Distributed Coherent Radar Layout for Phase Noise Cancellation
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Solution Overview
Problem
Distributed coherent radar systems suffer from reduced detection performance due to uncorrelated phase noise from local oscillators in individual radar units, which is not effectively attenuated during down mixing, particularly affecting targets with small cross-sections.
Innovation Solution
A distributed coherent radar system design that estimates phase noise using a configuration where antennas of each radar unit are aligned in one direction and offset in an orthogonal direction, allowing for phase noise estimation without requiring antennas to act as both transmitter and receiver, thereby reducing complexity and cost by avoiding circulators or power dividers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If local oscillators are used in each radar unit, then system complexity and cost are reduced, but phase noise becomes uncorrelated and detection performance deteriorates
Solution Approach 1:
A synchronization signal is introduced as an intermediary to coordinate the phase of local oscillators across distributed radar units. The synchronization signal, transmitted via a dedicated channel or existing communication infrastructure, enables each radar unit to align its local oscillator phase with a reference, thereby correlating phase noise across units without requiring a centralized oscillator.
Solution Approach 2:
The system implements phase feedback mechanisms where each radar unit monitors its local oscillator phase deviation from the synchronization reference and applies corrective phase adjustments. This feedback loop ensures that phase noise remains correlated across distributed units, maintaining detection performance while preserving the distributed architecture's simplicity.
2Device complexity
If antennas act as both transmitter and receiver, then device complexity is reduced, but coupling between Rx and Tx increases and cost increases due to circulators or power dividers
Solution Approach 1:
The antenna functions are segmented into separate transmit and receive antennas within each radar unit. This segmentation eliminates the need for circulators or power dividers by using dedicated transmit antennas for signal transmission and dedicated receive antennas for signal reception, thereby removing harmful Tx-Rx coupling while maintaining system simplicity.
Solution Approach 2:
The harmful coupling function is extracted from the system by separating transmit and receive antenna paths. Instead of using a single antenna that must handle both functions with additional components, the coupling-prone components (circulators, power dividers) are completely removed by assigning separate antennas to transmit and receive functions.
3Device complexity
If phase noise is not attenuated during down mixing, then system simplicity is maintained, but detection performance particularly for small cross-section targets deteriorates
Solution Approach 1:
The uncorrelated phase noise from distributed radar units, which initially appears harmful, is converted into a benefit through synchronization. By correlating the phase noise across units using synchronization signals, the system enables coherent integration of signals from multiple units, improving detection performance for small cross-section targets while maintaining the simplicity of distributed architecture.
Data Source
AI summary
Disclosed is a distributed coherent radar (DCR) system comprising: first and second radar units and a processer, the radar units each comprising: first and second antennas, aligned in a first direction, and offset in a second, orthogonal, direction, and a linear array of antennas distributed along the first direction and including the first or second antenna; wherein: the second radar unit is configured to receive, at is second antenna, a first signal, being a reflection, from a target, of a first frequency modulated continuous wave (FMCW) signal transmitted by the first radar unit first antenna; the first radar unit is configured to receive, at its second antenna, a second signal, being a reflection, from the target, of a second FMCW signal transmitted by the second radar unit first antenna; and the processor is configured to estimate phase noise from the first signal and the second signal.