An octa-phase differential relaxation VCO generating both triangular and rectangular waveform outputs is designed for 8-PSK subcarrier generation in FM-UWB transceiver systems. The VCO consists of cascaded quad-phase relaxation oscillators in which the second stage oscillator provides 45° phase shifting with pseudo injection locking. The 5.2-11.8MHz octa-phase VCO implemented in 0.18μm CMOS consumes 2.5mW from a 1.8V supply.