Switched-Capacitor Radar Baseband Cancellation for Self-Interference
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Solution Overview
Problem
Radar systems suffer from self-interference due to amplifier nonlinearities, leading to ghost targets and increased noise floors, which are particularly challenging for digitally coded radars and result in stringent linearity and dynamic range requirements that are impractical in terms of power dissipation and silicon area.
Innovation Solution
A radar transceiver with a correction module that integrates sampling, cancellation, and amplification in the discrete time domain using switched capacitors to cancel self-interference, reducing linearity and dynamic range requirements on the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If linear broadband amplification is used to meet dynamic range requirements, then receiver performance is improved, but power dissipation and silicon area increase significantly
Solution Approach 1:
The receiver chain is segmented into multiple functional blocks (LNA, mixer, VGA, ADC) with distributed gain allocation. The LNA provides initial low-noise amplification, the mixer provides conversion gain, and the VGA provides programmable baseband gain, allowing the system to achieve high dynamic range without requiring a single high-power linear broadband amplifier across the entire frequency range.
Solution Approach 2:
The system uses a variable gain amplifier (VGA) with programmable gain control in the baseband path instead of a fixed high-gain linear amplifier. This dynamic gain adjustment allows the receiver to adapt to different signal levels and maintain optimal performance across varying operating conditions while minimizing power consumption by only providing necessary amplification.
2Measurement precision
If high linearity is implemented to suppress self-interference, then detection accuracy is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent acknowledges that self-interference and amplifier nonlinearities cannot be completely eliminated, but instead converts this harmful effect into a manageable problem by using digital signal processing techniques. The system uses the known transmit signal waveform to generate a reference and applies digital filtering and correlation methods to suppress the self-interference and ghost targets in the digital domain, turning the limitation into an opportunity for flexible digital processing.
Solution Approach 2:
The system changes the operating parameters of the amplifiers to balance linearity and power consumption. Rather than designing for maximum linearity throughout the entire signal chain, the patent optimizes each stage's linearity requirements based on its specific function, and uses digital processing parameters (filtering, correlation) to compensate for residual nonlinearities, thereby reducing overall device complexity.
3Measurement precision
If stringent dynamic range requirements are imposed on ADC to handle self-interference, then measurement precision is improved, but power dissipation and silicon area increase
Solution Approach 1:
The system performs preliminary analog signal processing (LNA amplification, mixing, and VGA gain adjustment) before the ADC to pre-condition the signal and reduce the dynamic range burden on the ADC. By establishing the appropriate signal level and suppressing strong self-interference components in the analog domain, the ADC only needs to resolve the remaining weaker target signals, allowing for lower-resolution (and thus smaller area) ADC implementation.
Data Source
AI summary
The disclosure relates to cancellation of self-interference in radar transceivers. Example embodiments include a radar transceiver in which a correction module is configured to combine an analog baseband received signal with a digital correction signal to provide a corrected analog baseband signal, the correction module comprising a sampling capacitor, a variable cancellation capacitor controllable by the digital correction signal, an amplifier and a switching arrangement configured to sample the baseband received signal and sum a sampled charge across the sampling capacitor with a charge across the variable cancellation capacitor to provide a residue signal to the amplifier, the amplifier configured to amplify the residue signal to provide the corrected analog baseband signal to an ADC.