Fixed-tuned high-power F-band TRAPATT amplifier

A FIXED-TUNED MIC TRAPATT amplifier has recently been developed which is insensitive to diode parameter variations such as breakdown voltage and junction capacitance. This characteristic is particularly desirable for applications involving 1 ow cost production such as fusing and phased array radar. In this paper the design and performance of this amplifier will be described. The amplifier dcsign is based on the bandpasss impedance transforming characteristics of a pair of coupled lines’. The use of the coupled line structure allows circuit matching to be realized at the fundamental TRAPATT as well as its harmonic frequencies without additional tuning elements. A coupled line MIC TRAPATT amplifier operated in the second harmonic extration mode has been reported2. This project involved the use of fundamental mode extraction to achieve high efficiency. The basic amplifier excluding the input-output circulator is shown in Figure 1. The amplifier consists of a multiple-section bias-filter, a pair of open-ended coupled lines approximately a quarter-wave in length, and a SMA output connector. Two capacitors of fixed value (0.2 pF) are provided at one end of the coupled line to achieve the proper impedance matching at the second harmonic. The packaged diode is mounted from the ground-plane side and located approximately one third of the line length from the end of the line. Figure 1 illustrates the extreme simplicity of the fixed tuned amplifier circuit.