Millimeter-wave and terahertz integrated circuit antennas

A comprehensive review of integrated circuit antennas suitable for millimeter and terahertz applications is presented. A great deal of research was done on integrated circuit antennas in the last decade, and many of the problems associated with electrically thick dielectric substrates, such as substrate modes and poor radiation patterns, have been understood and solved. Several antennas, such as the integrated horn antenna, the dielectric-filled parabola, the Fresnel plate antenna, the dual-slot antenna, and the log-periodic and spiral antennas on extended hemispherical lenses, which have resulted in excellent performance at millimeter-wave frequencies, are covered in detail. A review of the efficiency definitions used with planar antennas is included     

Double-slot antennas on extended hemispherical and elliptical quartz dielectric lenses

In this paper, the theoretical far-field patterns and Gaussianbeam coupling efficiencies are investigated for a double-slot antenna placed on quartz hemispherical lenses with varying extension lengths. The radiation patterns of the double-slot antenna are computed using ray-tracing inside the lens and electric and magnetic field integration on the spherical dielectric surface. The theoretical results are equally valid for double-dipole, log-periodic, and spiral antennas, and are presented in extension length/radius and radius/λ. Therefore, the results yield universal design curves for quartz lenses of different diameters and at different frequencies and using different antennas. The results indicate that forsingle units, there exists a wide range of extension lengths (ext. length/radius=0.61 to 0.76) which result in high Gaussian-coupling efficiencies to moderately highf/# systems. Forimaging array applications with high packing densities, an extension length/radius=0.82 to 0.93 (depending on frequency) will result in peak directivity and highest packing density but lower Gaussian-coupling efficiencies.     

Far-field pattern analysis of 94 GHz extended hemispherical lens monopulse antennas

In this paper, the far-field patterns are investigated for double-slot antenna array placed on extended hemispherical lenses. The radiation patterns of the extended hemispherical lens fed by single double-slot antenna or double-slot antenna array are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The computation results show that the sharp null of the difference pattern is below -37dB.     

Off-axis properties of silicon and quartz dielectric lens antennas

The theoretical far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed off aids on extended hemispherical silicon and quartz lenses. Measured off-axis radiation patterns at 250 GHz agree well with the theory. Results are presented that show important parameters versus off-axis displacement: scan angle, directivity, Gaussicity, and reflection loss. Directivity contour plots are also presented and show that near-diffraction limited performance can be achieved at off-axis positions at nonelliptical extension lengths. Some design rules are discussed for imaging arrays on dielectric lens antennas     

Ray tracing on extended hemispherical and elliptical silicon dielectric lenses

In this paper, extended hemispherical and elliptical silicon dielectric lenses are compared by means of ray tracing. It is shown that the optical focuses of two lenses are not at same position though the elliptical lens is synthesized from an extended hemispherical lens by carefully choosing a particular extension length as stated in ref[1]. It may be used to explain why the best compromise between alignment, directivity and Gaussian-coupling effciency will be obtained if the feed antenna is placed at the region between 2.2 mm and 2.4 mm of extension length (for 13.7 mm diameter lens, dielectric contant = 11.7).     

High-power constant-index lens antennas

The results of a study to develop a high temperature dielectric lens antenna for use in the microwave frequency range are presented. The design and fabrication of spherical and hemispherical constant-index lenses are described. Radiation patterns, gain, polarization, and VSWR characteristics of spherical and hemispherical constant-index dielectric lens antennas over the frequency range from 2 to 11 GHz are presented. The results from high-power testing of both spherical and hemispherical constant-index lenses at a 2 kW average power level indicate that this power level causes no degradation in the performance of the lenses.     

The dielectric-filled parabola: a new millimeter/submillimeterwavelength receiver/transmitter front end

A design is presented for a semi-integrated millimeter/submillimeter wavelength receiver/transmitter front end incorporating a planar antenna and a solid-state device in an efficient feed structure which can be matched directly to high f-number optical systems. The feed system combines the simplicity and robustness of a dielectric substrate lens with the high gain of a parabolic reflector in a single structure that is termed a dielectric-filled parabola. The same fundamental unit can be configured as either a heterodyne or direct detection mode receiver, a power transmitter or a frequency multiplier by changing out the solid-state device and/or the integrated antenna. The structure can also be used with a small integrated antenna array in a multibeam or imaging arrangement. Design and fabrication details for the feed system are given. These are followed by beam pattern and impedance measurements taken on a microwave model when dipole, bow-tie, log-periodic, and log-spiral antennas are used as the integrated feed elements     

Double-slot antennas on extended hemispherical and ellipticalsilicon dielectric lenses

Far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed on hemispherical lenses with varying extension lengths. The radiation patterns of a double-slot antenna on a silicon dielectric lens are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The measured radiation patterns at 246 GHz and Gaussian-beam coupling efficiencies show good agreement with theory. The theoretical results are presented in terms of extension-length/radius and radius/λ, and therefore result in universal design curves for silicon lenses of different diameters and at different frequencies. The theoretical and experimental results indicate that for single units, there exists a wide range of extension lengths which result in high Gaussian-coupling efficiencies (50-60%) to moderately high f 's. These Gaussian-coupling efficiencies can be increased to 80-90°% with the use of a λ_m/4 matching-cap layer. For imaging array applications with high packing densities, an extension-length/radius of 0.38 to 0.39 (depending on frequency) will result in peak directivity and a corresponding Gaussian-coupling efficiency 15-20% lower than for single units     

