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This paper presents a single-feed circularly polarized wideband printed antenna for small satellites, which can be used with NASA Near-Earth Networks (NEN) for both uplink and downlink communications. This electromagnetically coupled stacked antenna is capable of working with a duplex transceiver and has the advantage of not requiring two different antennas for transmitting and receiving. It shows a significantly wide axial ratio (AR) 11 < −10 dB bandwidth. This wideband covers the NASA NEN's X-band uplink and downlink frequencies. The overall antenna size for a single element is 17 mm × 17 mm × 6.5 mm, which can provide a peak gain of 8 dBi. This antenna can save up to at least 50% area required by the conventional two-antenna solution for uplink and downlink, which is critical for CubeSat applications.

High Impedance Surface (HIS) planar antenna governed by leaky wave properties is presented in this paper. Near the ‘magnetic resonance’, the slotted square shaped ring patches experience the peak current value. Thus, the slotted square shaped ring patch based metasurface antenna resonates at 29.7 GHz where the structure exhibits negative effective permittivity and effective permeability. Far-field performances are examined for a different number of elements distributed over the copper grounded substrate. Maximum gain of 9.142 dB near the resonance is obtained with good gain-bandwidth over a large frequency from this antenna composed of 6 elements.

An ultrathin antenna of thickness nearly 100th of the wavelength is presented, which is capable of providing small-scale beam steering. The antenna is inspired by concepts used in high impedance surfaces (HISs) A linear array antenna comprised of periodic dogbone-shaped elements mounted on top of a grounded substrate with multiple feeds is analyzed to obtain beam scanning and large gain bandwidth, despite the ultrathin thickness. Beam steering is observed when one port at the time is excited among multiple ports distributed along the length of the array. When multiple ports are excited simultaneously, a significantly larger gain bandwidth is observed even from this ultra-low-profile configuration. A maximum gain of 5.7 dBi is achieved along with a 3 dB gain bandwidth over a wide frequency range from 19.2 GHz to 25.2 GHz (27%).

An ultrathin antenna based on a curved high impedance surface (HIS) is designed, which has wide beamscanning capability if the leaky wave is excited by proper selection of the feed location. The HIS-inspired curved printed antenna exploits the leaky wave properties of a linear arrangement of dogbone-shaped copper patches over a curved ground plane. By selecting the excitation port along the array demonstrates a beamscanning capability ranging from $\mathbf{-34^{\circ}}$ to $\mathbf{+34^{\circ}}$ . The curved HIS-based antenna exhibits a rather wide 3dB gain bandwidth. The thickness is in the order of a hundredth of a wavelength.

A 2U CubeSat, (20cm by 10 cm by 10 cm) is being developed to make impedance measurements of plasma in the ionosphere at 400 km altitude. Because the new instrument is able to make measurements rapidly, and because of the severe power and size constraints of the satellite, special care is needed in storing the measurement data and transmitting it to Earth. For both the measurements and for general housekeeping functions, the software of the CubeSat must be able to respond rapidly to events and operate in a manner that is not only flexible and extensible but also power efficient. This work outlines the process by which the software was designed to satisfy the constraints of the mission.

Background: Human milk meets all the nutritional requirements of infants for the first 6 months of life, and it is associated with a lower incidence of diarrhea than partial or artificial feeding. The infant should be exclusively breastfed for at least 4 months of life and if possible for 6 months, as recommended by WHO and UNICEF. Aim of the Study: was to assess the breastfeeding practice for children under 24 months in Arar city, as well as its relation to some sociodemographic and nutrition related variables. Participants and methods: A cross-sectional study was carried out in Arar city, mothers were selected from the attendees of 6 randomly selected primary health care centers in the city. They were interviewed and filled in a questionnaire that included the key questions. Results: 11.8% of infants received exclusive breastfeeding, 39.7% received a mix of both breast and artificial feeding while 48.5% depended only on artificial feeding. More than 50% of the studied infants were males, 70% of the mothers weren't working. No significant relationship between type of child feeding and child age, sex, mother education, mother's working status, father's work or mother age group (P >0.05). About 2 thirds of children who had mixed feeding suffered from repeated gastroenteritis, delayed teething, standing and walking. Conclusion: In accordance with the obvious deficiency of exclusive breastfeeding in Arar city which is located in Northern Saudi Arabia, we highly recommend that programs promoting exclusive breastfeeding in the first 6 months of age must be conducted to increase mothers’ awareness of the exclusive breastfeeding duration is recommended.

