Design of a W-band Frequency Tripler for Broadband Operation Based on a Modified Equivalent Circuit Model of GaAs Schottky Varistor Diode

This paper presents the design and experimental results of a W-band frequency tripler with commercially available planar Schottky varistor diodes DBES105a fabricated by UMS, Inc. The frequency tripler features the characteristics of tunerless, passive, low conversion loss, broadband and compact. Considering actual circuit structure, especially the effect of ambient channel around the diode at millimeter wavelength, a modified equivalent circuit model for the Schottky diode is developed. The accuracy of the magnitude and phase of S21 of the proposed equivalent circuit model is improved by this modification. Input and output embedding circuits are designed and optimized according to the corresponding embedding impedances of the modified circuit model of the diode. The circuit of the frequency tripler is fabricated on RT/Rogers 5880 substrate with thickness of 0.127 mm. Measured conversion loss of the frequency tripler is 14.5 dB with variation of ±1 dB across the 75?~?103 GHz band and 15.5?~?19 dB over the frequency range of 103?~?110 GHz when driven with an input power of 18 dBm. A recorded maximum output power of 6.8 dBm is achieved at 94 GHz at room temperature. The minimum harmonics suppression is greater than 12dBc over 75?~?110 GHz band.