In this paper, two kinds of dual-band bandpass filter (BPF) based on a single square ring resonator are presented, which are realized by loading capacitance or inductive stubs, respectively. Even-odd-mode analysis is applied to explain their model characteristics. One filter is implemented by loading a pair of capacitance stubs, and both in-band couplings can be tuned in a reasonable range. Another filter is completed by loading a pair of inductive stubs, and the first and second passband center frequencies can be controlled independently. For demonstration, two filters operating at 2.45/5.25 GHz and 2.4/5.25 GHz are designed and fabricated. The simulated and measured results show good agreements.
This paper presents method of moments based analysis of high-gain broad-band waveguide broad-wall longitudinal slot array antenna. Initially a basic two-element slot array antenna has been analyzed, and corresponding scattering parameter data have been obtained. The theoretical data have been compared with experimental data and Ansoft HFSS's simulated data to validate the proposed method. The excellent agreement obtained between the results validates the analysis. After validating the methodology attempts have been made to design a broad-band high-gain slot array antenna. An 18-element slot array antenna has been designed, fabricated and tested. The fabricated antenna provides a high gain over large band width.
A new method for the theoretical analysis of the third-order intermodulation distortion (IM3) in barium strontium titanate (BST) thin film interdigital capacitors (IDCs) on r-plane sapphire substrates is presented. Two circuit topologies-the dual and series dual BST varactor circuit-are proposed and their theoretical models along with simulated and measured results are presented. Low IM3 is demonstrated and experimentally verified. By proper selective biasing, very low nulls are observed in both dual and series dual BST varactor circuit topologies which indicate minimum distortion. The measured first nulls are achieved at ±13 V and ± 20 V for the dual and series dual topologies respectively. These results demonstrate the potential of incorporating these highly linear BST varactors in silicon on sapphire (SoS) applications.
In this paper, design of broadband dual polarized electromagnetically coupled antenna array is proposed to achieve high isolation between two orthogonal ports. A dual polarized electromagnetically coupled microstrip antenna is designed with a suspended radiating element placed in inverted microstrip configuration and excited by two orthogonal microstrip line feeds to achieve broad bandwidth and high isolation. The antenna is designed for 5.8 GHz frequency band. In order to optimize the design, detailed parametric analysis of the antenna is presented. The antenna design is extended to 2×2 antenna array, with top layer radiating elements electromagnetically coupled to the open microstrip feed line network. The 6×6 antenna array is designed using 2×2 sub arrays with power divider network. The power divider network is integrated on the back side of the feed network to feed 2×2 antenna sub arrays. The 6×6 antenna array achieves VSWR < 2 bandwidth of 26% for Port 1 and 28% for Port 2. The 6×6 antenna array has measured gain of 22 dBi at 5.8 GHz with isolation between two orthogonal ports > 30 dB.
In this work, a library of 3D lumped components completely embedded in the thinnest, multilayer LCP (M-LCP) stack- up with four metallization layers and 100 μm of total thickness, is reported for the first time. A vertically and horizontally interdigitated capacitor, realized in this stack-up, provides higher self resonant frequency as compared to a similarly sized conventional parallel plate capacitor. Based on the above mentioned library, a miniaturized bandpass filter is presented for the GPS application. It utilizes mutually coupled inductors and is the smallest reported in the literature with a size of (0.035×0.028×0.00089)λg. Finally, the same filter realized in a competing ceramic technology (LTCC) is compared in performance with the ultra-thin M-LCP design. The M-LCP module presented in this work is inherently exible and offers great potential for wearable and conformal applications.
We report the numerical and experimental investigation of a highly directive Fabry-Perot (FP) cavity antenna based on a metamaterial, operating in the microwave regime. Numerical simulations using finite element method and reflection-transmission microwave measurements have been performed and a good quantitative agreement has been observed. Measured return losses and radiations patterns done in an anechoic chamber agree very well with the simulated ones. The potential application of the proposed FP cavity antenna in a non-contact breathing sensor is proposed and evaluated. Experimental record and frequency spectrum for respiratory movements of human-being (voluntary under test) are presented. The low cost and simple fabrication process of the proposed FP cavity antenna make it very promising for its integration in modern telecommunication systems.
A novel model for the outage probability prediction in time diversity satellite communication (SatCom) systems operating above 10 GHz is proposed. Due to the migration of operating frequency at Ka band and above, atmospheric phenomena affect the signal. Rain is the dominant fading mechanism. Diversity techniques are the probable solution of the compensation of rain fading. Among the diversity techniques, time diversity has been identified as an efficient and cost effective technique. A method for the prediction of outage performance and diversity gain of time diversity SatCom systems is presented based on the physical assumptions of a well accepted dynamic stochastic model. The new method is tested against with simulated and experimental data with encouraging results.
