The Pros and Cons of Patch Antennas
What Is a Patch Antenna?
Patch antennas are flat antennas with a single or multiple “patches” to receive the signal. Patch antennas are also called microstrip antennas, flat panel antennas and panel antennas.
The patch antenna is made from two different plates. The patch antenna is made from two different plates. The smaller radiating patch with a dielectric substrate sites on a larger ground plane. The feed point for the antenna runs from the patch on the patch antenna down to the back of the entire antenna.
You can find patch antennas with linear polarization or circular polarization. Linear polarized patch antennas tend to have slightly more gain and work over a wider range of frequencies than Circular polarized patch arrays. But circular polarized patch arrays often work better in high multipath environments, such as working between large buildings in urban area.
The Benefits of Patch Antennas
Patch antennas are lighter weight and take up less space than a comparable helical antenna. Many patch antennas are cheap and durable because they are made on printed circuit boards.
Patch antennas are by their very design high “Q” antennas, enjoying a high degree of radiation efficiency. A drone with a patch antenna relaying video back to the controller will be able to send back high quality video farther and longer than if you were only using a wheel or helical antenna. You could get 50% greater range for your FPV drone.
Because these antennas are flat and can often be covered in plastic, they are often inconspicuous.
Patch antennas have high gain on narrow frequencies; it isn’t going to let you receive a variety of frequencies. If you increase the number of patches, you increase the gain. Given their flat design, adding these extra “patches” means the antenna is just a little bigger in one direction or the other.
The Weaknesses of Patch Antennas
Patch antennas usually only let you receive signals from a narrow beam width. This is why many drone pilots who use a patch antenna to extend the range of their drone in one direction have at least one omni-directional antenna on the drone. In the case of GPS applications, the best place to put the antenna is on the top of a structure or device with the patch pointing directly at the sky. For control, video, and data links, the patch antenna needs to be looking back at the operator.
Gain is highest when the antenna is directly facing the transmitter. For example, a GPS patch antenna has highest gain when placed flat on a surface facing the zenith. This works well for looking at the GPS satellite constellation.
Observations about Patch Antennas
Patch antennas have similar gain to Yagi antennas. Patch antenna gain is correlated to the ground plane size and the number of patches. The design of the power dividers connected all the patches tend to be in 2n number of patches. That would be 2,4,8,16,32, etc.
The height of the patch element determines its resonant frequency. The width of the patch controls bandwidth (how wide a frequency span the antenna works over) and the impedance of the patch element.
If you’re using a directional patch antenna, you’ll get limited range on the sides and back of the antenna. Connecting multiple directional patch antennas to generate 360° coverage may be more expensive than using a wheel antenna. This is why wheel antennas are preferred for FPV applications than patch antennas though you can connect multiple (typically 4) patch antennas to a drone.
The Uses of Patch Antennas
Patch antennas are regularly used in ATVs, beacons, MIMO, wi-fi applications, AMSAT, GPS, repeaters, wireless systems and dish feeds.
© 2017 Tamara Wilhite