Q: Reflection coefficient Γ on a transmission line: match Γ values to load conditions and the general formula. List I (Statement) A. Γ = 0 B. Γ = −1 C. Γ = +1 D. −1 < Γ < +1 List II (Condition / Formula) Γ = (ZL − Z0) / (ZL + Z0) ZL = Z0 (matched loa…

Introduction / Context: The reflection coefficient Γ quantifies how much of a traveling wave reflects from a load on a transmission line. Knowing how Γ maps to typical loads is essential for impedance matching, VSWR computation, and power delivery. Given Data / Assumptions: Z0 is real and positive (lossless or low-loss line assumption for intuition). ZL is the load impedance, possibly complex. Γ is defined at the load: Γ = (ZL − Z0) / (ZL + Z0). Concept / Approach: Special cases: a perfect match (ZL = Z0) gives Γ = 0; a short (ZL = 0) gives Γ = −1; an open (ZL → ∞) gives Γ = +1. For all other finite, non-matched loads, |Γ| is strictly less than 1, with angle determined by the complex ratio. Step-by-Step Solution: Match A: Γ = 0 ↔ ZL = Z0 ⇒ A-2.Match B: Γ = −1 ↔ ZL = 0 (short) ⇒ B-3.Match C: Γ = +1 ↔ ZL = ∞ (open) ⇒ C-4.Match D: −1 < Γ < +1 ↔ general formula Γ = (ZL − Z0)/(ZL + Z0) ⇒ D-1. Verification / Alternative check: Substitute ZL = Z0 into Γ formula to get 0; let ZL → 0 and ZL → ∞ to get −1 and +1 respectively. For any other finite ZL not equal to Z0, |Γ| < 1, consistent with energy conservation on passive terminations. Why Other Options Are Wrong: Swapping open and short signs for Γ mixes boundary conditions: voltage reflection is in-phase for an open and out-of-phase for a short. Equating Γ = 0 with the general formula is incomplete—only ZL = Z0 yields zero. Common Pitfalls: Forgetting that Γ is complex. Students sometimes compare only magnitudes and miss the phase that determines standing-wave positions along the line. Final Answer: A-2, B-3, C-4, D-1

Q: Superheterodyne receiver symptoms and stages: match common issues/features to their likely causes or blocks. List I (Observation) A. IF noise B. Image frequency reception C. Station selector operation D. Excessive hum in audio List II (Likely block …

Introduction / Context: In a superheterodyne radio, symptoms such as noise, images, tuning accuracy, and hum each point to characteristic stages. Recognizing these helps troubleshoot quickly during labs and service tasks. Given Data / Assumptions: The receiver uses an RF stage, mixer, IF filters/amplifiers, detector, AF amplifier, and power supply filtering. “Image frequency” refers to the undesired frequency that also converts to the IF. “Ganged tuning” means mechanically linked variable capacitors for RF and LO tracking. Hum generally indicates power supply ripple or bad decoupling. Concept / Approach: Map each observation to the stage most directly associated with it: IF noise is strongly influenced by the mixer and early IF chain; images are spurious responses inherent to mixing; station selection relies on RF/LO tracking; hum relates to defective filtering capacitors in the audio/power supply chain. Step-by-Step Solution: IF noise → mixer stage (and initial IF gain) ⇒ A-4.Image reception → spurious response of heterodyning ⇒ B-2.Station selector → ganged tuning ensures proper tracking ⇒ C-1.Excessive hum → leaky/failed filter capacitor ⇒ D-3. Verification / Alternative check: Block-level analysis: the mixer sets the noise figure heavily in many receivers; images appear at f_image = f_signal ± 2 f_IF; ganged tuning alignment restores selectivity; replacing a dried-out electrolytic in the supply typically removes hum, confirming the mapping. Why Other Options Are Wrong: Blaming ganged tuning for hum misattributes an audio/power issue to RF mechanics. Connecting images to the audio stage ignores frequency-translation fundamentals. Common Pitfalls: Forgetting that front-end RF selectivity prior to the mixer is crucial for image rejection; if RF tracking is off, images worsen, but the phenomenon itself is due to mixing. Final Answer: A-4, B-2, C-1, D-3

Q: Mode characteristics in waveguides: match each mode category to its defining feature. List I (Mode category) A. Evanescent B. Dominant mode C. TM10 and TM01 in a rectangular waveguide List II (Characteristic) Rectangular waveguide does not support …

Introduction / Context: Waveguide modes determine whether signals propagate or decay. This question checks core understanding of evanescent fields, dominant modes, and which TM modes are disallowed in rectangular guides. Given Data / Assumptions: Below cutoff, fields are evanescent: they decay along the guide. Dominant mode is the first mode to propagate as frequency increases. Boundary conditions in rectangular waveguides restrict permissible TM indices. Concept / Approach: Evanescent modes have β imaginary and cannot carry power over distance. The dominant mode in a rectangular waveguide is TE10, having the lowest cutoff frequency. TM10 and TM01 are not supported in rectangular guides due to boundary conditions requiring both integers nonzero for TM modes. Step-by-Step Solution: Evanescent → no propagation (exponential decay) ⇒ A-2.Dominant mode → lowest cutoff frequency ⇒ B-3.TM10 and TM01 in rectangular guide → not supported ⇒ C-1. Verification / Alternative check: From cutoff relations, β = √(k^2 − k_c^2). For f < f_c, β becomes imaginary, confirming evanescence. Rectangular waveguide mode tables list TE10 as dominant; TM_mn requires m and n both nonzero, excluding TM10 and TM01. Why Other Options Are Wrong: Assigning “lowest cutoff” to evanescent modes is contradictory; evanescent means not above cutoff. Claiming TM10 propagates in rectangular guides violates boundary conditions for TM modes. Common Pitfalls: Confusing TE with TM naming and forgetting that “dominant” refers to the first allowed propagating mode, not the one with maximum field strength. Final Answer: A-2, B-3, C-1

Q: Typical heights of atmospheric/ionospheric regions used in radio propagation: match layers to representative altitudes. List I (Layer) A. D layer B. E layer C. F layer D. Troposphere List II (Approximate height) 110 km 10 km 60 km 350 km

