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Separable Delay And Doppler Estimation In Passive Radar

Mats Viberg, Daniele Gerosa, Tomas McKelvey, Patrik Dammert, Thomas Eriksson

TL;DR

The paper addresses estimating a moving target's location and velocity in a passive radar setting where a Reference Channel provides the IO waveform and a Surveillance Channel carries interference and the target return. It introduces a separable estimation strategy that first performs a 1-D delay search using a first-order Doppler approximation and interference projection, then recovers Doppler across batches via phase regression (Tretter's method), dramatically reducing per-node search dimensionality and data transmission to the central node. The main contributions are a novel separable delay-Doppler estimator for IO-reflected signals, substantial computational and communication savings in distributed radar, and improved Doppler estimation across a broad range of target speeds while maintaining delay accuracy for large batch sizes. Numerical results show that with sufficiently large batch sizes, delay accuracy matches the full 2-D method, while Doppler estimates are consistently enhanced by the separable approach, highlighting practical benefits for scalable passive radar systems.

Abstract

In passive radar, a network of distributed sensors exploit signals from so-called Illuminators-of-Opportunity to detect and localize targets. We consider the case where the IO signal is available at each receiver node through a reference channel, whereas target returns corrupted by interference are collected in a separate surveillance channel. The problem formulation is similar to an active radar that uses a noise-like waveform, or an integrated sensing and communication application. The available data is first split into batches of manageable size. In the direct approach, the target's time-delay and Doppler parameters are estimated jointly by incoherently combining the batch-wise data. We propose a new method to estimate the time-delay separately, thus avoiding a costly 2-D search. Our approach is designed for slowly moving targets, and the accuracy of the time-delay estimate is similar to that of the full batch-wise 2-D method. Given the time-delay, the coherency between batches can be restored when estimating the Doppler parameter. Thereby, the separable approach is found to yield superior Doppler estimates over a wide parameter range. In addition to reducing computational complexity, the proposed separable estimation technique also significantly reduces the communication overhead in a distributed radar setting.

Separable Delay And Doppler Estimation In Passive Radar

TL;DR

The paper addresses estimating a moving target's location and velocity in a passive radar setting where a Reference Channel provides the IO waveform and a Surveillance Channel carries interference and the target return. It introduces a separable estimation strategy that first performs a 1-D delay search using a first-order Doppler approximation and interference projection, then recovers Doppler across batches via phase regression (Tretter's method), dramatically reducing per-node search dimensionality and data transmission to the central node. The main contributions are a novel separable delay-Doppler estimator for IO-reflected signals, substantial computational and communication savings in distributed radar, and improved Doppler estimation across a broad range of target speeds while maintaining delay accuracy for large batch sizes. Numerical results show that with sufficiently large batch sizes, delay accuracy matches the full 2-D method, while Doppler estimates are consistently enhanced by the separable approach, highlighting practical benefits for scalable passive radar systems.

Abstract

In passive radar, a network of distributed sensors exploit signals from so-called Illuminators-of-Opportunity to detect and localize targets. We consider the case where the IO signal is available at each receiver node through a reference channel, whereas target returns corrupted by interference are collected in a separate surveillance channel. The problem formulation is similar to an active radar that uses a noise-like waveform, or an integrated sensing and communication application. The available data is first split into batches of manageable size. In the direct approach, the target's time-delay and Doppler parameters are estimated jointly by incoherently combining the batch-wise data. We propose a new method to estimate the time-delay separately, thus avoiding a costly 2-D search. Our approach is designed for slowly moving targets, and the accuracy of the time-delay estimate is similar to that of the full batch-wise 2-D method. Given the time-delay, the coherency between batches can be restored when estimating the Doppler parameter. Thereby, the separable approach is found to yield superior Doppler estimates over a wide parameter range. In addition to reducing computational complexity, the proposed separable estimation technique also significantly reduces the communication overhead in a distributed radar setting.
Paper Structure (8 sections, 20 equations, 2 figures)

This paper contains 8 sections, 20 equations, 2 figures.

Table of Contents

  1. Introduction
  2. Problem Description and Data Model
  3. Target Parameter Estimation
  4. Baseline Approach: Full 2-D Search
  5. Target Localization
  6. Separable Delay and Doppler Estimation
  7. Numerical Examples
  8. Conclusions

Figures (2)

  • Figure 1: RMS error for a) time-delay and b) Doppler frequency estimates versus the number of batches. The size of each batch is fixed, so $N$ increases with $M$.
  • Figure 2: RMS error for a) time-delay and b) Doppler frequency estimates versus the target's Doppler frequency. The total data length $N$ is fixed.