Mitigating Unwanted Mode in a Microstrip Patch by a Simpler Technique to Reduce Cross-Polarized Fields Over the Orthogonal Plane
18 Feb 2021-IEEE Antennas and Wireless Propagation Letters (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 20, Iss: 5, pp 678-682
TL;DR: In this paper, a strategic metal pole has been introduced to control the modal current of an orthogonal higher mode (TM02) but leaving the fundamental radiating mode untouched, and the pole height can be reduced by 40% −63% by accepting a tradeoff in XP suppression by 3 dB.
Abstract: This letter explores a new concept for the first time to control a specific unwanted higher mode in a microstrip patch with a target to reduce its cross-polarized (XP) radiation over the orthogonal plane. A strategic metal pole has been introduced to control the modal current of an orthogonal higher mode (TM02) but leaving the fundamental radiating mode (TM10) untouched. The conjecture has been successfully verified in S -band. The approach is the simplest of all explored earlier, requiring no multiparameter optimization or fabrication complexity except requiring an additional vertical space. Antenna impedance and primary radiations are insensitive to this technique but it ensures 11dB XP suppression over the orthogonal plane. The pole height can be reduced by 40%–63% by accepting a tradeoff in XP suppression by 3 dB.
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TL;DR: In this article , the surface current distribution in a rectangular microstrip patch is modified to reduce the H-plane cross-polarized (XP) radiations along with minimizing the backside radiation to some extent.
Abstract: This work explores an idea of modifying surface current distribution in a rectangular microstrip patch which contributes to reducing its H-plane cross-polarized (XP) radiations along with minimizing the backside radiation to some extent. A pair of grounded spikes has been strategically used and the physics behind its operation in weakening the XP generating TM02 mode has been thoroughly discussed. The vertical height of the spike is typically $\lambda $ /4 and a further investigation demonstrates shortening of its effective height by folding the same by 90°. A set of prototypes has been experimentally studied to ensure the predicted characteristics viz. the 12 dB consistent suppression of XP level over the whole range of elevation in H-plane and an average of 5–7 dB suppression in backside radiation. These achievements are also associated with more than 1 dB improvement in peak gain. The design is straightforward, low cost, and commercially viable. The nonplanar feature restricts its use only to those applications where antenna front is open or can accommodate the vertically extended or 90° bent spikes.
5 citations
TL;DR: In this paper , the authors address a concern of aperture coupled microstrip patch which is commonly overlooked and propose a simple strategic approach to reform the same for a rectangular patch, which achieves an overall XP discrimination by nearly 27dB from the perspective of 3D radiation scenario.
Abstract: This work addresses a concern of aperture coupled microstrip patch which is commonly overlooked. Such feeding configuration is typically believed to be immune to high cross-polar (XP) radiations, which indeed is a paradox. It actually offers considerably low XP only across H-plane, but concerning high XP over its diagonal or skewed planes (azimuth $\approx 45^{\circ }$ -70°). An aperture feed, therefore, hardly reveals any advantageous feature in terms of the overall XP discrimination. Such a major shortcoming of aperture-fed microstrip, to the best of our knowledge, has been addressed and successfully resolved in this article for the first time. It explores a way of mitigating near field issues based on theoretical analysis and has proposed a simple strategic approach to reform the same for a rectangular patch. A representative design, theoretical justification, and experimental studies with an S-band prototype have been presented. XP suppression by 11dB has been experimentally achieved in the diagonal (D-) plane with no considerable changes in its H- or E-plane. That eventually attains an overall XP discrimination by nearly 27dB from the perspective of 3D radiation scenario. The proposed technique hardly affects the co-polar radiations or gain of its traditional design. Moreover, this is satisfactorily functioning for a $2\times 2$ sub-array with a remarkable co-to-cross isolation by about 34dB over the entire radiation planes.
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TL;DR: In this article , an asymmetric defected ground structure (DGS) under the patch, which perturbs the TM02 mode, was proposed to reduce the cross-polarization without increasing the back radiation.
Abstract: For cross-polarization (XP) reduction of microstrip antenna, it is proposed to use asymmetric defected ground structure (DGS) under the patch, which perturbs the TM02 mode. Unlike conventional DGS, the proposed DGS reduces the XP without increasing the back radiation. A method of higher order modes and surrounding electric fields is used to explain the DGS. The feasibility and superiority of the proposed scheme are further verified by constructing H-plane linear 4-element arrays. The XP reduction and decoupling are achieved simultaneously, as supported by simulation and measurement.
References
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TL;DR: In this article, a defected ground structure (DGS) pattern is proposed to reduce the cross-polarized (XP) radiation of a microstrip patch antenna, which is simple and easy to etch on a commercial microstrip substrate.
Abstract: A defected ground structure (DGS) is proposed to reduce the cross-polarized (XP) radiation of a microstrip patch antenna. The proposed DGS pattern is simple and easy to etch on a commercial microstrip substrate. This will only reduce the XP radiation field without affecting the dominant mode input impedance and co-polarized radiation patterns of a conventional antenna. The new concept has been examined and verified experimentally for a particular DGS pattern employing a circular patch as the radiator. Both simulation and experimental results are presented.