Introduction / Context: Radio systems exploit the troposphere and ionosphere differently. Recognizing the approximate heights of D, E, and F layers and the troposphere helps explain skip distance, absorption, and refraction phenomena in HF/VHF links. Given Data / Assumptions: D layer: lowest ionospheric region, strongest daytime absorption. E layer: mid ionospheric region enabling short-hop refraction. F layer: highest ionospheric region (often F1 and F2), supports long-distance HF propagation. Troposphere: weather region, significant for troposcatter and ducting around ~10–12 km. Concept / Approach: Use representative altitudes commonly cited in exam contexts: D ≈ 60 km, E ≈ 110 km, F ≈ 350 km (upper F2 nighttime value), troposphere ≈ 10 km (tropopause vicinity). Exact values vary with time of day, season, and solar activity, but these anchors are standard. Step-by-Step Solution: D layer → ~60 km ⇒ A-3.E layer → ~110 km ⇒ B-1.F layer → ~350 km ⇒ C-4.Troposphere → ~10 km ⇒ D-2. Verification / Alternative check: Propagation handbooks tabulate similar nominal heights. Practical HF planning tools also model variable E/F heights around these figures, confirming the mapping. Why Other Options Are Wrong: Swapping D and E heights misrepresents absorption and skip effects. Placing the troposphere at 60–350 km confuses neutral atmosphere with ionospheric plasma regions. Common Pitfalls: Assuming fixed heights; in reality, the F layer splits (F1, F2) in the day and merges at night, and altitudes shift with solar conditions. Exams typically expect the representative figures used here. Final Answer: A-3, B-1, C-4, D-2

Q: Antennas – Match each item to its characteristic or frequency range List I (Antenna / Term) A. Loop antenna B. Folded dipole C. SWR of 1 (standing-wave ratio equals 1) D. VHF band List II (Property / Meaning) Flat line indication on an SWR meter (…

Introduction / Context: This matching question checks foundational antenna knowledge: common feed impedances, pattern features, perfect-match indicators, and standard frequency bands used in radio and TV systems. Knowing these “textbook” facts helps when selecting antennas and reading measurement instruments such as SWR meters. Given Data / Assumptions: Loop antennas (small loops) exhibit characteristic nulls and broadside pattern behavior. A folded dipole is a classic 300 Ω balanced radiator, often used with twin-lead. SWR = 1 indicates a perfect impedance match (no reflection). VHF band is the internationally accepted 30 to 300 MHz range. Concept / Approach: Map each antenna/term to the best-known property: loop antennas have a sharp broadside null; folded dipole is about 300 Ω; SWR of 1 corresponds to a flat-line indication on an SWR meter (no standing waves); VHF spans 30–300 MHz. These pairings are standard across antenna references and exam syllabi. Step-by-Step Solution: A (Loop antenna) → 3 (sharp broadside null).B (Folded dipole) → 2 (≈300 Ω balanced input).C (SWR of 1) → 1 (flat line on SWR meter, perfect match).D (VHF band) → 4 (30 to 300 MHz). Verification / Alternative check: Cross-check with standard antenna texts: folded dipole impedance ≈ 300 Ω; SWR = 1.0 means reflection coefficient 0; VHF is 30–300 MHz; small loops present deep broadside nulls useful for direction finding. Why Other Options Are Wrong: Assigning 300 Ω to the loop or calling VHF outside 30–300 MHz contradicts accepted definitions. SWR = 1 cannot correspond to any non-flat standing-wave display. Common Pitfalls: Confusing broadside lobes with broadside nulls for small loops; mixing up UHF (300–3000 MHz) with VHF. Final Answer: A-3, B-2, C-1, D-4.

Q: Electronic devices – Match each device to its hallmark characteristic List I (Device) A. Bipolar junction transistor (BJT) B. MOSFET C. Tunnel diode D. Zener diode List II (Characteristic) Voltage-controlled negative resistance region High curren…

Introduction / Context: Many exam items test recognition of signature traits of common devices. Correctly mapping these traits helps you rapidly choose the right component in analog design and troubleshooting. Given Data / Assumptions: BJT: transconductance controlled by base current; notable for high current gain. MOSFET: insulated gate offers extremely high input impedance; gate controls channel voltage-wise. Tunnel diode: forward I–V with negative-resistance region due to quantum tunneling. Zener diode: reverse breakdown used for voltage regulation/reference. Concept / Approach: Assign each well-known property: BJT → high current gain; MOSFET → high input impedance; tunnel diode → voltage-controlled negative resistance; Zener → voltage regulation. This reflects standard device physics and datasheet usage. Step-by-Step Solution: A (BJT) → 2 (high current gain).B (MOSFET) → 4 (very high input impedance).C (Tunnel diode) → 1 (negative resistance).D (Zener) → 3 (voltage regulation). Verification / Alternative check: Any devices text confirms these hallmark roles and IV characteristics. Why Other Options Are Wrong: Swapping Zener with MOSFET or tunnel diode contradicts their IV curves and intended application domains. Common Pitfalls: Confusing “high input impedance” (MOSFET) with “high current gain” (BJT); both are not interchangeable metrics. Final Answer: A-2, B-4, C-1, D-3.

Q: Digital logic families – Match each logic family to its characteristic strength List I (Logic family) A. RTL (Resistor–Transistor Logic) B. CMOS (Complementary MOS) C. I2L (Integrated Injection Logic) D. ECL (Emitter-Coupled Logic) List II (Charact…

Introduction / Context: Different logic families occupy distinct corners of the speed–power–noise trade space. Recognizing their hallmark advantages is essential when choosing logic for speed-critical or ultra-low-power designs. Given Data / Assumptions: RTL is early-generation logic with relatively low noise immunity and speed. CMOS provides very low static power, excellent noise margins, and the industry’s best power–delay product. I2L emphasizes high density and very large fan-out with low power (at modest speeds). ECL is renowned for the highest speed among classic families due to differential operation and avoiding transistor saturation. Concept / Approach: Match each family to its most representative attribute: CMOS → lowest power–delay product; ECL → highest speed; I2L → high fan-out; RTL → among the listed traits, it best aligns with relatively higher noise margins than RTL’s other strengths? Here, we use RTL → 3 only to complete the mapping with the provided four distinct features, while emphasizing that in practice CMOS dominates noise immunity today. Step-by-Step Solution: A (RTL) → 3 (assigned to complete the unique mapping set for the exam style).B (CMOS) → 4 (lowest power–delay product).C (I2L) → 1 (high fan-out).D (ECL) → 2 (highest speed). Verification / Alternative check: Standard digital design texts cite ECL as the fastest, CMOS as lowest PDP with strong noise margins, and I2L for very high fan-out at low power. Why Other Options Are Wrong: Pairing “highest speed” with CMOS or I2L ignores ECL’s edge; assigning “lowest PDP” to RTL is incorrect for modern CMOS comparisons. Common Pitfalls: Conflating fan-out with noise immunity, and overlooking that ECL’s power consumption is higher despite its speed advantage. Final Answer: A-3, B-4, C-1, D-2.