Sickle cell trait is highly prevalent in Saudi Arabia. However, most of the patient are asymptomatic, only few present with symptoms of the complications of the disease. We report a case of 24-year-old male who presented to the hospital with history of dull left upper quadrant, nausea and vomiting while he was on the airplane. Investigation showed a picture of sickle cell trait with hemoglobin S of 40%. Peripheral blood smear was within normal. CT scan of the abdomen confirmed the presence of splenic infraction. This case emphasized on the need to increase the level of threshold to recognize the rare complications of sickle cell trait and how to manage them appropriately.

The rate of blood flow in the skin has relevance to several cardiovascular conditions of clinical significance. However, there is no accepted fast, easy way to noninvasively measure the volumetric rate of blood flow per unit tissue volume. Previous work has suggested the potential for using skin heating from radio frequency (RF) energy in the millimeter wave (MMW) band, with simultaneous monitoring of skin surface temperature as a means for noninvasive skin blood flow measurement. This work presents a design and in vitro test results for a simple transducer for MMW blood flow measurement. The transducer consists of a Ka band microstrip antenna and an infrared temperature sensor integrated in a thermoplastic housing. A prototype was tested in a controlled flow chamber, using a commercial tissue phantom material. The device was tested at eight flow rates ranging from 0.25 ml min−1 to 20 ml min−1, equivalent to approximately 10–800 ml min−1·per 100 cm3 of tissue. The differences in temperature increase at exposure time t=60 s were statistically significant (n = 5) so as to allow resolution of flow rates of 0.25, 0.50, 1.0, 2.0, 10, and 20 ml min−1. The ensemble average of temperature increase versus time over the 60 s exposure window were described by a simple two-parameter lumped model which can be correlated with the flow rate. The flow rate model parameter does not scale directly with the flow in the experimental chamber however. This may suggest limitations either in the model or the experimental procedure.

This paper presents the initial stage of the new initiative of applying Artificial Intelligence (AI) for the predictive maintenance in the Al Ain Distribution Company (AADC). The paper first describes the maintenance methods and types applied in AADC, and the current practices related to data-collection, data-processing, decisions-making and condition-monitoring. Detailed analysis and mapping of input-output data processes are carried out for various predictive maintenance-related attributes. The paper proposes a new AI interactive screen, including online dashboard and data analytics, to ease, integrate and automate the data collection/processing/decision-making for related predictive maintenance attributes. The paper also addresses the current AI challenges of data collection/processing/decision-making, data availability/accuracy as well as data interaction and integration issues. The results of the initial stage of applying AI in predictive maintenance show that many AI applications and proposals can be adopted, such as asset’s health-index (assets condition code), ageing, condition-monitoring, peak load, planning/scheduling maintenance programs, etc.

A pair of microstrip line-fed open multi-slot antennas are presented for operation in 4G LTE bands. Two open slots are used for forming this open multi-slot configuration: one circular slot open at one side and one rectangular slot terminated in the circular slot with other end open. The open multi-slot antenna is excited by a microstrip line loaded with circular tuning stubs on the underside of the dielectric substrate. Two antennas operate independently for Multiple-Input Multiple-Output (MIMO) communications and cover a frequency range from 800 MHz to 4.25 GHz. The antenna demonstrates 137% fractional bandwidth with good diversity performance.

