Linear Slot Array Research Articles

Enhanced-Bandwidth Center-Fed Linear Slot Array and its Multibeam Application

Enhanced-Bandwidth Center-Fed Linear Slot Array and its Multibeam Application

Design of a Low-Cost, Low-Sidelobe-Level, Differential-Fed SIW Slot Array Antenna with Zero Beam Squint

This paper presents a low-cost, low-sidelobe-level, differential-fed, substrate-integrated waveguide (SIW)-based slot array antenna with zero beam squint. The antenna consists of two identical six-way unequal power dividers (PDs) and a 6 × 16 slot array and is realized on a single-layer substrate. The six-way unequal PD provides tapered amplitude and in-phase excitation for six SIWs, and each of them has 16 radiating slots. The 1 × 16 linear slot array on each SIW is excited using a differential feed to avoid undesired beam squinting across its operating band. A two-way hybrid waveguide (WG)-to-SIW E-plane PD is developed to provide equal amplitude and out-of-phase excitation for two six-way unequal power dividers. Moreover, metallic decoupling walls are implemented between two adjacent linear slot arrays to reduce E-plane external mutual coupling. An antenna prototype is fabricated and experimentally verified. The fabricated antenna shows that the measured −10 dB reflection bandwidth is 7.15% (9.57–10.28 GHz), with the achieved gain ranging from 20.30 to 21.92 dBi. A stable boresight beam is observed over the entire operating band. Furthermore, at the designed frequency of 10 GHz, peak SLLs of −29.1 dB and −29.4 dB are achieved in the E- and H-plane, respectively.

Millimeter-Wave Near-Field-Focused Full 2-D Frequency Scanning Antenna Array With Height-Modulated-Ridge Waveguide

A millimeter-wave near-field-focused (NFF) full 2-D frequency-scanning antenna array is presented in this article. The proposed antenna is achieved by combining an NFF ridged-waveguide slot array with a double-layer folded focused progressive feeding network. The linear ridged-waveguide slot array antenna is designed with a height-modulated ridge to focus on the power in one direction. The folded feeding line with different length is used to generate the desired focused phase and frequency-dependent progressive phase shift in the other direction. In this case, as the working frequency is swept in the considered range, the inherent frequency-dependent behavior of the linear NFF leaky-wave antenna (LWA) allows a single-scanning sweep in one direction, whereas the focused progressive feeding network ensures multiple-scanning sweeps in the other direction. A full 2-D electronic scanning with no coverage blindness in the scanning area is achieved. To the best of our knowledge, the proposed NFF antenna array is the first design to achieve the full 2-D scanning focus in the near-field (NF) region only by sweeping the frequency, which means that the testing information in the NF region can be directly obtained with a certain band of frequency. This type of antenna is a good candidate in NF fast-scanning applications, e.g., electromagnetic imaging/detecting systems.

Ultra-Wideband Endfire Long-Slot-Excited Phased Array for Millimeter-Wave Applications

An ultra-wideband phased array with endfire radiation is proposed for millimeter-wave (mm-wave) applications. This array consists of a linear long slot array (LSA) source and a transverse-electromagnetic (TEM) horn radiator. For each unit, a Γ-shaped probe based on a substrate integrated coaxial line (SICL) is adopted to generate a primary slot source. Then, the slot flares in the E-plane with an exponential profile to form a horn unit. The antenna unit is studied with periodical boundaries (PBs) in simulation and operates from 15.4 to 46.4 GHz with active standing wave ratio (SWR) <; 3 for a scan angle of up to 45° in H-plane. To verify the design concept, two 1×16 finite arrays, Array-1 for 0° scan and Array-2 for 45° scan, are fabricated and tested. Over the operating band of 15.4-46.4 GHz, both arrays obtain good impedance matching in measurements with SWR <; 2.3. The measured gain varies from 11.8 to 19.1 dBi for Array-1 and from 10 to 16.9 dBi for Array-2 within 16-40 GHz. Besides, Array-2 exhibits a scan angle of 48° and an average scan loss of 2.4 dB. Moreover, both arrays achieve a radiation efficiency exceeding 73% because of employing the low-loss SICL feed network.

