Radar Filter Circuit Topology for Low-Cutoff Sensing in Less Area
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Solution Overview
Problem
Existing radar sensors face an issue of increased design area due to the need for low cutoff frequencies in high-pass filters, which leads to larger capacitor and resistor sizes, thus requiring a solution to maintain accuracy while reducing the overall size of the filtering device.
Innovation Solution
A filtering device is designed with an amplification circuit, filter circuit, and feedback circuit to set cutoff frequencies based on gain values, allowing for a smaller design area by using higher cutoff frequencies in the filter circuit, thereby reducing the size of capacitors and resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cutoff frequency of the high-pass filter is reduced to several tens of kHz for accurate distance sensing, then the measurement precision is improved, but the size of the capacitor and resistor increases, leading to a larger design area
Solution Approach 1:
The filter is divided into two separate circuits: a first filter circuit with a higher cutoff frequency (second cutoff frequency) and a second filter circuit with a lower cutoff frequency (first cutoff frequency). This segmentation allows each circuit to use smaller component values while achieving the overall low-pass filtering effect needed for accurate distance sensing.
Solution Approach 2:
An intermediate signal processing stage is introduced where the reflection signal is first processed by the first filter circuit, then by the second filter circuit. This intermediary approach enables the system to achieve the equivalent effect of a single low-cutoff-frequency filter while using smaller components throughout the signal path.
2Measurement precision
If the cutoff frequency of the high-pass filter is reduced, then the measurement precision is improved, but the size of the capacitor and resistor increases
Solution Approach 1:
The filtering function is segmented into two stages with different cutoff frequencies. The first filter circuit uses a higher cutoff frequency allowing smaller capacitors and resistors, while the second filter circuit compensates to achieve the overall low-frequency response needed for accurate measurements.
Solution Approach 2:
The system changes the parameter of cutoff frequency across different filter stages rather than using a single low cutoff frequency throughout. This allows optimization of component sizes at each stage while maintaining the overall frequency response characteristics needed for precision sensing.
3Measurement precision
If the size of the high-pass filter is increased to maintain a low cutoff frequency, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
Rather than using a single complex filter with many large components, the system segments the filtering into two simpler stages with smaller components each, reducing overall device complexity while maintaining measurement precision.
Data Source
AI summary
A filtering device for passing a frequency component above a first cutoff frequency in an input signal includes an amplification circuit configured to generate an amplification signal based on the input signal, a first feedback signal, and a second feedback signal, a filter circuit configured to generate an output signal by passing a frequency component above a second cutoff frequency higher than the first cutoff frequency in the amplification signal, and a feedback circuit configured to generate the first feedback signal and the second feedback signal by amplifying the output signal, the filter circuit configured to set the first cutoff frequency based on a first amplification value corresponding to a gain of the amplification circuit and the second cutoff frequency.