A set of two 1x12 linear antenna arrays, placed orthogonally, designed for operation in the 5G 28 GHz band is presented in this paper. Microstrip patch antenna elements with better than -10 dB return loss from 27.5-28.35 GHz are used for both arrays. A Dolph-Tschebyscheff excitation weighting and optimum spacing are used to achieve a gain of 15 dBi or better over a scanning range of +/- 60° from broadside.

This paper presents a small-footprint wideband, wide beamwidth circularly polarized (CP) hybrid stacked patch-ring microstrip antenna for cubesat applications. The antenna ground plane size is chosen such that it can be accommodated on the top plate of a cubesat for communicating with high-orbital satellite networks. Hybrid perturbations are applied on patch and ring for obtaining wide axial ratio beamwidth. The axial ratio bandwidth achieved is significantly larger compared to typical CP patch antennas. This design uses only one probe-feed which significantly reduces the system complexity in cubesat applications. A simulated impedance bandwidth (for VSWR ~ 2) of 8%, AR ~ 3 dB bandwidth of 6% and beamwidths in the order of 96 degrees are achieved from this antenna.

An electrically short dipole antenna (l-2m) mounted on the payload of a sounding rocket is commonly used as a probe to measure plasma properties in the earth's ionosphere. The complete measurement system consisting of the dipole and associated circuitry is called a Plasma Impedance Probe (PIP). Here we report on the behavior and impedance characteristics of an electrically long dipole antenna, obtained through a finite difference time domain (FDTD) simulation. The motivation for this study is to design a combined impedance probe - plasma wave receiver system. In order for plasma waves to be efficiently received, the dipole antenna must be optimized to receive signals usually in the electron cyclotron resonance range. However, it is found that the overall antenna behavior changes when the cyclotron and antenna resonances are moved closer to each other. In the case of our simulations, the plasma cyclotron resonance frequency is shifted lower by 20%.

A dual tuning stub loaded microstrip line-fed multi-slot antenna design is presented in this paper for operation in the L TE band. The slot antenna on a grounded dielectric slab is comprised of three wide slot sections: one horizontal slot, one vertical slot, and a circular slot joining both slots. These slots are excited by a microstrip feed line on the other side of the dielectric. This arrangement generates multiple modes that are combined to obtain a large bandwidth for covering most of the L TE band: from 850 MHz to 2600 MHz or beyond. Two similar slots and feed lines are placed on two corners of the ground plane for polarization diversity. The fabricated antenna shows an excellent agreement in terms of scattering parameters.

In this paper, a wideband circularly polarized (CP) stacked microstrip antenna is presented. CP is achieved by using hybrid perturbation technique, where positive perturbations are applied to the driven patch and negative perturbations to the parasitic patch. The axial ratio bandwidth achieved is wider than that from typical CP patch antennas. The antenna is excited by a probe-feed without requiring any complex dual feed network to generate two equal and orthogonal modes necessary for the CP generation. This reduces the system complexity and saves space in the antenna in comparison to those with dual feeds. The antenna exhibits a simulated impedance bandwidth of (for $\mathbf{S}_{11}=-10\ \mathbf{dB}$ ) 10.4%, and axial ratio (AR ∼ 3 dB) bandwidth of 2.8%. The antenna demonstrates broad axial ratio beamwidth in both planes which is useful for wide angular coverage.

The design and analysis of a miniaturised double-ridged horn antenna for active microwave imaging application are presented in this study. For such an application, a physically small horn is required. For effective signal penetration, a low frequency of operation (about 1.4 GHz) is selected. An array of these sensors is intended for use in a cylindrical breast imaging system, which is under development in the authors laboratory. The miniaturisation is achieved by loading the double-ridged horn antenna with distilled water (e r = 76), a high permittivity, but easily available material. Further size reduction is achieved by reducing the aperture size and flare length in the horn section. The frequency response and both near- and far-field patterns were studied. Two simplified prototypes were fabricated, and as per the system requirements, tested in a cylindrical container filled with distilled water. Measured and simulated reflection and transmission responses are discussed. Measured radiation patterns are compared with the simulated ones to validate the analysis.

