Integrated Lens Antenna Research Articles

Integrated lens antenna with a conic extension at 220 GHz

Integrated lens antenna with a conic extension at 220 GHz

Design and measurements of a terahertz quasi‐optical mixer integrated lens antenna

ABSTRACTThe article propose a quasi‐optical mixer, which could operate from 325 GHz to 350 GHz. A hybrid method is offered that combined FEM and MLFMM algorithm to design and optimize the lens antenna integrated a planar log‐periodic antenna and a Schottky diode. We also give the method for characterizing the conversion loss and noise temperature of the quasi‐optical mixer. The antenna gains at 340 GHz is calculated to be 29 dB from the measured radiation patterns. The measured DSB conversion loss of the mixer could achieve from 10.5 dB to 12.5 dB and the noise temperature is estimated to be lower than 5300 K with an improved measurement method. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:113–116, 2017

Integrated lens antenna array with full azimuth plane beam scanning capability at 60 GHz

ABSTRACTAn antenna array operating at 60 GHz is proposed. The proposed array covers impedance bandwidth of 5 GHz (57.5–62.5 GHz) with maximum gain of 16.25 dBi at 61. 5 GHz. With the proposed array 15 distinct radiation patterns in azimuth plane can be achieved, each having 3‐dB beamwidth of 24° and 3‐dB cross over. The beam scanning capability can be achieved by activating each array element one by one. Each array element consists of a conventional microstrip patch antenna (MPA) integrated with extended hemispherical Teflon lens. The Teflon lens is utilized to enhance the gain of conventional MPA as well as to achieve the desired elementary radiation pattern of array to cover full azimuth plane. A very good agreement between the measured and simulated results is observed. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:116–120, 2017

Effects of antireflective coatings on scanning performance of millimetre‐wave lenses

This study examines the beam scanning performance of the antireflective coatings designed on millimetre-wave integrated lens antennas with dense material. Dielectric lens antennas fabricated with a dense dielectric material allow good power transfer efficiency through the lens and enable fabrication of low-cost and compact-size lens antennas. However, using dense dielectric material causes strong multiple internal reflection behaviour inside the lens antenna. These multiple reflections deteriorate not only the return loss but also the radiation characteristics. Wide angle scanning performance is limited due to off-axis aberrations. Effects of strong internal reflections can be reduced considerably using one or more dielectric matching layers coated at the top of the antenna. A 77 GHz extended hemispherical lens antenna made of alumina is coated with different types of solutions for antireflection layers, namely, conventional quarter-wave transformer, multiple layer transformer, linear and circular corrugations and their performance in beam scanning applications is observed. The lens is illuminated by an aperture coupled microstrip antenna designed to radiate into alumina at 77 GHz. A frequency-dependent characterisation of the beam pattern clearly showed the existence and impact of internal reflections on beam scanning performance for 77 GHz automotive radar antennas.

Improvement of the Scanning Performance of the Extended Hemispherical Integrated Lens Antenna Using a Double Lens Focusing System

We demonstrate that an integrated lens antenna (ILA) with a double lens (DL) focusing system can provide simultaneously a high broadside directivity and a low scan loss over a wide angular range. The proposed DL ILA system consists of a hemispherical substrate lens and a planoconvex objective lens. A prototype of a high-gain DL ILA with lenses made of a low permittivity dielectric material is fabricated and characterized in the frequency range of 75–79 GHz. The realized scan loss in terms of gain within a ±30° field of view is <1.1 dB in both planes. The performance of the DL ILA is compared with that of two hemispherical ILAs designed to provide the best broadside directivity and the lowest scan loss, respectively.

Analysis of an integrated lens antenna fed by SIW slot array using a hybrid MoM–PO method

This paper presents a very fast and highly efficient full-wave hybrid method for analyzing an integrated dielectric lens antenna (ILA) fed by multilayered substrate-integrated waveguide (SIW) slot antenna/array. The feeding antenna structure is modeled as a stacked parallel-plate waveguide with metallic posts, coupling, and radiating slots. Physical optics method in conjunction with three-dimensional ray tracing technique is employed to analyze the effect of the dielectric lens on the SIW feeding slots. Fields in the SIW structure are computed by considering the Dyadic Green's function expressed as an expansion of vectorial cylindrical eigenfunctions and taking into account scattering at the conducting posts. Slots are modeled with equivalent magnetic currents expressed as a sum of domain basis functions. By imposing continuity of the tangential components of the fields an integral equation is obtained that is solved with the application of method-of-moments. In order to validate the proposed technique, a hemispherical ILA fed by a double-layered SIW cavity which is backed with slot antenna is analyzed. Excellent agreement is obtained with HFSS software together with significant improvement in computational time and memory requirements.

