Using impedance tuning to maximize antenna performance in 5G mobile phones
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With the advent of 5G, RF design in mobile phones is becoming increasingly complex, making it more difficult for mobile phone manufacturers to meet stringent performance requirements. As mobile phones include more antennas and support more frequency bands, it becomes increasingly challenging to maintain antenna performance under all usage conditions and frequencies. Impedance tuners can help solve this problem by maximizing RF power transfer under different conditions and between multiple frequency bands. As a result, impedance tuners are increasingly used to optimize performance, reduce design costs and meet 5G requirements. This white paper describes how to use impedance tuners and discusses the relative advantages of different impedance tuner designs. It also uses multiple examples to demonstrate how impedance tuning can be used to significantly improve performance in typical real-world application scenarios.
RF complexity in mobile phones has been growing exponentially over the past few years, and 5G is further increasing the complexity of mobile device design. These make it even more difficult to meet performance requirements, especially given the limited space allocated for RF technology in mobile devices.
Maximizing antenna performance is one of the key challenges. Phone manufacturers are adding more antennas to handle the growing number of frequency bands and wireless standards. As more antennas are placed in a phone, their performance becomes more susceptible to external conditions, such as the phone’s proximity to different materials and the way the user holds the phone. Under these conditions, the antenna impedance can change, resulting in an impedance mismatch between the antenna and the RF front end (RFFE). Antenna impedance also changes when the antenna communicates in different frequency bands. Impedance mismatch reduces the RF power transfer between the RFFE and the antenna, requiring increased transmission power to compensate for the loss, thus affecting the overall RF performance of the phone and shortening battery life.
Impedance tuners solve this problem by matching the impedance of the antenna to the impedance of the RFFE under different usage conditions and over a wide frequency range. This maximizes the RF power transferred between the RFFE and the antenna, helping smartphone manufacturers meet performance requirements for different applications and over a wide frequency range.
Problem: Impedance mismatch between RFFE and antenna
The FFE impedance is usually a constant 50Ω, but the antenna impedance varies depending on the frequency band and usage conditions. When there is an impedance mismatch, the RF power transferred between the RFFE and the antenna is reduced. For example, when a mobile phone transmits a signal, not all the available power from the source (RFFE) is transferred to the load (antenna), which can cause up to several dB of signal loss. The amount of loss depends on the size of the mismatch between the RFFE and the antenna impedance. The following figure shows the system loss under different VSWR (voltage resident waveform radio) conditions.
Impedance tuners are a key solution to address antenna efficiency issues caused by the increasing RF complexity in mobile devices. By increasing the RF power transferred between the RFFE and the antenna, impedance tuners help smartphone manufacturers maximize performance across different applications and frequency bands. As a result, manufacturers are integrating impedance tuners in more and more mobile devices, especially with the transition to 5G.
Click here to download the eBook "Using Impedance Tuning to Maximize Antenna Performance in 5G Mobile Phones" to view more content including the following passages:
Solving impedance mismatch problems
What is an impedance matching network?
Tuner gain as a metric for impedance matching networks
Building impedance matching networks using tunable capacitors and inductors
Comparison of different types of matching networks Bypassing
matching networks using switches and implementing inductor tuning
The impact of quality factor on tuner gain
Examples of using impedance tuners in real-world antenna problem scenarios
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