Digital Radio Altimeter Validation System Latency Compensation
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Solution Overview
Problem
Existing radio altimeter validation systems struggle to flexibly simulate both very low (close to 0 feet) and very high (close to 10,000 feet) heights, especially for controlled slope radio altimeters, due to limitations in digital systems and physical delay lines.
Innovation Solution
A digital radio altimeter validation system with an input/output RF interface, characterized by an incompressible latency τ, receives a linear chirp FMCW signal and retransmits it with a configurable delay, ensuring frequency compensation for the latency τ. This system uses a series of converters, shifters, and time delay units to achieve frequency compensation and simulate various heights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If physical delay lines are used to simulate different heights, then the system can provide test scenarios for various heights, but the system becomes bulky, expensive, and limited in flexibility
Solution Approach 1:
The patent replaces physical delay lines (mechanical/electrical system) with a digital signal processing system that uses software-based delay implementation. The digital system processes FMCW signals through mathematical operations including phase compensation and delay calculation, eliminating the need for bulky physical delay lines while maintaining the ability to simulate various heights flexibly through programmable parameters
Solution Approach 2:
The patent implements height simulation by changing digital parameters rather than physical configurations. The system uses configurable delay parameters and phase compensation values that can be adjusted through software to represent different heights, allowing the same hardware to simulate a wide range of heights from very low to very high without physical reconfiguration
2Adaptability or versatility
If digital systems are used to simulate heights, then flexibility is improved, but the system cannot simulate very low heights for controlled slope radio altimeters
Solution Approach 1:
The patent applies preliminary phase compensation to counteract the effects of system latency before delay simulation. By calculating and applying phase compensation based on the known latency τ of the system, the system pre-corrects the signal to eliminate apparent delay, enabling accurate simulation of very low heights where the propagation delay is comparable to or smaller than the system latency
Solution Approach 2:
The patent introduces phase compensation as an intermediary process between the received FMCW signal and the delay simulation. The phase compensation acts as a mediator that removes the distorting effect of system latency, allowing the subsequent digital delay to accurately represent the intended height without being corrupted by the inherent system delay
3Device complexity
If system latency is not compensated, then the system is simpler, but the frequency of the signal shows apparent delay that prevents accurate simulation
Solution Approach 1:
The system performs self-compensation by using knowledge of its own latency τ to correct its output. The phase compensation calculation uses the known system characteristics (latency value) to automatically adjust the signal, making the system self-correcting without requiring external calibration or complex additional hardware
Data Source
AI summary
A digital radio altimeter validation system, provided with an input/output RF interface and characterized by an incompressible latency τ, configured to receive a linear chirp (FMCW) signal s(t) with linearly frequency-modulated continuous-wave f(t)=αt+β and with quadratic phase s(t)=e2jπ(αt<sup2>2</sup2>/2+βt+γ), that can also be written in complex form in cartesian coordinates I(t)+jQ(t), t representing the time, and configured to retransmit it according to a configurable delay and deliver to the radio altimeter a signal I′(t)+jQ′(t) that is exactly frequency-compensated for the latency τ by a linear extrapolation of its phase by calculation of difference between the current phase and the digitally delayed phase of the value to be compensated τ.