55 research outputs found
Near millimeter wave imaging/multi-beam integrated antennas
This report describes the most recent work on the theory of single element Linearly Tapered Slot Antennas (LTSAs) and Constant Width Slot Antennas (CWSAs). The radiation mechanism for these is presently well understood and allows quantitative calculation of beamwidths and sidelobe levels, provided that the antennas have a sufficiently wide conducting region on either side of the tapered slot. Appendices 4 to 7 represent earlier work on the grant. This work further elucidates the properties of arrays of CWSA elements, and the effects of coupling on the beam-shape. It should be noted that typical beam-efficiencies of 65% have been estimated, and that element spacings of about one Rayleigh unit are possible. Further, two-point resolution at the Rayleigh spacing has been demonstrated for a CWSA array in a 30.4 cm paraboloid at 31 GHz. These results underscore that interest in further studies of the radiation mechanism of tapered slot arrays. Appendix 7 constitutes a final, detailed report on the work leading to a 94 GHz seven element LTSA array imaging system, which has been reported previously in less detail. Experimental results are presented
Near millimeter wave imaging/multi-beam integrated antennas
Theoretical models of single element Linearly Tapered Slot Antennas (LTSA) and coupling effects of LTSA arrays are discussed. A list of publications is given
Direct and Heterodyne Detection of Microwaves in a Metallic Single Wall Carbon Nanotube
This letter reports measurements of microwave (up to 4.5 GHz) detection in
metallic single-walled carbon nanotubes. The measured voltage responsivity was
found to be 114 V/W at 77K. We also demonstrated heterodyne detection at 1 GHz.
The detection mechanism can be explained based on standard microwave detector
theory and the nonlinearity of the DC IV-curve. We discuss the possible causes
of this nonlinearity. While the frequency response is limited by circuit
parasitics in this measurement, we discuss evidence that indicates that the
effect is much faster and that applications of carbon nanotubes as terahertz
detectors are feasible
Terahertz detection in single wall carbon nanotubes
It is reported that terahertz radiation from 0.69 THz to 2.54 THz has been
sensitively detected in a device consisting of bundles of metallic carbon
nanotubes, quasi-optically coupled through a lithographically fabricated
antenna, and a silicon lens. The measured data are consistent with a bolometric
process and show promise for operation above 4.2 K.Comment: 9 page
Antenna-coupled terahertz radiation from joule-heated single-wall carbon nanotubes
In this letter an experimental method is introduced that allows detection of terahertz (THz) radiation from arrays of joule-heated Single-Walled Carbon Nanotubes (SWCNTs), by coupling this radiation through integrated antennas and a silicon lens. The radiation forms a diffraction-limited beam with a total maximum radiated power of 450 nW, significantly greater than the power estimated from Nyquist thermal noise (8 nW). The physical radiation process is unknown at this stage, but possible explanations for the high radiated power are discussed briefly. The emission has a typical bandwidth of 1.2 THz and can be tuned to different frequencies by changing the dimensions of the antennas. Arrays of the devices could be integrated in CMOS integrated circuits, and find application in THz systems, such as in near-range medical imaging
On the feasibility of constructing an imaging array of slot-antennas integrated with SIS mixers
Several important developments have been made for the realization of array mixer receivers for imaging in radio astronomy: preliminary experiments on a 700 GHz SIS mixer have been performed and imaging at 31 GHz using an array of tapered slot antennas equipped with diode detectors has been demonstrated. These developments are briefly describe
NbN Hot Electron Bolometric Mixer with Intrinsic Receiver Noise Temperature of Less than Five Times the Quantum Noise Limit
ABSTRACT-In recent years, improvements in device development and quasi-optical coupling techniques utilizing planar antennas have led to a significant achievement in low noise receivers for the edges of the submillimeter frequency regime. Hot Electron Bolometric (HEB) receivers made of thin superconducting films such as NbN have produced a viable option for instruments designed to measure the molecular spectra for astronomical applications as well as in remote sensing of the atmosphere in the THz regime. This paper describes an NbN HEB mixer with intrinsic DSB receiver noise temperature of at most five times the quantum noise limit at frequencies as high as 2.24 THz. I. INTRODUCTION New measurements with an NbN Hot Electron Bolometric (HEB) Mixer, which was described in detail at last year's IMS [1] and in a subsequent IEEE Trans. MTT paper II. DEVICE DESIGN AND FABRICATION The HEB receivers were fabricated by conventional UV lithographical techniques on thin film (3 t
- …