New cross-coupled bandpass filters using half-wavelength (λ/2) and branch-line resonators are proposed. The branch-line resonators are made of two quarter-wavelength (λ/4) resonators in which a shorted circuit is realized by one open stub. In the first case, a non-0°feed structure at the input and output resonators is used to produce one pair of transmission zeros near the passband to improve the selectivity. In the second case, good selectivity and improved stopband rejection can be achieved at the same time by utilizing a 0° feed structure. Specifically, the proposed filters can simplify the manufacturing process of the conventional cross-coupled filters using λ/2 and λ/4 resonators without increasing circuit area significantly.
This paper presents the modified design that can reject harmonic components in the branch-line coupler. After adding open stubs at the center of branch lines of the traditional design, their new network parameters can be found in order to maintain the conventional function at an operating frequency and suppress its harmonic terms chosen. Experimental results show the second and third harmonic suppressions to be -28.3 and -39.6 dBs, while maintaining its traditional performance at the fundamental frequency.
A sleeve monopole antenna, which has a wide impedance bandwidth for indoor base station applications, is successfully realized experimentally and numerically. The proposed antenna consists of dual sleeves, loaded circular disc and two shorted pins which are connected to the circular ground plane. The antenna possesses 14-dB impedance bandwidths of 30.3% and 46.5% at the lower and higher bands, respectively. And the 10-dB return loss bandwidth of the antenna is 128.2%, which is about 48 times that of the traditional monopolar wire-patch antenna. The antenna is successfully simulated, designed, and measured, showing dual-band and wide band characteristics, stable gain and good omni-directional radiation patterns.
Two microstrip fed ultra-wideband (UWB) antennas with different band rejection techniques are presented in this paper. The designed antennas consist of a defected ground plane with an elliptical slot and two different radiator shapes. The first design is composed of a half circular ring radiator element while the second one uses a crescent shaped radiator. The radiators are fed by a 50 Ω microstrip line with a tapered microstrip transition to ensure good impedance matching. The calculated impedance bandwidth of the proposed antenna ranges from 3 GHz to 14 GHz with relatively stable radiation patterns. To achieve band-notch characteristic in the 5.0--6.0 GHz WLAN frequency band, two different techniques have been implemented. The first technique uses a C-shaped slot etched in the ground plane while the other one uses another Cshaped slot in the feed line.
A rectangular dielectric resonator antenna (DRA) based on Barium Strontium Titanate --- Cyclic Olefin Copolymer (BST-COC) composite for 2.4 GHz wrist application is designed and characterized. The dielectric properties of the composite with ~57 vol.% BST loading are characterized using microstrip ring resonator structures at 2.45 GHz frequency. The proposed DRA, fixed onto a reverse grounded FR4 laminate, has a very compact size of 19 mm×10 mm×5 mm. The impact of the user's body proximity on the radiation performance of the antenna is studied experimentally. The percentage total efficiency and gain of the antenna deteriorated by about 8.5% and 2 dB due to the proximity of the user's body. The proposed DRA showed better performance than that of resonant type of antennas when close to the user's body.
A fully fabric triangular shaped microstrip patch antenna is proposed for Wireless Broadband (WiBro) communication systems operating in the frequency range of 2.3 GHz to 2.4 GHz with 2.34 GHz as centre frequency. Three highly efficient and flexible antennas, built using three different conductive fabrics and an insulating polyester fabric are evaluated and results reported in this paper. To the best of authors' knowledge, this is the first attempt to utilize textile materials for the development of WiBro antennas.
A helix slow-wave structure (SWS) for a high efficiency Ku-band 140 W space TWT has been designed. Cold circuit parameters of helix SWS like propagation constant and on axis interaction impedance were determined using 3-D electromagnetic field simulators ANSOFT-HFSS and CST-MWS and validated with the experimental results. In-house developed large-signal code SUNRAY-1D was used to design the complete helix SWS in 2-section with sever and taper to achieve desired output power, gain, efficiency, and other linearity parameters such as phase shift, AM/PM factor, I/M components. Simulated RF performance of the Ku-band 140W helix TWT was validated with the experimental results. A close agreement between the simulated and experimental results has been found.
This work presents an ultra-wideband (UWB) low noise amplifier (LNA) with active shunt-feedback technique for wideband and flat gain by using standard 0.18 μm CMOS processes. Different from past resistive shunt-feedback technique, the capacitor supersedes by a transistor in active shunt-feedback technique. The active shunt-feedback provides input matching generating a 50 Ω real part with proper design and achieves flat gain from 2.5 GHz to 12 GHz. The UWB LNA achieved 11.4±0.2 dB gains, 4.5~5.2 dB noise figure (NF), 13.5 mW power consumption at frequency 3.1 GHz to 10.6 GHz, -15 dBm of 1-dB compression point (P1dB), and -3 dBm of input third intercept point (IIP3) at 6 GHz. The chip size including pads is only 0.6×0.5 mm2.
