Realization and performance analysis of FPGA based offset quadrature phase shift keying (OQPSK) modem

Phase Shift Keying is a modulation technique employed in transmitting digital baseband data (message) from one point to other over a channel such that there is no corruption in information. This technique involves alteration of phase of the carrier signal according to base band data. Quadrature Phase Shift Keying (QPSK) is a phase shift keying technique which is most recurrently employed scheme in modern satellite communication systems. Offset Quadrature phase shift keying (OQPSK) is a variant of Quadrature Phase Shift Keying (QPSK) which has an advantage over conventional QPSK data transmission scheme in terms of mitigating spectral regrowth when data transmission takes place in nonlinear channels. This modulation scheme is commonly used in various communication and remote sensing satellites for payload data transmissions, telemetry and tele command systems. This paper describes design and hardware implementation of OQPSK modulator and demodulator. The proposed design is designed and implemented using Xilinx ISE software and Xilinx System Generator for MATLAB. The proposed design is implemented on Virtex 5 XUPV5110T FPGA. Bandwidth analysis, transmission characteristics, Bit Error Rate (BER), Power Analysis of proposed OQPSK modem is also presented in this paper.