Microstrip patch antenna feed for offset reflector antenna for dual band application

In this article, details of a dual band microstrip patch antenna (MPA) array feed for an offset reflector antenna is presented. The main objective of the proposed structure is to achieve low cross‐polarization at Φ = 90° plane in the reflector pattern. Low cross‐polar levels in the reflector pattern are achieved by illuminating the reflector with fields of the proposed dual band feed structure. A centered circular array as the dual band feed structure is proposed in which the central radiating element is a dual mode circular MPA operating at 6 GHz and the surrounding circular ring of eight circular MPA elements operating at 4 GHz in the dominant mode. The dual mode central antenna uses the concept of conjugate field matching for cross‐polarization reduction. TM₂₁ mode is excited at an appropriate ratio with the TM₁₁ mode to achieve the proper field matching at 6 GHz. The radius of the surrounding circular array is varied to obtain cross‐polarization better than ?30 dB at both the resonant frequencies. The offset reflector gain is found to be better than 37 dB with a 2.5 m parabolic reflector and F/D = 0.8 at both the operating frequencies.     

Single‐feed wideband circularly polarized patch antenna using dual mode defected ground waveguide coupling structure

A dual mode square‐ring defected ground waveguide (SR‐DGW) with defected square patch is first proposed to excite a single‐feed dual mode circularly polarized (CP) patch antenna, which can improve the impedance bandwidth and achieve the CP radiation pattern. The defected square patch is called the perturbation element. By optimizing the size of the perturbation, the degenerate modes of the dual mode SR‐DGW are split and their orthogonal modes can be excited simultaneously. Due to the dual mode of the SR‐DGW, the TM₀₁ mode, and TM₁₀ mode of the square patch antenna are excited simultaneously, which can improve the impedance bandwidth of the antenna. Meanwhile, owing to the orthogonal modes, CP radiation pattern of the antenna is obtained. Then, for a better impedance matching, an L‐shaped spurline embedded in the feedline is introduced. The simulated and measured results show a good performance of the proposed antenna. The measured ?10 dB impedance bandwidth is 10.4% (3.56 GHz‐3.95 GHz). The measured 3 dB axial ratio bandwidth is 5.36% (3.63 GHz‐3.83 GHz). Detailed designs and experiments are described and discussed.     

Integrated circular polarized microstrip antenna with dual‐mode‐polarization insensitive characteristics

A dual‐mode circularly polarized compact antenna with integrated left‐hand and right‐hand circular polarization (LHCP and RHCP) is presented in this work. A multilayer arrangement of a square patch and square ring structure with an irregular transmission line is analyzed for dual‐band, dual‐CP operation. To realize dual mode propagation the proposed structure is excited using electromagnetic coupling technique. Succeeding proximity feeding with T‐stub match is analyzed, which conveys impedance bandwidth of 180 and 300 MHz within |S₁₁| < ?10 dB at 3.5 and 5.5 GHz. The designed CP elements is suitably arranged with feed line for generating two orthogonal polarization of equal amplitude and a 90° phase difference at both the resonant modes (TM₁₀ and TM₀₁). Alterable LHCP and RHCP performance is realized by altering the compensated position and peculiar angle. Having both LHCP and RHCP polarization this design shows polarization insensitive characteristic. Each LHCP and RHCP antenna element accomplished a 3‐dB AR of 70 and 120 MHz with a gain up to 6 dBi. With a low profile of 0.27λ₀ × 0.27λ₀ × 0.04λ₀, the CP antenna is fabricated, and the performance is validated through experimental analysis. With all the viable characteristics, the antenna is proposed for Wi‐MAX/WLAN communication.     