An improved solution for integrated array optics in quasi-opticalmm and submm receivers: the hybrid antenna

A dielectric lens antenna that is a special case of an extended hemispherical dielectric lens and is operated in the diffraction-limited regime is considered. The dielectric lens antenna is fed by a planar antenna that is mounted on the flat side of the dielectric lens antenna, using it as a substrate, and the combination is termed a hybrid antenna. Beam pattern and aperture efficiency measurements were made at millimeter and submillimeter wavelengths as a function of the extension of the hemispherical lens and of lens size. An optimum extension distance for which excellent beam patterns and simultaneously high aperture efficiencies can be achieved is found experimentally and numerically. At 115 GHz the aperture efficiency was measured to be (76±6)% for a diffraction-limited beam with sidelobes below -17 dB. Results for a single hybrid antenna with an integrated superconductor-insulator-superconductor (SIS) detector and a broadband matching structure at submillimeter wavelengths are presented. The hybrid antenna is space efficient in an array due to its high aperture efficiency, and is easily mass produced, thus being well suited for focal plane heterodyne receiver arrays     

Performance of reduced size substrate lens antennas for Millimeter-wave communications

This paper presents the theoretical performance (input impedance, -10 dB return-loss bandwidth, radiation patterns and surface efficiencies) of reduced size substrate lenses fed by aperture-coupled microstrip patch antennas. The diameter of the extended hemispherical homogeneous dielectric (/spl epsiv//sub r,lens/) lenses varies between one and five wavelengths in free-space, in order to obtain radiating structures whose directivity is comprised between 10 and 25 dB. A lot of configurations of lenses are investigated using the finite-difference time-domain methods technique and compared in the 47-50 GHz band as a function of their diameter, extension length and dielectric constant. In particular, the analysis of internal reflections-in time and frequency domains-shows that the latter have potentially a strong influence on the input impedance of small lens antennas, even for low values of /spl epsiv//sub r,lens/(2.2), whereas the usual limit (beyond which anti-reflection coatings are required) is /spl epsiv//sub r,lens/=4. We also demonstrate that the diffraction limit of reduced size lenses is reached for extension lengths varying between 50% and 175% of the extension of synthesized ellipses, depending on the lens material and diameter. Finally, we show that superdirective structures with surface efficiencies reaching 250% can be obtained with small lens diameters, justifying the interest in reduced size lens antennas.     

Generation of microwave radiation by active antennas with field-effect transistors locked by an external signal

Effects of locking by an external electromagnetic field of an array of oscillator antennas (OAs) designed by field-effect transistors integrated with log-periodic antennas are analyzed. The possibility of spatial combining of the radiation powers of OAs placed on a common dielectric substrate and arranged into a 1D array is demonstrated. It is shown that application of external locking can ensure severalfold broadening of the locking band of an ensemble of independent self-oscillators as compared to the case of mutual locking by a common field propagating in the dielectric substrate.     

毫米波扩展半球透镜／物镜天线系统辐射特性分析

采用射线追踪和场积分的方法分析了扩展半球透镜／物镜天线系统的辐射特性，给出了计算结果，表明该系统具有良好的辐射特性。通过改变扩展半球透镜的扩展长度，可以实现集成电路与各种准光系统的耦合，具有很强的实用价值。     

Electromagnetic Radiation by Antennas of Arbitrary Shape in a Layered Spherical Media

A unified method of moments model is developed for the analysis of arbitrarily shaped antennas that are radiating next to a multilayered dielectric sphere. The curvilinear Rao-Wilton-Glisson triangular basis functions and dyadic Green's functions have been used in the model. Antennas of various geometries including spherical, circular and rectangular microstrip antennas as well as hemispherical dielectric resonators have been modeled. Input impedance and radiation pattern results are presented and shown to be in good agreement with published data.      

Synchronization and combining of the radiation powers of active microwave antennas integrated with field-effect transistors

Combining of the powers of microwave generators designed as a array of log-periodic antennas on a dielectric substrate and field-effect transistors as active components is experimentally investigated. Possibilities of a substantial increase in the generation efficiency due to mutual synchronization of radiators are demonstrated, and conditions for formation of the radiation pattern are studied.     