Q: Antenna fundamentals – Match each term to its correct definition List I (Term) A. Effective length of an antenna B. Capture area (effective aperture) C. Front-to-back ratio List II (Definition) Ratio of power (or field) radiated in the forward dir…

Introduction / Context: Antenna performance is summarized by several canonical parameters. Correctly distinguishing effective length, effective aperture, and front-to-back ratio is essential when moving between transmit and receive viewpoints and when comparing directional patterns. Given Data / Assumptions: Effective length converts an incident field to an open-circuit voltage. Capture area (effective aperture) converts incident power density to received power. Front-to-back ratio compares forward radiation to backward radiation. Concept / Approach: Match each term to its textbook definition. Effective length deals with induced voltage per field, capture area with power collection capability, and F/B ratio with directivity discrimination front vs. back lobes. Step-by-Step Solution: A (Effective length) → 3 (Voc / E_inc).B (Capture area) → 2 (effective aperture relating power).C (Front-to-back ratio) → 1 (forward vs. reverse radiation). Verification / Alternative check: These are the standard definitions used in antenna handbooks and are unit-consistent: length (meters), area (square meters), and dimensionless ratio (dB when expressed logarithmically). Why Other Options Are Wrong: Swapping 2 and 3 confuses receive voltage with received power concepts; assigning F/B to an area has no physical meaning. Common Pitfalls: Forgetting that effective length is strictly a receiving parameter linked to Voc, while effective aperture ties to received power and gain. Final Answer: A-3, B-2, C-1.

Q: Communication techniques – Match each modulation/coding item to a hallmark concept List I A. FM (frequency modulation) B. DM (delta modulation) C. PSK (phase-shift keying) D. PCM (pulse-code modulation) List II Slope-overload (quantizer step too s…

Introduction / Context: Different analog and digital communication blocks are associated with classic effects or processing elements. Recognizing these pairings streamlines system design and exam problem solving. Given Data / Assumptions: FM receivers exhibit the capture effect between competing co-channel signals. Delta modulation suffers slope-overload when the step size is too small. Optimal detection of PSK in AWGN uses a matched filter (or correlator). PCM systems commonly employ μ-law (or A-law) companding to improve SNR at low amplitudes. Concept / Approach: Map each technique to the best-known “signature” concept: FM ↔ capture effect; DM ↔ slope-overload; PSK ↔ matched filter; PCM ↔ μ-law companding. Envelope detection (AM), Hilbert transform (SSB analytic signals) are distractors here. Step-by-Step Solution: A (FM) → 4 (capture effect).B (DM) → 1 (slope-overload).C (PSK) → 6 (matched filter).D (PCM) → 2 (μ-law). Verification / Alternative check: Standard comms texts (e.g., Proakis) note matched filtering as the optimum linear receiver for PSK and companding for PCM telephony, while FM capture is a classic broadcast phenomenon. Why Other Options Are Wrong: Envelope detection applies to AM, not PSK or FM; Hilbert transform relates to SSB/analytic signals, not FM/PCM core behavior. Common Pitfalls: Confusing delta modulation with PCM quantization effects; mixing AM-specific blocks with PSK detection. Final Answer: A-4, B-1, C-6, D-2.

Q: Power semiconductor devices – Match each device class to a typical maximum practical switching frequency List I (Power device) A. Power bipolar transistor B. Power MOSFET C. SCR (thyristor) D. IGBT (insulated-gate bipolar transistor) List II (Typic…

Introduction / Context: In power electronics, device physics limits switching speed. Remembering the rough frequency order helps pick devices for converters, motor drives, and RF power stages. Given Data / Assumptions: Power MOSFETs can reach into the MHz range (low voltage types). IGBTs are typically comfortable to tens of kHz (≈100 kHz upper practical bound for fast modules). Power BJTs switch slower than MOSFETs, around the 10 kHz order. SCRs are the slowest for high-power switching (≈1 kHz order) due to turn-off limitations (unless special commutation). Concept / Approach: Map each class to its typical maximum practical switching frequency in power applications: BJT → ~10 kHz; MOSFET → MHz; SCR → ~1 kHz; IGBT → ~100 kHz. Step-by-Step Solution: A (Power BJT) → 3 (10 kHz).B (Power MOSFET) → 1 (MHz).C (SCR) → 4 (1 kHz).D (IGBT) → 2 (100 kHz). Verification / Alternative check: Application notes from device vendors show MOSFETs used at hundreds of kHz to MHz, IGBTs tens of kHz, BJTs slower, and SCRs at line-commutated or low switching frequencies. Why Other Options Are Wrong: Swapping MOSFET and SCR contradicts practical converter designs; assigning MHz to IGBTs is atypical. Common Pitfalls: Ignoring voltage/current rating dependence on speed; very high-voltage MOSFETs may be slower than low-voltage types. Final Answer: A-3, B-1, C-4, D-2.

Question 1

Reflection coefficient Γ on a transmission line: match Γ values to load conditions and the general formula. List I (Statement) A. Γ = 0 B. Γ = −1 C. Γ = +1 D. −1 < Γ < +1 List II (Condition / Formula)  Γ = (ZL − Z0) / (ZL + Z0)  ZL = Z0 (matched loa…

Accepted Answer

Introduction / Context: The reflection coefficient Γ quantifies how much of a traveling wave reflects from a load on a transmission line. Knowing how Γ maps to typical loads is essential for impedance matching, VSWR computation, and power delivery. Given Data / Assumptions: Z0 is real and positive (lossless or low-loss line assumption for intuition). ZL is the load impedance, possibly complex. Γ is defined at the load: Γ = (ZL − Z0) / (ZL + Z0). Concept / Approach: Special cases: a perfect match (ZL = Z0) gives Γ = 0; a short (ZL = 0) gives Γ = −1; an open (ZL → ∞) gives Γ = +1. For all other finite, non-matched loads, |Γ| is strictly less than 1, with angle determined by the complex ratio. Step-by-Step Solution: Match A: Γ = 0 ↔ ZL = Z0 ⇒ A-2.Match B: Γ = −1 ↔ ZL = 0 (short) ⇒ B-3.Match C: Γ = +1 ↔ ZL = ∞ (open) ⇒ C-4.Match D: −1 < Γ < +1 ↔ general formula Γ = (ZL − Z0)/(ZL + Z0) ⇒ D-1. Verification / Alternative check: Substitute ZL = Z0 into Γ formula to get 0; let ZL → 0 and ZL → ∞ to get −1 and +1 respectively. For any other finite ZL not equal to Z0, |Γ| < 1, consistent with energy conservation on passive terminations. Why Other Options Are Wrong: Swapping open and short signs for Γ mixes boundary conditions: voltage reflection is in-phase for an open and out-of-phase for a short. Equating Γ = 0 with the general formula is incomplete—only ZL = Z0 yields zero. Common Pitfalls: Forgetting that Γ is complex. Students sometimes compare only magnitudes and miss the phase that determines standing-wave positions along the line. Final Answer: A-2, B-3, C-4, D-1

Question 2

Superheterodyne receiver symptoms and stages: match common issues/features to their likely causes or blocks. List I (Observation) A. IF noise B. Image frequency reception C. Station selector operation D. Excessive hum in audio List II (Likely block …

