Automotive Radar Gain Amplifier With Pole-Zero Alias Band Attenuation
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Solution Overview
Problem
Voltage gain amplifiers in automotive radar systems face challenges in achieving desired attenuation in alias bands without experiencing gain peaking, which affects the accuracy of distance determination in radar systems.
Innovation Solution
A voltage gain amplifier design incorporating a differential pair of NPN bipolar junction transistors with a high-pass filter and a transistor circuit driven by high-frequency components to remove undesirable frequencies, along with optional chopper and low-pass filter configurations to downconvert and upconvert signals, ensuring effective attenuation of alias band signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage gain amplifier is designed to attenuate alias band signals, then attenuation in alias bands is improved, but gain peaking occurs in the bandwidth
Solution Approach 1:
The patent divides the frequency response into two distinct segments: one for the intermediate frequency band (0-25 MHz) and another for the alias band (75-100 MHz). By using a multi-stage amplifier architecture with different gain stages optimized for different frequency ranges, the design achieves flat gain in the intermediate band while providing attenuation in the alias band, eliminating gain peaking.
Solution Approach 2:
The patent introduces an intermediary feedback network that selectively affects different frequency bands. The feedback path includes frequency-dependent elements (capacitors and resistors) that create a feedback mechanism which suppresses alias band signals without impacting the intermediate frequency band, thereby preventing gain peaking while achieving alias band attenuation.
2Measurement precision
If the low-pass filter is placed before the voltage gain amplifier, then alias band signals are filtered, but noise introduced by the filter is amplified
Solution Approach 1:
The patent performs preliminary attenuation of alias band signals within the voltage gain amplifier itself, before the signals would be further processed. By integrating the attenuation function into the amplifier stages rather than relying on a preceding low-pass filter, the design prevents noise introduced by external filtering from being amplified, while still achieving the required alias band suppression.
3Power
If the voltage gain amplifier amplifies all frequency components, then signal strength is improved, but alias band signals saturate the amplifier
Solution Approach 1:
The patent applies local quality by giving different gain characteristics to different frequency components within the amplifier. The first voltage gain stage provides high gain for the intermediate frequency band while the second stage provides attenuation for the alias band. This localized frequency-dependent gain control allows strong signal amplification without alias band saturation.
Data Source
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AI summary
Disclosed herein is a voltage gain amplifier (15) for use in an automotive radar receiver chain. The voltage gain amplifier utilizes pole-zero cancellation to yield a desired transfer function without gain peaking at a bandwidth in which attenuation is desired, and utilizes a low pass filter effectively formed by a feedback loop including a high pass filter (R1, C1) and a differential amplifier (NP3, NP4) to ensure the desired level of attenuation at the desired bandwidth. In some instances, a chopper may be utilized in the feedback loop prior to the high pass filter (R1, C1), and after the differential amplifier, so as to reduce the bandwidth of the differential amplifier (NP3, NP4) in the feedback loop.