Whispering gallery modes in a dielectric resonator:characterization at millimeter wavelength

Applications of whispering-gallery-mode (WGM) dielectric resonators in the millimeter and submillimeter frequency range are discussed. A summary of the main peculiarities of these resonators is given, and a method to obtain approximate analytical expressions of electromagnetic field components is developed. Problems connected with the excitation by far infrared (FIR) laser radiation are examined. The analysis of electromagnetic propagation in different structures drives the best choice for the transmission line (metallic and dielectric waveguides), and the same theoretical analysis allows to face the basic problem of optimizing the matching between transmission-line and WG resonators; the role in this application of dielectric waveguides with variable diameter is discussed. All of the predictions are obtained in a unified theoretical picture. The experimental characterization of a WG resonator at 240 GHz involved the measurement of the effectiveness of the coupling between the transmission line and the resonator, the determination of the merit factor and free spectral range for the different resonance families in different resonators. Accurate measurements were carried out to acquire knowledge of the field distribution in both axial and radial directions; to this purpose, dielectric antennas with high directivity were used to sense the field intensities for different resonance modes. The good agreement between the experimental results and the theoretical predictions is carefully discussed     

Design of Dielectric Grating Antennas for Millimeter-Wave Applications

At theoretical procedure well suited for generating design data on dielectric grating antennas for the millimeter-wave region is presented. The procedure utilizes the effective dielectric constant (EDC) method to determine the phase constant of the leaky modes supported by the antenna structure of finite lateral width. The radiation or leakage constant of these modes is obtained from the relatively simple boundary value problem of dielectric grating antennas of infinite width. For single-beam radiation, the practicably interesting case, the phase and leakage constants completely determine the field distribution in the antenna aperture, from which the directivity gain and radiation pattern are then calculated. The dependence of the antenna characteristics on the dimensions of the radiating structure is presented and discussed for epsilon = 12, the dielectric constant of typical millimeter-wave materials, such as silicon and GaAs.     

The annular aperture antenna with a hemispherical center conductor extension

An annular aperture antenna mounted on an infinite ground plane and containing a hemispherical center conductor extension above the ground plane is investigated. A Green's function for the region above the ground plane is derived so as to be compatible with numerical solution techniques. A magnetic field integral equation is obtained in terms of the unknown tangential aperture electric field and is solved by the method of moments. A comparison between flush mounted and hemispherically extended annular aperture antennas is presented for the tangential aperture electric field, the coaxial line apparent input admittance, and the far radiated field.     

Synthesis of new variable dielectric profile antennas via inverse scattering techniques: a feasibility study

In this paper, we investigate whether and how one can synthesize given far field patterns by acting on the dielectric profile of a lens antenna. In particular, an approach to design a radiating system consisting of a variable dielectric profile and a single or a low number of feeds is proposed and discussed. To properly take into account physical and practical feasibility issues, the proposed method splits the problem into two steps. The first one is aimed to fix design goals (i.e., the nominal field), in such a way to avoid super-directive or physically unfeasible antennas and properly exploits known properties of electromagnetic fields radiated by finite extent sources. The second step, dealing with the dielectric profile synthesis, is based on suitable modifications of inverse scattering techniques and can take into account constraints on the spatial behavior as well as of dielectric characteristics of the profile to be synthesized. To show the interest of the subject, as well as effectiveness of the proposed approach, the synthesis of new dielectric antennas, such as a high directivity source and a lens radiating a steerable degradation-free Chebyshev pattern, is considered in the two dimensional scalar case.     

A new accurate design method for millimeter-wave homogeneous dielectric substrate lens antennas of arbitrary shape

The synthesis and the optimization of three-dimensional (3-D) lens antennas, consisting of homogeneous dielectric lenses of arbitrary shape and fed by printed sources, are studied theoretically and experimentally at millimeter(mm)-wave frequencies. The aim of the synthesis procedure is to find a lens profile that transforms the radiation pattern of the primary feed into a desired amplitude shaped output pattern. This synthesis problem has been previously applied for dielectric lenses and reflectors. As far as we know, we propose, for the first time, to adapt and implement it for the design of substrate lens antennas. The inverse scattering problem is solved in two steps. In the first one, the geometry of the 3-D lens is rigorously derived using geometrical optics (GO) principles. The resulting second-order partial-differential equation is strongly nonlinear and is of the Monge-Ampe/spl grave/re (M.A) type. The iterative algorithm implemented to solve it is described in detail. Then, a surface optimization of the lens profile combined with an analysis kernel based on physical optics (PO) is performed in order to comply with the prescribed pattern. Our algorithms are successfully validated with the design of a lens antenna radiating an asymmetric Gaussian pattern at 58.5 GHz whose half-power beamwidth equals 10/spl deg/ in H plane and 30/spl deg/ in E plane. The lens is illuminated by a microstrip 2/spl times/2 patch antenna array. Two lens prototypes have been manufactured in Teflon. Before optimization, the measured radiation patterns are in very good agreement with the predicted ones; nevertheless, the -12 dB side lobes and oscillations appearing in the main lobe evidence a strong difference between the desired and measured patterns. This discrepancy is significantly reduced using the optimized lens.     

Microstrip Antenna–Oscillators Integrated with a Waveguide Built in a Dielectric Substrate

The design of a microwave oscillator based on a microstrip log-periodic antenna integrated with a field effect transistor and a waveguide built in a dielectric substrate has been developed and analyzed. The waveguide geometry provides the possibility of propagation and radiation at both the fundamental frequency of the log-periodic antenna and harmonics. Computer simulation of the oscillator design in a frequency range near resonance frequencies of the log-periodic antenna is conducted. The possibility of summation of powers of several antenna–oscillators arranged ias a linear phased array is investigated.