Silicon Waveguide Frequency Scanning Linear Array Antenna

The design and experimental findings of a novel approach a relatively simple low-cost frequency-scanning milliter-wave antenna are described. The antenna consists of a silicon dielectric rectangular rod with periodic metallic stripe perturbations on one side. The feasibility of electronically scanning through a range of angles by varying the frequency fed into the silicon rod is shown. CalcuIations were made to determine the allowable physical size of the silicon rod in order to maintain a single fundamental mode of operation and the effect which size variations and perturbation spacing have on the angle of radiation and the range of angular scan for a given frequency shift. Efforts covered the frequency range 55-100 GHz with specific points of interest at 60, 70, and 94 GHz. The results of the experiments conducted are compared with the theoretical calculations.     

Grating Lobe Suppression of Narrow-Wall Slotted Hollow Waveguide Millimeter-Wave Planar Antenna for Arbitrarily Linear Polarization

A high-gain and high-efficiency slotted waveguide planar antenna is developed in the millimeter-wave band. Forty-five degree inclined polarization is required for automotive radar systems. In the design of slotted waveguide array for arbitrarily linear polarization, slot spacing is one guide wavelength which is larger than a wavelength in free space. Consequently, grating lobes appear in the radiation pattern. So, we developed a slotted waveguide planar antenna composed of post-loaded narrow-wall slots and a single-layer alternating-phase feeding circuit. A planar antenna with suppressed grating lobes has been fabricated and its RF performance has been measured. The measured gain is 33.2 dBi and antenna efficiency is 56% at 76 GHz. Grating lobe level is -28.6 dB lower than main lobe level. Since the proposed structure remains simple, the antenna is expected to be manufactured by metal injection molding for low cost     

Electronic Modulated Beam-Steerable Silicon Waveguide Array Antenna

The design and experimental findings for a low-cost easily fabricated millimeter-wave line scanner is described. This antenna consists of a 1-mm x 1-mm silicon dielectric rod with a metal grating (periodic structure) on the upper surface and p-i-n diodes mounted on the sidewall. A narrow 8/spl deg/ beam is radiated from the grated (perturbed) surface at an angle dependent on the guide and perturbation spacing. The beam angle is switched over a 10/spl deg/ angle by application of a dc forward current through the p-i-n diode modulators.     

Horn Image-Guide Leaky-Wave Antenna

A novel structure for a frequency-scanning millimeter-wave antenna is described. The antenna is constructed by embedding a dielectric leaky-wave antenna in a long trough with metal flares attached along both sides. The optimum flare angle for achieving maximum gain is theoretically predicted. The design of the leaky-wave antenna, which is comprised of metallic-strip perturbations on top of the dielectric guide, is also discussed.     

Surface emitting characteristics of silicon waveguides

This paper concerns the surface emitting characteristics of silicon waveguides in the millimeter-wave frequency band. The waveguides used in the experiment are rectangular slabs of high resistivity silicon (30,000 ohm-cm). A series of periodic perturbations on the waveguide surface provide a radiating antenna. A rectangular grating with a period of Λ=1.8 mm, a height of 0.35 mm, and a duty cycle of 0.46 was sawn into the top surface of a silicon waveguide with a width of 3 mm and a height of 1.41 mm. Experiments were performed to measure the attenuation, dispersion and the radiation characteristics of the waveguides. The test setup was used to monitor the frequency, radiation angle, and the radiated power. Measurements are made over a band of frequencies around the second Bragg frequency. The detector was scanned from 88–95 GHz and changes were observed in the attenuation constant, dispersion relation and the far field radiation pattern. From these results we were able to verify the grating theory.     

Radiation properties of a planar dielectric waveguide loaded withconducting-strip diffraction grating

A dielectric planar waveguide periodically loaded with conducting strips is considered as a possible antenna for millimeter-wave range. We show that separating the grating from the waveguide leads to the reduction of radiative attenuation of the waveguided radiation and substantial narrowing of the angular spread of the diffracted radiation     

Metallized Dielectric Horn and Waveguide Structures for Millimeter-Wave Oscillator/Mixer Systems

A new method of producing millimeter-wave oscillator/mixers and associated antenna horns has been developed. This uses the technique of metal coating of dielectric body, and hence avoids the expensive and difficult machining of conventional metal cavities. A sensitive self-oscillating mixer has been tested in this structure and shown to be free from the unstable operation associated with surface radiation of unshielded dielectric waveguide. Low epsilon/sub r/ dielectric was used, thus facilitating ease of matching in contrast with the high epsilon/sub r/ necessary with the unshielded guide.     

