Search

A 24-beams slot array antenna, which achieves 360-degrees coverage over azimuth direction, based on substrate integrated waveguide (SIW) technology is designed, fabricated and measured for supporting the concept of triangle cell, beam diversity and multiple input multiple output (MIMO) wireless communications. Constructed by six 4-beams single layer SIW antennas which integrate the 4 x 8 modified Butler matrix with a low side lobe level (SLL) amplitude distribution, measured SLLs are reduced as low as -14.5 dB for all beams in E-plane. The size of the SIW single layer multibeam antenna is 385 mm x 110 mm including feeding network. The usable bandwidth of the proposed antenna is 3.75% at 16 GHz. Index Terms--Beam-forming, Butler matrix, substrate integrated waveguide (SIW).

Transverse slot array antennas fed by a half-mode substrate integrated waveguide (HMSIW) are proposed and developed in this paper. The design concept of these new radiating structures is based on the study of the field distribution and phase constant along the HMSIW as well as on the resonant characteristics of a single slot etched on its top conducting wall. Two types of HMSIW-fed slot array antennas, operating, respectively, in X-band and Ka-band, are designed following a procedure similar to the design of slot array antennas fed by a dielectric-filled rectangular waveguide. Compared with slot array antennas fed by a conventional rectangular waveguide, such proposed HMSIW-fed slot array antennas possess the advantages of low profile, compact size, low cost, and easy integration with other microwave and millimeter wave planar circuits. It is worth noting that the width of HMSIW slot array antennas is reduced by nearly half compared to that of slot array antennas fed by a substrate integrated waveguide. Index Terms--Half-mode substrate integrated waveguide (HMSIW), transverse slot array antenna.

A fixed-beam frequency-tunable coplanar stripline (CPS) antenna array using the phase reversal technique and varactor diodes tuning is presented. The antenna array is composed of plurality of half-wavelength CPS sections interconnected by phase reversing crossovers. These crossovers have two functions: they serve as the radiators (small dipoles) of the array and also provide their own required in-phase excitations for broadside radiation. Two rnicrostrip-to-CPS transitions for excitation of the balanced input/output antenna array are implemented and compared. A six-element array is demonstrated theoretically and experimentally, with 9.3 dBi of gain for bidirectional radiation and 12.5 dBi of gain for unidirectional radiation using a back reflector. Moreover, shunt varactor diodes are incorporated along the CPS structure to achieve frequency tuning through a bias voltage control while broadside radiation patterns remain fixed. The return loss and the radiation patterns at several frequencies are presented, and up to 50% tuning range is obtained. The proposed antenna array is simple and uniplanar with small lateral size, high radiation efficiency and high directivity. In addition, it uses a very simple biasing circuit with high DC-RF isolation. Its balanced input/output makes it suitable for RF system integration and active integrated antenna design. Index Terms--Antenna array, coplanar stripline (CPS), phase reversal, tunability.

A Ka-band compact single layer substrate integrated waveguide monopulse slot array antenna for the application of monopulse tracking system is designed, fabricated and measured. The feeding network as well as the monopulse comparator and the subarrays is integrated on the same dielectric with the size of 140 mm x 130 mm. The bandwidth ([S.sub.11] < - 10 dB) of the antenna is 7.39 % with an operating frequency range of 30.80 GHz-33.14 GHz. The maximum gain at 31.5 GHz is 18.74 dB and the maximum null depth is -46.3 dB. The sum- and difference patterns of three planes: H-plane, E-plane and diagonal plane are measured and presented. Index Terms--Difference pattern, monopulse antenna, null depth, substrate integrated waveguide, sum pattern.

A novel substrate integrated waveguide (SIW) multibeam antenna based on the parabolic reflector principle is proposed and implemented at 37.5 GHz, which takes the advantages of low loss, low profile, high gain, and mass producible. A prototype of the proposed antenna with seven input ports generating a corresponding number of output beams is fabricated in a standard PCB process. The measurements are in good agreement with the simulations, and the results demonstrate that this type of printed multibeam antenna is a good choice for communications applications where mobility and high gain are simultaneously required. Index Terms--Beamforming network, multibeam antenna, parabolic reflector, substrate integrated waveguide (SIW).

