# Rectangular Microstrip Antenna with Spaced Dielectric Superstrates Frequency Study

Article by Arvind Krishnan updated June 24, 2016

###### Article

Microstrip antennas are becoming a popular choice for a wide range of wireless communication.  They are lightweight, low cost, and straightforward to design, this application, however, requires that the antenna be placed out of sight of the consumer, beneath protective dielectric superstrates.

This placement of the microstrip antenna shifts the antenna resonant frequency. Generally, a microstrip antenna that is designed, without consideration of these frequency shifts, will not perform as expected once installed in a wireless equipment.

The design under study consists of a microstrip antenna covered with multi dielectrics with low relative permittivity of substrates (Ɛr<3).

HFWorks resonance study is used to calculate the resonant frequency of the microstrip antenna, shown in the figure below, covered with a multilayer of dielectrics, to compute the behavior of the electric field and to compute the quality factor Q.

Figure 1: HFWorks Model View

In this example we will choose only 1 mode. However, in HFWorks resonance study, the user can enter as many modes as required. It defines the number of the frequencies at which the structure resonates. For the patch and the ground plane we will apply a PEC. In the table below is a list of the material assigned for each layer:

Number of LayerRelative permittivityDielectric Loss Tangent
Layer 1Ɛr=2.32Tan δ=0.0002
Layer 2Ɛr=2.32Tan δ=0.0002
Layer 3Ɛr=1Tan δ=0

Results of the resonant frequency, quality factor Q (Q-Dielectric, Q-Conductor Q-effective), and stored energy are illustrated in the table below.

Figure 2: HFWorks Results Table

The measured [1] and the simulated values of the antenna resonant frequency are presented in the figure below, and demonstrate the high accuracy of HFWorks Resonance Study.

Figure 3: Comparison between simulated and measured value of frequency

In the HFWorks resonance study we can represent the distribution of the electric field for each mode. This plot represents the flux lines of the electric field that exists in the substrate of the structure, the superstrates, or in the air gap. Figure 4 depicts the distribution of the electric field at f=3.75GHz, at which the structure resonates.

Figure 4: Electric Field at 3.75GHz (HFWorks also includes an animation)

HFWorks software package can be used to effectively calculate electromagnetic field distributions, resonance parameters and losses density. In this article, design of Rectangular Micro strip Antennas with Flush and Spaced Dielectric Superstrates have been described. Good agreement between HFWorks simulation and measurement has been achieved. Hence, in addition of being fully integrated in SOLIDWORKS, HFWorks is also accurate and easy to use.

HFWorks offers a complete suite of solvers to cover all your high frequency analysis needs. Whether you are interested in resonance/eignmode analysis, S-parameters, Antennas or Scattering you need HFWorks. Contact us about HFWorks to learn more about the high frequency design analysis solution for SOLIDWORKS engineers.

##### References:
`[1] Resonant Frequencies of Rectangular Microstrip Antennas with Flush and Spaced Dielectric Superstrates, Jennifer T. Bernhard, Member, IEEE, and Carolyn J. Tousignant, Student Member, IEEE,VOL.47, pp.302-308,NO. 2, FEBRUARY 1999.`