RFID Interrogator Automatic Gain Control Timing
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Solution Overview
Problem
RFID reader/writers face challenges in precisely determining the timing of received reflected radio waves from RFID tags due to significant wave short-cutting from the transmission subsystem to the reception subsystem, making it difficult to implement Automatic Gain Control (AGC) effectively in backscatter systems.
Innovation Solution
An RFID interrogator device with a transmission section, a reception section having a variable gain amplifying function, and an automatic gain control section that measures the amplitude of the reception signal after a predetermined time to adjust the gain of the received RF signal to a desired level, ensuring appropriate amplitude modification for optimal communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the RFID reader/writer simultaneously transmits continuous wave and receives reflected wave from RFID tag, then backscatter radio-communications can be conducted, but radio wave short-cutting from transmission subsystem to reception subsystem occurs making it difficult to precisely determine reception timing
Solution Approach 1:
The patent applies preliminary action by measuring the reception signal amplitude in advance (within a predetermined time period after transmission completion) before the actual communication begins. This advance measurement allows the system to determine the correct reception timing and adjust gain accordingly, avoiding the short-cutting problem that would occur if timing was determined after the fact during simultaneous operation.
Solution Approach 2:
The patent segments the reception process into distinct phases: a measurement phase where the reception signal amplitude is measured within a predetermined time after transmission, and a communication phase where actual backscatter communication occurs. This temporal segmentation allows the system to accurately determine reception timing parameters without interference from the transmission signal, resolving the timing detection accuracy problem.
2Reliability
If Automatic Gain Control is implemented to maintain constant received power, then signal reception quality improves, but the system complexity increases due to additional control circuits
Solution Approach 1:
The patent implements self-service by using the received signal itself to control the gain adjustment. The reception signal amplitude measurement directly feeds back to the gain control mechanism, allowing the system to automatically adapt to signal strength variations without requiring external intervention or complex control algorithms. This simplifies the control circuitry while maintaining reliable signal reception.
Solution Approach 2:
The patent employs feedback by measuring the reception signal amplitude and using this information to adjust the gain of the reception amplifier. This closed-loop feedback mechanism ensures that the received power remains within the optimal range for processing, improving signal reception quality while using a relatively simple implementation that doesn't significantly increase system complexity.
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 enables suitable automatic gain control for RFID communications, improving the precision of signal reception and maintaining a stable gain level, even with weak signal power from RFID tags, thereby enhancing communication efficiency.
Implementation Method 1
passive type RFID tags have no its power source... RFID tag converts the received continuous wave to DC power as its power source
Implementation Method 2
the RFID tag alternately carries out reflection and absorption of the received continuous wave by varying impedance of its antenna in response to information to be transmitted
Data Source
AI summary
RFID interrogator device carries out an automatic gain control when an RF signal from RFID tag with a backscatter radio-communication is received. To carry out the automatic gain control, amplitude of the reception signal is measured within a prescribed time corresponding to a length of preamble added to the head of data of the RF signal. An AGC value is determined based on the measured amplitude value.