Slotted waveguide antenna with central trapped wave effect

ABSTRACTA new slotted waveguide antenna is proposed in this paper, which opens eight parallel slots along the longitudinal axis at the broad wall of the waveguide as radiation output facets. It has compact slot structure, which greatly reduces the size of the antenna, and the overall longitudinal size of the parallel slot facet is merely 3.8 mm (just slightly larger than half of the operating wavelength). The slot linear array design of the antenna achieves the central trapped wave radiation effect, avoids energy consumption at communication discontinuous zone, and enhances radiation efficiency. The operating bandwidth could be up to 10 GHz, with the center frequency of 85 GHz. The measured results match well with simulated results, and the gain is slightly higher than 9.0 dBi within the whole operating frequency range. The antenna has features of compact longitudinal structure, wide frequency band, stable gain, etc., and will have good application prospects in wireless communication.

SIW Corporate-Feed Network for Circular Polarization Slot Array Antenna

In this paper, multilayer feeding network for linear slot array antenna is studied. A substrate integrated waveguide (SIW) corporate-feed network for linear slot array antenna based on three layers is presented. This design has eight right-handed circularly polarized radiation elements, one power divider with SMA connector to SIW adapter structure and six SIW power divider by coupling slot method. The feed network and antenna structures has been designed at X-band frequency. The SMA to SIW power divider and SIW power divider by coupling slot has in-phase and out-of-phase feature, respectively. The proposed feeding method takes the advantages of miniaturization of structure compared with the corporate-feed network by T-junctions. Also, proposed network for feeding radiation elements, eliminated undesirable surface current of the coaxial connector transition, which reduction of these currents causes lower side-lobe level at the antenna radiation pattern. Dimensions of manufacture array structure are 132.8 * 23 * 2.4 mm3 and the substrate is Rogers RO4003c. This antenna has the capability to expand the number of elements and feed network for achieving higher gain. Due to the unidirectional radiation pattern, this antenna useful for monopulse radar and automotive radar applications.

Linear high‐gain bidirectional slot array fabricated by narrow bent metallic line

A linear high-gain slot array with bidirectional broadside radiation is proposed. By utilising a novel slot-energising approach, the slot array obtains a simple and compact geometry, which could be fabricated by a narrow bent metallic line. The slot array achieves an approximately constant magnitude distribution on a long radiating aperture by adopting proper slot elements arrangement and optimising the dimensions. Thus, compared to the existing bidirectional slot arrays in the open literature, the proposed slot array generates a higher gain and moderate gain-to-length ratio. To confirm the build strategy, a prototype with the length of 6.3 wavelength at the centre frequency of 2.4 GHz is constructed, fabricated, and tested, which realises a high gain of 14.0 dBi. With the merits of small size, high gain, low cost, and high-power capacity, the proposed slot array is an attractive substitute for various long-distance communication systems.

Automatic Design of a CP Fan-Beam Linear Slotted Array in SIW Technology

In this paper, we present a technique for the automatic optimization of a right-hand circular-polarized (RHCP) linear slotted array in substrate integrated waveguide (SIW) technology for the so-called “last-mile”communications, in which a narrow (broad) beam is required in the elevation (azimuthal) plane. The procedure can be divided into two steps; i) the optimization of isolated single slot pairs, by means of two physics-based functionals able to minimize both slot pair back-scattering and axial-ratio, ii) the optimization of the entire linear array of slot pairs, by means of a global functional able to match the co-polar component of the synthesized aperture distribution to the target one, i.e., a uniform magnetic current distribution to radiate a narrow beam in the elevation plane. A prototype of array was optimized at 24.3GHz and measured in the bandwidth [24.1, 24.5]GHz, showing a fair agreement against full-wave simulations, thus validating the exposed techniques.

Technique for Determination of Particulate Matter Pollution in the Atmosphere Using Waveguide Slot Linear Array Antennas: A Feasibility Study

Particulate atmospheric pollution alters the dielectric coefficient of the atmosphere. In principle, this could allow pollution to be measured via its effects on the performance of an antenna. In this letter, a novel technique for measuring these effects, based on the use of an optimized air-filled waveguide-fed slot linear array, is shown.

