Development of multichannel transmitters short-centimeter-wave systems for multiple radio access
Theoretical study of intermodulation distortion in nonlinear power amplifier has been done. It relates to a generation of second harmonics of input signal and allowed to present a new linearization principle of these devices, which is based on use of mentioned harmonics energy as a feedback signal. Calculations of impact of described mechanism upon signals of different digital modulation types have been conducted. Significant reduce (up to 25 dB) in crosstalk level has been reached. And 1dB compression level of amplifier output power has almost reached saturation point. As compared to known methods of linearization of single transistor power amplifiers at shortwave part of centimeter and millimeter wavelengths, simplicity of implementation of the proposed one makes it most promising in this frequency range of wireless communications.
According to conducted study a design and engineering principles of realization of fully planar power combining circuits has been developed. Today spatial power combining method is the only way to reach output power levels of more than 35 dBm and previously has been implemented using spatial structures. In contrast to those, the presented circuits are fully planar and thus can be included as a part of transmitters’ circuits produced by a hybrid- or monolithically-integrated technology.
Precision technological equipment has been designed, which allows to conduct measurements of high order intermodulation distortion and crosstalk introduced by amplification of real multichannel digital signals.
Linearized power amplifiers and multichannel transmitter on their basis have been designed. Transmitter is a part of base station of wireless access system in a 12 GHz frequency range.
Theoretical study in a new field of system compensation of nonlinear distortion in multichannel transmissions by means of additional digital encoding and corresponding filtration has been done, which is important for present communication channels. A possibility of improvement of channel characteristics without replacement of actual transmitters with high crosstalk levels has been shown.