Qingxin Guo

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.

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.

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.

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.

A small and wideband second order Koch-fractal log-periodic antenna

In this paper, a second order Koch fractal log-periodic dipole antenna (LPK2DA) with broadband is proposed. Koch iteration technique has been applied here in order to obtain a small physical size. And the overall size of the proposed antenna is 57.5×88.9×0.5 mm3. The antenna has a broadband which ranges from 2 GHz to 8 GHz. Furthermore, the antenna has end-fire radiation patterns along its horizontal axis, which is very suitable for receiving antennas and conformal applications.

Study on Available Condition of Static Circuit Parameters Applied to Predict the Transmission Characteristics of Step Microstrip Line

The static circuit parameters extracted from the field results of non-uniform microstrip line provides an efficient way to predict dynamic effect of non-uniform structure. The predictable frequency range of the static circuit parameters on prediction of the transmission characteristics of step microstrip line is researched in this paper. The circuit parameters are extracted from the full wave results of step line, respectively, at three frequencies (9 GHz, 15 GHz and 20 GHz). On one hand, the time domain transmission characteristics of step line can be solved from the equivalent circuit constructed by these extracted circuit parameters. On the other hand, the frequency domain S -parameter can be derived by the static distributed characteristic impedance. By comparing these time and frequency domain results obtained from the static circuit parameters with those obtained directly from the full wave method, the available condition of the static circuit parameters of the step microstrip line can be analyzed. This comparison shows that the static circuit parameters can be used in frequency bands from DC up to 20 GHz. To verify the accuracy of the static parameters used to predict the transmission characteristics of step line, the measured S11 is also given for comparison.

A low-profile helix array antenna designed for DBS

A low-profile array antenna composed of 2-turn helices with pitch angle of 4º is designed for the direct broadcast from satellite (DBS), it has a frequency band ranging from 11.5GHz to 13.0GHz. The antenna elements are fed by a radial waveguide in which a traveling wave in transverse electromagnetic (TEM) mode is propagating. The exciting phase of each helical element can be adjusted by rotating mechanically the element around its axis. Promising performances of the antenna are predicted theoretically first, and then the experiments are done for verifying the efficiency of the design.

Measured Performance Comparisons between Spatial Multiplexing and Beamforming Arrays in the 28 GHz Band

A spatial multiplexing (SM) array and a beamforming (BF) array with similar antenna size working at 28 GHz are designed and fabricated. In the SM array, a 4 × 4 MIMO system is realized with each port composed of a four-element subarray. In the BF array, the whole 16 elements are used to formulate a high-gain array. The measured S-parameters are in agreement with the simulated results. For both arrays, the channel capacities are computed by the measured channel matrix and signal-to-noise ratio (SNR) in an office room. Results show that capacity of the SM system is larger than that of the BF system, although the gain of BF array is about 5 dB larger than that of the SM array. However, the capacity of the SM array depends heavily on SNR; specifically, for the 1 dBm transmit power, communication distance  cm, the ergodic capacity of the SM system is 2.76 times that of the BF system, and if  cm, the capacity gain is reduced to 1.45. Furthermore, compared with the BF array, the SM array has a more robust performance over antenna misalignment, because of the wider beamwidth.