A coax-feed low profile dual-polarized circular patch antenna with ±45˚ polarization is presented. The antenna consists of a dual-polarized circular patch excited by two coax-lines and an AMC reflector. By using the AMC reflector as the ground plane of the patch antenna, the profile of the antenna is reduced to λ/8 of the operation frequency, which is much lower than that of the conventional dual-polarized patch antenna. The experimental results show that the proposed design obtains a wide bandwidth (2.12-2.77 GHz) and a high isolation (>35 dB) over the entire band. In addition, the front-back radio of the antenna is improved significantly by using the AMC reflector. The wide bandwidth, low-profile and high front-to-back ratio make the antenna a good candidate as a base station antenna for WLAN, WiMAX and LTE applications.
A dual-beam frequency scann ing microstrip antenna is proposed in this letter. The wellknown characteristic of the conventional leaky wave antenna is the beam scanning with operating frequency variation. Here, four slots are applied on the ground plane of the conventional leaky wave antenna structure to obtain the dual-beam frequency scanning characteristic. According the results, it shows that this work with relatively simple structure radiating not only in upper half-plane, but also in lower half-plane. The upper half-plane main lobe scans from 356˚ (-4˚) to 24˚ (scanning region is 28˚). Meanwhile, the lower half-plane main lobe scans form 190˚ (-170˚) to 161˚ (scanning region is 29˚). The 7-dB return loss bandwidth is 600 MHz from 3.4 GHz to 4 GHz. In addition, the measured average antenna gain is about 5.3 dBi in the operating frequency.
In this letter, a reflectarray antenna based on the folded stepped impedance resonator (SIR) patch-slot configuration with variable size is presented. A novel frequency selective surface (FSS) in the reflectarray as a ground plane for reducing radar cross section (RCS) level is applied. The FSS is based on the folded SIR configuration. Two prime-focus 15 × 15 reflectarray antennas backed on the folded SIR FSS ground and a conventional ground are designed and manufactured. The radiation performance of a reflectarray element backed either by a solid ground plane or a band-stop FSS structure is compared. The measured results demonstrate that the radiation pattern and gain of the FSS-backed reflectarray are almost same to its counterpart backed by a conventional ground plane at the operating band of 11.5 GHz. The RCS is effectively reduced in the out of this band when compared with the reflectarray with a solid metal ground plane of the same dimension.
A novel compact wideband b andpass filter using rotational symmetric loaded structure is proposed in this paper. A λ/4 parallel coupled line is first introduced to form a passband with desired center frequency. The rotational symmetric structure with short/open circuit stubs is then introduced as a loading structure to improve the filter's performance. The rotational symmetric loading structure is discussed in detail in this paper, and a pair of transmission zeros is obtained and located at two sides of the passband to improve the passband selectivity intensively. Moreover, three open circuit stubs are utilized to replace one single stub for obtaining a wide stopband. At last, the proposed filter is fabricated and measured, and the results show a good agreement with each other.
In this paper, a new design of asymmetric coplanar strip (ACS)-fed UWB planar monopole antenna with dual band-notched characteristics is presented and investigated. The proposed antenna is composed of an asymmetric ground plane, a semi-circular radiator, together with two open-ended half wavelength bow-shaped slots etched on the radiation patch. This leads to the desired dual notched bands of 3.12-3.69 GHz for WiMAX and 5.51-6.01 GHz for WLAN. Experimental results show that the designed antenna, with compact size of 29.5×12 mm2, has stable and omnidirectional radiation pattern, sharp reduction in gain and group delay at notched frequencies. The very simple feeding structure and compact uniplanar design make it easy to be integrated within the portable device for UWB communication systems.
A modified generalized memory polynomial model (MGMP) is proposed for RF power amplifiers (PAs). The MGMP model is derived by applying complexity-reduced technique to the generalized memory polynomial model (GMP)， and the least square (LS) algorithm is used for coefficient extraction. The proposed MGMP model is assessed using a GaN Class-F PA driven by two modulated signals (a WCDMA 1001 signal and a single carrier 16 QAM signal with 20 MHz bandwidth). The experimental results demonstrate that the MGMP model outperforms the memory polynomial (MP) model and the generalized memory polynomial (GMP) model. Compared with MP model, the MGMP model shows a normalized mean square error (NMSE) improvement of 2.13 dB in forward modeling, average adjacent channel power ratio (ACPR) improvement of 2.62/2.11 dB in the DPD application with almost identical number of model coefficients. In contrast with the GMP model, the MGMP model can achieve comparable forward modeling and linearization performance results, but reduces approximately 40% of coefficients.
In this paper, a novel compact dual-band microstrip antenna operating at two different bands namely C-band and X-band is presented and analyzed. The dual ultra wide band is realized by cutting two triangular slots on the right and on the left sides of the patch and a rectangular slot on the top side of the patch. The antenna structure is optimized and simulated using commercial software. The excitation is launched through a 50 Ohms microstrip line. According to simulation and measured results the proposed antenna can provide two separated impedance bandwidths of 500 MHz centered at 7 GHz and 2 GHz centered at 10.7 GHz and stable radiation patterns.
