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This paper presents the novel design and analysis of a 25 W broadband Class-AB GaN HEMT-based power amplifier working over 0.9–1.7 GHz. A large signal model of the Wolfspeed-make GaN HEMT CG2H40025 has been used in this design. The comprehensive design process has been carried out with the help of the Advanced Design System software by Keysight. Instead of conjugately matching the load and source impedance obtained from load-pull analysis of a nonlinear model of CG2H40025, the value of load and source impedance has been tuned with the help of a novel design approach of an ideal matching design approach. Thus, to achieve an output power of more than 25 W and a flat large signal gain of 15.425 ± 0.375 dB, a novel design approach has been employed to create input and output matching networks, maintaining a lower Q value results in broad bandwidth and for determining the load and source impedances. The circuit has been fabricated on Roger's substrate RO4350B having a dielectric constant of 3.66 and a loss tangent of 0.0031. The unique design approach based on electromagnetic simulation of the circuit at each design step yielded experimental results that agreed very well with the simulated results. The fabricated power amplifier achieves a power-added efficiency of over 54.78% and a drain efficiency of over 55.45% throughout the entire frequency range. It also delivers a maximum output power of 32.18 W at 1.3 GHz. This power amplifier is developed for L-band Foliage Penetrating Radar. [ABSTRACT FROM AUTHOR]

This paper analyses the effect of introducing multi-cavity-backing up to four cavities on a two-layered suspended stacked one bottom four top rectangular microstrip antenna. The analysis brings out the concurrent enhancement of bandwidth, gain and isolation between two antennas with progressive cavity-backing up to three cavities. Compared to stacked rectangular microstrip antennas without cavity, the single and triple cavity-backed configurations yielded a 40% and 83% enhancement in bandwidth and 0.80 and 2.20 dB enhancement in gain, respectively. The proposed novel triple cavity-backed one bottom four top rectangular microstrip antenna yields a bandwidth of 65.2% and an average gain of 12.85 dBi with an efficiency of 89%. The triple cavity-backed configuration yielded cross-polarization of less than −50 dB in both E and H planes and two such proposed antennas with rim-to-rim separation of 0.35 λ0 give uniform isolation better than 40 dB covering the entire bandwidth. Measured results are in close agreement with the simulated one, which validates the performance of the antenna. The proposed antenna is deemed suitable for Through the Wall and Ground Penetrating Radar applications because of the improved characteristics offered by the proposed antenna in the S-band. [ABSTRACT FROM AUTHOR]

In this paper, a new planar printed quasi-Yagi antenna with compact size and wide bandwidth is presented for a multiple-input-multiple-output (MIMO) antenna system. Antenna element consists of a rectangular driven monopole, a strip director, and a coplanar ground shorted reflector. A planar rectangular monopole is used for the first time as a driven element instead of a dipole to avoid the implementation complexity of BALUN as it can be fed directly by an unbalanced coaxial feed. It has been shown that the antenna element has an impedance bandwidth (|S11| < −10 dB) of 60.5% ranging from 1.59 to 2.97 GHz. Based on this element, a four-element pattern diversity MIMO antenna is proposed. By utilizing the ground of one element as a reflector for the successive element, a compact size of 109 mm × 109 mm (0.54λ0 × 0.54λ0 at 1.5 GHz) has been obtained. Measured bandwidth of 65.9% (1.5–2.97 GHz) with minimum isolation of 13 dB has been achieved. The measured directional patterns and an average gain of 4 dBi, remain stable in the operating band with cross-polarization levels less than −25 dB. The envelope correlation coefficient and channel capacity loss show good diversity performance. [ABSTRACT FROM AUTHOR]

Modified design of triangular-shaped microstrip antenna is proposed for circular polarized response which yields an axial ratio bandwidth of 68 MHz (∼5%) in the L-band. Furthermore, its electromagnetically coupled stacked design is presented, which yields enhanced impedance and axial ratio bandwidth of more than 1100 (∼70%) and 90 MHz (>7%), respectively. A single and stacked antenna offers a broadside pattern with a peak gain of 9 dBi. As a part of the design procedure, resonant length formulation at patch modes is presented. This serves as a guideline in the re-designing of similar antenna in a given frequency spectrum. Theoretical results have been verified experimentally with a good agreement. [ABSTRACT FROM AUTHOR]

