Duplexer Phase-Shift Circuit for RF Isolation in Tx/Rx Modules
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Solution Overview
Problem
Existing transmission/reception modules in multimode wireless systems face issues with signal isolation, where transmission signal components may not be sufficiently attenuated, leading to degraded isolation characteristics due to impedance mismatch at the input node of the low-noise amplifier.
Innovation Solution
Incorporating a duplexer with a common node, transmission node, and reception node, along with a phase-shift circuit between the duplexer's reception node and the low-noise amplifier's input node, to adjust impedance and ensure the gain of the transmission signal is smaller than the reception signal, thereby improving isolation characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high pass filter and band pass filter are used in the transmission/reception module, then signal filtering is achieved, but transmission signal components may pass through without sufficient attenuation leading to degraded isolation characteristics
Solution Approach 1:
A phase-shift circuit is introduced as an intermediary component between the band pass filter and the low-noise amplifier. This circuit includes a series capacitor and a shunt inductor that work together to adjust the impedance at the low-noise amplifier input, thereby reducing transmission signal leakage without affecting the reception signal path
Solution Approach 2:
The impedance parameters of the low-noise amplifier input are modified by adding the phase-shift circuit. By carefully selecting the capacitor and inductor values, the input impedance is changed to create a mismatch for transmission signals (reducing their gain) while maintaining proper matching for reception signals
2Reliability
If the impedance at the input node of the low-noise amplifier is not adjusted, then the circuit configuration is simple, but the gain of the transmission signal may exceed the gain of the reception signal
Solution Approach 1:
A phase-shift circuit is introduced as an intermediary component between the band pass filter and the low-noise amplifier. This circuit includes a series capacitor and a shunt inductor that work together to adjust the impedance at the low-noise amplifier input, thereby reducing transmission signal leakage without affecting the reception signal path
Solution Approach 2:
The impedance parameters of the low-noise amplifier input are modified by adding the phase-shift circuit. By carefully selecting the capacitor and inductor values, the input impedance is changed to create a mismatch for transmission signals (reducing their gain) while maintaining proper matching for reception signals
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
The solution effectively reduces the gain of the transmission signal while maintaining high gain for the reception signal, thereby enhancing the isolation characteristics of the transmission/reception module, as confirmed by simulation results.
Implementation Method 1
a phase-shift circuit that is provided between an input node of the low-noise amplifier and the reception node of the duplexer, and that adjusts an impedance at the input node of the low-noise amplifier with respect to the transmission signal and the reception signal
Data Source
AI summary
Provided is a transmission/reception module that includes: a power amplifier that outputs a transmission signal to an input/output terminal; a low-noise amplifier that amplifies a reception signal input from the input/output terminal; a duplexer that isolates the transmission signal, which is output to the input/output terminal from the power amplifier via a transmission node and a common node, and the reception signal, which is input to the low-noise amplifier from the input/output terminal via the common node and a reception node, from each other; and a phase-shift circuit that is provided between an input node of the low-noise amplifier and the reception node of the duplexer, and that adjusts an impedance at the input node of the low-noise amplifier with respect to the transmission signal and the reception signal such that the gain of the transmission signal is smaller than the gain of the reception signal.