An X-band ferrite-loaded half mode substrate integrated waveguide (HMSIW) phase shifter is proposed and fabricated in this paper. A full-height E-plane Yttrium Iron Garnet (YIG) ferrite slab is embedded in the HMSIW to construct the non-reciprocal phase shifter. With the application of a magnetic bias field on the ferrite slab, the phase of the ferrite-loaded HMSIW can be adjusted and controlled. For a magnetic bias field of 1800 Gauss, the insertion loss is less than 3.2 dB from 9.7 to 11.0 GHz. The return loss is better than 10 dB over the same frequency range. The largest differential phase shift can be up to 337°. This circuit is easily integrated with other planar components and also has the capability to handle medium power level.
A novel ortho-mode transducer (OMT) for dual-band dual-polarized communication systems is proposed in this letter. The OMT is loaded with five posts in reasonable positions of the waveguides and a shorted circuit piston in the branch waveguide. Compared with the septum loaded traditional one, the presented OMT is more flexible, simple and easy to fabricate. Both simulations and measurements indicate that the impedance bandwidths of VSWR<1.15 ranging from 6.50 to 7.20 GHz and 8.80 to 10.2 GHz can be obtained. The low insertion losses indicate that the presented OMT can be used in actual project. Moreover, good isolation performance between the two input ports in both bands are obtained because of the inherent existence of cross polarization.
3D integration using through-silicon-vias (TSVs) is gaining considerable attention due to its superior packaging efficiency resulting in higher functionality, improved performance and a reduction in power consumption. In order to implement 3D chip designs with TSV technology, robust TSV electrical models are required. Specifically, due to the increase of signal speeds into the gigahertz (GHz) spectrum, a high frequency electrical characterization best describes TSV behavior. In this letter, 5x50 μm TSVs are manufactured using a via-mid integration scheme and characterized using S-Parameters up to 65 GHz. At 50 GHz, the measured attenuation constant is 0.35 dB/via with a time delay of 0.7 ps/via.
The purpose of this paper is on the behavioural modelling of surge voltage pulses used in Atom Probe Tomography. After brief description of the atom probe functioning principle, we examine the excitation electrical pulse signal integrity along the electric pulser (E-pulser) feeding line modelling with respect to the IEC1733/04 standard. This feeding electric line is ended by cylindrical via ground to control the ion emission. By using the transmission line (TL) ultra-broadband RLCG model, the propagating pulsed signals degradation is predicted. The signal propagation was analysed in both frequency and time domains by taking into account the substrate dispersion. The wideband frequency behaviours of the surge signal along the feeding line were examined from DC-to-2 GHz. In addition, by considering pulse surge signals with pulse-width and rise-/fall-time parameters (T1=9 ns, tr1=tf1=1.6 ns) and (T2=30 ns, tr2=4 ns/tf2=18 ns), the transient responses from 5 cm to -20 cm length TL are characterized. It was shown that the excitation pulse was significantly distorted. It was emphasized that the operated signal delay varies from 0.3 ns-to-1.5 ns in function of the via capacitor value. The time-dependent radiated E-field on the performance of the atom probe system which enables to characterize the nature of tested materials (ions or atoms) is discussed. The presented analysis approach is particularly useful for E-pulser integrated in measurement scientific instruments as Atom Probe Tomography time of flight optimisation, a nano-analysing technique that uses ultra-sharp high vacuum pulse to induce controlled erosion of samples. In this application, the excitation voltage pulse integrity during the propagation is required in order to improve the measurement instrument performances.
A novel broadband planar rotated cross monopole antenna, which consists of a vertical patch (area A) and a rotated horizontal patch (area B), is proposed. By rotating the horizontal patch, the bandwidth of the proposed antenna can be significantly enhanced. The effect of the rotated angle of the horizontal patch on the bandwidth has been deeply studied. The measured results show that the proposed antenna with compact size of 50×50 mm2 can achieve a wide impedance bandwidth (10-dB reflection coefficient) as large as 8.76 GHz (2.33-11.09 GHz) or about 130%, which is nearly two times of what the corresponding conventional cross monopole antenna was.
A Coplanar Waveguide(CPW)-fed monopole loaded with Composite Right/Left Handed Transmission Line (CRLH-TL) unit cell is presented in this letter. Multiband is achieved due to the nonlinear dispersion relation of the CRLH-TL unit cell. The CRLH-TL unit cell supports a fundamental LH wave (phase advance) at lower frequencies and a RH wave (phase delay) at higher frequencies. By loading CRLH-TL unit cells with a conventional monopole, the resonant frequency of higher order mode can be decreased and zeroth-order mode or even negative-order mode can be achieved. As a result, the proposed antenna operates at 1.43 GHz, 2.58 GHz, 3.31 GHz and 4.4 GHz. Finally the modified antenna is fabricated and measured; measurements and EM simulations are in a good agreement that confirms the proposed theory.
