Implementation of Ultra-Wideband (UWB) Sensor Nodes for WBAN Applications - Ultra-Wideband and 60 GHz Communications for Biomedical Applications - page 113

Fig. 7 Delay-based impulse radio ultra-wideband (IR-UWB) pulse generation
where t p the propagation delay is caused by the buffer, C L is the load capacitance,
V DD is the supply voltage of the buffer, k 1 and k 2 are the gain factors. This narrow
pulse generation technique is shown in Fig. 7 . Two identical buffers are fed with a
resistor set oscillator that generates square pulses. Linear Technology's LT6905 pro-
grammable oscillator that generates a variable output frequency from 17 to 170 MHz
is used as the reference square pulse generator in this design. Fairchild semiconduc-
tor's NC7WZ126 ultra high-speed buffer and NC7SZ86 XOR gate are chosen in
this pulse generation mechanism because of their low rise and fall time operations.
Identical buffers are chosen to eradicate the delays introduced by external factors
other than the operating voltages. Therefore, the only factor that would affect the
propagation delay is the modification of the supply voltage ( V DD ). A narrow pulse is
formed by changing the propagation delay on one of the buffers to allow a slightly