Optimized Envelope Shaping for Hybrid EER Transmitter of Mobile WiMAX-Optimized ET Operation

The envelope signal of a Hybrid Envelope Elimination and Restoration (H-EER) technique is optimally reshaped to improve linearity and efficiency, resulting in an Envelope Tracking (ET) architecture. The bias V-ds of the ET is adjusted to be a higher value than that of the conventional H-EER technique to enhance the output power and power-added efficiency (PAE). Furthermore, the bias is shifted above the knee region of the PA to reduce the AM/AM and AM/PM distortions at the low bias region. For the verification, the Mobile WiMAX signal with 8.2 dB peak-to-average power ratio and 5-MHz signal bandwidth is used. In the interlock experiment, the PAE of the transmitter is 40% at an output power of 42.04 dBm. By using the digital predistortion technique, the Relative Constellation Error has satisfied the specification of -33.6 dB. These results clearly show that the H-EER transmitter with ET shaping is the most suitable architecture for the highly linear and efficient Base Transceiver Station transmitter.