The dual V-type linearly tapered slot antenna (DVLTSA) is a modified version of the Vivaldi radiator and is first introduced here. It is much more compact and keeps the advantages of the conventional tapered slot antenna (TSA). Furthermore, this antenna is suitable for a monopulse antenna owing to its special configuration. Both the sum and difference beams can be generated only employing a single DVLTSA respectively through the multimode substrate integrated waveguide (SIW) feeding technology. With detailed theoretical analysis, a prototype of the monopulse antenna proposed at the center frequency of 36 GHz was integrated on a single substrate using the normal PCB process. Measured gain of the sum beam is 10.6dBi, while the zero depth of the difference beam is lower than -35 dB. It also has good cross-polar characteristics and can be applied over a broad bandwidth as well. Index Terms--Linearly tapered slot antenna (LTSA), monopulse antenna, multimode, substrate integrated waveguide (SIW).

A new type of substrate integrated waveguide (SIW) multibeam antenna is proposed for mobile satellite communications using beam switching and diversity techniques. It employs an SIW Rotman lens as the beamforming network. The prototype of a single multibeam antenna is implemented at 28.5 GHz with seven input ports and an antenna array constructed by nine SIW linear slot arrays, which can generate a corresponding number of beams along one dimension. Several such antennas are grouped in two different ways to cover a 2-D solid angle with multiple beams. Experiment results show that the 2-D solid angle around (-40[degrees], 40[degrees]) x (-35[degrees], 35[degrees]) or (-25[degrees], 25[degrees]) x (-35[degrees], 35[degrees]) are covered with 20 or 25 beams with 5-dB beamwidth, respectively. It is demonstrated that this type of printed multibeam antenna is a good choice for communication applications where mobility and high gain are simultaneonsly required. Index Terms--Beamforming network (BFN), multibeam antenna, Rotman lens, substrate integrated waveguide (SIW).

A compact two-dimensional (2-D) finite-difference time-domain (FDTD) method is proposed to analyze the propagation characteristics of arbitrary guiding structures. By transforming electromagnetic field variables into new forms of periodic variables, which also can be resolved from the Maxwell's equations, one can convert the 2-D transmission line problem into an equivalent resonator problem based on the idea of translating the transmission distance-related attenuation part of complex propagation constant into a time-dependent damping factor. As a result, the FDTD method for resonator can be made use of to simulate the lossy guiding structures. Attenuation constants can be obtained by means of the quality factors of equivalent resonators. It means that some leaky wave antennas can also be analyzed by using this method. Numerical simulations show that the proposed method can quickly and accurately extract the phase constants and attenuation constants of lossy guiding structures. Index Terms--Complex propagation constant, equivalent resonator, finite-difference time-domain (FDTD) method, leaky wave antenna, quality factor.

A compact linear array antenna fed by substrate integrated image guide (SHG) at 94 GHz is presented. The SIIG is a low-loss dielectric waveguide which is synthesized directly on a high dielectric constant substrate or semiconductor wafer. Such a low-cost approach of integration allows for the development of directive low profile antennas for future commercial millimeter-wave products. Special attention was directed towards the radiation elements that are fabricated in printed circuit technique on top of the SHG. Their novel design provides a wide tuning range for the radiation coefficient and excellent linear polarization purity. In addition, an optimized reflection compensation technique effectively reduces the overall return loss and permits frequency scanning through broadside direction without suffering from a stop band due to distributed Bragg reflection. Published theory concerning the scan range of this class of frequency-scannable array antennas is extended in this work. Detailed design guidelines are given along with simulation and measurement results of a prototype. The 2 cm long implementation produced a fan beam with 11 dB gain. Index Terms--Antenna array feeds, dielectric waveguides, leaky waves, millimeter-wave antennas, substrate integrated image guide, substrate integrated circuits.

