Effective Microstrip Feed Line Length in Ultra-Wideband Responses and Wireless Applications

In this article, an effective feed line technique is used instead of DGS (Defected Ground Structure) and CSRR (Complimentary Split Ring Resonator) which are commonly used for achieving UWB (Ultra-Wideband Applications) responses. A classical antenna is designed for 2.4GHz frequency with a feedline of 180° electrical length. The resonance of proposed antenna responses as UWB and it has interesting current distributions through the patch antenna. This paper avoided all aspects of existing techniques which are proposed to achieve UWB.


1.
Introduction Microstrip patch antennas are widely used for wireless communication in MM wave applications [1]. The design theory of antenna is studied by various researchers and different types of geometry models are invented with respect to their knowledge and applications [2] [3] [4]. Among them, widely used is the rectangular patch antenna, which is having impressive characteristics like narrow bandwidth, basic positive radiation pattern in terms of dB, horizontal polarization with respect to design axis, etc. It is being appreciated for its design aspects that include easy sketch, feeding techniques, fabrication, etc [5].
There are different types of feeding techniques used for exciting the rectangular patch antenna [6] [7] [8]. One of the most used feeding methods is microstrip feed line, whereas the other feeding techniques like coaxial feed and aperture coupled feed have design challenge aspects [5]. The feed line is a conducting strip to the patch antenna with smaller width (f W ) when compared to patch (p w ), i.e. f W <<p w . This feeding technique is easy to position to the proposed model of patch. So, this paper proposes effective feed line length (FL) which gives Ultra-Wide Band (UWB) responses, and the parameters of antenna are compared with previous works which are useful to study about UWB technology design aspects.

2.
Design of effective electrical length antenna The rectangular patch antenna is designed for fo=2.4GHz, with the following design equations. The geometry design of the patch depends on dielectric constant. The patch and feedline are placed on the dielectric material consisting electrical characteristics. Electrically, the microstrip patch antenna looks greater than its physical dimension due to fringing effect. Figure 1 shows the top view dimension of microstrip patch antenna with geometrical calculations for ɛr=4.4 and substrate thickness 0.5mm.
The width of the patch for same resonant mode, By using Eq. (2.4) and Eq. (2.5), the patch dimensions are calculated. So, the length and width of the patch are L= 27.9mm and W=38mm.
The return loss of 2.4GHz patch antenna is as shown in Figure 1.     Figure 6 shows the return loss of effective length introduced in the patch antenna and inset feed technique is removed without disturbing the dimensions of the patch with respect to 2.4GHz. The proposed design explored in Figure 5 achieved UWB frequency responses. The bandwidth of an antenna depends on SWR (Standing Wave Ratio) where 2:1 is the lossless transmission line.

Results and Discussion for Effective Feedline Technique.
So, the antenna is fed with lossless transmission line of 180 o electrical length feed line. Basically, microstrip patches respond with narrow bandwidth. In this proposed design, the antenna dimension is not optimized and is designed at a frequency of 2.4GHz. The feeding techniques are studied very deeply with mode analysis. TM 010 mode analysis is used achieve this response. This article proposes the novel work of electrical length. It also decides the reflection loss of antenna to get UWB.

Achieving UWB with DGS
Employing defects on the ground plane to enhance antenna parameters like Input Impedance, Radiation Pattern, Gain, Efficiency, return loss is proved to be a complex yet useful technique to obtain the desired characteristics. This method of sliding defects such as slots, stubs on the ground plane along with periodic and aperiodic structures is called DGS ( For this evaluation, we designed a concentric circular patch antenna at 2.4GHz (Figure 7) This is further extended to UWB frequency range by using partial ground plane method followed by dimensional optimization of the design parameters. Defects are later introduced on the ground plane in form of small slots across the edge and directly under the feedline. The working of the antenna is analysed by varying the radius of the concentric circular patch, along with length and width of the slots on the ground plane. This design achieved return loss less than -10dB at application frequencies as proposed in the paper and exhibits good gain and radiation properties.

Result
While comparing the gain, return loss and radiation pattern parameters of both feedline simulated and DGS simulated designs, we can observe that the effective feedline technique resonates at desired application frequencies with dual and multiband operations thus building high gain and return loss values. Whereas DGS outputs do obtain the desired characteristics, but for optimum results, design modifications are to be done which results in complexity. Here, the term design modifications highlight the fact of introducing more defects on the ground plane.

6.Conclusion
The direct feeding method gives more affable response when compared to inset feed technique due to the changes in electrical length of antenna. The proposed antenna responded at the given application frequency ranges.