In high dynamic environment, due to the rapid relative movement between receiver and transmitter, the DOA (Direction of Arrival) of signals will change even between two consecutive snapshots. Thus, covariance-based DOA estimation algorithms are ineffective. Compressive sensing algorithms, as a kind of novel DOA estimation algorithms, are still effective with only one snapshot. At the same time, it is noted that the DOA changing is limited by relative moving speed and distance between receiver and transmitter. In this paper, a DOA tracking algorithm based on weighted L1 minimization is proposed which utilizing the DOA changing scope between two consecutive snapshots as a prior to improve the tracking performance. Different from other multiple snapshots compressive sensing algorithms which assumed fixed DOA among multiple consecutive snapshots, the proposed algorithm takes into account the DOA changing among different snapshots. The simulation results demonstrate the advantages of the proposed algorithm.
This paper proposes a method to design an even-order symmetric bandpass filter with Chebyshev response. The alternative J inverters and λ/4 short-ended resonators are used in the filter design. It is well known that a conventional even-order Chebyshev bandpass filter prototype can be designed by using J-inverters. However, to achieve the Chebyshev response, a problem is that the output admittance YL is unequal to the input admittance Y0 since normalized gn+1 is not equal to the g0. But for the symmetrical structure, an additional impedance transform can be installed at the output port to solve this problem, thus the network of even-order symmetric bandpass filter with a Chebyshev response should be modified with new J-inverters. In this work, all J-inverters of the symmetric bandpass filter with Chebyshev response are extracted and described as curves to determine the circuit dimensions of the proposed structure. Two even-order Chebyshev bandpass filters with the second- and fourth-order are designed with the proposed method as its application examples. Finally, the fourth-order filter is fabricated and measured at center frequency of 2.5 GHz with the fractional bandwidth 25%. The measured result is in good agreement with the simulated one.
A new structure of coupled-fed loop antenna connected with two branch radiators for eight-band LTE/WWAN (LTE700/GSM850/900/1800/1900/UMTS/LTE2300/2500) operation in the ultra-thin laptop computer is presented. The two branch strips of the antenna are efficient radiators and contributing multi-resonant modes to greatly enhance the bandwidth of the antenna. The proposed antenna on the top shielding metal wall of the laptop display, with a planar and compact size of 12.5×70×0.8 mm3, is suitable to be embedded inside the casing of the laptop computer. The proposed antenna is fabricated and tested, and good radiation performances are obtained. Compared with the existing published antennas, the volume of the planar antenna is quite small.
Primary user (PU) signal detection is critical for cognitive radio networks as it allows a secondary user to find spectrum holes for opportunistic reuse. Eigenvalue based detection has many advantages, such as it does not require knowledge on primary user signal or noise power level. However, most of the work on eigenvalue based detection methods presented in the literature rely on multiple sensing nodes or receiving antennas so that they cannot be directly applied to single antenna systems. In this paper, an effective PU signal detection method based on eigenvalue is proposed for a cognitive user equipped with a single receiving antenna. The proposed method utilizes the temporal smoothing technique to form a virtual multi-antenna structure. The maximum and minimum eigenvalues of the covariance matrix obtained by the virtual multi-antenna structure are used to detect PU signal. Compared with the previous work, the presented method offers a number of advantages over other recently proposed algorithms. Firstly, the presented approach makes use of power method to calculate the maximum and minimum eigenvalues, it has lower computational complexity since the eigenvalue decomposition processing is avoided. Secondly, it can reduce system overhead since single antenna is used instead of multiple antennas or sensing nodes. Finally, simulation results show that performance of the proposed method is close to that of maximum-minimum eigenvalue detection using multiple antennas.
In this paper, transmitter polarization optimization is firstly proposed to improve the accuracy of azimuth-elevation arrival angles estimation within MIMO electromagnetic vector-sensor array (EMVA). Minimizing of Cramer-Rao bound is used as cost function for the optimal design of transmitting signal polarization. Computer simulation results verify that the optimal polarization design provides increased estimation accuracy of direction finding in MIMO-EMVA, compared with that of using fixed polarization of transmitting signal. Moreover, the optimal polarization design retains all advantages of using fixed polarization of transmitting signal for MIMO-EMVA direction finding.
