Design Of Key Microwave Circuits For Wideband Signal Generator

Now in the RF and microwave testing field, signal generator is one of the most important and widely used electronic instruments. The application of debugging, testing for most of the microwave devices, and other electronic equipment maintenance often needs to use signal generator. Therefore, to design a low cost, high performance signal generator is very important and meaningful.In this dissertation, the mainly studies of the signal generator are some key microwave circuit, and including Harmonic mixer and Octave filter assembly. Harmonic mixer mainly include input and output power amplifier module, balun, multiplier, single balanced mixer and low pass filter. Input and output amplifier modules are used to amplify the Oscillator and IF signal power; the purpose of selecting balun output two local oscillator signals, output signals are of equal magnitude and of opposite phase; we are selecting AEROFLEX company’s MSPD2018 phase detector as a mixer, the mixer are connected by the single balanced mixer and step recovery diode(SRD); the harmonic signals of local oscillator are mixing with RF signals, and output IF signals; the purpose of low pass filter is filtering out unwanted noise signal, which are including the fundamental signals, up-conversion signals and some down-converted signals. The design of harmonic mixer applies ADS software. The test results of harmonic mixer: in the 3-10 GHz range, the LO and RF isolation is 18-25 d B; the minimum conversion loss is 11 d B, when we consider the wideband of mixer and high-harmonic signal(harmonic up to 16 times), in general the performance of harmonic mixer is good.Octave filter assembly is consisting of microwave switch, frequency multiplier, band-pass filter consisting. The frequency range of input signal is 3-10 GHz, the microwave switch(SPDT) output two columns, one signal output to the multiplier, multiplier is a x2 active broadband frequency multiplier, the signal output to the three band-pass filter via multiplier, the task of the band-pass filter is selecting the signals which we want to get, the frequency range of signal is 10-13 GHz, 13-16 GHz and 16-20 GHz. The band-pass filters are interdigital filters, the advantages of this structure are small size, compact structure and so on. We are simulating band-pass filters by CST software.