Study On Efficient Passive Frequency Tripler

With the continuous development of communication technology,the proliferation of communication products has led to the shortage of available spectrum resources,especially the ISM frequency band which is widely used and can be used for free without authorization.Millimeter-wave frequency band has attracted much attention because of its wide bandwidth and its ability to solve the problem of insufficient spectrum resources.Therefore,the frequency source of millimeter-wave frequency band in ISM frequency band is very important.The millimeter wave frequency source is mainly realized by the cascade of low-frequency frequency source and frequency doubler,so the millimeter wave frequency doubler with good performance has important research significance.In this paper,the research on the millimeter wave frequency tripler with the center frequency of 61.25 GHz in ISM band is carried out.In this paper,ISM frequency band and Millimeter-wave frequency band are briefly introduced,and the research status at home and abroad is summarized.Then the basic theory of frequency doubler is studied and analyzed,including the basic principle of frequency doubler,the realization scheme of frequency doubler,the working principle of the varactor diode and the analysis method of the frequency doubler.Then the frequency tripler is studied and designed.Gallium arsenide varactor diode MA46H146 is selected and modeled.After integrating the factors such as volume,price,processing difficulty and performance,in order to meet the requirements of small volume,low cost and easy processing,the microstrip line structure with RT/duroid5880 0.508 mm thick as the medium substrate and the diode reverse parallel structure which can suppress even harmonics are selected to design the frequency tripler.Due to the reverse parallel structure of diodes,even harmonics are naturally suppressed,and in order to reduce the complexity of the design,the even harmonics are not considered.In order to achieve miniaturization,the design of high and low resistance low-pass filter is studied,and the low-pass filter at the front end of the frequency doubler is designed by Butterworth prototype filter.The S11 of the filter is less than-20 d B below 20 GHz,and the S21 is less than-20 d B above 50 GHz.Therefore,the low-pass filter only allows the fundamental signal to pass through,and the third and higher harmonic signals cannot pass,which meets the requirements of the designed frequency multiplier.In order to maximize the power of the output signal,the theory of impedance matching is studied.After the input and output impedance of the diode reverse parallel structure is extracted,it is matched by the Smith circle graph theory.In order to simplify the design structure of frequency multiplier,the idle circuit is used to replace the output filter network,so the idle circuit is studied and designed.Finally,the designed modules are combined for overall simulation and optimization.The simulation results show that when the input signal frequency is 20.4GHz and the input power is 100 m W,the output 61.2GHz signal power is17.465 d Bm with the highest frequency doubling efficiency of 55.78%.In the whole input frequency range,the fundamental wave suppression is greater than 50 d Bc,and the harmonic suppression is greater than 100 d Bc,meeting the design requirements.In this paper,varactor diodes are used,and the frequency tripler designed by using the variable capacitance characteristics of non-linear devices has higher frequency multiplication efficiency,which is of great significance to the design of millimeter wave frequency doublers.