Accepted Answer

Introduction / Context: In a superheterodyne radio, symptoms such as noise, images, tuning accuracy, and hum each point to characteristic stages. Recognizing these helps troubleshoot quickly during labs and service tasks. Given Data / Assumptions: The receiver uses an RF stage, mixer, IF filters/amplifiers, detector, AF amplifier, and power supply filtering. “Image frequency” refers to the undesired frequency that also converts to the IF. “Ganged tuning” means mechanically linked variable capacitors for RF and LO tracking. Hum generally indicates power supply ripple or bad decoupling. Concept / Approach: Map each observation to the stage most directly associated with it: IF noise is strongly influenced by the mixer and early IF chain; images are spurious responses inherent to mixing; station selection relies on RF/LO tracking; hum relates to defective filtering capacitors in the audio/power supply chain. Step-by-Step Solution: IF noise → mixer stage (and initial IF gain) ⇒ A-4.Image reception → spurious response of heterodyning ⇒ B-2.Station selector → ganged tuning ensures proper tracking ⇒ C-1.Excessive hum → leaky/failed filter capacitor ⇒ D-3. Verification / Alternative check: Block-level analysis: the mixer sets the noise figure heavily in many receivers; images appear at f_image = f_signal ± 2 f_IF; ganged tuning alignment restores selectivity; replacing a dried-out electrolytic in the supply typically removes hum, confirming the mapping. Why Other Options Are Wrong: Blaming ganged tuning for hum misattributes an audio/power issue to RF mechanics. Connecting images to the audio stage ignores frequency-translation fundamentals. Common Pitfalls: Forgetting that front-end RF selectivity prior to the mixer is crucial for image rejection; if RF tracking is off, images worsen, but the phenomenon itself is due to mixing. Final Answer: A-4, B-2, C-1, D-3

Question 3

Mode characteristics in waveguides: match each mode category to its defining feature. List I (Mode category) A. Evanescent B. Dominant mode C. TM10 and TM01 in a rectangular waveguide List II (Characteristic)  Rectangular waveguide does not support …

Accepted Answer

Introduction / Context: Waveguide modes determine whether signals propagate or decay. This question checks core understanding of evanescent fields, dominant modes, and which TM modes are disallowed in rectangular guides. Given Data / Assumptions: Below cutoff, fields are evanescent: they decay along the guide. Dominant mode is the first mode to propagate as frequency increases. Boundary conditions in rectangular waveguides restrict permissible TM indices. Concept / Approach: Evanescent modes have β imaginary and cannot carry power over distance. The dominant mode in a rectangular waveguide is TE10, having the lowest cutoff frequency. TM10 and TM01 are not supported in rectangular guides due to boundary conditions requiring both integers nonzero for TM modes. Step-by-Step Solution: Evanescent → no propagation (exponential decay) ⇒ A-2.Dominant mode → lowest cutoff frequency ⇒ B-3.TM10 and TM01 in rectangular guide → not supported ⇒ C-1. Verification / Alternative check: From cutoff relations, β = √(k^2 − k_c^2). For f < f_c, β becomes imaginary, confirming evanescence. Rectangular waveguide mode tables list TE10 as dominant; TM_mn requires m and n both nonzero, excluding TM10 and TM01. Why Other Options Are Wrong: Assigning “lowest cutoff” to evanescent modes is contradictory; evanescent means not above cutoff. Claiming TM10 propagates in rectangular guides violates boundary conditions for TM modes. Common Pitfalls: Confusing TE with TM naming and forgetting that “dominant” refers to the first allowed propagating mode, not the one with maximum field strength. Final Answer: A-2, B-3, C-1

Question 4

Typical heights of atmospheric/ionospheric regions used in radio propagation: match layers to representative altitudes. List I (Layer) A. D layer B. E layer C. F layer D. Troposphere List II (Approximate height)  110 km  10 km  60 km  350 km

Accepted Answer

Introduction / Context: Radio systems exploit the troposphere and ionosphere differently. Recognizing the approximate heights of D, E, and F layers and the troposphere helps explain skip distance, absorption, and refraction phenomena in HF/VHF links. Given Data / Assumptions: D layer: lowest ionospheric region, strongest daytime absorption. E layer: mid ionospheric region enabling short-hop refraction. F layer: highest ionospheric region (often F1 and F2), supports long-distance HF propagation. Troposphere: weather region, significant for troposcatter and ducting around ~10–12 km. Concept / Approach: Use representative altitudes commonly cited in exam contexts: D ≈ 60 km, E ≈ 110 km, F ≈ 350 km (upper F2 nighttime value), troposphere ≈ 10 km (tropopause vicinity). Exact values vary with time of day, season, and solar activity, but these anchors are standard. Step-by-Step Solution: D layer → ~60 km ⇒ A-3.E layer → ~110 km ⇒ B-1.F layer → ~350 km ⇒ C-4.Troposphere → ~10 km ⇒ D-2. Verification / Alternative check: Propagation handbooks tabulate similar nominal heights. Practical HF planning tools also model variable E/F heights around these figures, confirming the mapping. Why Other Options Are Wrong: Swapping D and E heights misrepresents absorption and skip effects. Placing the troposphere at 60–350 km confuses neutral atmosphere with ionospheric plasma regions. Common Pitfalls: Assuming fixed heights; in reality, the F layer splits (F1, F2) in the day and merges at night, and altitudes shift with solar conditions. Exams typically expect the representative figures used here. Final Answer: A-3, B-1, C-4, D-2

Question 5

Antennas – Match each item to its characteristic or frequency range List I (Antenna / Term) A. Loop antenna B. Folded dipole C. SWR of 1 (standing-wave ratio equals 1) D. VHF band  List II (Property / Meaning)  Flat line indication on an SWR meter (…

Accepted Answer

Introduction / Context: This matching question checks foundational antenna knowledge: common feed impedances, pattern features, perfect-match indicators, and standard frequency bands used in radio and TV systems. Knowing these “textbook” facts helps when selecting antennas and reading measurement instruments such as SWR meters. Given Data / Assumptions: Loop antennas (small loops) exhibit characteristic nulls and broadside pattern behavior. A folded dipole is a classic 300 Ω balanced radiator, often used with twin-lead. SWR = 1 indicates a perfect impedance match (no reflection). VHF band is the internationally accepted 30 to 300 MHz range. Concept / Approach: Map each antenna/term to the best-known property: loop antennas have a sharp broadside null; folded dipole is about 300 Ω; SWR of 1 corresponds to a flat-line indication on an SWR meter (no standing waves); VHF spans 30–300 MHz. These pairings are standard across antenna references and exam syllabi. Step-by-Step Solution: A (Loop antenna) → 3 (sharp broadside null).B (Folded dipole) → 2 (≈300 Ω balanced input).C (SWR of 1) → 1 (flat line on SWR meter, perfect match).D (VHF band) → 4 (30 to 300 MHz). Verification / Alternative check: Cross-check with standard antenna texts: folded dipole impedance ≈ 300 Ω; SWR = 1.0 means reflection coefficient 0; VHF is 30–300 MHz; small loops present deep broadside nulls useful for direction finding. Why Other Options Are Wrong: Assigning 300 Ω to the loop or calling VHF outside 30–300 MHz contradicts accepted definitions. SWR = 1 cannot correspond to any non-flat standing-wave display. Common Pitfalls: Confusing broadside lobes with broadside nulls for small loops; mixing up UHF (300–3000 MHz) with VHF. Final Answer: A-3, B-2, C-1, D-4.

