The recent discovery of high-temperature superconductors (HTS's) 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. In this paper, two methods for feeding HTS microstrip antennas at K and Ka-band are examined. Superconducting microstrip antennas that are directly coupled and gap-coupled to a microstrip transmission line have been designed and fabricated on lanthanum aluminate substrates using Y-Ba-Cu-0 superconducting thin films. Measurements from these antennas, including input impedance, bandwidth, efficiency, and patterns, are presented and compared with published mdels. 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.

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The direct detection of nitroglycerine, ethylene glycol dinitrate, and dinitrotoluene by optoacoustic spectroscopy techniques at 6 microm, 9 microm, and 11 microm is reported. The effect of interference by normal atmospheric pollutants is investigated, and it is found that of those wavelengths used in this investigation the 9-microm and 11-/microm spectral regions, using a CO(2) laser as radiation source, are the most promising for use in explosive detection.

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Using a pulsed dye laser and a nonresonant optoacoustic detector, the absorption spectrum of NO(2) has been measured in the spectral region of 480-625 nm at various cell pressures and at various concentrations in air. The results of the measurements as a function of NO(2) concentration in air demonstrate the detection capability of the system. An extrapolated sensitivity of 4 ppb NO(2)/W of laser power has been achieved.