ASK Inductive Link Circuit for Fast RF Pulse Decay
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Solution Overview
Problem
In inductive links for implanted electronic systems, the power transfer efficiency and data pulse decay rates are conflicting requirements, with high unloaded quality factors enhancing power transfer during RF-ON but causing slow decay during RF-OFF, making data detection challenging.
Innovation Solution
A series-tuned resonant transmitting circuit with a damping resistor is used to reduce the quality factor during RF-OFF, accelerating the decay of RF amplitude and minimizing state transition times, while a class D amplifier driver integrated on a microchip facilitates efficient data transfer using Amplitude Shift Keying (ASK).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high unloaded quality factor is used in the resonant circuit, then power transfer efficiency is improved, but RF pulse decay time increases
Solution Approach 1:
The patent applies dynamics by making the quality factor of the resonant circuit time-variable rather than fixed. During the RF-ON period, the circuit maintains a high quality factor for efficient power transfer. During the RF-OFF period, the quality factor is reduced to accelerate RF pulse decay. This dynamic adjustment of circuit parameters resolves the contradiction between maintaining high power transfer efficiency and achieving fast pulse decay.
Solution Approach 2:
The patent changes the physical parameter of the resonant circuit (quality factor) based on the operational state. By switching between different quality factor values corresponding to RF-ON and RF-OFF states, the system optimizes both power transfer efficiency during transmission and pulse decay speed during idle periods, thereby resolving the technical contradiction.
2Power
If high unloaded quality factor is used in the resonant circuit, then power transfer during RF-ON is enhanced, but state transition time increases
Solution Approach 1:
The patent uses dynamic quality factor adjustment to optimize state transitions. When transitioning from RF-ON to RF-OFF, the quality factor is reduced to accelerate the decay of residual RF energy, thereby reducing the time required for the system to reach the idle state. This dynamic parameter change enables fast state transitions while maintaining high power transfer during the active state.
Solution Approach 2:
The system employs periodic switching between high and low quality factor states synchronized with the RF-ON and RF-OFF periods. This periodic adjustment ensures that the resonant circuit operates at optimal efficiency during power transfer phases while rapidly settling during idle phases, minimizing overall state transition time.
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 enables rapid decay of RF pulses to baseline, improving data decoding accuracy and insensitivity to coupling factors, thus enhancing data transfer efficiency and reducing power consumption in implanted systems.
Implementation Method 1
An inductive link basically has two resonant circuits: an external one and an internal one implanted in the patient user. The inductances of the two resonant circuits are realized, for example, as two spiral-shaped coils with typical outer diameters between 20 and 30 mm. When facing each other, the coils form a transformer which allows the transfer of RF-energy.
Implementation Method 2
A series-tuned resonant transmitter circuit with a damping resistor (RD) is used to reduce the transmitter quality factor during RF-OFF, accelerating the decay of RF amplitude
Data Source
AI summary
A rf signal transfer link is described which uses amplitude shift keying (ASK) to transfer rf data pulses. The link minimizes state transition time at the end of each data pulse.