GPS ranging signals — operational L-band frequencies The standard GPS system performs code and carrier ranging using how many L-band frequencies?
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A3 L-band frequencies
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B2 L-band frequencies
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C2 C-band frequencies
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D3 C-band frequencies
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ENone of these
Answer
Correct Answer: 2 L-band frequencies
Explanation
Introduction / Context:GPS signals occupy L-band (approximately 1–2 GHz) for reliable propagation through the ionosphere and foliage. Classic ranging uses distinct L-band carriers and associated codes for positioning and ionospheric delay mitigation.
Given Data / Assumptions:
- Conventional GPS references the legacy core: L1 and L2.
- Modern signals (e.g., L5) exist but the canonical answer remains two L-band frequencies for standard dual-frequency operations.
- Range measurements imply code and carrier observations on these carriers.
Concept / Approach:Dual-frequency ranging exploits the dispersive ionosphere: combining measurements on L1 and L2 removes first-order ionospheric error. Additional bands (like L5) enhance performance but the minimum standard for “dual-frequency GPS” is two L-band frequencies.
Step-by-Step Reasoning:
1) Identify legacy carriers: L1 (~1575.42 MHz) and L2 (~1227.60 MHz).2) Dual-frequency combination reduces ionospheric delay.3) Therefore, GPS range measurements are traditionally made on two L-band frequencies.Verification / Alternative check:Receiver specifications commonly cite L1/L2 tracking for survey and high-grade navigation; L1-only is single-frequency.
Why Other Options Are Wrong:
- 3 L-band or C-band options: Not representative of classic GPS; C-band is not used for GPS navigation signals.
- None of these: Incorrect since two L-bands are standard.
Common Pitfalls:Confusing modern multi-band GNSS (adding L5/E5) with the minimum dual-frequency requirement.
Final Answer:2 L-band frequencies