The detailed design equations and antenna parameters for a directional antenna for breast imaging are presented in this paper. The antenna was designed so that it could be immersed in canola oil to achieve efficient coupling of the electromagnetic energy to the breast tissue. Ridges were used in the horn antenna to increase the operating bandwidth. The antenna has an exponentially tapered section for impedance matching. The double-ridged horn antenna has a wideband performance from 1.5 GHz to 5 GHz (3.75 GHz or 110% of impedance bandwidth), which is suitable for breast microwave radar imaging. The fabricated antenna was tested and compared with simulated results, and similar bandwidths were obtained. Experiments were conducted on breast phantoms using these antennas, to detect a simulated breast lesion. The reconstructed image from the experiments shows distinguishable tumor responses indicating promising results for successful breast cancer detection.

A microstrip line-fed multi-slot antenna design is presented in this paper for operation in the 4G/LTE band. The slot antenna is comprised of three wide slot sections: one vertical slot, one horizontal slot, and a circular slot joining them. All three slots are excited with a transmission line, which generates multiple modes. These modes are combined to obtain a large bandwidth for covering most of the 4G/LTE band. Dual slots are excited with two feeds for polarization diversity. The radiation patterns are provided showing this behavior of the antenna. The slots are placed in the upper portion of a grounded dielectric substrate, leaving a large area available for electronic circuitry and other functions, such as, display, speakers, camera, etc., in modern smartphones.

An elliptical planar ultra-wideband (UWB) ring antenna in the presence of a humanoid breast phantom is presented in this paper. The antenna is designed for breast imaging. Therefore, it is modeled in front of a humanoid cubic breast phantom and its performances are studied. The antenna operates in a wide frequency band from about 1.5 GHz to 7 GHz. The impedance bandwidth is about 126%. This Antenna can be used in a breast imaging system for radar based microwave imaging system for cancer detection, where wide bandwidth is required.

A printed elliptical monopole antenna operating at 1–4 GHz frequency for biomedical imaging applications is presented in this article. To reduce the reflection of the microwave signal from breast, glycerin is used as the coupling medium (er = 9, σ = 0.4 S/m, tan δ = 0.28) whose electrical properties are close to those of breast tissue. Directional patterns and reduced back radiations are achieved using a reflector. The antenna has wide impedance bandwidth from 1 GHz to over 6 GHz (over 140%), suitable for radar-based imaging. The antenna demonstrates S21 > −60 dB from 1 to 4 GHz in the coupling medium. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:808–813, 2014

The concept of adaptive array antenna is presented, where the array can be switched between a reflectarray state and a transmitarray state. Several configurations are discussed including a basic geometry comprising of just a slotted ground plane with MEMS bridges over each slot and a slotted ground plane with square patches or rings on both sides of the ground plane. In the later cases, the slots on the ground plane need to be shorted when a reflectarray is desired; otherwise, the array will behave as a transmitarray. The detail unit cell study is discussed for each case for the performance of the array. Experimental study is presented to verify the concept. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:935–938, 2014

This paper reviews the concept of an engineered conductor, introduced by the authors in order to reduce ohmic losses of miniaturized microstrip antennas [1-4]. Because of the miniaturization, the ohmic losses of microstrip antennas increase, which essentially significantly reduces their gain and efficiency. By the use of the engineered conductor concept, these two important parameters of such antennas can be improved without altering the antenna's geometry. The concept is based on using multiple laminated thin conductors, rather than one thick conducting layer, to form the microstrip antenna. The technique is applied to several miniaturized microstrip antennas in order to reduce their ohmic losses. The concept is explained using a microstrip line to demonstrate that the conductor loss can be reduced by increasing the number of layers in the lamination, while keeping the total thickness constant. Using conventional metallized substrates, the lamination reduces the thickness of each conductor layer to approximately or less than the skin depth in that conductor. Studies of two miniaturized antennas - namely, the square-ring antenna and the modified open-ring antenna - have respectively provided about 4.6 dB and 1.5 dB improvements in the gain, and from 30% to 40.7% improvement in the efficiency. Experimental investigations are also presented that confirmed the simulated results.

