QPSK Modulation Scheme Based on Orthogonal Gaussian Pulses for IR-UWB Communication Systems

A new impulse radio-ultra wideband (IR-UWB) communication system with quadrature phase shift keying (QPSK) modulation scheme was presented in this research. The system utilized orthogonal property of fourth- and fifth-order derivatives of Gaussian pulses for modulation and time hopping (TH) multiple-access scheme. This system was compared with conventional TH-PPM and TH-BPSK systems at the same condition. The simulation results in multipath channel showed that the proposed system can provide better bit rate performance compared with the conventional IR-UWB system. A very low power and low complexity circuit for generation of the fourth-order derivative of Gaussian pulse was also proposed. The circuits of fourth- and fifth-order derivatives of Gaussian pulses were simulated using a 0.18 mu m CMOS technology. The core chip size was only 0.015 mm(2). The output amplitude pulse yielded 135 mV peak to peak under a supply voltage of 1.8V. The energy consumption of the fourth- and fifth-order derivatives of Gaussian pulses circuits were 8 pJ/pulse for 200 MHz pulse-repeating frequency (PRF).