**5. Polarization detection**

#### **5.1 Detection of polarization modulated signal**

The simplest way to detect the polarization at receivers is to use two orthogonally polarized antennas and compare the signals received by the two antennas.

**Figure 7** shows a basic configuration to detect the polarization. Two antennas for horizontal and vertical polarization are connected to a comparator. Comparison of the signals received by the two antennas discriminates the polarizations.

The polarization discrimination can be easily achieved in RF by using an RF multiplier as a comparator. When a polarization modulated radio wave has polarizations of ±45° , the vertical and horizontal components of the radio wave are separately received by using the two orthogonally polarized antennas, and the voltage of each component is expressed as follows:

$$V\_{\rm H} = V \sin \left( \alpha t \right) \tag{4}$$

$$V\_V = V \sin\left(\alpha t + \varphi\right) \tag{5}$$

where φ is the phase difference between the horizontal and vertical components and it is 0 or *π* in the case of ±45° polarization modulation.

The DC output voltage of the multiplier is

$$V\_{\rm out} \propto V^2 \cos \mathfrak{q}.\tag{6}$$

**65**

*Polarization Modulation*

adding 90°

**Figure 8.**

systems.

**Acknowledgements**

and JP17K06429.

**6. Conclusions**

*Polarization discrimination antenna [11].*

*DOI: http://dx.doi.org/10.5772/intechopen.87985*

Polarization discrimination for circular polarizations is similarly achieved by

In this chapter, a modulation scheme which effectively utilizes the polarization of the radio wave is introduced. The polarization modulation gives a new degree of freedom in the modulation adding to the phase, amplitude, and frequency. Antenna technology is a key to achieve the polarization modulation communication systems. Basics of the polarization modulation and several examples of the polarization agile antennas are introduced. Furthermore, the detection of polarizations and a polarization discrimination antenna are also explained. The concept utilizing polarizations gives new vistas to the next-generation advanced wireless communication

The author wishes to appreciate Dr. Eisuke Nishiyama and Dr. Takayuki Tanaka,

This work was supported in part by JSPS KAKENHI Grant Numbers 26420361

Associate Professors, Saga University, Japan, for their fruitful discussions. The author also would like to thank Tasuku Uechi of Saga University, Japan, for his technical support and all the students of the Communication Engineering Lab, Saga

University, Japan, for their continuous hard work.

phase difference between the horizontal and vertical components [12].

Therefore, when the phase difference φ = 0, the output voltage of the multiplier *V*out becomes positive, and it becomes negative when φ = *π*. Therefore, the polarization modulated signal can be demodulated in RF.

#### **5.2 Polarization discrimination antenna**

**Figure 8** shows a practical implementation of the polarization discrimination antenna. The antenna consists of 12 microstrip antenna elements, feed network and double-balanced multiplier [11]. The feed network employs microstrip lines and slot lines and achieved simple planar structure. The double-balanced multiplier is located at the center of the array antenna and composed of a slot ring and four detector diodes mounted on the slot ring.

The horizontal and vertical components of the radio wave are separately received by the antenna. The blue and red arrows show the signal of the horizontal and vertical polarizations, respectively. Each received signal is applied to the RF multiplier, and the detected voltage is obtained at the inner conductor of the slot ring.

**Figure 7.** *Basic configuration to detect the polarization.*

*Modulation in Electronics and Telecommunications*

each component is expressed as follows:

and it is 0 or *π* in the case of ±45°

The DC output voltage of the multiplier is

modulated signal can be demodulated in RF.

**5.2 Polarization discrimination antenna**

detector diodes mounted on the slot ring.

*Basic configuration to detect the polarization.*

**5.1 Detection of polarization modulated signal**

The simplest way to detect the polarization at receivers is to use two orthogonally polarized antennas and compare the signals received by the two antennas. **Figure 7** shows a basic configuration to detect the polarization. Two antennas for horizontal and vertical polarization are connected to a comparator. Comparison

The polarization discrimination can be easily achieved in RF by using an RF multiplier as a comparator. When a polarization modulated radio wave has polariza-

rately received by using the two orthogonally polarized antennas, and the voltage of

*V*<sup>H</sup> = *V* sin(*t*) (4)

*V*<sup>V</sup> = *V* sin(*t* + φ) (5)

*V*out ∝ *V*<sup>2</sup> cosφ. (6)

Therefore, when the phase difference φ = 0, the output voltage of the multiplier *V*out becomes positive, and it becomes negative when φ = *π*. Therefore, the polarization

**Figure 8** shows a practical implementation of the polarization discrimination antenna. The antenna consists of 12 microstrip antenna elements, feed network and double-balanced multiplier [11]. The feed network employs microstrip lines and slot lines and achieved simple planar structure. The double-balanced multiplier is located at the center of the array antenna and composed of a slot ring and four

The horizontal and vertical components of the radio wave are separately received by the antenna. The blue and red arrows show the signal of the horizontal and vertical polarizations, respectively. Each received signal is applied to the RF multiplier, and

the detected voltage is obtained at the inner conductor of the slot ring.

where φ is the phase difference between the horizontal and vertical components

polarization modulation.

, the vertical and horizontal components of the radio wave are sepa-

of the signals received by the two antennas discriminates the polarizations.

**5. Polarization detection**

tions of ±45°

**64**

**Figure 7.**

**Figure 8.** *Polarization discrimination antenna [11].*

Polarization discrimination for circular polarizations is similarly achieved by adding 90° phase difference between the horizontal and vertical components [12].
