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The talk will focus on intriguing properties of asymmetrical adaptive large and medium aperture antennas. Several adaptive medium size antennas will be discussed to demonstrate their attractive potentials as primary feeds. First, an adaptive virtual array is realized in a single large aperture antenna such as a parabolic reflector. Both symmetric and offset reflector structures will be addressed....
More and more research is being done in extremely high frequency bands that exceed the frequency ranges of single box signal generators and spectrum analyzers. This necessitates the use of frequency multipliers on the generation side, and harmonic mixers to extend the frequency range of the spectrum analyzer. With these setups there are certain important parameters that should be taken into account...
Mixers are one of the fundamental components of many receivers and transmitters, especially in the microwave range. Any mixer-based receiving or transmitting system requires that each mixer has well-known amplitude, group delay and phase responses. A linear phase and constant group delay in particular are essential for low bit error rates (BER) during data transmission in wireless and satellite communications...
A 20/30GHz Frequency Selective Surface (FSS)-backed reflectarray is introduced in this paper. This reflectarray is designed as part of a shared aperture reflectarray for simultaneous operation at X- and Ka-band. The reflectarray is illuminated with a circularly polarized (CP) feed and the elements are designed to collimate the beam in a desired direction. Separate reflectarrays with frequency selective...
In this paper, a new method is presented to excite an open-ended circular waveguide feed. A circular microstrip patch element is embedded near the bottom end of the waveguide, which excites the dominant TE11 mode at the aperture of the antenna. The technique is simple and capable of generating a relatively pure mode over a respectable frequency band. The technique eliminates the need of using a waveguide...
The radar cross section (RCS) of an iceberg is derived in the context of a monostatic high frequency surface wave radar with a vertical dipole source driven by a pulsed waveform. The starting point of this derivation is the backscattered electric field equation as found in previous work. This equation is simplified by restricting the iceberg size to fit within the radar system's patch width. After...
A new ultra-wideband (UWB) pattern diversity antenna design is proposed and simulation results are presented. With a size 40×42×21 mm3, the proposed antenna structure consists of a disk radiating element, fed at two points at 90° angle by two coaxial lines. The excitation of feed lines determines the radiation pattern of the antenna, which is either directional or squinted. The disk and its feed lines...
We have derived an integral equation using the dyadic Green's function on the assumption that there exists a random medium screen of which the dielectric constant is fluctuating randomly. On the integral equation, the depolarized EM wave has been analyzed by using a perturbation method, and we have shown the representation of the first order perturbation of the depolarized EM wave.
Finding the location of a mobile agent has been long an issue of interest for many applications. Many techniques have been introduced for local position estimation which are usually based on array concept and typically apply either of frequency or phase variation methods. Arrays are usually used in the receiver side and the problem is to find the position of the transmitter. In this study, a new Line-of-Sight...
To obtain wide bandwidth and high gain at millimeter wave frequency, Antipodal Fermi-Linear Tapered Slot Antenna (AFLTSA) is proposed. The proposed antenna achieves wide bandwidth from 23 to 33 GHz as well as flat gain of 14.5 dBi over wide operating frequency band. It achieves the side lobe level of −8 dB in H Plane and −16 dB in E plane. Proposed design also achieves the front-to-back ratio of −20...
A negative permittivity (ENG) zeroth-order resonance (ZOR) antenna with compact size and low profile is introduced in this paper. By adding a shorting via and applying capacitive coupling feeding technology, the antenna could operate in the center of f0 =5.084GHz, which is corresponding to the electric size 0.273λ0×0.273λ0×0.0136λ0 (where λ0 is the wavelength corresponding to the operational frequency...
We characterize an improved fully-printed biplanar volumetric negative-refractive-index transmission-line (NRI-TL) metamaterial lens, which utilizes new double dual-arm spiral inductors and metal-insulator-metal capacitors as loading elements. The structure exhibits a NRI property from 3.92 GHz to 4.57 GHz. At these frequencies, the structure is shown to be isotropic and possesses a small electrical...
This paper investigates a novel method based on the application of stepped impedance resonator technique used for miniaturization of metamaterial unit-cells. The effect of this technique on the S parameters of well-known rectangular and circular metamaterial unit-cells is studied and it is shown that this technique works well for both type of structures.
Unlike its conventional counterpart, a new vector basis function based meshless method that preserves the divergence property of electromagnetic fields is proposed for solving transient electromagnetic problems. Its divergence properties are investigated through numerical experiment; it is found that artificial charges generated by the proposed method are not present while they are in the conventional...
Ionospheric clutter is one of the main sources of interference affecting the performance of high frequency surface wave radar (HFSWR). One component of this arises from a portion of the transmitted radar signal which is reflected from the ionosphere to the ocean surface, from whence it is backscattered to the receiving antennas. The influence of the ionospheric reflection can be accounted for by a...
A planar Ku-band broadband phased array antenna has been realized for satcom terminals suited for aeronautical platforms. The antenna Rx module includes an RF front-end connected to an optical beam forming module. This combination guarantees a squint-free beam steering over the whole commercial Rx Ku-band. This document describes the design, manufacturing and testing of the RF front-end.
A novel Push-Push oscillator array with simple structure is proposed. The Push-Push oscillators are connected via a coupling circuit whose structure is very simple. The phase shift between the output signals of the oscillators is achieved by controlling the phase difference of the reflection coefficients of the coupling circuit. The phase difference is changed by the bias voltage of the HEMT used...
Non-reciprocity, tunability and gyrotropy of graphene magnetoplasmons in various magnetically biased graphene structures are investigated. Novel terahertz non-reciprocal devices are proposed.
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