Slot Dipole Research Articles

Arrays of antenna-coupled bolometers using transition edge sensors

We are developing antenna-coupled transition edge sensor (TES) bolometer arrays for use in the measurement of the cosmic microwave background polarization. We have designed and built a prototype antenna-coupled bolometer pixel. This design uses a double slot dipole antenna on a silicon hemispherical lens, fed with superconducting niobium microstrip. Microstrip filters are used to define the frequency band of the optical response, which is centered at 217GHz with 40% bandwidth. The microstrip is terminated into a load resistor on a silicon nitride suspension, adjacent to a TES which is used to measure the dissipated power.We will discuss our progress in the development of the prototype pixel chips as well as the baseline design of a bolometer array for POLARBEAR, a CMB polarization experiment.

Dual‐frequency and broadband characteristics of hybrid coupled slot antennas fed by coplanar waveguide

AbstractA simple design of a hybrid coupled slot antenna, fed by coplanar waveguide with dual‐frequency or broadband operation, is presented. The proposed antenna is constructed by a coplanar waveguide (CPW) capacitively coupled slot‐loop antenna and a CPW inductively coupled dipole slot antenna. The dimensions of the two slot antennas decide the two resonant frequencies of the proposed antenna, respectively. Results show that the impedance bandwidth of the proposed broadband slot antenna is about 35%. Details of the proposed dual‐frequency and broadband designs are described and experimental results are presented and discussed. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 496–498, 2003; Published online in Wiley InterScience (www.interscience.wiley.com).

Frequency tunable CPW-fed slot dipole using piezoelectric transducer

A frequency tunable CPW-fed slot dipole using a piezoelectric transducer (PET) is presented. A dielectric perturber attached on a PET is used to change the effective dielectric constant of the slot line at the slot dipole. The electrical length of the slot dipole is changed due to the variation of the air gap between the slot dipole and the perturber by an external voltage. The resonant frequency of the slot dipole is tuned over 300 MHz from 4.65 to 4.35 GHz using an external voltage of 60 V.

Design of an efficient miniaturized UHF planar antenna

The design aspects and the measured results of a novel miniaturized planar antenna are described. Such architectural antenna design is of great importance in mobile military communications where low visibility and high mobility are required. Slot radiating elements, having a planar geometry and capable of transmitting vertical polarization when placed nearly horizontal, are appropriate for the applications at hand. Slot antennas also have another useful property, so far as impedance matching is concerned. Basically, slot dipoles can easily be excited by a microstrip line and can be matched to arbitrary line impedances simply by moving the feed point along the slot. Antenna miniaturization can be achieved by using a high permittivity or permeability substrate and superstrate materials and/or using an appropriate antenna topology. We demonstrate miniaturization by designing an appropriate geometry for a resonant narrow slot antenna. A very efficient radiating element that occupies an area as small as 0.12/spl lambda//sub 0//spl times/0.12/spl lambda//sub 0/ is designed and tested. Simulation results, as well as the measured input impedance and radiation patterns of this antenna, are presented. This structure shows a measured gain of 0.5 dBi on FR4 substrate, which has a loss-tangent of the order of 0.01. Also, the effect of finite ground plane size on gain and resonant frequency is investigated experimentally.

Radiation efficiency and impedance bandwidth of conductor-backed CPW-fed broadside twin slot antennas on two-layer dielectric substrate

The radiation efficiency and impedance bandwidth of matched broadside twin slot dipoles, fed by a coplanar waveguide on a conductor-backed two-layer substrate, are investigated as a function of distance between the slots and height of the bottom substrate layer. It is confirmed that the low radiation efficiency associated with a single slot due to the excitation of parallel-plate modes may be greatly increased by using two slots spaced half a wavelength of the dominant two-layer parallel-plate mode apart. It is also demonstrated that the radiation efficiency of optimally spaced twin slots may be further improved by increasing the height of the bottom substrate layer, in general at the cost of decreased bandwidth. The effect of bottom substrate height on gain and directivity is investigated, and radiation patterns are provided for the case of optimally spaced twin slots. Twin slots on a conductor-backed two-layer substrate can yield high radiation efficiencies similar to those of previously reported twin slot antennas with a back plane, with the advantage of reduced overall height.

Efficiency and gain of slot antennas and arrays on thick dielectric substrates for millimeter-wave applications: a unified approach

A unified approach for representing the surface-wave fields and for computing the corresponding radiation efficiencies from arbitrarily shaped slot-type antennas on thick dielectric substrates at millimeter-wave (mm-wave) frequencies is presented. In this approach, two different representations of the surface-wave fields, i.e., the one based on the idea that the surface-wave power can be associated with a substrate radiation pattern and the other based on the cylindrical wave expansion, are linked together in a unified way. The developed theory is then applied for investigating the surface wave characteristics of printed twin offset slots and uniform linear slot arrays. Based on the developed theory, new insight into the mechanism with which surface-wave power is coupled by the slot pair is presented. Subsequently, the optimum number of elements and corresponding interelement spacing for linear, uniformly excited, slot dipole arrays is explored for achieving maximum radiation efficiency and gain. In order to provide guidance on practical mm-wave integrated slot antenna array design, supportive numerical results are presented for Substrates of dielectric constant /spl epsi//sub r/ = 4.0 and /spl epsi//sub r/ = 12.0.

