Design, analysis and simulation of hybrid integrated NRD guide based QPSK modulator for LMDS applications at 28GHz

This paper reports design, analysis and simulation of QPSK modulator in Ka-band. The modulator is designed at 28GHz frequency in hybrid microwave integrated circuit (HMIC) technology. For feasible high frequency operation, the design is integrated with non-radiative dielectric (NRD) guide using NRD guide to Microstrip line transition. In simulation, the observed value of the maximum phase deviation from the quadrature phase shift is 5°. Error vector magnitude (EVM) of the designed modulator is determined to be 11.9% for 400 Mbps digital data rate, modulated over 28 GHz RF carrier. The effect of amplitude and phase variations is analyzed through a constellation diagram, power spectrum and eye pattern.