In this paper, a modified planar balanced Vivaldi antenna with endfire characteristics near the metal surface is proposed for 6-18 GHz applications. The proposed antenna structure consists of three copper layers, among which two external layers locate on the two outsides of two dielectric substrates, and the central layer is sandwiched by these two dielectric substrates. To further enhance the end-fire radiation characteristic, a number of novel techniques are proposed, including elongation and shaping of the supporting substrate of a conventional balanced antipodal Vivaldi antenna beyond its aperture, using an I-shaped slot loaded radiation patch and cutting a triangle on the edge of three copper layers. Measured and simulated results show that the proposed antenna not only exhibits good impedance bandwidth, but also improves the end-fire performance in the operational frequency of 6-10 GHz and achieves high gain in the end-fire direction, low cross-polarization and high front-to-back (F-to-B) ratio.
The wireless link between a mobile phone and its surrounding crucially depends on the quality and properties of the mobile phone antenna. The process of antenna selection is a multi-criteria decision-making problem with conflicting and diverse objectives. In this work, a model was built to select the best GSM mobile phone antenna in the design phase to increase the overall performance in the band. The model includes building an analytic hierarchy structure with a tree of hierarchical criteria and alternatives to ease the decision-making. The antenna options considered were limited to retractable whip antenna, loop chip antenna, monopole antenna, planar inverted F-antenna (PIFA), microstrip patch antenna, and printed slot antenna. An Analytical Hierarchy Process (AHP) was used to assist in building the model and help draw decisions. As a result of the decision making process, the monopole antenna was found to be the best choice for the GSM mobile phone antenna. Expert Choice™ software was used to conduct the experimental assessments. The judgments were found to be consistent, precise and justifiable with narrow marginal inconsistency values. The paper also presents a thorough sensitivity analysis to demonstrate the confidence in the drawn conclusions.
The performance of high resolution subspace-based algorithms are particularly sensitive to the prior information of the source number, the Signal-to-Noise Ratio (SNR) and the snapshot. Although the existing direction-of-arrival (DOA) estimation methods without estimating the source number could eliminate the awful impact brought by incorrect source number estimation, yet its performance would get deteriorated by small snapshots and low SNR. Methods which exploit noise and signal subspaces information simultaneously, such as SSMUSIC, could provide a high resolution performance in such nonideal circumstances. However, its performance would degrade severely when the prior information of the source number is incorrect. To provide a DOA estimation method without estimating the number of source, which has a high resolution performance in small sample and low SNR scenario, using all information spreads in eigenvalues and eigenvectors, this paper reconstructs a new spatial spectrum which is very similar to the SSMUSIC algorithm. In order to enhance the robustness of the new method, we provide an empirical method to modify the eigenvalues to prohibit the spreading of noise eigenvalues caused by snapshot deficient and low SNR. To verify the validity of the new method, comparisons with other algorithms are made in computer simulations and the measured data test.
This paper presents the field trial measurement data of WiMAX base station; it includes the system coverage, signal strength and available transmission rate. Data consisting of real time images, VoIP internet telephone are transmitted through Skype software by using WiMAX, HSDPA (3.5G) and EDGE (2G) transmission techniques, and these data are connected to centrally equipped wireless monitoring servers to perform data monitoring and analysis. Finally, we make comparisons, analysis and discussions of these three transmission techniques from the measured and characterized data.
This paper presents a frequency reconfigurable cedar-shaped fractal antenna. The special shape of the patch makes it simpler to integrate RF switches to connect consecutive branches. The proper activation/deactivation of the switches alters the current flow and changes the resonance frequency. Simulated and measured results show the characteristics of the presented design.
Multi-beam antenna arrays have important applications in the field of communications and radar. The reconfigurable design problem is to find the element in a sector pattern main beam with side lobes. The same excitation amplitudes applied to the array with zero-phase should be in a high directivity, low side lobe pencil shaped main beam. This paper presents a new method of designing a reconfigurable antenna with quantized phase excitations using an improved artificial bee colony, called IABC. Compared with subsequent quantization, experimental results indicate that the performance of the discrete realization of the phase-excitation value can be improved.
In this paper, new microstrip bandstop filters with single band, dual-band and tri-band by using U-shaped defected ground structures are presented without the assistance of coupled lines or certain resonators, and the application of DGS is developed. The proposed bandstop filters have good performances of low loss, multi-band operation, transmission zeros which improve the filter frequency selectivity, and miniaturization because of the cascade of DGS and minimum defected patterns which reduce the circuit size. The new designs are demonstrated by measurement.
