Tham khảo tài liệu 'ultra wideband communications novel trends system, architecture and implementation part 15', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 60 GHz Ultra Wideband Multiport Transceivers for Next Generation Wireless Personal Area Networks 339 A popular scheme of the conventional I Q modulator demodulator consists of a 90 phase shifter two mixers and a combiner divider. The equivalence between the conventional and the six-port demodulator has been demonstrated as shown in figure 8. Khaddaj Mallat Tatu 2007 . The quadrature I Q signals equations are expressed in 11 and 12 . Fig. 8. Conventional and Six-Port Receivers. Xị t V1 t - V2 t K -a t a 2 cos Ap t 11 xq f V3 f - V4 f K -a t a 2 sin Ap f 12 In order to obtain the DC output signals four power detectors are connected to the six-port outputs. The I Q signals are obtained using a differential approach as indicated in equations 11 and 12 where K is a constant I Q signals In-phase Quadrature-phase V1 to V4 are the detectors outputs signal a is the LO signal power A p t p6 t -p5 is the instantaneous phase difference and a t is the power ratio of RF and LO. A millimeter-wave receiver system simulation is done by Advanced Design System ADS of Agilent Technologies. This receiver system is composed of the proposed six-port local oscillators amplifiers pass-band filters and Sample_and_Hold circuits SHCs . The simulation block diagram is presented in figure 9. The operating frequency is set at 60 GHz and the modulation types discussed are M-PSK QAM Phase Shift Keying Quadrature Amplitude Modulation . In the next paragraph the simulation of the proposed receiver will be based on the measurements results of a fabricated hybrid coupler and not simulation results. Figure 10 shows the simulation results of demodulated constellations using the proposed receiver for 16PSK and 16QAM signals respectively. It proves that this receiver is performing the analog demodulator task. For 16 PSK modulations the constellation points I Q are positioned on a circle and these points are equidistant for the 16QAM modulated signal. During this simulation a coherent LO is used to .