A dual‐band dual‐mode microstrip Yagi antenna with quasi‐end‐fire radiation

A dual‐band dual‐mode microstrip Yagi antenna with quasi‐end‐fire radiation patterns is proposed in this paper. It consists of five radiating patches driven by a single slot‐loaded patch placed in the middle. Meanwhile, two slot‐loaded parasitic patches are symmetrically located on two sides of the driven patch, respectively. In the lower band, the five patches involved resonate at TM₀₁ mode. While in the upper band, all the patches resonate at TM₀₂ mode. In order to ensure quasi‐end‐fire radiations in the both bands, four slots are symmetrically etched around the strongest surface currents of each patch resonating at TM₀₂ mode. As a result, the resonant frequency of TM₀₂ mode is decreased dramatically, while the resonant frequency of TM₀₁ mode almost remains unchanged. With these arrangements, the separations between any two of the adjacent patches at their centers satisfy the requirements in design of the microstrip Yagi antenna in both bands, so as to realize the dual‐band dual‐mode microstrip Yagi antenna on a single‐layer substrate. Finally, an antenna prototype is fabricated and tested. The measured results reveal that the dual operating bands of 2.76~2.88 and 4.88~5.03 GHz for |S₁₁| < ?10 dB are satisfactorily achieved. Most importantly, the proposed antenna can indeed realize the quasi‐end‐fire radiation patterns in dual operating bands.     

Dual circularly polarized loop antenna using a pair of resonant even‐modes

Conceptual design of dual circularly polarized (CP) square loop antennas using a pair of resonant even‐modes for wireless sensor application is presented. A pair of even‐modes is simultaneously excited within a single, nonuniform square loop element and employed to realize a dual circular polarization characteristic. When the natural boundary conditions of the even‐modes and the feed lines are matched, respectively, a bidirectional dual CP loop antenna can be attained at first. Then, a unidirectional dual CP loop antenna is designed by introducing a simple metallic reflector. Both bidirectional and unidirectional designs exhibit dual CP performance with available operation bandwidth of 10.0% and 8.5%. The design approach is expected to get applications in dual CP antenna designs for wireless sensor systems.     

A multi‐mode wideband omnidirectional monopolar patch antenna for indoor wireless communication systems

A wideband omnidirectional monopolar patch antenna merged multi‐mode with a simple structure is proposed in this article. The antenna consists of a circular patch and a concentric annular ring, which is coupled‐fed by a T‐shape monopole at its center. A wideband performance is achieved by converging multi‐mode: TM₀₂ mode of the circular patch, TM₀₂ mode of the annular ring and monopole mode of the T‐shape monopole. The measured results show that the proposed antenna has an impedance bandwidth of 55.3% from 4.45GHz to 7.85GHz. All of the three resonant modes lead to conical radiation patterns in the elevation plane and omnidirectional radiation patterns in the azimuth plane, and the measured peak gain varies from 6.1 to 10 dBi within the operating band, which verifies it can be a good choice for indoor wireless communication systems.     

A TM03 mode reduced side lobe high‐gain printed antenna array in K band for UDN and IoT applications in 5G

A single layer simple feed reduced side lobe gain‐enhanced microstrip antenna array using higher‐order modes is analyzed and designed in this work. The relationship between the relative magnitude of equivalent magnetic currents and directivity are studied. Modal analysis for rectangular patch is considered for broadside and non‐broadside radiation. Comparative investigations on antenna radiation and impedance characteristics for fundamental and higher‐order modes are presented. It is observed that an array can be designed to operate in TM₀₃ mode for enhanced gain with broadside radiation. Parametric optimization is carried out to attain low side lobe level. The proposed theory is validated by designing and fabricating a single layer single feed 2 × 2 microstrip patch array in the K band operating in TM₀₃ mode. The simulated and measured realized gain of the fabricated TM₀₃ mode array is 16.1 and 15.5 dBi, respectively, at 22 GHz with consistent broadside radiation pattern and linear polarization.     

Dual‐band circularly polarized antenna with harmonic suppression performance

A dual‐band circularly polarized (CP) antenna with harmonic rejection property is proposed in this paper. Four T‐shaped slits and two corner cuts are etched on the proposed microstrip patch antenna. Those structures can be used to tune the resonant frequencies of TM₀₁ mode and TM₀₃ mode of the antenna into the desired bands of 2.45 and 5.8 GHz with CP radiation. A shunt transmission line is employed not only to improve the impedance matching at 5.8 GHz but also to suppress the radiation at 4.9 GHz (second harmonic of 2.45 GHz). Meanwhile, two L‐shaped slits are etched on the feeding line to realize the harmonic rejection at 11.6 GHz (second harmonic of 5.8 GHz). The simulated and measured results show that this antenna has good dual‐band CP radiation property and harmonic suppression performance, which makes it a good candidate for the wireless energy harvesting system.     

