The frequent use of vector modulators and mixers in microwave and telecommunication systems increases the need of designing new prototypes for these two components.; The design and realisation of three circuits are presented in this thesis: a direct microwave vector modulator, a gate mixer and a balanced mixer.; The direct vector microwave modulator covers the Ku band and has a double balanced configuration. It has been designed by using only passive elements (hybrid quadrature couplers) and MESFETs that are biased to work as resistive elements. The vector modulator prototype have been fabricated in the hybrid and monolithic technologies, capable to support input power that can vary from one to several watts. The distortion and noise level are very low, and the mismatch coefficients at the different ports are −30 dB. The hybrid prototype of the vector modulator presents good results but the experimental measurement on the monolithic version reveals some errors on the physical layout. These errors have been corrected and a new Layout was generated and submitted for a new fabrication.; The simulation of the mixers have shown that the isolation between the IF signal and the RF and LO signal are −36 dB and −54 dB for the gate mixer, and −58 dB for the simple balanced gate mixer. They also present excellent conversion gains, and good isolations between the IF signal and the different harmonics. The layouts of the mixers are presented in this thesis.
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