**9. Microstrip antennas**

Microstrip antennas are printed on a on a dielectric substrate with low dielectric losses. Cross section of the microstriop antenna is shown in **Figure 10**.

Microstrip antennas are thin patches etched on a dielectric substrate εr. The substrate thickness, H, is less than 0.1λ. Microstrip antennas are widely presented in [1–18].

Advantages of microstrip antennas:


**Figure 10.** *Microstrip antenna cross section.*

Disadvantages of microstrip antennas:


The electric field along the radiating edges is presented in **Figure 11**. The magnetic field is perpendicular to the electric field according to Maxwell's equations. At the edge of the strip (X/L = 0 and X/L = 1), the magnetic field drops to zero, because there is no conductor to carry the electromagnetic current, it is maximum in the patch center. The electric field is at maximum level (with opposite polarity) at the patch edges (X/L = 0 and X/L = 1) and zero at the patch center. The ratio of electric to the magnetic field is proportional to the impedance that we measure when we feed the patch. Microstrip antennas may be fed by a microstrip line or by a coaxial line or probe feed. By varying the location of the antenna feed point between the patch center and the patch edge, we can get a 50 Ω impedance or any other desired impedance. Microstrip antenna may have any arbitrary shape such as square, triangle, circle, ring, rectangular, and fractal shape as presented in **Figure 12**.

The antenna dimension W is given by Eq. (17). The antenna bandwidth is given in Eq. (18).

$$W = \frac{c}{2\xi\sqrt{\varepsilon\_{\text{eff}}}}\tag{17}$$

$$BW = \frac{H}{\sqrt{\epsilon\_{\text{eff}}}} \tag{18}$$

**Figure 11.** *Rectangular microstrip antenna.*

**Figure 12.** *Microstrip antenna shapes.*

**Figure 13.**

*MM wave microstrip antenna array. (a) Parallel array feed network. (b) Parallel-series array feed network.*

The gain of microstrip patch is between 0 and 5 dBi. The microstrip patch gain is a function of the antenna configuration, structure, and dimensions. Microstrip antenna arrays are used to get gain up to 30 dB. In microstrip patch arrays, a lowprofile and low-cost feed and matching network is attained by integrating the antenna feed network with the radiating patches on the same substrate. Microstrip antenna feed networks are shown in **Figure 13**. A parallel feed network is shown in **Figure 13a**. A parallel–series feed network is shown in **Figure 13b**.

#### **10. Conclusions**

This chapter presents electrical parameters of several basic antennas. Antennas are part of radio and television broadcasting, point-to-point radio communication systems, wireless LAN, cell phones, radar, medical systems, and spacecraft communication. Compact wideband efficient antennas are crucial in communication systems.

**Author details**

Kinneret and Ort Braude Colleges, Israel

*Introductory Chapter: Novel Radio Frequency Antennas DOI: http://dx.doi.org/10.5772/intechopen.93142*

provided the original work is properly cited.

\*Address all correspondence to: sabban@mx.kinneret.ac.il

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Albert Sabban

**15**

*Introductory Chapter: Novel Radio Frequency Antennas DOI: http://dx.doi.org/10.5772/intechopen.93142*
