M.A. Richard

Superconducting microstrip antennas: an experimental comparison of two feeding methods

The recent discovery of high-temperature superconductors (HTSs) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS causes difficulty in feeding such antennas because of the high patch edge impedance. Two methods for feeding HTS microstrip antennas at K- and Ka-band are examined. Superconducting microstrip antennas that are directly coupled and gas-coupled to a microstrip transmission line have been designed and fabricated on lanthanum aluminate substrates using Y-Ba-Cu-O superconducting thin films. Measurements from these antennas, including input impedance, bandwidth, efficiency, and patterns, are presented and compared with published models. The measured results demonstrate that usable antennas can be constructed using either of these architectures, although the antennas suffer from narrow bandwidths. In each case, the HTS antenna shows a substantial improvement over an identical antenna made with normal metals. >

Performance of TlCaBaCuO 30 GHz 64 element antenna array

A 64-element, 30-GHz microstrip antenna array with corporate feed network was designed and built on a 0.254-mm (10-mil) thick lanthanum aluminate substrate. One antenna pattern was fabricated from gold film, and a second pattern used TlCaBaCuO high-temperature superconductor. Both antennas used gold ground planes deposited on the reverse side of the substrate. Gain and radiation patterns were measured for both antennas at room temperature and at cyrogenic temperatures. Observations agree well with simple models for loss and microwave beam width, with a gain on boresight of 20.3 dB and beam width of 15 degrees for the superconducting antenna. The antenna loss is only 1.9 dB.<<ETX>>

Performance of a four-element Ka-band high-temperature superconducting microstrip antenna

Superconducting four-element microstrip array antennas operating at 30 GHz have been designed and fabricated on a lanthanum aluminate (LaAlO/sub 3/) substrates. The experimental performance of these thin-film Y-Ba-Cu-O superconducting antennas is compared with that of an identical antenna patterned with evaporated gold. Efficiency measurements of these antennas show an improvement of 2 dB at 70 K and as much as 3.5 dB at 40 K in the superconducting antenna over the gold antenna.<<ETX>>

A 10 GHz Y-Ba-Cu-O/GaAs hybrid oscillator proximity coupled to a circular microstrip patch antenna

A 10-GHz hybrid Y-Ba-Cu-O/GaAs microwave oscillator proximity coupled to a circular microstrip antenna has been designed, fabricated, and characterized. The oscillator was a reflection mode type using a GaAs MESFET as the active element. The feedline, transmission lines, RF chokes, and bias lines were all fabricated from YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting thin films on a 1-cm*1-cm lanthanum aluminate substrate. The output feedline of the oscillator was wire bonded to a superconducting feedline on a second 1 cm*1 cm lanthanum aluminate substrate, which was in turn proximity coupled to a circular microstrip patch antenna. Antenna patterns from this active patch antenna and the performance of the oscillator measured at 77 K are reported. The oscillator had a maximum output power of 11.5 dBm at 77 K, which corresponded to an efficiency of 10%. In addition, the efficiency of the microstrip patch antenna together with its high temperature superconducting feedline was measured from 85 K to 30 K and was found to be 71% at 77 K, increasing to a maximum of 87.4% at 30 K.<<ETX>>

Design of an optically controlled Ka-band GaAs MMIC phased-array antenna

Phased array antennas long were investigated to support the agile, multibeam radiating apertures with rapid reconfigurability needs of radar and communications. With the development of the Monolithic Microwave Integrated Circuit (MMIC), phased array antennas having the stated characteristics are becoming realizable. However, at K-band frequencies (20 to 40 GHz) and higher, the problem of controlling the MMICs using conventional techniques either severely limits the array size or becomes insurmountable due to the close spacing of the radiating elements necessary to achieve the desired antenna performance. Investigations were made that indicate using fiber optics as a transmission line for control information for the MMICs provides a potential solution. By adding an optical interface circuit to pre-existing MMIC designs, it is possible to take advantage of the small size, lightweight, mechanical flexibility and RFI/EMI resistant characteristics of fiber optics to distribute MMIC control signals. The architecture, circuit development, testing and integration of optically controlled K-band MMIC phased array antennas are described.

Optical control of an 8-element Ka-band phased array antenna using a high-speed optoelectronic interconnect

Optical distribution of control signals in electronically steered phased array antennas is considered. A demonstration experiment in which a high-speed hybrid GaAs optoelectronic integrated circuit (OEIC) was used to control a 28.2 GHz eight-element phased-array antenna is described. The OEIC, which accepts a serial optical control signal as input and converts it to 16 demultiplexed parallel outputs, was used to control the monolithic GaAs phase shifters of a Ka-band patch panel array antenna. Antenna pattern switching speeds of 2.25 mu s, limited by interface circuitry, were observed.<<ETX>>

Performance of a K-band superconducting gap-coupled microstrip antenna

Superconducting circular gap-coupled antennas at 26 GHz have been designed and fabricated on lanthanum aluminate substrate using a YBCO high-temperature superconducting thin film. The efficiencies and far-field antenna patterns have been measured and are compared with an identical antenna patterned with gold. The experimental far-field patterns agree well with published models, and efficiency measurements show a maximum improvement of 9% at 20 K in the efficiency of the HTSC antenna when compared to the gold antenna at the same temperature. Surface wave efficiency approximations show that the performance of these antennas is limited by surface wave losses.<<ETX>>

A Ka-band electromagnetically-coupled superconducting microstrip antenna

Summary form only given. One of the drawbacks of using HTS (high-temperature superconductor) for microstrip antennas, is the fact that HTS is unavailable on low-permittivity substrates. The use of a high-permittivity substrate for microstrip antennas leads to undesirable characteristics such as narrow bandwidth and reduced radiation efficiency due to surface wave generation. To overcome this difficulty and effectively use HTS in microstrip antenna systems, a two-layered electromagnetically coupled microstrip patch has been investigated. This configuration allows the patch to be patterned with gold on a lower permittivity substrate while still using HTS for the feed network.<<ETX>>

A 4-element superconducting microstrip array

A superconducting 4-element microstrip array antenna operating at 30 GHz has been designed and fabricated on a lanthanum aluminate (LaAlO/sub 3/) substrate. The experimental performance of this thin-film Y-Ba-Cu-O superconducting antenna is compared with that of an identical antenna patterned with evaporated gold. Antenna patterns show good agreement with predicted patterns, and efficiency measurements of these antenna show an improvement of 2 dB at 70 K in the superconducting antenna over the gold antenna.<<ETX>>

Performance of a 300-mb/s 1:16 serial/parallel optoelectronic receiver module

Optical interconnects are being considered for the high speed distribution of multiplexed control signals in GaAs MMIC-based phased array antennas. This paper describes the performance of a hybrid GaAs optoelectronic integrated circuit (OEIC), along with a description of its design and fabrication. The OEIC converts a 16-bit serial optical input to a 16 parallel line electrical output using an on-board 1:16 demultiplexer and operates at data rates as high as 305 Mbps. The performance characteristics as well as potential applications of the device are presented.