The possibility of using non-Foster circuit to expand the bandwidth of a monopole antenna is investigated theoretically. Beginning with an inductor-loaded monopole antenna resonating at different frequencies by changing the value of the loaded inductor, we show that a frequency-dependent inductor is needed to enhance the bandwidth of the monopole antenna. The curve for the reactance of the frequency-dependent inductor versus frequency is fitted, which enlightens us to use a non-Foster reactive circuit to realize the frequency-dependent inductor. Based on the above studies, a monople antenna loaded with a non-Foster circuit is presented. Simulated results demonstrate that the input reactance of the loaded antenna becomes stable and approaches zero, which favors the impedance matching and extends the bandwidth to a certain extent. Finally, a passive (Foster) matching circuit is designed to improve the bandwidth further. A 0.69-m monopole antenna with 2.0:1 VSWR in the frequency range 30--150 MHz is designed and investigated.
This paper presents analysis and design of a Gaussian backscatter antenna with ring focus feed. The curvature of main reflector is Gaussian, and the subreflector is a portion of an ellipse. The antenna has axial symmetry. A backscattering technique is used with the main reflector to achieve wide beamwidth. The input parameters of the proposed antenna are derived in closed form. Physical theory of diffraction (PTD) is used to analyze the radiation pattern of the proposed antenna and verified with experimental results. The effects of the support structures on the radiation patterns of the proposed antenna have been investigated experimentally. The proposed antenna can produces high gain and wide beamwidth (coverage angle θ=±65°). This antenna can be used for realizing earth coverage beam in LEO satellite or indoor wireless LAN applications.
A miniaturized microstrip-fed antenna composed of a broadside coupled split ring resonator and an excitation arc-shaped monopole is presented. Numerical and experimental results are presented for an antenna configuration of 1/25 wavelength in diameter (ka~0.126). The antenna size including the ground plane is 60×38.5 mm2 and it is operating at 200 MHz. Its resonant frequency can be tuned over a good range of frequency without changing the antenna size, which can increase its usable bandwidth using reconfigurable antenna techniques.
Waveguide diplexer designs are widely used for telecommunications, space, and terrestrial applications. Although mathematical models and design procedures for waveguide filters are known, diplexer designs still remain complex and time consuming. This paper describes how to obtain an equivalent circuit network model and a complete design of non-contiguous diplexers using a computer-aided approach with a classic Y-junction. Results are satisfactory in terms of reduced design time and performance. Examples including physical dimensions are provided.
A compact stack antenna consisting of square loop resonators, aperture couples, feed line and the perturbation for dual-band and circular polarization (CP) applications is proposed in this paper. This perturbation applies both dual-mode and orthogonal mode effects existing in the square loop resonator to present wide-band and CP characteristics simultaneously. The stack antenna presents the desired bands of 2.46 GHz with bandwidth (BW) = 160 MHz (6.58%) and 5.28 GHz with BW = 450 MHz (8.52%). The circular polarizations for dual-band are demonstrated with axial ratio (AR) spectrum and orthogonal modes. The proposed antenna is successfully simulated and measured with frequency responses, radiation patterns and current distributions.
In this paper, we propose a hybrid optimization approach that combines the Efficient Global Optimization (EGO) algorithm with Taguchi's method. This hybrid optimized algorithm is suited for problems with expensive cost functions. As a Bayesian analysis optimization algorithm, EGO algorithm begins with fitting the Kriging model with n sample points, and finds the (n+1)th point where the expected improvement is maximized to update the model. We employ Taguchi's method in EGO to obtain the (n+1)th point in this paper. A numerical simulation demonstrates that our algorithm has advantage over the original EGO. Finally, we apply this hybrid optimized algorithm to optimize an ultra-wide band (UWB) transverse electromagnetic (TEM) horn antenna and a linear antenna array. Compared to Taguchi's method and the Integer Coded Differential Evolution Strategy, our algorithm converges to the global optimal value more efficiently.
This paper presents a novel third-order cross-coupled rectangular cavity filter by using standard low-temperature co-fired ceramic (LTCC) technology, in which the multilayer substrate integrated waveguide (SIW) is implemented. Particularly, the desired filter has a single finite frequency attenuation pole at j4.0 with asymmetrical frequency selectivity. An experimental band pass filter (BPF) has been fabricated and measured. The insertion loss of the filter is better than 4.2 dB, and the 1 dB bandwidth is about 1 GHz at the center frequency 35.8 GHz. Good agreement is obtained between the simulated and measured S-parameters of the proposed filter. This filter can be used in millimeter wave secondary surveillance radars.
