A handset power amplifier with high efficiency at a low level using load-modulation technique

A new monolithic-microwave integrated-circuit power amplifier for cellular handsets has been implemented using the load-modulation concept of the Doherty amplifier, which has a high efficiency at a low power level. In order to get a compact module, the /spl lambda//4 transmission line for the load modulation is replaced by a passive high-pass /spl pi/-network, and the load-modulation circuit is also modified to function as a power-matching circuit of the main amplifier. The amplifier has two modes of operation, low- and high-power modes, controlled by a control voltage. At the high power mode, both the main and auxiliary amplifiers are operational and, at the low power mode, only the main amplifier generates output power enhancing the efficiency. For the code-division multiple-access environment, the amplifier at the low-power mode provides power-added efficiency (PAE) of 39.8% and an adjacent channel power ratio (ACPR) less than 49.8 dBc at 23.1 dBm, and the high-power mode PAE of 37.9% and ACPR of 46.4 dBc at 28 dBm. The efficiency is improved by approximately 18.8% at P/sub out/=23 dBm by the load-modulation technique. For the advanced mobile phone system-mode operation, the amplifier delivers 26.1 dBm with PAE of 53% and 30.8 dBm with 48.7% at the low and high modes, respectively.

[1]  K. Kim,et al.  A highly efficient CDMA power amplifier based on parallel amplification architecture , 2004, IEEE Microwave and Wireless Components Letters.

[2]  Bumjae Shin,et al.  A fully matched N-way Doherty amplifier with optimized linearity , 2003 .

[3]  Bumman Kim,et al.  A CDMA and AMPS handset power amplifier based on load modulation technique , 2004, 34th European Microwave Conference, 2004..

[4]  A. Samelis,et al.  Efficiency improvement techniques at low power levels for linear CDMA and WCDMA power amplifiers , 2002, 2002 IEEE Radio Frequency Integrated Circuits (RFIC) Symposium. Digest of Papers (Cat. No.02CH37280).

[5]  Jaehyok Yi,et al.  Optimum design for linearity and efficiency of a microwave doherty amplifier using a new load matching technique , 2001 .

[6]  P. Asbeck,et al.  An extended Doherty amplifier with high efficiency over a wide power range , 2001, 2001 IEEE MTT-S International Microwave Sympsoium Digest (Cat. No.01CH37157).

[7]  Steve C. Cripps,et al.  Advanced Techniques in RF Power Amplifier Design , 2002 .

[8]  Peter Vizmuller,et al.  RF Design Guide Systems, Circuits and Equations , 1995 .

[9]  Bumjae Shin,et al.  An adaptive bias controlled power amplifier with a load-modulated combining scheme for high efficiency and linearity , 2003, IEEE MTT-S International Microwave Symposium Digest, 2003.

[10]  Peter B. Kenington,et al.  High-Linearity RF Amplifier Design , 2000 .

[11]  W. H. Doherty.  A New High Efficiency Power Amplifier for Modulated Waves , 1936 .