This paper presents a multiband meandered loop antenna for smart phone applications. The proposed antenna which features a meandered folded-loop generates two resonance modes in the LTE/GSM bands. The current distributions of the excited resonance modes are analyzed to investigate the mode characteristic. By using a capacitively coupled feed on the backplane, the impedance bandwidth is broadened to cover LTE/WWAN bands. The simulation performed in this research used a high frequency structure simulator (HFSS) to optimally design the antenna, and a practical structure was constructed for the test. Details of the various antenna parameters are presented and discussed in this paper.
This article describes the design and performances of a rectenna that collects low incident power density levels, at a single ISM-band frequency (f0=2.45 GHz). A new rectenna topology consisting only of an antenna, a matching circuit, a Schottky diode, and a DC filter has been modeled using a global simulation. A circular aperture coupled patch antenna is proposed to suppress the first filter in the rectenna device, and in addition, the losses associated with this filter. The harmonics rejection of the antenna is primarily used to reduce the rectenna size. The implementation of the filter in the antenna structure, combined with a reduction of the rectenna size, gives several advantages in several applications where the size and weight are critical criteria. The maximum energy conversion efficiency in this configuration is 34% and is reached for a load of 9.2 kΩ and a RF collected power of SRF=17μW/cm2(≈-10 dBm RF incident upon the diode).
A microstrip-line-fed Isosceles Trapezoidal Dielectric Resonator Antenna (ITDRA) with a parasitic strip and modified ground plane is introduced. It is proved by simulation and experiment that the antenna's resonant frequency can be lowered and the bandwidth can be increased considerably by introducing a slot and optimizing its position and dimensions in the ground plane. The proposed antenna is a wide band antenna with a 2:1 VSWR bandwidth of 21.5% centered at 2.51GHz and exhibits good radiation characteristics and moderate gain in the entire operating band. The antenna covers important application bands viz. ISM: Bluetooth/WLAN 2.4/Wibree (802.11 b/g/n)/ZigBee, WiBro and DMB. The wideband response in the relatively lower frequency range which includes the above mentioned application bands are not much seen anywhere in literature. Details of the design along with experimental and simulation results are presented and discussed.
Packaging of planar MMICs poses a unique challenge at microwave frequencies as the dimensions of the encapsulating cavity are comparable to wavelength at the operational frequencies. In addition, the effect of ground loops (caused by bond wires exposed to ground over extended length due to gaps between interconnects) deteriorates the situation even further in circuits like MMIC switches requiring high isolation between ports. The ground loops cause reflections thereby deteriorating the insertion loss figure of merit. This paper presents optimization of design of a metal ceramic package used for packaging an SPDT MMIC switch working in the frequency range of 5-6 GHz. The microwave performance of the package was simulated using EM simulation with parameters including cavity dimensions, port placement, gaps between interconnect lines, package feed-thrus and MMIC chip pads. Detailed characterization of the bare package and packaged SPDT MMIC done later shows a good match between the simulated and measured performance. The SPDT MMIC performance degradation was arrested by improvement in the package structure and it showed insertion loss of -1.6dB and input/output (I/O) return losses of ~16dB in the new package as compared to the values of -2.1dB insertion loss and -12dB I/O return losses in the original package. The port-to-port isolation remained unchanged (~40 dB in both cases) as it is governed by the MMIC assembly inside the package rather than the conditions at the I/O interfaces in this kind of large sized packages.
This paper presents the design procedure and implementation of an innovative compact bandpass filter in UHF band by using Composite Right/Left Handed Transmission Line (CRLH-TL) by using parasitic effects of these structures. The CRLH-TL is utilized in order to minimize the overall size of component and reject higher ordered harmonics. The metamaterial transmission line is about one-eighth of a wavelength long and acts as both resonator and inverter which provide capacitive coupling between neighboring sections. To show the validity of design procedure, two prototype bandpass filters were fabricated and tested. We have shown that very good agreement exists between simulation results and those obtained by measurement.
