In this paper, optically transparent ultra-wideband (UWB) monopole antennas in S-band and C-band are presented, compared and discussed. Three transparent UWB antennas elaborated from the AgGL (Silver Grid Layer) material with various levels of transparency (54.5%, 73.4% and 80.3%) and of sheet resistances 0.018 Ω/sq, 0.022 Ω/sq and 0.052 Ω/sq, respectively are tested. The radiofrequency measurements show performances very close to those of a light reflecting reference antenna made of a continuous silver/titanium bilayer (0.0026 Ω/sq sheet resistance). Conversely, the fourth transparent antenna, made of usual transparent conducting oxide/metal multilayer presents significant ohmic losses and weak radiofrequency performances. The gains of the UWB AgGL antennas are similar to that of the reference antenna (~6 dBi max.). Whereas the gain of the transparent multilayer antenna always stays ~2 dB lower than that of the reference. This work demonstrates the relevance of AgGL coating in the fabrication of transparent UWB antennas with high radiation efficiency.
Fast and efficient spectrum sensing is vital for multi-radio multi-channel cognitive radio (CR) networks where unlicensed secondary users (SUs) have to sense and opportunistically transmit on multiple spectrum bands without causing any harmful interference to the licensed primary users (PUs) of those spectrum bands. Accordingly, this paper presents a smart, practical and efficient wideband spectrum sensing scheme based on an optimal sensing stop policy that aims to optimize SU throughput while adhering to the PU interference constraints. Unlike existing work, this scheme is smart because in determining the best time for the multi-transmitter SU to stop sensing and start data transmission based on the channels that have been sensed idle, this scheme explicitly takes into consideration the number of transmitters on the SU; so-called N-transmitters constrained SU. Further, we formulate and solve the optimal sensing stopping problem. The numerical and simulation results presented verify the efficiency of the proposed sensing scheme.
A novel Ultra Wideband (UWB) antenna on double substrates crossing is presented in this paper. Based on conical antenna and microstrip patch UWB antenna, the proposed antenna is omni-directional, band-notched and easy to be fabricated. It operates from 2.6 GHz to 12 GHz with low Voltage Standing Wave Ratio (VSWR<2), excluding a notch-band of 5.8 GHz. Except for good performance of VSWR, the proposed antenna keeps its radiating beam at about θ = 45°in E-plane through the whole band. The UWB antenna is fed by a coaxial probe through a SMA connector. The length of the proposed monopole element above the ground is slightly less than λ/4 of the lowest frequency. The simulated and measured results of the VSWR, he gain and the radiation patterns for the proposed antennas are presented and discussed. Good agreement between simulated and measured results is demonstrated.
A novel multipolarized sectoral antenna on a metallic electromagnetic band gap (M-EBG) surface is investigated. The M-EBG structure behaves as a partially reflecting surface (PRS) and enhances the directivity of a simple radiating source. The use of metallic structures offers a new approach to industrial partners in order to reduce costs and to facilitate design techniques. By using double layers of M-EBG structure working on orthogonal polarizations as a superstrate with a single patch feeding by two ports, multipolarization operation is achieved. This antenna provides vertical, horizontal, 0°/90°and circular polarizations with a sectoral radiation pattern in the azimuth plane. M-EBG antennas with sectoral pattern are usually designed only for vertical polarization. In order to verify the results a Bipolar M-EBG Sectoral antenna prototype for WIMAX application~[5.15-5.35] GHz is realized and measured. Finally, we study the possibility to generate circular polarization.
In this article, a compact microstrip-fed printed dual band antenna for Bluetooth (2.4-2.484 GHz) and UWB (3.1-10.6 GHz) applications with WLAN (5.15-5.825 GHz) band-notched characteristics is proposed. It is demonstrated that dual band characteristics with desired bandwidth can be obtained by using a fork shaped radiating patch, whereas, band-notched characteristics can be obtained by etching two L-shaped slots and two symmetrical step slots on the rectangular ground plane. The proposed antenna is simulated, fabricated and tested. The structure is fabricated on a low cost FR4 substrate having dimensions of 50 mm (Lsub) × 24 mm (Wsub) × 1.6 (H) mm and fed by a 50 Ω microstrip line. The proposed antenna has S11 ≤ -10 dB over 2.18-2.59 GHz, Bluetooth band, 3.098-5.15 GHz and 5.948-11.434 GHz, UWB band with WLAN band notch. The structure exhibits nearly omnidirectional radiation patterns, stable gain, and small group delay variation over the desired bands.
This paper studies static effect of communication Low Noise Amplifier (LNA) that utilizes GaAs wafer. It analyzes the Electro-Static Discharge (ESD) effect, which occurs within communication components, such as GaAs LNA, and describes testing standard and methods. In order to find out GaAs LNA's susceptibility to static, two well-recognized communication GaAs LNA IC models were selected to be tested. Commercial program allowed measuring of static energy inserted within LNA's internal circuit by running a simulation about static discharge of GaAs LNA. Then we analyzed malfunctions caused by static and discussed about architectural problem and improvement according to the test and simulation result, from the perspective of GaAs LNA's electro static discharge.
