Patch antenna radiation pattern equation

Higher values of permittivity allow a "shrinking" of the patch antenna. Particularly in cell phones, the designers are given very little space and want the antenna to be a half-wavelength long.

One technique is to use a substrate with a very high permittivity. Equation 1 above can be solved for L to illustrate this: Hence, if the permittivity is increased by a factor of 4, the length required decreases by a factor of 2.

Using higher values for permittivity is frequently exploited in antenna miniaturization. The height of the substrate h also controls the bandwidth - increasing the height increases the bandwidth. The fact that increasing the height of a patch antenna increases its bandwidth can be understood by recalling the general rule that "an antenna occupying more space in a spherical volume will have a wider bandwidth".

This is the same principle that applies when noting that increasing the thickness of a dipole antenna increases its bandwidth. Increasing the height also increases the efficiency of the antenna.

Increasing the height does induce surface waves that travel within the substrate which is undesired radiation and may couple to other components. As the inset feed point moves from the edge toward the center of the patch the resonant input impedance decreases monotonically and reaches zero at the center.

Results and Discussions In this paper an inset fed circular microstrip patch antenna using different dielectric substrates is designed and simulated using CST.

This program analyzes the 3D and multilayer configurations general form. It is commonly used for the design of different types of antenna. It may be used to calculate and plot the return loss, standing wave ratio from Smith charts, Real power Vs Frequency, VSWR, E-field and H-field distribution, gain as well as radiation patterns.

The antenna dimensions for the dielectric materials of Arlon AD A with dielectric constant of 3. The bandwidth of the antenna is defined for that range of frequencies over which the RL is less than dB corresponds to the value of VSWR keeping less than 2 and it is calculated according to [1].

The width of the microstrip transmission line Wf is taken equal to 3. The dimensions of the proposed antenna for Arlon AD dielectric material is shown in table Table 1. The return loss, S11 of the designed antenna at resonant frequency 5. It is observed that the return loss S11 and VSWR at first started to decrease with increasing the value of notch width g that means the input impedance begins to match with the impedance of the radiating patch.

In order to obtain the better impedance matching g is varied as shown in table-2 and the lowest value of S11 At this point less amount of energy is reflected back and most of the power is transferred to the radiating patch.

The gain and directivity also increase with increasing g and finally a limit arrives where it again decreases with the variation of g. The antenna is simulated at 5 GHz but the resonant frequency and bandwidth shifted from 5. It is also observed that using equation 6 proper impedance matching can be obtained by varying g to obtain the maximum performance of a circular patch antenna when Arlon AD dielectric dielectric material is used. The maximum directivity fig.

Fig-7 and fig-8 illustrate the power accepted and the total efficiency of the proposed antenna with varying g for Arlon AD From fig. The return loss is also very high for these values of g due to proper impedance matching. The main lobe magnitude for farfield gain, farfield directivity and farfield E-field are 5. Table 2. Performance parameters of the antenna with Arlon AD dielectric material 3. VSWR of the designed antenna at resonant frequency 5.

Farfield radiation pattern of the designed antenna: a gain b directivity c H-field d E-field e Power field and f Smith chart at resonant frequency 5GHz Fig ure 7. Accepted power of the antenna with varying g Fig ure 8. Total efficiency of the proposed antenna with varying g 3.

The radius are calculated as 8. While increasing the notch gap g from 0. The resonating frequency varies from 5. Table 3. When the notch width is increased from 0. There is a little increase in directivity followed by decreased in gain due to the variation of g.

The maximum value of gain and bandwidth obtained using Fr-4 substrate are 1. The 3D radiation pattern and the polar plot of the designed antenna are shown in fig. As g is further increased above this point, the power loss started to increase while transferring it to the radiating circular patch and S11 becomes 1.

At the resonating frequency at 5. Table 4. Farfield radiation pattern of the designed antenna: a E-pattern b H-field c Power field e directivity f gain and d Smith chart at resonant frequency 5GHz 3.

It is noticed that for the thin dielectric material with higher value of dielectric constant the radius, Wf and other parameters also decreases since these parameters depend on the radius of the circular patch. Likewise, Arlond AD and FR-4 dielectric materials, using Preperm L as the dielectric material the return loss S11 and VSWR decrease simultaneously with increasing g and after attaining at their lowest level for a certain value of g, S11 and VSWR again start to increase with further increased in g.

The lowest value of the return loss and VSWR are found as But in table-6, the antenna performance parameters are taken in accordance to their individual resonant frequencies and for that reason the values of S11 and VSWR are different than from fig. The directivity also increases with the variation of g and maximum value of it is observed as 6. At resonating frequency 5.

At resonant frequency 5. This is because in these ranges of g, the input impedance does not match with the radiating patch impedance and the resonant frequency is shifted but the parameters are taken at 5. The smith chart of the designed antenna is shown in fig. The highest accepted power is found to be 0. The polar plot of the proposed antenna suggests that is may efficiently be used for the transmitting and receiving the signal and information to the remote distances with the minimum loss of energy.

Table 5. Performance parameters of the antenna with Preperm L dielectric material 5. Farfield radiation patterns of the designed antenna: a directivity b gain c E-field d H-field e power field and f accepted power of the antenna designed with Preperm L dielectric material with dielectric constant 5. The resonance frequency is shifted from 5. The return loss S11 and VSWR decreased up to a limit with increasing the value of g and after this point of g the return loss and VSWR started to increase due to mismatch of the impedance.

There is little increase in directivity with increasing g and maximum value 6. The maximum gain and bandwidth obtained using lead glass as the dielectric substrate are 5.

The characteristics of the antenna are shown in table Table 7. Performance parameters of the antenna with Lead glass dielectric material 6. Fig ure Farfield radiation pattern polar plot of the designed antenna: a directivity b gain c H-field d E-field e power field and of the antenna designed using Lead glass with dielectric constant 6.

Conclusions The effect of using different substrates on the performance of an inset feed circular microstrip antenna by varying their notch width has been studied. The resonance frequency of the antenna showed negligible shift for different dielectric materials. Likewise, rectangular patch antenna analyzed by [21], in circular patch antenna the return loss and VSWR at first started to decrease up to a level with increasing the value of notch width g and above this value of g, the S11 and VSWR started to increase again for further increased the value of g.

The dimension of the antenna also decreases for the higher values of the dielectric constants. Among the used four dielectric materials, FR-4 has the minimum gain 1. The equation 6 used for calculating the inset feed distance Fi in rectangular patch antenna by [2] can also efficiently be used in circular patch antenna to calculate the inset feed distance fi. It can be concluded that using thicker dielectric materials with their low values maximum gain and directivity are obtained.

The overall performance of the circular patch antenna is significantly influenced by the different substrate materials.