Analysis of Signal Transmission through Time-Varying Inductively Coupled Links

Resonance in inductively coupled links improves the gain but reduces the bandwidth and data rate. One of the techniques for increasing the data rate that can be transmitted through a resonant link is to reset the state variables on both the primary and secondary sides of the inductively coupled link after each symbol. This removes inter-symbol interference but reduces the received signal amplitude. Another technique, specific to frequency-shift keying (FSK), is to modulate the resonance frequency of the primary side in accordance with the transmitted frequency. This preserves the signal amplitude but can be applied only on the primary side. This paper compares the performance of these techniques. It is shown that the received signal amplitude is twice as much in resonance-frequency modulation compared to state-variable reset. A new technique combining both these approaches is proposed, and it outperforms all other techniques at high quality factors.