This paper describes the design, assembly and field testing of a LHCP (Left Hand Circularly Polarized) high gain helical antenna. The antenna is to be utilized for the reception of reflected Global Positioning System (GPS) signals, which are correlated with the direct signals to form an image of the area of interest. Thus the antenna forms a constituent element of a remote imaging system. Owing to the low power of the reflected GPS signals the major design parameter was obviously high gain, while maintaining the polarization integrity of reflected GPS signals. *
To study effective anti-chaff jamming methods, this paper investigates the echo characteristics of the vessel and the chaff for missile-borne wideband coherent radars. Firstly, the echo model of the missile-borne wideband coherent LFM pulses radar is built, and the range-Doppler image of the echoes is derived. Based on the measured data, the differences of the echoes between the vessel and the chaff are analyzed. Then in terms of the spread feature and the energy evenness of the range-Doppler image, two features of the radar echoes are proposed to distinguish the vessel and chaff. Finally, statistical distributions of the two features are investigated, and we find that the proposed features can be used for chaff jamming identification and suppression.
In this document, a simple and efficacious method to estimate the shielding effectiveness of an electrically large enclosure (SEe) made with pierced metallic plate is shown under uniform and isotropic field conditions, which are produced in a reverberation chamber (RC) where the field is well stirred. The estimate is made by the calculation of the transmission cross sections (TCSs) of the walls of an enclosure and absorption cross sections (ACSs) of the inner losses. TCSs and ACSs are connected to the shielding effectiveness (SE) of the walls and inner losses, respectively; the latter are also connected to the reflectivity of the enclosure internal walls. The comparison with measurements made in an RC matches enough. It shows that the method shown here is sound. Moreover, the results support a recent model that connects SEe to SE by the reflectivity of the enclosure internal walls, and show still further that unloaded electrically large enclosures with distributed apertures are not very efficacious.
In this article, a novel simplified dual-composite right/left-handed transmission line (S-DCRLH-TL) is proposed according to the theory of dual-composite right/left-handed transmission line. The electromagnetic characteristics of S-D-CRLH-TL are analyzed by simulator, and the results indicate that the proposed structure has two narrow stopbands; they can be controlled by changing the geometry parameters of the structure. Then, a bandpass filter with dual notched bands is designed by using the unit cell of S-D-CRLH-TL, and the designed filter is simulated, fabricated and measured, the measured and simulated results are in good agreement with each other, showing that the two notched bands centered at 3.60 GHz and 5.50 GHz, and the bandwidths are 9.7% and 7.3%. This designed filter can avoid the interference to UWB communication system effectively, which comes from the signals of WiMAX and WLAN. Besides, in comparison with the other bandpass filter with notched bands, the designed filter has good electromagnetic performances.
In this paper, a 4 × 4 indoor Multiple-Input Multiple-Output Ultra-Wideband (MIMO-UWB) measurement campaign in the 2-5 GHz bandwidth is presented. The main contribution of this work is the impact of radio-wave polarization as well as the effect of frequency dependence on the capacity of MIMO-UWB systems working in an office environment. To accomplish this, the capacityfor different polarizations is analyzed under two different assumptions: constant or variable Signalto-Noise Ratio.
A compact stacked bidirectional antenna is presented for dual-polarized 2.4 GHz WLAN applications in this paper. The antenna consists of an orthogonal coupling feed driver and stacked director array, with the overall size 50×50×160 mm3. Dual-polarization is excited by the orthogonal coupling line, and the director array contributes to the bidirectional radiation pattern. Both the coupling feed driver and directors are printed on FR4 substrate and supported by plastic pillars. The measured bandwidth of the two ports are 2.33-2.62 GHz (11.8%) and 2.32-2.64 GHz (13%) under the condition of VSWR less than 2. The isolation between two ports are lower than -20 dB. The peak gains along one radiation direction are 9.65 dBi and 9.30 dBi for each port, with highly symmetric bidirectional beam pattern. The proposed antenna is compact and stable, and suitable for bidirectional 2.4 GHz WLAN applications.
In this paper, ultra-wideband characteristics of a hexagonal wide slot antenna with dual band-notched property have been proposed and experimentally investigated. By etching a pair of L-shaped slots and embedding a pair of parallel strip conductors, dual band-notched properties in WiMAX/C-Band satellite application and WLAN band are achieved respectively. Good impedance matching is obtained over a wide band by designing the feed structure with a 50 Ω microstripline loaded by a tuning stub. The stub is proposed to have one hexagonal section and one straight section. The proposed antenna operates over 2.0 GHz-10.7 GHz range, for VSWR≤2,excluding the two rejection bands from 3.4 GHz to 4.3 GHz and 5.12 GHz to 6.4 GHz having rejection level VSWR of 7.84 and 6.5 respectively. The impedance bandwidth of the antenna is 5.35:1. The proposed ultra-wideband structure also exhibits constant group delay, satisfactory gain and high radiation efficiency in the pass band.
