The fabrication and characterisation of surface acoustic wave resonators operating in the gigahertz frequency range are presented. The devices were fabricated on thin AlN layers deposited by magnetron sputtering on high resistivity (100) oriented silicon substrates. Using direct writing e-beam lithography, well defined interdigital transducers with 300 nm finger width and spacing have been obtained. On-wafer microwave measurements have demonstrated a narrow bandstop frequency characteristic with high rejection at approximately 5 GHz and an electromechanical coupling coefficient of 0.53%.

This paper reports on a GaN/Si surface acoustic wave (SAW) impedance element filter operating in the few gigahertz region. The PI-type filter consists of three SAW resonators with the same digit/interdigit widths, integrated with series/parallel planar inductors. The design procedure is based on modeling the SAW resonators using four parameters, independent of the equivalent circuit model representation (series resonance frequency, static capacitance, quality factor, and effective coupling coefficient). The series frequency is tuned by a planar inductor placed in series, while the parallel resonant frequency is tuned by a planar inductor placed in parallel with the SAW resonator. Closed-form equations are derived for the analysis of lumped-element SAW resonators. The design procedure is further based on the area of the SAW resonator and the lengths of the planar inductors as independent variables. Full-wave electromagnetic and circuital co-simulations and parametric optimizations are employed for the final filter design, which is implemented in the coplanar waveguide topology. The lumped-element SAW bandpass filter is fabricated using e-beam lithography for the definition of the 200-nm-wide interdigital transducers. Measurement results show the insertion losses of 12.9 dB at 5.49 GHz, the return losses of 16 dB, 3-dB bandwidth of 8.3 MHz, and the out-of-band rejection of 24 dB. The filter is compatible with monolithic integration with GaN active electronics.

This paper presents the fabrication processes for micromachined millimetre-wave devices, on two different types of semiconductor substrates. The first process uses micromachining on high-resistivity < 100> oriented silicon. A three-layer dielectric membrane, with a total thickness of 1.5 µm is used as support for the millimetre-wave structures. This process was used for the manufacturing of two coupled line filters, with central operating frequencies of 38 and 77 GHz, respectively. The second process is based on GaAs micromachining. For the first time, a 2.2 µm thin GaAs/AlGaAs membrane, obtained by molecular beam epitaxy growth and micromachining of semi-insulating < 100> GaAs, is used as a support for millimetre-wave filter structures. Cascaded coplanar waveguide open-end series stubs filter type structures, with central frequencies of 38 and 77 GHz, respectively, were designed and manufactured on a GaAs micromachined substrate. `On wafer' measurements for the filter structures were performed. Losses of less than 1.5 dB at 38 GHz and less than 2 dB at 77 GHz have been obtained for both the silicon as well as for the GaAs-based micromachined filters.

This letter presents a novel monolithic integrated frequency multiplier circuit for free space power generation in the ${W}$ -band (75–110 GHz). The circuit is based on a submicrometer GaAs Schottky diode monolithically integrated with a slot antenna on a GaAs semi-insulating substrate. The fabricated diode with an air-bridged Schottky contact and a U-shaped ohmic contact showed an ideality factor of about 1.25 and a zero bias cutoff frequency higher than 1.25 THz. Using input signals between 15 and 50 GHz, the free space power generated in the ${W}$ -band corresponding to $\times 2$ , $\times 3$ , $\times 4$ , and $\times 5$ frequency multiplication was measured and showed minimum isotropic conversion losses (with antenna) of 11.5, 16.9, 23.7, and 26.4 dB, respectively.

This paper addresses the design and modeling of millimeter wave tunable filters using CoPlanar Waveguide (CPW) quarter wavelength stubs and MEMS (Micro-Electro-Mechanical-Systems) switches. In order to design bandstop and bandpass tunable MEMS filters an accurate design methodology based on the transmission line theory is presented. The tunable behavior is achieved using original MEMS switches: Two Cantilever Shunt Switch (TCSS). The overall structures, including TCSS, have been manufactured using dielectric membrane, in order to minimize the insertion losses. The obtained simulation and experimental results confirm the accuracy of the proposed design methodology and indicates very good performances in millimeter wave band.