Direct and electromagnetically coupled compact microstrip antenna design with modified fractal DGS

This article proposes ultra‐miniature microstrip patches with direct and electromagnetically coupled feeding mechanism for wireless communications at 10 GHz. Antenna size reduction is achieved here by loading a modified Minkowski fractal (type‐2) defected ground structure (MFDGS‐II) exactly beneath the radiating patch. The proposed method involves the selection of best DGS configuration through sensitivity analysis of the antenna structure. From different applications point of view, three different designs: a single layer direct fed patch and two electromagnetically coupled fed multi‐layered microstrip patch antennas are proposed here and designed with MFDGS‐II. The resonant frequencies of the antenna designs are reduced in a significant manner incorporating MFDGS‐II without any change in the physical size of the antenna. The prototypes of the proposed antennas are fabricated, and the performance parameters are measured. Compared with other existing structures, with a lower patch size of 0.20 λ₀ × 0.15 λ₀, the proposed single layered antenna with microstrip feed achieves a patch size reduction up to 67% and an overall volumetric reduction of 84%, respectively. Similarly, the proposed multi‐layered patch with proximity feed exhibits a maximum impedance bandwidth of 600 MHz and the aperture coupled fed patch has a realized gain of 6.2 dBi with radiation efficiency of 91% centered at 10 GHz. All three proposed compact antenna structures are best in three different aspects and have the potential to meet the practical requirements for X‐band portable wireless applications.     

A novel microstrip Yagi antenna with an improved end‐fire radiation pattern under operation of the TM20 mode

In this article, a novel microstrip Yagi antenna under operation of the TM₂₀ mode is proposed to obtain an enhanced end‐fire radiation pattern. First, a two‐element microstrip Yagi antenna is theoretically analyzed under different dimensions of the parasitic element. The results demonstrate that the parasitic element can act as either a reflector or director when its size is smaller or larger than the size of the driven patch, respectively. After that, the equivalent magnetic currents and electric fields of the two‐element antenna are formed to provide physical insight into the working principle and radiation performance of the antenna. With these arrangements, an array of four patch elements including one driver, one director, and two reflectors are selected for the antenna design. Unlike the traditional microstrip Yagi operating with the TM₁₀ mode, all the patch elements involved in this design resonate with the TM₂₀ mode, thus effectively enhancing the tilted beam angle toward the desired end‐fire direction on an infinite ground. Finally, the proposed antenna is designed, fabricated and tested. The measured results show that its impedance bandwidth is maintained at approximately 3.3%, ranging from 4.76 to 4.92 GHz. Most importantly, the maximum deviation angle of the antenna is significantly improved to approximately 58° from the broadside direction at the center frequency (4.84 GHz), while maintaining a low profile and compact size.     

Bandwidth and gain improvements of low‐profile H‐shaped microstrip patch antenna under quadruple‐mode resonance

A wideband low profile H‐shaped microstrip patch antenna (MPA) with reallocated quadruple‐mode resonance is presented for indoor wireless communication application. In this paper, the TM₂₀ (mode 1), TM₀₂ (mode 2), TM₂₂ (mode 3), and additionally notch mode 4 of the proposed MPA are simultaneously employed. First, the rectangular radiating patch is reshaped as an H‐shaped radiator so as to separate a pair of degenerate modes (mode 1 and mode 2). Then, a pair of linear notches is cut on the diagonal of the patch to excite an additional notch resonance (mode 4). Finally, in order to improve the frequency of mode 1, four shorting pins are placed at the four corners of the H‐shaped patch. Therefore, the bandwidth of the antenna is dramatically increased up by utilizing four resonant modes (modes 1, 2, 3, and 4). A prototype of H‐shaped patch antenna with notches and shorting pins is manufactured and measured. The results show that the antenna achieves a broad bandwidth of about 31.7% (2.31‐3.18 GHz), and its profile is only 0.036 wavelength of center frequency. It is particularly noticed that a relative high gain of around 9.8 dBi is successfully acquired, while keeping relative stable dual‐beam radiation patterns.     

