What is Antenna Aperture Tuning?

Antenna aperture tuning is a process through which the resonant frequency of an antenna can be modified/tuned to cater to a specific application/frequency. By tuning the resonant frequency of an antenna for a specific application it can operate very efficiently at that specific frequency. Also, this way the same antenna can be used to operate efficiently for multiple applications like - WiFi (Both bands), Cellular, GNSS etc.

In Aperture tuning, the electrical length of an antenna is altered to adjust the resonant frequency of the antenna. Antenna aperture tuners improve the total radiated power (TRP) and total isotropic sensitivity (TIS) by increasing the effective size of an antenna or by altering its radiation pattern.

A switch is used to adjust the resonant frequency of the antenna to the desired frequency band of operation. It is connected between the antenna and the ground. A capacitor or inductor can also be used to further adjust the resonant frequency, to support different bands. They can be connected between the switch and the radiating element.

The figure below shows the concept of aperture tuning with four different cases:

• The resonant frequency of an antenna when the switch is off
• The resonant frequency of an antenna when the switch is on
• The resonant frequency of an antenna when an inductor is connected between the switch and the radiating element
• The resonant frequency of an antenna when a capacitor is connected between the switch and the radiating element

As can be seen in the figure above, each configuration alters the frequency of the antenna. The x-axis in the figure is the frequency.

Antenna Aperture Tuning is a method used to compensate for reduced antenna performance in smartphones, caused because of reducing antenna sizes and increased screen size. It allows smartphones to support the broad range of RF frequency bands and transition to 5G.

Today's typical LTE smartphones need 4-6 antennas to support carrier aggregation (CA), MIMO, Wi-Fi, GPS, and Bluetooth. But with the transition to 5G, smartphones need to operate over a wide range of RF bands from Sub-6 GHz to mm Waves. Next-Gen 5G smartphones need typically 6-10 antennas, to deliver higher data rates and support techniques like CA and MIMO. Future 5G handset requires at least four antennas for cellular communications only. 

Exacerbating the situation is the design of smartphones. The increased screen size demand has reached the verge of bezel less phones, i.e. no space for antennas. These bezel less phones makes it increasingly difficult to fit all these antennas into the limited space available.

Need for more antennas and less space results in shrinking of antenna sizes, which reduces antenna efficiency and bandwidth. This reduced efficiency can impact transmit (Tx) and receive (Rx) performance, causing shorter battery life, lower data rates and connectivity problems. So to improve a smartphone's performance, aperture tuning is used for compensate for all these factors.