An integrated module with filtering and radiation performance realized by covering substrate integrated waveguide (SIW) cavity frequency selective surface (FSS) at aperture of horn antenna has been investigated in this paper. The module has functions of bandpass filter and horn antenna, so it is called a 'filtering antenna' (filtenna). It is very suitable for applications in military platforms where FSS is used for antennas and radars' radar cross section (RCS) reduction. The filtenna is simulated and optimized with CST software and its performance is verified by experiments. From simulated and measured results it can be found that the proposed structure keeps characteristics of return loss, radiation pattern and gain of the horn antenna within desired frequency band, meanwhile presents effective reflection to interference signals at out-band. Using this structure the volume and cost of communication systems in military platforms can be effectively reduced. Index Terms--Antenna, filtenna, frequency selective surface (FSS), horn, substrate integrated waveguide (SIW).

A novel frequency selective surface (FSS) based on substrate integrated waveguide (SIW) technology is investigated with simulation and experiment. The periodic unit is made of a SIW cavity with slots on the top and bottom surfaces, and the whole FSS is fabricated on a microwave substrate with standard PCB process. The high-Q property of SIW cavities greatly improved the frequency selectivity of the FSS, which is significant for the application in antenna cover or object stealth etc. The finite difference frequency domain (FDFD) method is adopted to simulate the transmission and reflection characteristics of the proposed FSS, and the simulated results are in good agreement with the experiment data. Both simulated and experiment results show that the FSS proposed in this paper takes the advantages of low passband insertion loss, good frequency selectivity, and insensitive to the incident angle and polarization etc. Besides, the FSS can be easily fabricated using normal PCB process with low cost. Index Terms--Cavity, finite difference frequency domain (FDFD), frequency selective surface (FSS), periodic structure, substrate integrated waveguide (SIW).

A hybrid scheme that incorporates the method of finite elements, the method of lines, variational techniques, and conformal mapping is proposed for the analysis of guided-wave structures. This technique is devised to analyze complex waveguide structures with irregular composite geometries, High numerical accuracy is maintained by treating key singularities by semianalytical procedures. Compared with the conventional method of lines with finite difference techniques, the proposed scheme is able to solve many complex guided-wave problems with fewer mesh lines without compromise on accuracy. This gain is due to the added variable mesh-directions and the flexibility in the method of finite elements in choosing appropriate functions for fitting the configuration of concern. Index Terms--Guided-wave problems, method of finite elements, method of lines, variational analysis.

A new finite plane wave series expansion for spherical wave functions of the first kind is presented in this paper. The formulation converts the spherical wave function described in the spherical coordinate system into a series of plane wave functions represented in the Cartesian coordinate system. The series expansion will be very useful in modal analysis of three dimensional guided wave structures and scatterers containing planar boundary surfaces. For a given range of orders m and degree n and for a region with [bar]r < R, the same set of plane waves can be used. The theory is numerically verified for a wide range of parameters, showing its fast convergence characteristics. The plane wave expansions of the vector multipole fields can also be obtained. Index Terms--Electromagnetic theory, guided waves, modal analysis, scattering, waveguide.

In this paper, experimental and analytical investigations of unidirectional dielectric radiator arrays (UDRA) are presented for the first time. Attractive electrical performance due to the use of nonradiating dielectric waveguide (NRD) structures is demonstrated. A numerical model based on a cavity-resonator approximation is developed for prediction of radiation properties of the UDRA's. Good agreement between measurements and calculations shows the validity of the modeling approach. On the other hand, the feed technique for the UDRA by microstrip line and coupling-aperture is experimentally investigated. Measurement results show high coupling and radiation efficiencies of the proposed excitation method. Such a circuit configuration allows the combination of planar millimeter-wave M(H)MIC's and NRD components in one system for the best use of different technologies.

An accurate and efficient technique is presented for the analysis of large microstrip antenna arrays. The technique consists of an amalgamation of a spatially discrete scheme, consisting of the CG-FFT method and the complex discrete image (CDI) technique. The unique feature of this approach is the use of the spatially discrete CG-FFT for analyzing microstrip structures. The aliasing and truncation errors are thoroughly eliminated in this approach. In addition, the grad-div operators are transformed from singular Green's functions to differentiable expansion and testing functions by using Galerkin's procedure, thereby improving the accuracy and the rate of convergence. To show the accuracy and efficiency of this technique, a number of microstrip arrays, including a large microstrip reflectarray, have been studied. It is found that the simulations carried out using this technique are in very good agreement with measurements.