CMOS Variable Bandwidth FIR Filter for Pulsed Radar Noise Reduction
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Solution Overview
Problem
Conventional radar systems face suboptimal performance due to fixed bandwidth filters that allow unwanted noise to pass through when pulse widths vary, affecting signal-to-noise ratio (SNR) and accuracy in range determination.
Innovation Solution
A variable bandwidth filter is developed, tunable on a CMOS chip, which adjusts its passband based on pulse width, utilizing a finite impulse response (FIR) filter with tunable transconductors to dynamically change bandwidth in response to changing pulse widths, enhancing SNR and accuracy in pulsed radar systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed bandwidth filter is used to match the narrowest pulse width, then the filter provides adequate noise filtering for narrow pulses, but unwanted noise passes through when wider pulses are transmitted, degrading signal-to-noise ratio
Solution Approach 1:
The filter bandwidth is made dynamically adjustable through a variable capacitor array that can be selectively switched to change the total capacitance value. This allows the filter bandwidth to adapt to different pulse widths, providing optimal noise filtering for each pulse width condition while maintaining the ability to handle varying radar operational requirements
Solution Approach 2:
The filter's key parameter (bandwidth) is changed by varying the capacitance value in discrete steps. By switching different capacitor combinations in parallel, the total capacitance changes, which directly adjusts the filter bandwidth to match the transmitted pulse width, thereby optimizing the signal-to-noise ratio for each pulse condition
2Reliability
If the filter bandwidth is designed for the narrowest pulse, then narrow pulses are properly filtered, but the filter cannot effectively filter noise for wider pulses
Solution Approach 1:
The filter transitions from a static fixed bandwidth design to a dynamic variable bandwidth design. The bandwidth can be adjusted in real-time based on the transmitted pulse width, ensuring reliable noise filtering performance across all pulse width conditions while maintaining the filtering effectiveness for narrow pulses
Solution Approach 2:
The filter is designed to perform multiple filtering functions across different bandwidth conditions. By incorporating a switchable capacitor array, the single filter structure can adapt to handle both narrow and wide pulse conditions, making it a universal filtering solution for varying radar operational modes rather than requiring separate filters for each pulse width
Data Source
AI summary
A variable bandwidth filter is described herein, wherein a bandwidth of a passband of the variable bandwidth filter is dynamically tunable. The variable bandwidth tuner is implemented on a CMOS chip, and acts to filter analog signals. The variable bandwidth filter comprises a plurality of finite impulse response (FIR) filters, wherein each FIR filter comprises a plurality of tunable transconductors. The tunable transconductors are tunable in their gain.