Rafael A. Rodriguez-Solis

Dual-polarized X-band microstrip patch sub-array for Off-the-Grid radar array antenna

The design of a dual-polarized microstrip patch sub-array to be used as the radiating element in an array for the CASA Off-the-Grid radar system is presented. The sub-array consists of four microstrip patches with dual feeds and oppositely fed to reduce the cross-polarization levels. Simulation results in demonstrate a 7% bandwidth at 9.4 GHz, port isolation of 30 dB, and cross-polarization levels of 27 dB at broadside.

Analysis of a CPW Fed Annular Slot Ring Antenna using DOE

A statistical characterization of an annular slot ring antenna using design of experiments (DOE) was presented. It was shown that increasing the separation between circles and decreasing the inner radius lower the impedance. Adjusting the antenna dimensions in this way also increases the resonant frequency and lowers the gain of the antenna at broadside. It was shown that the impedance of slot rings and folded slots can be decreased by increasing the slot width at the side opposite to the feed line. Future work will include a higher order model to increase the accuracy of the results and a tunable version using thin ferroelectric films

Frequency-agile microwave components using ferroelectric materials

The non-linear electric field dependence of ferroelectric thin films can be used to design frequency and phase agile components. Tunable components have traditionally been developed using mechanically tuned resonant structures, ferrite components, or semiconductor-based voltage controlled electronics, but they are limited by their frequency performance, high cost, hgih losses, and integration into larger systems. In contrast, the ferroelectric-based tunable microwave component can easily be integrated into conventional microstrip circuits and attributes such as small size, light weight, and low-loss make these components attractive for broadband and multi-frequency applications. Components that are essential elements in the design of a microwave sensor can be fabricated with ferroelectric materials to achieve tunability over a broad frequency range. It has been reported that with a thin ferroelectric film placed between the top conductor layer and the dielectric material of a microstrip structure, and the proper DC bias scheme, tunable components above the Ku band can be fabricated. Components such as phase shifters, coupled line filters, and Lange couplers have been reported in the literature using this technique. In this wokr, simulated results from a full wave electromagnetic simulator are obtained to show the tunability of a matching netowrk typically used in the design of microwave amplifiers and antennas. In addition, simulated results of a multilayer Lange coupler, and a patch antenna are also presented. The results show that typical microstrip structures can be easily modified to provide frequency agile capabilities.

Cavity-backed folded-slot antenna

Folded slot antennas (FSAs) offer some of the attractive characteristics of the slot antennas, such as small size, light weight, wider bandwidth and that can be flush-mounted on surfaces. They also present an input impedance about four times lower than the slot antenna at the first useful resonance (f0) [1], facilitating the matching to 50 Ω and providing a wider bandwidth. However, FSAs, as well as slot antennas, are free to radiate from both sides of the substrate. This limits their applications in multilayer circuits, near metallic objects and near the earth. Placing a cavity behind the slot focuses the antenna radiation on one side of the substrate, suppressing backward radiation. This configuration is known as cavity backed slot antenna (CBSA). Many studies have been carried out about CBSAs. One of the earliest works was presented by [2], who used the Greens function technique to find the input admittance of the CBSA. Experimental works about input impedance of the CBSA have been proposed by [3], [4] and [5], in which was found that the input impedance of the antenna can be reduced as the cavity depth decreases. Although there are many works related with CBSAs, studies about CBFSAs have not been reported and there is no information about input impedance and radiation characteristics, to the knowledge of the authors. Since FSAs have lower input impedance than slots antennas, CBFSAs with shallow cavities could be of great interest in wireless devices, active and passive arrays, ground penetrating radars and airborne devices due to their compact size, flush-mounting capability, light weight and unidirectional pattern.

Dual polarized aperture-coupled microstrip patch antenna for X-band series-fed array

This paper discusses the design of a 4-port radiating element and a patch load radiating element (PL) that is used for a series feed linear array for CASAs student test-bed and the results obtained for their simulations.

Ways to improve the radiation pattern of a LPFSA

In this paper, we propose an alternative method for improvement the radiation properties of an LPFSA. Specifically, it is shown that the increased width of the side slots in the folded element amounts to the proper phasing conditions resulting in a stable pattern and a 2 dB average increase in peak gain. The impedance bandwidth is somewhat reduced, but over an octave broadband operation is attained. To fully assess the performance of the proposed structure, a thorough study and design of an LPFSA with and without the phasing slot is performed and all structures are compared. A design of experiments (DoE) technique with the method of moments code, Ansoft Designerreg, are utilized for the design and optimization

Design and Simulation of a Tunable Multilayer Lange Coupler

Full-wave electromagnetic simulators based in the method of moments (HP-EEsof Momentum) and in the finite difference time domain technique (Remcoms XFDTD) are ideal to analyze and study the effect of ferroelectric materials on the output response of microwave passive structures. The nonlinear electric field dependence of ferroelectric thin films has been used by the microwave research community to design tunable components. The fabrication of these structures is expensive and time consuming, hence, estimated results of the S-parameters using electromagnetic simulators are desirable previous to the fabrication process. In this work, BSTO ferroelectric thin film is used on MgO to simulate the output response of a K band multilayer Lange coupler. The S-parameters of the couplers are estimated for different bias conditions for the BSTO. Isolation, insertion loss, coupling, and return loss are computed for different bias conditions.

Analysis of a cavity backed annular slot ring antenna using design of experiment techniques

In this work, a cavity-backed annular slot-ring antenna is analyzed, and an initial characterization is performed using Design of Experiments. The initial design shows a bandwidth of 100 MHz at 7 GHz, with a gain of 3 dB. The DOE analysis yielded simple models that can serve as an initial guide for the design of this antenna.

Dual polarized microstrip antenna array for X-band radar applications

The design and development of an aperture-coupled dual-polarized patch antenna array operating at a frequency of 9.5 GHz for X-band radar application is presented in this paper. The linear array consists in connecting in series the 4-port radiating element in series. These antennas exhibit low profile as well as low cross polarization (XP) radiation and low sidelobe levels (SLL).

Characterization of a cavity-backed capacitively-fed folded slot antenna using DOE techniques

In this work a cavity-backed, capacitively-fed folded-slot antenna was characterized using Design of Experiments (DOE) techniques to study the influence of the antenna dimensions in the resonant frequency and in the reflection coefficient at resonance. The DOE technique used in the experiment was an un-replicated 2Kfull factorial. The experiment was conducted by simulations in the Ansofts HFSS, and the results obtained were statistically analyzed with the software Minitab. The results reflect with a 99% of reliability only the dimension that affects the responses. These results allow improving the antenna operation and size reduction.