In this paper, a new ultra wideband circular antenna array (UCAA) combining genetic algorithm (GA) to minimize the bit error rate (BER) is proposed. The ultra wideband (UWB) impulse responses of the indoor channel for any transmitter-receiver location are computed by SBR/Image techniques, inverse fast Fourier transform and Hermitian processing. By using the impulse response of multipath channel, the BER performance of the binary pulse amplitude modulation (B-PAM) impulse radio (IR) UWB system with circular antenna array can be calculated. Based on the topography of the antenna and the BER formula, the array pattern synthesis problem can be reformulated into an optimization problem and solved by the genetic algorithm. The novelties of our approach is not only choosing BER as the object function instead of sidelobe level of the antenna pattern, but also considering the antenna feed length effect of each array element. The strong point of the genetic algorithm is that it can find out the solution even if the performance index cannot be formulated by simple equations. Simulation results show that the synthesized antenna array pattern is effective to focus maximum gain to the multiusers.
In this paper, a jamming cancelation approach based on the concept of pulse diversity is proposed to suppress some newer complicated digital radio frequency memory (DRFM) range false targets (RFT). Just repeating the intercepted radar electromagnetic signal, as done in the conventional re-transmitting jammer, is not effective because only one range false target is produced. In contrast, the newer DRFM-based RFT generation methods, especially chopping and interleaving (C&I) and smeared spectrum (SMSP) can yield a multi-lobe filter output by transforming the internal structure of the intercepted radar signal. The presented approach to overcome this challenge is based on the temporal pulse diversity technique, and it does not require parameter estimation of the jamming signal. By transmitting pulses with specific transmission pulse block and the following proper processing, it can cancel out the protruding spikes of the jammer at the price of an acceptable performance loss. Particularly, this method is applicable to broad DRFM repeat jammer in electronic warfare (EW) area.
Non-invasive termite detection avoids damage to the structure under investigation. In this paper, we present the design and simulation of a hybrid radar array, with sub-arrays designed for both close range imaging and wide-area direction of arrival (DOA) processing for non-invasive termite detection. This radar array achieves wide area detection via novel modifications to the Matrix Enhanced Matrix Pencil algorithm and array transformation and achieves high resolution imaging through near field beam-steering from a large random array. The array hardware is designed to be implemented using available technology and low cost electronics.
Obtaining higher efficiency during the development of space Traveling Wave Tubes (TWTs) is always one of the most important goals for scientists. In this paper, a scheme of obtaining the maximum theoretical overall efficiency is explored by optimizing the helix pitch profile of a TWT based on the collectability of spent beam. The collectability of the spent beam was evaluated by the maximum collector efficiency, and this maximum collector efficiency was employed to calculate the maximum theoretical overall efficiency. The energy distribution of the spent beam and the output power of TWTs were calculated by the 3-D large signal Beam-Wave Interaction Simulator (BWIS) of MTSS. The detailed design of a Ku-band helix TWT is described according to three optimization goals (theoretical overall efficiency, theoretical collector efficiency and electronic efficiency). The simulation results indicate that the optimization for high interaction circuit efficiency or collector efficiency by itself is not adequate to obtain maximum overall efficiency. The maximum theoretical overall efficiency of 77% was achieved via the optimization of slow wave structure for theoretical overall efficiency.
This paper shows the design of a fractal patch antenna, which uses a unique fractal geometry known as Pythagoras tree with co-planer waveguide (CPW) feeding. The antenna has been designed for dual band operation at the WLAN/WiMAX (2.4 GHz) and WiMAX (3.5 GHz) for Ultra-Wideband applications. The antenna was simulated using CST Microwave Studio. The fabricated antenna's measurement results were found to be in good agreement with the simulated ones.
A compact wide-slot antenna fed by microstrip-line for wideband operation is proposed and studied. The proposed antenna consists of a microstrip-fed line and a wide rectangular slot with a reverse L-shaped slot. The proposed antenna resonates the 10-dB bandwidth from 2.17 GHz to 6.25 GHz, and these frequency bands cover the standard IEEE 802.11b/g (2.4--2.485 GHz) and IEEE 802.11a (5.15--5.35 GHz, 5.725--5.875 GHz) for WLAN applications and 2.5 GHz (2.5--2.69 GHz), 3.5 GHz (3.3--3.8 GHz) and 5GHz (5.25--5.85 GHz) for WiMAX applications. In order to remove unwanted bands, we used two methods to reject the bands. By inserting a strip in the slot of the broadband antenna, a reject frequency band from 4.13 to 4.95 GHz can be obtained; by etching a U-slot on the the broadband antenna, a reject frequency band from 2.96 to 3.17 GHz can be achieved. The slot antenna with dual band-notched for WiMAX operation has been obtained. Detailed design and experimental results are shown and discussed in this paper.
A new model (EWGM) is presented to predict the resonant frequency of Rectangular Dielectric Resonator Antenna (RDRA) more accurately. Correction factors are introduced to calculate the effective dimensions by considering the effect of relative permittivity and aspect ratios (length/height and width/height) of RDRA. Results obtained from EWGM are compared with previous studies and experimental data to show its accuracy and effectiveness.
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