Masami Ohnishi

Switch-less-impedance-matching type W-CDMA power amplifier with improved efficiency and linearity under low power operation

A W-CDMA power amplifier with new impedance matching technique, Switch-Less Impedance Matching (SLIM), is fabricated to improve the efficiency and linearity of a power amplifier at medium- to low-power ranges. In a SLIM amplifier, two amplifiers with different saturation powers are connected in parallel, and operated alternately without switches in the signal path. At its full power of 25.6 dBm, fabricated SLIM amplifier module exhibited power added efficiency of 38% with ACPR of -40 dBc, which is comparable to existing PAs for W-CDMA. Furthermore, at 15 dBm, its power added efficiency is as much as 12% with ACPR of -42 dBc. Throughout its output power range up to 25.6 dBm, the SLIM PA can provide very high linearity of under -40 dBc ACPR. Furthermore, the efficiency of 12% is not possible from a single amplifier with fixed load impedance.

Thermal Gain Variation Compensation Technique Using Thermistor on HPA Module for W-CDMA System

The thermal gain variation of a high-power amplifier (HPA) module for a wide-band code division multiple access (W-CDMA) system application was reduced to within ±1dB by applying a thermistor to compensate the gain variation. Two techniques for gain variation compensation with respect to temperature were investigated: base bias control according to temperature, and use of a thermistor in a matching network. Experimental comparison of two techniques indicated that the thermistor-based technique was more effective in reducing the gain variation without affecting linearity. A fabricated two-stage HPA module with a thermistor in its input matching network achieved a small gain variation within ±1dB and ±5MHz offset adjacent channel leakage power ratio (first ACLR) below -36dBc over the temperature range from -10 to +85°C, where the first ACLR was measured under a load-mismatched condition with a voltage standing wave ratio (VSWR) of 1.4 : 1.

Reduced gain variation against temperature with thermistor on HPA module for W-CDMA system

A high-power amplifier (HPA) module for wide-band code division multiple access (W-CDMA) system with small gain variation against temperature is presented in this paper. Two temperature compensation techniques, which contain gain control bias circuits that correspond to temperature or thermistors were investigated. Comparison between the above techniques indicated that the technique with thermistors was more effective in reducing gain variation without affecting linearity. A fabricated two-stage HPA module for W-CDMA system with a thermistor in its input matching network provided a small gain variation within plusmn1 dB and an ACLR under -36 dBc in the temperature range from -10 to +85degC when ACLR was measured under load mismatched conditions, VSWR=1.4:1.