A popular method for creating required phase shifts for patches in a microstrip Reflectarray uses open ended stubs attached to the patches. Uniform stubs are narrowband and hence limit the bandwidth of the array. In this paper, two novel methods for designing broadband reactive phase shifters are proposed based on the method of least squares. A structure consisting of transmission line sections, open-ended stubs, and resistors is considered for the phase shifter. Another one consists of transmission lines and open-ended. A least square error function is constructed for the required phase shift and the characteristic impedances, electrical lengths of transmission lines and resistances are obtained by its minimization. Then, the circuit is realized by microstrip lines to be attached to the microstrip patch. It is shown that the novel phase shifters create the required phase shifts in a broader bandwidth than those of uniform stub phase shifters. The frequency response of proposed microstrip line phase shifters are validated by the results obtained using AWR's Microwave Office software.

A novel technique for acquiring high aperture efficiency in dual Reflectarray Antennas (DRA) is presented. This technique is performed by using a shaped beam sub-Reflectarray which gives optimum illumination on the main Reflectarray aperture. Applying this technique resolves the inherent deficiency of Reflectarrays; which is the impossibility of controlling elements amplitude. In this regard, it has been shown that using this feature, the aperture efficiency of a classic dual Reflectarray antenna can be enhanced significantly by optimally shaping the sub-Reflectarray radiation pattern. Theoretical analysis demonstrates an improvement of about 12% in antenna aperture efficiency comparing with a conventional dual Reflectarray antenna.

Phase Perturbation Method (PPM) is introduced as a new phase-only synthesis method to design Reflectarray Antennas so as their sidelobe level is reduced. In this method, only the reflected phase of conventional unit cells are perturbed from their required values. To this end, two approaches namely the conventional Optimization method and newly introduced Phase to Amplitude Approximation (PAA) method are proposed. Finally, a Reflectarray antenna is designed and fabricated to have a low sidelobe level and its performance is investigated.

This paper presents a new unit to design dual linearly polarized Reflectarray antenna at ku for satellite telecommunication. Two orthogonal sets of parallel dipoles are used for each polarization to achieve more degree of freedom in the design and wider phase variation in the unit cells, consequently. A 0. 3m Reflectarray Antenna with two distinct beams is fabricated and measured in an anechoic chamber. The measurements have been carried out for both polarizations (X and Y ) in the azimuth and elevation planes. This antenna has x-polarized beam at (θ 0=30º , ϕ 0=90º ) with 23. 7 dBi gain and y-polarized beam at (θ 0=30º , ϕ 0=0º ) with 24. 2 dBi gain at Ku-band. The proposed design has one layer and simple structure compared to the references as well as dual band and dual polarization capabilities.

We present a new phase realization approach applied to design the broadband single-layer Reflectarray Antennas. Such an optimization technique minimizes the adverse effects of frequency dispersion which limit the bandwidth of Reflectarray antenna designed by traditional methods. Using this new approach leads to obtaining a wideband Reflectarray by finding the optimum element arrangement on the antenna aperture. The excellence of such an approach in comparison with its counterparts is to decrease the dependency of wideband Reflectarray design to the element phase behavior. For really assessment this phase synthesis approach, a single-layer Reflectarray compromising of square patches loaded with split rings is designed with the help of this optimization technique. It is analytically and numerically shown that the simulated Reflectarray can be a broadband antenna in which Side Lobe Level (SLL) value is reduced. To validate the obtained numerical results, a designed 29×29cm2 Reflectarray is fabricated and measured. Measurements demonstrate 1. 5dB gain bandwidth of about 28% covering 12-16GHz frequency band. Its |SLL| is also less than-17dB (<-13. 5dB for uniform excitation arrays). Such a design technique is applicable for approximately all Reflectarray elements and relieves the designer from complex elements and multilayer structures.