This work is devoted to a theoretical investigation of the current crowding problem in flat conductors bent at arbitrary angles. Using conformal mapping techniques, we succeed in obtaining an analytical expression for current density distributions in such conductors. It is shown that the current density increases in a small vicinity of the corner and approaches to infinity at its top. In order to eliminate the infinity, the vertex is replaced by an arc of a circle with a small radius. The method has been developed for an arbitrary angle; several specific examples are considered.
This paper presents a novel method for the two-dimensional direction of arrival (DOA) estimation based on QR decomposition. A configuration with two uniform linear antenna arrays (ULA) is employed for the joint estimation of elevation (θ) and azimuth (φ) angles. Q data matrix will estimate the azimuth angle while R data matrix will estimate the elevation angle. The proposed method utilizes only a single snapshot of the received data and constructs a Toeplitz data matrix. This reduces the computational complexity of the proposed method to O((N+1)2) from O(N3) for SVD based methods. The structure of the data matrix also favors the 2D DOA estimation for both coherent and non-coherent source signals. Simulation results are presented, and performance of the proposed method is compared with the Matrix Pencil method for 2D DOA estimation of multiple incident source signals.
In this paper, magnetic material was applied in the design of a UHF-RFID metal tag to increase the reading distance. The influence of the electromagnetic properties, especially the electromagnetic loss, of magnetic substrate on the gain of the tag antenna is discussed by analyzing the reflection and the surface current distribution. As to folded antenna, the loss of energy caused by the magnetic substrate tends to occur in the folding edge of the antenna. Both simulations and experiments indicate that electromagnetic loss markedly reduces the gain rapidly when both the dielectric loss tangent (tanδ) and the magnetic loss tangent (tanδm) are between 0 and 0.3. The reading distance drops from 3 m to 1.5 m when the tanδm of the magnetic composite substrate increases from 0.009 to 0.023. And tanδm should be less than 0.1 for the antenna working excellently. The conclusion offers meaningful guidance for future studies of magnetic substrate folded metal tag.
In this paper, the author studies, through numerical simulation, the classical analog of the electromagnetically induced absorption/reflection (EIA) in a planar metamaterial structure in the near infrared spectral region. The structure is designed by transforming an electromagnetically induced transparency (EIT) structure into an EIA structure using Babinet's principle. The structure exhibits a coupling between a bright mode (a complementary ring resonator (CRR)) and a dark mode (pair of parallel straight slits) imprinted on a glass substrate. A narrow absorption window, induced in a wide transparent window, is achieved by the structure and the strength of coupling is tuned by the degree of breaking symmetry and relative displacement of the two mode elements.
A new wideband vertical planar printed unidirectional antenna is presented. The proposed antenna is composed of a bowtie electric dipole, a loop antenna and a microstrip-to-coplanar stripline balun. All of them are printed in the same plane perpendicular to the ground. The antenna has a wide impedance bandwidth of 87.2% for SWR≤2 from 3.3 to 8.4 GHz and a stable gain of 7.3±1.5 dBi over the operating frequencies. Moreover, stable unidirectional radiation pattern with low back-lobe radiation, low cross polarization and nearly identical E- and H-plane patterns is also demonstrated over the frequency of interest. A prototype is fabricated and measured. The measured results indicate that the antenna is suitable for wideband wireless communication system.
A novel dual-band filter based on substrate integrated waveguide (SIW) is presented in this paper. The proposed filter is composed of two filters with different center frequencies and bandwidths, where they share the input and output ports with source-load coupling using rectangular SIW cavity structure. Muliti-transmission zeros have been obtained through electrical coupling between the source and load, which improves the frequency-selective characteristics of the filter greatly. Finally, a Ku-band substrate integrated waveguide dual-band filter with bandwidths of 220 MHz and 120 MHz was finally designed, fabricated, and measured. The measurement results are found to be in good agreement with the simulation results.
A novel design of miniaturized dual-bandantenna based on mushroom cell and interdigital capacitor is presented in this paper. Four transmission line (TL) elements are loaded in a microstrip antenna, and each one is composed ofamushroom cell and interdigital capacitors. The interdigital capacitors contribute to the series capacitance and metallicvia-hole of mushroom structuresresult in the shunt inductance in the equivalent circuit model. The antenna works as a zeroth-order (f0= 2.51 GHz) and first-order (f1 = 3.78 GHz) resonant antenna with varied radiation patterns. Omnidirectionalradiation pattern and unidirectional radiation pattern are obtained at 2.51 GHz and 3.78 GHz, respectively.The overall size of the antenna is only 0.25×0.25×0.017λ03 (at f0= 2.51 GHz). The proposed antenna features compact structure, low profile and easy fabrication. Good agreement between the simulated and measured results is also achieved, validating our design concept.