A novel UWB bandpass filter (BPF) based on the composite right/left-handed (CRLH) material and 0° feeding structure is proposed. With multiple unit-cells cascaded, the new section comprises the series interdigital capacitors and the shunt short-circuited stub inductors in the symmetric configuration. The circuit is designed to be unbalanced, a tunable gap between left handed and right handed modes in the β-ω diagram can control out of band performance. With careful design, a bandpass filter with wide rejection band can be achieved. Furthermore, by using the 0° feeding associated structure, two extra transmission zeros are created just outside the intended passband. Finally, a three cells bandpass filter has been designed and fabricated with 1.1 dB insertion loss at the center frequency of 4.2 GHz. Two transmission zeros are located at 2.95 GHz and 6.18 GHz with attenuations of -44.1 dB and -37.3 dB, respectively. Also, a wide rejection band from 5.4 to 9 GHz is obtained.
In this paper, we present a wideband on-chip K-band RF front-end including a transmitter and a receiver for vehicular FMCW radar applications using a 0.18 μm CMOS process. To achieve wideband performance, an RC feedback circuit is applied to the input stage of amplifiers, as well as wideband passive circuits such as Marchand type baluns and Wilkinson type power dividers to the mixer LO port and transmitter output, respectively. The designed chip shows a 3-dB bandwidth of 6 GHz and 4.8 GHz for the receiver and transmitter, respectively. The receiver represents a gain of 18 dB and an input-referred 1 dB compression point of -9 dBm at an RF frequency of 24.15 GHz and an IF frequency of 100 kHz. The transmitter shows a power gain of 8.9 dB and an output power of 6.8 dBm at a frequency of 24.15 GHz. The total chip has a size of 1500 μm x 1270 μm while consuming 71 mA with a supply voltage of 1.8 V. Further, the designed RF front-end chip, also, has been verified by radar performance tests such as the Doppler shift and range detection. The test result for range information shows good agreement with theoretical expectation.
Two recent methods that have been reported in the literature to improve the performance of pyramidal horns are metal baffle loading and the use of epsilon-near-zero metamaterial. In this paper, a comparative study of the two methods is undertaken for the case of Ku- and X-band horns. In addition to the simulation study, a C-band metal baffle loaded horn was fabricated and rigorously characterized. It emerges from the study that E-plane metal baffle loading improves the radiation characteristics of the horn much better than the loading by metamaterial. Furthermore, the baffle loading nearly retains the construction simplicity, weight and cost of the normal pyramidal horn.
Performance of the sensing patch technique for measuring the power accepted at the antenna feed port of active patch antennas has been evaluated at harmonic frequencies. A prototype antenna, including two sensors at appropriate locations, was fabricated and tested at the fundamental and two harmonic frequencies to estimate the power accepted by the antenna, including determination of the sensor calibration factor.
In order to study the information of temperature with stir during microwave heating on fluid, the coupled Maxwell's equations, fluid field equations and heat transport equations were solved using Finite-Element Method (FEM). The microwave heating on fluid was analysed with high power, different dynamic viscosities and relative complex permittivities. The results show that the highest temperature occurs on the interface of the fluid and air. When the fluid is heated under high microwave power, speeding up the stir can improve the uniform of temperature, but if the rotate speed is fast enough, going on speeding up the stir cannot decrease the temperature difference any more. When the value of the imaginary part of relative complex permittivity which accounts for dielectric losses or the dynamic viscosity increases, the temperature in the water rises very quickly, and the temperature difference is very large even if the rotate speed is fast enough.
A novel method of using bypass coupling SICC resonator to generate transmission zeros in filter stopband to improve stopband attenuation is presented. A SIW quasi-elliptic function filter for Satellite Communication application with bypass coupling SICC resonator is designed and fabricated to validate the method. The results show that the method is effective on improving the filter stopband performance.
Recent studies have shown that the dielectric properties of normal breast tissue vary considerably. This dielectric heterogeneity may mean that the identification of tumours using Ultra Wideband Radar imaging alone may be quite difficult. Significantly, since the dielectric properties of benign tissue were shown to overlap with those of malignant, breast tumour classification using traditional UWB Radar imaging algorithms could be very problematic. Rather than simply examining the dielectric properties of scatterers within the breast, other features of scatterers must be used for classification. Radar Target Signatures have been previously used to classify tumours due to the significant difference in size, shape and surface texture between benign and malignant tumours. This paper investigates Spiking Neural Networks (SNNs) applied as a novel tumour classification method. This paper will describe the creation of 3D tumour models, the generation of representative backscatter, the application of a feature extraction method and the use of SNNs to classify tumours as either benign or malignant. The performance of the SNN classifier is shown to outperform existing UWB Radar classification algorithms.
