Debatosh Guha

Microstrip Patch Antenna With Defected Ground Structure for Cross Polarization Suppression

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.

Resonant frequency of circular microstrip antennas with and without air gaps

An improved analytical model is presented for calculating the resonant frequency of circular microstrip antennas with and without air gaps. Unlike the previous models, the present one is widely applicable to all patch diameters-from very large to very small compared to the height of the dielectric medium below the patch and also to the substrates covering the entire range of dielectric constants. The computed results for different antenna dimensions and modes of resonance are compared with the experimental values.

Improved Design Guidelines for the Ultra Wideband Monopole-Dielectric Resonator Antenna

This letter examines in detail multiple resonance phenomenon responsible for the ultra wideband response of the hybrid monopole-dielectric resonator antenna (DRA). The physical insight gained by this investigation has lead to improved guidelines for designing the antennas for any specified frequency band. These simple guidelines are then verified using both simulated and measured data

Four-Element Cylindrical Dielectric Resonator Antenna for Wideband Monopole-Like Radiation

A new four-element cylindrical dielectric resonator (CDR) array is proposed as a wideband low profile monopole-like antenna. Unlike previous investigations, the present antenna is easy to design and excite as it employs the dominant HEM11delta mode in each CDR. Ansofts HFSS based design data and experimental results are presented. As much as 29% matching bandwidth (S11<-10 dB) with monopole-like radiation pattern over the entire band has been achieved with 4 dBi peak gain from a prototype occupying a very compact space measuring 0.6lambda0 by 0.1 lambda0 approximately

Concentric Ring-Shaped Defected Ground Structures for Microstrip Applications

A new defected ground structure (DGS) consisting of concentric circular rings in different configurations is experimentally studied to examine the stopband characteristics. Unlike previous DGS designs, a metallic shielding is introduced at the back of the DGS to suppress any leakage or radiation, and this would be advantageous for microwave circuit applications. A wide stopband is demonstrated with a set of prototypes designed for X-band. Its application to suppressing mutual coupling in microstrip patch arrays is demonstrated

New Half-Hemispherical Dielectric Resonator Antenna for Broadband Monopole-Type Radiation

A new half-hemispherical dielectric resonator antenna (h-HDRA) is proposed and a two-element h-HDRA configuration is employed to design a broadband monopole-type radiator. Two half sections of a hemispherical DRA are employed to enhance the impedance bandwidth by introducing an additional resonant mode. Since the new geometry of an h-HDRA is studied here for the first time, it is characterized using simulation and experimental studies. Two closely spaced resonant modes, which in a two-element h-HDRA generate monopole-type radiation are investigated. Results for both the single and two-element h-HDRAs are presented. As much as 35% impedance bandwidth (S11<-10dB) with more than 5 dBi peak gain, 99.08% efficiency and monopole-type radiation pattern has been demonstrated using a prototype occupying a compact volume measuring 0.48lambda0 by 0.2lambda0 approximately, lambda0 being the wave length corresponding to the center of the impedance bandwidth

Resonant frequency of circular microstrip antenna covered with dielectric superstrate

A simple design formulation to compute accurate resonant frequencies of circular microstrip antennas covered with dielectric superstrates is proposed. It alleviates the rigorous mathematical analyzes and large computational time of some earlier works. This theory is widely applicable to both high and low dielectric constant superstrates as verified with the experiments and other theoretical models. Of all theories, the present one shows the closest approximation with the measurements revealing average percent error as low as 0.52%. The extension of this formulation to predict the accurate design data for conventional microstrip circular antennas are also verified with different experiments and available improved theories for various sets of antenna parameters.

Higher Order Mode Excitation for High-Gain Broadside Radiation From Cylindrical Dielectric Resonator Antennas

A resonant mode (HEM12δ), other than those ( HEM11δ and TM01δ) conventionally excited and used in a cylindrical dielectric resonator antenna (CDRA) has been examined with a view for using it as another radiating mode with broadside radiation patterns. Excitation of the mode, being the most challenging aspect, has been discussed and resolved by employing an innovative technique. The proposed concept has been successfully verified and experimentally demonstrated for the first time. More than 8-dBi peak gain with excellent broadside radiation has been obtained from a prototype shaped from a commercially available low-loss dielectric material with relative permittivity 10.

Resonant frequency of equilateral triangular microstrip antenna with and without air gap

A tunable equilateral triangular microstrip patch (ETMP) antenna with a variable air gap between the substrate and the ground plane has been studied theoretically and experimentally. Calculated resonant frequencies for different air gap heights have been verified with measurements of a coax-fed antenna. The tunability of the antenna as a function of the air gap height is studied theoretically showing over 200% tunable range of an ETMP with 50 mm side length printed on a substrate with /spl epsiv//sub r/=10.5. The computed results for the antennas with zero air gap height are compared with a standard spectral domain moment method analysis supported by other previously reported experiments. Very close agreement is revealed in all comparisons.

Improved Cross-Polarization Characteristics of Circular Microstrip Antenna Employing Arc-Shaped Defected Ground Structure (DGS)

Application of defected ground structure (DGS) to suppress cross-polarized (XP) radiation from a microstrip patch antenna has been reinvestigated using a new DGS geometry for much improved characteristics. Arc-shaped defect has been used in pair, symmetrically located under a circular patch. A number of optimization parameters have been examined using simulated results, leading to a design indicating improved XP behavior. A set of identical prototypes, with and without DGS, have been experimentally studied. The presence of the DGS shows as much as 30 dB isolation of the XP level from its peak radiation, and that compared to an identical patch without DGS indicates an improvement by as much as 12 dB. The relative suppression in XP values are found to be around 7-12 dB over ±75° elevation around the boresight of the patch.