A novel miniaturized microstrip dual-mode filter using a half wavelength resonator with centrally loaded open stub and quasi-L shaped feed-lines is proposed. The advantage of using such a resonator is inherently generating a transmission zero by itself. To further improve the selectivity, quasi-L shaped feed-lines are introduced to create additional transmission zeros. Theoretical and simulated analyses of this filter are performed. A demonstration filter centered at 2.33 GHz with a fractional bandwidth of 4.7% is designed, fabricated and measured to validate the design methodology.
A 16-way radial waveguide power divider with the characteristics of low insertion loss and high power handling capacity is investigated. Its design theory and basic structure are proposed at first; a power divider with the center frequency of 4.0GHz is designed, fabricated, and measured. Good agreement between the simulated and measured results is found for the proposed power divider. The measured 15-dB return loss bandwidth is demonstrated to be 440MHz and the measured 0.5-dB insertion loss bandwidth is demonstrated to be 540MHz. The power handling capacity of the proposed power divider is analyzed through simulation, and the results prove its usability in high power applications.
A novel extremely wide band dipole antenna with omni-directional radiation patterns is investigated experimentally and numerically. The proposed antenna comprises two groups of crossing semicircular discs. The shape of each disc is modified to broaden the working bandwidth. Measured results demonstrate that the novel antenna possesses good impedance match from 0.45 to 38.9 GHz for S11 lower than -10 dB, in good agreement with simulated results. Omni-directional radiation patterns keep stable within the operating band. The proposed antenna is highly suitable for various wide band systems.
A high performance balun bandpass filter (BPF) with very simple structure is proposed in this letter, this structure realizes superior performance in bandpass filtering meanwhile with good differential performance of the balun. The proper balanced outputs and BPF characteristic by the symmetric feeding and skew-symmetric feeding have been obtained, and the theory of this simple structure for unbalanced input to balanced outputs has been studied. The center frequency of the fabricated balun-BPF was operated at 2.4 GHz with 5.8% fractional bandwidth (FBW), and this frequency is used for Bluetooth and some other communication systems. The differences between the two outputs are 180° ± 5° in phase and within 0.39 dB in magnitude. At f0, the amplitude imbalanced and phase difference are within 0.37 dB and 179.2°, respectively. The measured frequency responses agree well with the simulated ones. With the theoretical analyses and practical results, it is shown that the proposed one has the advantages of simple structure, convenient analysis and good performance of both BPF and balun.
A compact ultrawideband (UWB) monopole antenna with two U-shaped slots for WLAN and WiMAX dual band-notched functions is proposed and experimentally studied. The proposed antenna with the size of 28 mm×24 mm×1.6 mm is excited by a 50Ω microstrip feed line. The band-notch functions are realized by loading two approximate half-wavelength U-shaped slots which change the current distribution on the Y-shaped patch. The obtained results show that the designed antenna has an impedance bandwidth of 2.95 GHz-12 GHz for S11 ≤ -10 dB, except two frequency stop-bands of 3.32 GHz-3.98 GHz for WiMAX and 4.81 GHz-6.68 GHz for WLAN. The antenna has successfully fabricated and measured. The return loss, band-notched characteristic, radiation patterns and peak gains are presented.
This paper reports material selection methodology for radio frequency - micro electro mechanical systems (RF-MEMS) switches used for reconfigurable antennas. As there are variety of materials available to design engineer, a proper technique to select the best possible material is needed. Three primary performance indices, pull-in voltage, RF-loss, and thermal residual stress, are used to obtain the desired performance. The selection chart shows that aluminum is the most suitable material for being used as bridge material in RF-MEMS switches to provide the best performance in reconfigurable antenna.
Power efficiency is a key issue in wireless sensor networks due to limited power supply. Buffer management is also crucially important in the scenario where the incoming traffic is higher than the output link capacity of the network since a buffer overflow causes power waste and information loss if a packet is dropped. There are many available buffer management schemes for traditional wireless networks. However, due to limited memory and power supply of sensor nodes, the existing schemes cannot be directly applied in wireless sensor networks (WSNs). In this work, we propose a multi-layer WSN with power efficient buffer management policy which simultaneously reduces the loss of relevant packets. Unlike the conventional WSNs which consider the whole network as single layer, we divide sensor network topology logically into multiple layers and give a three-layer model as an example. In our proposed scheme, the layers are differentiated by the sensors' information. The buffer can then judge the packets from different layers and then make a decision on which packet to be dropped in case of overflow. We show that our proposed multi-layer WSN can reduce the relevant packet loss and power waste for retransmission of lost packets.
