M. De Dominicis

Miniaturized superconducting filter realized by using dual-mode and stepped resonators

In this paper, the design principles of a new miniaturized superconducting planar filter configuration is presented. The configuration is based on the combined use of dual-mode cross-slotted patch resonators and stepped resonators. Four-pole filters exhibiting a quasi-elliptical response and with operating frequencies in K-, L-, and C-bands have been designed as a test vehicle of the new configuration. The analyzed topology exhibits a high degree of miniaturization, requiring less than 50% of the area occupied by filters based on dual-mode or hairpin resonators. The physical origin of the transmission zeros is discussed, deriving equivalent-circuit descriptions that are capable of reproducing the measured frequency response. In order to confirm the validity of the introduced design principles, experimental performances on an exemplary L-band filter, realized using a YBCO film deposited on an MgO substrate and exhibiting a 3% fractional bandwidth, are presented. The measured frequency response obtained at T = 77 K agrees well with the simulations, presenting an insertion loss of 0.1 dB and a power handling of 34 dBm.

High Power Microstrip GaN-HEMT Switches for Microwave Applications

In this paper the design, fabrication and test of X-band and 2-18 GHz wideband high power SPDT MMIC switches in microstrip GaN technology are presented. Such switches have demonstrated state-of-the-art performances. In particular the X-band switch exhibits 1 dB insertion loss, better than 37 dB isolation and a power handling capability at 9 GHz of better than 39 dBm at 1 dB insertion loss compression point; the wideband switch has an insertion loss lower than 2.2 dB, better than 25 dB isolation and a power handling capability of better than 38 dBm in the entire bandwidth.

A novel impedance pattern for fast noise measurements

Complete noise characterization of an active device implies the extraction of the minimum noise figure (F/sub min/), noise resistance (R/sub n/), and optimum value of the complex input reflection coefficient (/spl Gamma//sub opt/). Such quantities can be obtained through a minimum of four noise figure measurements, associated to four different reflection coefficients at the input of the DUT, (/spl Gamma//sub in,k/ k = 1 /spl middot/ /spl middot/ /spl middot/ 4), forming an impedance pattern. Measurement redundancy is usually required to reduce overall uncertainty, therefore forcing one to use, for the synthesis of a large number of different terminations, an impedance tuner. This paper introduces a novel four-points input pattern, which becomes an optimum trade-off between accuracy and complexity, while avoiding the use of a tuner: a drastic reduction in cost and complexity of the measurement bench therefore results.