Zengrui Li

Interaction Between Internal Antenna and External Antenna of Mobile Phone and Hand Effect

In this paper, we begin by presenting a multiband antenna for mobile phone applications operating in GSM, DCS, PCS, UMTS, Bluetooth, and LTE bands. The antenna platform includes the ground plane, the battery, the camera, and other paraphernalia that the mobile phone environment typically comprises. Results show that the platform has a significant effect on the performance of the antenna, both in terms of its bandwidth and the number of its resonance frequencies. In addition, metal rings, frequently used in a mobile phone for mechanical reasons, can also have a significant influence on the performance of the antenna in the phone. Equivalent circuits and current distributions have been derived with the objective of investigating the effects of the metal ring that embrace the mobile phone. We investigate ways in which we can modify the ring so as to restore the desired performance of the antenna, which has been previously designed to operate in the phone environment but without the presence of the ring. We show how we can control the resonances of the ring by using capacitance loading and lower its Q by loading the ring resistively at a number of different strategic locations along the ring.

A Band-Notched UWB Printed Elliptical-Ring Monopole Antenna

In this paper, a compact ultra wideband (UWB) monopole antenna with a band-notched characteristic is presented. The band- notched characteristic is achieved by inserting a U-shaped slot in the half elliptical ring radiating patch. The measured bandwidth of the designed antenna for jS11j 6 i10dB spans 3.1GHz to 9.3GHz with a notched band (jS11j > i10dB) spanning 5.12GHz to 5.99GHz. A quasi-omnidirectional radiation pattern in the x-z plane and quasi- symmetrical radiation patterns in the x-y and y-z planes are obtained throughout the operating band. The antenna is suitable for UWB communication applications and also reduces the interference with wireless local area network (WLAN) systems. The parameters which afiect the performance of the antenna in terms of its frequency domain characteristics are investigated in this paper.

Ultra-wideband, Wide Angle and Polarization-insensitive Specular Reflection Reduction by Metasurface based on Parameter-adjustable Meta-Atoms

In this paper, an ultra-wideband, wide angle and polarization-insensitive metasurface is designed, fabricated, and characterized for suppressing the specular electromagnetic wave reflection or backward radar cross section (RCS). Square ring structure is chosen as the basic meta-atoms. A new physical mechanism based on size adjustment of the basic meta-atoms is proposed for ultra-wideband manipulation of electromagnetic (EM) waves. Based on hybrid array pattern synthesis (APS) and particle swarm optimization (PSO) algorithm, the selection and distribution of the basic meta-atoms are optimized simultaneously to obtain the ultra-wideband diffusion scattering patterns. The metasurface can achieve an excellent RCS reduction in an ultra-wide frequency range under x- and y-polarized normal incidences. The new proposed mechanism greatly extends the bandwidth of RCS reduction. The simulation and experiment results show the metasurface can achieve ultra-wideband and polarization-insensitive specular reflection reduction for both normal and wide-angle incidences. The proposed methodology opens up a new route for realizing ultra-wideband diffusion scattering of EM wave, which is important for stealth and other microwave applications in the future.

A Monolayer Multi-Octave Bandwidth Log-Periodic Microstrip Antenna

In this paper, a novel monolayer multi-octave bandwidth log-periodic microstrip antenna (LPMA) is presented. This antenna consists of a 50› microstrip feed-line and fourteen rectangular patch elements. Twelve rectangular patch elements are fed by edge-coupling from the microstrip feed-line and two other patch elements are directly connected with the microstrip feed-line. A mixed microstrip line feed is applied to expand the bandwidth. Our measured results closely agree with the simulated results. These results show that the proposed antenna lends itself well to operation in the impedance bandwidth from 2GHz to 8GHz with a voltage standing-wave ratio (VSWR) less than 2.

Measurement-Based Performance Comparison of Colocated Tripolarized Loop and Dipole Antennas

In this paper, a colocated tripolarized loop (TPL) antenna is proposed and a colocated tripolarized dipole (TPD) antenna is also designed for multiple-input multiple-output (MIMO) performance comparison. Both antennas have satisfactory performances of impedance bandwidth and isolation. The channel measurements are conducted in a nonlossy reverberation chamber (RC), a lossy RC, a corridor, and an office room. For both antennas, the measured average correlation coefficients (CCs) in the nonlossy RC are the smallest, close to 0.1, in the lossy RC are the largest, 0.3-0.5, and in the two indoor scenarios are slightly larger than that in the nonlossy RC. Except for the signal correlation, the relative path loss (RPL) should also be included to fairly compare the channel capacities. If the RPL is considered, a strong dependence of the channel capacity on the propagation properties can be seen. For both antennas, the channel capacities in the two indoor scenarios are 20%-30% smaller than that in the nonlossy RC. Interestingly, both antennas have similar condition numbers (CNs) in all the four scenarios, whose PDFs are close to that of the independent identically distributed (i.i.d.) complex Gaussian channel, which reveals that both antennas can obtain nearly three independent parallel subchannels and good multiplexing performance.

