This paper describes the design of high-performance compact aperture array antennas for radio astronomy and other applications. Three recent antenna developments for square kilometer array design study (SKADS) have been investigated and the performances are compared. In addition to the radio frequency (RF) performance, an essential requirement for the square kilometer array application is the cost per square area. Based on initial large–scale finite array studies, prototypes with different geometries have been fabricated and measured. Guidelines are derived for large–scale wide–band dual-polarized array designs in applications where low cross-polarization and a wide range of scan angles are required.

This paper presents an analysis of totem-pole (TP) stages for driver applications and summarizes the major design constraints for an optimization with respect to P1dB, OIP3, and bandwidth. It is shown, that for matched drivers, in contrast to the widely applied common collector (CC) stage, class-AB TP stages offer higher output power and much higher power-added efficiencies (PAE) at comparable bandwidth. A combiner chip in 0.25 μm SiGe Bipolar CMOS (BiCMOS) verifying this concept in hardware as output driver is demonstrated proofing the increased achievable output power, which was measured greater than +0.1 dBm. This is approximately 11 dB higher than for a conventional CC driver. Furthermore, a concept is proposed, where the TP stage can act as a broadband matched driver for differential or balun operation ranging down to DC. As verification a broadband driver design using a class-AB TP stage is presented, which has a 3 dB bandwidth of 7.9 GHz and delivers up to +4.3 dBm into a 50 Ω load, which is 17 dB higher than its CC counterpart. At this output power it consumes a DC power of 12.3 mW and yields a PAE of 16.1%.

In this paper, we present a continuously tunable phase shifter realized in MEMS technology. Varactors with liquid crystal as a tunable dielectric layer underneath gold bridges are used to build a loaded line phase shifter. Measurements show that the phase shifter has a differential phase shift of 92°, a figure of merit (FoM) of 42°/dB and an input matching of −19 dB at 76 GHz.The tuning speed of the phase shifter is measured at different temperatures between 10 and 50°C. The realized phase shifter can be used in combination with MEMS switches in order to build a 360° tunable reflection phase shifter.

A new setup is proposed for the measurement of current–voltage pulsed characteristics of electron devices. The main advantages of the system consist in: shorter pulse widths through generation in a 50-Ω environment, simple average current monitoring through separation of the direct and alternate current paths, setting of average voltage values independently of pulse amplitudes and duty cycle, and stability of the setup guaranteed by wide-band dissipative terminations. The system is used for the characterization of dispersive effects due to carrier energy traps and thermal phenomena in GaAs and GaN on SiC field effect transistors. The basic differences between the two technologies are highlighted in the paper.

Millimeter-wave wireless space-division-multiplexing signals were discriminated by a newly developed electro-optic modulator using an array of antenna-coupled electrodes and polarization-reversed structures of ferroelectric optical crystals. Discrimination with channel isolation over 13 dB was obtained for two 38 GHz wireless signals with an irradiation angle difference of 15° by use of a fabricated device 30 mm in length.