Generalized design approach to compact wideband multi‐resonant patch antennas

In this work, a generalized design approach to compact, wideband multi‐resonant microstrip patch antenna is proposed. Theoretical criterion of the length of the prototype dipole is laid down based on the simplest dipole model and the associated eigenmodes at first. Then, the criterion is employed to reveal the general relationship between the prototype dipole length, operational modes, sizes, and radiation behaviors of the resultant multi‐resonant circular sector patch antennas. Next, a compact wideband, dual‐resonant circular sector patch antenna is designed accordingly. It is operating at the TM_3/4,1 and TM_9/4,1 modes within a 240° circular sector patch radiator with its radii short circuited. The antenna fabricated on a single‐layered air substrate exhibits an available radiation bandwidth of 25.0%, with a profile as small as 0.043 guided wavelength at the center frequency. It is evidently verified that the approach can be employed to realize compact, dual‐resonant wideband microstrip patch antennas without increasing antenna profile, inquiring multiple radiators or employing reactance compensation techniques. In addition, it may lead to a series of novel wideband patch antenna designs with diverse performances.     

Metasurface cavity antenna for broadband high‐gain circularly polarized radiation

The article presents a microstrip patch (MSA) fed high gain circularly polarized metasurface cavity (CP‐MSC) antenna using a planar progressively‐phased‐reflector and a transmissive linear to circular polarization conversion metascreen. The bottom metasurface reflector consists of a remodeled Jerusalem cross to obtain 2π reflection phase variation. Linear to circular polarization conversion is achieved by a hexagonal ring based meta‐element with high transmission and bellow 3 dB axial ratio from 9.5 to 10.5 GHz. Simulated and measured results of assembled CP‐MSC antenna with MSA are in good agreement. The gain of the proposed cavity antenna with 10 and 10.5 GHz MSA are 14.9 and 16.3 dBi, respectively. Below 3 dB AR throughout the operating band denotes significant circular polarization performance of the proposed antenna.     

Hybrid wideband dual‐cylindrical circularly polarized dielectric resonator antennas excited with S‐shaped microstrip feed for sub‐6 GHz frequency range

In this article, a hybrid microstrip fed dual‐cylindrical dielectric resonator antenna (dual‐CDRA) has been proposed for the sub‐6 GHz band application with a wide circular polarization band. The proposed hybrid microstrip feed cylindrical dielectric resonator antenna utilizes an S‐shaped microstrip feed line to excite fundamental HE_11δ like mode and hybrid mode in dual‐CDRAs. The presented antenna structures are acting as monopole antenna separately with 48.75% (3.88‐6.38 GHz) bandwidth whereas both radiators called dual‐CDRAs enhances the bandwidth up to 93.06% (2.16‐5.92 GHz) in addition with an axial ratio bandwidth of 15.2% (3.52‐4.1 GHz). The proposed antenna is applicable for WiMAX (3.4‐3.69 GHz), and WLAN application of 802.11d and 8.02.11e IEEE standard. For validation of simulated results, an antenna prototype has been fabricated and experimentally verified. A good agreement between simulation and measured results are obtained. The simulation results have been carried out by using Ansys HFSS 14.0 version software.     

A low‐profile circularly polarized dielectric patch antenna and array

A square dielectric patch (DP) resonator fusing with the bottom substrate is studied for designing low‐profile circularly polarized (CP) antenna. Based on the theoretical investigation using the constructed analysis model, it can be found that the proposed DP resonator possesses a pair of degenerate dominate modes (TM₁₀₁ and TM₀₁₁), which can be split by introducing perturbations on the DP resonator and then used to design CP antenna fed by a microstrip line directly. To verify the proposed idea, a 2 × 2 array fed by a dual Marchand balun network is designed and implemented. Reasonable agreement between the measured and simulated results is observed. Experimental results show that a measured impedance bandwidth is 380 MHz (5.18‐5.56 GHz) for |S₁₁| < ?10 dB and the 3‐dB axial ratio bandwidth is 90 MHz (5.32‐5.41 GHz). The measured gain is up to 11.77 dBic with a cross polarization of about ?20 dB in the boresight direction.     

