STAR Antenna T/R Coupler Layout for Active Self-Interference Cancellation
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Solution Overview
Problem
Simultaneous transmit and receive (STAR) systems face challenges due to transmitter signal coupling back and compressing the receiver's dynamic range, leading to issues like intermodulation distortion, gain compression, and increased noise figure, especially in array architectures with high power antennas.
Innovation Solution
The implementation of a switch at the end of the transmit chain and a directional coupler in the receive chain, combined with active cancellation signals generated based on the antenna array's coupling matrix, to cancel out coupled TX waveforms before they reach the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If transmit and receive channels operate at the same frequency to optimize bandwidth utilization, then spectrum efficiency is improved, but self-interference from transmit signal coupling into receive channel worsens
Solution Approach 1:
The system applies preliminary anti-action by generating an active cancellation signal that is the inverse of the expected coupled transmit signal. This cancellation signal is injected into the receive channel before the harmful coupling occurs, pre-neutralizing the self-interference effect and enabling simultaneous transmit and receive operation at the same frequency
Solution Approach 2:
The system converts the harmful transmit signal coupling into a beneficial effect by using the known transmit signal characteristics to generate a precise cancellation signal. The harmful coupling effect is predicted and counteracted, transforming the problem of self-interference into a controlled cancellation process that enables full-duplex operation
2Object-affected harmful factors
If isolation elements are added to prevent transmit signal coupling into receive channel, then self-interference is reduced, but device complexity increases
Solution Approach 1:
The system extracts and separates the cancellation signal generation function from the main transmit and receive paths. By using a dedicated cancellation signal generator that operates independently and injects the cancellation signal at a specific point in the receive channel, the system reduces complexity compared to full duplex isolation architectures while effectively mitigating self-interference
3Power
If high power array antennas are used to increase transmit power, then transmission range is improved, but transmit-to-receive coupling increases
Solution Approach 1:
The system applies feedback by continuously monitoring the transmit signal characteristics and using this information to generate an updated cancellation signal. The cancellation signal is dynamically adjusted based on the actual transmit power and coupling conditions, ensuring effective interference mitigation even when high power array antennas are used to increase transmission range
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 approach maintains the receiver's dynamic range and sensitivity by actively canceling mutual coupling effects, enabling STAR operation without the need for post-processing, thus optimizing system performance.
Implementation Method 1
providing an active cancellation signal to cancel at least some mutual coupling effects that arise on an input to the receive channel
Data Source
AI summary
A simultaneous transmit and receive (STAR) system comprises a plurality of radiating elements and a plurality of antenna transmit/receive (T/R) elements. The plurality of antenna T/R elements are each in operable communication with a respective radiating element. Each T/R element comprises a transmit channel, a receive channel, a switch, and a directional coupler. The directional coupler comprises an RF input in operable communication with an antenna array receiving signals, an RF output coupling the received signals to an input of the receive channel, and a coupled input operably coupled to the switch. If the switch is set to a predetermined state, the respective transmit channel couples an active cancellation signal to the coupled input of the directional coupler to cancel at least some coupling effects arising on an input to the receive channel, arising from operation of at least some of the T/R elements in the array.