Millimeter-wave Broadband Frequency Multiplier

Millimeter multiplier, generally used for decreasing the basic oscillator of millimeter equipments and expanding frequency spectum, is a very important component in millimeter system. Meanwhile, the advantages of the microwave equipments, such as high stability and excellence phase-noise performance, can be held in millimeter range.In this paper,K and Q band doublers,based on the balanced multiplier theory, are designed and fabricated by utilizing the Schottchy diodes DMK-2784. This kind of doubler, composed of microstrip(MS)-to-coplanar waveguide(CPW), microstrip–to-slotline(SL),microstrip-to-rectangle waveguide transitions and CPW-to-SL junction, can realize good odd harmonic suppression with FBW more than 40%. In this design, the passive elements of the doubler are simulated and optimized via CAD software HFSS and CST, then the output power and harmonic characterictc of the doubler is analyzed by harmonic balance analysis in ADS.For input power Pin=17dBm, the conversion loss of the K band doubler is about 17.75±3.75dB and the odd harmonic suppression is more than 24.2dBc in the frequency range from 8.25GHz to 12.5GHz.The best conversion is about 14dB for the frequency 9.3GHz. For input power Pin=15dBm, the conversion loss of the Q band doubler is about 13.7±3dB in the frequency range from 17GHz to 24GHz. The best conversion is about 10.7dB for the frequency 21.5GHz. The third harmonic suppression is more than 24.7dBc.Usually a junction of two or more waveguides and transmission lines, such as microstrip, CPW and slotline, is used to provide the required amplitude and phase relationships and an input/output isolation in this kind doubler. In this paper, we also explained the transition theory for MS-to-CPW,MS-to-SL and MS-to-rectangular waveguide. Furthermore, we simulated these transitions by utilizing HFSS and CST, and then obtained some useful results for the doubler design. Finally, the back-to-back transitions were fabricated and measured. The results show that for the MS-to-CPW transition, the insertion loss is less than 2.2dB and the return loss is better than 11dB in the frequency range from 8.25GHz to 12.5GHz.