Philipp Neumaier

245-GHz Transmitter Array in SiGe BiCMOS for Gas Spectroscopy

A 245-GHz transmitter (TX) array with an integrated antenna-array for a gas spectroscopy system has been realized. It consists of a push-push VCO with a 1/64 frequency divider, power amplifiers, frequency doublers, and on-chip antennas with localized backside etching. The TX-frequency is tunable in the range from 238 to 252 GHz. The TX-array has been fabricated in a 0.13- μm SiGe:C BiCMOS technology with f T /f max of 300 GHz/500 GHz. Its output power is approximately 7 dBm at 245 GHz, and the effective isotropically radiated power (EIRP) reaches 18 dBm at 245 GHz. The main components of the gas spectroscopy system are a TX and a receiver (RX) in SiGe BiCMOS as well as a gas absorption cell. The sensitivity of this spectroscopy system is demonstrated by measuring the high-resolution absorption spectrum of gaseous methanol ( CH3OH). Due to the increased power provided by the TX-array, the sensitivity of the spectrometer can be increased significantly.

245 GHz SiGe sensor system for gas spectroscopy

A 245 GHz sensor system for gas spectroscopy is presented, which includes a SiGe receiver (RX), a SiGe transmitter (TX), and a 0.6 m long gas absorption cell between the TX and RX. The integrated local oscillators of the RX and the TX are controlled by two external PLLs, whose reference frequencies are swept with constant frequency offset for a low IF of the RX. The RX consists of a differential LNA, an integrated 122 GHz local oscillator with 1/64 divider, a 90° differential hybrid, and active subharmonic mixer. The TX consists of an integrated 122 GHz local oscillator with 1/64 divider, and a frequency doubler. The RX and TX are fabricated in 0.13 µm SiGe BiCMOS with ft/fmax of 300GHz/500GHz. Using external dielectric lenses for the TX and RX, the absorption spectrum of gaseous methanol has been measured. The reference frequency of the TX-PLL is modulated for frequency-modulation spectroscopy. The performance of the sensor system is demonstrated by measuring the 2f absorption spectrum (second harmonic detection) of gaseous methanol.

245 GHz SiGe Transmitter Array for Gas Spectroscopy

A 245 GHz transmitter (TX) array with an integrated antenna-array for a gas spectroscopy system has been realized, which consists of a push-push VCO with a 1/64 frequency divider, power amplifiers, frequency doublers, and on-chip antennas with localized backside etching. The TX-frequency is tunable in the range from 238 GHz to 252 GHz. The TX-array is fabricated in 0.13 μm SiGe:C BiCMOS technology with fT/fmax of 300GHz/500GHz. Its estimated output power is 7 dBm at 245 GHz, and the EIRP reaches 18 dBm at 245 GHz. The 245 GHz spectroscopy system includes a TX and a receiver in SiGe. The sensitivity of this spectroscopy system is demonstrated by the high-resolution absorption spectrum of methanol and will be increased further by this TX-array.

Molecular Spectroscopy With a Compact 557-GHz Heterodyne Receiver

We report on a heterodyne terahertz spectrometer based on a fully integrated 557-GHz receiver and a digital fast Fourier transform spectrometer. The receiver consists of a chain of multipliers and power amplifiers, followed by a heterostructure barrier varactor tripler that subharmonically pumps a membrane GaAs Schottky diode mixer. All sub-components are newly developed and optimized with regard to the overall receiver performance such as noise temperature, power consumption, weight and physical size. The receiver works at room temperature, has a double sideband noise temperature as low as 2000 K at a maximum power consumption of 4.5 W with an Allan time of 10 s and a sideband gain ratio of 0.52. The performance of the spectrometer is demonstrated by absorption spectroscopy of H2O and CH3OH with an instantaneous bandwidth of 1.5 GHz and a resolution of 183 kHz. Several pressure broadening parameters of methanol absorption lines were determined, that agree with other published data. Using the experimentally determined molecular parameters the CH3OH absorption spectrum could be modeled with very high precision.

Sensor system in SiGe BiCMOS at 245 and 500 GHz for gas spectroscopy

This paper reviews our recent work on transmitter (TX) and receiver (RX) circuits in SiGe BiCMOS technology for gas spectroscopy in the frequency ranges around 245 GHz and 500 GHz. The 245 GHz TX consists of a 122 GHz local oscillator (LO) and a frequency doubler, and the 245 GHz RX consists of a low noise amplifier (LNA), a LO, and an active subharmonic mixer. A 245 GHz TX-array increases significantly the sensitivity of the sensor system. The 500 GHz system includes a TX-array, and a subharmonic RX with a transconductance mixer. The 500 GHz TX contains a frequency quadrupler, and the RX uses a frequency doubler for the LO. The LOs of the RX and the TX are controlled by two external phase-locked loops (PLLs). The reference frequency of the TX-PLL is frequency-modulated. The performance of the sensor system is demonstrated by using a gas absorption cell with dielectric lenses between the TX- and RX-modules, and measuring the 2f high-resolution absorption spectrum (second harmonic detection) of gaseous methanol (CH3OH) and acetonitrile (CH3CN).

Terahertz gas-sensors: Gas-phase spectroscopy and multivariate analysis for medical and security applications

This paper describes a spectroscopic system for gas sensing applications. It is based on SiGe transmitters (TXs) and receivers (RXs) operating at frequencies around 245 GHz and 500 GHz. 2f spectra of volatile organic compounds (VOCs) were obtained using wavelength modulation spectroscopy (WMS). Chemometrical analysis of the spectra is performed by applying several multivariate analysis (MVA) techniques.

Gas spectroscopy system at 245 and 500 GHz using transmitters and receivers in SiGe BiCMOS

A compact gas spectroscopy system is demonstrated, which contains a transmitter (TX) and a receiver (RX) in SiGe BiCMOS, as well as a gas absorption cell. The sensitivity of this spectroscopy system is demonstrated by measuring the high-resolution 2f absorption spectrum (second harmonic detection) of gaseous methanol (CH3OH) at 238-252 GHz, and at 495-497 GHz. The 245 GHz TX consists of a 120 GHz local oscillator (LO) and a frequency doubler, and the 245 GHz RX includes a low noise amplifier (LNA), a LO, and an active subharmonic mixer. A 245 GHz TX-array increases significantly the sensitivity of the sensor system. The 500 GHz system includes a TX-array, and a subharmonic RX with a transconductance mixer. The 500 GHz TX contains a frequency quadrupler, and the RX uses a frequency doubler for the LO. The LOs of the RX and the TX are controlled by two external phase-locked loops (PLLs).