We describe the design and measured performance of a 5 mm x 5 mm x 1.37 mm antenna duplexer for the U.S. PCS band (Tx: 1850-1910 MHz, Rx: 1930-1990 MHz) for cellular handsets based on FBAR (Film Bulk Acoustic Resonator) technology. The FBARs are fabricated in a silicon-based IC process technology and are hermetically sealed in a wafer-level packaging process. Two dice, Tx and Rx, are attached to a 4-level printed circuit board, ballbonded, and encapsulated in plastic to form the final product. Guaranteed worst-case Tx insertion loss is 3.5 dB, worst-case Rx insertion loss is 4.0 dB. Minimum rejection is 50/40 dB in the Tx/Rx bands, guaranteed isolation is >52/42 dB.

Superconducting tunnel junctions coupled to superconducting absorbers may be used as high-resolution, high-efficiency x-ray spectrometers. We have tested devices with niobium x-ray absorbing layers coupled to aluminum layers that serve as quasiparticle traps. The energy resolution at 6 keV was 49 eV full width at half-maximum. We estimate that each quasiparticle tunnels an average of 19 times before recombining, increasing the total charge transferred and therefore decreasing the effects of electronic noise.

We present the first experimental results obtained using a cryogenically‐cooled Nb–Al2O3–Nb superconductor–insulator–superconductor (SIS) tunnel junction detector operating at 1.3 K as an ion detector in a time‐of‐flight mass spectrometer. As opposed to microchannel‐plate ion detectors (MCPs) commonly used in such systems, cryogenic detectors such as SIS detectors offer a near 100% detection efficiency for all ions including single, very massive, slow‐moving macromolecules. We describe the operating principle of an SIS detector and its use as an ion detector in our matrix‐assisted laser desorption/ionization (MALDI) time‐of‐flight mass spectrometer and compare its response to an MCP detector operated in the same system. To our knowledge, this is the first direct comparison of these detector types in this application. A comparison of count rates and time‐of‐flight spectra obtained with both detectors for human serum albumin (molecular weight 66 000 Da) indicates a two to three orders of magnitude higher detection efficiency per unit area for the SIS detector at this mass. For higher molecular masses we expect an even higher relative efficiency for cryogenic detectors since MCPs show a rapid decline in detection efficiency as ion mass increases, which is not expected to be the case for cryogenic detectors. Our results imply that time‐of‐flight techniques could be extended beyond the current upper mass limit if cryogenic detectors are used. Initially, cryogenic detectors will be used for the analysis of large protein molecules. If non‐fragmenting ionization techniques can be perfected, cryogenic detectors will also open the possibility of the rapid analysis of large DNA molecules and perhaps intact microorganisms.

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We present experimental results obtained with a cryogenically cooled, high-resolution x-ray spectrometer based on a 141 μm×141 μm Nb-Al-Al2O3-Al-Nb superconducting tunnel junction (STJ) detector in a demonstration experiment. Using monochromatized synchrotron radiation we studied the energy resolution of this energy-dispersive spectrometer for soft x rays with energies between 70 and 700 eV and investigated its performance at count rates up to nearly 60 000 cps. At count rates of several 100 cps we achieved an energy resolution of 5.9 eV (FWHM) and an electronic noise of 4.5 eV for 277 eV x rays (the energy corresponding to C K). Increasing the count rate, the resolution 277 eV remained below 10 eV for count rates up to ∼10 000 cps and then degraded to 13 eV at 23 000 cps and 20 eV at 50 000 cps. These results were achieved using a commercially available spectroscopy amplifier with a baseline restorer. No pile-up rejection was applied in these measurements. Our results show that STJ detectors can operate at count rates approaching those of semiconductor detectors while still providing a significantly better energy resolution for soft x rays. Thus STJ detectors may prove very useful in microanalysis, synchrotron x-ray fluorescence (XRF) applications, and XRF analysis of light elements (K lines) and transition elements (L lines).