Fast analysis and optimal design of metasurface for wideband monostatic and multistatic radar stealth

In this paper, a metasurface (MS) is designed based on the hybrid array pattern synthesis and particle swarm optimization method for wideband monostatic and multistatic radar stealth. The non-absorptive MS is composed of two kinds of electronic band gap structures with the reflection phase difference of 180° (±37°) over a wide frequency range. Far field scattering pattern of the MS can be quickly and accurately synthetized by the method of moments and array pattern synthesis. A new strategy is proposed for realizing the diffusion reflection of electromagnetic waves by redirecting electromagnetic energies to more directions through optimizing the reflected phase arrangement for the MS by hybrid array pattern synthesis and particle swarm optimization algorithm. Due to the non-uniform distributions of phase gradient between neighboring lattices, numerous scattering lobes are produced in the upper half-space, leading to a great reduction of bistatic radar cross section (RCS). The −10 dB RCS reduction bandwidth of 80.2% is achieved for both monostatic and bistatic at normal incidence. The specular reflection and bistatic scattering for oblique incidence with TE and TM polarizations are also considered in detail. The measured results are in good agreement with the corresponding simulations.

Design of high performance sleeve dipole array antenna

A 5-element planar dipole array antenna is analyzed and successfully implemented. The proposed antenna is designed for operation at 1.9 GHz band for basic station applications with S11< −14 dB. The planar dipole array antenna comprises of a 1×5 dipole array and fed by a microstrip line. This structure is easily constructed by printing on both sides of a dielectric (FR4) substrate. The measured −14 dB return loss (VSWR 1.5:1) impedance bandwidth is around 7.0% (1.79–1.92 GHz). A reflector is put behind the dipole array to obtain directional radiation and high gain, and the measured maximum gain for operating frequencies across the 1.9 GHz band is about 6.9–8.6 dBi. The measured results of radiation efficiency, radiation pattern, antenna gain and return loss show that this dipole array is with a good performance.

A Wideband End-Fire Conformal Vivaldi Antenna Array Mounted on a Dielectric Cone

The characteristics of a novel antipodal Vivaldi antenna array mounted on a dielectric cone are presented. By employing antipodal Vivaldi antenna element, the antenna array shows ultrawide bandwidth and end-fire radiation characteristics. Our simulations show that the cone curvature has an obvious influence on the performance of the conformal antenna, in terms of both the bandwidth and the radiation patterns. The thickness and permittivity of the dielectric cone have an effect on the bandwidth of the conformal antenna. Measurement results of both single antenna and conformal antenna array show a good agreement with the simulated results. The measured conformal antenna can achieve a −10 dB with bandwidth of 2.2–12 GHz and demonstrate a typical end-fire radiation beam. These findings provide useful guidelines and insights for the design of wideband end-fire antennas mounted on a dielectric cone.

An original Vivaldi antenna for 1–8GHz wideband application

A tapered slot Vivaldi antenna, which is fed by a microstrip-slot balun for 1-8GHz Wideband application is presented. The measured bandwidth of the proposed antenna for |S11| ≤-10 dB spans 0.9GHz to 9.6 GHz. The endfire radiation patterns in the x-y and y-z plane are obtained through the operating band from 0.9GHz to 5.8GHz. The antenna peak gain is 6.3 dB and measured gain is larger than 3.15 dB from 0.9GHz to 6GHz, however, the gain has a sharp decline at 8GHz. The structure and parameters of the Vivaldi antenna is designed and simulated.

Study of the Colocated Dual-Polarized MIMO Capacity Composed of Dipole and Loop Antennas

The colocated dual-polarized dipole (DPD) and dual-polarized loop (DPL) MIMO channel performances are compared. Computation results show that, for the ideal electric and magnetic dipoles, the dual-polarized MIMO systems have identical channel capacity. But the contour plots of the capacity gain of the realistic DPD and DPL are different, due to the difference in antenna patterns. The cumulative distribution function (CDF) of the capacity gain in the two-mirror (TM) channel shows that, for small distance, the capacity gain obtained by the DPD is obviously smaller than that of the DPL, but, with the increase of the distance, the difference gets smaller. A DPL with low mutual coupling is fabricated. Measured results show that high MIMO capacities can be obtained by this DPL in both the anechoic chamber (AC) and the realistic office room. The capacity gain of the DPL antenna is 1.5–1.99, which basically coincides with the theoretical and numerical results. Furthermore, the capacity of the virtual DPL antenna with no mutual couplings is also investigated. It is shown that, in the AC, the mutual coupling will generally decrease the dual-polarized MIMO capacity; however, in the office room, the effect of mutual coupling is not always negative.