16 research outputs found
Surface wave control for large arrays of microwave kinetic inductance detectors
Large ultra-sensitive detector arrays are needed for present and future
observatories for far infra-red, submillimeter wave (THz), and millimeter wave
astronomy. With increasing array size, it is increasingly important to control
stray radiation inside the detector chips themselves, the surface wave. We
demonstrate this effect with focal plane arrays of 880 lens-antenna coupled
Microwave Kinetic Inductance Detectors (MKIDs). Presented here are near field
measurements of the MKID optical response versus the position on the array of a
reimaged optical source. We demonstrate that the optical response of a detector
in these arrays saturates off-pixel at the dB level compared to the
peak pixel response. The result is that the power detected from a point source
at the pixel position is almost identical to the stray response integrated over
the chip area. With such a contribution, it would be impossible to measure
extended sources, while the point source sensitivity is degraded due to an
increase of the stray loading. However, we show that by incorporating an
on-chip stray light absorber, the surface wave contribution is reduced by a
factor 10. With the on-chip stray light absorber the point source response
is close to simulations down to the dB level, the simulation based on
an ideal Gaussian illumination of the optics. In addition, as a crosscheck we
show that the extended source response of a single pixel in the array with the
absorbing grid is in agreement with the integral of the point source
measurements.Comment: accepted for publication in IEEE Transactions on Terahertz Science
and Technolog
Eliminating stray radiation inside large area imaging arrays
With increasing array size, it is increasingly important to control stray
radiation inside the detector chips themselves. We demonstrate this effect with
focal plane arrays of absorber coupled Lumped Element microwave Kinetic
Inductance Detectors (LEKIDs) and lens-antenna coupled distributed quarter
wavelength Microwave Kinetic Inductance Detectors (MKIDs). In these arrays the
response from a point source at the pixel position is at a similar level to the
stray response integrated over the entire chip area. For the antenna coupled
arrays, we show that this effect can be suppressed by incorporating an on-chip
stray light absorber. A similar method should be possible with the LEKID array,
especially when they are lens coupled.Comment: arXiv admin note: substantial text overlap with arXiv:1707.0214
An Ultra-Wideband Leaky Lens Antenna for Broadband Spectroscopic Imaging Applications
We present the design, fabrication and characterisation of a broadband leaky
lens antenna for broadband, spectroscopic imaging applications. The antenna is
designed for operation in the 300-900 GHz band. We integrate the antenna
directly into an Al-NbTiN hybrid MKID to measure the beam pattern and absolute
coupling efficiency at three frequency bands centred around 350, 650 and 850
GHz, covering the full antenna band. We find an aperture efficiency over the whole frequency band, limited by lens reflections. We
find a good match with simulations for both the patterns and efficiency,
demonstrating a 1:3 bandwidth in the sub-mm wavelength range for future on-chip
spectrometers.Comment: Accepted for Publication at IEEE Transactions on Antennas and
Propagatio
First light demonstration of the integrated superconducting spectrometer
Ultra-wideband 3D imaging spectrometry in the millimeter-submillimeter
(mm-submm) band is an essential tool for uncovering the dust-enshrouded portion
of the cosmic history of star formation and galaxy evolution. However, it is
challenging to scale up conventional coherent heterodyne receivers or
free-space diffraction techniques to sufficient bandwidths (1 octave) and
numbers of spatial pixels (>). Here we present the design and first
astronomical spectra of an intrinsically scalable, integrated superconducting
spectrometer, which covers 332-377 GHz with a spectral resolution of . It combines the multiplexing advantage of microwave kinetic
inductance detectors (MKIDs) with planar superconducting filters for dispersing
the signal in a single, small superconducting integrated circuit. We
demonstrate the two key applications for an instrument of this type: as an
efficient redshift machine, and as a fast multi-line spectral mapper of
extended areas. The line detection sensitivity is in excellent agreement with
the instrument design and laboratory performance, reaching the atmospheric
foreground photon noise limit on sky. The design can be scaled to bandwidths in
excess of an octave, spectral resolution up to a few thousand and frequencies