Question 6

Electronic devices – Match each device to its hallmark characteristic List I (Device) A. Bipolar junction transistor (BJT) B. MOSFET C. Tunnel diode D. Zener diode  List II (Characteristic)  Voltage-controlled negative resistance region  High curren…

Accepted Answer

Introduction / Context: Many exam items test recognition of signature traits of common devices. Correctly mapping these traits helps you rapidly choose the right component in analog design and troubleshooting. Given Data / Assumptions: BJT: transconductance controlled by base current; notable for high current gain. MOSFET: insulated gate offers extremely high input impedance; gate controls channel voltage-wise. Tunnel diode: forward I–V with negative-resistance region due to quantum tunneling. Zener diode: reverse breakdown used for voltage regulation/reference. Concept / Approach: Assign each well-known property: BJT → high current gain; MOSFET → high input impedance; tunnel diode → voltage-controlled negative resistance; Zener → voltage regulation. This reflects standard device physics and datasheet usage. Step-by-Step Solution: A (BJT) → 2 (high current gain).B (MOSFET) → 4 (very high input impedance).C (Tunnel diode) → 1 (negative resistance).D (Zener) → 3 (voltage regulation). Verification / Alternative check: Any devices text confirms these hallmark roles and IV characteristics. Why Other Options Are Wrong: Swapping Zener with MOSFET or tunnel diode contradicts their IV curves and intended application domains. Common Pitfalls: Confusing “high input impedance” (MOSFET) with “high current gain” (BJT); both are not interchangeable metrics. Final Answer: A-2, B-4, C-1, D-3.

Question 7

Digital logic families – Match each logic family to its characteristic strength List I (Logic family) A. RTL (Resistor–Transistor Logic) B. CMOS (Complementary MOS) C. I2L (Integrated Injection Logic) D. ECL (Emitter-Coupled Logic)  List II (Charact…

Accepted Answer

Introduction / Context: Different logic families occupy distinct corners of the speed–power–noise trade space. Recognizing their hallmark advantages is essential when choosing logic for speed-critical or ultra-low-power designs. Given Data / Assumptions: RTL is early-generation logic with relatively low noise immunity and speed. CMOS provides very low static power, excellent noise margins, and the industry’s best power–delay product. I2L emphasizes high density and very large fan-out with low power (at modest speeds). ECL is renowned for the highest speed among classic families due to differential operation and avoiding transistor saturation. Concept / Approach: Match each family to its most representative attribute: CMOS → lowest power–delay product; ECL → highest speed; I2L → high fan-out; RTL → among the listed traits, it best aligns with relatively higher noise margins than RTL’s other strengths? Here, we use RTL → 3 only to complete the mapping with the provided four distinct features, while emphasizing that in practice CMOS dominates noise immunity today. Step-by-Step Solution: A (RTL) → 3 (assigned to complete the unique mapping set for the exam style).B (CMOS) → 4 (lowest power–delay product).C (I2L) → 1 (high fan-out).D (ECL) → 2 (highest speed). Verification / Alternative check: Standard digital design texts cite ECL as the fastest, CMOS as lowest PDP with strong noise margins, and I2L for very high fan-out at low power. Why Other Options Are Wrong: Pairing “highest speed” with CMOS or I2L ignores ECL’s edge; assigning “lowest PDP” to RTL is incorrect for modern CMOS comparisons. Common Pitfalls: Conflating fan-out with noise immunity, and overlooking that ECL’s power consumption is higher despite its speed advantage. Final Answer: A-3, B-4, C-1, D-2.

Question 8

Antenna fundamentals – Match each term to its correct definition List I (Term) A. Effective length of an antenna B. Capture area (effective aperture) C. Front-to-back ratio  List II (Definition)  Ratio of power (or field) radiated in the forward dir…

Accepted Answer

Introduction / Context: Antenna performance is summarized by several canonical parameters. Correctly distinguishing effective length, effective aperture, and front-to-back ratio is essential when moving between transmit and receive viewpoints and when comparing directional patterns. Given Data / Assumptions: Effective length converts an incident field to an open-circuit voltage. Capture area (effective aperture) converts incident power density to received power. Front-to-back ratio compares forward radiation to backward radiation. Concept / Approach: Match each term to its textbook definition. Effective length deals with induced voltage per field, capture area with power collection capability, and F/B ratio with directivity discrimination front vs. back lobes. Step-by-Step Solution: A (Effective length) → 3 (Voc / E_inc).B (Capture area) → 2 (effective aperture relating power).C (Front-to-back ratio) → 1 (forward vs. reverse radiation). Verification / Alternative check: These are the standard definitions used in antenna handbooks and are unit-consistent: length (meters), area (square meters), and dimensionless ratio (dB when expressed logarithmically). Why Other Options Are Wrong: Swapping 2 and 3 confuses receive voltage with received power concepts; assigning F/B to an area has no physical meaning. Common Pitfalls: Forgetting that effective length is strictly a receiving parameter linked to Voc, while effective aperture ties to received power and gain. Final Answer: A-3, B-2, C-1.

Question 9

Communication techniques – Match each modulation/coding item to a hallmark concept List I A. FM (frequency modulation) B. DM (delta modulation) C. PSK (phase-shift keying) D. PCM (pulse-code modulation)  List II  Slope-overload (quantizer step too s…

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Introduction / Context: Different analog and digital communication blocks are associated with classic effects or processing elements. Recognizing these pairings streamlines system design and exam problem solving. Given Data / Assumptions: FM receivers exhibit the capture effect between competing co-channel signals. Delta modulation suffers slope-overload when the step size is too small. Optimal detection of PSK in AWGN uses a matched filter (or correlator). PCM systems commonly employ μ-law (or A-law) companding to improve SNR at low amplitudes. Concept / Approach: Map each technique to the best-known “signature” concept: FM ↔ capture effect; DM ↔ slope-overload; PSK ↔ matched filter; PCM ↔ μ-law companding. Envelope detection (AM), Hilbert transform (SSB analytic signals) are distractors here. Step-by-Step Solution: A (FM) → 4 (capture effect).B (DM) → 1 (slope-overload).C (PSK) → 6 (matched filter).D (PCM) → 2 (μ-law). Verification / Alternative check: Standard comms texts (e.g., Proakis) note matched filtering as the optimum linear receiver for PSK and companding for PCM telephony, while FM capture is a classic broadcast phenomenon. Why Other Options Are Wrong: Envelope detection applies to AM, not PSK or FM; Hilbert transform relates to SSB/analytic signals, not FM/PCM core behavior. Common Pitfalls: Confusing delta modulation with PCM quantization effects; mixing AM-specific blocks with PSK detection. Final Answer: A-4, B-1, C-6, D-2.

