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A dual-mode ring coupler is proposed for balanced frequency doubler application based on the microstrip technology. The proposed coupler can operate in a quasi-hybrid ring coupler mode and a T-junction power divider/combiner mode at two frequency bands with center frequencies of $f_{0}$ and $2f_{0}$ , respectively. The operating principle is analyzed, and the design procedure is described. To verify the proposed concept, a 3-/6-GHz dual-mode ring coupler is developed and fabricated. Measured results demonstrate that the proposed coupler achieves good performances with bandwidths up to 20% at both lower and upper bands. The measurements agree well with the simulations. Finally, as an application demonstration of our proposed dual-mode coupler, a 19-/38-GHz balanced frequency doubler based on this structure is also designed and fabricated. Measured results show that the conversion loss of the fabricated multiplier is less than 8.9 dB with the input frequency ranging from 17 to 21 GHz, and the minimum conversion loss is 7.3 dB at 19 GHz. [ABSTRACT FROM AUTHOR]

In this paper, a W-band single pole single throw (SPST) switch based on a novel PIN diode model is presented. The PIN diode is modeled using a full-wave electromagnetic (EM) simulator and its parasitic parameters under both forward and reverse bias states are described by a T-network. By this approach, the measurement-based model, which is usually a must for high performance switch design, is no longer necessary. A compensation structure is optimized to obtain a high isolation of the switch. Accordingly, a W-band SPST switch is designed using a full wave EM simulator. Measurement results agree very well with simulated ones. Our measurements show that the developed switch has less than 1.5 dB insertion loss under the 'on' state from 88 GHz to 98 GHz. Isolation greater than 30 dB over 2 GHz bandwidth and greater than 20 dB over 5 GHz bandwidth can be achieved at the center frequency of 94 GHz under the 'off' state. [ABSTRACT FROM AUTHOR]