Seven‐band surface‐mount loop antenna with a capacitively coupled feed for mobile phone application

Abstract

conical beam patterns was characterized and verified with measurements and shown to have acceptable axial ratio. The present antenna design can be used as a good candidate for applications in short-range wireless communication systems, particularly wireless sensor networks, where the conical beam will give advantages of energy saving and reduced co-channel interference. Other applications could include indoor WLAN antennas for mounting on ceilings or other horizontal surfaces. Recently, a variety of multiband loop antennas for wireless wide area network (WWAN) operation in the mobile phone have been demonstrated [1][2][3][4][5][6][7]. These loop antennas are attractive for mobile phone applications in part, because their excited surface current paths are in a closed form, which is different from the conventional mobile phone antennas such as the monopoles or planar inverted-F antennas (PIFAs), whose excited surface current paths are in an open form [8]. Hence, the possible coupling between the loop antenna and the system ground plane of the mobile phone can be much smaller than that of the conventional mobile phone antennas. In this case, the variations in the dimensions of the system ground plane will show smaller effects on the performances of the loop antenna. For the reported multiband loop antennas for mobile phone applications [1][2][3][4][5][6][7], most of them use a direct feed, and the obtained operating bands cover several of the GSM850 (824 -894 MHz), GSM900 (890 -960 MHz), GSM1800 (1710 -1880 MHz), GSM1900 (1850 -1990, and UMTS (1920( -2170 bands for WWAN operation. In this article, we present a surfacemount loop antenna with a capacitively coupled feed for achieving seven-band operation covering all the five operating bands for WWAN operation, the 2.4-GHz band (2400 -2484 MHz) for wireless local area network (WLAN) operation, and the 2.5-GHz band (2500 -2690 MHz) for worldwide interoperability for microwave access (WiMAX) operation [9 -15]. That is, WWAN/WLAN/ WiMAX multinetwork operation can be achieved for the proposed antenna. SEVEN-BAND SURFACE-MOUNT LOOP ANTENNA WITH A CAPACITIVELY COUPLED FEED FOR MOBILE PHONE APPLICATIONThe capacitively coupled feed applied in the proposed loop antenna comprises a coupling strip and a tuning strip, which is different from the conventional capacitive feed that has been studied for internal mobile phone antennas [5, 16 -18]. The conventional capacitive feed mainly has a coupling strip or coupling portion only, and with the capacitive feed, widened bandwidth in the lower band (900 MHz band) of the antenna [16] or reduced size of the antenna [17,18] has been demonstrated. In [5], by using a coupling stub as the capacitive feed, two wide operating bands are achieved to cover GSM850/900/1800/1900 quad-band operation for the loop antenna with an occupied volume of 3.4 cm 3 .In the proposed design, the loop antenna is formed by mounting a meandered loop strip onto the surfaces of a foam base of 60 ϫ 10 ϫ 3 mm 3 (1.8 cm 3 ) only. The antenna is then surface-mounted ...

Very compact coupled fed loop antenna for 2.4‐GHz WLAN applications

“…The technique of utilizing the coupling feed for feeding the loop antennas has been reported very recently [1][2][3][4][5]. Generally speaking, two types of loop configurations are found among these studies.…”

“…The first type is of an open-loop structure, which has one end open and set close to a coupling feed, whereas the other end of the loop grounded, with a driven coupling element and a coupled strip to form a virtual continuous loop through the capacitive coupling [1,5]. The second type is a close-form loop that has its both ends short-circuited to the system ground and is capacitively excited by a driven coupling element encircled by the loop strip [2][3][4]. These aforementioned loop designs were mainly aimed at mobile/PDA-phone applications and must required a relatively large system/antenna ground plane to properly excite the antenna in the case of either the antenna as a matching element (e.g., unbalanced 0.5-and 1.5-wavelength loops) to couple to the ground-plane resonance or the antenna to be the main radiator (e.g., balanced 1.0-wavelength loop) [6].…”

Compact coupled-fed printed antenna for eight-band WWAN/WLAN/ WiMAX internal mobile phone

“…Recently, a multiband antenna operating in WWAN/WLAN/WiMAX bands in the internal mobile phone is also demonstrated in [6], while it is three-dimensional and need to load a chip inductor. Internal multiband loop antennas have also been presented in [13,14], yet they are both three-dimensional and not easy fabrication.…”

“…To achieve small size, ease of fabrication, and wideband operation, the on-board printed internal antennas such as the capacitively coupled-fed antennas [1,2], monopole antennas [3] and slot antennas [4] are attractive for the modern thin mobile phone applications. Various designs of wideband antennas [5][6][7][8][9][10][11][12][13][14] with printed structure or 3-D structure have been recently proposed to cover the WWAN, WLAN or WiMAX operation required by modern mobile devices.…”

Low-profile penta-band monopole antenna for mobile communication applications

“…Many works regarding the antennas with above features have been reported [1]- [6]. Among the available methods of reducing antenna size, one effective way is to meander the strips, and this method has been used in many promising designs [2]- [4], [7].…”