RF Phase Shifter Circuit for Transmit-Receive Crosstalk Cancellation
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Solution Overview
Problem
High-frequency communication units, particularly in mono-static radar systems, face significant interference due to poor signal isolation between transmit and receive paths, leading to degraded performance and increased complexity and cost, with existing phase compensation techniques being impractical at high frequencies.
Innovation Solution
The implementation of an electrically adjustable phase shifter using active devices and varactors allows for dynamic phase compensation of RF signals, enabling improved signal-to-noise ratio (SNR) by cascading phase adjustment circuits and using real-time feedback to adjust phase and gain, thereby reducing cross-talk interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high-end circulators or rat-race couplers are used to reduce interference effects, then isolation between transmit and receive paths is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts and removes the harmful transmit signal from the receive path by generating a cancel signal that is subtracted from the received signal. This eliminates the need for complex isolation components like circulators and rat-race couplers, directly addressing the contradiction by removing harmful interference without adding system complexity.
Solution Approach 2:
The patent converts the harmful transmit signal leakage into a useful cancel signal by capturing a portion of the transmit signal, processing it through phase and amplitude adjustment, and subtracting it from the receive path. This transforms the harmful interference into a beneficial cancellation mechanism, improving isolation without requiring complex passive components.
2Object-affected harmful factors
If ultra short transmit pulses are used to guarantee transmitter shut-down, then isolation during receive operation is improved, but productivity and system performance degrade
Solution Approach 1:
The patent implements dynamic phase and amplitude adjustment of the cancel signal to adapt to changing operating conditions. This allows continuous transmit-receive operation without requiring ultra-short pulses, maintaining both interference rejection and system productivity through real-time signal processing rather than time-gated operation.
3Object-affected harmful factors
If spatially-separated antennas are used for transmit and receive operation, then isolation between paths is improved, but device complexity and space requirements increase
Solution Approach 1:
The patent merges the transmit and receive antenna functions into a single antenna system, using signal processing rather than spatial separation to achieve isolation. By combining the antenna functions and using electronic cancel signal subtraction, the system achieves interference rejection without requiring separate transmit and receive antenna elements, reducing space requirements.
4Reliability
If phase compensation techniques are implemented at high frequencies, then signal-to-noise ratio is improved, but ease of manufacture and implementation become impractical
Solution Approach 1:
The patent replaces mechanical or hardware-based phase compensation techniques with electronic signal processing. By using electronic phase and amplitude adjustment circuits rather than mechanical phase shifters or complex hardware compensation networks, the system achieves high-frequency phase compensation that is both effective and manufacturable with standard electronic components.
Data Source
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AI summary
An integrated circuit for phase shifting a radio frequency signal, wherein the integrated circuit comprises at least one phase shifter (300) comprising: at least one input for receiving a radio frequency signal, a voltage variable element (315); and a plurality of active devices (305, 310) operably coupled to the voltage variable element (315) and arranged to receive a variable control voltage (435, 440). The plurality of active devices (305, 310) comprise at least two active devices coupled in a common base arrangement and arranged to receive the radio frequency signal with the voltage variable element (315) coupling the emitter contacts or source contacts of the at least two active devices, such that a variable control voltage applied to the voltage variable element adjusts a phase of the radio frequency signal.