James P. McMillan

85-to-127 GHz CMOS transmitter for rotational spectroscopy.

A transmitter for rotational spectroscopy using a fractional-N PLL (FNPLL) that generates frequency shift keyed signals from 85 to 127 GHz (39% tuning range) with a fine frequency step of ~570 Hz and settling time of ~10 μS is demonstrated. Implemented in 65-nm CMOS, the FNPLL delivers greater than 5 μW of output power, and achieves measured phase noise of less than -70 dBc/Hz in-band and less than -102 dBc/Hz at 10-MHz offset over the output frequency range while consuming 80 mW. The transmitter output is radiated using a bond-wire antenna and successfully utilized in a spectrometer for detection of gas molecules.

The Complete, Temperature Resolved Experimental Spectrum of Methanol (CH3OH) between 214.6 and 265.4 GHz

The spectrum of methanol (CH{sub 3}OH) has been characterized between 214.6 and 265.4 GHz for astrophysically significant temperatures. Four hundred and eighty-six spectra with absolute intensity calibration recorded between 240 and 389 K provided a means for the calculation of the complete experimental spectrum (CES) of methanol as a function of temperature. The CES includes contributions from v{sub t} = 3 and other higher states that are difficult to model quantum mechanically (QM). It also includes the spectrum of the {sup 13}C isotopologue in terrestrial abundance. In general the QM models provide frequencies that are within 1 MHz of their experimental values, but there are several outliers that differ by tens of MHz. As in our recent work on methanol in the 560-654 GHz region, significant intensity differences between our experimental intensities and cataloged values were found. In this work these differences are explored in the context of several QM analyses. The experimental results presented here are analyzed to provide a frequency point-by-point catalog that is well suited for the simulation of crowded and overlapped spectra. Additionally, a catalog in the usual line frequency, line strength, and lower state energy format is provided.

200–280GHz CMOS RF front-end of transmitter for rotational spectroscopy

A 200-280 GHz RF front-end of transmitter is demonstrated in 65-nm CMOS. Saturated EIRP is greater than -5dBm over a frequency range of 60GHz. When the input power is -20dBm, EIRP is greater than -10dBm for most of the frequency range, and achieves 3-dB and 6-dB bandwidths of 24% and 33%. The front-end was integrated with a fractional-N synthesizer to form a transmitter operating at 208-255GHz with EIRP of -18 to -11dBm. The transmitter and a CMOS receiver are used for rotational spectroscopy and to detect ethanol in human breath.

225–280 GHz receiver for rotational spectroscopy

A fully integrated CMOS receiver for mm-wave rotational spectroscopy is demonstrated. The receiver consists of a sub-harmonic mixer based receiving front-end which down-converts 225-280 GHz RF input to 20 GHz intermediate frequency, a 20-GHz AM demodulator followed by a baseband buffer amplifier, and an 122-139 GHz local oscillator chain which is comprised of a frequency quadrupler and a driver amplifier. The receiver exhibits responsivity of 400-1200 kV/W and noise equivalent power of 0.4 to 1.2 pW/√Hz from 225 to 280 GHz. Detection of ethanol, propionitrile (EtCN), acetonitrile (CH3CN) and acetone in a mixture is demonstrated using the receiver in a rotational spectrometer setup. This is the first demonstration that a CMOS receiver can be used for rotational spectroscopy and that a CMOS circuit can support an existing application at frequencies above 200 GHz.

Devices and circuits in CMOS for THz applications

Recent advances of CMOS technology and circuits have made it an alternative for realizing capable and affordable THz systems. With process and circuit optimization, it should be possible to generate useful power and coherently detect signals at frequencies beyond 1THz, and incoherently detect signals at 40THz in CMOS.

THE COMPLETE, TEMPERATURE RESOLVED EXPERIMENTAL SPECTRUM OF METHYL FORMATE (HCOOCH3) BETWEEN 214.6 AND 265.4 GHz

Because methyl formate (HCOOCH3) is abundant in the interstellar medium and has a strong, complex spectrum, it is a major contributor to the list of identified astrophysical lines. Because of its spectral complexity, with many low lying torsional and vibrational states, the quantum mechanical (QM) analysis of its laboratory spectrum is challenging and thus incomplete. As a result it is assumed that methyl formate is also one of the major contributors to the lists of unassigned lines in astrophysical spectra. This paper provides a characterization, without the need for QM analysis, of the spectrum of methyl formate between 214.6 and 265.4 GHz for astrophysically significant temperatures. The experimental basis for this characterization is a set of 425 spectra, with absolute intensity calibration, recorded between 248 and 408 K. Analysis of these spectra makes possible the calculation of the Complete Experimental Spectrum of methyl formate as a function of temperature. Of the 7132 strongest lines reported in this paper, 2523 are in the QM catalogs. Intensity differences of 5%–10% from those calculated via QM models were also found. Results are provided in a frequency point-by-point catalog that is well suited for the simulation of overlapped spectra. The common astrophysical line frequency, line strength, and lower state energy catalog is also provided.

The complete, temperature resolved spectrum of methyl cyanide between 200 and 277 GHz

We have studied methyl cyanide, one of the so-called ‘astronomical weeds’, in the 200–277 GHz band. We have experimentally gathered a set of intensity calibrated, complete, and temperature resolved spectra from across the temperature range of 231–351 K. Using our previously reported method of analysisa, the point by point method, we are capable of generating the complete spectrum at astronomically significant temperatures. Lines, of nontrivial intensity, which were previously not included in the available astrophysical catalogs have been found. Lower state energies and line strengths have been found for a number of lines which are not currently present in the catalogs. The extent to which this may be useful in making assignments will be discussed.

Spectroscopic fits to the alma science verification band 6 survey of the orion hot core and compact ridge

SATYAKUMAR NAGARAJAN, JAMES P. McMILLAN, Department of Physics, The Ohio State University, Columbus, OH, USA; ANDREW M BURKHARDT, Department of Astronomy, The University of Virginia, Charlottesville, VA, USA; CHRISTOPHER F. NEESE, FRANK C. DE LUCIA, Department of Physics, The Ohio State University, Columbus, OH, USA; ANTHONY REMIJAN, ALMA, National Radio Astronomy Observatory, Charlottesville, VA, USA.

THE COMPLETE, TEMPERATURE RESOLVED SPECTRUM OF METHANOL BETWEEN 214 AND 265 GHZ

We have studied methanol, one of the so-called ‘astronomical weeds’, in the 215–265 GHz band. We have gathered a set of intensity calibrated, complete, experimental, and temperature resolved spectra from across the temperature range of 240–389 K. A number of low lying transitions, including the νt = 3 , have not been produced by available catalogs. Using our previously reported method of analysisa we were able generate a line list that contains lower state energies and linestrengths, for all of the observed lines in the band. This line list includes those lines which have no quantum mechanical assignment. In addition to this line list we provide a point by point method capable of generating the complete spectrum at an arbitrary temperature. The sensitivity of the point by point analysis is such that we are able to identify lines which would not have manifest in a single scan across the band. The consequence has been to reveal not only a number of new methanol lines, but also trace amounts of contaminants. We show how the intensities from the contaminants can be removed with indiscernible impact on the signal from methanol. To do this we use the point by point results from our previous studies of these contaminants. The efficacy of this process serves as strong proof of concept for usage of our point by point results on the problem of the weeds. The success of this approach for dealing with the weeds has also previously been reportedb.