A novel System-on-Package (SoP) implementation is presented for a transmitter (TX) module which makes use of electromagnetic coupling between the TX chip and the package antenna. The TX chip is realized in 0.13 μm CMOS process and comprises an on-chip antenna, which serves as the oscillator's inductor as well. The TX chip is housed in a Low Temperature Co-fired Ceramic (LTCC) package with a patch antenna. The on-chip antenna feeds the LTCC patch antenna through aperture coupling, thus negating the need for RF buffer amplifiers, matching elements, baluns, bond wires and package transmission lines. This is the first ever demonstration of wireless-interconnect between on-chip and package antennas which increases the gain and range of the TX module manyfold with respect to the on-chip antenna alone. Though the range of the TX SoP increases considerably, power consumption remains the same as that of the TX chip only. A simple analytical model for the new wireless-interconnect has been developed which helps determine the optimum position of the chip with respect to the aperture in the ground plane.
A magnetically tunable passive narrow-band split-mode mm-wave phase shifter based on dielectric resonance in yttrium iron garnet (YIG) is investigated. The novelty here is the demonstration of a phase shifter in the frequency region between two split dielectric resonances in YIG. It is shown that, under certain conditions, the differential phase shift from the split modes add up, resulting in a larger phase shift than for a single mode phase shifter. Two prototype phase shifters operating in the U- and W-bands at frequencies much higher than ferromagnetic resonance (FMR) in YIG have been designed and characterized. Phase shifts up to 30° with low losses and acceptable standing wave ratio are obtained for moderate bias magnetic fields. Equivalent transmission-line model taking into account coupling between the split resonances is presented and there is reasonable agreement between theory and experiment for both insertion loss and differential phase shift. Suggestions on further improvements of prototype filter characteristics have been outlined.
An ultra-wideband (UWB) balanced bandpass filter (BPF) is proposed and designed using defected ground structures (DGSs). A multimode resonator on top layer with a coplanar waveguide on bottom layer is used to design a UWB BPF. U-shaped and H-shaped DGSs loaded with capacitor are used to design to provide common mode rejection within a lower band, while a set of dumbbell-shaped DGSs are utilized to provide common mode rejection within an upper-band. The proposed UWB balanced BPF shows the performance of good common mode rejection in and out of the UWB passband.
A fast and simple parameter estimation algorithm, joint azimuth angles, elevation angles and polarization parameters of incident sources for an arbitrary conformal array is proposed. Based on 2-D Discrete Fourier Transform (2-D DFT), the computational complexity can be reduced significantly compared with traditional 2-D space-search MUSIC or polynomial rooting (search-free) methods. The antenna elements can be mounted on arbitrary curved surfaces or platforms. Conformal array characteristics, such as directional radiation patterns of the elements and polarization are taken into consideration. Numerical simulations based on real-world conformal arrays are provided to demonstrate the performance of the proposed method.
Unidirectional carbon/epoxy composite laminates are highly orthotropic, with their conductivity and permittivity being strongly dependent on the incident angle relative to the fibre orientation. This paper presents a novel frequency selective polarizing subreflector manufactured from unidirectional carbon fibre reinforced polymer (CFRP), placed a certain distance from a conducting ground also made from CFRP laminate. Theoretical analysis, computational simulation, and experimental measurements are conducted to investigate the effects of separation offset, laminate thickness and incident angle on the performance of a reflector manufactured from a unidirectional IM7/977-3 CFRP. The results show that this new reflector reduces the cross polarization at S-band by 13 dB while remaining a good reflector at X-band and the incident angle has minimal effect on the frequency response of the polarizer. The single reflector can support two orthogonal polarized frequencies, unlike traditional wire grid polarizer screens.
Multi-band microwave filters are important for multifunctional and miniaturization requirement of portable communication equipment. In this paper, tri-section split ring stepped-impedance resonator is analyzed, and new compact dual-band and tri-band bandpass filters are proposed by using split ring stepped-impedance resonators, and the designs are demonstrated by measurement. The new dual-band filters operate at about 2.4 and 5.5 GHz which meet IEEE 802.11 application requirements, and the new tri-band filters operate at about 2.4-2.6, 3.3-3.6 and 5.2-5.6 GHz, and filter sizes are greatly reduced compared with relative reports. The designed filters have advantages of compact and miniature structures, low passband insertion losses and good frequency selectivity, all these have prospect to be applied in wireless communication systems.
A novel 12 GHz VCO designed and fabricated in a 0.18 μm SiGe BiCMOS technology is presented. Strongly magnetic coupled dual LC tanks with fixed and tunable capacitive elements are introduced to extend tuning range and improve phase noise. By hybrid using of varactor tuning, loaded transformer tuning and switched capacitor tuning, the proposed VCO achieves a wide tuning range of 4.3 GHz (36%) and output power of -9 dBm with only 4.5 mW power consumption and only 0.17 mm2 chip area.