In this paper, antenna ultra wideband enhancement by non-uniform matching is proposed. The antenna consisted of a rectangular shaped radiator with two convex circled corners. Simulated results using CST Microwave Studio and measured results of a fabricated antenna concord well to prove that it can operate from about 3.5 GHz to 4.6 GHz and from 7.4 GHz to 12.7 GHz for S11 (dB) < -10 dB. In addition, a good impedance matching is noted in the IEEE radar engineering X band range since the return loss coefficient remains below -50 dB value at 9.5 GHz and can reach -45 dB at 11 GHz. A current density comparison at 11 GHz, supporting our argument, between a stepper corner and convex corner demonstrates that the current density can reach 52 A/m with a convex corner whereas it does not exceed 33 A/m for the antenna with a stepper corners. Radiation patterns at various frequencies and peak gains show clearly interesting features of such antennas.
Star-junction multiplexers are used when the number of channels is relatively small since the resonating junction has to be connected to many filters' outputs. In this paper, novel topologies of star-junction multiplexers with resonating junctions are proposed. The advantage of the proposed topologies is that the number of connections to the resonating junction is reduced and thus allowing multiplexers with more channels to be implemented. An optimization technique is used to synthesize the coupling matrix of the proposed multiplexers, and numerical examples are illustrated in this paper.
Previous works on maximum ratio combining (MRC) diversity have derived a closed-form cumulative distribution function (CDF), referred to as Lee's formula, for spatially correlated Rayleigh fading channels. It is usually believed that (due to its singularity) Lee's formula will result in large numerical error when two eigenvalues of a diversity antenna's covariance matrix are close to each other. This letter shows that the limit of Lee's formula converges to the true CDF as eigenvalues converge to each other, which implies that Lee's formula is robust in determining diversity gains of arbitrary antennas based on stochastic measurements.
A miniature single-layer CPW-fed monopole antenna with triple-band operation for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications is presented. The proposed antenna, comprising a planar rectangular patch element embedded with dual U-shaped slot, is capable of generating three distinct operating bands, 2.37 - 2.53, 3.34 - 3.82, and 4.23 - 6.88 GHz covering all the 2.4/5.5/5.8 GHz WLAN bands and the 3.5/5.5 GHz WiMAX bands. The designed antenna has a simple uniplanar structure and occupies a small size of 25×18 mm2 including the finite ground CPW feeding mechanism. Moreover, the proposed antenna shows good monopole-like radiation patterns with small cross-polarization and stable antenna gains across the three operating bands.
This paper presents a compact microstrip-fed slot antenna with triple-frequency operation. The proposed antenna structure consists of a cross-shaped microstrip feed line and multiple open-ended slots on the ground plane. By properly selecting shapes and dimensions of these embedded slots, the triple-resonance situations at 2.4/3.5/5.8GHz are obtained. Meanwhile, the cross-shaped feedline with shorting pin makes a joint benefit to adjust the matching condition and impedance bandwidth. The numerical and experimental results exhibit the designed antenna operates over triple frequency ranges and covers numbers of useful frequency bands for present wireless communication systems. In addition, acceptable radiation characteristics are obtained over the operating bands.
A novel nano-antenna system design using photonic spin in a PANDA ring resonator is proposed. This photonic spins are generated by a soliton pulse within a PANDA ring, in which the transverse electric (TE) and a transverse magnetic (TM) fields are generated. The magnetic field is introduced by using an aluminum plate coupling to the microring resonator, in which the spin-up and spin-down states are induced, where finally, the photonic dipoles are formed. In operation, the dipole oscillation frequency is controlled by a soliton power, coupling coefficients, and ring radii. The obtained results have shown that THz frequency source can be generated by the proposed system. The advantage of proposed system is that the simple and compact nano-antenna with high power pulse source can be fabricated, which can generate and detecte the THz frequency in a single system.
