Front end HPA/antenna for Multi-Radio
Résumé
This paper focuses on multi-radio front end transmitter, a function implied by cognitive radio (0.5 to 6 GHz). S and C bands standards (WLAN/MAN) present a challenge, due to the signals modulation schemes (OFDM/WCDMA) dynamic (tens of dBs), driving us to a mandatory transmitter linearization. The idea is to provide frequency flexibility and average power control of a multi-radio high efficiency front-end for such signals (polar/EER structure). The study implies antennas design and average power control demonstration. Based on switched mode power amplifier, a discrete detuning is possible to adapt the PA at both "WiMAX" and "Wifi5" frequencies. This architecture amplifies signals with amplitude information. This latter is here coded by ΣΔ/PWM technique, to present a constant envelope signal. The AM information is restored by a pass-band RF filter. The antenna can be designed with a notch, to reduce the filtering constraints (selectivity and standards coexistences) and to help in the restoration of amplitude information. Average power control is illustrated by voltage supply variation and results are a possible dynamic of 9.5 dB. To complete the analysis, the simulation of the propagation channel, including antennas, with CST (free space, line of sight) is imported under AGILENT-ADS.