In this paper, a four-element microstrip antenna array is presented. The array is composed of Wilkinson power dividers which act as feed network along with Dolph-Chebyshev distribution and four-identical patch antenna elements. The array elements are properly designed to have a compact size and constant gain against frequency. The simulated results show good agreement with the measured results for the fabricated antenna array. Measurement shows that the array has a peak gain of more than 12 dBi with side-lobe level of -15 dB at 6 GHz. These characteristics make the antenna array suitable for UWB directional uses.
The design and simplified analysis of a compact and wide band (16%) negative permittivity complementary split ring resonator metamaterial is introduced. The proposed metamaterial component was applied to reduce the size of the feeding line filter of microstrip patch antenna for the sake of higher order harmonic suppression. The reduction has been done using only one element of the complementary split ring resonator, while maintaining the antenna's performance. Simplified theoretical study and design of the proposed circuits has been presented. Moreover, experimental results have been done for validation and conformation purpose. Results confirm that almost 95% of the antenna noise harmonics power has been removed.
In this paper, a novel dual planar electromagnetic bandgap (DP-EBG) microstrip structure is investigated to suppress the spurious radiation of the patch antenna. It is demonstrated that the proposed structure achieves a ultra-wide stopband and excellent passband performance within a compact circuit area. Utilizing such special features, two units of the DP-EBG structure are employed in the feed line of patch antenna with the aim of suppressing harmonics and other spurious modes. The calculated and experimental results all verify that the application of this DP-EBG structure not only drastically diminishes spurious radiations of 2nd ~ 6th harmonics in a broad frequency band, but also overcomes some shortages of other EBG microstrip antennas introduced in previous research such as large back radiation or beam squint. Besides that, by adjusting the separation between the DP-EBG structure constructed in the feed line and the patch's bottom edge in a moderate distance, the procedure for designing the EBG patch antenna working on a certain frequency with the goal of reducing spurious radiation is simplified.
This paper addresses the design and development of HiperLAN antennas meeting the IEEE 802.11a standards for wearable applications. Five such antennas are investigated for their performance characteristics, out of which three are conventional copper based antennas and the remaining two are fully fabric antennas. The results reveal that all the proposed antennas are suitable for HiperLAN applications yielding antenna gain in the order of 7-11 dBi. This study demonstrates that fully fabric antennas outperform the copper based antennas.
In this paper, a novel Metamaterial (MTM) CRLH Zeroth Order Resonance (ZOR) Circular microstrip patch antenna is proposed to have a monopole antenna pattern due to the completely closed loop of a magnetic current around the structure, and reduced profile and size due to the left-handedness. Different from other ZOR antennas of 1D periodic arrays with shorted patches, we suggest 1 circular patch capacitively coupled to 1 circular shorted ring to have ZOR and -1st resonance modes. The antenna is designed and modeled with equivalent circuits for the coaxial-fed central patch and the circular shorted ring and verified by the comparison with 3D EM simulation of the physical structure. The no-phase variation at the ZOR (2.4 GHz) and the -1st resonance mode (2 GHz) as the metamaterial properties are proven with electric field distributions and far-field patterns. The measurement shows there exist the ZOR and the -1 resonance modes despite the frequency shift from the simulation, which is proven by the monopolar radiation pattern and broadside radiation pattern, respectively. So the advantages of the proposed antenna will be addressed with the low-profile monopole at the ZOR and the size reduction effect at the -1st resonance.
This paper presents a packaged third-order transmission line based (TL-based) active bandpass filter (BPF), which is fabricated using Silterra's standard 0.18-μm CMOS 1P6M technology, with high stopband suppression. The active compensating circuit, which produces differential negative conductance, improves the quality factor (Q factor) of TL-based resonator and suppresses the spurious resonances at even-harmonic frequencies. The spurious responses are also shifted towards higher frequencies by applying a capacitively loaded TL resonator method to the filter design. Additionally, an inductive parasitic effect introduced by the package is investigated and reduced to achieve the minimum impact on the stopband suppression. Measurement results indicate that the prototype has an insertion loss of 0.95 dB at a central frequency (f0) of 1.53 GHz with a 3-dB bandwidth of 3.1%, while a current of 8 mA is consumed from 3.0 V. The stopband suppressions at 2f0 and 3f0 are 44.57 dB and 52.78 dB, respectively. Furthermore, the suppression exceeds 35 dB from 1.08f0 to 10.05f0.