An analysis of the radiation from circular arrays of directive elements

A simple analytic formula for the radiation of the angular harmonics excited by a large cylindrical array is derived. The dependence of the phase on elevation angle and cylinder diameter relative to a wavelength is shown and compared to an exact solution. The difference between a continuous distribution and discrete array is presented; and the angular phase perturbations produced by the discrete array are also derived. The results can be used for computing the radiation field produced by multiple harmonic excitation of the array, and indicate the effect of the element pattern, number of elements, and spacing.     

Transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with a dielectric slab

A compact and wide-band transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with an H-plane -dielectric slab is presented in this paper. By partially filling an H-plane dielectric slab in the waveguide, the inter-element spacing between slots is reduced to be about 0.8 free-space wavelengths to avoid grating lobes. In addition, the partially filled material provides extra flexibility to adjust the slot impedance as desired within a relatively wide frequency range. A new feeding network is designed for this antenna array, which can prevent the shift in the pointing angle of the array's main radiation beam with the change of frequency. Experimental data for a 2/spl times/4 antenna array operating at X-band show that stable radiation pattern over a wide frequency range can be obtained. The measured gain is 16.9 dB at 10 GHz and the fluctuation is less than 2 dB over a frequency band of 1.5 GHz. The slot array's 10-dB return loss bandwidth is 13% and the cross-polarization level is better than -25 dB.     

Experimental analysis of metal coated dielectric waveguides

This paper concerns the experimental characteristics of metal coated dielectric waveguides with a rectangular surface corrugation. Waveguide are designed to operate at a second Bragg frequency of 90 GHz. The period, height and the duty cycle of a rectangular grating were calculated using the chosen frequency. A metallic layer of aluminum is sputtered on one side of the slab waveguide. The purpose of the metallic layer is to simulate a layer of high density plasma on the surface of the waveguide similar to that obtained by optical excitation of semiconductor structures. Experiments were performed to examine the far field radiation pattern, attenuation constant and the dispersion relation. Due to the presence of the plasma layer there will be an angular shift in the far field radiation pattern. We have observed angular shifts of about 20? in the radiation pattern of the waveguide before and after coating. Measurements are made in the frequency range of 88–95 GHz. This waveguide structure can be used to design an electronically steerable antenna and an electronic phase shifter operating in the millimeter-wave frequency band.     

Antennas and waveguides for far-infrared integrated circuits

Antennas and waveguides for the wavelength range 0.1-3 mm are considered. Emphasis is placed on those designs which lend themselves to integration with each other and with other components such as diodes. The general properties of FIR antennas are reviewed. A novel silicon waveguide antenna is discussed, and its design, simulation, fabrication, and performance at 119 μm are described. This antenna has a highly symmetrical, single-lobed beam with 3 dB beamwidths of 35 and 38° in theE- andH-planes, respectively. The gain (measured in microwave simulation) is 12.8 dB. This antenna is well suited for integration with Schottky diodes. The related subject of FIR waveguides is discussed. Experiments with metal transmission lines at 119 μm are described and dielectric guides related to the waveguide antenna are also considered. Using components such as these it may soon be possible to construct receiver front ends for this wavelength range in integrated-circuit form.     

Circularly polarized dielectric-loaded planar antenna excited bythe parallel feeding waveguide network

A new receiving planar array antenna for DBS (direct broadcasting satellite) is proposed. The element antenna is a short waveguide aperture mounted in the ground plane, loaded with a dielectric and polarizers, and excited through its side wall by another feeding rectangular waveguide. The gain of the element antenna loaded with a dielectric is so high that the grating lobes can be reduced sufficiently even if the element spacing in the array is wider than the wavelength in free space. Therefore we can reduce the number of the array elements, and parallel feeding by the low loss waveguide network can be feasible to provide a planar array antenna. This paper describes the experimental results of several kinds of the circularly polarized dielectric-loaded element antennas and the planar antennas fed by the waveguide network. In the 12 GHz band the planar antenna with 64-element radiators has a maximum gain of 31.9 dBi with an aperture efficiency of 94.7%, the 1 dB-down frequency bandwidth of the gain is about 800 MHz (6.7% for a center frequency of 11.85 GHz), and the frequency bandwidth of the axial ratio is less than 1 dB of 850 MHz (7.2%)     

94 GHz dielectric slab-line leaky-wave antenna

A leaky-wave planar antenna for millimetre-wave frequencies is described using a dielectric slab line, fed by a slotted waveguide array. The radiation of the planar antenna is induced by line discontinuities such as metallic discs on the guide surface.     

