Esko Jarvinen

Bias circuits for GaAs HBT power amplifiers

This paper discusses the effects of process and temperature variations on the performance of GaAs HBT power amplifier bias circuits. A novel feedback bias circuit, which overcomes these problems, is presented. The measured variation from 54 to 60 mA in the bias current, over the temperature range of -25 to +85/spl deg/C, agrees well with the simulations. The circuit is insensitive to variations in the regulated voltage which is a desirable feature in a case when the amplifier is biased to a constant current. On the other hand, a smooth bias and gain control can be achieved by adding an extra resistor connected to a separate control voltage.

Variable gain power amplifier for mobile WCDMA applications

A single chip linear power amplifier (PA) with >48 dB gain control range and >24 dBm output power with adjacent channel leakage power (ACP) figures below -36 dBc is presented. The chip is realized using an AlGaAs-GaAs HBT process and is aimed at 1.95 GHz mobile WCDMA applications. The amplifier consists of two blocks, the variable gain amplifier and the power amplifier; The chip size is 1.3/spl times/1.1 mm/sup 2/ and it is mounted on a 8/spl times/8 mm FR-4 type laminate with 26 pieces of 0402 SMD components composing a complete 50 /spl Omega/ input-output amplifier module. This paper presents the design of the two blocks, discusses issues related to the combining and finally presents the complete amplifier realization and measurement results.

Variable-gain power amplifier for mobile WCDMA applications

A single chip linear power amplifier (PA) with >48 dB gain control range and >24 dBm output power with adjacent channel leakage power (ACP) figures below -36 dBc is presented. The chip is realized using an AlGaAs-GaAs HBT process and is aimed at 1.95 GHz mobile WCDMA applications. The amplifier consists of two blocks, the variable gain amplifier and the power amplifier; The chip size is 1.3/spl times/1.1 mm/sup 2/ and it is mounted on a 8/spl times/8 mm FR-4 type laminate with 26 pieces of 0402 SMD components composing a complete 50 /spl Omega/ input-output amplifier module. This paper presents the design of the two blocks, discusses issues related to the combining and finally presents the complete amplifier realization and measurement results.

An integrated 900-MHz push-pull power amplifier for mobile applications

This paper describes a two-stage 900-MHz push-pull type GaAs HBT MMIC power amplifier with 3.2W (35dBm) maximum output power and 57% maximum power added efficiency with a supply voltage of 3.5V. The small-signal gain of the PA is 30dB. The size of the realized power amplifier chip is 1.2*1.3mm/sup 2/. The drawbacks and advantages of the push-pull topology are discussed and compared to a traditional single-ended topology.

GaAs HBT power amplifier with smooth gain control characteristics

A gain control scheme giving simultaneously an effective power switch-off operation and smooth gain control characteristics is presented. The concept was applied to a 3-stage power amplifier which was a part of a 900-MHz transmitter chip. The chip was realised by using GaAs MMIC technology and was mounted on a ceramic substrate. The power amplifier was tested separately by mounting it directly on a conventional FR4 board. In this lossy environment the power amplifier delivered an output power of 33.2 dBm with a supply voltage of 3.5 V. The maximum value of the gain control slope was 22 V/V showing a good agreement to the simulations.

Comparison of measured and simulated /spl pi//4-DQPSK adjacent channel power using a functional high power amplifier model

A novel functional nonlinear high power amplifier model for radio communication system simulations is used to study spectrum regeneration of a nonlinearly amplified /spl pi//4-DQPSK signal. Simulated adjacent channel power has been compared to measured results, and a very good resemblance is found. This together with a satisfactory intermodulation behaviour in a two-tone test simulation verifies that the proposed model is applicable to accurate adjacent channel power prediction in radio system simulations.

Integrated power measurement circuit for RF power amplifiers

A RF power measurement circuit, which operates on the same chip with an integrated RF power amplifier, is presented. The circuit is capable of measuring load variation dependent output power changes. Full integration saves the PCB area needed for the line coupler used in conventional power detection methods. The circuit was realised using GaAs MMIC technology and tested on a standard FR4 test board at 900 MHz. The circuit detects RF power in a range of 35 dB with a sensitivity of 0.8 V/W showing good agreement with the simulations.