Cosite Transmitter-Receiver Isolation via Complex Weight Beamforming
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Solution Overview
Problem
Cosite transmitter-receiver systems face challenges in isolating receiver antennas from strong signals emitted by nearby transmitters, leading to degraded receiver functionality due to signal coupling, which existing techniques such as increased separation, sidelobe reduction, and digital suppression filters do not adequately address.
Innovation Solution
The system employs complex weights to synthesize transmit signals, which are scaled and phase-shifted versions of a common waveform, allowing for improved isolation by minimizing power coupling into receive antennas through channel state information analysis and digital signal processing techniques, including repetition codes and beamforming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If transmit and receive antennas are located in close proximity, then system integration is improved, but signal coupling degrades receiver functionality
Solution Approach 1:
The patent segments the transmitted signal into multiple orthogonal components (e.g., different polarizations, time slots, or codes) that can be independently processed. By dividing the signal space, the receiver can separate desired signals from self-interference through orthogonal decomposition, enabling close antenna placement while maintaining signal integrity.
Solution Approach 2:
The patent introduces digital signal processing as an intermediary mechanism between the coupled transmit and receive antennas. Through adaptive filtering, channel estimation, and interference cancellation algorithms, the system mediates the harmful coupling effect and recovers the desired signal, allowing physical proximity without performance degradation.
2Object-affected harmful factors
If separation between transmit and receive antennas is increased, then isolation is improved, but system integration deteriorates
Solution Approach 1:
The patent replaces the mechanical solution of physical antenna separation with a digital signal processing approach. Instead of relying on spatial distance for isolation, the system uses orthogonal signal design, adaptive filtering, and interference cancellation algorithms to achieve isolation electronically, maintaining compact integration while achieving the required isolation performance.
3Object-affected harmful factors
If digital suppression filters are employed, then isolation is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary signal design techniques where transmit signals are pre-coded with orthogonal sequences or specific polarization states before transmission. This preliminary structuring of signals enables simpler receiver processing, as the orthogonality is already embedded in the transmitted signal, reducing the computational burden of suppression filters while maintaining effective isolation.
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 effectively reduces signal power at receive ports to near noise floor levels, enabling simultaneous operation of receivers with cosite transmitters and improving RF isolation across various frequency sub-bands.
Implementation Method 1
Beamforming is a technique used in multi-port transmitters to transmit signals with directional selectivity. Beamforming is accomplished by introducing phase differences between signals emitted or received by spatially-separated antenna elements. The phasing can occur at radio frequencies (RF), such as in analog arrays, or digitally, such as in digital beam forming systems. These phase differences cause the waves of energy which carry the signals to combine constructively and destructively differently along different angles of transmission.
Implementation Method 2
The system may be configured to use the channel state information to determine a second set of complex weights which will reduce the power received at one or more ports of the receiver when applied to a second plurality of transmit signals
Data Source
AI summary
Systems and methods for improving isolation between a cosite transmitter-receiver system. The transmitter may send a first plurality of transmit signals from multiple transmit ports. The first plurality of transmit signals may be related to one another by a first set of complex weights. The receiver may detect channel-impaired versions of the first plurality of transmit signals at one or more receive ports. The receiver may analyze channel-impaired versions of the first plurality of transmit signals to estimate channel state information. The transmitter may use the channel state information to determine a second set of complex weights which will reduce the power received at one or more ports of the receiver when applied to a second plurality of transmit signals. The second set of complex weights may vary with frequency.