Switch-Protected LNA Input Network for Bandwidth and Leakage Protection
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Solution Overview
Problem
Existing RF communication systems face challenges in protecting low noise amplifiers (LNAs) from damage due to transmit signal leakage and reflections, which can degrade performance and reduce bandwidth.
Innovation Solution
Implementing a switch protected LNA with a first input inductor, a second input inductor, an inductor bypass switch, and a shunt protection switch, where the inductor bypass switch is turned on in receive mode and the shunt protection switch is turned on in transmit mode to provide additional inductance for improved transmit mode bandwidth and bypassed in receive mode for low insertion loss and improved noise figure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protection switch is included at the input of an LNA to protect from transmit signal leakage and reflections, then the LNA is protected from damage, but the bandwidth is reduced
Solution Approach 1:
The patent applies dynamics by making the inductor configuration changeable through switches. The first and second input inductors are connected in series during transmit mode to provide protection and appropriate impedance, while they can be reconfigured during receive mode to maintain wide bandwidth. This dynamic reconfiguration resolves the contradiction between protection and bandwidth by adapting the circuit topology to different operational modes.
2Length of moving object
If additional inductance is provided to improve transmit mode bandwidth, then transmit mode bandwidth is improved, but insertion loss increases and noise figure degrades in receive mode
Solution Approach 1:
The patent uses dynamic switching to change the inductor configuration based on operational mode. During transmit mode, the first and second input inductors are connected in series to provide additional inductance for improved bandwidth. During receive mode, the switches reconfigure the circuit to bypass or reduce the inductance impact, thereby minimizing insertion loss and maintaining good noise figure performance. This dynamic adaptation resolves the contradiction between transmit bandwidth improvement and receive mode loss.
3Length of moving object
If additional inductance is provided to improve transmit mode bandwidth, then transmit mode bandwidth is improved, but noise figure degrades in receive mode
Solution Approach 1:
The patent implements dynamic reconfiguration of the inductor network using switches. In transmit mode, the first and second input inductors are connected in series to enhance bandwidth. In receive mode, the switches change the topology to minimize the impact of inductors on the noise figure, ensuring that the LNA operates with low noise performance. This dynamic switching resolves the contradiction between transmit bandwidth and receive noise figure by optimizing the circuit configuration for each operational mode.
Data Source
AI summary
Switch protected low noise amplifiers (LNAs) are disclosed herein. In certain embodiments, a switch protected LNA includes an antenna terminal for receiving a radio frequency (RF) signal, an LNA for amplifying the RF signal, a first input inductor, a second input inductor, an inductor bypass switch connected in parallel to the second input inductor, and a shunt protection switch. The first input inductor is electrically connected between the antenna terminal and the second input inductor, while the second input inductor is electrically connected between the first input inductor and the shunt protection switch. The inductor bypass switch is turned on and the shunt protection switch is turned off in a receive mode, while the inductor bypass switch is turned off and the shunt protection switch is turned on in a transmit mode.