A microstrip line-fed slot antenna is presented in this paper to operate in the entire 4G/LTE band. The slot antenna has the letter ‘L’ shape, and when excited with a transmission line generates multiple modes. These modes are combined to obtain the large bandwidth for covering most of the 4G/LTE band. Several feedlines have been studied to enhance the bandwidth. The slot width is also varied to achieve large impedance bandwidth. The radiation patterns are provided showing the behavior of the antenna. This antenna can be further optimized to provide polarization diversity in the 4G/LTE systems. The slot antenna is located in the upper portion of the ground plane, leaving a large area available for accommodating electronic circuitry for wireless communications or display technology in modern smartphones. This area can also be utilized to incorporate millimeter wave antennas to make the device compatible for future 5G wireless systems.

On-body printed antenna is a rapidly growing research area targeted for healthcare, biomedical, public safety and military applications. Printed antennas in both microwave (MW) and millimeter wave (mmWave) frequency bands have been found useful for Wireless Body Area Networks (WBAN) and medical devices. While miniaturization, conformability and good near-field patterns have prime importance in the antenna design, the interaction of RF signals with human body and the effective signal penetration need to be assessed carefully during the design phase. An on-body 2×2 printed antenna array is under development at mmWave frequencies on a flexible material. The single patch antenna design and results are presented in this paper. The return loss data due to the close proximity of skin is also discussed. The results from the array showing specific absorption rate (SAR) and power density (PD) profile on an experimental phantom using a high-resolution infrared camera will be presented at the symposium.

A wideband single probe-fed stacked patch-ring antenna is presented in this paper, which uses hybrid perturbations to generate circular polarization radiation. A wide beamwidth is obtained when a combination of a square ring with negative perturbation and a square patch with positive perturbation is used as parasitic and driven elements, respectively. This arrangement provides circular polarization with improved performance. A simulated impedance bandwidth (VSWR < 2) of 12%, 3-dB axial ratio bandwidth of 6.5%, a peak RHCP gain of 8.1 dBic, and a beamwidth of 116° are obtained from this antenna.

The unit cell study for a tunable Frequency Selective Surface (FSS) is discussed in this paper. L-shaped slots with varying lengths are used as elements for the FSS. This shape has advantages of reduced size and arranging more L-shaped slots. For multiband operations, multiple L-slots can be used. A case with two L-shaped slots is presented in this paper. For tuning to a desired frequency, all slots except the slot resonant at that frequency have to be shorted using solid-state electronics or micro-electromechanical systems.

Ultra Wide Band Radar is a novel technology used for breast cancer detection. This imaging modality uses ultra wide band waveforms to form a reflectivity map of the breast region in which tumors can potentially been clearly distinguished. In this study, the authors assess the use of a novel Breast UWBR reconstruction approach, microwave holography, on anthropomorphic phantoms. These phantoms mimic both the shape and dielectric properties of human breast. The images formed using microwave holography are consistent with the location of the synthetic breast structures and show signal to clutter level above 3dB.

Stacked electromagnetically coupled square ring antennas with extremely thin spacing are studied. The separation between rings is kept very small so that they do not increase the overall antenna height, yet can provide multiband operation. The coupling effects among these very closely placed rings are studied based on substrate parameters so that they can be practically implemented using commercially available microwave substrates. It is observed that with an asymmetric arrangement of the stacked rings, different polarizations can be obtained for different resonances. However, if a fixed polarization is desired, a concentric stacked rings configuration has to be used. Experimental investigations are conducted to confirm simulation results.

