Metal Plate Lens Research Articles

Low-Profile Scanloss-Reduced Integrated Metal-Lens Antenna

Integrated lens antennas are widely used in high gain and beam steering applications at millimeter-wave frequencies. The ILA has often large height and suffers from significant scan loss. In this article, we demonstrate a low-profile, efficient, and scanloss-reduced integrated metal-lens antenna (IMLA). An IMLA is a combination of a dielectric lens and metal–plate lens. A 16- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> diameter IMLA is designed using the HDPE and 58 stainless steel plates to achieve the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f/d$ </tex-math></inline-formula> of 0.69. The simulated aperture and radiation efficiency of the IMLA are 73% and 92%, respectively. At 76 GHz, the simulated and measured realized gains of the fabricated IMLA are 31.24 and 31 dBi, respectively. The IMLA is designed to steer the main beam to ±30°. The scan loss is reduced by tilting the radiation pattern of the feeds at offset positions along the focal plane. The radiation pattern of the square waveguide feed is tilted using asymmetrical dielectric pins. The asymmetrical dielectric pins reduce the simulated gain scan loss of the IMLA by more than 1.5 dB at 30° steering angle. The simulation results show that the inclination of the feed radiation pattern helps limit the scan loss of the IMLA to 4.1 and 4.3 dB in the H- and E-planes for 30° steering angle, respectively. The measured scan loss of the manufactured IMLA is 3.8 and 6.2 dB in the H- and E-plane, respectively.

RESULTS AND TOOLS FOR EVALUATING THE EFFECTIVENESS OF FOCUSING SYSTEMS TO IMPROVE ACCESSIBILITY IN WIRELESS NETWORKS

The widespread use of wireless technologies leads to an ever-increasing number of users and permanently functioning devices. However, the growth of the number of wireless users in a limited space and a limited frequency range leads to an increase in their mutual influence, which ultimately affects the throughput of wireless channels and even the performance of the system as a whole. The article presents the statistics and tendencies of the distribution of wireless networks of the IEEE 802.11 standard systems, as well as analyzes the main problems that arise during the expansion of their use. Substantiation and choice of ways to overcome these difficulties largely depends on the objective control of radiation parameters of access points and subscriber funds in a particular environment. The review of the state control facilities provided by the developers of the equipment is presented, and author's variants of experimental measuring complexes are offered, allowing to control signal and information parameters of Wi-Fi systems. The experimental results obtained with the use of the indicated means, obtained using the accelerating metal-plate lens as an additional autonomous element for focusing the field, including for MIMO systems, the effect of the accelerating metal-plate lens on the spatial distribution of the field, on the spectral structure of the signal are presented. In addition, polarization effects were investigated. Possible ways to further increase the availability, integrity of information and energy efficiency of wireless access systems are discussed. The authors propose simpler and less costly options for increasing the direction of radiation on the basis of an accelerating metal-plate lens, experimentally tested, as well as the use of zone zoning on the path of the computer.

A Study on Measurement of Material Constant to High Dielectric Constant Material by using Condensing Metal Plate Lens Antenna in C-Band

A Study on Measurement of Material Constant to High Dielectric Constant Material by using Condensing Metal Plate Lens Antenna in C-Band

Apparatus for generating quasi-free-space microwave-driven plasmas.

An apparatus for generating quasi-free-space microwave-driven plasmas has been designed, constructed, and tested. The plasma is driven by a multi-kW, ∼5 GHz microwave beam focused at the center of a vacuum chamber using a Koch-type metal plate lens. Sustained plasma discharges have been generated in argon at pressures ranging from 150 to 200 mTorr, at beam power levels ranging from 5 to 10 kW, and at gas flow rates of approximately 200 SCCM.

A High-Power Microwave Zoom Antenna With Metal-Plate Lenses

Metal-plate lens antennas were designed and constructed for a high-power microwave zoom antenna concept comprising a pyramidal horn feed antenna and two metal-plate lenses. Good agreement was found between experiment and simulation. This antenna provides true zoom capability with continuously variable collimated beam output, approximately 10% bandwidth, and very high power-handling capability. It can be designed to operate at any frequency in the range of about 100 MHz to 10 GHz. It was found that nano-modified carbon fiber composites could be used instead of metal plates in these lenses; these composites would reduce the weight of the lens significantly and would help to mitigate possible spurious TM modes induced in the lens when it is in the near-field of the feed horn antenna.

