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An active hybrid shared-aperture concept (employing both active and passive circuits) is presented. This active shared aperture realizes the required isolation level of 48 dB between transmit (30 GHz) and receive (20 GHz) channels of a ground terminal for two-way satellite communication. It can be applied in Very Small Aperture Terminals (VSAT). The dual-frequency shared aperture can be used as a building block for a linearly or circularly-polarized phased-array feed in a focal-plane array (FPA) system. It includes a 20 GHz low noise amplifier (LNA) with on-chip notch filtering realized in a 0.25 μm SiGe:C BiCMOS technology. The on-chip filter achieves 30 dB of attenuation at 30 GHz with only 0.4 dB noise figure degradation. The isolation is further enhanced by a novel dual-frequency shared aperture concept, based on defected ground structures (DGS) in the PCB. Experimental results from the prototype show an overall isolation between transmit and receive channel of more than 50 dB at 30 GHz.

This paper presents a millimeter-wave tunable hybrid-transformer-based duplexer concept with dual-antenna configuration. By using orthogonal sequentially-rotated linearly-polarized antennas and the hybrid-transformer-based duplexer, the transmitter and receiver duplexes the two antennas with orthogonal circular-polarized signals. An on-chip tuning technique using magnetic coupling is introduced to improve the isolation of the duplexer in case of impedance imbalances. An alternative duplexer with a similar principle using an on-board rat-race coupler is also proposed and designed for comparison. In order to demonstrate the isolation with practical antenna connections, prototypes have been developed to integrate the on-chip duplexer and the rat-race coupler with on-board aperture-coupled microstrip antennas with sequential rotation technique. Measurement results demonstrate the orthogonal circular polarizations for the receiver and transmitter modes on both prototypes. The achieved isolation by the on-chip tunable duplexer is better than 50 dB between 30.2 and 31.2 GHz, while the achieved isolation by the rat-race version is about 20 dB in the same bandwidth.

The problem of beam squinting in circularly polarized offset reflector antennas is solved by using a novel focal-plane array concept that consists of sequentially rotated linearly polarized elements. This concept can be used to facilitate beam steering in full-duplex communication with satellite Internet (VSAT) operating in the Ka-band. A prototype consisting of a 75-cm offset dish illuminated by a $2 \times 2$ array of sequentially rotated aperture-coupled microstrip antennas was developed and tested at 20 GHz. Experimental results clearly demonstrate the removal of the beam-squint and resulted in an axial ratio (AR) below 1 dB within the 1-dB beamwidth of the main beam.

This paper presents a novel technique to accurately measure the RF voltage across the tuner in order to ease the design procedure of aperture tuned antennas. The presented approach can be used together with MEMS based variable digital capacitors with high voltage handling to achieve efficient RF performance. An example of a tunable antenna with high voltage handling is described.

It is shown that metal gratings can be used to improve the cross polarization of circularly-polarized aperture-coupled microstrip antennas. The metal gratings reduce edge difiraction from the flnite- size grounded dielectric slab on which the antennas are printed. The edge difiraction is due to surface waves that can propagate in the grounded dielectric slab. The design of the metal grating is based on an analytical model, which results in a flrst-order estimation for the design of the metal grating structure. The model provides physical insight and appears to be accurate enough for the application. Using this model, a prototype was developed, consisting of a circularly-polarized 2 £ 2 microstrip array with associated feeding network. Measurements show that the axial ratio can be reduced down to 1.75dB within the beam width of the antenna.

Despite the common belief that multiple sclerosis (MS) is a painless disease, several studies contradict this. There are a significant number of MS patients who actually suffer from painful conditions such as central and peripheral neuropathy, migraines, trigeminal neuralgia, painful tonic spasms, complex regional pain syndrome, glossopharyngeal neuralgia, and transverse myelitis. In addition, MS relapses are usually painful with many patients complaining of paroxysmal dystonia and neuropathic pain during these episodes. Additionally, treatments for MS such as use of beta-interferons may be associated with headache and pain at the injection site. The pathophysiology of pain in MS is poorly understood, but may be related to the development of demyelinating lesions involving certain neuroanatomic pathways such as the spinothalamic tract. Management of pain in MS patients is a therapeutic challenge for clinicians. Currently, various pharmacological agents such as antiepielptics, non-steroidal anti-inflammatory agents, and even corticosteroids are used to suppress various painful conditions associated with MS. Non-pharmacological procedures such as massage therapy have also been used in the treatment of MS patients. The authors present a review of recent findings in pathophysiology and management of pain in MS patients.

This paper presents the performance of a focal plane array operating in transmit mode at 30 GHz for use in future Very Small Aperture Terminals (VSAT). The performance of the array is analyzed in front of a reflector with a small F/D ratio. The focal plane fields are synthesized using an array with aperture-coupled microstrip antennas. This configuration is used to determine the optimal excitation coefficients. A Silicon transmitter integrated circuit (IC) using a phase shifting up-converter operating at 30 GHz is designed and measured together with the antenna to generate a complex gain constellation for the required beam steering. The experimental results are used to calculate the far-field pattern of the complete system.

A 30/35 GHz dual-band phased array transmitter (TX) front-end is demonstrated in a 0.25um SiGe:C BiCMOS process. The front-end provides variable phase shifts from 0°~360° with a ~10° resolution. A 5-bit amplitude resolution is achieved for advanced beamforming algorithms. Accurate transmitted beam patterns can be generated by applying a genetic algorithm with the achieved phase and amplitude resolution. The front-end transmits a >+14dBm saturation output power with >+15dB gain and >+22dBm OIP3 at 30/35GHz.

