Terahertz components and devices are typically interfaced with measurement instrumentation and characterized using fixtures equipped with waveguide flanges or antennas. Such fixtures are known to introduce significant uncertainty and error in measurements. It is preferable to characterize such devices in-situ,
where the device under test can be measured on-wafer, prior to dicing and separately from the circuit housing to which it is ultimately affixed. This is commonly done in the RF and millimeter-wave region with a probe station equipped with coplanar launchers. Commercial coplanar waveguide probes have generally been available to the WR-2.2 band (325—500 GHz) but few options currently exist for on-wafer measurements
above these frequencies. This paper describes recent work at the University of Virginia and Dominion Microprobes, Inc. to extend on-wafer measurement capabilities to terahertz frequencies through the design and implementation of coplanar probes based on silicon micromachining. At present micromachined on-wafer probes operating to WR1.2 (600 to 900 GHz) have been demonstrated and exhibit typical insertion losses lower than 7 dB with return loss of 15 dB or greater over a full waveguide band.
PAPPA is a balloon-based experiment designed to measure the polarization of the Cosmic Microwave Background using candidate technology for an eventual Einstein Inflation Probe mission. It will survey a 20° × 20° patch of sky with 0.5° angular resolution covering 3 passbands centered at 89, 212 and 302 GHz. Detection will be accomplished via antenna-coupled transition edge sensors (TESs) with SQUID-based readouts. In the eventual flight package, band defining filters and MEMS-based polarization modulators will be incorporated into the superconducting microstrip transmission lines that terminate in resistors that are thermally coupled to the TESs. The MEMS switches will allow on-chip polarization modulation that is faster than significant detector gain variations. The initial configuration will incorporate a simplified focal plane augmented by quasioptical polarization modulation. We describe the overall instrument design and present a summary of the current progress.
This paper presents the design of a millimeter-wave Fourier transform spectrometer based on microstrip transmission line circuits and PIN diode switches. The working frequency for this design is in the range of 40-70 GHz which is potentially useful for measurement of absorption spectra of biological materials. Simulation results demonstrate the feasibility of this design and indicate that a frequency resolution of 6 GHz is achievable.
This paper presents the concept of an integrated millimeter-wave Fourier transform spectrometer. It is proposed to integrate the interferometer through the use of planar transmission line circuits onto a single chip. The splitting and combining of the broadband signal can be realized through the use of coupled-line couplers and
the sliding reflector can be realized with distributed RF-MEMS transmission lines. Calculations are given to demonstrate the feasibility of this concept.
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