Design And Characteristics Of A 144MHz 8W Low Power Linear Amplifier.pdf

1. An 8W linear amplifier using the Mitsubishi RA08H1317M RF MOSFET power amplifier module is designed for use with the Anglian 144MHz transverter. The amplifier operates in Class AB and features stable, low voltage operation with high gain and low drive level requirement. It also has good linearity, especially when the output is kept below about 5W PEP. The amplifier draws less than 1.5A at 13.5V at full output. The module is a small 30 x 10 x 5.4 mm power amplifier module using RF MOS FET technology. The device number indicates it is an 8W amplifier for use between 130 and 170MHz. The amplifier module has four connection pins plus ground, with the connections being RF Input, Gate Voltage, Drain Voltage, and RF Output. The gate bias voltage is purposely held at 3.4V by R1 and R2, and a series-connected 3 Amp silicon rectifier diode, D1, is recommended in the supply to the amplifier to drop the supply voltage and provide protection against accidentally reversing the supply to the transverter and amplifier. The circuit is straightforward, with a low pass filter consisting of L1, C7, L3, C9, and L3, which has been carefully modelled and tested to check that it agrees with the model design. The filter has less than 0.3dB insertion loss at 144MHz with over 25dB input return loss, and the second harmonic is suppressed over 20dB and the third harmonic by over 50dB.