This paper discusses a conducted emission measurement of a cell phone integrated circuit. The industry standard measurement method is used to compare the measurement result to the defined limit line. A data analysis method-short time fast Fourier transform (STFFT) is presented to help to analyze the result. The data consistency and repeatability is also analyzed.
This paper presents a novel design of a circular ring defected ground structure (DGS) antenna for bandwidth enhancement using fuzzy logic approach. The ground plane of the antenna is defected by introducing circular ring sector type of defect beneath the circular ring patch. The position of the defect in the ground plane to attain the highest return loss and corresponding frequency is determined by using Fuzzy Interface System (FIS). The antenna resonates in X-band showing wideband characteristics with improved gain and reduced cross polar radiations. The return loss and analogous frequency obtained from simulated results and fuzzy system are compared and are in good agreement. The return loss and input impedance is measured experimentally and compared with the simulated results. Parameters like impedance bandwidth, VSWR and antenna gain are likewise calculated and discussed. The simulated results for the radiation pattern of the proposed design with polarization (Co-polar and Cross-polar) are also presented. The simulated impedance bandwidth of about 1.33 GHz (1.2 GHz experimentally) in X-band is obtained with a gain of 6.43 dB and also cross-polarized radiations have an isolation of 20 dB.
A simple wideband antenna with parasitic element is proposed in this paper. The printed antenna is comprised of an L-shape monopole and a parasitic element. By optimizing geometrical parameters of the parasitic element structure, a good impedance bandwidth which covers DVB (470 MHz~702 MHz) for return loss being higher than 5 dB and LTE/700(704 MHz~787 MHz), GSM850/900 (824 MHz~894 MHz/880 MHz~960 MHz) for return loss being higher than 10 dB is achieved. A fabricated antenna has a dimension of 150 mm×56 mm. The measured and simulated efficiency, gain and radiation pattern which is quasi omni-directional in the yoz plane make it to be a good candidate of mobile communicational terminals.
A novel compact dielectric loaded Exponentially Tapered Slot (ETS) antenna using Substrate Integrated Waveguide (SIW) technology is presented in this paper for Millimeter (Mm) wave wireless communication applications. The dielectric loaded ETS antenna and compact SIW feed are fabricated on a single substrate. The compact SIW feeding structure results in a considerable reduction in size and eliminates the unwanted radiations from feed. The proposed antenna is designed, fabricated, and investigated at 60 GHz. Furthermore, the proposed antenna design is simulated using electromagnetic software CST Microwave Studio and the comparison is made with Ansys HFSS to validate the design procedure. The measurement results are compared with simulated results.
This paper presents a new design for wide slot circularly polarized (CP) antenna (WSCPA). The proposed design possesses much larger return loss bandwidths and CP bandwidths than existing WSCPA. The main features of the antenna structure include a modified CPW feeding line and a wide and symmetric ellipse-aperture along the diagonal axis. By properly tuning axial ratio of ellipse-aperture and parameters of feeding line, wideband return loss and CP radiations can be achieved. The measured bandwidths of 10-dB return loss and 3-dB axial ratio (AR) are as large as 112.5% (2.1-7.5 GHz) and 109% (2.3-7.8 GHz), respectively. The improvement process of the AR and S11 properties is completely presented and discussed in this paper.
This paper presents a neural network based technique for the analysis of various stacked patch antennas, those can be applied for satellite and wireless local area network (WLAN) applications. In order to show the diversity of artificial neural network (ANN) modeling technique, two different trained neural networks were developed with different number of antenna geometrical parameters as inputs. These trained networks locate the operational resonance frequencies with their bands for stacked patch antennas (SPA) operating in the X-Ku (8 GHz-18 GHz) bands and WLAN bands (2 GHz-6 GHz). These frequency bands are useful for satellite communication and indoor wireless communication applications respectively. First ANN model takes design (geometrical) parameters of antenna like lower patch dimension, upper patch dimension, and height of air gap, as a input, whereas other NN model includes feed point location also as a input. The validity of the network is tested with the simulations results obtained from the full-wave Method of Moment (MoM) based IE3D and few experimental results obtained in the laboratory.