Specific emitter identification (SEI) is the technique which identifies the individual emitter based on the RF fingerprint of signal. Most existing SEI techniques based on the transient RF fingerprint are sensitive to noise and need different variables for transient detection and RF fingerprint extraction. This paper proposes a novel SEI technique for the common digital modulation signals, which is robust to Gaussian noise and can avoid the problem that different variables are needed for transient detection and RF fingerprint extraction. This makes the technique more practical. The technique works based on the signal's energy trajectory acquired by the fourth order cumulants. A relative smoothness measure detector is used to detect the starting point and endpoint of the transient signal. The polynomial fitting coefficients of the energy trajectory and transient duration form the RF fingerprint. The principal component analysis (PCA) technique is used to reduce the feature vector's dimension, and a support vector machine (SVM) classifier is used for classification. The signals captured from eight mobile phones are used to test the performance of the technique, and the experimental results demonstrate that it has good performance even at low SNR levels.
We hybridize vector Finite Element Method (FEM) and a Modified Multimodal Variational Formulation (MMVF) to the accurate and fast design of complex isotropic rectangular filters. The MMVF is applied to the full-wave description in the rectangular waveguides while the FEM characterizes waves in the arbitrarily shaped discontinuities. The proposed hybrid method is applied to the full-wave analysis of circuits with great practical interest (i.e., cross-shaped iris and multimode filters), thus improving CPU time and memory storage against several full-wave FEM based Computer Aided Design (CAD) tools (i. e. HFSS High Frequency Structural Simulator). The performances of the proposed hybrid method are validated with experimental results and HFSS simulations.
An ultra-wideband (UWB) planar monopole antenna integrated with a narrow-band (NB) cylindrical dielectric resonator antenna (DRA) is presented. The proposed antenna consists of a UWB monopole excited by a coplanar waveguide (CPW) transmission line, acting as a ground for a DRA excited by a slot. The mode HEM11δ is excited in the NB DRA. To validate the concept of integration, an antenna is fabricated and measured. The measured results demonstrate that the UWB antenna provides a 2:1 voltage standing wave ratio (VSWR) bandwidth for 3.05-11 GHz, integrated with a dual-band NB antenna. Moreover, the two ports have the same polarization and a reasonable isolation (less than -10 dB) between each other. This is a promising candidate for applications in cognitive radio, where the UWB antenna can be used for spectrum sensing and the NB antenna for communication operation.
In this paper, an alternative technique for estimating the Rice factor, K, is applied to the phase of electromagnetic field within a reverberating chamber (RC) for classifying the fading depth on the coherent components in the emulated line-of-sight (LOS) environments. The estimator is time-effective and general, and can be applied for any angle of arrival (AoA) of the received field and for any time varying propagation channel as a complementary method to the classical estimators for evaluating K above all when small but consistent coherent components are present. Measurements accomplished at the RC of the Università di Napoli Parthenope (formerly Istituto Universitario Navale, IUN) confirm the goodness of the proposed technique.
A new microstrip ultra-wideband (UWB) bandpass filter (BPF) with triple-notched bands is presented in this paper. The circuit topology and its corresponding electrical parameters of the initial microstrip UWB BPF are desired by a variation of genetic algorithm (VGA). Then, triple-notched bands inside the UWB passband are implemented by coupling a square ring short stub loaded resonator (SRSSLR) to the main transmission line of the initial microstrip UWB BPF. The triple-notched bands can be easily generated and set at any desired frequencies by varying the designed parameters of SRSSLR. For verification, a microstrip UWB BPF with triple-notched bands respectively centered at frequencies of 4.3 GHz, 5.8 GHz, and 8.1 GHz is designed and fabricated. Simulated and experimental results are in good agreement.
We propose a technique with clear guidelines to design a compact planar Wilkinson power divider (WPD) for ultra-wideband (UWB) applications. The design procedure is accomplished by replacing the uniform transmission lines in each arm of the conventional power divider with varyingimpedance profiles governed by a truncated Fourier series. Such non-uniform transmission lines (NTLs) are obtained through the even mode analysis, whereas three isolation resistors are optimized in the odd mode circuit to achieve proper isolation and output ports matching over the frequency range of interest. For verification purposes, an in-phase equal split WPD is designed, simulated, and measured. Simulation and measurement results show that the input and output ports matching as well as the isolation are below -10 dB, whereas the transmission parameters are in the range of (-3.2 dB, -4.2 dB) across the 3.1 GHz-10.6 GHz band.