Sompol Kosulvit

TWO-PROBE EXCITED CIRCULAR RING ANTENNA FOR MIMO APPLICATION

This paper presents the analysis and design of a two-probe excited circular ring antenna. The analysis is conducted by using induced emf method and transmission line model. The design process is to choose a suitable radius of the ring for a single probe antenna. Then, the suitable probe length and ring length are determined for the two- probe antenna. Finally, isolation between the two probes is enhanced by insertion of an inductor coil between the probes. The operational characteristics of the prototype antenna at the frequency of 5.2GHz are measured and compared with calculation results. It is evident that these results are in good agreement. The antenna achieved isolation in excess of 20dB and VSWR less than 2 : 1 over the desired bandwidth and a bidirectional radiation pattern with 4dBi gain. This antenna is suitable for Multiple-Input Multiple-Output (MIMO) system covering a long and narrow environment.

5.8 GHz Notched UWB Bidirectional Elliptical Ring Antenna Excited by Circular Monopole with Curved Slot

This paper presents a UWB bidirectional elliptical ring antenna excited by circular monopole with curved slot for 5.8 GHz band rejection. High Q operation of band notch is obtained in the simulation. The characteristics of the antenna have many attractive features in both technically and economically, such as bidirectional radiation pattern, wide impedance bandwidth, moderate gain, small size, low cost, and easy fabrication. The antenna is desired for application in conventional narrow and long path service area, where some frequency bands pre-occupied by the WLAN standard IEEE 802.11a.

Polarization reconfigurable suspended antenna using RF switches and P-I-N diodes

Polarization reconfigurable square flat antenna using RF switches and P-I-N diodes is presented for WLAN application operated at the center frequency of 2.45 GHz. The proposed antenna consists of the square flat structure, three switches (six P-I-N diodes), transmission-line phase shifters of 0 and 90 degrees. The antenna can be switched between 5 different states: vertical, horizontal and slant polarizations for linear polarization (LP), left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) by controlling the DC bias of 5 V and the current of 16 mA for the P-I-N diodes. The simulated and measured results show that the proposed antenna can cover the impedance bandwidth from 2.400 GHz to 2.484 GHz and good axial ratio for the circular polarization.

Radiation characteristics of a bidirectional antenna using a linear probe in a rectangular ring

This paper reports the radiation characteristics of a low cost and simple structure bidirectional antenna by using a linear probe in a rectangular ring. The radiation pattern is obtained from the Fourier transformation of the aperture field which is derived from the field inside the ring by using Greens function. From the numerical result of the radiated field, for a specific ring dimension, the optimum length which provides the maximum directivity are calculated and chosen as a design parameter. Experimental results, verifying the bidirectional radiation, agree very well with the computational result.

Unidirectional antenna using two-probe excited circular ring above square reflector for polarization diversity with high isolation

This paper presents a circular ring antenna fed by two perpendicular probes, both of which are placed above the square re∞ector. The antenna is employed to radiate unidirectional beam for polarization diversity reception. A linear isolator is added to improve the isolation between the two probes. The antenna is proposed for the point-to-point communication of Wireless Local Area Network (WLAN) system according to the IEEE 802.11a standard in which the allocated frequency band ranges from 5.150GHz to 5.825GHz. The proposed antenna is compact and suitable for mass production. Without the dielectric material, the antenna is free of dielectric loss and capable of high power handling. The prototype antenna was fabricated and measured to verify the theoretical predictions. At the center frequency, the unidirectional pattern with the measured half-power beamwidths in two principal planes of 65 and 75 degrees is achieved. The front-to-back ratio is 31dB, and the antenna gain is 7.42dBi. The jS11j and jS21j are respectively i23:09dB and i33:99dB; the obtained bandwidth is 23.64%. Based on the aforementioned characteristics, the antenna is a potential candidate for polarization diversity of WLAN applications.