An LTE smart mobile antenna with multiband operation is proposed to work in the bands of LTE, GSM, DCS, PCS, PHS, UMTS, Bluetooth, and WLAN. Compared with those reported in the literature, the proposed antenna features a simple and straightforward design procedure, which is composed of three easy steps. Firstly, A three-dimensional meandering monopole antenna is constructed along the edge of a rectangular PCB to act as the main radiator, resulting in the bands of LTE, DCS, and PCS, PHS, and UMTS. Secondly, a shorted stub is fabricated to excite the GSM band, and also to improve the impedance matching in the bands of LTE and GSM. Finally, the second shorted stub is added to radiate in the band of WLAN. The numerical results show that the -6 dB return-loss bandwidths are from 0.7 GHz to 0.985 GHz (0.285 GHz, 34%) in the lower band and from 1.64 GHz to 2.535 GHz (0.895 GHz, 43%) in the higher band. The corresponding measured data are from 0.7 GHz to 1.03 GHz (0.33 GHz, 38%) in the lower band and from 1.64 GHz to 2.55 GHz (0.91 GHz, 43%) in the higher band. The measured antenna gains are about 2 to 3 dBi in the lower and higher bands, respectively.
In this paper, a novel approach was used to design two-layer stacked high gain microstrip antenna array with improved bandwidth and high aperture efficiency. Cross Snowflake fractal microstrip patches were employed as radiation elements. Varieties of antenna arrays with different fractal iterations were optimized by using the Genetic Algorithm (GA) associated with 3D full-wave Finite Element Method (FEM) in order to investigate the influence of the Cross Snowflake fractal radiators. As compared with the conventional square patches, the Cross Snowflake fractal configuration provides extremely high flexibility to achieve a wideband performance and maintains higher aperture efficiency at operating frequency band. A prototype antenna with 2 x 2 Cross Snowflake radiators was fabricated and measured. Both simulated and measured results show that the proposed antenna has some promising performances to be more specially, the measured impedance bandwidth is 22.9% (from 5.18 GHz to 6.52 GHz) when S11<10 dB; the simulated gain is 12.0 dBi and its corresponding aperture efficiency is up to 87.4% at the working frequency 5.8 GHz.
This paper presents a new rectangle-slot antenna for ultra wideband applications with 3.5/5.5 GHz dual stop-band characteristics. The antenna contains a simple square radiating patch and a rectangle-slot ground plane, which provides a wide bandwidth from 2.6 GHz up to 14.1 GHz. In order to obtain dual stop-band properties at 3.5 and 5.5 GHz, a rectangularshaped slot is etched off the ground plane, and a strip line ended up a shorting pin is applied, respectively. The antenna is simple in configuration and has a compact dimension of 20×22 mm2. The proposed antenna is designed, simulated and fabricated. The measured results exhibit a acceptable agreement with the simulated data. The antenna provides nearly omnidirectional radiation patterns, relatively flat gain over the entire UWB frequency excluding the two stop bands.
A radiation pattern synthesis technique for large planar arrays with active element pattern (AEP) method and fine-grained parallel micro-genetic algorithm (FGPMGA) is presented. Based on the AEP method, the mutual coupling between array elements can be taken into account. Analysis problems of large rectangular and triangular grid planar arrays are divided into small linear array problems. And for a multiple concentric circular ring array, we only need to obtain one-sixth of all AEPs. So computational cost is greatly reduced. Large planar arrays with low side lobe level (SLL) can be achieved via optimizing the excitation amplitudes and phases. In order to reduce the global optimization time, the FGPMGA is used. This technique is applied to design 256-element rectangular grid, 200-element triangular grid and 4-circle 60-element concentric circular ring E-shaped patch antenna arrays. The radiation patterns calculated by the AEP method show good agreements with those by using CST Microwave Studio.