An Efficient Method for Calculating the Characteristics of the Integrated Lens Antennas on the Basis of the Geometrical and Physical Optics Approximations

We develop a combined method for calculating the characteristics of the integrated lens antennas for millimeter-wave wireless local radio-communication systems on the basis of the geometrical and physical optics approximations. The method is based on the concepts of geometrical optics for calculating the electromagnetic-field distribution on the lens surface (with allowance for multiple internal re-reflections) and physical optics for determining the antenna-radiated fields in the Fraunhofer zone. Using the developed combined method, we study various integrated lens antennas on the basis of the data on the used-lens shape and material and the primary-feed radiation model, which is specified analytically or by computer simulation. Optimal values of the cylindrical-extension length, which ensure the maximum antenna directivity equal to 19.1 and 23.8 dBi for the greater and smaller lenses, respectively, are obtained for the hemispherical quartz-glass lenses having the cylindrical extensions with radii of 7.5 and 12.5 mm. In this case, the scanning-angle range of the considered antennas is greater than ±20° for an admissible 2-dB decrease in the directivity of the deflected beam. The calculation results obtained using the developed method are confirmed by the experimental studies performed for the prototypes of the integrated quartz-glass lens antennas within the framework of this research.

Millimeter-Wave Electronically Steerable Integrated Lens Antennas for WLAN/WPAN Applications

This paper presents design and experimental verification of electronically steerable integrated lens antennas (ILAs) for WLAN/WPAN communication systems operating in the 60-GHz frequency band. The antenna is comprised of a quartz extended hemispherical lens, four switched aperture coupled microstrip antenna (ACMA) elements, and a distribution circuit based on SPDT MMIC switches. The designed ILAs are capable of electronic steering between four different antenna main beam directions in one plane. Fixed beam and electronically steerable ILA prototypes are fabricated and tested. The results are given for two quartz dielectric lenses with the radii of 7.5 and 12.5 mm in order to meet a wide range of WLAN/WPAN requirements. The measured maximum gains of the designed ILAs are 18.4 and 23.2 dBi. The experimental results of the fabricated electronically steerable quartz ILA prototypes prove the simulation results and show ±35 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> and ±22 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> angle sector coverage for the lenses with the 7.5 and 12.5 mm radii, respectively. The bandwidth of the ILAs exceeds the frequency band of 57-66 GHz allocated for WLAN/WPAN applications. The designed ILAs meet all the requirements for steerable directional antennas of 60-GHz WLAN/WPAN systems.

Experimental Characterization of E-Band Two-Dimensional Electronically Beam-Steerable Integrated Lens Antennas

This letter presents design of E-band integrated lens antennas (ILAs) with two-dimensional (2-D) fully electronical beam-steering capability. Two extended hemispherical quartz lenses with the radii of 7.5 and 12.5 mm and a feeding printed circuit board (PCB) with 16 aperture-coupled microstrip antenna (ACMA) elements arranged in a 2-D order together with a switching circuit were fabricated for experimental verification. A set of the directivity and radiation patterns measurements of the scanning antenna at 77 and 85 GHz is presented. It is shown that the ILA with the radius of 12.5 mm provides the coverage within the solid angle in any direction from the lens axis with the directivity not lower than 20 dBi in the covered area. The ILA with the radius of 7.5 mm provides higher coverage (within ), but with the lower directivity of 16 dBi. A good agreement between the electromagnetic simulations and the measurements is demonstrated. The designed ILAs can be effectively used in different millimeter-wave applications such as WLAN/WPAN communications, automotive radars, imaging systems, and millimeter-wave radio backhaul systems.

REDUCTION OF INTERNAL REFLECTIONS IN INTEGRATED LENS ANTENNAS FOR BEAM-STEERING

The conventional integrated lens antennas (ILAs) for beam steering sufier from internal re∞ections that deteriorate the scanning properties. The internal re∞ections are known to afiect side lobes, cross-polarisation level, input impedance of the feed, and mutual coupling. In this paper, ILAs are designed to exhibit very low re∞ection loss, i.e., to minimize the internal re∞ections. Wide ranges of realistic relative permittivities of the lens and of the feed element directivities are considered. It is shown that with any permittivity and with any feed directivity it is possible to design the lens shape in such a way that the re∞ection loss is low, for moderate beam-steering angles, without resorting to a complicated matching layer. The gain, directivity, beam-width, and the resulting distance between the feed elements are compared for all the designed lenses.

