Antenna Systems & Technology - Fall 2015 - (Page 8)

FEATURE ARTICLE Dual Tuning - The OEM's Secret Weapon in Spectrum Proliferation By Larry Morrell, Executive Vice President, Marketing and Business Development Cavendish Kinetics The large and rapidly growing demand for data over wireless networks is well-known, but the scope of the problem for smart phone makers is not widely appreciated. Wireless data volume in the US has grown by 20 times during the past five years to 4.1 Trillion Megabytes of mobile data in 2014 according to the CTIA 2014 survey. While the US leads the world in data demand, the global trend is just as staggering. Wireless network operators around the globe are expanding spectrum holdings, investing in 4G infrastructure and even pursuing unlicensed spectrum to fulfill the demand. One technical solution just being rolled out as part of Long Term Evolution-Advanced (LTE-A) is carrier aggregation (CA): combining component carriers of 5 MHz each to attain 10 MHz to 20 MHz channels for users. These bands can be adjacent to each other or widely divergent. This adds considerable complexity to both the fixed wireless network and the mobile device in the hands of the user. Carrier Aggregation as a Solution The world wide standards body 3GPP has defined CA groupings based on operator requests, which are based on operator frequency holdings. So almost every operator has a grouping request different from every other operator. Since the vast majority of the data flows from the network to the user's device, the initial deployments are for Downlink (DL) CA. Sprint reports that the DL to UL ratio is currently running between 5:1 and 7:1; a significant waste of a radio network architecture that was originally (2G) designed to be symmetric. DL CA skews the network capacity in favor of DL and allows for more efficient network use. In many ways the network side is the simpler side of the link since a fixed network has far fewer constrains on power, size and cost. Device makers, however, now must be able to build not only radios that can cover 698 MHz to 2.7 GHz (and soon up to 3.5 GHz), but the radios must be able to operate on multiple frequencies simultaneously - in just about any combination you can think of. With more than 40 frequency bands defined (and growing) the number of possible combinations is an uncomfortably high number: approaching 100 operator-requested combinations. User Device: Antenna is the Weakest Link The handset antenna systems generate two to three times the loss of the other components and as antennas are allocated less and less volume, but need to cover wider and wider frequencies - the antenna losses will grow if traditional passive antennas are used. Equation (1) shows the relationship of antenna volume (a) to wavelength (λ), efficiency (η) and fractional bandwidth (Δf/f). This relationship was developed in the 1940s by Harold Wheeler[1] and elaborated on by Lan Jen Chu [2]. It has been shown empirically to reflect antenna performance in electrically small antennas by Daniel Sievenpiper et al.[3]. Note that as the bandwidth grows, antenna efficiency must shrink, and either the bandwidth or the efficiency shrinks by the cube of the wavelength; bad news for lower frequencies. Bands in 700 MHz range and below will have radiated efficiency of 10 percent or less within the small volumes allocated within smart phones. The equation tells us that to have a higher efficiency requires a narrower bandwidth. 8 Antenna Systems & Technology Fall 2015 www.AntennasOnline.com http://www.AntennasOnline.com

Table of Contents for the Digital Edition of Antenna Systems & Technology - Fall 2015

Editor’s Choice
Dual Tuning - The OEM's Secret Weapon in Spectrum Proliferation
A Hybrid "Hexa-Band" Cellular Antenna
Tunable and Fixed Filtering Solutions Enhance Dynamic Range of 4G-LTE Measurements
Antenna Systems 2015: Conference Preview
Low-Cost and Frequency-Selective Metamateiral and Its Antenna Applications
Antennas
Components/Subsystems
Software / System Design
Industry News
Hiding a DAS
Marketplace

Antenna Systems & Technology - Fall 2015