Multifrequency operation can be obtained from the single-layer probe-fed annular ring antenna by loading it with a gap or slit. Two types of loading are studied: vertical and horizontal gap. For each case, two unloaded modes are excited around the dominant TM11 mode of the ring, equally spaced on the frequency spectrum. These multiple modes are excited, when the loading is symmetric on one side of the ring along one axis, and the excitation is off-centered on another side, or vice-versa. By choosing the location of the vertical or horizontal gaps along the y- or x-axis respectively, the polarization of each mode can be controlled. One of the loaded mode frequencies is much lower than the dominant TM11 mode frequency of the annular ring, indicating a miniaturization of antenna to a great extent. Effects of substrate parameters are investigated on the loaded and unloaded mode frequencies, and a design guideline is presented. Simulation results are confirmed by measurements.

This paper presents a method of wideband circular polarization (CP) generation using a stacked patch-ring microstrip antenna with a single probe feed. An enhanced axial ratio (AR) bandwidth is obtained when a combination of a square ring and a square patch with negative perturbations is used as parasitic and driven elements, respectively. The axial ratio bandwidth obtained is significantly larger compared to the case when square rings are used as parasitic and driven rings with a single feed. A simulated impedance bandwidth (Sn< −10dB) of 16%, 3dB AR bandwidth of 8%and a peak gain of 8.65 dBic are obtained from this antenna.

A cavity surrounded stacked circular patch antenna is investigated as a feed for prime-focus reflectors in this paper. The radiation patterns of this feed are slightly asymmetric in the E-plane, which are improved by a differential feeding technique using two probes. This feed has a bandwidth of 20%, and wide beamwidths which improve the overall efficiency of symmetric parabolic reflector antennas.

Reduced size microstrip monopole slot antennas with different slot shapes-straight, L and inverted T, and placed on a small ground plane, are investigated. The ground plane size is 50 mm/spl times/80 mm, which is about the size of a typical PC Wireless card. Detailed simulation and experimental investigations are conducted to understand their behavior and optimize for broadband operation. It is shown that, the variation in the slot shape, from straight to L and T shapes, helps in generating additional resonances, which when coupled to the original resonances of the slot, further increases impedance bandwidths. The bent shapes of the L and T slots reduce their height and provide more space on the ground plane for electronics. A mirror image dual L-slot antenna, placed at two adjacent corners of the ground plane, is also investigated and optimized for the polarization diversity. They provide an impedance bandwidth of 87%, with near orthogonal radiation characteristics. The measured impedance bandwidths (S/sub 11/=-10 dB) of up to 60%, 84%, and 80% are achieved for these straight, L and inverted T slots respectively, by suitably selecting their design parameters. The simulation results are in good agreement with the experimental data considering several practical issues.

Tuberculosis is a multiorgan disease with varied clinical presentations and is reemerging due to increasing immigration and globalization. We present the case of an immigrant female patient who developed acute renal failure with clinical and biochemical features suggestive of lupus nephritis but with a timely renal biopsy showing caseating granulomata in the renal parenchyma consistent with renal tuberculosis. Despite treatment with antituberculosis treatment and resolution of TB on repeat renal biopsy, she remained haemodialysis dependent. We discuss the diagnostic challenges faced in this presentation and also explore possible differential diagnoses. This rare presentation highlights the importance of renal biopsy in the diagnosis and treatment of acute renal failure and the atypical presentation of tuberculosis.

