Variable Inductor/Capacitor TDD Front-End for LNA/PA Matching
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Solution Overview
Problem
Transceiver front-ends for time division duplexing (TDD) operation often incorporate complex circuitry to minimize signal loss, which can degrade the performance of low noise amplifiers (LNAs) and power amplifiers (PAs) due to impedance mismatching and current leakage.
Innovation Solution
Incorporation of a variable inductor and a variable capacitor in the receiver and transmitter branches, respectively, with a mode control switch and capacitance control switches to adjust impedance matching dynamically based on operation mode, minimizing noise factor and performance impact on LNAs and PAs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If complex circuitry is incorporated into the receiver branch and transmitter branch to minimize signal loss, then signal loss is reduced, but the noise factor of LNAs increases and performance of PAs degrades due to impedance mismatching and current leakage
Solution Approach 1:
The patent implements dynamic switching between different circuit configurations using switches (first switch, second switch, third switch) that change the connectivity of inductors and capacitors based on operating mode. This dynamic reconfiguration allows the circuit to optimize impedance matching for both receiving and transmitting modes, preventing signal loss while maintaining LNA and PA performance through adaptive impedance transformation.
Solution Approach 2:
The patent utilizes variable inductors and capacitors whose electrical parameters (inductance and capacitance values) can be changed based on operating conditions. These parameter changes enable the matching network to adapt to different impedance requirements in receiving versus transmitting modes, thereby minimizing signal loss without degrading amplifier performance through impedance mismatching.
2Strength
If multiple stacked transistors are incorporated into the switch to support a large voltage switch at the antenna, then voltage switching capability is improved, but device complexity increases
Solution Approach 1:
The patent divides the voltage switching function across multiple stacked transistors (first switch, second switch, third switch), where each transistor handles a portion of the voltage stress. This segmentation allows the circuit to support large voltage swings at the antenna while distributing the complexity across manageable discrete components rather than requiring a single complex high-voltage switch.
Solution Approach 2:
The patent introduces intermediate matching network components (inductors, capacitors, transformers) that mediate between the high-voltage antenna interface and the lower-voltage LNA/PA circuits. These intermediary elements transform impedances and voltages, allowing simple low-voltage switches to control high-voltage signals without directly exposing the switches to full voltage stress.
3Adaptability or versatility
If a complex matching network is incorporated between the I/O pad and the LNA for impedance matching, then impedance matching is improved, but signal loss increases and LNA performance degrades
Solution Approach 1:
The patent designs a universal matching network that serves multiple functions simultaneously: impedance matching for both receiving and transmitting modes, signal path switching, and protection of the LNA from high-voltage transmitters. This multi-functional approach eliminates the need for separate complex matching networks for each mode, reducing overall signal loss while maintaining adaptability across different operating conditions.
Solution Approach 2:
The patent ensures continuous impedance matching across mode transitions by maintaining connected inductors and capacitors that remain part of the signal path during both receiving and transmitting operations. This continuity avoids discontinuities and reflections that would occur with complete reconfiguration, thereby minimizing signal loss while maintaining adaptability through controlled switching of specific elements.
Data Source
AI summary
A transceiver front-end (FE) includes a receiver from an I/O pad to an amplifier (e.g., a low noise amplifier (LNA)) and a transmitter from the I/O pad to another amplifier (e.g., a power amplifier (PA)). The receiver further includes a variable inductor connected at one end to the I/O pad and connectable at the opposite end to ground by a switch. The LNA is connected to a node between portions of the inductor. When receiving, the switch is opened so the inductor exhibits low inductance for LNA impedance matching. When transmitting, the switch is closed so the inductor exhibits high inductance for blocking leakage to the LNA. Additionally, or alternatively, the transmitter includes a variable capacitor connected to the I/O pad. When receiving, the capacitor is programmed to exhibit low capacitance for optimal LNA performance. When transmitting, the capacitor is programmed to exhibit high capacitance for optimal PA performance.