| The simulation of multi-in multi-out (MIMO) communication systems requires the realization of a channel emulator in order to test and calibrate equalization algorithms of digital signals. Channel emulator is composed of several modules among them an amplitude attenuator and phase shifter. These two components are generally time varying with linear control. In fact, when they are not linear, we can not extract the modulated transmitted signal. Circuit linearity allows modulator realization.;In the first part of this work, we propose the design and realization of a variable attenuator based on PIN diode. The proposed model for this diode is obtained by the analysis of the reflection coefficient of an adequate circuit. The obtained model describes mostly the physical behaviour of the PIN diode.;In the second part of this work, we suggest the design and realization of a phase shifter based on varactor diodes. The modeling of this diode is performed as in the case of PIN diode. We note that obtained models do not totally fit physical characteristics of PIN and varactor diodes. So, it is necessary to improve the two proposed models.;Our proposed linearization procedure is not based on the I/V semi-conductor characteristics. Indeed, we have suggested transforming diode control potential by a numerical method. Obtained results show that the proposed architectures allow linear attenuation and phase shifting. However, our procedure can be improved by the use of FPGA (Field Programmable Gate Array) which reduces the computation errors and noise power. |
