Bob Giometti Vice President R&D and Engineering, SkyCross [email protected] New Antennas for Mobile Technology Presented at the Antenna Systems Conference December 12-13, 2013 Las Vegas, NV
Bob Giometti Vice President R&D and Engineering, SkyCross [email protected]
New Antennas for Mobile Technology
Presented at the Antenna Systems Conference December 12-13, 2013 Las Vegas, NV
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Contents
1. Introduction
2. LTE-A and the Mobile Device Antenna
3. LTE-A: Impact on the Antenna System a. Requirements
b. Carrier Aggregation c. Drivers for Antenna Tuning
4. Enabling Technologies a. Aperture Tuning b. Tunable Match Network c. Hybrid Approach d. Co-location of antennas e. Isolated Mode Antennas (iMAT) - Beam Forming Application
5. Summary
Introduction
- Over 20 years experience in the wireless industry
- Mobile phone product development at Motorola/Google
- Electrical design lead for the original RAZR
- BSEE/MSEE Illinois Institute of Technology
- Joined SkyCross as VP of R&D and Engineering Jan. 2013
Background/Bio
Page 4
LTE- A and the Mobile Device Antenna
• Many bands (40+ and counting….) – 700 MHz in US (sub-bands for AT&T and Verizon) – AWS (2.1/1.7 GHz) in US – 790-862 MHz in Europe – 2.6 GHz FDD – mainly in Europe – 2.6 GHz TDD – China, Europe – 2.3 GHz TDD – China, Korea, India – 600MHz on the way!
• GPS, BT, FM, NFC,…
• WiFi (Dual Band)
• Tx Diversity
• MIMO 2x2, 3x3, 4x4,…
• Carrier Aggregation
– Low/Low, Low/High, High/High
LTE-A: Squeezing Even More Into The Mobile Device
Page 6
Challenges facing today’s Mobile Device Antenna Engineer
Page 7
Traditional antenna performance is inadequate to meet market demands for: Increasing number of frequency bands (4G/LTE ) Increased data traffic clogged networks Real life use cases (head, hand, slider phone ) Thinner phones Smaller antennas Quality of Service challenges
Bands of Interest vary by: Country / Region Network provider Protocol
Need for advanced adaptive antenna/RF solutions
“Advanced Smart Antennas” provide improved RF Performance & Increased Flexibility
Page 8
LTE-A: Impact on the Antenna System
Page 10
Enables more users, more applications, and a better experience
Source: Rysavy Research/4G Americas, 2012
LTE 2010 to 2012 •5 or 10 MHz Radio Channels •2X2 Multiple Input Multiple Output (MIMO)
LTE- A 2013 to 2016 Higher Capacity/Throughput and/or Efficiency
•Wider Radio Channels: 20 MHz •Carrier Aggregation: up to 100 MHz •Advanced Antenna Configurations •More Advanced MIMO (Higher Order, Multi-User, Higher Mobility) •Coordinated Multipoint Transmission •Het-nets (Microcells/Picocells/Femtocells)
• Easiest way to arrange aggregation: use contiguous component carriers within the same operating frequency band (as defined for LTE), so called intra-band contiguous.
• May not always be possible, due to frequency allocation scenarios.
• For non-contiguous allocation it could either be intra-band, i.e. the component carriers belong to the same operating frequency band, but are separated by a frequency gap, or it could be inter-band, in which case the component carriers belong to different operating frequency bands.
Carrier Aggregation Considerations
Page 11
• LTE smartphones are challenged to achieve tightening carrier performance expectations – 4G LTE speeds/capacity require MIMO (multiple LTE antennas) – Growing number of operating frequency bands (number of antennas) – Aggressively styled device form-factors (constrained space)
• OEMs seeking new technical solutions to address challenges – Tunable antenna solutions seen as the desired approach – Progressive OEMs already initiating smartphone architectures that support
tunable antenna modules
• LTE-A Requirements – Carrier Aggregation – Higher Levels of MIMO – Tx Diversity
LTE-A Drivers for Antenna Tunability
Page 12
Antenna Tuning Technologies
Tunable vs. Passive Antennas
Page 14
• Integrates tuning elements, antenna, and interface
• Smaller size (smaller than
conventional passive antennas at same efficiency) or higher gain in same size to reduce Tx power consumption (increased battery life)
• Separate from and complementary to feed-point impedance matching
• Supports Carrier Aggregation requirements
• Primary/secondary antennas can
be co-located for greater space reduction
• Potential to simplify filter circuits • Simple 1 or 2 bit interface and
control
Motivation for Tunable Antennas 1. Greater band coverage +MIMO in accepted form factor allocated
space
2. Smaller Antenna: 1000 cubic millimeters or less (handset OEMs)(need more tuning states)
3. Head/Hand Effect mitigation (requires sensor and algorithm) (Operators)
4. Higher ASP stemming from integration of antenna and tuning elements/control (Antenna Suppliers)
5. Lower VSWR (PA Suppliers)
6. Reduced Filter Requirements (Filter suppliers)
Page 15
Aperture Tuning • Integrates tuning element, antenna,
and interface
• Antenna resonance is changed directly by the tuning element.
• Allows antenna to be made smaller or cover more bands than with passive antenna
• Simple interface and control to achieve open loop coverage on a band-by-band basis
• Often used with tuning devices such as switches or DTCs for open or closed loop control.
• Can be thought of as a “coarse tuner”
Tunable Matching Network • Used to improve VSWR match to
antenna.
