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Abstract A miniaturized V-band leaky-wave antenna (LWA) with circular polarization and backward-broadside-forward radiation based on a modified half-mode substrate integrated waveguide (M-HMSIW) is presented. The proposed M-HMSIW structure employs broadside coupled complementary split ring resonators to replace metallic vias, resulting in low-cost and fully-planar fabrication advantages over conventional HMSIWs. Each unit cell of the proposed LWA consists of an M-HMSIW in combination with two horizontal stubs and a cross-shaped complementary electric LC slot to provide a proper circular polarization with a composite right/left-handed property. Using this structure, the balanced condition can be obtained for the unit cell; hence a continuous backward-to-forward scanning, including broadside, is achieved. As a result, the proposed LWA with a radiator length of only 3.8 λ 0 provides wide-angle beam scanning from − 53° to + 54° over the frequency range of 61.2 GHz to 73.4 GHz, while maintaining an excellent circular polarization between − 25° and 25°. The maximum gain of the LWA is 11.1 dB which is satisfactory, considering its compactness. The antenna’s performance is experimentally verified, and close agreement between the simulations and measurements is observed.

In this paper, a mathematical model is proposed to govern the phase distribution on a reconfigurable intelligent surface (RIS) for anomalously reflecting the beam towards the directions of interest. To this end, two operational modes are defined with respect to the reflected pattern. In the first mode, the RIS is configured to form multi-reflected beams toward the directions of interest capable of being controlled independently. The second mode is when the RIS provides a wide reflected beam. Regarding to each mode, a cost function is derived and then, in order to enhance the reflected pattern characteristics, a genetic algorithm (GA) is employed to the model as optimization method. To validate the practicality of the method, the proposed model is applied to a fabricated RIS to assess its performance in a real-world outdoor scenario. In the first mode, an asymmetric dual-beam reflected pattern is obtained and tested with tilt angles of $\theta _{0}=60^{\circ }$ and $\theta _{1}=135^{\circ }$ . Furthermore, a wide-reflected beam is generated in the second mode with half-power beamwidth of $\theta _{HPBW}=30^{\circ }$ and tilt angle of $\theta _{0}=75^{\circ }$ . At both modes, the measured data are well aligned with the simulated results.

Abstract A hybrid technique is proposed to manipulate the field distribution in a substrate integrated waveguide (SIW) H-plane horn to enhance its radiation characteristics. The technique comprises two cascaded steps to govern the guided waves in the structure. The first step is to correct the phase of fields and form a quasi-uniform distribution in the flare section so that the gain increases and side-lobe-level (SLL) decreases. This is obtained by loading the structure with a novel modulated metal-via lens. Field expansion on the radiating aperture of the SIW H-plane horn generates backward surface waves on both broad walls which increases the backlobe. In the second step, these backward surface waves are recycled and directed forward with the aid of holography theory. This is achieved by adding a couple of dielectric slabs with holographic-based patterns of metallic strips on both broad walls. With this step, the backlobe is reduced and the endfire gain is further increased. Using the proposed technique, the structure is designed and fabricated to operate at $$f=30$$ f = 30 GHz which simultaneously improves the measured values of gain to 11.65 dBi, H-plane SLL to $$-\,17.94$$ - 17.94 dB, and front-to-back ratio to 17.02 dB.

Here, we first aim to explain practical considerations to design and implement a reconfigurable intelligent surface (RIS) in the sub-6 GHz band and then, to demonstrate its real-world performance. The wave manipulation procedure is explored with a discussion on relevant electromagnetic (EM) concepts and backgrounds. Based on that, the RIS is designed and fabricated to operate at the center frequency of 3.5 GHz. The surface is composed of 2430 unit cells where the engineered reflecting response is obtained by governing the microscopic characteristics of the conductive patches printed on each unit cell. To achieve this goal, the patches are not only geometrically customized to properly reflect the local waves, but also are equipped with specific varactor diodes to be able to reconfigure their response when it is required. An equivalent circuit model is presented to analytically evaluate the unit cell’s performance with a method to measure the unit cell’s characteristics from the macroscopic response of the RIS. The patches are printed on six standard-size substrates which then placed together to make a relatively big aperture with approximate planar dimensions of $120 \times 120$ cm2. The manufactured RIS possesses a control unit with a custom-built system that can control the response of the reflecting surface by regulating the performance of the varactor diode on each printed patch across the structure. Furthermore, with an introduction of our test-bed system, the functionality of the developed RIS in an indoor real-world scenario is assessed. Finally, we showcase the capability of the RIS in hand to reconfigure itself in order to anomalously reflect the incoming EM waves toward the direction of interest in which a receiver could be experiencing poor coverage.

