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A novel waveguide-to-microstrip inline transition was proposed using a wedge-waveguide iris to form an ultra-compact U-bend waveguide. The wedge-waveguide iris not only functioned as a wide wall of the height-reduced waveguide for the $E$ -plane probe, but also played a critical role in impedance matching and parasitic resonance suppression. The working principle was investigated through theoretical analysis and full-wave simulation, and the relevant design processes for the transition were discussed. Moreover, two back-to-back transition prototypes, one working at the $W$ -band and the other working at the WR4.3 band, were designed, fabricated, and measured. The back-to-back prototypes obtained an insertion loss of less than 0.8 and 1.2 dB, with a return loss better than 15 dB in the $W$ -band and WR4.3 band, respectively. The measurement results were consistent with simulation results. A miniaturized 110-GHz tripler incorporating this transition for inline output was fabricated. A conversion efficiency of 2.5%–3.6% was achieved in 90–120 GHz at 100-mW driving power. [ABSTRACT FROM AUTHOR]

In this article, a novel waveguide-to-microstrip transition with a built-in dc/IF return path is proposed, in which a traditional E- plane probe is directly connected to the backshort by a thin metal wire along the axis of the waveguide. The proposed waveguide-to-microstrip transition implements an additional dc/IF return path while realizing mode conversion. Moreover, the presence of the dc/IF return path has little influence on the performance of the original E- plane probe. The operating principle is analyzed by theoretical analysis and full-wave simulation, and the design procedure of the transition is also presented. To implement the proposed dc/IF return path on different substrates, two approaches, including direct integration with planar circuits or with wire bonding technology, are developed. Furthermore, two back-to-back transition prototypes working in the millimeter and submillimeter bands were designed and characterized. The measured results are in excellent agreement with the simulations. Finally, as an application example, a 70-/140-GHz unbalanced frequency doubler adopting this structure for both dc biasing and dc grounding was designed and fabricated. Measured results show that the conversion loss of the fabricated doubler is less than 13 dB in the range from 125 to 145 GHz, and the minimum conversion loss is 11 dB at 140 GHz with 100-mW input power. [ABSTRACT FROM AUTHOR]

This paper describes the design and demonstration of a 135–190 GHz self-biased broadband frequency doubler based on planar Schottky diodes. Unlike traditional bias schemes, the diodes are biased in resistive mode by a self-bias resistor; thus, no additional bias voltage is needed for the doubler. The Schottky diodes in this verification are micron-scaled devices with an anode area of 6.6 μm2 and an epitaxial layer thickness of 0.26 μm. For accurate design of the doubler, the 3D-EM model of the Schottky diode is built up to extract the parasitic parameters induced by the diode package when frequency rises up to the terahertz band. In order to implement broadband working, input waveguide steps, output suspended microstrip steps, and output probe with bias filter are all used as matching elements for impedance matching. Measured results show that the doubler exhibits a 3 dB bandwidth of 34% from 135 GHz to 190 GHz, with a conversion efficiency of above 4% when supplied with 100 mW of input power. A 17.8 mW peak output power with a 10.2% efficiency was measured at 166 GHz when the input power was 174 mW. The measured results agree well with the simulated results, which indicates that the self-bias scheme for Schottky diode-based frequency multipliers is feasible and effective. [ABSTRACT FROM AUTHOR]