The emission is very poorly confined along the surface of the PCB and instead has a nearly spherical distribution in the far field. Patch antennas exhibit omnidirectional emission above the patch region, or rather above the ground plane in the PCB. However, at much higher frequencies in the mmWave range, patch antennas are very useful due to their ease of design and their small size at high frequencies. At lower frequencies, such as WiFi or lower, patch antennas may not be the best choice on a PCB due to their size. ![]() Using a substrate with a larger dielectric constant will allow the patch antenna to be made smaller if required. The fundamental mode will have the largest operating wavelength, so this will determine the overall size of the patch antenna. One of the challenges with a patch antenna placed on a PCB is that they can be rather large. The design equations that will be shown below are based on this operation in the fundamental mode. This field distribution in the fundamental mode determines the radiation pattern around the patch antenna. This placement will also determine the input impedance looking into the antenna, which is discussed more below. The fundamental mode is the TM10 mode (transverse magnetic), and the feedline is placed to ensure excitation of this fundamental mode. The field line distribution for the fundamental mode between the patch and the ground plane is shown below. The image below shows the basic structure of a patch antenna with its feedline placement along the width direction. All patch antennas operate as leaky resonators, where radiation is emitted from the surface and edges of the antenna structure. For example, if the antenna is on L1, then GND should be on L2. Ideally, patch antennas in a PCB should be placed close to the ground plane, so they are best used in 4-layer boards with the ground plane on an inner layer. The width of a patch antenna is sized to support a standing wave resonance between the patch and the ground plane.Patch antennas are placed over a ground plane, and the ground plane should extend well beyond the edges of the antenna.Patch antennas are simple to design on the surface layer of a PCB and they obey two simple design rules: At the end of the article, I'll provide a link to a calculator that can be used to get much more detail on a patch antenna, including a feedline matching method. This article primarily provides the design equations for patch antennas in a PCB. To design a patch antenna, only a few simple formulas are required, and it's possible to design probe-feeding into the antenna to operate as an external module. They can also be probe-fed, which is something you might find in an external patch antenna module connected via a coaxial probe. Patch antennas are one of the simplest to design and they offer a simple polarized emission solution, especially at high frequencies.
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