Radar Signal Processor Feedback Circuit for DC Offset Transients
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Solution Overview
Problem
Radar systems face challenges in effectively suppressing DC offset transient response components during frequency conversion, particularly in millimeter wave radar systems, where conventional high-pass filter technologies are not practical due to the low frequency band requirements.
Innovation Solution
A radar signal processor with an amplifier circuit and feedback circuit that generates control pulses to selectively cut off the frequency band including DC offset transient response frequencies during specific periods of chirp frequency changes, using a high-pass filter with adjustable RC time constants controlled by switches to minimize DC offset impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional high-pass filter technologies are used to suppress DC offset transient response components, then DC offset suppression is improved, but device complexity and impracticality increase due to low frequency band requirements in millimeter wave radar systems
Solution Approach 1:
The patent changes the parameter of cutoff frequency dynamically by controlling the RC time constant of the high-pass filter through switchable resistors. This allows the filter to adapt to different operating conditions (chirp start/stop moments) rather than using a fixed high cutoff frequency, thereby suppressing DC offset without requiring overly complex filter design
Solution Approach 2:
The patent applies periodic action by activating the high-pass filter only during specific periods (chirp start and stop moments) when DC offset transient response occurs. The control circuit generates control signals to switch the filter on/off periodically, matching the chirp transmission cycle, thus suppressing harmful DC offset components without continuously complicating the signal path
2Object-affected harmful factors
If the cutoff frequency of the high-pass filter is set high to suppress DC offset, then DC offset suppression is improved, but signal processing accuracy deteriorates due to loss of useful signal components in the low frequency band
Solution Approach 1:
The patent makes the cutoff frequency dynamic rather than fixed. The control circuit adjusts the RC time constant by switching resistors in response to chirp control signals, raising the cutoff frequency only when needed (during chirp transitions) and lowering it during normal operation, thus preserving both DC offset suppression and signal accuracy
Solution Approach 2:
The patent applies preliminary action by raising the cutoff frequency before DC offset transient response occurs (at chirp start/stop moments). The control circuit anticipates the timing of DC offset generation and pre-adjusts the filter parameters, preventing harmful components from entering the signal path while preserving useful low-frequency signal components during normal operation
3Measurement precision
If high-gain operation is implemented to improve detection sensitivity, then detection sensitivity is improved, but DC offset transient response components increase, deteriorating signal processing accuracy
Solution Approach 1:
The patent implements feedback by using the output of the high-pass filter to control its own input through the control circuit. The control circuit monitors the chirp transmission state and generates control signals that feed back to adjust the filter's RC time constant, creating a closed-loop system that automatically suppresses DC offset while maintaining high-gain operation for improved detection sensitivity
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
The solution effectively reduces DC offset transient response components during demodulation, enabling high-gain operation and size reduction in radar systems by synchronizing the frequency band cutoff with chirp control signals, improving signal processing accuracy.
Implementation Method 1
The feedback circuit is configured to detect an output signal of the variable amplifier as a detection signal and feeds back a signal of a frequency band included in the detection signal to an input of the variable amplifier
Implementation Method 2
using a high-pass filter with adjustable RC time constants controlled by switches to minimize DC offset impact
Data Source
AI summary
A radar system includes a transmitter circuit, which transmits a radar wave having a chirp frequency gradually increasing or decreasing to a target, and a frequency conversion circuit, which demodulates a signal of the radar wave reflected at the target by frequency-conversion in correspondence to the chirp frequency. A radar signal processor includes a variable amplifier connected to an output side of the frequency conversion circuit, and a feedback circuit which detects an output of the variable amplifier as a detection signal and feeds back a signal of a frequency band included in the detection signal to an input of the variable amplifier. The feedback circuit is configured to cut off and not cut off a frequency band including a DC offset transient response frequency, which occurs at time of frequency conversion by the frequency conversion circuit, during a specified period and a period other than the specified period, respectively. The specified period is a predetermined first period from starting of a demodulation operation of the frequency conversion circuit and/or a predetermined second period from ending of the demodulation operation of the frequency operation of the frequency conversion circuit.