Circulator-Based Stand-Alone LNA for TDD Wireless Systems
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Solution Overview
Problem
Conventional Low Noise Amplifier (LNA) systems for Time Division Duplex (TDD) wireless systems require separate cables or additional control lines for switching between transmit and receive modes, leading to high costs, maintenance burdens, and difficulties in achieving low loss and standardized control interfaces, especially when supplied by different manufacturers.
Innovation Solution
The use of circulators in the LNA system eliminates the need for transmit/receive switches by providing a standalone solution with minimal attenuation during transmit bursts and gain during receive bursts, utilizing a limiter device to prevent signal leakage and operating independently of the base station, with a configuration that reduces loop gain and inband ripple through interconnection of circulators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a single feeder cable is used for both transmit and receive paths with a Tx/Rx switch, then the system cost and cable quantity are reduced, but the system requires additional control lines and signaling interfaces which increase device complexity and difficulty in standardization
Solution Approach 1:
The invention extracts the control signaling requirement from the system by using a stand-alone LNA that operates autonomously. The LNA automatically detects transmit/receive modes through its circulator architecture and switches internally without external control lines, eliminating the need for standardized control interfaces between different manufacturers' equipment.
Solution Approach 2:
The LNA system serves itself by using the inherent properties of circulators to automatically route signals based on the operational mode. The circulators' directional signal flow characteristics enable the LNA to self-detect whether it is in transmit or receive mode and self-switch the signal path without external intervention or control signaling.
2Quantity of substance
If a Tx/Rx switch is used to alternate between transmit and receive paths, then a single feeder cable can be shared, but the switch introduces signal loss and difficulty in achieving low loss performance
Solution Approach 1:
The invention replaces the mechanical/electronic Tx/Rx switch with a passive circulator-based routing system. Circulators use magnetic field effects to direct signal flow based on the direction of signal application, eliminating the need for active switching components that introduce insertion loss. The circulator provides isolation between transmit and receive paths while maintaining low loss in both directions.
3Loss of energy
If separate transmit and receive feeder cables are used, then transmit and receive paths have lower loss, but the system cost and maintenance burden increase
Solution Approach 1:
The invention merges the transmit and receive feeder cable functions into a single shared cable by using circulators to provide directional signal routing. The circulators enable the single cable to carry high-power transmit signals in one direction and low-power receive signals in the opposite direction without interference, achieving the functionality of separate cables with the simplicity of a single cable installation.
4Quantity of substance
If a Tx/Rx switch is used for signal path switching, then a single feeder can be used, but it is difficult to realize a switch that can switch at high power and with low loss
Solution Approach 1:
The invention replaces the active Tx/Rx switch with passive circulator components that use magnetic field-based signal routing. Circulators can handle high power levels inherently as they are passive magnetic devices without active components that would be damaged by high power. The circulator's directional coupling provides low-loss signal transfer in the forward direction while providing isolation in the reverse direction, achieving both high power handling and low loss simultaneously.
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 provides a cost-effective, reliable, and low-maintenance LNA system with minimal attenuation and gain during transmit and receive phases, respectively, while reducing inband ripple and Bit Error Rate (BER), operating independently of the base station without the need for standardized control interfaces.
Implementation Method 1
A first circulator has first, second and third ports. The first port is for connecting to a TX/RX feed to the transceiver system.
Implementation Method 2
The receive path comprises a limiter device and a low noise amplifier (LNA).
Data Source
AI summary
A time division duplex (TDD) wireless apparatus includes a low noise amplifier (LNA) system, at least one antenna and a transceiver system. The apparatus supports N time division duplexed channels which each have a transmit direction of transmission flow and a receive direction of transmission flow. The LNA system comprises N sub-units. Each sub-unit comprises a first circulator for connecting to a respective TX/RX feed to the transceiver system and a second circulator for connecting to the at least one antenna. The first circulator and second circulator within each sub-unit are interconnected to provide a path in one of the directions of transmission flow. The first circulator of each sub-unit is connected to the second circulator of another sub-unit to provide a path in the other direction of transmission flow. A single channel variant is also provided.