CMOS Transceiver Tx/Rx Port Sharing With a Single RF Choke
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Solution Overview
Problem
Conventional CMOS-based transceiver schemes require two inductors to share the Tx/Rx interface port, leading to excessive power loss and increased costs due to the need for special resistors to support high PA output power.
Innovation Solution
A technique using a single inductor with controllable switches to selectively share the RF choke between the LNA and PA, leveraging source-drain symmetry of MOS transistors to minimize power loss and eliminate the need for special resistors, allowing the same device to function as both LNA and PA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two inductors are used to share the Tx/Rx interface port, then the circuit can support both LNA and PA functions, but the power loss increases excessively
Solution Approach 1:
The patent merges the functions of two separate inductors (L1 for LNA bias and L2 for PA bias) into a single shared inductor. The inductor is configured to provide biasing for both the LNA and PA circuits, eliminating the need for separate inductors and reducing the total power loss that would occur with two separate LC tanks.
Solution Approach 2:
The single inductor is designed to serve multiple functions: it acts as the bias inductor for the LNA circuit and simultaneously serves as the bias inductor for the PA circuit. This multi-functional design allows the same component to support both transmit and receive operations without requiring separate dedicated inductors for each function.
2Power
If special resistors are used to support high PA output power, then the PA can achieve high output power, but the cost increases
Solution Approach 1:
The patent replaces expensive special resistors with standard, low-cost resistors. By using a single shared inductor and configuring the circuit appropriately, the design eliminates the need for costly special resistors while still supporting high PA output power requirements.
Solution Approach 2:
The patent changes the circuit configuration parameters to enable high power operation without special resistors. By adjusting the biasing scheme and utilizing the shared inductor effectively, the circuit achieves high PA output power using conventional, low-cost resistor components.
3Reliability
If two inductors are used for LNA and PA biasing, then each circuit can be optimized independently, but the device complexity increases
Solution Approach 1:
The patent combines two separate inductor components into a single shared inductor that serves both LNA and PA biasing functions. This reduction in component count simplifies the device while maintaining the ability to optimize both circuits through proper biasing configuration.
Data Source
AI summary
A circuit for sharing Tx/Rx ports of a CMOS based time multiplexed transceiver includes a Low Noise Amplifier (LNA) and a Power amplifier (PA), and deploys a single RF choke shared between the LNA and PA. The circuit selectively functions as a PA cascode or a LNA input device. In one form the circuit uses MOS transistors configured for use in one of Blue tooth, WLAN and TDMA applications, taking advantage of source-drain symmetry of the MOS transistors. The circuit may include a DC path and be used in WLAN applications, wherein the sharing of the single choke is enabled by one switch in the DC path. As described, the single RF choke is disposed outside of the LNA and the PA. The circuit supports high out powers and causes reduced signal loss due to just one LC tank as opposed to two LC tanks present in the prior art.