Real-Life Applications of EBG Patch Antennas

High-Precision GPS

High-precision positioning can be achieved by combining global navigation satellite systems (GNSS) such as GPS and Galileo [97-99]. By using this system, surveyors can make measurements with sub-centimeter accuracy. In order to acquire such accurateness, some precautions are required to shield the antenna from false signals. The conventional approaches such as choke rings provide a good performance [100]. But, choke rings are generally very huge and expensive. Nowadays, EBG structures are used while maintaining good antenna performance.

A Galileo antenna on an EBG substrate is illustrated in Figure 11.28a. To achieve best gain for GPS applications, the dimension of the EBG structures is optimized. It is observed that with the combination of EBG substrate and patch antenna, an axial ratio of 2 dB is achieved. The axial ratio value for choke rings is 1 dB, which implies that the EBG patch has a better performance. Similarly, the patch and Koch fractal EBG structure [98] are shown Figure 11.28b. The tested results show the significant improvement in axial ratio bandwidth, which fits the requirement of GPS applications (Figure 11.29).

Wearable Electronics

Wearable electronic systems are technology that finds applications in many fields that include military, telemedicine, sports, and tracking. In [101], the jean fabric was used as a substrate having a dielectric constant of 1.7 with a thickness of 1 mm. As shown in Figure 11.29, the design consisted of a fractal monopole patch antenna with an EBG surface. This fractal antenna resonates at 1,800 MHz and 2.45 GHz for GSM and ISM applications, respectively. The antenna is placed over a 3x3 EBG array of size 150x150 mm2. Figure 11.27 illustrates the fractal-based monopole patch antenna with an EBG surface. Another researcher used a Pellon fabric substrate [102] with a dielectric constant of 1. The designed antenna consisted of a coplanar waveguide (CPW)-fed monopole antenna with an AMC array of 4x6 units, with the overall size of 102x68 mm2.

TABLE 11.6

Low-Profile Patch Antennas by Using Different EBG Structures

S. No.

Type of EBG Structure

Dimension

(cm3)

Height

(mm)

Resonating Frequency Band

Reference

1.

EBG-CS

1.65

3

Two bands (3.5 and 4.5)

[86]

2.

Miniaturized EBG structure

4.2

0.7

One band (2.4)

[88]

3.

Square Sierpinski fractal EBG structure

10.24

1.6

Three narrow bands at 2.4, 3.5. and 4.6 GHz

[87]

4.

Uniplanar EBG structure

46.4

8

One band (1.25-29)

[95]

5.

Modified EBG structure

94.8

7.9

Two bands (2-3 and 3.8-6.3)

[93]

(a) Galileo antenna on an EBG ground plane [100]; (b) circularly polarized patch antenna with fractal HIS [102]

FIGURE 11.28 (a) Galileo antenna on an EBG ground plane [100]; (b) circularly polarized patch antenna with fractal HIS [102].

(a) Dual-band wearable fractal-based monopole patch antenna [101]; (b) the fabricated monopole antenna with an artificial magnetic conductor as a ground plane [102]

FIGURE 11.29 (a) Dual-band wearable fractal-based monopole patch antenna [101]; (b) the fabricated monopole antenna with an artificial magnetic conductor as a ground plane [102].

Radio Frequency Identification (RFID) Systems

RFID systems have been used since World War II, and the demand for RFID systems is rapidly growing in both business and daily life. Currently, the RFID system is used in many applications such as hospitals and healthcare, passports, stores, and people identification. One of the biggest challenges associated with RFID systems is the long-range operation capability [103-106]. In [107], a CPW-fed bow tie antenna was mounted over an AMC. The AMCs reduce the backward radiation that results in

(a) CPW-fed bow tie antenna mounted over an AMC [107]; (b) dipole AMC [108]

FIGURE 11.30 (a) CPW-fed bow tie antenna mounted over an AMC [107]; (b) dipole AMC [108].

EBG checkerboard ground plane [109]

FIGURE 11.31 EBG checkerboard ground plane [109].

improved gain and directivity of the overall system. The antenna was fabricated using an ARLON 25 N substrate with a thickness of 0.7 mm and a relative permittivity of 3.3. Figure 11.30a illustrates the bow tie antenna over an AMC. This structure helps in the enhancement of gain by 2.53 and 1.86 dB at 5.8 and 6.4 GHz, respectively. In [108], a dipole antenna over an AMC was designed to improve the overall performance. From the tested results, it was observed that the dipole with a balun AMC achieved an improvement of 2.9 dBi as compared to the dipole without balun AMC.

Radar Systems

To reduce the radar cross section, the reflection phase property of the EBG structures is used to change the direction of the fields that are scattered by a radar target. This change in direction of the scattered fields is achieved by using checkerboard EBG structures and results in a wider frequency band RCS reduction. Figure 11.31 shows the checkerboard EBG surface which is a combination of two EBG structures.

Conclusion

The EBG structures have greatly attracted researchers because of their unique and desirable properties. This chapter stated how the integration of EBG structures and patch antennas improves the overall performance of the antenna systems. The recent advancements of patch antenna design using EBG structures were included. Different EBG approaches to improve gain and bandwidth were discussed. The band gap property of EBG structures has been found useful to eliminate the surface wave propagation to reduce the mutual coupling and to achieve band-notch characteristics. Real-life applications of EBG structures, such as RFID, wearable electronics, and radar systems, were also included. A number of recent publications proved that the EBG technology eliminates the drawbacks of patch antenna and is most preferable for the modern-day wireless communication systems.

 
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