Notch Circuit in Power Amplifier Modules for Tx-Rx Self-Interference
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Solution Overview
Problem
In transceivers, the close spacing of transmit and receive bands leads to self-interference, degrading reception quality due to the overlap of transmission signals with the receiver band, especially in limited frequency band scenarios where frequency separation is narrow, making it difficult to eliminate this interference.
Innovation Solution
A notch circuit and power amplifier module that includes an inductor and capacitor connected to a power amplifier, which receives a supply voltage that varies with the input transmission signal, attenuating the output transmission signal when its frequency corresponds to a stopband where self-interference is likely, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the center frequencies of transmit and receive bands are separated to reduce self-interference, then the self-interference is reduced, but the available frequency band resources are limited and frequency separation becomes difficult
Solution Approach 1:
The patent extracts and removes the harmful frequency components from the transmit signal that would otherwise interfere with the receive band. The notch circuit selectively extracts and eliminates the specific frequency components causing self-interference, allowing the transmit and receive bands to operate closer together without degradation of reception quality.
Solution Approach 2:
The notch circuit acts as an intermediary component between the power amplifier and the antenna. It mediates the transmit signal by introducing a frequency-dependent attenuation characteristic that selectively reduces the harmful frequency components while preserving the useful transmission signal, thereby enabling better coexistence between transmit and receive operations.
2Object-affected harmful factors
If a notch circuit is added to attenuate self-interference frequencies, then self-interference is reduced, but the device complexity increases
Solution Approach 1:
The patent changes the electrical parameters of existing components (inductor and capacitor values) to create the desired notch filter characteristics. By carefully selecting and adjusting these parameters, the circuit achieves selective frequency attenuation without requiring complex active components or multiple stages, thereby limiting the increase in device complexity.
3Use of energy by moving object
If the amplitude of supply voltage varies with input transmission signal to improve power efficiency, then power efficiency is improved, but self-interference is exacerbated
Solution Approach 1:
The patent converts the harmful effect of amplitude-modulated supply voltage (which exacerbates self-interference) into a beneficial outcome by using the same modulation technique in the notch circuit. The notch circuit's attenuation characteristic is modulated at the same frequency as the supply voltage, creating a dynamic filter that selectively reduces self-interference while preserving power efficiency benefits.
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 notch circuit effectively decreases self-interference by attenuating the output transmission signal in frequencies where overlap occurs, improving reception quality without significant power loss, especially in low frequency bands where interference is most severe.
Implementation Method 1
The inductor is electrically connected to the first power amplifier. The inductor receives a first supply voltage (Vpa). An amplitude of the first supply voltage (Vpa) varies with the first input transmission signal (Tx In). The capacitor is electrically connected to the inductor. When a modulated frequency of the first supply voltage (Vpa) is corresponding to a stopband, the first output transmission signal (Tx out1) is attenuated.
Implementation Method 2
The notch circuit includes an inductor and a capacitor. The inductor is electrically connected to the first power amplifier. The capacitor is electrically connected to the inductor. When a modulated frequency of the first supply voltage (Vpa) is corresponding to a stopband, the first output transmission signal (Tx out1) is attenuated.
Data Source
AI summary
A notch circuit and a power amplifier module capable of reducing self-interference in a transceiver are provided. The transceiver includes a transmitter and a receiver, and the transmitter causes self-interference to the receiver. The transmitter includes a power amplifier module and the power amplifier module includes a notch circuit and a power amplifier. The notch circuit includes an inductor and a capacitor. The power amplifier amplifies an input transmission signal to generate an output transmission signal. The inductor receives a supply voltage. An amplitude of the supply voltage varies with the first input transmission signal. The capacitor is electrically connected to the inductor. The first output transmission signal (Tx_out1) is attenuated when a modulated frequency of the supply voltage is corresponding to a stopband.