RFID Modulator Impedance Control via Capacitive Coupling
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Solution Overview
Problem
Existing RFID modulation methods are inefficient for both short and long distances, with ASK modulation limiting maximum distance due to energy consumption and PSK modulation failing at short distances due to decreased signal power.
Innovation Solution
A modulator that phase and/or amplitude modulates a received electromagnetic carrier signal using a rectifier circuit with a controllable switching device, which intervenes in the rectifier stages to change the input impedance, allowing efficient modulation without affecting parasitic properties and enabling reliable communication across varying distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If ASK modulation is used by connecting and disconnecting an ohmic load, then amplitude modulation is achieved, but the maximum transmission distance is significantly reduced due to energy consumption
Solution Approach 1:
The patent introduces a capacitor as an intermediary element connected to the switching device. This capacitor absorbs and releases energy during the modulation process, acting as a buffer that prevents direct energy depletion from the power supply. The switching device alternately connects and disconnects the capacitor, enabling amplitude modulation while the capacitor maintains voltage stability and reduces overall energy consumption.
Solution Approach 2:
The patent changes the electrical parameters by introducing a capacitor with specific capacitance value into the modulation circuit. This parameter change allows the system to store and release energy in a controlled manner, transforming the modulation mechanism from direct power supply depletion to capacitor-based energy exchange, thereby improving power efficiency while maintaining modulation capability.
2Use of energy by moving object
If PSK modulation is used by changing the capacitance of a capacitor, then phase modulation is achieved with higher efficiency, but the reflected signal power decreases at very short distances
Solution Approach 1:
The patent employs a dynamically switchable capacitor configuration where the capacitance value can be changed during operation. The switching device can connect the capacitor in different configurations (series, parallel, or disconnected) based on the required modulation type and operating conditions. This dynamic adaptability allows the system to optimize between PSK efficiency and signal power output depending on the transmission distance and requirements.
Solution Approach 2:
The modulation circuit is designed with multi-functionality to support both ASK and PSK modulation modes using the same capacitor and switching device. By universally applying the capacitor-based approach, the system can switch between amplitude modulation (when capacitor is disconnected) and phase modulation (when capacitor is connected), providing versatile operation across different distance scenarios without requiring separate dedicated circuits.
3Productivity
If a switching device intervenes in the rectifier circuit, then efficient modulation is achieved, but parasitic properties affect the modulation performance
Solution Approach 1:
The patent creates an isolated modulation environment by using a capacitor that is electrically coupled to the rectifier circuit through a transformer or optocoupler. This copying approach allows the switching device to control the capacitor's charging and discharging without directly interfering with the high-voltage rectifier circuit. The capacitor replicates the modulation effect while being electrically isolated, thereby eliminating parasitic effects from the switching device on the rectifier's performance.
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 efficient and reliable modulation for both ASK and PSK, maintaining high efficiency and signal strength across a wide range of distances, especially in the near and far field regions, by minimizing the impact of switching processes on the rectifier's output voltage and using a capacitive coupling to the antenna input.
Implementation Method 1
a rectifier circuit for rectifying a received electromagnetic carrier signal having at least one rectifier stage with at least one circuit node
Implementation Method 2
the circuit node is connected by a capacitive coupling to an input of the rectifier circuit
Implementation Method 3
the electromagnetic carrier signals are modulated by the transponder with a customary modulation method as a function of the data to be transmitted to the base station and are reflected. In general, this is accomplished by a change in the input impedance of the transponder's transmitting and receiving device
Data Source
AI summary
In certain embodiments, an apparatus includes a rectifier and a switch. The rectifier is configured to modulate a received carrier signal. The switch is coupled to at least one node of the rectifier. The switch is configured to modify an impedance of the rectifier to modulate the received carrier signal by providing a potential to the at least one node of the rectifier based on a field strength of the received carrier signal and a modulation-control signal.