Sharif Digital Repository

In this letter, a compact, wideband, and fully planar microstrip crossover structure is proposed. This design is based on a compact microstrip to coplanar waveguide transition, which has a measured bandwidth extending from dc to 40 GHz. At 20 GHz, the measured insertion loss, return loss, and isolation are better than 0.35, 21, and 19 dB, respectively. This circuit is ultracompact with the core size of 3 mm ×3 mm, which is 0.2λ×0.2 λ at 20 GHz. © 2012 IEEE  

This letter presents a symmetrical slot-type bowtie antenna with widened impedance bandwidth and high efficiency. Two symmetric vias are exploited underneath each slot in order to increase the antenna bandwidth up to 84% with simultaneous preservation of high efficiency (>90%), and low cross-polarization (<-10 dB). The proposed antenna is fed with 50Ω ungrounded coplanar waveguide (CPW) with no need to balun insertion and tuning stub. The proposed antenna has low profile and simple structure in comparison with previous complex wideband bowtie antennas. The commercial CST Microwave Studio software is adopted for the simulations. The antenna is fabricated and measured, while good agreement is... 

In the present work, a non-linear distributed circuit model for superconducting rectangular-spiral resonators is proposed. This is based on an accurate non-linear circuit model for superconducting parallel coupled lines, which is simultaneously considered both quadratic and modulus non-linear dependencies. The non-linearity in superconducting devices depends on the current distribution, which is mainly determined by the geometrical structure of the device. The current distribution in the superconducting spiral resonators can be computed by a numerical approach based on three-dimensional finite element method. This computed current distribution is used to produce a non-linear circuit model... 

In the present work, a non-linear distributed circuit model for superconducting rectangular-spiral resonators is proposed. This is based on an accurate non-linear circuit model for superconducting parallel coupled lines, which is simultaneously considered both quadratic and modulus non-linear dependencies. The non-linearity in superconducting devices depends on the current distribution, which is mainly determined by the geometrical structure of the device. The current distribution in the superconducting spiral resonators can be computed by a numerical approach based on three-dimensional finite element method. This computed current distribution is used to produce a non-linear circuit model... 

This paper presents a sequence of affordable methods applied to diagnose a millimeter-wave system-in-package. The module used in this paper is a 60 GHz transceiver with a waveguide interface, designed to transmit 8 dBm of saturated power. It consists of a flip-chipped RFIC, a multi-layer organic substrate, a metal enclosure with a standard waveguide interface, passive components and a 30-pin connector. The first measured output power was 3 to 6 dB below the desired value over the 60 GHz band. Thus, all parts of the module were thoroughly investigated to detect the cause of power drop. By 3-D electromagnetic simulation of the enclosure, the cavity modes and power leakage in the enclosure were...