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Softwaretechnik-Trends

NOISE AND RF BANDWIDTH MEASUREMENTS OF A 1.2 THz HEB HETERODYNE RECEIVER

Anders J. Skalare, William R. McGrath, B. Bumble, Henry George LeDuc

Published Jan 1, 1997• 4 citations
OpenAlex

Abstract

Receiver noise and RF coupling bandwidth have been measured for a quasioptically coupled diffusion-cooled hot-electron bolometer mixer at a local oscillator frequency of 1267 GHz and an intermediate frequency of 1.4 GHz. A lowest receiver equivalent noise temperature of 1880 K double-sideband was measured, with an upper limit for the mixer noise temperature of 950 K double-sideband. The amount of absorbed local oscillator power in the bolometer device was approximately 6 nW. The effective instantaneous RF bandwidth measured with a Fourier transform spectrometer was 730 GHz.

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The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The best results of the DSB noise temperature at 1.5 GHz IF frequency obtained with one device are: 1300 K at 650 GHz, 4700 K at 2.5 THz and 10000 K at 3.12 THz. The measurements were performed at 4.5 K ambient temperature. The amount of local oscillator (LO) power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain measured at 650 GHz is -9 dB, the total conversion gain is -14 dB.

IEEE Transactions on Applied Superconductivity•Jun 1, 1999•6 citations
Receiver noise and RF coupling bandwidth have been measured for a quasioptically coupled diffusion-cooled hot-electron bolometer mixer at a local oscillator frequency of 1267 GHz and an intermediate frequency of 1.4 GHz. A lowest receiver equivalent noise temperature of 1880 K double-sideband was measured, with an upper limit for the mixer noise temperature of 950 K double-sideband. The amount of absorbed local oscillator power in the bolometer device was approximately 6 nW. The effective instantaneous RF bandwidth measured with a Fourier transform spectrometer was 730 GHz.
Diffusion-cooled Nb hot-electron bolometer (HEB) mixers have the potential to simultaneously achieve high intermediate frequency (IF) bandwidths and low mixer noise temperatures for operation at THz frequencies (above the superconductive gap energy). We have measured the IF signal bandwidth at 630 GHz of Nb devices with lengths L = 0.3, 0.2, and 0.1 micrometer in a quasioptical mixer configuration employing twin-slot antennas. The 3-dB EF bandwidth increased from 1.2 GHz for the 0.3 gm long device to 9.2 GHz for the 0.1 gm long device. These results demonstrate the expected 1/L squared dependence of the IF bandwidth at submillimeter wave frequencies for the first time, as well as the largest EF bandwidth obtained to date. For the 0.1 gm device, which had the largest bandwidth, the double sideband (DSB) noise temperature of the receiver was 320-470 K at 630 GHz with an absorbed LO power of 35 nW, estimated using the isothermal method. A version of this mixer with the antenna length scaled for operation at 2.5 THz has also been tested. A DSB receiver noise temperature of 1800 plus or minus 100 K was achieved, which is about 1,000 K lower than our previously reported results. These results demonstrate that large EF bandwidth and low-noise operation of a diffusion-cooled HEB mixer is possible at THz frequencies with the same device geometry.
We report receiver noise temperature measurements using a quasioptically coupled diffusion-cooled hot-electron bolometer mixer at a local oscillator frequency of 1267 GHz, and an intermediate frequency of 1.4 GHz. A best double-sideband (DSB) receiver noise temperature of 1880 K was measured, with an estimated mixer noise of 945 K (DSB), and a conversion efficiency including coupling losses of -19 dB (DSB). The coupled local oscillator power requirement for this device is estimated at roughly 6 nW. The mixer noise temperature is less than twice that measured earlier in a waveguide receiver at 530 GHz, which shows that the sensitivity of this type of mixer does not degrade sharply with increasing frequency in this regime.
Superconductive hot-electron bolometer (HEB) mixers have been built and tested in the frequency range from 1.1 THz to 2.5 THz. The mixer device employs diffusion as a cooling mechanism for hot electrons. The double sideband receiver noise temperature was measured to be approximately equals 2750 K at 2.5 K at 2.5 THz; and mixer IF bandwidths as high as 9 GHz are achieved for 0.1 micrometers long devices. The local oscillator power dissipated in the HEB microbridge was in the range 20- 100 nW. Further reductions in LO power and mixer noise can be potentially achieved by using Al microbridges. The advantages and parameters of such devices are evaluated. A distributed-temperature model has been developed to properly describe the operation of the diffusion-cooled HEB mixer. The HEB mixer is a primary candidate for ground based, airborne and spaceborne heterodyne instruments at THz frequencies.
In this paper we report receiver sensitivity measurements with a diffusion-cooled niobium hot-electron bolometer around 1100 GHz. The lowest receiver noise temperature was 1670 K DSB, with approximately 40 nW of local oscillator power being dissipated in the device. The intermediate frequency bandwidth of this device, due to its short length (0.15 gm) and low normal resistance (43 a), exceeded the 1.8 GHz bandwidth of the measurement setup. The receiver was used to detect the sulfur dioxide gas absorption line at 1102 GHz in a heterodyne mode.
The performance of a NbN based phonon-cooled Hot Electron Bolometric (HEB) quasioptical mixer is investigated in the 0.65-3.12 THz frequency range. The device is made from a 3 nm thick NbN film on high resistivity Si and integrated with a planar spiral antenna on the same substrate. The in-plane dimensions of the bolometer strip are 0.2/spl times/2 /spl mu/m. The best results of the DSB noise temperature at 1.5 GHz IF frequency obtained with one device are: 1300 K at 650 GHz, 4700 K at 2.5 THz and 10000 K at 3.12 THz. The measurements were performed at 4.5 K ambient temperature. The amount of local oscillator (LO) power absorbed in the bolometer is about 100 nW. The mixer is linear to within 1 dB compression up to the signal level 10 dB below that of the LO. The intrinsic single sideband conversion gain measured at 650 GHz is -9 dB, the total conversion gain is -14 dB.