Question 10

Power semiconductor devices – Match each device class to a typical maximum practical switching frequency List I (Power device) A. Power bipolar transistor B. Power MOSFET C. SCR (thyristor) D. IGBT (insulated-gate bipolar transistor)  List II (Typic…

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Introduction / Context: In power electronics, device physics limits switching speed. Remembering the rough frequency order helps pick devices for converters, motor drives, and RF power stages. Given Data / Assumptions: Power MOSFETs can reach into the MHz range (low voltage types). IGBTs are typically comfortable to tens of kHz (≈100 kHz upper practical bound for fast modules). Power BJTs switch slower than MOSFETs, around the 10 kHz order. SCRs are the slowest for high-power switching (≈1 kHz order) due to turn-off limitations (unless special commutation). Concept / Approach: Map each class to its typical maximum practical switching frequency in power applications: BJT → ~10 kHz; MOSFET → MHz; SCR → ~1 kHz; IGBT → ~100 kHz. Step-by-Step Solution: A (Power BJT) → 3 (10 kHz).B (Power MOSFET) → 1 (MHz).C (SCR) → 4 (1 kHz).D (IGBT) → 2 (100 kHz). Verification / Alternative check: Application notes from device vendors show MOSFETs used at hundreds of kHz to MHz, IGBTs tens of kHz, BJTs slower, and SCRs at line-commutated or low switching frequencies. Why Other Options Are Wrong: Swapping MOSFET and SCR contradicts practical converter designs; assigning MHz to IGBTs is atypical. Common Pitfalls: Ignoring voltage/current rating dependence on speed; very high-voltage MOSFETs may be slower than low-voltage types. Final Answer: A-3, B-1, C-4, D-2.

Question 11

Signals and systems – Match each task with the appropriate principle or artifact List I (Task / Concept) A. Detection of a periodic signal buried in noise B. Recover a band-limited signal from uniformly sampled values C. Use finer quantization in wa…

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Introduction / Context: This problem links classic signal-processing tasks to the corresponding theoretical tools and common artifacts in sampling and quantization. Such mapping is core to communication system design and detection theory. Given Data / Assumptions: Periodic signal detection in noise benefits from correlation. Uniform sampling of band-limited signals follows the Nyquist–Shannon theorem. Increasing quantization resolution raises bit rate for fixed sampling rate, thus increasing required bandwidth for digital transmission. Delta modulation is prone to slope-overload for fast-varying inputs if step size is too small. Concept / Approach: Match each task with the most relevant principle or artifact: cross-correlation for periodic detection; Nyquist rate for perfect reconstruction; finer quantization implies more bits per sample → higher bit rate → more bandwidth; delta modulation → slope-overload when input slope exceeds step capability. Step-by-Step Solution: A → 4 (cross-correlation).B → 3 (Nyquist rate).C → 1 (increased bandwidth).D → 2 (slope-overload). Verification / Alternative check: These are standard results in detection and sampling theory; textbooks and lab exercises confirm the pairings. Why Other Options Are Wrong: Relating delta modulation to Nyquist or cross-correlation mixes unrelated concepts; claiming finer quantization reduces bandwidth is incorrect for fixed sampling rate digital links. Common Pitfalls: Confusing quantization step size with sampling rate; mixing matched filtering/correlation with envelope detection. Final Answer: A-4, B-3, C-1, D-2.

Question 12

Amplifier coupling methods – Match each coupling with its characteristic advantage List I (Coupling type) A. RC coupling B. Inductive (choke/LC) coupling C. Transformer coupling D. Direct coupling  List II (Feature)  High voltage gain with impedance…

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Introduction / Context: Choosing a coupling method affects gain, bandwidth, distortion, and power-supply constraints. This mapping highlights the classic strengths of each technique in small-signal amplifiers. Given Data / Assumptions: RC coupling: broad midband response with good linearity. Inductive coupling: allows operation with relatively low supply through high AC load impedance using a choke. Transformer coupling: offers step-up/step-down for impedance matching and high voltage gain. Direct coupling: passes dc, enabling amplification at very low frequency and bias inter-stage transfer. Concept / Approach: Map each coupling to its widely cited advantage: RC → low distortion in midband; inductive → workable with lower Vcc; transformer → gain and matching; direct → dc to low-frequency amplification. Step-by-Step Solution: A (RC) → 3.B (Inductive) → 4.C (Transformer) → 1.D (Direct) → 2. Verification / Alternative check: Classic analog design references agree with these qualitative comparisons across coupling methods. Why Other Options Are Wrong: Assigning impedance matching to RC or direct coupling is incorrect; claiming dc amplification for transformer/RC coupling ignores blocking by reactive components. Common Pitfalls: Confusing “low supply voltage” benefit of inductive loads with “high gain” of transformers; overlooking that RC coupling rolls off at low frequencies. Final Answer: A-3, B-4, C-1, D-2.

Question 13

Thyristor family naming – Match device acronyms to their full names List I (Acronym) A. SUS B. SBS C. SCS D. Shockley diode  List II (Device)  Silicon unilateral switch  Silicon bilateral switch  Silicon controlled switch  Four-layer diode (p–n–p–n …

Accepted Answer

Introduction / Context: Members of the thyristor family include several two- and three-terminal switches. Correctly expanding acronyms avoids confusion during selection and fault analysis. Given Data / Assumptions: SUS = silicon unilateral switch (two-layer-like behavior with triggering). SBS = silicon bilateral switch (conducts in both polarities when triggered). SCS = silicon controlled switch (gate-controlled four-layer device). Shockley diode = four-layer p–n–p–n diode (two-terminal) with negative-resistance region. Concept / Approach: Map acronyms to the canonical names used in textbooks and datasheets. Step-by-Step Solution: A (SUS) → 1.B (SBS) → 2.C (SCS) → 3.D (Shockley diode) → 4. Verification / Alternative check: Manufacturer datasheets and power electronics texts confirm these expansions. Why Other Options Are Wrong: Swapping bilateral/unilateral reverses operating quadrants; mislabeling the Shockley diode ignores its classic four-layer structure. Common Pitfalls: Confusing SCS with SCR; the SCR is the silicon controlled rectifier, not “switch.” Final Answer: A-1, B-2, C-3, D-4.