Radiation efficiency and impedance bandwidth of conductor‐backed CPW‐FED slot dipole antenna with two‐layered dielectric substrate

AbstractRadiation efficiency and impedance bandwidth of optimally matched conductor‐backed coplanar waveguide‐fed slot dipoles on two‐layer substrates are investigated as a function of bottom substrate layer height. It is demonstrated that low radiation efficiency due to parasitic parallel‐plate modes may be notably improved through increased height of the bottom layer at the cost of decreasing bandwidth. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 34: 138–141, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10396

Analytical field calculation of helical coils

Various helical coils such as helical dipole magnets, multifilamentary superconductors and superconducting strands have something in common with the helical structure. In this paper, we discuss the analytical calculation for the magnetic field of helical coils. In addition, the comparison between the analytical and numerical calculations is presented for simple helical coils. In particular, the helical multipole coefficients are introduced for helical dipole magnets, which are essential components of Siberian Snakes and spin rotators for polarized proton acceleration at Relativistic Heavy-Ion Collider (RHIC). The relation between the field homogeneity and helical multipoles is also studied. Finally, the analytically and numerically calculated and measured results of the magnetic field at the middle of the slotted helical dipole prototypes with the half-length for RHIC are compared. In this paper, the end effects of helical dipoles is not treated.

Antenna arrays in MCM-D technology fed by coplanar CPW networks

In this paper, the design, fabrication, and characterization of planar antenna arrays in the MCM-D technology are presented. The arrays are fed by coplanar feeding networks built using coplanar-waveguide lines. 2/spl times/2 and 4/spl times/4 arrays of slot dipoles designed to work in K-band, around 25 GHz, are also presented. The analysis was carried out both theoretically and experimentally. The results include the return loss, radiation patterns, and antenna gain. The proposed arrays are compatible with the driving electronics technology, enjoying high-impedance bandwidth, low cross polarization, high gain, and high radiation efficiency.

Analysis of a slot microstrip antenna

The slot microstrip antenna is used as a folded slot dipole symmetrically fed across a gap by means of a strip line. A theoretical model equivalent to several lossy transmission lines had been described previously to explain the bandwidth and the radiation admittance. The theory is improved when coupling between the two equivalent radiating lines of every slot is taken into account, and explains a fourth resonance near the third one, which had been measured on several models. Theoretical results and experiments are in good agreement. They are radiation admittance in a wide frequency band, current distribution along each slot and radiation patterns.

On some design examples of a circularly polarized wave array antenna using slot antenna combined with parasitically excited dipoles

AbstractThere are two methods to obtain a circularly polarized array antenna. One is to arrange and feed linearly polarized elements (such as slots) in an appropriate manner. Another is to arrange circularly polarized elements. The second approach is used to design a four‐element circularly‐polarized planar array consisting of a slot and parasitic dipoles. An array antenna having good characteristics is obtained and described. In general, coupling exists between the array elements, and these couplings affect the antenna characteristics, particularly in the case of circularly‐polarized arrays. Before beginning the design, the changes in the circular polarization characteristics of a single element are numerically evaluated as a function of the coupling, and this information is used as a reference in the design of the circularly polarized arrays. Then, with a formulation including the inter‐element coupling, calculations are made for a situation more nearly approximating actual practice. The possibility of obtaining a small antenna with a bandwidth of 1.5 dB axial ratio (6%) and a gain of more than 13 dB is pointed out.

Excitation of a conducting cylindrical surface of large radius of curvature

Approximate expressions are obtained for the magnetic field induced by slots on conducting circular cylinders of infinite length and of radius large compared to the signal wavelength. The approximations are derived from the formal solution of the cylinder problem and are valid for all distances from the slot. The expression for a short slot dipole, at any orientation, is expressed in terms of the field of the slot on a flat conducting sheet multiplied by a curvature term. The latter is a function of the ray path length and radius of curvature, making the results applicable to other convex surfaces. Corresponding expressions for half wavelength axial and transverse slots are also obtained and the results compared with experimental measurements.

Design of a Coaxial Hybrid Junction

The design of a coaxial hybrid junction is discussed. The hybrid consists of a shunt junction and a series junction. The shunt junction is a broad-band stub compensated tee, and the series junction is basically a balun of the type used to excite a slotted dipole. There is inherent isolation between the shunt and series terminals. The useful bandwidth of the hybrid is at least 10 per cent, while the bandwidth of the shunt junction alone exceeds this by a factor of four. Design data are presented for frequency bands centered at 425 Mc and 220 Mc. Many of these hybrids have been manufactured for application, and the performance repeats very well. Performance data are given for VSWR, isolation, and peak power capacity.