Smartphones have come a long way since the gray, brick-sized design of the late eighties. Today, consumers demand thinner, smaller handsets and, in order to meet this trend; smartphone manufacturers often have to reduce antenna volume within their design. Since smaller antennas typically do not offer the same performance as larger ones, the result is an increase of dropped or missed calls and lower achievable data rates. Adding to this problem, smartphones now also need to adapt to the increasing network offered data rates and wider band coverage range (698-2690 MHz) of 4G and 4G+ networks.
In order to meet new carrier requirements and consumer expectations, RF tuning has become essential in smartphone designs.
Traditional tuning solutions, called “open-loop”, enable the device to better support multiple LTE/HSPA+ bands and improve antenna performance, but do not adapt to variable operating conditions, or use cases. Current solutions typically select a fixed match pattern to provide the optimal smartphone performance for a certain use case, (usually either for freespace, head-hand, or a compromise). While this is an improvement over non-tuned antennas, the use of standard matching configurations only partially address real-world environments the handset experiences in its normal operation.
Think of the different ways in which you use your smartphone in a given day- texting a friend, typing an email, or making a phone call. Each of these use cases affect how your handset performs. When you hold your phone to your ear or grip it with your hand, you are actually detuning the handset and blocking the antenna signal. This leads to a reduction in Total Radiated Power (TRP) (the measurement of how much power the phone is transmitting) and Total Isotropic Sensitivity (TIS) (the measurement of how sensitive the smartphone is to “receive” signal levels).
The most advanced system for adapting to use case changes are closed-loop systems. These take real- time measurements of the antenna impedance and adjust the match, also in real-time, to accommodate the variations experienced by the antenna in different use cases.
Closed-loop tuning needs to measure both phase and amplitude of signal reflected from the antenna to determine the antenna impedance, as shown on the Smith chart. Once the complex impedance is known, an algorithm is applied to determine optimal match configuration, which is then applied in real time.
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Comment
Gareth Weale
2015-04-17 06:58:46.0
Comment rating:0
ON Semiconductor is now marketing a solution to the smartphone market, that allows real time measurement of the complex impedance of the antenna (called the "Sense IC" - built into a module - TML-200D,E,F), a phone then employs an algorithm running on the cellular modem processor to calculate the optimal tunable match to offer premium device performance.
Tom De Ryck
2015-04-16 23:50:26.0
Comment rating:0
What's the tool used to do the measurement/analysis? Custom made hardware/software? Or a commercial tool?
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