Hybrid cylindrical dielectric resonator antenna with HE11δ and HE12δ mode excitation for wireless applications

In this article, dual mode triple band hybrid cylindrical dielectric resonator antenna (CDRA) for different wireless applications is investigated. It is seen that annular ring shaped patch along with T‐shaped printed line behaves as a magnetic and electric dipole concurrently and create HE_11δ and HE_12δ mode in the proposed CDRA. Both of the hybrid modes radiate in broadside direction. The concept of hybrid antenna (the combination of annular ring patch and CDRA) is used to achieve triple‐band feature in the proposed antenna. Ansoft HFSS‐EM simulator is used to optimize the proposed antenna. Optimized simulated results have been practically confirmed by using the archetype of proposed antenna. The proposed radiator is applicable in three different frequency bands, that is, 2.24‐2.56 GHz, 3.28‐4.18 GHz, and 5.36‐5.8 GHz. It is appropriate for WLAN (2.4/5.8 GHz) and WiMAX (2.5/3.3/5.5 GHz) applications.     

A dual‐feed microstrip grid array antenna for balanced or unbalanced operation

The development of a dual‐feed microstrip grid array antenna for either balanced or unbalanced operation to radiate pencil‐beam patterns has been described. As an example, the dual‐feed microstrip grid array antenna on RT/duroid 5880 substrate with a size of 60 × 60 × 0.787 mm³ or 4.8λ × 4.8λ × 0.063λ at 24 GHz were designed and fabricated. The measured results show that the dual‐feed microstrip grid array antenna has achieved excellent performances: 4.85% impedance bandwidth, 9.03% gain bandwidth, and 20.6‐dBi gain at 24.15 GHz as a balanced antenna and 6.05% impedance bandwidth, 7.74% gain bandwidth, and 17.8‐dBi gain at 24.15 GHz as an unbalanced antenna. The dual‐feed microstrip grid array antenna is a suitable antenna candidate for radar and sensor applications.     

Broadband conical beam antenna in planar environment

In this article, a substrate‐truncated microstrip circular patch antenna with shorting vias is proposed for X‐band applications. The bandwidth of the designed antenna is substantially increased by making two slots—one circular and another annular ring—at the top of the structure which actually helps in bringing two individual resonating frequencies closer to each other. The antenna is simulated using the Ansoft HFSS, and various parameters are optimized for better performance. The deigned structure is finally fabricated and tested, and the measured data fairly agree with the simulated results. The measured relative impedance bandwidth (|S₁₁| < ?10 dB) is found to be 28.5% (8.9‐11.85 GHz). The proposed antenna is behaving like a monopole with the radiated beam of conical shaped in the entire operating band having a maximum gain of 7.2 dBi.     

A substrate integrated cavity‐fed dual‐polarized filtering patch antenna with high isolation

This article presents a dual‐polarized filtering patch antenna, which uses two orthogonal modes (TE₂₁₀/TE₁₂₀) of the substrate integrated cavity (SIC) to couple with two orthogonal modes (TM₁₀/TM₀₁) of the patch by the cross slot, respectively. The second‐order filtering response on dual polarizations can be achieved by using just one SIC resonator and one slotted square patch, which display simple structure of the proposed antenna. The slotted square patch provides a new way to obtain same external quality factor of the radiator on dual polarization, which makes the performances on two polarizations agree well with each other when changing the bandwidth. High isolation can be achieved by controlling the space of the vias of the SIC. Radiation nulls can be produced by connecting the coupled lines with the feeding lines in parallel. A prototype with the entire height of 0.019 λ₀ (λ₀ is the free‐space wavelength at center frequency) achieves a 10‐dB bandwidth of 1.6%, the gain of 4.9 dBi at the center frequency, the port isolation of 43 dB, and the out‐of‐band rejection level of 25 dB.     

Hybrid polarized microstrip antenna for multifrequency application

In this article, a novel single layer, single‐fed ring antenna is analyzed for multiresonance operation in WLAN/Wi‐MAX bands. The antenna geometry consists of a square patch with a dual square ring enclosure which commit multiresonance characteristics. The antenna is excited using electromagnetically from a separate feed patch placed in between the rings. The impedance characteristics are enhanced up to 18% using a unique hourglass type feed patch in between the square rings. The suggested antenna exhibits good return loss at 2.45, 3.5, and 5.8 GHz having bore sight gain response of . Hybrid polarization is comprised with circular polarization and dual‐linear polarization characteristics are investigated in this research work. This antenna was implemented on Arlon's substrate with dielectric constant ?r = 2.55 and substrate thickness h = 1.524 mm. A good axial ratio is achieved with optimized corner truncation.