This paper presents the theory, properties, types, and applications of high impedance wires (HIWs). The effective permeability of a transmission line that consists of an HIW and a second conductor has a resonating behavior. Consequently, slow-wave and stop-band regions appear in the dispersion relation. In the slow wave regions, a new implementation for dual-mode filter is presented. The proposed filter size is reduced by 33%. In the stop band region, a new application is presented; dual-band balun where the common mode is rejected by the HIW. The novel design has a total area of 4 x 2.4 cm2 and exhibits reliable performances at 2.75 GHz with a 40% bandwidth (2.2--3.3 GHz) and at 4.75 GHz with a 15% bandwidth (4.4--5.1 GHz) with an amplitude imbalance less than 1 dB, a return loss better than 13 dB, and phase imbalance less than 5°. Theoretical expectations were confirmed by EM simulations and measurements.
The structural and microwave properties of (y) Ni1-xCdxFe2O4 and (1-y) Ba0.8Sr0.2TiO3 (x = 0.2, 0.4, 0.6 and y = 0.15, 0.30 and 0.45) composites synthesized by self propagating auto combustion route was studied. X-ray diffraction patterns reveal this method can produce two phases simultaneously. The porosity increases with increase in ferrite content in the composite. The SEM morphologies show the growth of cadmium substituted nickel ferrite grains which are well dispersed in barium strontium titanate (BST) matrix. The composite material shows microwave absorption of about 0.575 in a broad band from 8-12GHz. The permittivity varied from 7 to around 43 with increase in ferrite content .The microwave conductivity measurements reveal the loss of polaron conduction which supports the dielectric loss in the microwave region.
In this paper, a time domain analysis for ultra-wideband short pulse radiation from wire monopole antennas and their arrays is presented. The pulse travels along the monopole antenna and reflects from the open end; during the pulse reflection, the pulse gets compressed. The analysis presented in this paper accounts for the pulse compression and the radiated pulse is compared with the measured pulse. Measured energy patterns for different pulse excitations of the monopole and monopole arrays are presented and compared with theoretical patterns.
A fully integrated 5.5 GHz high-linearity low noise amplifier (LNA) using post-linearization technique, implemented in a 0.18 μm RF CMOS technology, is demonstrated. The proposed technique adopts an additional folded diode with a parallel RC circuit as an intermodulation distortion (IMD) sinker. The proposed LNA not only achieves high linearity, but also minimizes the degradation of gain, noise figure (NF) and power consumption. The LNA achieves an input third-order intercept point (IIP3) of +8.33 dBm, a power gain of 10.02 dB, and a NF of 3.05 dB at 5.5 GHz biased at 6 mA from a 1.8 V power supply.
In this paper, a novel broadband monopole antenna with an extended rectangular shaped slot based on coplanar waveguide (CPW)-fed is designed and presented. The antenna composed of a planar rectangular patch element embedded with a slots, capable of generating two separate resonant modes with good impedance matching. The parametric study is performed to understand the characteristics of the proposed antenna. To verify the simulated design concept, a prototype antenna is designed and fabricated on the FR4 substrate, and characterized experimentally. The overall size of the antenna is 35.24 mm×26.4 mm×1.6 mm including the finite ground CPW feeding mechanism and total volume of the antenna is 1.49 cm3. The antenna operates in broad frequency bands from 3.424 GHz to 6.274 GHz covering wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) bands. The maximum gain of the proposed antenna is 5.51 dBi at 4.78 GHz frequency band. The proposed antenna‟s radiation characteristics are also observed.
With the advent of DVB-T in most European countries, the European Union has decided to end all analogue television broadcasts in its member countries until 2012. This analogue switch-off, as well as the increased spectral efficiency of the DVB-T protocol will create a surplus of spectrum in the UHF band, part of which is to be used by mobile communications systems. In order for this "digital dividend" to be shared efficiently, the coexistence and interference parameters between DVB-T and other services (designated as IMT-Advanced by the International Telecommunications Union) have to be studied. In this paper a generic 5 MHz interfering signal is broadcasted in close proximity to a stationary DVB-T receiver. Various DVB-T parameters are then measured and analyzed for different frequency values and power levels of the interfering signal.