Mukesh Kumar Khandelwal

Defected Ground Structure: Fundamentals, Analysis, and Applications in Modern Wireless Trends

Slots or defects integrated on the ground plane of microwave planar circuits are referred to as Defected Ground Structure. DGS is adopted as an emerging technique for improving the various parameters of microwave circuits, that is, narrow bandwidth, cross-polarization, low gain, and so forth. This paper presents an introduction and evolution of DGS and how DGS is different from former technologies: PBG and EBG. A basic concept behind the DGS technology and several theoretical techniques for analysing the Defected Ground Structure are discussed. Several applications of DGS in the field of filters, planar waveguides, amplifiers, and antennas are presented.

Triple band circularly polarized compact microstrip antenna with defected ground structure for wireless applications

Asymmetric slits loaded irregular shaped microstrip patch antenna with three different ground structures is proposed. All three antennas show triple band characteristics. First antenna with regular ground plane resonates at 1.95, 2.4, and 4.90 GHz with good radiation characteristics and shows right-hand circular polarization at 1.95 GHz. 18.75% of compactness is achieved with triple band characteristics. Further, same patch is used with different defected ground structures. Second antenna resonates at 1.85, 2.4, and 4.85 GHz with suppressed cross-polarization level and antenna shows right-hand circular polarization at 1.85 and 4.85 GHz. Compactness is further improved to the value of 22.91%. The third antenna resonates at 1.95, 2.4, and 4.85 GHz with better gain and radiation characteristics and antenna shows right-hand circular polarization at 1.95 and 2.4 GHz. The small frequency ratio f 2 /f 1 is achieved and the value of f 2 /f 1 is 1.29 and 1.23 for second and third configuration, respectively. Proposed structures show right-hand circularly polarized with suppressed left-hand circularly polarized radiations and suitable for fixed mobile wireless communication applications. All structures are analyzed using Ansoft HFSS v.14 based on finite element method and measured results satisfy the simulated results.

Dual-band stacked circularly polarized microstrip antenna for S and C band applications

A single-fed circularly polarized microstrip antenna is proposed where the antenna structure exhibits truncated corners in the radiating square patch. The truncated corners square patch structure is loaded with a circular slot and is resonating at 2.25 GHz with circular polarization. Furthermore, the proposed antenna is stacked using an upper circular patch thus achieving a dual-band circularly polarized pattern. The dual-band antenna resonates at 2.25 GHz in the first band and with impedance bandwidth ranging from 4.4 to 5.5 GHz in the second band. The size of the proposed stacked structure is compact compared with the conventional circularly polarized stacked antenna designs. Proposed structures are fabricated and fed using Subminiature version A (SMA) connector. The measured results are in good agreement with the simulated. The antenna shows stable radiation characteristics for the entire band of operation.

Single-feed circularly polarized stacked patch antenna with small-frequency ratio for dual-band wireless applications

A single-feed dual-band circularly polarized stacked microstrip patch antenna with a small-frequency ratio is presented. Two pair of orthogonal slits is cut on the lower circular patch for achieving circular polarization and truncated corner square patch is used as the upper parasitic element. The frequency ratio of the dual-band is 1.03. The 3 dB axial ratio bandwidth is 1.3% for the upper band and 1.1% for the lower band. Proposed structure is fabricated on the FR-4 epoxy substrate and fed by SMA connector. The measured results are in good agreement with the theoretical and simulated results. The antenna shows stable radiation characteristics in both bands of operation.

Truncated compact circular microstrip antenna loaded with asymmetric slits

A compact circular microstrip antenna is presented. The proposed radiating structure consists of a truncated circular patch loaded with asymmetric slits. A 32% compactness is achieved when compared with conventional circular microstrip antenna. The variation in resonant frequency with the slit dimensions is also investigated and observed that the antenna characteristics are highly dependent on slit dimensions. The resonant frequency can be altered by simply varying the slit dimensions. The proposed antenna may be a good candidate for indoor wireless local area network applications.

ANTENNA WITH HEXA-BAND CAPABILITIES FOR MULTIPLE WIRELESS APPLICATIONS

In this paper, a novel multiband microstrip patch antenna with small frequency ratio is designed and analysed. One can design a multiband antenna at any desired frequencies through these proposed methods. The proposed antenna shows six operating frequencies with very small frequency ratio between two consecutive resonant frequencies 1.1248, 1.1123, 1.0792, 1.1469 and 1.3254 and can be used for various wireless applications, i.e., 2.5 GHz for UMTS and Wi-Fi, 2.812 GHz for CCTV with wireless video links, 3.128 GHz and 3.376 GHz for WiMAX, 3.872 GHz for C-band applications and 5.132 GHz for Lower WLAN. Design procedure and formation of all six bands are presented and discussed. Analysis is done by Ansoft HFSS v. 15 which is based on Finite Element Method (FEM), and simulated results are verified with experimental results of fabricated prototypes which are found in close agreement.

THEORETICAL ANALYSIS AND DESIGN OF DUAL BAND DGS ANTENNA WITH SMALL FREQUENCY RATIO FOR WI-FI AND WIMAX APPLICATIONS

In this article, a theoretical analysis and design are presented for a Microstrip Patch Antenna (MPA) embedded with an inclined rectangular slot supported by a C-shaped Defected Ground Structure (DGS). Dual-band characteristics are achieved at 2.4 GHz and 2.6 GHz with a small frequency ratio of 1.08, which makes the proposed antenna useable for Wi-Fi and WiMAX applications. A theoretical analysis is also proposed for the designed antenna structure using modal expansion cavity model and equivalent circuit approach. The analyzed antenna design is fabricated, and it is found that measured results are in good match with theoretical and simulated results.

Omnidirectional multi-band stacked microstrip patch antenna with wide impedance bandwidth and suppressed cross-polarization

In this paper, triple-band stacked microstrip patch antennas (MPAs) are presented with wide impedance bandwidth and suppressed cross-polarization level. Triangular and circular shaped slots are embedded in the patch of antenna. Slot-loaded microstrip patches are fed with meandered microstrip line supported by a semi-ground plane structure. Triangular shaped slot-loaded MPA shows triple resonance at frequencies 2.2, 4.45, and 5.3 GHz having bandwidth of 45.9, 19.23, and 15.67%, respectively. Circular shaped slot-loaded MPA also shows triple resonance at frequencies 2.2, 4.42, and 5.38 GHz having bandwidth of 50.24, 33.21, and 13.43%, respectively. Using circular slot in place of triangular; bandwidth of the first and the second band is improved by 4.34 and 13.98%, respectively. Both the proposed antennas show an omnidirectional radiation pattern at all three resonance frequencies in the xz-plane with almost 0 dBi gain. Both the proposed antennas are fabricated on a FR-4 epoxy substrate and show a minimum level of cross-polarization radiations.

Design and analysis of microstrip DGS patch antenna with enhanced bandwidth for Ku Band applications

A wide band Microstrip antenna with defected ground plane structure is proposed for Ku Band applications. The design procedure is presented and characteristics of the antenna are analyzed. A 50-ohm Microstrip line is used to excite the circular slot integrated in ground plane. The measured results demonstrate that the structure exhibits a wide impedance bandwidth of 56.67% ranging from 9.8 GHz to 17.55 GHz, which covers Ku-band and partially X-band. Within the band, stable radiation characteristics are observed. The designed antenna has a gain ranging from 5dBi to 12.1dBi in impedance bandwidth range. Isolation of about 20dB is observed between the co-polar and cross-polarization level.