2. Regulation and application

The UWB wireless communication has been only authorized to the military communication for 42 years. Since 2002, the FCC released the unlicensed

employment of UWB for commercial purpose and classified the application scenario into imaging system, vehicle radar system, and communication and measurement system. According to the regulation of FCC, the f<sup>L</sup> and f<sup>H</sup> are located at 3.1 and 10.6 GHz, where f<sup>L</sup> and fH, respectively, stand for the frequencies with 10 dB attenuation of the upper and lower sidebands. Therefore, the center frequency of UWB bandpass filter is expressed as

$$f\_C = \frac{f\_H + f\_L}{2} = 6.85 \text{ GHz} \tag{2}$$

Meanwhile, the FBW can also derived as

$$FBW = \frac{2\left(f\_H - f\_L\right)}{f\_H + f\_L} = 109.5\% \tag{3}$$

end of the receiving system [5]. Therefore the UWB bandpass filters are known as an inevitable key building block of wideband communication systems, and the filtering performance of UWB bandpass filter will directly related to the perfor-

The comparison between the UWB spectrum and spectrum of currently commercial communication systems.

The performance is a critical factor for UWB filters even in any engineering device,

1. Insertion loss (IL): insertion loss is the attenuation caused by the introduction of the device between the in port and out port, usually expressed in dB. The

Pout

ð Þ dB (4)

and the major parameters for UWB filter performance evaluating are as follows:

IL <sup>¼</sup> 10 log Pin

where Pin is the input transmitted power and the Pout is the output received power. In addition to the mismatching loss, the actual bandpass filters have a series

3. Microwave foundation of designing UWB bandpass filters

The sketch of transmitting system and receiving system with primary components.

mance of the entire UWB system.

Figure 2.

Review on UWB Bandpass Filters

DOI: http://dx.doi.org/10.5772/intechopen.87204

Figure 3.

81

3.1 Performance specifications

insertion loss can be calculated as follows:

of other losses. Firstly, dielectric loss, can expressed as

For the purpose of evading the interference of UWB systems and existing communication systems (such as GPRS, WLAN, TD-LTE, and mobile cellular), the radiation spectral density of UWB systems is strictly limited and regulated, the highest power spectral density of the UWB systems regulated not exceeding �41.3 dBm/MHz, as illustrated in Figure 1. It is worth noting that the regulation also varies depending on the indoor and outdoor circumstance.

As depicted in Figure 2, the UWB band has an extremely high FBW and unparalleled 7.5 GHz absolute bandwidth; the UWB therefore has potential in many applications. The UWB can be applied to support large channel capacity since its huge bandwidth, whereas its propagation distance is limited by low effective isotropic radiated power (EIRP). Therefore, the UWB is an ideal candidate for short-distance high-rate communication. For detecting, the UWB has a dramatic penetrating ability by using its outstanding weak narrow pulse of baseband, which can easily penetrate the leaves, the earth's surface, the clouds, and the concrete; even objects behind the obstacle can also detected. For locating, high positioning accuracy can be accomplished by UWB technology, whether for military or civilian application.

The UWB bandpass filters have the responsibility to remove the unwanted signals and noise in UWB communication system. As shown in Figure 3, for the transmitting system, the modulated signal is directly filtered by using the UWB bandpass filter, and the UWB bandpass filter is also a critical component in RF front

Figure 1. Indoor radiation masks and outdoor radiation mask regulated for UWB system by FCC.

Review on UWB Bandpass Filters DOI: http://dx.doi.org/10.5772/intechopen.87204

#### Figure 2.

employment of UWB for commercial purpose and classified the application scenario into imaging system, vehicle radar system, and communication and measurement system. According to the regulation of FCC, the f<sup>L</sup> and f<sup>H</sup> are located at 3.1 and 10.6 GHz, where f<sup>L</sup> and fH, respectively, stand for the frequencies with 10 dB attenuation of the upper and lower sidebands. Therefore, the center frequency of

<sup>2</sup> <sup>¼</sup> <sup>6</sup>:85 GHz (2)

¼ 109:5% (3)

<sup>f</sup> <sup>C</sup> <sup>¼</sup> <sup>f</sup> <sup>H</sup> <sup>þ</sup> <sup>f</sup> <sup>L</sup>

FBW <sup>¼</sup> <sup>2</sup> <sup>f</sup> <sup>H</sup> � <sup>f</sup> <sup>L</sup>

also varies depending on the indoor and outdoor circumstance.

plished by UWB technology, whether for military or civilian application.

Indoor radiation masks and outdoor radiation mask regulated for UWB system by FCC.

The UWB bandpass filters have the responsibility to remove the unwanted signals and noise in UWB communication system. As shown in Figure 3, for the transmitting system, the modulated signal is directly filtered by using the UWB bandpass filter, and the UWB bandpass filter is also a critical component in RF front

 f <sup>H</sup> þ f <sup>L</sup>

For the purpose of evading the interference of UWB systems and existing communication systems (such as GPRS, WLAN, TD-LTE, and mobile cellular), the radiation spectral density of UWB systems is strictly limited and regulated, the highest power spectral density of the UWB systems regulated not exceeding �41.3 dBm/MHz, as illustrated in Figure 1. It is worth noting that the regulation

As depicted in Figure 2, the UWB band has an extremely high FBW and unparalleled 7.5 GHz absolute bandwidth; the UWB therefore has potential in many applications. The UWB can be applied to support large channel capacity since its huge bandwidth, whereas its propagation distance is limited by low effective isotropic radiated power (EIRP). Therefore, the UWB is an ideal candidate for short-distance high-rate communication. For detecting, the UWB has a dramatic penetrating ability by using its outstanding weak narrow pulse of baseband, which can easily penetrate the leaves, the earth's surface, the clouds, and the concrete; even objects behind the obstacle can also detected. For locating, high positioning accuracy can be accom-

UWB bandpass filter is expressed as

UWB Technology - Circuits and Systems

Figure 1.

80

Meanwhile, the FBW can also derived as

The comparison between the UWB spectrum and spectrum of currently commercial communication systems.

#### Figure 3.

The sketch of transmitting system and receiving system with primary components.

end of the receiving system [5]. Therefore the UWB bandpass filters are known as an inevitable key building block of wideband communication systems, and the filtering performance of UWB bandpass filter will directly related to the performance of the entire UWB system.