up to 1.1 THz. The miniature chip footprint of a few
allows for compact multi-pixel spectral imagers, which would enable
spectroscopic direct imaging and large volume spectroscopic surveys that are
several orders of magnitude faster than what is currently possible.Comment: Published in Nature Astronomy. SharedIt Link to the full published
paper: https://rdcu.be/bM2F
Compact parabolic reflector antenna design with cosecant-squared radiation pattern
This paper deals with the parametric analysis and proper design of parabolic reflector antennas to obtain pencil-beam, cosecant-squared and inverse cosecant-squared radiation patterns for air and coastal surveillance radars. A novel design is introduced to obtain both pencil-beam and cosecant-squared radiation patterns by using the same modified parabolic reflector antenna structure fed by an H-plane horn feeder which can be adjusted as symmetric or asymmetric feeder by changing the bottom flare angle. The analytical regularization method (ARM) is used as a fast and accurate way to solve the problem of E-polarized wave diffraction by parabolic shaped perfectly electrical conductive (PEC) cylindrical reflector with finite thickness. The numerical procedure is initially verified by the analytical and numerical methods, and the calculated radiation characteristics are presented for the proposed antenna configurations
Analysis of back wall smoothing and multisource feeding effects for H-plane horn radiator
Triangular-Shaped Single-Loop Resonator: A Triple-Band Metamaterial With MNG and ENG Regions in S/C Bands
A new metamaterial topology, called triangular-shaped single-loop resonator (SLR), is introduced with two distinct mu-negative (MNG) regions and one epsilon-negative (ENG) region over the S/C frequency bands. Transmission and reflection characteristics of the suggested subwavelength resonator are analyzed using full-wave electromagnetic solvers, Ansoft HFSS and CST Microwave Studio (MWS), to demonstrate the presence of four closely located resonance frequencies within the 3.3-5.1 GHz range. Effective permittivity and permeability parameters of the resulting composite medium are retrieved from simulated complex scattering parameters to verify the existence of fully developed MENG and ENG regions. Dependence of the resonance frequencies on the design parameters of the triangular SLR unit cell and on the presence of its gaps are also investigated in detail
An outline of indirect holographic methods for antenna measurements and microwave imaging
Indirect microwave holographic techniques offer a simple, low cost technique for a range of microwave measurements including the determination of antenna characteristics and the ability to provide good quality images of passive objects. This work provides a brief outline of the basic theory of indirect microwave holography and how it can be used for the reconstruction of scattered complex fields at the measurement plane and how these results can be back propagated to provide the scattered fields at any preselected observation plane. It provides an outline of the different techniques required for antenna measurement and the imaging of passive objects. It demonstrates how indirect holography can be used to determine the far field radiation pattern of a high gain antenna and reconstruct the complex antenna aperture fields. This work also demonstrates the use of indirect holography for the imaging of passive objects. The techniques described have been validated by experimental results on a range of objects including buried objects
A compact five-band SLR type metamaterial
In this paper, a novel single-loop resonator (SLR) type metamaterial topology is proposed with five distinct resonance frequencies placed within the frequency band from 2.8 GHz to 5.1 GHz displaying two -negative (ENG) and three -negative (MNG) bands. This new SLR unit cell is obtained by slightly modifying the geometrical structure of the square-shaped SLR that is recently reported in literature with only three resonances. Transmission and reflection characteristics of both standard square-shaped SLR and its newly modified version are simulated by two different full wave electromagnetic solvers, Ansoft's HFSS and CST Microwave Studio, to verify the accuracy of numerical results. Effective permittivity and permeability parameters of these metamaterial structures are retrieved from simulated complex scattering parameters to verify the presence of distinct ENG and MNG regions. E-field distributions are computed over the conductive strips to investigate the mechanism of resonances. Finally, effects of substrate permittivity and substrate thickness on the values of resonance frequencies are inspected parametrically for the novel SLR topology. © 2012 IEEE