DME Ground Apparatus Squitter Pulse Rate Stabilization
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Solution Overview
Problem
Existing DME ground apparatuses are susceptible to external noise, causing variations in the transmission rate of squitter pulses, which are essential for maintaining automatic gain control in aircraft interrogators.
Innovation Solution
A DME ground apparatus with a transponder unit and a monitor control unit that generates and transmits squitter pulses independently of thermal noise, using a digital PN code generating circuit to ensure consistent transmission rates, replacing response pulses when the transmission rate falls below a preset value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an analog circuit utilizing thermal noise is used to generate squitter pulses at random time intervals, then the randomness and correlation reduction of squitter pulses is improved, but the transmission rate becomes unstable and deviates from the appropriate range due to susceptibility to external noise
Solution Approach 1:
The patent replaces the analog noise-based circuit with a digital circuit that generates pseudo-random squitter pulses using a pseudo-random code sequence. This substitution eliminates susceptibility to thermal noise and external interference while maintaining the required randomness properties, thereby stabilizing the transmission rate within the appropriate range.
Solution Approach 2:
The patent changes the generation mechanism from analog thermal noise to digital pseudo-random code, altering the fundamental parameter of how randomness is achieved. This allows precise control over the transmission rate through digital logic while preserving the statistical properties needed for low correlation with interrogation pulses.
2Adaptability or versatility
If squitter pulses are transmitted at random time intervals to reduce correlation with interrogation pulses, then the automatic gain control in aircraft interrogators is maintained, but the transmission rate varies and may fall outside the appropriate range
Solution Approach 1:
The patent replaces the analog noise-based timing mechanism with a digital pseudo-random code generator that produces squitter pulses at precisely controlled random intervals. The digital implementation ensures that while the transmission times remain random for low correlation, the overall rate is accurately maintained within the specified range through digital logic control.
Solution Approach 2:
The patent incorporates a control mechanism that monitors the transmission rate of squitter pulses and adjusts the generation timing accordingly. This feedback ensures that despite the random intervals required for low correlation, the average transmission rate remains within the appropriate range for maintaining automatic gain control in aircraft interrogators.
Data Source
AI summary
In a DME ground apparatus, under the control of a transmission-rate monitoring control unit, the transponder unit decodes an interrogation signal it has received and generates a response signal. The transmission rate at which to transmit the response signal is monitored. If the result of the monitoring indicates that the transmission rate has reached a preset value, the response signal is transmitted from the DME ground apparatus. If the result of the monitoring indicates that the transmission rate has not reached a preset value, squitter pulses are transmitted from the DME ground apparatus.