RF Transceiver Calibration Circuit for ADC Saturation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Radar systems face issues with ADC saturation and amplitude clipping due to parasitic transient signals and close-in reflections when switching operation modes, which limit performance and detection accuracy.
Innovation Solution
A circuit with a mixer, selectable local oscillator phase circuit, and programmable filter is used to frequency-translate signals with a calibrated phase shift and adjust cutoff frequencies, reducing parasitic signals and close-in reflections by shifting DC levels and adjusting filter bandwidths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the radar system operates in active mode with wide bandwidth to detect reflected signals, then detection capability is improved, but parasitic transient signals cause ADC saturation and amplitude clipping
Solution Approach 1:
The system performs a calibration mode operation before active radar mode to pre-characterize and store parasitic signal signatures. This preliminary action enables the system to identify and mitigate parasitic transient signals during subsequent active operation, preventing ADC saturation while maintaining detection accuracy.
Solution Approach 2:
The patent introduces an intermediate calibration mode that acts as a mediator between the inactive and active radar modes. This calibration mode captures parasitic signal characteristics without transmitting high-power radar signals, creating a safe intermediate state that enables subsequent parasitic signal removal during active operation.
2Measurement precision
If the system uses a fixed filter bandwidth optimized for active mode, then reflected signal detection is improved, but parasitic signals near DC frequency are not adequately filtered
Solution Approach 1:
The system dynamically adjusts the filter bandwidth based on the operational mode. During calibration mode, a first bandwidth is used to capture parasitic signal characteristics near DC frequency. During active mode, the bandwidth is adjusted to a second value optimized for reflected signal detection while maintaining parasitic signal rejection capability.
Solution Approach 2:
The patent changes the filter bandwidth parameter between different operational modes. The filter bandwidth is set to a first value during calibration mode to effectively filter parasitic signals, and then changed to a second value during active mode to optimize reflected signal detection while maintaining parasitic signal rejection.
3Measurement precision
If the radar system transmits high power to improve detection range, then detection capability is improved, but close-in reflections from stationary targets saturate the receiver
Solution Approach 1:
The system converts the harmful close-in reflections into a useful calibration resource. By deliberately capturing these strong reflections during calibration mode, the system characterizes their signature and uses this knowledge to remove or mitigate their effect during active operation, turning a saturation problem into a calibration opportunity.
Solution Approach 2:
The calibration mode is executed before active radar operation to pre-capture and characterize close-in reflection signals. This preliminary characterization enables the system to identify and remove these harmful signals during subsequent active operation, preventing receiver saturation while maintaining extended detection range.
4Productivity
If the system operates continuously in active mode, then detection productivity is improved, but parasitic transient signals accumulate causing performance degradation
Solution Approach 1:
The system implements periodic calibration mode operations interspersed with active radar mode operations. This periodic switching allows the system to refresh its parasitic signal characterization at regular intervals, preventing accumulation of parasitic signal effects and maintaining signal quality while preserving overall detection productivity.
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 effectively reduces ADC saturation and amplitude clipping, improving detection accuracy and system performance by isolating parasitic signals and enhancing signal processing of reflected RF signals.
Implementation Method 1
a mixer having an input port configured to be coupled to an antenna of a radio frequency (RF) transceiver; and a selectable local oscillator (LO) phase circuit coupled to an LO port of the mixer, the selectable LO phase circuit configured to provide a calibrated phase shift to a local oscillator signal
Implementation Method 2
a filter coupled to an output of the mixer, the filter having a selectable cutoff frequency
Data Source
AI summary
In accordance with an embodiment, a method for operating a radio frequency (RF) transceiver includes frequency-translating, using a local oscillator signal having a calibrated phase shift, a signal received at an antenna of an RF transceiver; filtering the frequency-translated signal using a programmable filter of the RF transceiver to produce a filtered frequency-translated signal; and changing a cutoff frequency of the programmable filter from a first cutoff frequency to a second cutoff frequency in response to the RF transceiver switching operation from a first mode to a second mode.