A dual-band periodic structure is here proposed, which allows for versatile frequency selectivity and polarization conversion functionality. The structure is a monolithic full-metal piece, and it is built from the arrangement of unit cells consisting of waveguide sections at cutoff loaded with compound perforations. The topology of such unit cells enables the efficient and independent interaction with vertical and horizontal electric field components illuminating the periodic structure. A circuit model is proposed to characterize the cells and understand their behavior. Three different examples of cells are designed to illustrate the structure versatile functionality. One of these examples is manufactured, consisting of a dual-band structure that converts linear polarization into circular with orthogonal senses of rotation at each band. The experimental results are in good agreement with the theoretical predictions, thus validating the underlying operation mechanism and its practical feasibility.

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All-Metal 3-D Frequency-Selective Surface With Versatile Dual-Band Polarization Conversion

This paper introduces a rectangular grating waveguide slot array antenna that provides a method for the design of satellite communication (SATCOM) receiving antennas. By integrating the radiating slots with a rectangular grating waveguide, which functions as a frequency-selective transmission line, the antenna realizes an extra filtering response. The operation bandwidth and out-of-band rejection of the antenna can be tuned by adjusting the rectangular grating waveguide parameters. In order to verify the proposed design concept, a prototype $Ku$ -band eight-slot rectangular grating waveguide slot array antenna is designed, fabricated, and measured, and its performance is compared with that of the conventional eight-slot rectangular waveguide slot array antenna. The results show that the proposed antenna works well in the receiving frequencies of 12.25–12.75 GHz and suppresses the realized gains with additional measured 14.8–21.3 dB in the transmitting frequencies of 14.0–14.5 GHz, which confirms its extra filtering response. Simultaneously, the measured antenna efficiency of the proposed antenna (68.3%–88.8%) is similar to that of the conventional antenna (66.9%–84.6%).

Rectangular Grating Waveguide Slot Array Antenna for SATCOM Applications

The design of a shared-aperture waveguide slot antenna operating in dual-band and dual-polarization (DBDP) is proposed in this letter for synthesis aperture radar (SAR) applications. The frequencies of the antenna are in both L- and C-band with frequency ratio of 4:1. The C-band horizontal-polarized subarray antenna is achieved by 16 V-shaped slots opened on a ridged waveguide, while the vertical-polarized subarray is realized by 16 longitudinal slots displaced from the centerline on the other ridged waveguide. The L-band vertical-polarized subarray is comprised by four groups of longitudinal slots cut in the metal-wall interlacing with the C-band dual-polarized antenna array sharing the same aperture. The L-band waveguide is a multiridge cavity under the C-band waveguide. A DBDP antenna module comprising 4 × 16 C-band dual-polarized elements and 1 × 4 L-band elements was manufactured in aluminum alloy. Experimental results show that the proposed antenna can obtain excellent electromagnetic performance and maintain satisfactory thermal and mechanical properties for space-borne SAR applications.

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Dual-Band Dual-Polarized Waveguide Slot Antenna for SAR Applications

In this article, a square enclosed circle split ring resonator (SEC-SRR) based metamaterial is described that shows negative permittivity (ENG) with near-zero-index (NZI) of refraction. The unit cell of this metamaterial is formed with two SRR rings, one with square in shape and another circular shaped. The inner circular SRR has related to the outer square SRR by the metal strip. The analyzed design is very simple, but the outcome of this recommended unit cell is high i.e., it covers the multiband S-, C-, and X- bands. Rogers is used as a substrate to design the proposed SEC-SRR that has a thickness of 1.524 mm. The unit cell has a dimension (electrical) of 0.070λ × 0.070λ. The simulation software CST microwave studio-2019 is used to identify transmission (S21) and reflection (S11) coefficient and from this knowledge relative permittivity, permeability and refractive index is obtained by using MATLAB code based on Nicolson-Ross-Wier (NRW) method. The simulated resonance frequencies are 2.61, 6.32 and 9.29 GHz with well-matched to the measured ones. The negative permittivity regions are obtained in 2.63–2.87 GHz, 6.39–7.45 GHz, and 9.37–9.52 GHz covering S-, C-and X-bands, respectively. The equivalent circuit is modeled in Advanced Design Software (ADS) and verified by comparing obtained S21 with CST output. The designed unit cell also exhibits NZI property, and high effective medium ratio (EMR) of 14.37 at lower resonance frequency. The applicability of NZI property of this ENG metamaterial has been investigated by applying for gain enhancement of LPDA antenna. Due to its near zero refractive index, negative permittivity, high EMR and simpler design, the proposed metamaterial can be utilized for S-, C-, and X-bands applications, especially for improving the gain of satellite and radar antennas with special features.