APPLICATION OF INTEGRAL EQUATION METHOD TO METAL-PLATE LENS STRUCTURES

The present paper concerns the design, numerical analysis, and measurement for simple metal-plate lens structures. The power of electromagnetic waves can be concentrated by arranging flat strips parallel to one another and adjusting the transverse and longitudinal length of the waveguide regions. The simple designing procedures are described for the lenses with plane, concave, and convex profiles. These steps are practically applied to construct the lenses for the X band. In order to discuss the dependence of focusing properties on the lens and source types, we numerically analyze the scattering problems using the integral equations combined with the moment method. The lenses are made up by aluminum plates, and the field amplitude in the transmission region is measured. We confirm the formation of the focus near the design point.

Use of microwave lenses in phase retrieval microwave holography of reflector antennas

The Misell (1973) phase retrieval algorithm for microwave holography requires the capability to axially move an antenna's subreflector or feed to obtain a defocused far-field magnitude pattern. A microwave lens may be used as an alternative method of defocusing an antenna. A metal plate lens has been designed and constructed for use in phase retrieval holography at the Georgia Tech Woodbury Research Facility. Its phase variation across the aperture was chosen to have a parabolic profile in order to imitate the effect of subreflector or feed translation. A two-dimensional (2-D) finite-difference time-domain simulation has been performed to characterize the lens. Measurements, using the measured aperture phase of the lens transfer function as a phase correction term in the Misell algorithm, show the results to be comparable with that of phase coherent holography. Other types of microwave lenses such as a Fresnel zone plate, a bed of circular waveguides, and a standard dielectric lens are also being studied.

Heating system with a lens applicator for 430 MHz microwave hyperthermia

To attain deep and localized heating for hyperthermic treatment of cancers, metal plate lens applicators that can converge microwave electromagnetic (EM) energy in the lossy medium such as human muscle with a computer-controlled heating system have been developed. This paper describes a system operating at 430 MHz. Results of an electric-field distribution calculation and a heating experiment made on a saline solution phantom show that the maximum heating depth is over 60 mm using the lens applicator, which is twice as deep as that obtained with a conventional waveguide applicator. The experimental results agree well with the theoretical ones. A computer-controlled heating system has been developed using the applicator. Experimental results show that fluctuations in temperature at locations in the heating region of the saline phantom were maintained within +/- 0.3 degrees C of the present temperatures. These results indicate that the system can be used for the clinical hyperthermia treatment of cancer.

High-sensitivity microwave optics

Microwave optics experiments operating at a 3.33-cm wavelength (9 GHz) are described that have an overall signal gain of 58 dB, which is achieved by using a 1000-Hz square-wave modulated reflex klystron and a high-gain, narrowband amplifier following a point-contact detector. A metal-plate electromagnetic lens is employed that has a gain of 22.5 dB relative to an isotropic radiator, produces a beam collimated to within 12 deg between half-power points, and has a 3.7% bandwidth around a center frequency of 9 GHz. This basic system was used to developed microwave versions of the Michelson interferometer, Bragg reflection, Brewter’s law and total internal reflection, and Young’s interference experiment. Measured radiation intensities for four signal sources are shown to lie well within Federal performance regulations established in 1971.

Correction to "Pattern Shaping with a Metal Plate Lens"

Correction to "Pattern Shaping with a Metal Plate Lens"

Pattern shaping with a metal plate lens

The metallic parallel plate lens is a viable alternative to both the shaped reflector and the array antenna for beam shaping. A C -band antenna using this lens is designed to provide a csc^{2} \theta (cos \theta)^{1/2} power pattern over the angular limits of 60\deg-80\deg below horizontal. The Woodward-Levison synthesis technique is applied to determine the required amplitude and phase distribution across the aperture. Initial plate positions and lengths of the lens are determined from geometrical optics and infinite waveguide theory. The positions and lengths of the lens plates are adjusted experimentally until a satisfactory pattern is obtained.

