Switch-less RF Transceiver LC Resonance Isolation
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Solution Overview
Problem
Conventional RF transceivers require a transmit/receive switch that increases size, cost, power consumption, and insertion loss, particularly at higher frequencies, and is undesirable for switchless operation.
Innovation Solution
The implementation of an interference cancellation circuit using LC resonant circuits to provide high impedance and act as a switchless TX/RX selector, allowing for low-impedance paths during receive and high-impedance paths during transmit operations, eliminating the need for a physical switch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transmit/receive switch is used in the transceiver, then the transmitter and receiver can be properly isolated during operation, but the insertion loss increases and receiver sensitivity decreases
Solution Approach 1:
The patent removes the transmit/receive switch from the signal path entirely, extracting the problematic switching component that caused insertion loss. Instead of using a physical switch to isolate the transmitter and receiver, the design relies on the inherent high impedance of the transmitter output and the use of interference cancellation circuits to prevent transmitter leakage from reaching the receiver, thereby eliminating switch-related insertion loss while maintaining proper isolation.
Solution Approach 2:
The patent introduces interference cancellation circuits as intermediary components that actively cancel out leakage signals from the transmitter before they can reach the receiver. These circuits use pilot tones and adaptive filtering to create canceling signals that neutralize the harmful leakage, serving as a mediator that achieves isolation without requiring a physical switch in the signal path.
2Volume of moving object
If a transmit/receive switch is integrated on-chip, then the device size is reduced, but insertion loss is still significant at high frequencies
Solution Approach 1:
The patent replaces the mechanical/electrical switching system with an electronic interference cancellation system. Instead of using a physical switch (mechanical or electronic transistor switch) to isolate TX and RX paths, the invention uses electronic signal processing techniques including pilot tone injection, adaptive filtering, and phase cancellation to achieve isolation electronically, thereby eliminating the insertion loss associated with physical switches while maintaining compact on-chip integration.
Solution Approach 2:
The patent changes the operating parameters and signal characteristics by introducing pilot tones at specific frequencies and using adaptive algorithms to dynamically adjust cancellation parameters. By modifying the signal domain parameters (frequency, phase, amplitude) rather than relying on physical switch states, the system achieves isolation without the insertion loss penalties of traditional switching mechanisms, even at high frequencies.
3Device complexity
If a transmit/receive switch is removed for switchless operation, then size and cost are reduced, but the transmitter output may damage the receiver input
Solution Approach 1:
The patent applies preliminary anti-action by proactively canceling out potential harmful transmitter leakage signals before they can reach and damage the receiver input. The interference cancellation circuits continuously monitor and cancel leakage paths using pilot tones and adaptive filtering, preventing the harmful effect from occurring in the first place rather than relying on a switch to block it after the fact.
Solution Approach 2:
The patent implements feedback mechanisms where the system continuously monitors the transmitter output and receiver input conditions, using this feedback information to dynamically adjust the interference cancellation parameters. The adaptive filtering algorithms use feedback from the received signal to optimize the cancellation of transmitter leakage, ensuring that harmful currents are neutralized in real-time without requiring a physical switch.
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
This solution reduces size, cost, and power consumption while minimizing insertion loss, enabling efficient high-frequency operation without a mechanical switch, achieving comparable performance to traditional switch-based transceivers.
Implementation Method 1
interference cancellation circuit using LC resonant circuits to provide high impedance
Data Source
AI summary
A switch-less transceiver has parallel LC resonances that act as OFF switches and series LC resonances act as ON switches when resonating at the transmit (TX) or receive (RX) frequency. When the transmitter is disabled, no current flows through series LC filters. Instead, series impedances to ground provide an RF ground to the transmitter output node. A TX inductor between the transmitter output node and the antenna is in parallel with a TX blocking capacitor to ground, which together form a parallel resonance to ground that has a high impedance when resonating at the receiver frequency. This high impedance acts as an OFF switch to block antenna signals from entering the transmitter. The two paths are in parallel, presenting a high impedance to the antenna and forming an OFF switch when the receiver is disabled.