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In this paper, we report on the fabrication and testing of a superconducting miniaturized filter integrated with a low-noise amplifier (LNA), in a single metallic packaging. The superconducting L-band filter is based on the combined use of dual-mode cross-slotted patch resonators and stepped resonators, and is able to offer a good trade-off between compactness and power handling. As far as the LNA is concerned, a two-stage single-ended configuration is proposed, providing a gain of 28 dB with a flatness of about ± 0.5 dB all over the bandwidth (15% centred around 2.15 GHz). A double bias scheme has been adopted (separate gate and drain biases) and great care has been taken to ensure stable performances under all possible operating load conditions, therefore ensuring unconditional stability of the amplifying stages. The LNA noise figure at room temperature has been estimated to be under 0.6 dB over the entire operating bandwidth. A superconducting filter integrated with an LNA has been assembled in a single copper package, exhibiting a total space occupation of (40 × 25) mm2. The final performances have been tested at T = 77 K, showing a gain of about 30 dB and minimum noise figure of 0.47 dB.

In this paper the performances of superconducting devices based on fractal layout are discussed. Depending on their shape, fractals are characterized by self-similarity and/or space-filling properties. The former allows the design of superconducting filters with highly reduced dimensions and no appreciable loss of performance, whereas the latter is the basis for the fabrication of multi-band antennas which hold promise for very interesting applications. Our attention was focused on the square Koch loop and the Sierpinski gasket geometries. In particular, prototype four pole filters for UMTS (Universal Mobile Telecommunications Systems) applications based on Koch resonators have been designed. Measurements performed on prototype devices fabricated by using double-sided superconducting thin films are reported and compared with simulations.

In high-temperature superconducting (HTS) microwave filters, the requirements for miniaturization and high power handling are difficult to match simultaneously. In this paper, we report on the design and realization of HTS filters realized by combining dual-mode cross-slotted and stepped resonators in order to obtain a compact size and a relatively high power handling. Prototype HTS four-pole filters operating in C-band and L-band, with quasi-elliptical responses, on both MgO and LaALO3 substrates, have been designed and tested at T = 77 K. The filters present a high degree of miniaturization as they save more than 50% of the area compared with those realized with dual-mode and/or hairpin resonators. The measured responses agree well with the simulation even if the in-band ripple should be optimized. As far as the power handling is concerned, the C-band filter grown on LaAlO3 presents a power handling of Pin = 20 dBm limited by the power handling of the dual-mode cross-slotted resonator, while we have observed no power degradation in the L-band filter grown on MgO up to Pin = 33 dBm limited by power supply.

The use of high-temperature superconducting films for the fabrication of antennas allows us to realize radiating structures that are small in size and have a very high efficiency. In this paper, we investigate the properties of a novel compact antenna obtained by crossing a square patch with diagonal and transverse slots. Single patch antennas, with both linear and circular polarization operating in the X-band, with a size reduction of about 40% as compared to conventional square patches, have been designed and tested at prototype level. They have been realized by using double-sided YBa2Cu3O7−x(YBCO) and Tl2Ba2Ca1Cu2O8(Tl-2212) superconducting films grown on MgO substrates and have been measured using a portable cryocooler. At T = 77 K, the experimental scattering parameter, S11, agrees well with simulations, showing a power handling of 23 dBm for YBCO devices. The miniaturized patch antenna investigated has allowed us to realize a 4 × 4 array of linear polarization antennas at 11.5 GHz, using a YBCO film grown on a MgO substrate with a 2'' diameter, by considering a reduced interspace (more than 20%) between the elements. The far-field pattern and the 16-array gain are in good agreement with the simulated results.