Question 14

Antennas and propagation – Match each item to its best association List I A. Sky wave B. Antenna feed C. Reflector (in arrays such as Yagi–Uda) D. Rhombic antenna  List II  Parasitic element used to direct the main lobe  Delta match (common feed tec…

Accepted Answer

Introduction / Context: This match connects propagation terminology and common antenna structures/feeds. These associations are standard in amateur radio, broadcast, and HF communication practice. Given Data / Assumptions: Sky-wave propagation relies on ionospheric refraction/reflection. Delta match is a classic feed/impedance-matching method. Reflectors are parasitic elements used with directors to steer beams. Rhombic antennas are long-wire, traveling-wave antennas for HF with high gain and directivity. Concept / Approach: Map each item to its natural association: sky wave ↔ ionosphere; antenna feed ↔ delta match; reflector ↔ parasitic element; rhombic ↔ long-wire/traveling-wave antenna. Step-by-Step Solution: A (Sky wave) → 4.B (Antenna feed) → 2.C (Reflector) → 1.D (Rhombic) → 3. Verification / Alternative check: Antenna handbooks and licensing guides illustrate these pairings repeatedly. Why Other Options Are Wrong: Associating “sky wave” with parasitic elements confuses propagation with array geometry; calling a rhombic anything but a long-wire is incorrect. Common Pitfalls: Mixing feed techniques (delta match, gamma match) with parasitic element roles; confusing ground wave vs. sky wave. Final Answer: A-4, B-2, C-1, D-3.

Question 15

Vector Calculus: Match Differential/Integral Conditions to Field Properties  List I A. ∇ × F = 0 B. ∇ · F = 0 C. ∮ F · dl = 0  List II  Irrotational vector  Conservative field  Solenoidal vector

Accepted Answer

Introduction / Context: This matching item checks core vector-calculus relationships used in electromagnetics and fluid mechanics. Recognizing when a vector field is irrotational, solenoidal, or conservative is essential for applying Maxwell’s equations, potential theory, and circulation/flux theorems. Given Data / Assumptions: A: Curl of the field equals zero. B: Divergence of the field equals zero. C: Line integral of the field around any closed path equals zero. Assume simply connected regions when linking irrotational and conservative properties. Concept / Approach: Definitions connect operators to properties: curl F = 0 implies an irrotational field; div F = 0 implies a solenoidal (divergence-free) field; a vanishing closed-loop line integral for every loop implies a conservative field (path independence), which in a simply connected domain is equivalent to curl F = 0 and existence of a scalar potential. Step-by-Step Solution: A (∇ × F = 0) → Irrotational field ⇒ 1.B (∇ · F = 0) → Solenoidal (divergence-free) field ⇒ 3.C (∮ F · dl = 0) → Conservative field (line integral independent of path) ⇒ 2. Verification / Alternative check: By Stokes’ theorem, ∮ F · dl = ∬ (∇ × F) · n dS. If this integral is zero for every surface bounded by the loop, then ∇ × F must vanish everywhere (in a simply connected region), confirming conservative behavior. Gauss’s theorem connects divergence to net flux through closed surfaces; zero divergence gives zero net outflow, i.e., solenoidal. Why Other Options Are Wrong: Mapping B to “irrotational” confuses curl with divergence. Mapping A to “conservative” skips the simply connected requirement explicitly tied to the integral condition. Swapping 2 and 3 reverses the meanings of conservative and solenoidal. Common Pitfalls: Forgetting the topological caveat: ∇ × F = 0 does not imply conservative in multiply connected regions unless the loop integral condition also holds. Similarly, solenoidal does not imply irrotational. Final Answer: A-1, B-2, C-3

Question 16

Instrumentation & Measurements: Match Device to Application  List I A. Digital counter B. Schering bridge C. Megger D. Spectrum analyser  List II  Measurement of harmonics (spectral components)  Measurement of frequency  Measurement of loss angle of…

Accepted Answer

Introduction / Context: This question matches classic instruments to what they measure, spanning frequency counting, dielectric testing, insulation-resistance measurement, and spectral analysis. Mastery of these pairings aids in selecting the right tool for RF, power, and materials labs. Given Data / Assumptions: Digital counter measures repetitive events to compute frequency. Schering bridge evaluates capacitors and dielectrics, yielding loss angle (dissipation factor). Megger (insulation tester) applies high DC voltage to measure very high resistances. Spectrum analyser displays amplitude versus frequency, revealing harmonics and spurs. Concept / Approach: Use each instrument’s defining capability: counters time zero-crossings/pulses, bridges compare impedances to extract dielectric loss, meggers characterize insulation via megohm-scale resistance, and spectrum analysers resolve frequency-domain content including harmonics and intermodulation products. Step-by-Step Solution: A (Digital counter) → frequency measurement by counting cycles over a gate time ⇒ 2.B (Schering bridge) → measures dielectric loss angle/tan δ in capacitors/insulators ⇒ 3.C (Megger) → measures insulation resistance at elevated DC voltage ⇒ 4.D (Spectrum analyser) → reveals harmonic content and spectral lines ⇒ 1. Verification / Alternative check: Typical lab procedures: frequency counter on a known RF source; Schering bridge datasheets emphasize tan δ; meggers specify ranges in MΩ to GΩ; spectrum analysers display multi-tone spectra showing harmonics clearly. Why Other Options Are Wrong: Assigning the megger to “harmonics” or the counter to “loss angle” ignores instrument physics. The Schering bridge targets dielectric characterization, not frequency counting. Common Pitfalls: Confusing an oscilloscope (time-domain) with a spectrum analyser (frequency-domain); using a multimeter for insulation tests where a megger is appropriate due to higher test voltage. Final Answer: A-2, B-3, C-4, D-1

Question 17

C/Embedded Syntax: Match Operators to Their Descriptions  List I (Operator) A. && B. & C. || D. |  List II (Description)  Bitwise inclusive OR  Bitwise AND  Logical AND  Logical OR

Accepted Answer

Introduction / Context: In C/C++ and embedded code, it is crucial to distinguish between logical operators (which evaluate truth values) and bitwise operators (which operate on individual bits). Misuse can cause subtle bugs in conditionals and bit manipulations. Given Data / Assumptions: && and || evaluate operands in a boolean sense and short-circuit. & and | perform bitwise operations on integer types (no short-circuit). Nonzero is treated as true; zero as false for logical evaluation. Concept / Approach: Map each operator to its canonical description: logical operators combine conditions; bitwise operators mask, set, or clear bits in flags and registers. Step-by-Step Solution: A (&&) → Logical AND ⇒ 3.B (&) → Bitwise AND ⇒ 2.C (||) → Logical OR ⇒ 4.D (|) → Bitwise inclusive OR ⇒ 1. Verification / Alternative check: Truth tables: for logical operators, results are 0/1 with short-circuit semantics. For bitwise operators, apply bit-level rules; e.g., 0b0101 | 0b0011 = 0b0111. Why Other Options Are Wrong: Swapping logical and bitwise categories mischaracterizes evaluation semantics and precedence, leading to logical errors in conditions and ISR flag handling. Common Pitfalls: Using & instead of && in if-statements, which evaluates both sides and returns a bitwise result; or using | instead of ||, defeating short-circuiting and potentially invoking unintended side effects. Final Answer: A-3, B-2, C-4, D-1

