.8 Ghz, Spectrum Analysis Instrument Receiver Front-end Development

In the fields of scientific research and production exploitation, such as modern communication, broadcast and television, the test of frequency domain has already become the essential means to solve problems. Spectral analyzer is the basic tool to realize this function. To solve the problem of high price of the spectral analyzer, domestic development of the spectral analyzer becomes more and more important.In this paper, a spectral analyzer receiver front-end is introduced, which works in the frequency range of DC to 8000MHz. In order to effectively suppress image frequency of the input signal, the high IF is chosen to realize the first frequency conversion; low IF is chosen to realize the second and third frequency conversion, and finally the signal frequency is converted to 76.8MHz.First of all, the principle of the heterodyne spectrum analyzer is deeply analyzed, the same as the aim of the receiver design. Then, the key of this paper: the design method of wide stopband lowpass filter, the design of miniature coaxial filter, the simulation of the circuit system and the realization of the circuit and system. Finally, the system design and ultimate testing results are represented: the maximum input level is 30dBm, the noise figure of the receiver front-end is less than 26dB, the total gain is about 20dB, and the typical value of the IMC3 is -66dBc, when the power of the input two tone signals are -30dBm. All of the above can satisfy the spectral analyzer.