Abhishek Kandwal

Wideband DGS Circular Ring Microstrip Antenna Design Using Fuzzy Approach with Suppressed Cross-Polar Radiations

This paper presents a novel design of a circular ring defected ground structure (DGS) antenna for bandwidth enhancement using fuzzy logic approach. The ground plane of the antenna is defected by introducing circular ring sector type of defect beneath the circular ring patch. The position of the defect in the ground plane to attain the highest return loss and corresponding frequency is determined by using Fuzzy Inference System (FIS). The antenna resonates in X-band showing wideband characteristics with improved gain and reduced cross polar components. The return loss and analogous frequency obtained from simulated results and fuzzy system are compared and are in good agreement. The return loss and input impedance is measured experimentally and compared with the simulated results. Parameters like impedance bandwidth, VSWR and antenna gain are likewise calculated and discussed. The simulated results for the radiation pattern of the proposed design with polarization (Co-polar and Cross- polar) are also presented. The simulated impedance bandwidth of about 1.33GHz (1.2GHz experimentally) in X-band is obtained with a gain of 6.43dB and also cross-polarized radiations have an isolation of 20dB.

A Novel Design of Gap-Coupled Sectoral Patch Antenna

Using gap coupling between the elements, an antenna of four sectors by cutting the slots through and through from a circular patch is designed for application in X-band. The bandwidth enhancement along with reduced sidelobes is obtained by marginally or fully moving one of the feeding sectoral patches diagonally away. The results are analyzed for different positions of the slot. A bandwidth of 1.2 GHz in X-band along with a reduced sidelobe level of -15.0 dB and a gain of 12.0 dBi is obtained. An analysis of mutual coupling and parasitic patch effect is also presented and discussed in this letter.

Improved characteristics of DGS ring antenna in L-band

A compact design of defected ground antenna working in L-band is proposed in this communication. The antenna resonates in the frequency range between 1–2 GHz. The parameters such as return loss, input impedance, antenna gain and side lobe level are thus presented and discussed. A comparison is also shown for the proposed antenna with the antenna structure without defect. A very good return loss of −32 dB with a gain of 6.6 dBi is obtained for the defected ground structure (DGS) ring antenna.

Continuous Beam Steering Through Broadside Using Asymmetrically Modulated Goubau Line Leaky-Wave Antennas

Goubau line is a single-conductor transmission line, featuring easy integration and low-loss transmission properties. Here, we propose a periodic leaky-wave antenna (LWA) based on planar Goubau transmission line on a thin dielectric substrate. The leaky-wave radiations are generated by introducing periodic modulations along the Goubau line. In this way, the surface wave, which is slow-wave mode supported by the Goubau line, achieves an additional momentum and hence enters the fast-wave region for radiations. By employing the periodic modulations, the proposed Goubau line LWAs are able to continuously steer the main beam from backward to forward within the operational frequency range. However, the LWAs usually suffer from a low radiation efficiency at the broadside direction. To overcome this drawback, we explore both transversally and longitudinally asymmetrical modulations to the Goubau line. Theoretical analysis, numerical simulations and experimental results are given in comparison with the symmetrical LWAs. It is demonstrated that the asymmetrical modulations significantly improve the radiation efficiency of LWAs at the broadside. Furthermore, the measurement results agree well with the numerical ones, which experimentally validates the proposed LWA structures. These novel Goubau line LWAs, experimentally demonstrated and validated at microwave frequencies, show also great potential for millimeter-wave and terahertz systems.

A new, compact, efficient, parasitically coupled notch-loaded antenna

This paper presents a new, compact, efficient, wideband and low side-level parasitically coupled notch-loaded antenna array for communication systems. The antenna structure consists of a circular microstrip antenna coupled parasitically with notch-loaded rings. The proposed antenna is also considered using different dielectric substrates and the results are compared. The simulated results are compared with the experimental results and are found to be in good agreement with each other.

Open-ended voltage multipliers for wireless transmission of electric power

ABSTRACT This paper presents a class of open-ended voltage multipliers, of which the input is a displacement current from a Goubau line and the output is a multiplied DC voltage. When terminated with a 500 ohm load, the proposed voltage multipliers have rectified a microwave power at 20 dBm into a DC voltage 5–6 V, corresponding to a conversion efficiency of approximately 50%. The maximum voltage reaches 20 V if the circuit is unloaded. Due to its characteristic impedance being comparable to that of the free space, the Goubau line feeding the proposed voltage multipliers has been successfully used as a monopole antenna for capturing ground waves in an experimental system for wireless power transfer. Over a short range, with r ≪ 1.05 m, the open-ended voltage multipliers vertically mounted on the surface of a lossy dielectric material were at best able to generate a power proportional to 1/r0.4, where r is the distance between the receiver and the transmitter, suggesting that the received power is not a pure space wave.

Capacitor-Loaded Spoof Surface Plasmon for Flexible Dispersion Control and High-Selectivity Filtering

This letter proposes a new spoof surface plasmon transmission line (SSP-TL) using capacitor loading technique. This new SSP-TL features flexible and reconfigurable dispersion control and highly selective filtering performance without resorting to configuration change. Moreover, it requires much smaller linewidth than the conventional SSP-TL for achieving an extremely slow wave (or a highly confined field), which is quite useful for a compact system. To illustrate the design principle, several examples are designed within the frequency range of 2–8 GHz. Both numerical and experimental results are given in comparison with the conventional SSP-TL. It is demonstrated that the proposed technique provides a better performance in size reduction and dispersion reconfigurability.

Zigzag microstrip leaky-wave antenna mimicking wave propagation in metallic waveguides

This paper proposes a zigzag microstrip leaky-wave antenna mimicking the zigzaging wave propagation in hollow metallic waveguides. It is shown that a zigzaging line shape increases the phase velocity of the second space harmonic of the quasi-TEM mode and hence allows this mode to leaky-wave radiation. Moreover, coupling this mode to the higher leaky-wave mode leads to dual beam scanning. A design example is provided to illustrate the principle. Both backward and forward beam scanning radiation is observed from the simulated radiation patterns.

Design of nonreciprocal antenna array

A new non-reciprocal antenna array has been proposed in this paper for operation in microwave frequencies. The antenna array has been configured using a gyrator with the antenna patch elements through a T-type structure. Implementation of gyrator in the structure, that provides a phase shift of 180 degrees, results in a same beam direction of the forward and backward signals in the proposed antenna array. This proposed novel structure provides high radiation efficiency with beam steering and reduced side lobe levels.

Synthesis of lossy coupling matrix for negative group delay filters

A novel systematic synthesis method for negative group delay(NGD)structure is proposed in this paper. Transfer functions are obtain from synthesised characteristics polynomials which provides higher design flexibility. An optimum design condition is derived to reduce the number of resonators being equal to the highest degree of polynomial. Different synthesis examples are discussed with different orders and NGD responses. The exact agreement between the polynomial and coupling matrix based responses illustrate the proposed synthesis method.