**1. Introduction**

Since the FCC allows the use of the UWB spectrum, the development of new systems that will adapt to this band has been growing. Much attention has been given to developing new systems that fit with UWB applications as radar detection, biomedical imaging. The proposed UWB antenna is more likely to be used in the biomedical imaging applications as a system to detect breast cancer.

Breast cancer is the second deadly cancer for women, for more efficiency and an early detection, the biomedical field need new systems that should be safe, comfortable and sensible [1, 2]. The medical field already has its methods to detect breast cancer like X-ray mammography, magnetic resonance imaging (MRI), as efficient as those techniques are they are missing between 10 and 30% [2] of very early breast cancer stages.

The UWB microwave imaging is one of the techniques that has been developed, in the Hunt for the next techniques that will detect breast cancer in its early stages. The basis for microwave detection is to compare between the dielectric properties of a normal tissue and cancerous tissue, the result of the comparison gives a prediction of malignant tissue characteristics as it size, shape, placement, … [3].

The second part of this chapter, I present a microstrip antenna that we offer is circular in shape and, a priori, has a low gain and a narrow bandwidth. To meet the requirements of our specifications would be to expand the bandwidth. For this reason, we have developed a design methodology, which has enabled us to develop an antenna capable of meeting these requirements.

The reduction in size is also a consideration to take into account when designing this antenna, which would allow it to be more easily integrated into the system and reduce the size. For this, the certain techniques are used. Among these techniques, we will use the slot insertion at the level of the radiating element.

The design procedure followed consists of three steps:


#### **2. Design of a UWB coplanar fed antenna**

#### **2.1 Ultra wide band**

UWB is defined as a system with a very large band, this large spectrum comes usually with some advantages as a low power, high debit of data, high time resolution, low-cost and an ease of implementation, resistance to interference and so on. Those advantages opened a wide range of UWB application to radar detection, biomedical imaging, and HD communication.

The definition of UWB is not a special one, the FCC (Federal Communication Commission) [4] defines it as a system with a bandwidth larger than 500 MHz or larger than 20% if we are working whit the relative bandwidth W/fc (W is the width of the band and fc is the carrier frequency). The UWB is being defined by its very large band that is 7.5 GHz between 3.1 GHz and 10.6 GHz for a limitation of the power emission level −41.3 dBm/MHz [4].

#### *2.1.1 Matching and efficiency*

The UWB communication systems uses a very short pulse duration of tens hundreds of nanoseconds, and sense the pulse and the bandwidth are inversely proportional, the shorter pulses is the wider the spectrum is going to be.

Antennas would match the UWB requirements if it have a bandwidth greater than 500 MHz defined at −10 dB according to the FCC, or to have a relative bandwidth more than 20% [4, 5].

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**Figure 1.**

*Geometry of the antenna proposed.*

*Design of a UWB Coplanar Fed Antenna and Circular Miniature Printed Antenna for Medical…*

The efficiency of an UWB antenna can be evaluated by the specter efficiency,

The signal passing through the UWB antennas is a very short pulse, the shorter the pulse is more likely the UWB antenna's response is going to be distorted and delayed

The rippling effect is caused by the geometry of the antenna, and it causes frequency translation, dispersion or delay on the transition reducing the speed of

This section is dedicated to the design and the performance of the proposed antenna. The design proposed is a notched coplanar antenna. The geometry of

thickness h = 3.175 mm. The top part of the antenna is a circle with two cutouts of

The two main characteristics that effect the performance of the antenna was the inner radius of the circle R and the laminate thickness. The gap between the transmission line and the ground structure was optimized so that the antenna's imped-

**Figure 2** shows the return loss or more known as the parameter S11 of the antenna, the spectrum of **Figure 2** contains the UWB frequency band spectrum. The spectrum's antenna range is form 2.8 GHz to 10.9 GHz and contains tow resonate frequencies

, Rogers RT5850 substrate with *ε*r = 2.2 and

Where *f*l and *f*h are the low and the high frequency respectively.

the evaluation matching has to be over the whole range of frequencies.

due to the ripple after the pulse called the rippel effect [5].

90° each. The structure of the antenna is shown in **Figure 1**.

*DOI: http://dx.doi.org/10.5772/intechopen.93205*

*2.1.2 Signal dispertion ans distortion*

the antenna consisted of a 25 × 30 mm2

ance can match a 50 Ω SMA port.

**2.3 Performances of the antenna**

*2.3.1 The return loss S11*

data transmission [6].

**2.2 Antenna design**

Where *f*l and *f*h are the low and the high frequency respectively.

The efficiency of an UWB antenna can be evaluated by the specter efficiency, the evaluation matching has to be over the whole range of frequencies.