A technique of loading shorting posts on the patch has been used to enhance the directivity of a circular microstrip antenna (CMSA) in this paper. The shorting posts connected between the patch and the ground plane, force the electric field to become zero at that point, thereby modifying various modes of the circular patch. The shorting posts, also perturb the surface current distribution on the patch that help to increase its electrical size, which – in turn – enhances directivity at fixed resonance frequency. Investigations on various radii and positions of the shorting posts – to enhance the directivity of a CMSA, have been carried out. A systematic analysis on the performance of the CMSA at a lower order mode, fundamental mode and higher order mode frequencies with the loading of shorting posts has also been presented. The simulated and measured results show that the directivity of CMSA can be enhanced by up to 2 dB using the proposed technique without changing the patch geometry. In addition, the proposed antenna configuration yields, a bandwidth enhancement of almost three times as compared to that of a conventional CMSA. The simulated results of the conventional and shorted CMSA are experimentally validated with good agreement. [ABSTRACT FROM AUTHOR]

A design technique of an antenna array with amplitude distribution/tapering to suppress the first side lobe level by exploiting the property of the rectangular microstrip antenna (RMSA) is proposed. Non-identical antenna array elements have been designed using the RMSAs by varying their width and hence the gain (keeping the length and hence the frequency same) to obtain the amplitude distribution for a desired first side lobe level. This eliminates the need of a complicated feed network with unequal power division to realize amplitude tapering. The conceptualized design is verified for a number of corporate-fed arrays and an analysis is carried out to give design guidelines with respect to the number of elements in the array. A symmetric corporate-fed 8-element antenna array with a cosine-square over pedestal amplitude distribution, operating at 1.8 GHz, has been designed and fabricated to validate the proposed concept. There is a reasonable agreement between simulated and measured results. [ABSTRACT FROM AUTHOR]

Microstrip Reflectarrays (MRAs) are typically excited using the horn antenna. In this paper, a different microstrip antenna feed to excite MRA, which is having patches of variable size, is proposed. Three different configurations namely, 2 × 2, five elements arranged in two orthogonal axes, and 3 × 3 element MRAs have been investigated to prove the concept. These configurations were first simulated using IE3D software, followed by their experimental verifications. [ABSTRACT FROM AUTHOR]

The broadband and dual-band rectangular microstrip antenna is realized by cutting pair of toothbrush-shaped or step slots along the non-radiating edges of the patch. The toothbrush-shaped slot is said to introduce TMd0 mode in between the TM10 and TM20 modes of the rectangular patch and realizes broadband response. In step slot cut configuration, the slot introduces a mode near the TM10 mode resonance frequency of the patch and realizes dual frequencies. In this paper, a detail analysis to study the effect of slots on the broadband and dual-band response in these rectangular microstrip antennas (RMSAs) is presented. It was observed that the slot does not introduce any mode but modifies the resonance frequency of higher order orthogonal mode and realizes broadband and dual-band response. The slot alters the direction of surface currents at higher order mode and gives similar radiation pattern characteristics over the broader bandwidth and at the dual frequencies. In broadband RMSA, a formulation of resonant length at modified TM02 mode is proposed. The frequency calculated using the same closely agrees with the simulated result. [ABSTRACT FROM AUTHOR]

The dual-band microstrip antennas (MSAs) are realized by placing the stub on the edges of the patch or by cutting a slot at an appropriate position inside the patch. The multiband MSAs are realized by using the combination of the slot and stub. In this paper, by cutting a rectangular slot on the radiating edge and half U-slot on the nonradiating edge of a rectangular MSA, a dual- and triple-band rectangular MSA are proposed. These slots are of nearly quarter wave in length and by changing their lengths, tuning of the frequencies is realized. Also, the multiport network models for these multiband MSAs are proposed, which helps in understanding the mode distributions at slot and patch frequencies. To realize the higher gain, the suspended configurations of these multiband antennas are also proposed. A good agreement is obtained between the simulated, multiport network model, and measured results. [ABSTRACT FROM AUTHOR]