Typical wireless systems, including mobile phones, are as follows:

Mobile phones

GSM 850 (850 MHz band),

GSM 900 (900 MHz band),

GSM 1800 (1.8 GHz band),

GSM 1900 (1.9 GHz band),

UMTS (Universal Mobile Telephone Systems) (2 GHz band),

LTE (Long Term Evolution) (700 MHz, 2.3 GHz, and 2.5 GHz bands)

Wireless systems

Bluetooth (2.4 GHz band),

WiFi (IEEE 802 11 a/g/n: 2.4 and 5 GHz bands),

WLAN (IEEE 802.11 b: 2.45/5.2/5.8 GHz),

WiMAX (Fixed: IEEE 802 16 2004: 3.5 and 5.8 GHz bands and

Mobile: IEEE 802 16e: 2.3, 2.5, and 3.5 GHz)

GPS (1.5 GHz band)

Various types of multiband microstrip patch antennas composed with various shapes combined with slots/slits embedded on the patch surface have so far been introduced. In this section, however, antennas for operating at more than two bands will be described.

8.1.2.1.2.1.1 A printed λ/8 PIFA operating at penta-band

A PIFA is designed to operate at one-eighth (λ/8) wavelength as the fundamental resonance mode for applying to WWAN (Wireless Wide Area Network) system [16]. The antenna is installed in a mobile phone, having a simple structure comprised of two radiating strips of length about λ/8 at 900 MHz. The configuration generates two λ/8 modes to cover two lower modes for operation of GSM 850/900, and at the same time, two higher-order modes or λ/4 modes at about 1900 MHz to operate at a wider upper band for GSM 1800/1900/UMTS. The antenna geometry is illustrated in Figure 8.35, in which dimensional parameters are given. The antenna covers penta band, yet occupies only a small printed area of 15 mm × 31 mm or 465 mm2. The antenna is fed using a coupling feed, by which the ordinarily large input impedance of a traditional λ/8 mode PIFA is greatly reduced, and successful excitation of the λ/8 mode for a PIFA is achieved. Measured and simulated return-loss characteristics are depicted in Figure 8.36.

8.1.2.1.2.1.2 Bent-monopole penta-band antenna

A metal-wire bent-monopole antenna (BMA) fed by mini-coaxial cable jointly with a thin printed ground line demonstrates that it operates at penta-band: CDMA, GSM, DCS, PCS, and WCDMA bands [17]. The antenna geometry is illustrated in Figure 8.37, which shows (a) antenna geometry and its feed point, (b) frontand back-side views of PCB (Printed Circuit Board). The feed and ground points are connected to a 50coaxial cable (10 cm long) with an SMA connector. The dimensions of the BMA are a = 38, b = 40, and c = 6 (in mm), and the radius and the length, respectively, of the feeding mini-coaxial cable are 1.13 and 46 mm, which is put tightly on the BMA to serve as a reactive loading. The effect of the reactive loading is reduction of the electrical

Figure 8.35 (a) Geometry of printed λ/8-PIFA for penta-band operation and (b) dimensions of PIFA pattern ([16], copyright C 2009 IEEE).

Frequency (MHZ)

Figure 8.36 Measured and simulated return loss ([16], copyright C 2009 IEEE).

Frequency (MHz)

Figure 8.38 Measured and simulated return-loss characteristics ([17], copyright C 2011 IEEE).

1880 MHz, respectively, and in the x–z plane (horizontal plane), 0.7 dBi and 2.07 dBi for 960 MHz and 1880 MHz, respectively.

Addition of a printed thin ground line behind the antenna contributes to increasing the bandwidth at both lower and higher bands, also providing an effect to form a balancedfeed structure like a sleeve balun, because of its length being nearly λ/4 at 1800 MHz, allowing a short circuit at the base to present an infinite impedance at the top.

The balanced feed to a balanced antenna is useful to reduce the current flow on the ground plane so that the operator’s hand effect on the antenna performance can be mitigated.

8.1.2.1.2.1.3 Loop antenna with a U-shaped tuning element for hepta-band operation

The printed loop antenna is designed to cover GSM 850/900/DCS/PCS/UMTS and WiMAX, with a U-shaped tuning element printed on the back side of the circuit board when applied to a laptop computer [18]. The antenna geometry is illustrated in Figure 8.39, which shows (a) 3D view, (b) plan view of the front side, and (c) plan view of the back side. The antenna is printed on an FR4 substrate with thickness of 0.8 mm, εr = 4.4, and mounted on the top right corner of a vertical ground plane of size 200 × 160 mm, which is the supporting metal frame of an LCD panel. The antenna measures only 65 × 10 × 0.8 mm, because it is coated on double sided PCB. The U-shape on the back side is a tuning element, which is affixed to the ground plane. Measured and simulated reflection coefficients are shown in Figure 8.40. The results exhibit bandwidth for –6 dB reflection coefficient 140 MHz (820–960 MHz) in the GSM band and 1190 MHz (1710–2900 MHz) in the DCS/PCS/UMTS bands. It also shows that –10 dB bandwidth is sufficient for WLAN and WiMAX applications. Radiation patterns are similar to that of a monopole. Table 8.4 gives average gain, peak gains, and efficiency for five frequency bands.