The miniaturization of conventional ring resonators is demonstrated by forcing a voltage minimum at one end of the resonator. In addition, the resonator is loaded with a capacitance to achieve further miniaturization and reducing its sensitivity to substrate thickness tolerance. The final resonator is 73% smaller than a conventional ring resonator and has a tenfold decrease in sensitivity to substrate thickness variations. Using this resonator a 4-pole quasi-elliptic filter is fabricated showing good agreement between simulation and experimental results.
In this paper, the electromagnetic field of a horizontal infinitely long magnetic line source over the dielectric-coated earth is treated analytically, and the complete approximate solution for the radiated field under the far-field conditions is outlined. The total field is composed of four modes: the direct wave, the ideal reflected wave or image wave, the trapped surface wave, and the lateral wave. In particular, the complete analytical formulas are obtained for both the trapped surface wave and the lateral wave. The trapped surface wave is determined by the sum of residues of the poles. When the infinitely long magnetic line source or the observation point is away from the planar surface of the dielectric-coated earth, the trapped surface wave deceases exponentially in the z direction, and the total field is determined primarily by the lateral wave. When the conductivity of the earth is large, and both the infinitely long magnetic line source and the observation point are on or close to the air-dielectric boundary, the total field is determined primarily by the trapped surface wave.
We present a band-stop filter (BSF) by using a periodic structure property of frequency selective surfaces (FSSs) embedded in a microstrip transmission line. The proposed BSF is designed with FSS unit cells modifying the cross-loop slots. The center frequency (fo) of the BSF is 6.6 GHz, and the 3-dB bandwidth varies by the number of cascading unit cells. The BSF is interpreted with an equivalent circuit model and a dispersion diagram, and exhibits uniplanar geometry, low return loss, simple fabrication, smaller size, and wide bandwidth.
Due to the integration of different wireless applications at different bands on a single device, multi-band microstrip patch antenna is the best solution keeping the overall size of the device small. In the present work, a metamaterial-inspired antenna is proposed for WiMAX/WLAN applications. Design studies, parametric analysis, simulation results along with measurements for an L-shape slotted ground microstrip patch antenna with CSRR (Complementary Split Ring Resonator) embedded on patch structure operating simultaneously at WiMAX (3.5 GHz) and WLAN (5.8 GHz) are presented. The metamaterial-inspired loading is exploited to create resonance for upper WLAN band while an L-shape slot on the ground plane resonates at the WiMAX band, maintaining the antenna's overall small form-factor. The measured S-parameter and radiation patterns of fabricated prototype show that the proposed design is suitable for emerging WiMAX/WLAN applications.
A technique that expands dynamic range (DR) of frequency down-converters in the C band frequency is presented. Primary characteristics of down-converter are evaluated to confirm that it can be used in microwave receivers. The C band down-converter is carried out by the combination of RF mixers, band pass interdigital filter, and X band combline filter which are designed entirely for this project. Attainment of the perfect receiver is the final purpose of this paper, and a method that causes 72 dB dynamic range, high tangential signal sensitivity and fine gain flatness is used for achieving the mentioned purpose. These efforts improve the dynamic range about 19 dB and gain flatness about 3.07 dB.
A double-layer radial line helical array antenna with rectangular aperture is proposed. With rectangular aperture, the antenna can be assembled to form high gain antennas. The use of double-layer feed system ensures an equal-amplitude in-phase feed for all elements in an expected frequency band, which can improve antenna gain and aperture efficiency. This paper presents its design concept, derives pertinent design and performance, and a 16-element array antenna is simulated and measured. The experimental results show that in the range of 3.8 GHz to 4.2 GHz, the antenna gain is over 17.7 dB, aperture efficiency over 82%, antenna sidelobe level below -12.0dB, antenna axial ratio below 3.2 dB, and antenna VSWR below 1.52.
This paper presents a design methodology of wide-band bandpass filters based on short-circuited multi-conductor transmission lines with bonding wires between alternated strips. General design guidelines, based on analytical equations, are derived and a left-handed behaviour of the multiconductor structure is inferred and studied. Analytical equations are assessed by means of full-wave electromagnetic simulations and experimental work. A very good agreement between theoretical results and measurements is achieved, that allows both the design and performance analysis of filters without the need for costly electromagnetic simulations. In addition, the equations presented yield a compact design of the filter with a left-handed behavior.
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