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Frequency extender modules of vector network analyzers and signal generators, as well as front-end modules of semiconductor automatic test systems, make use of broadband resistive diode frequency multipliers. This paper presents the design and fabrication of innovative planar varistor frequency multipliers. Three frequency triplers (#1, #2, #3) and two frequency doublers (#4, #5), operating in the 60-110 GHz and 50-110 GHz frequency ranges, respectively, are designed. The hybrid architecture utilizes commercial gallium arsenide Schottky diodes from United Monolithic Semiconductors on thin-film processed high-permittivity alumina substrate. Synthesis is based on a co-simulation procedure between 3-D electromagnetic field and nonlinear harmonic balance circuit simulations. Scalar and spectral measurement data over the focused output frequency ranges are presented. Conversion loss values around 18 dB from 60 to 95 GHz and below 22 dB from 60 to 110 GHz are achieved with frequency tripler #1. Frequency doubler #5 achieves conversion loss values below 15 dB from 50 to 89 GHz and below 22 dB from 50 to 110 GHz. A comprehensive comparison of the presented work with reported frequency multipliers is included.

The demand on advanced personnel screening systems led to the development of several active and passive imagers. Among them, active multistatic imaging ensures high image quality and allows fully electronic screening. An active E-band imager is presented in this paper, which measures in real-time and delivers images of 30-dB dynamic range. Imaging of humans is achieved by optimizing the acquisition time using a dedicated digital signal processing solution. This paper introduces the system hardware, the calibration procedure, and several measurement results demonstrating high quality imaging capabilities.

The interest in active millimeter-wave and microwave imaging systems is increasing due to their utilization in security, medical, and industrial applications. Imaging systems using monostatic arrays suffer from the high number of antenna positions, making a fully electronic solution very costly and impractical. Multistatic arrays, however, offer the chance for high reduction factors in the number of antennas, and then allow for fully electronic solutions. Here, a new array architecture is presented, which is suitable for real-time operation and is capable of delivering high image quality in means of resolution and dynamic range. Various technological solutions were developed for the imaging purpose, which are introduced in detail. An example array for operation from 72 to 80 GHz is demonstrated. The imaging system hardware is introduced, along with several imaging results of humans with concealed objects.

A bandpass filter for 300 GHz with a stopband at 450 GHz based on a highly efficient binary grating as a frequency-selective element was developed and optimized. The geometry of the grating was carefully designed for a maximum difference angle between reflected beams at 300 and 450 GHz and for maximum efficiency at 300 GHz. The grating efficiency was optimized using a rigorous theory of diffraction, yielding a maximum efficiency of over 99.5% neglecting conductor losses. Antennas and elliptical mirrors are used for optimum quasi-optical illumination of the grating and Gaussian beam shaping. After an optimization and a comprehensive examination of the grating in an experimental heterodyne measurement setup at 300 GHz, the filter was implemented fixed tuned into a small housing with waveguide flanges. The fixed tuned setup with corrugated feed horns results in an overall flange-to-flange insertion loss of only 2.8 dB.

The block diagram shown in Fig 33 of the above-named paper [ibid., vol. 61, no. 12, pp. 4442–4460, Dec. 2013] is incorrect. Instead of series resonators, it should contain parallel resonators. A corrected version is provided here as Fig. 1. In the continuous text of the above paper [p. 4451, col. 2, line 38] it reads "MSL half-wave series resonator," which is incorrect. It should read "half-wave MSL parallel resonator."

Generalized unilateral fin-line configurations for extended millimeter-wave applications are analyzed using the equivalent transmission-line concept in the spectral domain. Numerical results for the frequency-dependent propagation constants and characteristic impedances of various stuctures are presented.

The spectral domain analysis is applied for deriving despersion characteristics of dominant and higher order modes in fin-line structures. In addition to the propagation constantant, the characteristic impedance is calculated based on the power-voltage definition. Numerical results are compared for different choices of basis functions and allow to estimate the accuracy of the solution.