Question: What is wireless antenna polarity and why is it important?

Answer: Polarization refers to the different shapes and orientations of electromagnetic waves as they move through space. Wireless audio systems emit these signals over a particular frequency, which is picked up by an antenna connected to a receiver. The polarity characteristics of the antenna play a critical role in optimizing the signal and transferring it from one device to another through the air. While there are different antenna techniques that perform well for a particular application, when it comes to wireless microphones, linear polarized antennas are often used.

Linear polarized antennas operate with horizontal and vertical planes. Stationary antennas are ideal as they allow transmit and receive antennas to be chosen and set up for an optimized transfer of energy. However, in the real world of wireless microphones, either or both of the antennas are often in motion. This is where setting up antennas to avoid signal dropouts is important. When someone holds a wireless handheld microphone transmitter in the upright vertical position, the signal transmission from the device’s antenna is vertically polarized. The most efficient pickup would come from an antenna that is also vertically polarized. However, if the transmitter is tilted to a horizontal position, like most people do while singing directly into the microphone, the signal transmission becomes horizontally polarized. The transmit and receive antennas are now 90 degrees off axis and you will have a significant loss of the signal.

So, the question is, “Do you orient your antenna for a horizontal or vertical polarity?” This may be determined by the type of antenna you are using. Wireless systems that use a traditional two-whip antenna setup may have one antenna oriented in a horizontal position and the other in a vertical position, or may place each at a 45-degree angle, creating a “V.” The diversity receiver will determine which of the two antenna signals is the most desirable to use at any given moment. The signal pickup may consistently use one antenna or switch between the two while in use.

To make the situations even more challenging, the wireless signals, just like sound, may bounce off of surfaces, causing multipaths to a receiving antenna. Therefore, proper design and setup of the wireless system is important for successful operation. Traditionally, wireless systems have used “special diversity” with two antennas being separated from each other. If one antenna could not capture the signal adequately, the other would hopefully be in a more desirable location to pick up the intended signal.

Other antennas optimized for polarization are the RF Venue DFIN and D-OMNI. The DFIN uses a directional LPDA-style antenna for the vertical plane and a pair of dipole whip antennas, mounted on each side of the LPDA, for the horizontal. With the design of the LPDA, the antenna pickup is directional and may be aimed toward the desired transmit signal pickup area. The D-OMNI antenna uses a similar concept, with one antenna picking up the vertical plane and the other picking up the horizontal plane, but it is able to provide 360-degree omnidirectional coverage around the antenna.

Since users of wireless microphone systems are so often moving around, be certain to have your wireless antenna optimized for pickup. RF Venue has fantastic literature and application notes on wireless antenna polarization and polarization diversity antenna systems to help you. If you have further questions on which antenna may work best for your wireless setup, contact the Audio Solutions Department for additional assistance.