Fa-Shian Chang

Low-cost broadband circularly polarized patch antenna

A novel single-feed broadband circularly polarized patch antenna is proposed. The proposed antenna has a simple structure, consisting of a corner-truncated square radiating patch, an L-shaped ground plane, and a probe feed. Through a via hole in the vertical ground of the L-shaped ground plane, the radiating patch is easily excited by a probe feed oriented in the same plane as the patch, and circular polarization (CP) radiation over a wide frequency range (>10%) is achieved. Experimental results of a constructed prototype with the center operating frequency at about 2500 MHz showed that the antenna has an impedance bandwidth (1.5:1 VSWR) of about 30%, a 3-dB axial-ratio CP bandwidth of about 10.4%, and a gain level of 8.5 dBi or larger within the CP bandwidth. In addition to the low cost of the proposed antenna due to its simple structure, the obtained CP performance is among the best that have been reported for single-feed single-element patch antennas.

Low-cost broadband circularly polarized probe-fed patch antenna for WLAN base station

Operation with CP (circular polarization) requires no strict orientation between the transmitter and the receiver for wireless communications, and is very suitable for applications in wireless local area network (WLAN) to overcome multipath fading problems and enhance system performance. However, for practical applications in the 2.4 GHz WLAN band (2400-2484 MHz), a wide CP bandwidth (larger than about 3.5%) is required. For this purpose, we demonstrate a novel and simple broadband circularly polarized patch antenna comprising a corner-truncated square patch, an L-shaped ground plane, and a single probe feed. The proposed antenna can be easily constructed at low cost, and have an impedance bandwidth (1:1.5 VSWR) of about 30%, a CP bandwidth (3 dB axial ratio) of about 10.4% and a gain level of 8.5 dBi or larger within the CP bandwidth. The obtained CP performance is among the best that have been reported for single-feed single-element patch antennas.

Compact printed band-notched ultra-wideband slot antenna

We present a compact printed circular wide slot antenna having an UWB operating bandwidth with a band-notched frequency band at 5 GHz. The band-notched operation is achieved by using a U-slotted circular stub for the antenna. It is found that by adjusting the length of the U-slot cut in the circular stub to be about a half-wavelength at the desired notched frequency, a destructive interference can take place, causing the antenna to be non-responsive at that frequency. Details of the proposed antenna are described, and results for a constructed prototype are presented.

Novel design of printed monopole antenna for WLAN/WiMAX applications

In recent years, wireless communications have progressed very rapidly. Wide-band antenna and multi-band antenna designs have become very important for wireless communications. Several promising monopole antennas for WLAN and WiMax applications have been reported recently. According to the WiMax protocol, there is three bands have been allocated for WiMax application: the lower band is 2.5-2.69 GHz, the middle band is 3.3-3.8 GHz, and the higher band covers from 5.25 GHz to 5.85 GHz. In practical use of WiMax applications, the lower band and the middle band are very close to each other, which lead to cause large effects of coupling and interference. To reduce the coupling and interference between the lower and middle bands, filters must be attached to the antenna to suppress the dispensable bands. However, the cost and the overall antenna size are increased due to the attached filters. In this paper, a CPW-fed printed monopole antenna for dual-band operation of 2.3-4.15 GHz and 4.93-5.83 GHz are proposed. Furthermore, by etching a pair of slits on the proposed monopole antenna, band rejection of frequency range from 2.93 GHz to 3.12 GHz can be achieved. Results show that, this novel design of CPW-fed monopole antenna is suitable for both WLAN and WiMax applications.

Folded meandered-patch monopole antenna for triple-band operation

The meandered patch is generally formed by cutting several linear slits in a planar conducting patch to meander the excited patch surface current path. The meandered patches are generally in planar structures. We demonstrate a novel antenna design utilizing a meandered patch folded into a compact three-dimensional structure. The proposed antenna is suitable for applications in mobile phones for GSM (global system for mobile communication, 890-960 MHz), DCS (digital communication system, 1710-1880 MHz) and PCS (personal communication system, 1850-1990 MHz) triple-band operations. In addition, owing to the proposed folding design, the antenna height is greatly reduced (to 8 mm) and can be mounted on top of a grounded substrate with a distance of 7 mm, leading to a low profile of only 16 mm (about 4.2% of the wavelength at 900 MHz) from the ground plane. This characteristic makes it very promising for the proposed antenna to be placed within the mobile phone housing, leading to a concealed mobile phone antenna.

Dual-polarized probe-fed patch antenna with highly decoupled ports for WLAN base station

In this paper we present a novel dual-polarized patch antenna using two probe feeds for achieving high port decoupling. By using a thick air-layer substrate, which makes possible a wide impedance bandwidth. The two probe feeds have a short probe pin and a triangular transition patch (F.S. Chang and K.L. Wong, Microwave Opt. Technol. Lett. vol. 30, pp. 341-343, 2001), which makes good impedance matching over a wide frequency range very easy to obtain. In addition, an additional shorted inverted-L patch is added, which is for the purpose of decreasing the excited patch surface currents flowing from the excited port toward the other one, such that great improvement in port decoupling can be obtained. Details of the proposed design are described, and a prototype suitable for the dual-polarized WLAN base-station application at 2.45 GHz band (2400-2485 MHz) is constructed and studied.

A novel broadband antenna for WLAN applications

This paper presents a novel monopole antenna backed by a U-shaped ground plane and broadside radiation for broadband dual-frequency operation. By varying the angle of inclined ground plane, dual-band operation with its operating mode center at about frequency 2.4GHz, 5.2GHz and 5.8GHz have been obtained. Good broadside radiation characteristics for the proposed antenna have also been observed.

A broadband probe-fed patch antenna with a thickened probe pin

Broadband operation of a planar patch antenna fed by a novel probe feed with a thickened probe pin is demonstrated. With such a probe feed used, the impedance bandwidth of a planar patch antenna with a thick air-layer substrate can be significantly enhanced. Prototypes with an impedance bandwidth (1:1.5 VSWR) suitable for applications in a DCS cellular system (1710-1880 MHz) base station have been successfully constructed and studied. Experimental results are presented and discussed.

A low-profile folded monopole antenna for GSM/DCS mobile phone application

A novel planar monopole consisting of a single patch, a tuning flat and wrapped into a compact structure with a height of 6 mm for 900 and 1800 MHz operations is presented. The proposed antenna has two separate wide bandwidths covering the required bandwidths of the GSM (880-960 MHz) and DCS (1710-1880 MHz) bands. In addition, the proposed antenna is lightweight and can easily be constructed by folding a planar monopole made of a copper plate. Good radiation characteristics of the proposed antenna have also been observed.

A broadband probe-fed patch antenna

The use of a probe feed has been the simplest way in exciting microstrip patch antennas. However, for microstrip patch antennas with a thick dielectric or air-layer substrate for broadband operation, the use of a conventional probe feed will require a long probe pin inside the thick substrate layer, and good impedance matching over a wide frequency range will become difficult to achieve. The proposed probe-fed patch antenna can have a thick air-layer substrate for broadband operation, and by using a triangular conducting patch of a suitable flare angle placed at one of the patchs radiating edges, good impedance matching over a wide frequency range can be obtained by using a conventional probe feed with a short probe pin. Based on the proposed design, many prototypes have been constructed, and an impedance bandwidth (1.5:1 VSWR) of about 10% can easily be obtained. A prototype whose impedance bandwidth meets the bandwidth requirement (1710-1880 MHz) of the DCS cellular system has also been implemented.