Design Considerations and Study of Bandwidth-Characteristics of a Microwave Antenna Assembly

The complete design considerations of a microwave antenna assembly at various frequencies are presented. The compensation of the phase-front due to a feed position displaced from the focus towards the paraboloidal reflector is achieved by a suitable metal-plate lens with a refractive index of 0.75 at 10 GHz. A theoretical expression for the phase-front of the displaced feed is derived. Detailed lens structure for perfect compensation of the phase-front is supplemented. Bandwidth study has also been made at other frequencies in the X-band for the designed antenna assembly.

The design of cylindrical metal-plate microwave lenses fed by non-resonant slotted waveguide arrays

The use of a suitably modified refractive index enables cylindrical lenses with squinting linear feeds to be designed by the usual 2-dimensional methods applicable to lenses with non-squinting feeds.An example is given of the design of a typical lens fed by a nonresonant slotted waveguide having a 20° squint angle.

Methods of reducing chromatic aberration in metal-plate microwave lenses

Microwave lenses of the waveguide type are subject to a pronounced degree of chromatic aberration because of the inherent dispersion of the waveguides. However, this aberration can be substantially eliminated over an appreciable bandwidth by making the lens of slot-loaded ridged waveguides with special properties. This type of lens design makes it possible to achieve additional benefits as well, such as improved scanning capability and elimination of discontinuities in the surfaces at the junction of adjacent "zones" or "steps." The ridged waveguides are periodically loaded by means of transverse slots in the ridges. The ridges may be relatively wide and hollow, or quite thin and solid. Additional desirable properties are obtainable by placing a relatively small strip of dielectric material above the ridge. Experimental data on the propagation characteristics of several of these structures and on the effect of varying such parameters as ridge height, slot width, slot depth, slot spacing, frequency, and size of dielectric strip are given. An analysis of the phase errors which result from changes in the operating frequency shows that the aberrations may conveniently be separated into one type in which the phase front from each zone of the lens is distorted, and a second independent type in which the desired phase relationship between the zones is destroyed. Methods of eliminating either or both of these types of aberration by suitable design of the ridged waveguides are described. In addition, it is shown how the ridged waveguides can conveniently be used to achieve "zoning" or "stepping" by changing the effective index of thereby eliminating discontinuities in the lens surfaces and avoiding the undesirable diffraction which would otherwise occur at the boundaries between adjacent zones. The superiority of this type of lens structure in wide-angle scanning applications is also discussed. Numerical examples which illustrate the advantages of the loaded ridged waveguide lens are included.

Wide-Angle Metal-Plate Optics

The design equations for constrained metal-plate lenses are derived. These lenses prove to have exceptional wide-angle scanning properties. The scanning aberrations are investigated by means of a power series expansion of the phase error. This analysis indicates that the square-law error is a function of lens depth and may be eliminated by the proper choice of lens thickness. It is also indicated that coma is associated with the inner lens contour, and that elliptical or double-correction-point lenses have minimum coma. The mechanism of refocussing is investigated and its first-order effect is given as a power series. The scanning performance of various lens, types is expressed by means of formulas giving the number of beamwidths scanned as a function of the f/D ratio. Experimental data are presented on a lens capable of sweeping a one-degree beam 100 beamwidths. Further data indicate the importance of smooth contours and compact structures in achieving low spurious radiation and large scanning angles.

Metallic Delay Lenses

A metallic lens antenna is described in which the focussing action is obtained by a reduction of the phase velocity of radio waves passing through the lens rather than by increasing it as in the original metal plate lens. The lens shape accordingly corresponds to that of a glass optical lens, being thick at the center and thin at the edges. The reduced velocity or “delay” is caused by the presence of conducting elements whose length in the direction of the electric vector of the impressed field is small compared to the wavelength; these act as small dipoles similar to the molecular dipoles set up in non-polar dielectrics by an impressed field. The lens possesses the relatively broad band characteristics of a solid dielectric lens, and since the conducting element can be made quite light, the weight advantage of the metal lens is retained. Various types of lenses are described and a theoretical discussion of the expected dielectric constants is given. An antenna design which is especially suitable for microwave repeater application is described in some detail.