275 citations
"Mitigating Unwanted Mode in a Micro..." refers background in this paper
...Introduction of defected ground structure (DGS) underneath a patch [13]–[15] are relatively simpler....
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...However, all of them [13]–[17] require high precision engineering or a kind of internal perturbation based on multiparametric optimized design....
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TL;DR: In this article, two photonic bandgap (PBG) structures, namely, the defected ground structure (DGS) and the compact microstrip resonant cell (CMRC), are applied to the feed line of microstrip antennas.
Abstract: Microstrip antennas inherently have a high input impedance at resonant frequency. This may not be convenient for some applications. For active integrated antennas, moreover, the radiated power of microstrip antennas needs to be very low at harmonic frequencies. The main goals of this study are impedance matching and harmonic suppression of microstrip antennas. In order to meet these requirements, two one-dimensional (1-D) photonic bandgap (PBG) structures, namely, the defected ground structure (DGS) and the compact microstrip resonant cell (CMRC), are applied to the feed line of microstrip antennas. The characteristic impedance of the microstrip line is controlled by the additional effective inductance of the PBG structure. Without any matching circuits, microstrip antennas can be easily fed by a simple 50 /spl Omega/ microstrip line with a PBG structure at the operating frequency. Additionally, the second harmonic of the proposed antennas is properly suppressed compared to a conventional antenna. Measured results indicate that the two PBG structures are quite effective for harmonic suppression. Therefore, the proposed antennas are suitable for active integrated antennas.
126 citations
Additional excerpts
...Use of band-gap structures [7], [8], differential...
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TL;DR: In this article, the authors investigated the effect of defected ground structure (DGS) on cross-polarized (XP) electric fields and associated radiations and found that the arc-DGS appears to be highly efficient in terms of suppressing XP fields.
Abstract: Experiments with probe-fed circular patches using conventional and defected ground planes flashed some interesting features relating to cross-polarized (XP) electric fields and associated radiations before the present authors. Those led to a series of new investigations for understanding the nature of XP fields and to deal with them using defected ground structure (DGS) for improved XP performance. In the first phase of investigation, the XP radiations of a probe-fed circular patch with conventional ground plane have been critically studied as a function of the radial probe location. Remarkably significant effect is experimentally demonstrated. New information about orthogonal resonant fields and its importance in designing an antenna is provided. In the second phase of investigation, limitations of dot-shaped DGS in reducing XP level are experimentally studied. As its improved variants, two new DGS geometries such as annular ring and circular arcs have been explored. The arc-DGS appears to be highly efficient in terms of suppressing XP fields. Suppression by 10-12 dB has been experimentally demonstrated. Each design has been experimented in both C- and X-bands to earn confidence on the measured data.
114 citations
TL;DR: In this paper, a broadband probe-fed patch antenna with a W-shaped ground plane is presented, which is obtained by bending the conventional planar ground plane into an inverted V-shape, seen in the resonant direction of the patch antenna and then adding proper flanges at the two straight edges of the ground plane.
Abstract: A new design of a broadband probe-fed patch antenna with a W-shaped ground plane is presented. The W-shaped ground plane is obtained by bending the conventional planar ground plane into an inverted V-shape, seen in the resonant direction of the patch antenna and then adding proper flanges at the two straight edges of the bent ground plane. The proposed design is applicable to the patch antenna with a planar radiating patch with a thin air substrate. With the use of the proposed W-shaped ground plane, the required probe-pin length in the substrate remains small, although the effective substrate thickness is significantly increased, resulting in a much wider operating bandwidth. Also, by choosing proper dimensions of the W-shaped ground plane, the antenna gain for frequencies over the obtained wide bandwidth is enhanced, compared to the conventional patch antenna with a planar ground plane. In addition, the cross polarization is also reduced for the proposed design and the cross-polarization level (XPL) in the H-plane pattern can even be better than that of a conventional probe-fed patch antenna with a thin air substrate.
89 citations
"Mitigating Unwanted Mode in a Micro..." refers methods in this paper
...Like earlier techniques by addressing the orthogonal mode [5]–[15], the present method also becomes effective over...
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...Several techniques were explored to reduce this H-plane XP radiation [5]–[17] of which [5], [6], and [10] used engineered bulky structure occupying 0....
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TL;DR: In this paper, a novel compact EBG structure in a spiral shape is presented and investigated, where the EBG cell introduces spiral structure to enlarge the capacitance between neighboring elements much, and get an extremely compact size.
Abstract: In this paper a novel compact electromagnetic band-gap (EBG) structure in a spiral shape is presented and investigated This EBG cell introduces spiral structure to enlarge the capacitance between neighboring elements much, and get an extremely compact size The simulations and experimental results have proved that the length of the spiral structure is only 309% of the conventional mushroom-like EBG structure The structure also presents some merits to design multi-band EBG structure only by adjusting the length of capacitance and without changing the periodical size Two applications are demonstrated, including radiation pattern improvement of patch antenna with novel EBG structure and steerable array with a linearly discrete beamsteering of 20° in steps of 10° at 30 GHz
87 citations
Additional excerpts
...Use of band-gap structures [7], [8], differential...
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