Mixer-First RF Receiver Spillover Cancellation for Automotive Radar
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Solution Overview
Problem
Automotive radar sensors face limitations due to TX-to-RX spillover, which causes receiver saturation and constraints linearity, particularly in low-supply-voltage implementations, and existing solutions are costly in terms of complexity and power consumption.
Innovation Solution
A low-noise high-linearity RF receiver down-converter circuit with a mixer-first topology and self-cancellation of TX-to-RX spillover, embedded in an active load, eliminating the need for a low-noise amplifier and voltage gain stages at the RF level, and incorporating a spillover cancellation circuit at the mixer output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-noise amplifier (LNA) and voltage gain stages at RF level are used, then noise performance is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent removes the low-noise amplifier (LNA) and voltage gain stages from the RF receiver chain, extracting these components entirely from the system. Instead, it employs a current-driven mixer that directly converts RF signals to IF signals, eliminating the need for separate amplification stages and thereby reducing circuit complexity and power consumption while maintaining noise performance through the mixer's inherent conversion gain
Solution Approach 2:
The patent substitutes the traditional voltage-based RF amplification mechanism with a current-driven mixing mechanism. The current-driven mixer directly converts RF voltage signals to current signals at IF frequency, replacing the need for voltage gain stages and LNAs, thus simplifying the overall receiver architecture
2Manufacturing precision
If TX-to-RX spillover cancellation is implemented, then linearity is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent merges the TX-to-RX spillover cancellation function directly into the current-driven mixer circuit. The mixer's current output naturally provides a signal that can be fed back through a feedback network to cancel the spillover interference at the RF input, combining the mixing function and interference cancellation function into a single integrated circuit block, thereby improving linearity without adding separate cancellation circuits
Solution Approach 2:
The patent implements a feedback network that takes a portion of the mixer's current output, processes it through impedance transformation and phase adjustment, and feeds it back to the RF input to cancel the TX-to-RX spillover signal. This feedback mechanism continuously compensates for interference, improving linearity while using the existing mixer circuitry
3Power
If voltage gain stages at RF level are used, then signal amplification is improved, but immunity to TX spillover deteriorates
Solution Approach 1:
The patent replaces voltage-based RF amplification with a current-driven mixing approach. The current-driven mixer provides conversion gain from RF to IF frequency through its inherent mixing action, eliminating the need for voltage gain stages that would amplify both the desired signal and the harmful TX spillover interference at RF frequency
Solution Approach 2:
The patent changes the operating domain from voltage amplification at RF frequency to current mixing at RF-IF frequency conversion. By operating in the current domain and performing frequency conversion, the system achieves signal amplification through conversion gain rather than voltage gain, thereby avoiding amplification of the spillover interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution provides high linearity and noise performance with reduced complexity and power consumption, improving immunity to TX spillover and relaxing linearity requirements, suitable for low-voltage CMOS implementation.
Implementation Method 1
a mixer circuit, comprising a RF input, a LO input and an IF output and configured to: a) receive said RF current signal at said RF input; b) receive a LO signal at said LO input; c) provide a mixed signal at said IF output, wherein the mixed signal comprises a frequency down-converted interfering component
Data Source
AI summary
An input receives a radio frequency (RF) signal having an interfering component superimposed thereon. The RF signal is mixed with a local oscillator (LO) signal and down-converted to an intermediate frequency (IF) to generate a mixed signal which includes a frequency down-converted interfering component. The mixed signal is amplified by an amplifier to generate an output signal. A feedback loop processes the output signal to generate a correction signal for cancelling the frequency down-converted interfering component at the input of the amplifier. The feedback loop includes a low-pass filter and a amplification circuit which outputs the correction signal.