Breast Microwave Radar is a novel imaging modality for breast cancer detection. This technology uses low power microwaves to illuminate the breast region and it generates a reflectivity map of the breast structures in which tumors can be detected. Although this imaging modality has been successful in limited clinical trials, additional work is needed to optimize several parameters of this technology to increase its use in routine clinical imaging procedures. One of the aspects that is crucial for the performance of a BMR system are the antennas used to record the datasets. In this study, the use of a novel horn antenna for BMR data collection is proposed. This antenna was used to record BMR datasets from synthetic phantoms that mimic the dielectric properties of breast tissues. Datasets from these phantoms were also collected using a Vivaldi antenna, which is a common design for current BMR systems. The results of this study show that images formed from datasets recorded using the horn antenna had a lower noise level and higher contrast compared to their counterparts corresponding to the Vivaldi antenna datasets.

Modifying a solid conductor with multiple thin laminated conductors can significantly reduce the ohmic loss of microstrip conductors. This concept can be used in circuits and antennas where substantial conductor loss occurs. The lamination in the composite material is realized using dielectric material. The laminating dielectric thickness is smaller or of the order of the skin depth of the conductor. First, it is shown analytically that in this composite material, the power lost is less in the conductor with several laminated conductors instead of a single solid conductor having the same thickness. The concept can be used in miniaturized antennas having poor gain due to a very high ohmic loss to improve their gain and efficiency by reducing the loss using multiple laminated conductors.

The design of a double-ridged horn antenna for medical imaging is presented in this paper. The antenna is immersed in canola oil to reduce its size and to achieve efficient coupling of the electromagnetic energy to the breast tissue. The antenna has wideband performance from 1.5 GHz to 5 GHz (3.5 GHz or 108% of impedance bandwidth), which is suitable for radar-based medical imaging. The double-ridged horn antenna has exponential tapered section for impedance matching. The detail design equations and antenna parameters are presented. The fabricated antenna was tested and compared with simulated results, and excellent agreement has been observed.

A stacked circular patch antenna is studied to be used as the reflector feed. Large bandwidth is achieved using stacked patches. Circular symmetric patterns with low cross-polarization are achieved from this antenna by optimizing the ground plane size for a particular substrate permittivity. With a ground plane size of only 0.3λ, good front-to-back ratio is also possible along with good pattern symmetry and low cross-polarization.

Since the advent of Radio, the communication technology and remote sensing science have gone through continuous evolutions and transformative advances. Both these areas use electromagnetic waves for operation and antennas to generate, transmit, and receive them. Thus, the antenna area has also gone through transformative advances, from low gain low frequency wire antennas, to high gain high frequency antennas, and recently into millimeter bands. The move into high frequency bands has increased the resistive losses of the antennas and lowered their operating efficiencies. At the same time the antenna miniaturization, which has resulted from RFID and personalized device applications, have also impacted the antenna efficiency through increased losses. Therefore, there is a need for a new design concept to overcome the antenna losses. Device miniaturization and space limitations in ever increasing complexity of equipment have also increased the need for hardware minimizations. Both problems will be addressed in this paper and effective remedies will be presented using the engineered conductor design and the virtual array concept.

A miniaturized double-ridged horn antenna for use as an array element in the Subsurface Radar (SR) system is presented. SR has been proposed for some emerging applications such as breast imaging and wood inspection. A cylindrical scanning geometry is proposed which will host 72 antennas in a row for illuminating the target and receiving scattered signal. The scanning system will have several rows of antennas for better sensitivity and spatial accuracy. The designed double-ridged horn antenna shows promising results with good transmission characteristics.

The design of a miniaturized double-ridged horn antenna for use as an array element in the Subsurface Radar (SR) system is presented. The array antenna system will be arranged in a cylindrical scanning geometry which will host 72 antennas in a row for illuminating the target and receiving scattered signal. The scanning system will have several rows of antennas for better sensitivity and spatial accuracy. The antenna element of the array has several critical parameters, which influences the antenna performance. Other system parameters are antenna spacing, their angular positions and distances from each other. Based on the parametric studies, two prototypes were fabricated and tested to determine their suitability in the proposed imaging application.

