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An RF-Domain Leakage Cancellation Scheme for FMCW Radars

Yikuan Chen, Ali Niknejad

Abstract

This paper proposes a novel solution to address the leakage from the transmitter (TX) to the receiver (RX) in frequency-modulated continuous-wave (FMCW) radars. The proposed scheme replicates the leakage using an in-phase and quadrature mixer (IQ-mixer) and performs leakage cancellation in the radio-frequency (RF) domain. This approach utilizes a Wilkinson power combiner after the RX antenna to subtract the replicated leakage signal from the received signal, ensuring that only the true target signal reaches the low-noise amplifier (LNA). This scheme enhances the dynamic range and the receiver's ability to discern proximate targets from previously indistinguishable low beat-frequency clutter. In addition, the proposed technique incorporates a second IQ-mixer based complex modulator in the transmitter to tune the leakage beat frequency. This allows for accurate estimation of the leakage amplitude and phase without additional hardware. Simulation results show more than 20 dB of leakage cancellation.

An RF-Domain Leakage Cancellation Scheme for FMCW Radars

Abstract

This paper proposes a novel solution to address the leakage from the transmitter (TX) to the receiver (RX) in frequency-modulated continuous-wave (FMCW) radars. The proposed scheme replicates the leakage using an in-phase and quadrature mixer (IQ-mixer) and performs leakage cancellation in the radio-frequency (RF) domain. This approach utilizes a Wilkinson power combiner after the RX antenna to subtract the replicated leakage signal from the received signal, ensuring that only the true target signal reaches the low-noise amplifier (LNA). This scheme enhances the dynamic range and the receiver's ability to discern proximate targets from previously indistinguishable low beat-frequency clutter. In addition, the proposed technique incorporates a second IQ-mixer based complex modulator in the transmitter to tune the leakage beat frequency. This allows for accurate estimation of the leakage amplitude and phase without additional hardware. Simulation results show more than 20 dB of leakage cancellation.
Paper Structure (15 sections, 2 equations, 5 figures)

This paper contains 15 sections, 2 equations, 5 figures.

Table of Contents

  1. Introduction
  2. Theory of FMCW Operation
  3. Range Detection with FMCW Radars
  4. Impact of Spectral Leakage
  5. Proposed System Architecture
  6. Leakage Cancellation Architecture Overview
  7. Leakage Cancellation-First Receiver
  8. The TX IQ-mixer
  9. Leakage Cancellation in an Array
  10. System Simulation Results
  11. System Parameters
  12. Operation Steps
  13. Results
  14. Concerns of the Proposed Approach
  15. Conclusion

Figures (5)

  • Figure 1: Simplified FMCW radar architecture and self-interference paths.
  • Figure 2: (a) Self-interference from different neighboring TX elements in an array. (b) Resulting leakage signals and their beat frequency spectrum.
  • Figure 3: (a) A non-coherently-sampled signal and its FFT spectrum with spread energy. (b) A coherently-sampled signal and its FFT with energy concentrated in one bin.
  • Figure 4: System block diagram of the proposed leakage cancellation scheme.
  • Figure 5: (a) Simulated range FFT spectrum with and without leakage cancellation with target 10 cm away from the radar. (b) Simulated range FFT spectrum with and without leakage cancellation with target 20 cm away from the radar.