Patch Antenna Design Hfss

1. Microstrip Patch Antenna Design Pdf

Microstrip Antennas: The Patch Antenna Microstrip (Patch) Antennas1.2.3.4.5.6.7.In this section, we'll discuss the microstrip antenna, which is also commonly referred to as the patch antenna. Note:I'll use the terms microstrip antenna and patch antenna interchangeably.The rectangular patch antenna is analyzed, and what is learned here will be applied to understanding.(Home)Rectangular Microstrip AntennaIntroduction to Patch AntennasMicrostrip or patch antennas are becoming increasingly useful because they can be printed directly onto a circuit board. Microstrip antennasare becoming very widespread within the mobile phone market.

Patch antennas are low cost, have a low profile and are easily fabricated.Consider the microstrip antenna shown in Figure 1, fed by a microstrip transmission line. The patch antenna, microstrip transmission line andground plane are made of high conductivity metal (typically copper).

The patch is of length L,width W, and sitting on top of a substrate (some dielectric circuit board) of thickness h with. The thickness of the ground plane or of the microstrip is not critically important.Typically the height h is much smaller than the wavelength of operation, but should not be much smaller than 0.025 of a wavelength (1/40th of a wavelength)or the will be degraded.(a) Top View of Patch Antenna(b) Side View of Microstrip AntennaFigure 1. Geometry of Microstrip (Patch) Antenna.The frequency of operation of the patch antenna of Figure 1 is determined by the length L. The center frequency willbe approximately given by:The above equation says that the microstrip antenna should have a length equal to one half of a wavelength within the dielectric (substrate)medium.The width W of the microstrip antenna controls the input impedance.

Larger widths also can increase the bandwidth.For a square patch antenna fed in the manner above,the input impedancewill be on the order of 300 Ohms. By increasing the width, the impedance can be reduced. However, to decrease the input impedanceto 50 Ohms often requires a very wide patch antenna, which takes up a lot of valuable space.The width further controls the.The normalized radiation pattern isapproximately given by:In the above, k is the free-space, given.

The magnitude of the fields, given by:The fields of the microstrip antennaare plotted in Figure 2 for W= L=0.5.Figure 2. Normalized Radiation Pattern for Microstrip (Patch) Antenna.The directivity of patch antennas is approximately 5-7 dB. The fields are linearly polarized, and in the horizontaldirection when viewing the microstrip antenna as in Figure 1a (we'll see why in the next section).Next we'll consider more aspects involved in Patch (Microstrip) antennas.Fringing Fields for Microstrip AntennasConsider a square patch antenna fed at the end as before in Figure 1a.Assume the substrate is air (or styrofoam, with a permittivity equal to 1), andthat L= W=1.5 meters, so that the patch is to resonate at 100 MHz. The height h is taken to be 3 cm.Note that microstrips are usually made for higher frequencies,so that they are much smaller in practice.When matched to a 200 Ohm load, the magnitude ofis shown in Figure 3.Figure 3. Magnitude of S11 versus Frequency for Square Patch Antenna.Some noteworthy observations are apparent from Figure 3. First, the bandwidth of the patch antenna is very small. Rectangularpatch antennas are notoriously narrowband; the bandwidth of rectangular microstrip antennas are typically 3%.Secondly, the microstrip antenna was designedto operate at 100 MHz, but it isat approximately 96 MHz.

This shift is due tofringing fields around the antenna, which makes the patch seem longer. Hence, when designing a patch antenna it is typically trimmedby 2-4% to achieve resonance at the desired frequency.The fringing fields around the antenna can help explain why the microstrip antenna radiates.

Consider the side view ofa patch antenna, shown in Figure 4. Note that since the current at the end of the patch is zero (open circuit end), thecurrent is maximum at the center of the half-wave patch and (theoretically) zero at the beginning of the patch. This low current valueat the feed explains in part why the impedance is high when fed at the end (we'll address this again later).Since the patch antenna can be viewed as an open circuited transmission line, the voltage reflection coefficientwill be 1 (see thefor more information).When this occurs, the voltage and current are out of phase. Hence, at the end of the patch the voltageis at a maximum (say +V volts). At the start of the patch antenna (a half-wavelength away), the voltage must be at minimum (-V Volts).Hence, the fields underneath the patch will resemble that of Figure 4, which roughly displays the fringing of the fieldsaround the edges.Figure 4. Side view of patch antenna with E-fields shown underneath.It is the fringing fields that are responsible for the radiation.

Note that the fringing fields near the surfaceof the patch antenna are both in the +y direction. Hence, the fringing E-fields on the edge of the microstrip antennaadd up in phase and produce the radiation ofthe microstrip antenna.

Microstrip Patch Antenna Design Pdf

This paragraph is critical to understanding the patch antenna. The current adds up inphase on the patch antenna as well; however, an equal current but with opposite direction is on the ground plane, whichcancels the radiation. This also explains why the microstrip antenna radiates but the microstrip transmission linedoes not. The microstrip antenna's radiation arises from the fringing fields, which are due to the advantageous voltagedistribution; hence the radiation arises due to the voltage and not the current. The patch antenna is therefore a'voltage radiator', as opposed to the,which radiate because the currents add up in phase and are therefore 'current radiators'.As a side note, the smaller is,the more 'bowed' the fringing fieldsbecome; they extend farther away from the patch. Therefore, using a smaller permittivity for the substrate yieldsbetter radiation. In contrast, when making a microstrip transmission line (where no power is to be radiated),a high value ofis desired, so that the fields are more tightly contained (less fringing),resulting in less radiation.

This is one of the trade-offs in patch antenna design. There have been research paperswritten were distinct dielectrics (different permittivities) are used under the patch antenna and transmission line sections,to circumvent this issue.Next, we'll look at alternative methods of feeding the microstrip antenna (connecting the antenna to the receiver or transmitter).Next:Top:This page on microstrip antennas and patch antennas is copyrighted. No portion can be reproduced except by permissionfrom the author. Copyright 2011-2016, antenna-theory.com. Patch antennas, microstrip antennas.

First of all, thank you sir for your reply and willingness to help.if you have the help book for hfss 11 plz upload it, i think i have it for 10 but i am using version 11.we have proceeded by trying shapes such as square, triangle, circle etc. However, there is one problem. No clear formulae are available for calculation of dimensions of patches.My question is this:If frequency of operation, dielectric thickness (height) and epsilon value of that dielectric is given, would i be able to find the lengths and widths of patch, quarter wave transformer, feed and waveport?Can you give the related formulae?the quarter wave transformer is used for impedance matching between feed and patchthis would be most helpful to our project.

Look the other guy has guided you very well.even i did not have the HFSS 11 book and you have fine from him.You must find all the formulaes in Pozar book on microwaves or Belinis book on antennas.this is not at all a big deal. If you have lengths and material properties in hand.then to model the strucute in HFSS is not an issue any more.even when you do the practice of Patch antenna from HFSS halp books.you will learn more.I would strongly suggest you to follow the HFSS Book Example on patches.and then u can put your dimentions to it.Regarding the feed line.it is not at all an issue.You can use the waveport to excite the patch, which is also meioned in the book example.I think you must do that first.regadrs.