A sub-GHz UWB pulse generator for wireless implantable medical devices

The design of a MOS-only pulse generator for sub-GHz Ultra-Wideband (UWB) biomedical communication is presented. The oscillator based pulse generator is capable of generating Binary Phase Shift Keying (BPSK) modulated pulses and is tunable in both frequency and output power. A varactor biasing circuit is developed that keeps the varactor bias voltage constant during oscillator startup and shutdown. The pulse occupies a bandwidth of 550 MHz. The center frequency can be controlled from 0.53 to 1.05 GHz and the digital gain control offers a 13.5 dB tuning range. For a 2.5 V supply and 1 MHz Pulse Repetition Frequency (PRF), the average power consumption ranges from 30 μW to 150 μW, depending on the pulse power controlled by the digital gain. The circuit performance is very robust over process corners, device mismatch and antenna reactance variations.