Reducing the drive signal bandwidths of EER microwave power amplifiers

High efficiency and linearity can be achieved using Kahn´s envelope elimination and restoration (EER) technique. However, when used with modulation schemes such as CDMA and orthogonal frequency division multiplexing (OFDM), the resulting polar drive signals suffers from expanded bandwidth. Rudolph has shown that the bandwidth of the polar drive signals can be reduced by hole punching (limiting the minimum envelop of the modulated signal). This paper quantifies the error vector magnitude (EVM) caused by the ensuing distortion and compares the performance to a distortionless method based on the well known partial transmit sequence (PTS) method for OFDM. Although the hole punch process performs better than the PTS approach in terms of spectrum improvement, its EVM will limit the data throughput of the transmission.