RFID Transmitter Signal Suppression via Reflection Modulator
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Solution Overview
Problem
RFID writing/reading devices face challenges in achieving sufficient isolation between the transmitter and receiver, leading to unwanted spurious signals that reduce sensitivity and require high dynamic range and power consumption, especially in UHF and microwave bands for long-range operations.
Innovation Solution
A directional coupler is used at the antenna output to reflect a weighted copy of the transmitted signal back into the receiver, with a reflection modulator adjusting the amplitude and phase to subtract the spurious signal, and an auxiliary signal with a frequency offset is used for DC-voltage-free processing, allowing for immediate and effective suppression of the transmitted signal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a circulator or separate antennas are used to decouple transmitter and receiver, then isolation between transmitter and receiver is improved, but device complexity increases
Solution Approach 1:
The patent combines the functions of signal coupling, reflection, and modulation into a single directional coupler with integrated reflection modulator, eliminating the need for separate circulators or antenna systems while achieving the same isolation effect
Solution Approach 2:
The directional coupler serves multiple functions simultaneously: it couples the transmitted signal, reflects a weighted copy back into the receiver path, and the reflection modulator adjusts amplitude and phase to enable signal subtraction, creating a multi-functional component that reduces overall system complexity
2Length of moving object
If transmitted signal power is increased to achieve long-range reading, then reading distance is improved, but spurious signal injection into receiver increases
Solution Approach 1:
The system preemptively creates a weighted copy of the transmitted signal and reflects it back into the receiver path with adjusted amplitude and phase, so that this anti-signal subtracts from the spurious injection before it can cause intermodulation distortion, allowing high power transmission without receiver degradation
Solution Approach 2:
The patent converts the harmful spurious signal injection into a useful component by deliberately reflecting a weighted copy of the transmitted signal through the receiver path, which then serves as a reference for subtraction, transforming the harmful interference into a beneficial cancellation mechanism
3Measurement precision
If receiver sensitivity is increased to detect low-level response signals, then detection capability is improved, but susceptibility to transmitted signal interference increases
Solution Approach 1:
The system uses feedback by continuously monitoring the transmitted signal through the directional coupler and dynamically adjusting the reflection modulator to maintain optimal cancellation conditions, ensuring that the anti-signal continuously counteracts the spurious injection even as operating conditions change
4Reliability
If dynamic range of receiver is increased to handle both high-level transmitted signal and low-level response signal, then signal detection capability is improved, but power consumption increases
Solution Approach 1:
The patent extracts the harmful transmitted signal component from the receiver path through the directional coupler and reflection modulator combination, removing it before it can interact with the low-level response signals, thereby allowing the receiver to operate with reduced dynamic range requirements and lower power consumption
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 approach reduces noise and increases sensitivity to response signals from tags, enabling reliable detection and processing while reducing the dynamic range requirements and power consumption, and allows for immediate compensation of transmitted signal components.
Implementation Method 1
part of a transmitted signal is used in a directional coupler at the antenna output of an RFID writing/reading device such that a copy of the transmitted signal, the amplitude and phase of which copy have been weighted, is reflected into the input of a receiver
Implementation Method 2
The degree of reflection and the associated phase are set using a reflection modulator
Data Source
AI summary
A device for operating an RFID writing/reading device with transmitted signal suppression includes the RFID writing/reading device and a reflection modulator. The RFID writing/reading device includes a transmitter, a receiver with a signal processor, a directional coupler with a first, a second, a third and a fourth port, and an antenna. The reflection modulator is connected to the fourth port of the directional coupler. The reflection modulator includes a first setting element and a second setting element. The reflection modulator is configured to reflect a copy of a transmitted signal from the RFID writing/reading device, the amplitude and phase of which copy have been weighted, to the directional coupler. The directional coupler is configured to add the weighted copy of the transmitted signal to a received signal from the antenna in the directional coupler.