In this paper, a high-gain low-cost Reflectarray antenna is proposed. This antenna does not need radome. The exploited dielectric is the FR4 epoxy which is both low-cost and mechanically robust. Reflector of the proposed antenna consists of a layer of FR4, suspended above the ground plane by spacer, with its re-radiating elements on its interior side. Superiority of the suggested antenna over the similar previously reported design is shown. For the proposed design, sensitivity of the phase-delay characteristic, number of elements and gain to the FR4 thickness is studied. In addition, effect of design tolerance for the dielectric and the air gap on the antenna gain is investigated.

In recent years Reflectarray Antennas have received considerable attention due to their unique capabilities. However, due to their large size, analyzing the performance of these Antennas using traditional full wave finite-difference and finite-element techniques requires considerable computational resources. In this paper, we present an efficient method to accurately analyze these class of Antennas which considerably reduces the computational burden. First, the radiation properties of the unit cells of the Antennas are obtained by applying periodic boundary conditions, which corresponds to an infinite array. Then, a phase-only algorithm is used to obtain required phase shift on the antenna surface. Next, different unit cells are used to achieve the required phase on the antenna surface. Lastly, to confirm the validity of our approach, each designed antenna is simulated by full wave method using method of moment and the full wave simulation results of co and cross polarization levels are compared with those obtained using the proposed formula. There is excellent agreement between the co- and cross polarization levels obtained by proposed approach and those obtained using full wave simulation.

This paper proposes a new method for the design of a broadband dual-beam Reflectarray antenna with a single feed. This method is based on the producing a null in the antenna radiation pattern and the appearance of two beams. The reflection phase distribution on the aperture of the antenna has been studied to achieve this null. A single layer subwavelength element with multi-resonances is used as the phase shifting unit cell due to its wide linear phase range. A comprehensive theoretical analysis and full-wave simulation are accomplished and the results are in good agreement. Two dual beam Reflectarray Antennas operating at X band are designed using the proposed method and the geometrical method. The improvement in the gain bandwidth and the beam squint of the designed Reflectarray using our proposed method is observed compared to the other one. The simulation results show the improvement of 1. 1% in 1-dB gain bandwidth and in the beam squint for the proposed design method compared with the other one.

A Reflectarray Antenna is designed to operate at X-band as a Local Multipoint Distribution Service (LMDS) base station antenna. It is a center-fed single layer Reflectarray consisting of 23×27 elements. The unit cell of the Reflectarray has linear polarization with more than 400° linear phase shift and its geometrical parameters have been optimized to achieve wide bandwidth and low cross polarization (XP) level for the Reflectarray. An iterative design procedure, that is valid for obtaining any arbitrary pattern, has been implemented to achieve the specified radiation pattern over a desired frequency range. The method has been successfully applied to a LMDS base station antenna, characterized by a sectorial cosecant squared beam in the frequency range of 9.3 GHz - 11.5 GHz. The simulation results are in a good agreement with the design requirements. The antenna has cosecant squared pattern over the bandwidth of 21%, XP level better than -30 dB, and SLL less than -20 dB in both elevation and azimuth planes. The total size of the 23×27-element array is 246×289 mm2 , and its 1dB gain bandwidth is wider than 19%. The proposed antenna performs significantly better than similar structures and has all the features and standards required for LMDS base station antenna

In this paper, a novel planar hybrid multiband antenna formed by a loop-type antenna, a monopole slot antenna, and a coupled planar monopole antenna for the mobile phone is proposed. The loop-type antenna comprises a driven monopole and a coupled strip that printed on the other side of the substrate and short-circuited to the ground. The 0.5l and 1.0l mode of the loop-type antenna are excited. Therefore, the 0.5l mode of the loop-type antenna forms a wide bandwidth of 326 MHz to cover the GSM850/900 operation and the 0.25l mode of the monopole slot antenna, the 1.0l mode of the loop-type antenna, and the 0.25l mode of the coupled monopole antenna provide a wide bandwidth of 1181 MHz to cover the GPS/DCS/PCS/UMTS/WLAN2.4/WiMAX operation. Finally, the 0.5l mode of the coupled monopole antenna forms a wide bandwidth to cover the WLAN5.2 operation. Moreover, the hybrid antenna occupies a compact area of 16.5´45 mm2 and it has good radiation characteristics over the operating bands.