A concurrent multi-band low-noise amplifier (LNA) for both WLAN and WiMAX applications covering 2.4-2.7 GHz, 3.3-3.8 GHz and 5.1-5.9 GHz is mainly investigated. The proposed LNA consists of two cascaded common-source stages and employs stepped-impedance transformers and series and shunt feedback techniques to obtain good return loss, low noise and high linearity simultaneously. Test results show that the LNA features input and output return loss of 12 dB, gain of 21 dB, and noise figure of 2\,dB across the three bands of operation, which are the state of the art among the counterparts.
A key feature of upcoming 4G wireless communication systems is multiple-input-multiple-output (MIMO) technology. To make the best use of MIMO, the antenna correlation between adjacent antennas should be low (< 0.5). In this context, we propose a correlation reduction technique suitable for closely spaced antennas (distance, d < λ/40). This technique reduces mutual coupling between antennas and concurrently uncorrelates antennas' radiation characteristics by inducing the negative group delay at the target frequency. The validity of the technique is demonstrated with a USB dongle MIMO antenna designed for LTE 700 MHz band. Measurement results show that the antenna correlation is reduced more than 40% using the proposed technique.
This paper presents the design and fabrication of a class of dielectric filled rectangular waveguides using a multilayer photoimageable thick-film technique. The original fabrication technique is modified to shorten fabrication time and improve waveguide thickness to reduce transmission structure losses. The materials used are first characterized before the wave-guiding properties are extracted. The fabricated waveguides show excellent results in term of loss and a 1% variation in permittivity over a wide frequency range of 10-100 GHz. To demonstrate the practical applications of this modified fabrication technique, 5th and 3rd order band-pass filters are designed and fabricated. The different incertitude on the fabrication issues is studied showing an effect on the bandwidth and central frequency. The measurement results of the fabricated prototypes agree well with the simulated ones. A broadband 3 dB coupler is designed and fabricated covering both V and W bands. The measurements results for this circuit show good performance with 23% of bandwidth and are in good agreement with the simulations.
This study develops a compact 28 GHz bandpass filter on a low-temperature co-fired ceramic substrate for applications in LMDS (Local Multipoint Distribution Service) bands. The filter comprises two pairs of verticallystacked cross-coupled open loops with vertical interconnection structures, achieving compactness, high integration, and superior frequency selectivity. Attaining selective response with two transmission zeros requires adjusting the couplings of adjacent resonators and external quality factor. The open loops are fed by using the three-via vertical interconnections to prevent any electrical effect on the filter. Measurements correlate closely with the simulation results: this study achieved a bandwidth of 2.1 GHz (27.6-29.7 GHz) with two zeros located at 25.8 GHz and 31.1 GHz, and a compact size of 2.69 x 2.66 x 0.4 mm3.
This paper presents a novel structure for compact dual-band balun design. The proposed structure is based on modified Marchand (with the fourth port shorted). To achieve the desired dual-band operation, two additional open-ended stubs are added to the two balanced ports of the modified Marchand balun. Explicit design equations are then derived using even-odd mode analysis. Finally, to verify the design concept, a microstrip balun operating at 0.9/2 GHz are fabricated on Duroid RO3210 printed circuit board. Measurement results are in good agreement with the theoretical predictions.
A new microstrip diplexer with very high output isolation and low insertion losses is presented in this letter. With the adoption of the spiral compact microstrip resonant cell (SCMRC) form into the dual behavior resonator (DBR) microstrip filter design, a bandpass filter with high rejection in the upper stopband can be achieved. Therefore, very high output isolation for the diplexer can be realized. Furthermore, the proposed diplexer also has a property of low insertion loss in the passband. To validate the design theory, one demonstrator diplexer has been designed and fabricated; the results indicate that the proposed diplexer has good performance of simple structure, better than 65 dB output isolation in the stopband, and less than 1.2 dB insertion losses in the passband.
A compact microstrip ultra-wideband (UWB) bandpass filter (BPF) including a narrow notched band within the UWB passband is proposed. The proposed filter is constructed by combination of two highly compact wideband bandpass filters (BPFs) with different physical dimensions which are designed on the basis of a folded-T-shaped stepped impedance resonator (SIR) and parallel-coupling feed structure. The wideband BPFs can be designed separately, and the design procedure is described. The narrow notched band with 3.8% 3 dB fractional bandwidth (FBW) from 5.15 to 5.35 GHz (IEEE 802.11a lower band) is created in order to eliminate interference from wireless local area network (WLAN) with the determined UWB passband. The center frequency and bandwidth of the notched band can be controlled by tuning the structural parameters. The full-wave EM simulated and measured results are in good agreement, showing that the proposed filter possesses good characteristics including wide passband, high selectivity, low insertion loss, large notch deep and sharp rejection.
