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In this paper, numerical investigation on GaN HFETs is carried out using hybrid finite element method (FEM) which combines the FEM with the preconditioned conjugated gradient technique. The maximum temperatures of the HFETs operating under continuous-waves (CW) and pulsed-waves (PW) are both captured accurately. The effects of temperature- dependent thermal conductivities of the materials on the temperature...
In this paper nonlinearities due to FET amplifiers are described by using a novel behavioral modeling approach. While our proposed method requires the identification of delays and coefficients like in a standard diagonal memory polinomial model, the importance of out-of-diagonal terms is emphasized if the amplifier exhibits memory effects. Furthermore, the different terms, delays and coefficients...
A double tuned Ku-band SiGe-MMIC voltage-controlled oscillator (VCO) with variable feedback capacitor is presented. The proposed VCO employs series varactors in feed-back paths in addition to varactors in tank circuit. By controlling both varactors, this VCO achieves wide tuning range compared to the conventional LC cross-coupled VCO. Furthermore, appropriately biased MOS varactors for feed-back paths...
In order to improve the operation reliability of passive transponders (e.g. for radio frequency identification applications - RFID), the design of low-loss integrated circuits and the development of efficient energy scavenging devices are an emerging task. This article deals with general considerations regarding self-sustaining integrated transponder devices with integrated RF power rectifiers and...
A novel metallic wire substrate (MWS) is proposed for miniaturized planar microwave circuits. This MWS consists of a dense array of vertical metallic wires embedded in a regular host substrate. It is demonstrated experimentally to exhibit magneto- dielectrics properties with simultaneously enhanced effective permittivity and permeability in a broad frequency range. Consequently, a substrate of higher...
This paper presents a simple ultra wideband pulse generator circuit using only two SRD components. The result shows a Gaussian pulse 340 psec in width. In addition, high order derivative Gaussian filter with microstrip line and parallel stub was designed and fabricated so that DS-UWB pulse generator could reduce the frequency spectrum of WLAN by 25 dB compared to the spectral power of the adjacent...
A particle for artificial magnetic material in microwave frequency is proposed. It has simple structure composed of two-parallel conductor. The characteristics of effective permeability are discussed based on the transmission line model for miniaturization and increase of the permeability. The plate-type material where the particles are placed is fabricated and the characteristic is confirmed.
In this paper we present a parameter estimation problem for practical electromagnetic signals generated by dipole antennas positioned close to a receiving antenna of uniform circular array (UCA). The positions (direction of arrival and range) and the radiation characteristics of emitting sources are being estimated using super resolution techniques. We also estimate the time difference of arrival...
A tunable and configurable photonic microwave bandpass filter with negative coefficient is proposed and demonstrated. Based on all-optical mixing in an intensity modulator and a phase modulator, the filter frequency response is related with the frequency of local RF signal (LO) signal and dc bias applied to the intensity modulator. The free spectral range of filter passband can be tuned conveniently...
This paper presents a detailed study of the shielding effectiveness of a rectangular metallic enclosure with apertures by using an analytical formulation and experimental study. The theories developed by other researchers have been extended to take into account the contribution of multimode of propagation in the enclosure. Both the electric and magnetic shielding effectiveness were calculated as a...
In this paper the analytic solutions of ground bounce problems on the power/ground plane structures of printed circuit boards (PCBs) are presented based on the perfect magnetic wall assumptions of the PCB's edges. The Green's function of the infinite power/ground plane is first derived, and then the sidewall reflections are replaced by the image sources, resulting the voltage expressions on the PCB...
This paper proposes a new type of wireless services over IP networks (WoIP), which enable voice communication sessions among mobile terminals with different types of air-interfaces. A SIP (session initiation protocol) server administrates the sessions, and realizes a call between WLAN (wireless LAN) and PHS (personal handy-phone system) terminals via IP network. Their service areas are experimentally...
The paper deals with permittivity measurement of biological materials and materials close to them. The used methods are presented and their appropriateness for particular materials is given. The achieved results are given in table and graphs and also similarities in courses of particular materials as well as anomalies are discussed.
In motion slot array antenna for receiving satellite broadcasting is presented. To reduce the loss of feed line and to reduce the coupling between the slots, we use the waveguide feeding network and the circular groove. By using two cross-type polarizers, which are implemented on a single layer film, the proposed antenna can receive RHCP or LHCP by mechanical switching system. The gains of 4x8 and...
In designing high power microwave antenna system, breakdown effect is one of the most important factor to consider. When coaxial beam-rotating antenna (COBRA) lens is used as high power microwave system, the size of antenna should be larger to prevent the breakdown due to the reflected wave from lens. In this paper, the method of miniaturization and improvement of pattern by compensating phase error...
In this paper we demonstrate that the anisotropic property of liquid crystal can be exploited to control the phase of signals that are reflected from a reflectarray cell. Numerical and measured results at X-band are used to compare the plane wave scattering from two reflectarray cells which are constructed on liquid crystal film of thickness 200 mum and 500 mum. The phase agility, bandwidth and reflection...
In this paper, we present a planar highly shaped-beam antenna made up of a line source embedded in a structure containing a metal reflector and a dielectric layer coated with metal strips. We have fabricated and measured the radiation characteristics, including the return loss and radiation pattern. Besides, the rigorous mode-matching method incorporating the equivalent principle was employed to calculate...
In this paper, a new compact low-pass filter with three finite attenuation poles at stopband is presented. The new structure is composed of a pair of symmetrical parallel coupled-line and a shunted capacitor. With this configuration, three finite attenuation poles can be available for 2nd, 3rd, and 4th harmonics suppression. The research method is based on transmission-line model for tuning the attenuation...
Efficient and wide band frequency conversion using a finline with a silicon substrate has been discussed. Laser pulses move along the finline as generating an electron-hole plasma at the surface of silicon in the fins. The plasma acts as a rf-short moving at a relativistic speed, reflecting an incident wave and up-shifting its frequency through the double Doppler effect. The theoretical results have...
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