How to Use a 2.4 GHz Quad Patch Antenna
What Is a 2.4 GHz Quad Patch Antenna?
Dipole antennas are half the length of the wavelength. Quarter wave monopoles are one fourth of the wavelength of the frequencies they are supposed to receive. Quad patch antennas are laid out on a printed circuit board.
The quad patch antenna is embedded or laid out on the printed circuit board (PCB) instead of resembling the coated antenna wire or loop of many monopole and dipole antennas.
A 2.4 GHz quad patch antenna is thus an antenna designed to pick up signals or transmit them in the 2400 to 2450 MHz or 2.4 GHz frequency range with the antenna itself part of a printed circuit board.
Uses of the 2.4 GHz Quad Patch Antenna
The 2.4 GHz frequency range is part of the UHF or ultra high frequency range. UHF wavelengths are between 10 and 100 centimeters. 2400 MHz quad patch antennas are used for a variety of UHF applications.
The 2400-2450 MHz quad patch antennas are recommended for 2.4 GHz wi-fi, 2.4 GHz video, 2.4 GHz UHF communications, 2400 MHz wireless systems and 2.4 GHz RFID.
Let’s look each of these uses in detail.
2.4 GHz Wi-Fi Antennas
This frequency range, part of the ISM band, was the first approved for unlicensed spread spectrum communications in the U.S., and it was adopted rapidly by several emerging technologies such as wi-fi.
2.4 GHz antennas fall under the IEEE 802.11 wireless standard. These antennas are subject to interference from Bluetooth devices, cordless telephones, some iridescent lights, wi-fi antennas on the same frequency and microwave ovens. Conversely, 2.4 GHz antennas are also used for Bluetooth, cordless phone, Zigbee and wi-fi signals.
This interference can be reduced by using direct sequence spread spectrum or DSSS or orthogonal frequency division multiplexing or OFDM. In some areas, users have switched to antennas in the 5 GHz band; the 5 GHz frequency range has more non-overlapping channels than the 2400-2450 MHz range and doesn’t interfere with the more commonly used 2.4 GHz range.
Another solution is installing a 5 GHz antenna to handle part of the wi-fi traffic in an area in addition to existing 2.4 GHz systems, reducing the bandwidth demands in the 2.4 GHz range.
Project Loon by Google, which uses high altitude balloons with 2.4 GHz antennas to fill in the internet’s reach, operates in this frequency range.
2.4 GHz Video Antennas
2400 MHz / 2.4 GHz antennas are regularly used for video signals. They are used in wireless CCTV security systems, wireless video baby monitors, wireless security cameras and even DVD players. Their video signals tend to be clearer than applications at other frequency ranges because of their high bandwidth transmissions. In these applications, you may be able to get a range as high as 4,000 meters, but signal quality and reliability go down with distance.
The 2.4GHz frequency range receives very little ham radio traffic, though it is open to amateur radio conversations. This frequency range is called the 13 cm ham band, since the wavelength of a 2.4 GHz signal is 13 centimeters. However, using a ham radio in this frequency range does require an amateur radio license from the FCC.
2400 MHz Wireless Systems
2400 MHz antennas, when part of wireless systems, are used for WAN (wide access network) communications.
The 2.4 GHz antenna is often used for remote control applications like RC cars, remote controlled airplanes and even personal drones. The two frequency bands allocated by the FCC for drones are 2.4 GHz to 2.5 GHz and 433.05 to 434.79 MHz.
2400-2450 MHz RFID Antennas
Radio frequency identification or RFID systems regularly operate in the 2400 MHz frequency range. RFID transmitters are allowed to operate in several frequency ranges, such as 918 to 926 MHz, 2400-2450 MHz, 5725-5795 MHz and several others.
Source: "RFID Applied, Edition 1" by Jerry Banks, Manuel Pachano, Les Thompson, and David Hanny.
Technical Specs for 2.4 GHz Quad Patch Antennas
dB is a measure of the gain or loss in a communication system. It measures the power of the signal output versus the power put into the antenna or system. The average gain for this antenna is 11 to 12 dBi. The maximum allowed by the FCC for 2.4 GHz antennas is 24 dBi gain if the power is 16 mW. For spread spectrum applications in the 2400 MHz range, the FCC limits systems to 1 Watt of output power.
Note: The height of the patches in the example are approximately 1/2 wavelength in length when the dielectric constant of the substrate insulator is considered.
The antenna is a DC short. This protects the 2.4 GHz products from static discharge.
Communications in the 2.4 GHz range requires an amateur radio license from the FCC in the United States. Installing RFID systems or wi-fi networks in this frequency range may require a license or other permissions in your jurisdiction.
1. "RFID Applied, Edition 1" by Jerry Banks, Manuel Pachano, Les Thompson, and David Hanny
2. “Understanding the FCC Regulations for Low-Power, Non-Licensed Transmitters” by the FCC, published October, 1993
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