STAR Subsystem External Noise Cancellation
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Solution Overview
Problem
Simultaneous transmit and receive systems face challenges in isolating high-power transmit signals and noise from receivers, leading to saturation or overwhelming of the receive signal, especially in applications like radar where antenna impedance worsens isolation, and external noise further complicates signal quality.
Innovation Solution
A wideband simultaneous transmit and receive (STAR) subsystem employs digital and analog cancellation techniques to minimize transmit signal leakage and external noise, using a combination of circulators, analog and digital cancellers, and active noise cancellation to preserve receiver sensitivity and achieve effective isolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circulator is inserted to isolate Tx and Rx signal paths, then signal path isolation is improved, but isolation effectiveness deteriorates when antenna active impedance worsens with scan angle
Solution Approach 1:
The patent implements feedback mechanisms where the received signal is fed back through a delay element and combiner to generate cancellation signals that counteract Tx leakage. The system continuously adapts to maintain effective isolation despite antenna impedance variations with scan angle.
Solution Approach 2:
The patent introduces intermediary components including delay elements, combiners, and cancellers that mediate between the Tx and Rx signal paths. These intermediaries process the signal to extract and cancel leakage components, providing stable isolation independent of antenna impedance changes.
2Device complexity
If STAR system shares single antenna for both Tx and Rx, then device complexity is reduced, but signal interference increases
Solution Approach 1:
The patent extracts and separates the harmful Tx leakage signal from the received signal using delay elements and combiners. By extracting the leakage component and processing it through cancellation circuits, the system eliminates interference while maintaining single-antenna operation.
Solution Approach 2:
The patent converts the harmful Tx leakage signal into a useful cancellation signal. The leaked signal is captured, delayed, and inverted to create a cancellation signal that actively removes the interference, turning the harm into a beneficial self-cancellation mechanism.
3Power
If high power Tx signal is transmitted, then transmit power is improved, but receiver saturation increases
Solution Approach 1:
The patent converts the harmful high-power Tx signal into a useful cancellation reference. The Tx signal is captured and processed to generate cancellation signals that actively compensate for the high power levels, allowing high transmit power operation without receiver saturation.
Solution Approach 2:
The patent uses feedback from the received signal to generate cancellation signals that counteract the high-power Tx interference. The feedback loop continuously adjusts the cancellation to maintain receiver operation within safe power ranges despite high transmit power.
Data Source
AI summary
A wideband simultaneous transmit and receive (STAR) subsystem for a radar or communications system including self-interference cancellation and external noise cancellation. The STAR subsystem includes a canceller circuit which digitally prepares a cancellation signal to cancel out leaked or reflected portions of the transmit signal and correlated noise in the receiver signal. The self-interference cancellation can be adaptively configured in a closed-loop mode, and operated open loop in real time to minimize bandwidth limitations and achieve wideband performance. The STAR subsystem also includes an external noise active canceller which greatly diminishes high-power external noise in the receiver signal. The external noise canceller digitally synthesizes a cancellation signal which dramatically improves the signal-to-noise ratio in the receiver. Together, the combined cancellation techniques prevent receiver saturation and preserve receiver sensitivity.