In microwave engineering, resonators are employed for which of the following applications?
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Amicrowave oscillators
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Bmicrowave narrow-band amplifiers
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Cmicrowave frequency meters (wavemeters)
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Dall of the above
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Enone of the above
Answer
Correct Answer: all of the above
Explanation
Introduction / Context:Microwave resonators (cavity, dielectric, or microstrip) store electromagnetic energy at discrete resonant frequencies. Their high Q and frequency selectivity make them fundamental in many RF/microwave subsystems.
Given Data / Assumptions:
- High-Q resonators provide narrowband frequency selection.
- Appropriate coupling mechanisms are available (loops, probes, irises).
- Losses are sufficiently low to sustain oscillation or enable sharp filtering.
Concept / Approach:
Resonators determine frequency in oscillators, set passbands in narrow-band amplifiers and filters, and act as frequency-selective standards in frequency meters. The same physical principle of resonance underlies all three applications.
Step-by-Step Solution:
Oscillators: Positive feedback loop oscillates at the resonator’s natural frequency.Amplifiers: Resonators in input/output networks provide gain only in a narrow band, improving selectivity and noise performance.Frequency meters: Tunable resonators that indicate resonance with an unknown source allow precise frequency readout.Hence, all listed applications are valid.Verification / Alternative check:
Classic waveguide cavity oscillators, helical resonators in narrow-band LNAs, and cavity wavemeters in labs are standard implementations.
Why Other Options Are Wrong:
- Choices a, b, or c alone are incomplete; resonators are useful in all three contexts.
- 'none of the above': Contradicted by widespread practice.
Common Pitfalls:
Assuming resonators are only for filters; overlooking their role as the frequency-determining element in oscillators and as precision standards in wavemeters.
Final Answer:
all of the above