This paper presents a high-selectivity dual-band bandpass filter with independently-tunable passband frequencies. A tap-coupled structure is utilized to feed the two resonators at lower passband and a coupling structure is used to feed the two resonators at the upper passband. Two pairs of varactor-loaded resonators operating within two different frequency ranges, allow the independent passband frequency tuning. Using this configuration, it is convenient to tune the center frequency of each passband, while the responses of the other passband remain unaltered. Source-load coupling is realized to generate transmission zeros, resulting in high skirt-selectivity. The transmission zeros move synchronously with the passbands, ensuring sharp roll-off rate for all tuning states. To verify the proposed idea, a demonstration microstrip tunable bandpass filter is implemented. The simulated and measured results are presented.
A novel printed monopole antenna covering 2.4-2.484 GHz (Bluetooth), 2.5-2.69 GHz (IMT-E) and 3.1-10.6 GHz (UWB) frequency bands is presented. The entire frequency bands are obtained by a modified U-shaped radiator and a modified ground plane. To prevent possible interference between UWB systems and other existing wireless systems such as WLAN and WiMAX, a SCRLH resonator structure is placed next to the feed line. Characteristics of the Bluetooth and IMT-E bands are further enhanced by two quarter-wavelength strips added on each side of the radiator. The proposed antenna can be easily printed on a 1.6-mm-thick FR4 substrate with dimensions of 30 × 41 mm2. Simulation and experimental results show that the antenna yields an impedance bandwidth of 2.3-2.8 and 3-12 GHz with -10 dB reflection coefficient, except for the dual notched bands of 3.2-3.6 for WiMAX and 4.9-6.1 GHz for WLAN. The electrical characteristics in frequency and time domain show suitability of this antenna for use in UWB systems.
Bionics principle is applied to frequency selective surface (FSS) design in this paper. To authenticate the method, a novel bionic and miniaturized FSS is proposed by use of a model of alternate phyllotaxis. The simulated and measured results show that the proposed FSS has a much smaller size and maintains other FSS-related performances. To study the applications of the novel bionic FSS in practice, it is used for the ground plane of an antenna array to reduce the antenna radar cross section (RCS). Compared to a reference antenna, the antenna with bionic FSS has lower RCS and favorable radiation performance. Hence, applying bionics principle to FSS design and antenna RCS reduction is proved feasible, which will serve as a good candidate for the future design of FSS and antennas with or without a requirement of RCS control.
This paper presents a new type of wideband bandpass filter (BPF) with quasi-elliptic frequency response by using proposed stubs loaded anti-parallel coupled-line. With different loads, the proposed stubs loaded anti-parallel coupled-line has different numbers of transmission zeros (TZs). These TZs are symmetrical along the designing frequency f0. By using a quarter-wavelength parallel coupled-line to connect two proposed stubs loaded anti-parallel coupled-line, three wideband BPFs centered at f0 = 1.575 GHz with quasi-elliptic frequency response are successfully designed. Good agreements between the simulations and measurements can be observed. The measured results also exhibits that the fabricated BPFs have the merits of low in-band insertion loss, good in-band return loss, sharp passband selectivity and high out-of-band rejection.
In recent years, Artificial Neural networks (ANNs) have been intensively employed to build smart model of microwave devices. In this paper a characterization of lossy SIW resonators by means of Multilayer Perceptron Neural Networks (MLPNNs) on Graphics Processing Unit (GPU), is presented. Once properly selected and trained, a MLPNN can evaluate the lossy SIW resonator's resonant frequency fr and the pertaining quality factor Q at a shorter time than the full-wave rigorous model. In this way, fast parametric models of SIWstructures to employ for the design and optimization of microwave devices, exploiting the computational power of GPUs, can be obtained.