Demonstration of a micromachined planar distribution network in gap waveguide technology for a linear slot array antenna at 100 GHz

The need for high frequency antennas is rapidly increasing with the development of new wireless rate communication technology. Planar antennas have an attractive form factor, but they require a distribution network. Microstrip technology is most commonly used at low frequency but suffers from large dielectric and ohmic losses at higher frequencies and particularly above 100 GHz. Substrate-integrated waveguides also suffer from dielectric losses. In addition, standard rectangular waveguide interfaces are inconvenient due to the four flange screws that must be tightly fastened to the antenna to avoid leakage. The current paper presents a planar slot array antenna that does not suffer from any of these problems.The distribution network is realized by micromachining using low-loss gap waveguide technology, and it can be connected to a standard rectangular waveguide flange without using any screws or additional packaging. To realize the antenna at these frequencies, it was fabricated with micromachining, which offers the required high precision, and a low-cost fabrication method. The antenna was micromachined with DRIE in two parts, one silicon-on-insulator plate and one Si plate, which were both covered with Au to achieve conductivity.The input reflection coefficient was measured to be below 10 dB over a 15.5% bandwidth, and the antenna gain was measured to be 10.4 dBi, both of which are in agreement with simulations.

Wide-Band Slot Antenna Arrays With Single-Layer Corporate-Feed Network in Ridge Gap Waveguide Technology

Single-layer, wideband, and low-loss corporate-feed networks for slot antenna arrays are described. The antenna is built using ridge gap waveguide technology, formed between two parallel metal plates without the requirements of electrical contact between these plates. The corporate-feed network is realized by a texture of pins and a guiding ridge in the bottom plate, and the radiating slots are placed in the smooth top plate. The paper describes two test antennas: a 4 $\,\times\,$ 1 linear slot array and a 2 $\,\times\,$ 2 planar slot array. Both have been fabricated and tested at Ku- band. The linear array shows more than 20% bandwidth and the 2 $\,\times\,$ 2 array shows a bandwidth of 21% for 10-dB return loss. There are good agreements between measured and simulated patterns for both antennas. Measured gain for the planar array is found to be at least 12.2 dBi over 12–15 GHz band.

Excitation Control Method for a Low Sidelobe SIW Series Slot Array Antenna With 45$^{\circ}$ Linear Polarization

A sidelobe suppression method for a series slot array antenna which radiates 45° -inclined linear polarization is proposed. Axial displacements are employed to create arbitrary excitation coefficients for individual centered-inclined radiating slots along the center line of a broad wall. To verify the proposed design method, we design two types of center-fed linear slot array antennas with a Dolph-Chebyshev distribution for -20 dB and -26 dB sidelobe levels (SLLs) in the Ka band. Furthermore, a cross-validation process involving an equivalent circuit model analysis and electromagnetic full-wave simulation using CST MWS is utilized. The entire structure of the proposed series slot array antenna is fabricated on printed circuit boards (PCBs), including drilling and chemical etching, to secure advantages of miniaturization and cost reduction. The measured realized gains are 15.17 and 15.95 dBi and SLLs are -18.7 and -22.5 dB respectively for two types of fabricated antennas. It demonstrates the validity of the proposed sidelobe suppression method.

Optimum Design of Traveling-Wave SIW Slot Array Antennas

This paper presents an optimum design method based on the Method of Least Squares (MLS) for the traveling-wave substrate integrated waveguide (SIW) slot array antenna. Elliot's design formulas for dielectric filled waveguide including external and internal mutual coupling are used for the design by means of the equivalent waveguide. In order to achieve an efficient antenna, design formulas are extended to nonuniformly spaced slots. An error function consisting of four terms is formulated and then minimized with respect to the design parameters namely lengths, offsets, spacings and excitations of slots using combination of genetic algorithm and conjugate gradient method (GA-CG). A linear slot array at $X$ -band is designed, simulated and fabricated for verification. Results of the proposed method, simulation software and measurement are in good agreement.

Substrate Integrated Waveguide (SIW) Rotman Lens and Its Ka-Band Multibeam Array Antenna Applications

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 (-40deg, 40deg) X (-35deg, 35deg) or (-25deg, 25deg) x (-35deg, 35deg) 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 simultaneously required.