A physically small - sized double-ridged horn antenna is presented for use as an array element in the Subsurface Radar (SR) system. The miniaturization is achieved by loading the antenna with a very high-permittivity material and also by reducing the flare length in the horn section. The effects of size reduction on the reflection and transmission response of the antenna are studied.

The development of an adaptive surface is presented, which can be switched between a transparent surface and a reflective surface. MEMS-bridges are used as the controlling device. The surface consists of a ground plane with apertures and square ring elements on both sides of the plane. MEMS-bridges can block the apertures for the reflection operation, otherwise the surface will behave as a transparent one. The unit cell study is discussed for the performance of the surface.

Circular patch is one of the few basic geometries of microstrip patch antennas, and have been studied extensively in the literature [1, 2]. Typically, a substrate material is used between the patch and the ground plane to give the mechanical support to the antenna. The performance of microtrip antennas is strongly dependent on the properties of the substrate material used. Sine electromagnetic wave is trapped inside the dielectric material, the radiation patterns of the microstrip antenna are affected by the substrate. It has been observed that for a certain value or range of the substrate permittivity, the co-polarization patterns of E- and H-planes of the circular patch antenna, for the dominant and several higher order modes, become nearly equal to each other at least in a particular range of elevation angle. This paper discusses this interesting phenomenon using commercial electromagnetic (EM) software: Ansoft Designer, version 4.

Transmit-array is an alternative of lens antennas which transmits electromagnetic (EM) waves. The EM wave is received at one side of the surface, and the phase of each element is adjusted to retransmit it from the other side [1–3]. It has become very popular due to the advancement of printed antennas because of low surface profile, small mass and low cost [4]. Using MMIC and MEMS technologies, thousands of printed patches can be etched on a dielectric substrate to form an array which acts as the transmit-array. By controlling the phase of each element, beam steering can be obtained easily.

Reflect-array antenna was introduced to replace parabolic reflectors, as they offer many advantages including beam steering, ease of fabrication, lightweight, etc. [1]. The electromagnetic energy should reflect back when it hits the reflect-array surface. It has become very popular due to the advancement of printed antennas because of low surface profile, small mass and low cost [2, 3]. We have been studying microstrip rings as the cell element to obtain a reflect-array. When there is an aperture on the ground plane, the distance of the rings can be adjusted to obtain appropriate phases so that the electromagnetic energy can propagate through the ground plane or reflect back. The aperture size is another important parameter to obtain the reflection. When the aperture on the ground plane is partially shorted using a micrsotrip, the length of the aperture is essentially reduced, and the reflection from the structure can be achieved. In this paper, simulation results of the unit cell of a reflect-array are discussed, which is based on square rings with an aperture on the ground plane. The effects of the aperture size and the use of shorting strips are presented. The cell is in an infinite array environment. Simulations were carried out in Ansoft HFSS, version 12.

The microstrip circular patch antenna is very popular for mobile and satellite communications applications [1, 2]. In order to have the mechanical strength of this patch antenna, typically a dielectric substrate material is used between the patch and the ground plane. Since the electromagnetic wave is trapped inside the dielectric material, the radiation patterns of any microstrip antenna are affected by the substrate. In this paper, the observation of obtaining nearly–equal co-polar patterns in the two principal planes from circular patch antennas is presented. Especially, with a finite ground plane, radiation patterns in two principal planes are investigated to find a range of the elevation angle for a particular substrate permittivity, in which the E- and H-plane co-polarization patterns are equal.

Although reflect-array and transmit-array are not new technologies, developing an adaptive surface to achieve both reflection and transmission, when required, will be another important technology, which will be advantageous for many applications. A structure with two electromagnetically coupled printed antennas is presented to obtain such a surface. The key factor for obtaining the adaptive nature of the surface is to receive and reradiate the energy on the same side when a reflection is desired, and to ensure efficient coupling of energy from one side to the other when a transmission is desired. An electronic circuitry with active elements will be required to achieve this performance. Beam steering is also possible by controlling the phase of individual unit in the array.