Backscatter Modulator Voltage Regulation Loop for RFID
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Solution Overview
Problem
Current RFID transponder designs face challenges with reduced antenna voltage due to deep sub-micron processes, limiting the operating voltage range and making traditional backscatter modulation methods unsuitable, as they induce additional voltage drops and are not compatible with the lower voltage thresholds of modern transponders.
Innovation Solution
A backscatter modulation circuit with a voltage regulation loop, including a rectifier, error amplifier, and switch, that maintains antenna voltage within a predetermined range by varying a regulated load based on a data stream, allowing precise modulation depth control independently of field strength, even at low voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional resistive load switching method is used for backscatter modulation, then modulation can be achieved in high voltage ranges, but additional voltage drops are induced and supply voltage falls out of the limited range in deep sub-micron processes
Solution Approach 1:
The patent implements a voltage regulation loop that continuously monitors the local voltage rail and adjusts the regulated load accordingly. The error amplifier compares the actual voltage with a reference and controls the regulated load to maintain voltage within the predetermined range, eliminating the voltage drop issues of traditional methods
Solution Approach 2:
The invention changes the modulation approach by using a regulated load with variable impedance controlled by the voltage regulation loop, rather than simple resistive switching. This allows dynamic adjustment of the load parameter to maintain optimal voltage levels while achieving backscatter modulation
2Reliability
If antenna voltage is limited to 3V or below due to reduced voltage resistivity, then device damage is avoided, but operating voltage range is reduced
Solution Approach 1:
The patent segments the voltage regulation function into a dedicated voltage regulation loop separate from the antenna interface. This allows independent control of antenna voltage within the safe 3V limit while maintaining adequate supply voltage for the analog front end and digital circuits through the regulated local voltage rail
Solution Approach 2:
The invention introduces a regulated load as an intermediary between the antenna and the power supply circuitry. This regulated load acts as a buffer that maintains the local voltage rail within the required range while the antenna voltage remains limited to safe levels, effectively decoupling the voltage constraints
3Reliability
If rectifier voltage drop is combined with 3V limiter threshold, then supply voltage is reduced to 2.5V, but former designs operated at 6V
Solution Approach 1:
The patent changes the supply voltage parameter dynamically through the voltage regulation loop. By adjusting the regulated load based on the detected antenna voltage and rectifier output, the system maintains supply voltage at adequate levels (above 2.5V) even when antenna voltage is limited to 3V, effectively compensating for the rectifier voltage drop
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
Enables precise and constant backscatter modulation at reduced antenna limiter thresholds, maintaining voltage regulation and extending the operating range of RFID transponders, making it compatible with deep sub-micron processes and low voltage environments.
Implementation Method 1
a rectifier connected between the antenna and the local voltage rail for rectifying a voltage from the antenna
Implementation Method 2
modulation circuitry for back scatter modulation at a local voltage rail connected to the antenna
Data Source
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AI summary
An RFID transponder includes an antenna and modulation circuitry for back scatter modulation at an local voltage rail connected to the antenna such that a voltage of the antenna is maintained within a predetermined range. The modulation circuitry includes a voltage regulation loop including a rectifier connected between the antenna and the local voltage rail (Vlocal) for rectifying a voltage from the antenna so as to load the local voltage rail (Vlocal) with the rectified voltage from the antenna, an error amplifier (A1) for comparing a voltage at the local voltage rail (Vlocal) with a modulation voltage (Vmod) and producing an output signal (Vout), means for switching the modulation voltage (Vmod) between a first reference voltage level (Vref) and a second reference voltage level, wherein a regulated load is coupled between the output of the error amplifier (A1) and the antenna, which is varied in response to the output signal (Vout).