In multimode transceivers, the transmitter for one communication standard induces a strong local interference in the receiver for another standard. Such strong interference can severely affect the receiver, if it is not suppressed at an early stage of the receiver. A widely explored method to cancel a locally induced interference is to construct its replica, using an analogue model of the interference coupling path, and subtract it from the received signal. Performance of the cancellation method mainly depends on the model accuracy which is limited by the affordable complexity. This paper performs a feasibility study on the application of the cancellation in multimode transceivers based on a simulated scenario. In contrast to previous works, the presented analysis allows an easy comparison between variations of the cancellation method with different complexities. It is found that with a practical complexity the model is not sufficiently accurate. Thus only cancellation in a narrow band is attained. Moreover, the coupling of the local transmitter noise to the local receiver increases. A more accurate model can improve the cancellation; however, it is overly complex for mobile devices. This suggests the requirement for alternative methods to successfully mitigate the local interference.

This paper presents the design of a dual-frequency filtenna using a defected ground structure (DGS). A shared aperture coupled microstrip antenna operating at 20/30 GHz (Ka band) is integrated with a coupled-line bandpass filter to increase the isolation between the transmit and receive channels. It is shown that the presence of slots in the ground plane can significantly increase the coupling between the coupled lines. The proposed technique allows for the design of tightly coupled lines without the necessity of using very narrow gaps. The integrated module can be made small enough to fit within an array unit cell for satellite communication applications.

This paper discusses the main issue of commercial RFID tags, which is the reduced range of the RFID tags when placed in the proximity of complex environments (e.g. food or human bodies). A short overview of the design aspects of UHF RFID antennas in complex environments is presented. Water, blood, heart and muscle tissue are used as environments. An antenna with a protecting ground plane that reduces environmental influence is presented. Several system-level measurements were done in order to compare the prototype (including and embedded IC) with commercially available RFID tags. In addition, a robust antenna with a reduced size (factor of 5) is presented with an efficiency of 84% at 868 MHz when placed on a water tank.

It is shown that metal gratings can be used to improve the cross polarization of circularly-polarized aperture-coupled microstrip antennas. The metal gratings reduce edge diffraction from the finite-size grounded dielectric slab on which the antennas are printed. The edge diffraction is due to surface waves that can propagate in the grounded dielectric slab. The design of the metal grating is based on an analytical model, which results in a first-order estimation for the design of the metal grating structure. The model provides physical insight and appears to be accurate enough for the application. Using this model, a prototype was developed, consisting of a circularly-polarized 2×2 microstrip array with associated feeding network. Measurements show that the axial ratio can be reduced down to 1.75 dB within the beam width of the antenna.

This paper describes an investigation of the focal plane field distribution of an offset reflector antenna. A physical-optics model is developed to calculate the near-field data at the focal plane. A 70 cm offset reflector antenna comparable to a standard satellite TV set has been our study case. As a starting point in our design process, we have investigated the optimal size of the focal plane array (FPA) for offset reflector antennas and achievable scan ranges. This study gives the guidance to the antenna designer for optimal FPA size, the proper F/DP and the required number of array elements.

Circularly polarized radiation is frequently used in satellite communication. This paper discusses how circular polarization can be generated by means of an array of linearly-polarized antenna elements by applying the sequential rotation technique. A calibration method is used to improve the axial ratio from ±30° to ±60° off bore sight by using a 4-bit accuracy for the active components. A measurement campaign was organized based on a demonstrator developed at ASTRON. The calibration of the axial ratio is applied to the measured element patterns of the ASTRON egg-crate structure antenna array operating at 7.14 GHz. The results prove that the axial ratio can be improved significantly. Finally the same technique will be applied to a linear array operating at 20 GHz with sequential rotation configuration in front of the reflector to improve the axial ratio in the boresight direction.

The aim of this paper is to present a hybrid approach for designing focal plane arrays using commercially available software, considering the fact that the main trade-off in the EM simulation is the accuracy versus computational power. The presented approach is hybrid method based on FDTD/PO. The optimization process, based on the alternating projection algorithm and projection matrix method, is performed on the embedded element patterns in order to fit the gain of the complete system onto the pre-defined mask.

In this study, a method for amplitude and phase constrained focal plane array pattern synthesis based on the intersection approach and Gram-Schmidt orthogonalization is presented. A new formulation for alternation projection, which leads to a efficient and simple algorithm, is given. The basic idea of the method is to utilize Gram-Schmidt orthogonalization as the projection operator in the iteration step of the alternating projection method. A number of examples are presented to highlight various aspects of the proposed method.

This paper presents a general technique for the synthesis of the antenna radiation pattern which does not require the calculation of derivatives or calculation of the Fourier transform. A new alternative formulation will be presented for the intersection method. The main concept of this method is to find a common point of many different sets using the projection matrix algorithm. The method with necessary amendments is then employed for focal plane arrays to find the proper excitation coefficients which fits the pattern into the desired mask. The method is found to be faster than the gradient search algorithm which is commonly used for beam synthesis. Numerical results for a focal plane array are shown and advantages discussed.

Wideband antenna technologies are in growing interest for future radio telescopes, such as in 1–10 GHz SKA (the squire kilometer array) [1] and 2–13 GHz VLBI 2010 (VLBI=Very Long Baseline Interferometry) [2] projects. The Eleven antenna, a new decade bandwidth log-periodic dual-dipole antenna developed at Chalmers University of technology, has very good features for applications in these radio telescopes due to the nearly constant beamwidth with about 11 dBi directivity, the fixed phase center location over the whole bandwidth, low profile, cryogenic cool-ability, high A/T values and simple geometry [3] [4]. A dual polarized Eleven antenna is shown in Fig. 1.