Synchronously tuned patch for transmitting FSK

The gain-bandwidth product of a conventional antenna is limited by its electrical size. Synchronous antenna tuning circumvents the limited bandwidth of a time-invariant resonant antenna by modifying the impedance match of the antenna in synchrony with the communications signal. This paper extends an investigation of tuning a VLF antenna in synchrony with a frequency shift keyed (FSK) signal to higher frequencies using varactor diodes rather than mechanical tuning.