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A focused beam and a shaped beam four-layer transmitarray (TA) antenna operating in the $K$ -band have been designed, fabricated, and measured. Four-layer unit cells allowing a transmission phase range of 360° are used. The gain of the beam-focusing TA is 30.3 dB at 19 GHz with an aperture efficiency of 34.9%. Compared with TAs proposed in the literature, the presented antenna bandwidth is almost two times larger with a −1 dB gain bandwidth of 18% and a −3 dB gain bandwidth of 25.5%. A second TA radiating a shaped beam was designed, and its measured pattern correlates well with theoretical calculations. The sensitivity of the proposed unit cells to fabrication errors and the effect of oblique incidence are also studied. [ABSTRACT FROM PUBLISHER]

This paper presents the design of a meander-line circular polarizer optimized for oblique incidence and for a direction off from the principal planes (\phi=\text0^\circ, \text90^\circ, \text180^\circ, or \text270^\circ). This polarizing screen converts linearly polarized (LP) waves into circularly polarized (CP) waves and vice versa. To illustrate the design process, a three-layer meander-line circular polarizer is designed for an oblique incidence angle of (\theta=\text40^\circ, \phi=\text45^\circ) and its performance is examined in detail over the 18–20 GHz band. Measurements and simulations are in good agreement. Moreover, the sensitivity of the results to frequency and incidence angle variations is studied. The results show that the bandwidth of the meander-line circular polarizer is maximum when it is designed for normal incidence or for an oblique incidence in the two principal planes because coupling between orthogonal modes is weaker. [ABSTRACT FROM PUBLISHER]

Circular polarization selective surfaces (CPSS) based on two variants of the original Pierrot cell are proposed. For the first variant, which uses a load in the middle segment, it is possible to equalize the frequencies at which the reflection and transmission performance for the two orthogonal circular polarizations is optimal. The second variant is a double Pierrot cell having a twofold rotation symmetry, which leads to an increased bandwidth and less sensitivity to variations in the angle of incidence. Experimental results in good agreement with full wave simulations are presented. The printed circuit board (PCB) fabrication process used with flexible substrates allows more freedom for adjusting the cells in order to improve the performance and the bandwidth of the CPSS. [ABSTRACT FROM PUBLISHER]

A generalized methodology to design low-profile transmitarray (TA) antennas made of several stacked layers with nonresonant printed phasing elements is presented. A study of the unit cell bandwidth, phase-shift range and tolerances has been conducted considering different numbers of layers. A structure with three metalized layers with capacitive and inductive elements enabling a phase range of nearly 360° and low insertion loss is introduced. A study of the four-layer structure shows improvement in the performance of the unit cells in terms of bandwidth from 2% to more than 20% and a complete phase coverage. Implementations on a flexible substrate of TAs with progressive phase shift operating at 19 GHz are used for validation. [ABSTRACT FROM PUBLISHER]

This paper proposes a circular polarization selective surface (CPSS) design consisting of two meander-line circular polarizers and a linear polarizer. No vias are required. These polarizers are individually designed with ANSYS-HFSS (High Frequency Structure Simulator) software whereas the response of the overall cascade CPSS is computed with the GSM approach. A cascade CPSS which includes three-layer meander-line polarizers is designed and fabricated. Good agreement is shown between experimental and simulated results, with only the TE00 and TM00 modes in the GSM analysis. Finally, analysis of the circular polarizers based on simple filter theory is done to better understand how the performance of the whole structure can be improved. [ABSTRACT FROM PUBLISHER]

In this paper, a new compact monopole surrounded by four switched parasitic elements having the ability to work in the directional (beam steering) and omnidirectional modes is presented. The antenna is designed to operate over a 6% bandwidth in the both modes. In the directional mode, the beam is steered in the azimuth plane and a front-to-back ratio greater than 10 dB is achieved over the bandwidth of interest. To steer the beam, the parasitic elements surrounding the driven element are connected and disconnected to the ground plane through switches. The performance of the antenna with both ideal and non-ideal switches is discussed based on the simulation and measurement results. To overcome the adverse effect of the non-ideal switch on the antenna radiation pattern and transmission coefficient, a transformer network is used in the switch circuit. It is shown that the accurate design of this transformer network can reduce the adverse effects significantly. [ABSTRACT FROM PUBLISHER]

In this communication, a new broadband antenna with a very low profile is proposed. The antenna inherits the wide bandwidth of the blade antenna, while its height is considerably reduced to 0.03\lambda0, where \lambda0 is the wavelength of the lowest operating frequency. This new design consists of a top loaded monopole with several shorting pins and an inductive loading. The antenna resonates at two distinctive frequencies determined by the shorting pins and inductive loading and the wideband characteristic is achieved by the control of the resonance separations. The inductive loading is created by a shorted metallic disk embedded into the antenna structure. This new method of inductive loading facilitates the antenna fabrication while the physical size of the antenna is kept compact. A prototype was fabricated and its VSWR and far field radiation pattern were measured. The antenna provides a bandwidth of 17% for VSWR smaller than 3. Also, a minimum realized gain of 1 dBi was achieved over the frequency bandwidth in which the antenna is well matched. [ABSTRACT FROM PUBLISHER]