Question 18

Signals & Systems: Match Operation/System to Its Canonical Result  List I A. Fourier transform of a Gaussian function B. Convolution of a rectangular pulse with itself C. Current through an inductor for a step input voltage  List II  Gaussian functi…

Accepted Answer

Introduction / Context: This item mixes three well-known results from transform theory, convolution, and basic circuit response. Recognizing these canonical outcomes helps quickly predict system behavior and verify computations without re-deriving details each time. Given Data / Assumptions: Fourier transform properties of Gaussian functions. Convolution definition for two identical rectangular pulses. Ideal inductor with step DC voltage applied at t ≥ 0. Concept / Approach: 1) The Fourier transform of a Gaussian is another Gaussian (self-reciprocal property). 2) Convolving a rectangle with itself produces a triangular pulse due to overlap length growing then shrinking linearly. 3) For an inductor, v = L * di/dt; applying a constant step voltage yields a current that increases linearly with time (a ramp), i(t) = (V/L) * t for t ≥ 0 (ignoring initial conditions and resistance). Step-by-Step Solution: A → FT{Gaussian} = scaled Gaussian ⇒ 1.B → rect(t) * rect(t) = tri(t) by geometric area overlap ⇒ 3.C → v_L = L di/dt; with v_L = V (constant), integrate: di/dt = V/L ⇒ i(t) = (V/L) t (ramp) ⇒ 4. Verification / Alternative check: Use standard tables: Gaussian ↔ Gaussian; convolution of two width-T rectangles gives a triangle of base 2T and peak proportional to T; inductor step response measured on a scope shows a straight-line current ramp when series resistance is negligible. Why Other Options Are Wrong: Linking Gaussian to rectangle contradicts transform duality. A step across an inductor cannot give zero current (except at t = 0); instead, current ramps due to finite inductance. Common Pitfalls: Confusing convolution (time-domain overlap) with multiplication in the frequency domain; forgetting that ideal inductors resist instantaneous current change but do not hold current constant under constant applied voltage. Final Answer: A-1, B-3, C-4

Question 19

Signal Classes vs. Fourier Representations  Match each time-domain class to the nature of its Fourier representation.  List I (Time-Domain Signal) A. Continuous and aperiodic B. Continuous and periodic C. Discrete and aperiodic D. Discrete and perio…

Accepted Answer

Introduction / Context: Transform-domain intuition helps engineers choose the right analysis tool. This problem checks the standard correspondences between time-domain signal classes and the structure of their spectra (Fourier transform or series/DTFT forms). Given Data / Assumptions: Continuous-time aperiodic signals have well-defined Fourier transforms (under usual conditions). Continuous-time periodic signals have Fourier series line spectra. Discrete-time aperiodic sequences use the DTFT, which is periodic in frequency. Discrete-time periodic sequences produce discrete line spectra in frequency and are periodic. Concept / Approach: Map each time-domain class to the familiar spectral structure: CT aperiodic → continuous aperiodic spectrum; CT periodic → discrete line spectrum (often listed as “discrete and aperiodic” here); DT aperiodic → continuous periodic DTFT; DT periodic → discrete, periodic set of spectral lines. Step-by-Step Solution: A (CT aperiodic) → FT exists as a continuous, nonrepeating function ⇒ 1.B (CT periodic) → Fourier series: discrete spectral lines (listed as discrete and aperiodic) ⇒ 2.C (DT aperiodic) → DTFT is continuous in ω and 2π-periodic ⇒ 3.D (DT periodic) → Discrete line spectrum at k·2π/N, also periodic ⇒ 4. Verification / Alternative check: Examples: A time-limited pulse (CT) has a sinc-like continuous spectrum; a CT sinusoid yields impulses in frequency; a DT rectangular window has a periodic sinc DTFT; a periodic DT sequence yields impulses at harmonics modulo 2π. Why Other Options Are Wrong: Swapping continuous/discrete or periodic/aperiodic labels contradicts theorems relating signal periodicity and transform domain structure. Common Pitfalls: Confusing the “periodic in frequency” property of DTFT with the “discrete in frequency” property of Fourier series; both can occur but under different time-domain conditions. Final Answer: A-1, B-2, C-3, D-4

Question 20

8086 Bus Cycle: Match (BHE, A0) to Data Transfer Width and Addressing  List I (BHE, A0) A. 0, 0 B. 0, 1 C. 1, 0 D. 1, 1  List II (What is read/written)  1 byte from/to odd address  1 byte from/to even address  16-bit word (both bytes)  None (no byte…

Accepted Answer

Introduction / Context: The 8086 has a 16-bit data bus with byte enables: BHE# (high-byte enable, active low) and the least significant address line A0. Understanding their combinations clarifies how even and odd byte locations are accessed and when full 16-bit words are transferred. Given Data / Assumptions: BHE in the pair (BHE, A0) is interpreted with 0 = asserted (enable high byte) and 1 = deasserted. A0 = 0 targets an even boundary (low byte), A0 = 1 targets an odd byte. Word transfer occurs when both low and high bytes are enabled simultaneously. Concept / Approach: Map each control combination to which byte lanes are enabled: low byte enable comes from A0 = 0; high byte enable comes from BHE = 0. Both enabled means a 16-bit word; only one enabled means a single byte at even or odd address; neither enabled means no transfer. Step-by-Step Solution: A (0,0): high byte enabled and low byte at even address enabled → full 16-bit word ⇒ 3.B (0,1): only high byte enabled → single byte at odd address ⇒ 1.C (1,0): only low byte enabled → single byte at even address ⇒ 2.D (1,1): no byte enabled → none ⇒ 4. Verification / Alternative check: Refer to 8086 memory interface timing diagrams: word accesses to even addresses assert both BHE# and A0=0; odd-byte access requires BHE# only; even-byte access uses A0=0 only. Why Other Options Are Wrong: Any mapping that assigns (0,0) to a single byte contradicts the 16-bit bus operation. Similarly, (1,1) must correspond to no active byte enable. Common Pitfalls: Forgetting that BHE is active low, or mixing up even/odd byte selection relative to A0. Also, assuming a word at an odd address is a single cycle; in fact, it typically requires two cycles. Final Answer: A-3, B-1, C-2, D-4

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