DESIGN AND OPTIMIZATION OF NONUNIFORMLY SPACED LONGITUDINAL SLOT ARRAYS

A new numerical method is presented for the design and optimization of linear arrays of nonuniformly spaced longitudinal slots on the broad wall of rectangular waveguides, based on the Method of Least Squares (MLS). Elliott’s design theory for travelling-wave-fed slot arrays is extended to nonuniformly spaced slots. As a common approach in MLS, an error function is formulated according to the design goals (namely the input impedance matching and pattern synthesis) and then minimized with respect to the design parameters (namely slot lengths, offsets, spacings and excitations). Having the slot parameters, one can design a linear slot array which accounts for the desired input impedance matching and array pattern. This approach has the advantage of combining the “nonuniform pattern synthesis”, which includes the external mutual coupling and element pattern of slots, with “impedance matching” and “calculation of the array parameters”. This procedure increases the design speed as well as synthesizing any desired pattern. The MLS design results and those obtained by HFSS simulation software are in good agreement and verify the accuracy of the proposed method.

Characterization of artificial magnetic conductor strips for parallel plate planar antennas

AbstractMetamaterial structures have unique properties in controlling the propagation of electromagnetic waves. In this work, we analyze the effect of artificial magnetic conductor (AMC) surface strips on the bottom face of an oversized parallel plate waveguide to enhance the wave guidance within it. The results using these configurations in a linear slot array antenna fed by a rectangular parallel plate waveguide are presented as an example of application. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 498–504, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23092

A Waveguide Broad-Wall Transverse Slot Linear Array with Reflection-Canceling Inductive Posts and Grating-Lobe Suppressing Parasitic Dipoles

A design of a linearly-polarized non-resonant waveguide broad-wall transverse slot linear array with suppressed grating lobes is presented. Each unit element in the array consists of a transverse slot, an inductive post and a parasitic dipole-pair at a height of half of the free space wavelength. It is designed as an isolated unit without considering mutual coupling by using the Method of Moments (MoM) for radiation suppression in grating beam direction and reflection cancellation at the input. The elements thus designed are used in a travelling wave array environment. It is predicted that the reflection is less than -20dB at 11.95 GHz while the grating lobes are suppressed by more than 15dB. The design and the characteristics of the array are confirmed by measurements.

Grating Lobes Suppression in Transverse Slot Linear Array with a Dual Parasitic Beam of Strip Dipoles

A new technique called the Dual Parasitic Beam (DPB) technique is proposed to suppress grating lobes in a rectangular waveguide broad wall transverse slot array. This technique involves an extra layer of parasitic strip dipoles that generate the DPB to suppress the grating lobes without opposing the main beam of the original slot linear array. A full wave EM analysis in Method of Moments (MoM) is conducted to compute the coupling excitation coefficients as well as the far field patterns of the slot and dipole currents. Analysis shows that a suitable dimension and arrangement of dipoles are needed to get a desired level of dipole excitations to meet the grating suppression condition. It is found that the grating lobes can be suppressed as much as 15 dB in the presence of the parasitic dipoles. Experiments are conducted to confirm the computed results.

A Direct Computation of the Frequency Response of Planar Waveguide Slot Arrays

An existing analysis technique, applicable only to linear waveguide slot arrays, has been extended to compute the frequency response of a complete planar slot array. The devised approach is a direct one and therefore significantly more efficient than already existing iterative procedures. The proposed approach is able to take into account also the frequency response of the coupling slots used in the beam forming network. The proposed technique has been validated through comparison with a commercial general-purpose CAD program.

Improved Design if Waveguide Slot Array Applicators For Microwave Heating

In this paper we consider the problem of optimizing the design procedure of a waveguide slot array applicator radiating a generic dielectric slab. To this end, we use a commercial simulation code to obtain empirical curves describing the behaviour of a single slot radiating on a dielectric slab with a given complex permittivity. Some results regarding a slot linear array applicator designed by using the calculated empirical curves are presented. A significant improvement in efficiency is shown for the slot linear array applicator with respect to a similar applicator designed by using a standard approximate analytical method.