Studying integrated silicon-lens antennas for radio communication systems operated in the 60 GHz frequency band

We consider the development of an integrated lens antenna for LAN radio communication systems operated in the 60 GHz frequency band. The antenna is an extended hemispherical silicon lens. On its flat surface, a microstrip antenna element is located. The use of silicon, which has a dielectric permittivity e = 11.7, as the lens material ensures the maximum range of scanning angles for the minimum axial size of the lens. The approximate analytical formulas, which are used for initial calculations of the lens parameters, allow one to evaluate the basic parameters of the lens antenna integrated with the microstrip antenna element. For further optimizing the parameters of the lens and the antenna element, 3D simulation of the electromagnetic-field distribution was performed. Based on its results, we have developed and manufactured extended hemispherical silicon lenses, which had radii of 6 and 12 mm. The planar microstrip antenna element was manufactured by the low temperature co-fired ceramics (LTCC) technology. The results of simulation and experimental studies of the manufactured prototypes demonstrate that the developed lens antennas has directivities of 17.6 and 23.1 dBi for lenses with radii of 6 and 12 mm, respectively. In this case, the maximum beam deflection angle is achieved, which is equal to 55°, while the permissible decrease in the directivity is no more than 6 dBi compared with the case of a non-deflected beam. The obtained results show that the developed integrated lens antennas can find applications in high-speed radio communication systems operated in the millimeter-wave range.

Size and Weight Reduction of Integrated Lens Antennas Using a Cylindrical Air Cavity

A simple and low-cost solution to reduce the height and weight of extended hemispherical lenses is proposed based on the introduction of a cylindrical air cavity above the primary feed. The presence of an additional air-dielectric interface enables one to shorten the focal length of the lens, which leads to antenna height and weight reductions of 13% and 27%, respectively. The communication describes the design principle and performance characteristics of the reduced-size integrated lens antenna, superimposed with a conventional synthesized elliptical one. Both prototypes are fabricated in Rexolite and measured in Ka band. A good agreement between the performance characteristics of the antennas is observed. The additional advantages of the proposed approach are explained, and its applicability for lens antennas made of high-k materials is discussed.

Numerical Study of Self-Complementary Antenna Characteristics on Substrate Lenses at Terahertz Frequency

This paper presents a numerical study of self-complementary antennas on substrate lenses made of high-permittivity dielectric material. Bowtie, logarithmically periodic, and logarithmic spiral antennas with the same outer and inner dimensions were selected for study, and their overall performances were compared in the terahertz band at frequencies up to 5.0 THz. The resonance and radiation characteristics of the three antennas were investigated in terms of input impedance, directivity, and radiation efficiency, using a full electromagnetic simulator. This study provides useful guidelines and partially solves the difficult problems of choosing the proper feed and optimizing the lens structure for a THz broadband integrated lens antenna.

Analysis and design of ring-resonator integrated hemi-elliptical lens antenna at terahertz frequency

In this paper, a novel lens integrated ring-resonator microstrip antenna is analyzed and simulated at 600GHz. A mathematical model to compute the directivity of this kind of the antenna has been developed and the directivity of the antenna has been computed which is 18dBi. The proposed model has been simulated by using CST Microwave Studio a commercially available simulator based on finite integral technique and similar result has been obtained. Further, the directivity of the antenna has also been computed by using the techniques reported in the literature and in this case also we have obtained the similar result. Later, a probe-fed patch integrated lens antenna has also been investigated to validate the correctness of the numerical method. To find the potential advantages of this kind of the structure, the −10dB impedance bandwidth of the antenna has been compared to a lens-integrated probe-fed microstrip patch antenna and a significant enhancement in the bandwidth has been observed.

USING OPTIMIZED ECCENTRICITY REXOLITE LENS FOR ELECTRICAL BEAM STEERING WITH INTEGRATED APERTURE COUPLED PATCH ARRAY

Design and measurement results of a beam-steering integrated lens antenna at 77GHz are presented. An 8-element LTCC aperture coupled patch antenna feed array with a switching network is used to electrically steer the main beam in H-plane. A 100-mm diameter Rexolite (r = 2:53) lens is simulated and tested. The eccentricity of the lens is optimized in an earlier work with ray-tracing simulations for improved beam-steering properties compared to the conventional extended hemispherical and elliptical lenses. The beam- steering properties including scan loss, main-beam width and direction, side-lobe levels, directivity, and cross-polarization are analyzed in detail with both simulations and radiation pattern measurements. As expected, the results show that the side-lobe and cross-polarization levels are not predicted accurately with large feed ofisets using the ray-tracing simulations. Nevertheless, it is shown that the lens shape can be successfully optimized with the simple and fast ray-tracing simulations. The measured half-power beam-width at 77GHz is 2:5 - § 0:2 - up to the largest tested beam-steering angle of 30 - . The optimized eccentricity low permittivity lens results in smaller scan loss than the conventional lenses.