Trough waveguide dual-frequency antenna

A new type of dual-frequency antenna using a hollow-fin trough waveguide is described. The hollow fin is used as aTE_{10}mode waveguide with sidewall radiating elements. These Sidewall radiating elements constitute the high-frequency section of the antenna. The low-frequency section consists of a thick hollow-fin trough waveguide antenna. The attenuation due to radiation and waveguide wavelength of the trough waveguide section are analyzed. This analysis shows good agreement with experimental measurements. Existing data may be used as a guide in the design of the high-frequency section of this antenna, and the data presented may be used as a guide in the design of the low-frequency section.     

Periodic metal plate-loaded dielectric slab antenna with broadsideradiation

Wave guiding properties of a periodic metal plate-loaded dielectric slab structure are investigated for obtaining surface wave antennas with broadside radiation and low voltage standing wave ratio (VSWR) characteristics. A novel technique is proposed in which dielectric phase transformers play an essential role for realizing a uniform phase distribution on the radiating aperture which is required to achieve broadside radiation. A quarter-guided wavelength spacing of the metal plates guarantees the suppression of reflections at the input port. On the basis of the theoretical results obtained, two types of antennas have been designed at 10 GHz, one having the exponential aperture distribution, the other the uniform aperture distribution. The overall antenna efficiency of the latter type has been found to be 53%, exhibiting a practical performance at microwave frequencies     

The design of a slot array in nonradiating dielectric waveguide, part I: Theory

A set of theoretical design equations for a slot array fed by nonradiating dielectric (NRD) waveguide is developed. Mutual coupling between the slots cut into one of the metal walls of the waveguide is taken into consideration for a design that can have a predetermined radiation pattern. The theoretical development follows that of Elliott.     

Millimeter-wave beam steering using "Diffraction electronics"

Periodic structures placed near a dielectric waveguide can cause the combined structure to radiate. The direction of radiation is controlled by the period or spacing of the elements in the structure. In the present study a simple coiled spring provided the periodic structure. Beam steering at 94 GHz over the range of80degto166degwas achieved by flexing of the spring. The half-power beamwidth is determined by the total effective length of the structure at the radiated angle. The experimental results indicate that a relatively low-cost beam-steerable antenna for fan-type beams may be constructed.     

宽角扫描的圆极化相控线阵

设计了一款宽波束的圆极化天线单元以及1×4的天线阵列，实现了一维的宽角圆极化扫描.天线单元由单层的辐射贴片和介质基片集成波导（substrate integrated waveguide，SIW）背腔构成，通过在辐射贴片上切角微扰和开U型槽实现右旋圆极化，并利用SIW背腔缝隙展宽波束.同时利用SIW背腔减小阵列单元间的互耦，实现宽角圆极化扫描.仿真与测试结果表明，天线阵列实现了扫描角为-53°~57°，3 dB波束宽度覆盖范围为-76°~79°，在主波束扫描覆盖范围内轴比（axial ratio，AR）均小于3 dB，且在扫描范围内增益变化平稳，可实现良好的宽角范围的圆极化扫描特性.     

Scattering of Surface Waves by Discontinuities on a Unidirectionally Conducting Screen

It is shown that a plane screen consisting of closely-spaced parallel wires which are separated from one another and which are such that the radius of the wires and the spacing between them are small in comparison to wavelength, can support a surface wave, the spread of whose field components depends only on the angle which the direction of propagation makes with the direction of the wires. The problem of radiation from a discontinuity in such a semi-infinite waveguide is studied for the following three types of discontinuities: 1) when the waveguide terminates in empty space, 2) when it terminates at another such semi-infinite waveguide having different propagation characteristics, and 3) when it terminates at a perfectly conducting half-plane. In each case, the power reflection coefficient, where applicable the power transmission coefficient, the loss of power due to radiation, and its angular distribution are evaluated. The motivation for this investigation is briefly indicated.     

An electronically switchable leaky wave antenna

We report an electronically switchable dielectric leaky wave antenna. The main beam angle can be electronically steered using p-i-n diodes. The diodes are used as switches to control the radiation from two sets of gratings with different periods, thereby switching the main beam angle. Beam steering is achieved at a single fixed frequency; no frequency sweeping is necessary. A microwave prototype demonstrates a 35° change in beam direction at 3.5 GHz. Measured antenna patterns agree with theoretical predictions. This approach should be scalable to millimeter-wave frequencies using diodes monolithically integrated on a semiconductor waveguide