MILLIMETER-WAVE SOURCES MEASUREMENT AND QUALIFICATION FACILITY

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. ACERT presently possesses 5 c.w. and 1 pulsed millimeter-wave sources, ranging in output power from approximately 1mW to 1.2KW. During the course of the Center grant period, we have increasingly required qualification, maintenance, and calibration services for these sources. To this end, we have assembled test and measurement instrumentation necessary to accomplish this task, and have established a regimen for applying these tools to it. The fundamental measurements are power, wavelength/frequency, spectral characteristics (including noise power) and, for pulse devices, temporal response. To address these needs, a test area has been set aside where the necessary measurement setups may be faithfully and quickly reproduced. For our quasioptical power measurements, we rely on a Thomas Keating Ltd. "TK TeraHertz" incident power meter system, with an absolute calibration accuracy of approximately 20% when corrected for wavelength and beam profile. Frequency and spectral characteristics are measured by means of a Tektronix model 492 spectrum analyzer, using a set of calibrated harmonic waveguide detectors covering 20 through 325 GHz. Because the TK power meter is relatively insensitive to wavelength, it produces a calibrated power measurement which is not highly sensitive to nor revealing with respect to the actual operating frequency. The spectrum analyzer, on the other hand, produces a relatively accurate measurement of the operating frequency and good qualitative measurement of the actual output spectrum, but is poorly calibrated with respect to absolute power at a given frequency. Between the two measurement systems, however, a good complementary measurement of power, wavelength/frequency and spectral characteristics is achievable. Temporal response is measured either by direct observation of an appropriate waveguide harmonic mixer output in detector mode, or indirectly, by interpretation of the frequency-domain spectrum observed with the spectrum analyzer.