The Dynamics of the User Effect on Electrically Small Antennas (2016)

The user effect on mobile phones has long been acknowledged as a major contributor to losses in cellular communications.Since the introduction of specific absorption rate (SAR) regulations, the model for quantifying these effects has been based on static measurements in controlled and reproducible environments.While this is a good approach for regulatory testing it is omitting much of the variance seen in a real-life scenario.In real life, the user will not use one static grip on the phone but will move the hand around on the phone in non-deterministic patterns.For classic antenna systems the antenna was a static structure without antenna tuning and therefore the user effect could not be compensated.The only focus was to guarantee that the SAR levels were lower than the legal limits and in some cases that the radiation pattern had a desired shape.For modern smartphones, the antenna system is getting increasingly tunable.This allows designers to consider feed-back systems that can compensate parts of the effect of the user.For such systems, a static user model is insufficient to test the efficiency of the regulation loop.Therefore, this study is focusing on the development of dynamic user effect models and measurement topologies.First a simulation model is presented where the index finger of a 3-dimensional hand model is parameterized.By moving the finger to several locations on the back plane of the phone, a first estimate of the user effect sensitivity of the phone can be obtained.The study presents simulated data for both single antenna systems and multiple input multiple output (MIMO) systems.For antenna measurements, the study introduces a novel device class, the tiny integrated network analyzer (TINA), that is a very small network analyzer used for measurements of the user effect inside of a mobile phone.This eliminates the need for external cables that are normally obstructing the user grip and adding cable effect.The device is finally used for a large-scale measurement campaign involving 100 test subjects performing various tasks on a mobile phone while the TINA is measuring the S-parameters of the phones' antennas.This study is the first to give actual measurements of the coupling between antennas on an electrically small antenna system as well as the first to give measured dynamic user effect data on a fully functional phone in a live network.iii ResumEn mobilbrugers inflydelse p mobiltelefonens antenner har laenge vaeret anerkendt som en betydelig kilde til degradering af signalerne i mobilnetvaerk.Siden introduktionen af specific absorption rate (SAR) regulativerne har tilgangen til kvantificering af brugerens interaktion med mobiltelefonen vaeret baseret p statiske og reproducrbare modeller.Dette er en god tilgang til certificering hvor reproducibilitet er ndvendig, men det udelader megen af den varians som er til stede i et normalt brugsscenarie.En bruger vil ikke hold telefonen p een statisk mde men skift greb p telefonen p en vilkrlig mde.Tidligere var antennesystemerne i mobiltelefoner statiske metalstrukturer uden tuningskredslb, som ikke kunne kompensere for brugerens effekt.Den eneste fokus for brugerinteraktionsmlinger var at garantere, at graensevaerdierne for SAR var overholdt.Moderne mobilantenner bliver mere og mere tunbare.Derved bnes muligheder for, at designere kan udvikle tilbagekoblingssystemer som kan kompensere for brugerens effekt p antennen.For sdanne systemer er en statisk model af brugerinteraktionen ikke tilstraekkelig til at test reguleringssljfens effektivitet.Dette studie har derfor fokuseret p at udvikle dynamiske brugerinteraktionsmodeller of mletopologier.Frste del af studiet praesenterer en simuleringsmodel af en hnd med en parametriseret pegefinger.Nr fingeren flyttes til forskellige placeringer p telefonens bagside opns et frste estimat af telefonens flsomhed overfor brugerinteraktion.Dette studie praesenterer resultater for antennesystemer med bde en og to antenner.Tuil mling af dynamisk brugerinteraktion praesenterer studiet en ny klasse af mleapparater, tiny integrated network analyzer (TINA), som er en yderst kompakt netvaerksanalysator, der kan foretage S-parameter-mlinger direkte