Aperture Tuning vs. Impedance Tuning in 5G and IoT Antennas

This page compares aperture tuning and impedance tuning, two techniques used in antenna tuning, and describes the difference between them in the context of 5G mobile and IoT device designs.

What is Antenna Tuning in 5G?

Introduction: Antenna tuning is crucial for effectively utilizing bandwidth for carrier aggregation and minimizing power consumption. The 5G system relies on MIMO (Multiple-Input Multiple-Output) and Carrier Aggregation (CA) to achieve higher throughput and bandwidth efficiency. MIMO systems necessitate multi-antenna arrays, which, in turn, require antenna tuning techniques. Antenna tuning is also essential for adjusting resonance frequencies.

Antenna tuners are configured to optimize the matching between the antenna and the RF Front End (RFFE) circuits. This maintains RF performance under varying conditions, including frequency band, power level, impedance, and temperature.

There are two primary methods for tuning an antenna or MIMO array antenna:

• Impedance tuning
• Aperture tuning

Both methods utilize antenna switches, which are commercially available as surface-mount ICs.

Antenna Aperture Tuning

• Aperture tuning is typically achieved using a switch with low loss to prevent degradation of antenna radiating efficiency.
• The switches can be shunt or series type. Shunt-type switches are often preferred due to their lower ohmic loss compared to series-type switches, resulting in higher radiation efficiency.
• It allows the 5G system with an antenna to switch between frequencies in two ways. Individual resonances can be tuned capacitively or inductively. The aperture switch and antenna together act like an RLC circuit, modifying the antenna’s natural frequencies.
• Using aperture tuning, the electrical length of the antenna’s ground leg is adjusted to shift the resonance of the operating band.
• It requires sufficient electronic circuitry for external bypassing.
• It does not require filtering.
• Aperture tuning helps boost isotropic sensitivity and radiated power by optimizing efficiencies for transmit/receive frequencies.
• Example: The QAT3514 device functions as an SP4T switch.

Antenna Impedance Tuning

• This technique broadens the antenna bandwidth, enabling uniform insertion loss and return loss to be achieved at multiple frequencies for both transmit and receive directions.
• Due to the widening of bandwidth, undesired frequencies may be passed. To mitigate this, RF filtering is employed.
• The impedance tuning switch and antenna form an equivalent RLC circuit, similar to aperture tuning.
• Impedance tuning helps to boost power transfer between the antenna and the RFFE (Radio Frequency Front End).
• It requires external passive components for bypassing.
• It requires filtering.

Impedance tuning improves S11 (reflection coefficient) and system efficiency accordingly. However, it does not improve antenna radiation efficiency because the antenna structure remains unchanged. Therefore, antenna aperture tuning is needed to change the radiation principle of the antenna without altering its physical structure.