Multiphase PWM characteristics in the EER transmitter envelope path

To create efficient telecommunication systems we need efficient telecommunication devices. The most energy-consuming element of any radio transmitting equipment is the radio frequency (RF) power amplifier (PA). The highest efficiency of a RF PA can be achieved when its elements operate in switching modes namely in classes D, E, F. Modern efficient telecommunication signals use simultaneous amplitude and phase modulation. Switching PA cannot directly amplify variable amplitude signals. To solve the problem various “synthetic” methods of linear amplification are used. The most promising of these are Kahn method (EER-Envelope Elimination and Restoration). To increase the transmission speed it is necessary to expand the bandwidth of the used frequencies, which is limited by the pulse width modulation (PWM) amplifier of the EER PA envelope path. Multiphase PWM is one way to solve this problem. The use of multiphase PWM in the EER PA envelope path can effectively reduce unwanted PWM conversion products. This will increase the effective bandwidth of amplified frequencies. The article defined efficiency of unwanted components suppression in multiphase PWM, depending on the number of LPF elements for a different number of phases. The requirements for acceptable channel asymmetry in multiphase PWM have been determined. They are quite high and should be taken into account when designing practical devices.