Mutual Information of MIMO System in a Corridor Environment based on Double Directional Channel Measurement

Double directional channel measurements were made in a corridor environment with a channel sounder. A multidimensional high resolution algorithm was used to extract channel parameters for calculating the mutual information of a special Multiple-Input Multiple-Output (MIMO) system. This system utilized bidirectional dual-polarized antennas at both ends of the communication. In a corridor environment, the mutual information of this system was 12 b/s/Hz higher than that of the other MIMO system equipped with traditional 1λ horizontally-spaced vertically-polarized dipole array antennas. Depolarization of the vertical polarization transmission degraded the mutual information of the dipole array antennas in this environment. The angular spread of the incoming signals at the receiver ranged from 0.9° to 3.8° depending on the distance between the transmitter and the receiver.

Design of a compact biconical antenna for UWB applications

This paper presents the study, design, fabrication, and measurement of a vertically polarized compact biconical antenna that can be used as a reference antenna. The study from simulation results suggest that the optimal antenna shall have the flare angle of 60° which gave the most stable vertical beamwidth in the broadside direction and the fewest ripples in the main beam region, a cone length of one wavelength of center frequency (7 GHz) to make the antenna most compact, and the feed gap was 0.5 mm. The return loss was −10 dB on average across the bandwidth. The simulation results were validated by the experiments. The fabricated antennas worked across 2–12 GHz as desired, and were used as reference antennas especially for UWB 3.1–10.6 GHz applications.

An Ultra-Wideband Bidirectional Antenna with Modified Circular Disc Monopole Excited Elliptical Ring

The antenna design for ultra-wideband (UWB) signal radiation is one of the main challenges of the UWB system, especially when the antenna can satisfy the requirement of low-cost, compactness, linear polarization and bidirectional pattern. This paper proposes a UWB bidirectional antenna with introducing the psi shape feeder to circular disc monopole (CDM) excited elliptical ring for modern base station in UWB system. The simulation results are presented UWB performance of this antenna by using Computer Simulation Technology (CSTreg). The return loss of better than 10 dB covers the frequency range from 3 to 25 GHz, directivity at the direction toward thetas = 0deg and 180deg from 2.8 dBi at 3 GHz to 4.6 dBi at 11 GHz. The proposed antenna can achieve bidirectional pattern over the bandwidth of 7.5 GHz. The bidirectional radiation pattern is desirable for many applications in long and narrow path service cell

Characteristics of an elliptical ring antenna excited by a linear electric probe

This paper presents the characteristics of an elliptical ring antenna excited by a linear electric probe. Based on the waveguide principle, the suitable cross-sectional dimension of the ring that yields the dominant mode (TEC11 mode) will be formulated in terms of the cut off wavelength. The variation of the antenna characteristics, depending on cross-sectional dimension, ring length and probe length, were investigated using numerical electromagnetic code (NEC) based on the method of moments (MoM). From the experiment, the prototype antenna provides bidirectional pattern with HPBW in E-plane and H-plane of 83 and 46 degrees, respectively, and the gain of 5.1 dBi with SWR < 2:1 over the bandwidth of 14% for the operating frequency of 1.92 GHz. This antenna is applicable for mobile communication on a highway, on a street, in a corridor and in a tunnel with the advantages of simple configuration and low cost.

A wideband bidirectional antenna using truncated circular sector fed by rectangular monopole

This paper presents a wideband bidirectional antenna using rectangular monopole with trident to excite truncated circular sector. The antenna is designed for wideband operation, especially when the antenna can satisfy the requirement of low-cost, linear polarization and bidirectional pattern. The simulation results are presented the wideband performance of this antenna. The return loss better than 10 dB covers the frequency range from 4 to 11 GHz, and the directivity at the direction toward θ = 0° and 180° is 4.03 dBi to 8.23 dBi from 4 to 11 GHz. The proposed antenna obtains bidirectional radiation pattern.