Reduced-Size Double-Shell Lens Antenna With Flat-Top Radiation Pattern for Indoor Communications at Millimeter Waves

We investigate the capabilities of reduced-size integrated lens antennas to produce flat-top radiation patterns for broadband wireless communication systems at millimeter waves. The main challenge consists in controlling accurately the lens radiation performance over a broad frequency band while reducing its size; this constitutes a difficult task since producing highly shaped beams usually leads to oversized lens antennas. The design procedure is based on the geometrical optics/physical optics method (GO/PO), and the antenna characteristics are confirmed by full-wave simulations since the antenna size is only a few wavelengths. Our numerical results demonstrate that one anti-reflection coating is necessary even if the lens is made in a low-permittivity material (Rexolite). The resulting double-shell dielectric lens antenna has been fabricated and measured. The experimental results are in very good agreement with the simulations, and the radiation characteristics are stable over a 14% relative bandwidth, which is enough for broadband communications at millimeter waves.

Noise temperature and beam pattern of an NbN hot electron bolometer mixer at 5.25 THz

We report the measured sensitivities of a superconducting NbN hot electron bolometer (HEB) heterodyne receiver at 5.25 THz. Terahertz (THz) radiation is quasioptically coupled to a HEB mixer with a lens and a spiral antenna. Using a measurement setup with black body calibration sources and a beam splitter in vacuo, and an antireflection coated Si lens, we obtained a double sideband (DSB) receiver noise temperature (TrecDSB) of 1150 K, which is nine times hν/2k, where h is the Planck constant, ν the frequency, and k the Boltzmann constant. In addition, the measured far field beam patterns of the integrated lens antenna show nearly collimated beams from 2.5 to 5.3 THz that allow reliable measurement of TrecDSB using the vacuum setup. Our experimental results in combination with an antenna-to-bolometer coupling simulation suggest that the HEB mixer can work well at least up to 6 THz, making it suitable for next generation of high-resolution spectroscopic space telescopes and, in particular, for the detection of the neutral atomic oxygen line at 4.7 THz.

Drastic influence of the half-bowtie resonances on the focusing and collimating capabilities of 2-D extended hemielliptical and hemispherical dielectric lenses

The interplay between the optical focusing and wavelength-scale resonant features of extended hemielliptical (EHE) and extended hemispherical (EHS) lenses is studied in the two-dimensional (2-D) formulation using highly accurate in-house software based on the Muller boundary integral equations. The influence of the half-bowtie (HBT) resonances on the focusing and collimating capabilities of medium-size EHE and EHS lenses made of silicon is characterized as a function of lens parameters and excitation conditions. As a result, factors determining the parasitic impacts of the HBT resonances on the performance of integrated lens antennas are highlighted.

Design and Characterization of 60-GHz Integrated Lens Antennas Fabricated Through Ceramic Stereolithography

Three integrated lens antennas made in Alumina and built through ceramic stereolithography are designed, fabricated and characterized experimentally in the 60-GHz band. Linear corrugations are integrated on the lens surface to reduce the effects of multiple internal reflections and improve the antenna performance. The lenses are excited by Alumina-filled WR-15 waveguides with an optimized dielectric impedance matching taper in E-plane. The main characteristics of the first two prototypes with corrugations of variable size are compared to those of a smooth lens without corrugation (third prototype). Experimentally their reflection coefficient is smaller than -10 dB between 55 GHz and 65 GHz, and their radiation characteristics (main beam, side lobe level, cross-polarization level) are very stable versus frequency. In particular, at the center frequency (60 GHz), the total antenna loss (including feed loss) is smaller than 0.9 dB and the radiation efficiency exceeds 80%.

Finite-difference time-domain simulations of the effects of air gaps in double-shell extended hemispherical lenses

The effects of parasitic air gaps on the input impedance and radiation characteristics of dense double-shell integrated lens antennas are studied numerically at millimetre waves using the finite-difference time-domain method. The lens core is made up of Macor or silicon, and is coated with a quarter wavelength matching layer. Two kinds of gaps are compared: they are located either (i) between both shells of the lens, or (ii) between the lens base and the feed substrate. We show that their impact is much more critical in the second case, and that it becomes dramatic for silicon lenses, even with very thin gaps (smaller than λ0/100); the three major observed effects are the following: (i) strong shift of the resonant frequency, (ii) beam broadening and directivity loss, (iii) increase of the side lobe level.