The geometry of a tri-band circular disk patch antenna with (DGS) is depicted in Figure 1. The triple band presentation is achieved by cutting three parallel slots on circular disk patch and rectangular slot on ground plane with a single layer patch. The coaxial probe is directly connected to the patch and FR4 dielectric is used as a substrate, which has dielectric constant of 4.4 and height of dielectric substrate is 1.6 mm. We have selected all the dimensions of proposed antenna, as desirable for triple-band antenna.

Due to the fringing effects, electrically the shining patch of the antenna looks bigger than its physical size; the increment on L is given by:

where the effective (relative) permittivity is,

This is associated to the ratio of h/W. The larger value of h/W is, then the smaller effective permittivity is [15] [16] . The effective length of the patch is given by:

The resonant frequency for the TM₁₀₀ mode is:

An optimized width for an efficient radiator is,

Analysis of circular disk microstrip antenna is same as that of rectangular patch apart from the effective radius and its resonant frequency. Therefore, the analysis of a circular disk patch is carried out by assuming that it is equivalent to a rectangular patch [17] in which length L is supposed to be equal to 2R and width W equal to

(Figure 1). The value of effective radius is considered by equating the area of circular disk to the ex-

panded rectangular patch of dimension and where and are calculated by [18] . The design method for original case is given in next step.

If the substrate parameter (, h) and the operating frequency () are known then we can easily work out on the size of the patch antenna using above simplified equation following design method to design the antenna:

Step 1: Using Equation (6) to get out the patch width W.

Step 2: Calculate the effective permittivity using the Equation (2).

Step 3: Compute the expansion of the length using the Equation (1).

Step 4: Determine the length L by solving the equation for L giving the solution.

From Equation (6), (f_r) is the resonance frequency at which the rectangular/circular microstrip antenna is to be planned. The radiating edge W, patch width is typically kept such that it lies within the variety for efficient radiation. By using the above equations we can get the values of concrete length of the patch as:

The final optimized parameters of the antenna are given in Table 1.

Our aim is to design the multiband antenna with the help of parallel slots loaded circular disk patch with (DGS). First, we have designed rectangular ground plane with rectangular slot cut on copper plate. We used the FR4 dielectric on copper plate with thickness of 1.6 mm. After that we stacked a parallel slots loaded circular disk patch with ground plane. With the above idea, the guideline of the design can be shown in four steps, which are given below.

First Step: In first step, by using above formulas, we have design three parallel slots loaded circular disk patch stacked with, without defected ground. We found that the results like broadband antenna with frequency range (3.47 - 4.92 GHz) and central frequency 4.20 GHz. The individual bandwidth of the broadband antenna is 34.45% with maximum gain is 4.97 dBi. All results of broadband antenna can be simply shown in Figures 2-4.

Through calculation and optimization, a broadband three parallel slots loaded disk antenna is achieved as shown in Figures 2-4. The radiation pattern of the broadband antenna is good in both E and H plane, which is shown in Figure 4. The dimensions of this broadband design are listed in Table 1.

We have already done more work on broadband antennas, so we are thinking about multiband antenna and then work on the next steps which are given below.

Second step: In second step, we think about the ground defected design, so we cut a rectangular slot on ground plane and stacked circular disk over a defected ground and got the multiband performance, which is my proposed antenna. The dimensions for this proposed design are listed in Table 1 and performances are shown in Figures 5-7.

The Figures 5-7, indicate that the performance of the proposed antenna is tri-band antenna. The variation of S₁₁ parameter with frequency is shown in Figure 5. The triple band antenna can be used in C and X band; first two bands in C-band and another last one is used in X-band performance. Similar performance of the gains of the proposed antenna is shown in Figure 6. The radiation pattern of the proposed antenna is shown in Figure 7, in all origin and polar form both the E and H-plane characteristics which is good as compared to published [14] . We have also checked the performance of the antenna with dual and single slot loaded in circular disk patch which is given in next coming steps.

Third step: In third step we used only two parallel slots on circular disk and ground defected is similar as earlier step. The dimensions for this design are listed in Table 1 and performances are shown in Figures 8-10.

If we used the double slots on circular disk patch the dual band antenna performance was found, which have already done in my previous work. The S₁₁ and gain variation of the dual band antenna is shown in Figure 8 and Figure 9. The radiation pattern of the dual band antenna is shown in Figure 10, which is not good as compared to other dual band antennas. And then think about single slot performance, which is shown in the next step.

Fourth step: In fourth step we used only single slot on circular disk and ground defected is same as earlier step. The dimensions for this design are listed in Table 1 and presentation is shown in Figure 11. The performance of single slot is like a single band antenna, which is the basic of the antenna.