A printed dipole antenna with back to back asymmetric dual-C-shape uniform strips capable of generating a wide operating band for digital television (DTV) signal reception in the 470-862 MHz band is presented. This antenna is associated with C-shape strips and asymmetric structure, and it operates band in 455-865 MHz. By proper adjusting some parameters, it is possible to achieve a broadband response. Measured results have been compared with simulation and found in a good agreement. The antenna with back to back asymmetric dual-C-shape uniform strips can generate two adjacent resonant modes to form a wide operating band of larger than 62% in 2.5:1 VSWR bandwidth, which is much wider than that of the corresponding back to back symmetric dual-C-shape strips dipole antenna. The experimental results show that stable radiation pattern is similar to a dipole antenna. The measured peak gains are 3.2 dBi and 2.3 dBi, at 620 MHz and 780 MHz, respectively. The radiation efficiencies are all larger than 60% for an entire DTV band.
A simple DoA estimator is proposed with a switched beam antenna. The estimator is implemented with an adjacent pattern power ratio algorithm. For a single source signal, the received signal powers are measured while the antenna switches over a set of measured directive beam patterns. The pattern that exhibits the maximum received signal power is chosen. Then, the ratio between the pattern adjacent to the chosen pattern and the chosen pattern, is used to find the DoA by using a lookup table or by performing a linear regression approximation. Compared with conventional DoA estimators with switched beam antenna, the proposed algorithm allows DoA estimation with low computational cost, without sacrificing much the estimation precision. Computer simulations and experiments in an anechoic chamber are carried out to verify the proposed algorithm with a switched beam antenna: the electronically steerable parasitic array radiator (ESPAR) antenna.
A novel single-layer broadband coplanar waveguide-fed antenna with band-rejected characteristic is proposed for WLAN/WiMAX operation. First, the broadband characteristic (2.43-5.97 GHz) is achieved by a CPW-fed patch antenna with a dual-Y slot. Then, a single slit is inserted on the radiating patch or ground plane to introduce a notched band. The proposed antenna has a compact size of 40 × 25 mm2. The broadband characteristic and band-rejected functions of the proposed antennas are implemented and measured. Two types of antennas were studied. Measured notched-band impedance bandwidths (return loss <10 dB) are 370 MHz and 1050 MHz, respectively, which satisfies the requirements for WLAN and WiMAX applications. Detailed design steps and experimental results for the designs are studied and investigated in this paper.
The design and optimization of an annular ring dielectric resonator antenna (DRA) operating in the C frequency band is addressed. The DRA is intended to be used as the radiating element of a transmitting array of active integrated antennas, its input impedance must exhibit a proper resistive load at the fundamental resonance frequency, as well as a dominant reactive behavior, either inductive or capacitive, at higher harmonics. The configuration here proposed is a slot-coupled annular DRA where harmonic tuning is performed by resorting to a proper shape factor. The design procedure is performed by exploiting artificial neural networks, to find the resonator geometry starting form the desired resonance frequency, and a finite elements based numerical tool for the electromagnetic characterization of the antenna. Samples of simulation results are shown to demonstrate the capabilities of the proposed slot-based harmonic tuning technique for ring DRAs.
Electronically steerable passive array radiator (ESPAR) antennas are expected to gain prominence in the field of wireless communication, because they can be steered toward a desired signal and they can eliminate interference; in addition, they have a very simple architecture that has significantly low power consumption and are inexpensive to manufacture. In this paper, we proposed an ESPAR antenna that has fastest convergence time. The downhill simplex method is used to maximize the correlation coefficient between the received signal and the reference signal. The simulation results indicate that this antenna can be steered toward the desired signal if one signal is used; in addition, it can eliminate interference if two signals, namely, the desired signal and the delayed signal are used by automatically varying the reactance values.
This paper proposes a new propagation model based on the most widely used Hata model. The proposed model is developed by extrapolating Hata model to be suitable microcells. The main equation of Hata urban model is modified by substituting the suburban correction factor with a terrain roughness parameter. This parameter uses a quadratic regression estimator of the standard deviation, σ, of the terrain irregularities along the measuring path, in west of Amman, Jordan. It is shown that RMSE between the predicted and measured data for the new proposed, is improved by up to 3 dB compared to Hata suburban model in most areas under study. Furthermore, the improvement in RMSE increases as σ increases. These results clarify the robustness of the proposed model.
This paper presents a novel dual-band circularly polarized CPW-fed circular slot antenna with two open-ground rings. The proposed antenna is constructed with two opened-ground rings facing in opposite directions and embedded in the circular slot, and the enhanced feed strip of CPW. By way of adjusting the relevant parameters, we can obtain the dual-band at 1.57 GHz and 2.46 GHz respectively. A smaller frequency ratio of 1.56 is presented. The measured -10 dB return loss impedance bandwidth are 380 MHz (24.68%) for 1.57 GHz band and 210 MHz (8.33%) for 2.46 GHz band. The measured -3 dB axial ratio bandwidth for 1.57 GHz and 2.46 GHz bands are 13.38% and 8.13%, the polarization of radiation patterns are RHCP and LHCP for each band and the antenna gain are 3.72 and 3.21 dBic respectively.