Square enclosed circle split ring resonator enabled epsilon negative (ENG) near zero index (NZI) metamaterial for gain enhancement of multiband satellite and radar antenna applications

With wireless communication technologies continually and rapidly developing, RF front-end systems are experiencing a profound evolution toward the goal of highly integrated and miniaturized RF front ends with improved performance. Traditionally, passive components in the RF front end, such as filters, antennas, and duplexers, have been designed individually and cascaded through a 50-Ω interface. This inevitably leads to bulky physical dimensions and complex circuits, high insertion loss, and signal distortion, especially at the band edges. In multiband or multistandard communication systems, multiple operating bands of the base station antenna are normally achieved using several separate subarrays operating at different frequencies, which can cause serious interference among different bands for various services due to the limited space on the antenna platform. Highly integrated multifunctional RF front ends would provide a high-efficiency solution to those advanced and miniaturized wireless systems. As the key components in any RF front-end system, the integration of filters and antennas can significantly improve the frequency selectivity and bandwidth; stability of the in-band gain, out-of-band rejection, and system efficiency. They have therefore received much research interest and opened up a broad avenue for antenna R&D in recent years.

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Filtering Antennas: Design Methods and Recent Developments

A broadband waveguide slot filtenna array with low cross polarization and high efficiency is presented for dual-polarization applications. The vertical polarization radiation is achieved by offsetting longitudinal slots on the ridged waveguide, while the horizontal polarization radiation is achieved by V-shaped slots on the ridged waveguide. Two polarization ridged waveguide linear arrays combine to obtain dual-polarized radiation with cross-polarization levels under −43 dB in wide angles. To extend the bandwidth of the array, each $1 \times 16$ -element linear array is separated into two $1 \times 8$ -element arrays, which are fed by a two-way ridged waveguide divider via H-shaped slot couplings. The evanescent-mode ridged waveguide filters are integrated into a two-way ridged waveguide divider that suppresses the out-of-band signal interference. The signals of the interference bands are suppressed effectively, which are −25 dB lower than that of the operation band. Furthermore, 16 pairs of dual-polarized linear arrays are designed, fabricated, and measured. The results show that the array has perfect properties such as bandwidth, polarization purity, efficiency, and immunity to interference.

Broadband Dual-Polarized Waveguide Slot Filtenna Array With Low Cross Polarization and High Efficiency

A novel waveguide slot filtering antenna with an embedded metamaterial is presented. This filtering antenna consists of a common waveguide slot antenna with longitudinal slots cut on the top broad wall of its rectangular waveguide and a metamaterial surface embedded in the bottom broad wall. The metasurface replaces the conventional metal plane in the form of a bed of nails. In the operating frequency band, the metasurface works as a perfect electric conductor, so the antenna radiates as the traditional waveguide slot antennas. While in the stopband, the metasurface performs as a perfect magnetic conductor to suppress the propagation of electromagnetic wave in the waveguide cavity, so the interference signal is rejected and a filter function is achieved. To show the design process and verify its feasibility, a filtering antenna prototype working in the $C$ -band and having a stopband in the $X$ -band is designed, fabricated, and tested. A good agreement between simulation and measurement is obtained, demonstrating efficient radiations in the working band and a strong suppression of more than 35 dB in the stopband.

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A Waveguide Slot Filtering Antenna With an Embedded Metamaterial Structure

A mushroom-type surface-based waveguide slot filtering antenna is proposed herein. First, using a mushroom-type surface replacing the conventional metal plane in the bottom of a rectangular waveguide, a novel filtering waveguide is achieved. This filtering waveguide functions as a bandstop filter when the surface performs as a perfect magnetic conductor. Then, a filtering waveguide slot antenna is obtained by cutting radiating slots on the top of the filtering waveguide. Compared with a traditional waveguide slot antenna, the proposed antenna has nearly the same radiation characteristic while realizes an additional filter selectivity with almost no extra volume occupancy. A prototype is demonstrated in Ku -band with operating in 12.25–12.75 GHz and rejecting over 14.0–14.5 GHz, which can be a candidate for receiving antenna of satellite communication. The measured results agree well with the designed ones, showing a suppression level stronger than 40 dB in the rejecting band.

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A Compact Waveguide Slot Filtering Antenna Based on Mushroom-Type Surface

In this letter, a Vivaldi antenna with wideband RCS reduction using Electromagnetic Band Gap Absorbing Structure (EBGAS) is designed. The EBGAS coveres on the antenna ground. The EBGAS constructed by split rectangular ring loaded with resistors and dielectric spacer. Compared with the metal ground Vivaldi antenna, RCS has reduced about 15 dB in the frequency band of 4–18 GHz and almost without gain loss. This antenna has wideband scanning ability, can be used for phased array antenna stealth design.

Hongtao Zhang

Papers

Broadband Dual-Polarized Waveguide Slot Filtenna Array With Low Cross Polarization and High Efficiency

A Waveguide Slot Filtering Antenna With an Embedded Metamaterial Structure

Dual-Band Dual-Polarized Waveguide Slot Antenna for SAR Applications

A Compact Waveguide Slot Filtering Antenna Based on Mushroom-Type Surface

Wideband RCS reduction of vivaldi antenna using electromagnetic band gap absorbing structure