Millimeter wave (mmWave) systems with effective beamforming capability play a key role in fulfilling the high data-rate demands of current and future wireless technologies. Hybrid analog-to-digital beamformers have been identified as a cost-effective and energy-efficient solution towards deploying such systems. Most of the existing hybrid beamforming architectures rely on a subconnected phase shifter network with a large number of antennas. Such approaches, however, cannot fully exploit the advantages of large arrays. On the other hand, the current fully-connected beamformers accommodate only a small number of antennas, which substantially limits their beamforming capabilities. In this article, we present a mmWave hybrid beamformer testbed with a fully-connected network of phase shifters and adjustable attenuators and a large number of antenna elements. To our knowledge, this is the first platform that connects two RF inputs from the baseband to a 16× 8 antenna array, and it operates at 26 GHz with a 2 GHz bandwidth. It provides a wide scanning range of 60°, and the flexibility to control both the phase and the amplitude of the signals between each of the RF chains and antennas. This beamforming platform can be used in both short and long-range communications with linear equivalent isotropically radiated power (EIRP) variation between 10 dBm and 60 dBm. In this article, we present the design, calibration procedures and evaluations of such a complex system as well as discussions on the critical factors to consider for their practical implementation.

A high-resolution conformal array for detection of small size tumors inside the breast is proposed. The array consists of a novel cavity-backed low-profile aperture-stacked-patch (LP-ASP) antennas. The proposed antenna operates from 2.2 GHz to 13.5 GHz which enables the imaging system to be exploited across a high fractional bandwidth of approximately 149%. Thanks to the wide operating bandwidth of the designed antenna, the proposed system is not only applicable for a deep penetration imaging, but also for high resolution and accurate images acquisition. The proposed single element antenna has a compact size of 10 × 10 × 10.495mm3. So, it is possible to form a conformal array around the breast by applying numbers of the designed elements. Moreover, a Hybrid Artifact Suppression (HAS) method is presented to remove the artifact effects including skin reflection and mutual coupling between the elements. In this method, the artifact response of each channel is estimated using Independent Component Analysis (ICA) at the early-stage of the recorded signals. Additionally, in order to suppress the artifact data to accurately detect the malignant tumor, a Wiener filter is applied. To validate the practicality of the presented calibration algorithm in the proposed conformal array, the detection of a single spherical tumor (with a small diameter of 5 mm) within a realistic breast model in different scenarios is studied. Investigating of simulated and measured results of the designed antenna, and comparing quantitative metrics of successfully reconstructed tumor images by the proposed HAS and conventional calibration methods show the proposed system can be a good candidate for the breast cancer detection applications.

To understand how rapid changes in blood pressure can regulate Na-K-ATPase in the kidney cortex, we tested the hypothesis that a short-term (5 min) decrease in renal perfusion pressure will increase the amount of Na-K-ATPase in the plasma membranes by an angiotensin II-dependent mechanism. The abdominal aorta of anesthetized Sprague-Dawley rats was constricted with a ligature between the renal arteries, and pressure was monitored on either side during acute constriction. Left renal perfusion pressure was reduced to 70 ± 1 mmHg (n = 6), whereas right renal perfusion pressure was 112 ± 4 mmHg. In control (nonconstricted) rats (n = 5), pressure to both kidneys was similar at 119 ± 6 mmHg. After 5 min of reduced perfusion, femoral venous samples were taken for plasma renin activity (PRA) and the kidneys excised. The cortex was dissected, minced, sieved, and biotinylated. Lower perfusion left kidneys showed a 41% increase (P < 0.003) in the amount of Na-K-ATPase in the plasma membrane compared with right kidneys. In controls, there was no difference in cell surface Na-K-ATPase between left and right kidneys (P = 0.47). PRA was 57% higher in experimental animals compared with controls. To test the role of angiotensin II in mediating the increase in Na-K-ATPase, we repeated the experiments (n = 6) in rats treated with ramiprilat. When angiotensin-converting enzyme was inhibited, the cell surface Na-K-ATPase of the two kidneys was equal (P =0.46). These results confirm our hypothesis: rapid changes in blood pressure regulate trafficking of Na-K-ATPase in the kidney cortex. [ABSTRACT FROM AUTHOR]