**Abstract**

In this chapter, a review has been presented on dual-band, multiband, and ultra-wideband (UWB). This review has been classified according to antenna feeding and loading of antennas using slots and notch and coplanar structure. Thereafter a comparison of dual-band, multiband, and ultra-wideband antenna has been presented. The basic geometry of patch antenna has been present along with its equivalent circuit diagram. It has been observed that patch antenna geometry for ultra-wideband is difficult to achieve with normal structure. Ultra-wideband antennas are achieved with two or more techniques; mostly UWB antennas are achieved from coplaner structures.

**Keywords:** dual-band, multiband, ultra-wideband, microstrip patch

### **1. Introduction**

Antenna is a device that is used to transmit and receive the information in the form of electromagnetic waves only. Antenna is generally classified according to the frequencies, low-frequency, medium-frequency, and high-frequency antenna. Firstly, low-frequency antenna was proposed by a German physicist H. Hertz, i.e., a dipole antenna; thereafter it took 20 years to practically install this antenna. Marconi preformed an experiment on half-wave dipole to transmit the information from Atlantics and received successfully at the receiver side, i.e., St. John's Newfoundland. It was Marconi who used the theory of Prof. J.C. Bose for successful transmission of information. Later, J.C. Bose was known for his contributions on horn antennas. These transmissions of signal were limited to a 200-m distance, and after that De Forester and Felleming developed vacuum tubes; this leads to the increase in transmission distance till 600 m. This enhances the role of electrical and electronics devices for long-distance communications. Then medium-frequency antenna ranges from 300 to 3000 KHz which was designed in the late 1920s. This antenna was constructed using steel bar supported via wooden bars. Later on all lots of development gone till the 1960s for the improvement of medium-frequency antenna, and various antennas were proposed that satisfied this ranges. Highfrequency antennas range from 0.003 to 40 GHz after that it is millimeter waves. High-frequency antennas are aperture antenna (pyramidal horn, circular horn, rectangular waveguide), antenna array (linear or planar arrays) and reflector

antennas (parabolic reflectors with horn fed or Cassegrain feed, lens antenna, and microstrip antennas (MSAs)) which comprise of a circular, rectangular, or square conducting patch that is made of grounded substrate. This chapter is focused on the miniaturized high-frequency devices so that it can be used in compact wireless communication devices.

In view of this, high-frequency patch antennas devices are introduced, and an extensive literature survey is performed. High-frequency MSAs are the antennas in which dielectric substrates are between the radiating patch and ground plane [1] and are shown in **Figure 1** along with its equivalent circuit diagram. Patch antenna at high frequency is represented as a parallel combination resistance *R*1, capacitance *C*1, and inductance *L*1. The value and equations of *C*1, *R*1, and *L*<sup>1</sup> [1] vary depending

**Figure 1.** *Configuration of microstrip antenna and its equivalent circuit diagram.*

on the shape and size of antennas. Patch antennas can be of any shape [1] and size, as shown in **Figure 2**. **Figure 2** shows different types of existing geometry of antennas such as square, rectangular, circle, elliptical, triangular, sectorial, angular ring, semicircular, and square ring. First microstrip patch antenna was reported by Deschamp [2] in 1953. High-frequency microstrip patch antennas generally are divided according to the frequency bands, i.e., dual-band, multiband, broadband, and ultra-wideband (UWB) [3–5]. To achieve these frequency bands, antennas of different shapes and sizes have been presented. In the next section, these frequency bands are discussed with respect to their shape, size, and feeding techniques. From **Figure 1** the input impedance of patch can be written from its equivalent circuit as

*A Review: Circuit Theory of Microstrip Antennas for Dual-, Multi-, and Ultra-Widebands*

*Zp*<sup>1</sup> <sup>¼</sup> <sup>1</sup> 1

*DOI: http://dx.doi.org/10.5772/intechopen.91365*

**2. Dual-band MSAs**

**2.1 Slot loaded MSAs**

**Figure 3.**

**107**

*Top view of slot loaded MSAs and its equivalent circuit diagram.*

*<sup>j</sup>ωL*<sup>1</sup> <sup>þ</sup> *<sup>j</sup>ωC*<sup>1</sup> <sup>þ</sup> <sup>1</sup>

*R*1

ent techniques such as stacking, coplanar structures (parasitic patches), slots, notches, shorting pin, shorting wall and active devices, etc. Using these techniques several research papers were published by various researchers, and the first dualband radiator was reported in 1984, using shorting pins in rectangular patches by Wang and Lo [6]. In this section, literature survey of dual-band and multiband is

presented on the basis of techniques used to achieve dual or multiband.

1 *Zps*

Dual-band and multiband microstrip patch antenna can be realized with differ-

Slot loaded MSAs can be achieved by etching rectangular or slot of any desired

The slotted loaded MSAs proposed by various researchers are summarized here. Daniel and Shevgoankar [7] studied rectangular microstrip patch antenna with the slot etched along with the nonradiating edge of the patch antenna for tunable dual-band operation and investigated the effects of the slot parameter on the tuneableness of the RMSA resonant frequencies. Wu [8] demonstrated compact slot loaded triangular patch antenna for wireless application and measured gain as 2.8

shape in the patch as shown in **Figure 3**. This antenna can be represented as a parallel combination of impedance due to patch (*Zp*1) and impedance due to slot (*Zsh*), and its equivalent is denoted as (*Zps*), as given in **Figure 3** and calculated as,

> ¼ 1 *Zp*<sup>1</sup> þ 1 *Zsh*

<sup>¼</sup> *<sup>j</sup>ωL*2*R*<sup>1</sup>

*jωL*<sup>2</sup> � *ω*2*L*1*C*1*R*<sup>1</sup> þ *R*<sup>1</sup>

, (1)

, (2)

**Figure 2.** *Different shapes of radiating patches.*

*A Review: Circuit Theory of Microstrip Antennas for Dual-, Multi-, and Ultra-Widebands DOI: http://dx.doi.org/10.5772/intechopen.91365*

on the shape and size of antennas. Patch antennas can be of any shape [1] and size, as shown in **Figure 2**. **Figure 2** shows different types of existing geometry of antennas such as square, rectangular, circle, elliptical, triangular, sectorial, angular ring, semicircular, and square ring. First microstrip patch antenna was reported by Deschamp [2] in 1953. High-frequency microstrip patch antennas generally are divided according to the frequency bands, i.e., dual-band, multiband, broadband, and ultra-wideband (UWB) [3–5]. To achieve these frequency bands, antennas of different shapes and sizes have been presented. In the next section, these frequency bands are discussed with respect to their shape, size, and feeding techniques. From **Figure 1** the input impedance of patch can be written from its equivalent circuit as

$$Z\_{p1} = \frac{1}{\frac{1}{j\alpha L\_1} + j\alpha C\_1 + \frac{1}{R\_1}} = \frac{j\alpha L\_2 R\_1}{j\alpha L\_2 - \alpha^2 L\_1 C\_1 R\_1 + R\_1},\tag{1}$$
