A European ISM band power amplifier module

In this paper we present a power amplifier module suitable for the 433 MHz European ISM band frequency. The PA module provides a maximum 30 dBm output level at 433 kHz. The included power control circuit provides 30 dB of dynamic range control. The overall module was designed on a single test board with a 4.8 V supply voltage. The maximum output power deviation is less than 1 dB over the complete control range. Measurements for two tone tests (with a 100 kHz offset) show that the measured intermodulation products are -35 dBc for a -35 dBm input power level. Four different variations of our basic design have been implemented. They differ in the types of directional coupler used and the types of power control circuit used. All designs use directional couplers with an envelope detector for the power control feedback circuit, which offers accurate power detection, high linearity and stable output power. The inherent simplicity of the new design makes it useful for many applications. At the highest output power level, the measured power efficiency of the PA module is 40%.