• Not considered as producing optimal radiation efficiency compared to Aperture Tuning
• Improves power coupled to antenna over frequency of operation and under varying usage or environmental conditions
• More complex interface generally with 6 or more bits of control
• Can use analog tuning devices such as BST and Varactor diodes, may be open or closed loop
• Can be thought of as a “fine tuner”
Aperture Tuning (AT) vs. Tunable Matching Network (TMN)
Page 16
Efficiency Comparison Between Passive Broad Band and State-Tuned-Aperture Antennas
Page 17
State 1 State 2 Broad Band
Low Bands High Bands
Significant improvement in low band performance
>2 dB
Minimal impact to high band performance
~0.8 dB
Page 18
Hybrid Approach: Aperture + Match Tuning
RF (Port 1)
Microcontroller Control Algorithm
Flash Memory
RF (Port 2)
Tunable Matching Network (Fine Tuner)
Optimize Performance
Diversity Aperture Tuned Antenna (Coarse Tuner) Band Selection
MIPI RFFE GPIO Control
Tunable Matching Network (Fine Tuner)
Optimize Performance
Diversity Aperture Tuned Antenna (Coarse Tuner) Band Selection
Antenna Co-Location
Page 20
Antenna Proximity Problem • Far apart
– Negligible coupling between antennas
– spatial separation makes antenna patterns unique
– How far: generally more than about half wavelength (17 cm at 900 MHz) – size not feasible for many consumer products
• Close together - coupling between antennas may
be a problem (RX saturation or desense, TX distortion)
- coupling hurts radiation efficiency as power goes into neighboring antenna and not to far field
- patterns lose uniqueness and are highly correlated (loss of MIMO capacity or loss of diversity gain)
- Reality of many consumer products
Antenna starts to couple more to its neighbor than to the far-field
Page 21
The MIMO Antenna Solution for 4G
: Isolated Mode Antenna Technology
• iMAT is a patented technology that allows a single antenna structure to behave like multiple antennas through the use of multiple feed points.
• Each feed point accesses the single antenna as if it consisted of 2, 3, or more independent antennas that are highly isolated with superior link performance gain.
• This compact solution is applicable to any mobile device! iMAT supports legacy networks and is essential for next generation protocols that require diversity or MIMO.
Patented Technology
Page 22
Enables Multiple Antennas in Small Spaces
Antenna Requirements • Diversity/MIMO • High isolation • High radiation efficiency • Low correlation coefficient • Small size
d
Conventional Smart Antenna
Approach
Isol
atio
n dB
0
-10
-20
-30 Frequency
60
50
40
30
Effi
cien
cy %
ISO
EFF
SkyCross iMAT Solution
Isol
atio
n dB
0
-10
-20
-30 Frequency
60
50
40
30
Effi
cien
cy %
ISO
EFF
1 2
The iMAT solution offers high efficiency, superior isolation, and low correlation coefficient while maintaining equivalent return loss, with a single antenna!
Technology Applications • WiFi and/or WiMAX • 4G/LTE • HSDPA / HSUPA • 1XEVDO • 802.11n, 802.11ac • Mobile video (CMMB, T-DMB,
DVB-H)
SkyCross Antenna Technology
Breakthrough!
1 3 . . . 3 . . .
d
2
Page 23
iMAT: Far-Field Patterns
• Each resonance mode has a unique far field pattern • With iMAT approach each antenna port couples to a different
combination of the two fundamental modes • The resulting far-field patterns are also unique to each other
resulting in low ECC
Combination
- =
+ =
Pattern phase reversal
Farfield pattern from Port 1
Farfield pattern from Port 2
Common Mode
Differential Mode
Page 24
iMAT: Concurrency of Isolation and ECC
• With iMAT Port-to-port isolation and low far-field correlation are obtained from the same design optimization at the same frequency
• Both result from the condition where the
near fields associated with Port 1 are orthogonal from those associated with Port 2
• The proper conditions are achieved
through resonance and so are inherently optimized to a particular frequency band or bands
Port-to-Port Coupling
Pattern Correlation
frequency
frequency
State 1 State 2
• Aperture tuning in SkyCross tunable antenna modules permits the actual radiating elements to be configured for optimal performance at each desired frequency band
• SkyCross ST-iMAT and Aperture Tuning deliver: Smaller size Improved device performance Network improvement (fewer dropped calls, increased network capacity) Superior performance versus simple feed-point matching
SkyCross ST-iMAT™ (State-Tuned iMAT Antenna Module for Smartphone)
VersiTune-LTE™ Tunable Antenna Module
Smartphone Implementation
iMAT Radiating Elements
Tunable Antenna Module
Page 25
Tunable iMAT “Isolation Notch” Drives Multiband Antenna Performance
iMAT des ign a llows “contro l” of the is o la tion be tween ports . Drives h igher e ffic iency and lower corre la tion coeffic ien t
• Isolation is a measure of signal interference separation from one feed point to the other • Correlation coefficient is the degree to which the two RF signals are distinct from each other
Page 26
Page 27
LTE-700 Corner to Corner Conventional Antenna Design
VSWR: <2:1 Efficiency:
30-40%
CC: >0.8 Coupling:
-4dB
Patterns almost identical
iMAT LTE-700 Antenna Design
VSWR <2.2:1
Isolation:
<-13 dB
Efficiency 50-58%
CC: <0.35
Significantly different patterns
50x100mm GP
Page 28
iMAT Advantage vs. Dual Antenna: Correlation Coefficient
iMAT Antenna Patterns
Dual Antenna Patterns
Greater pattern diversity results in lower Correlation Coefficient for iMAT vs. Dual Co-polarized Antenna
Independent analysis of iMAT vs. Conventional antenna for handsets shows iMAT delivers significant improvement in Correlation Coefficient
Page 29
Multiband Antenna Efficiency: ST-iMAT
State 1 State 2 State 3 State 4 State 5 State 6
Sing
le P
ort O
nly Primary
Spec
Diversity Spec
Meas ured Data : S ta te Tuned iMAT configura tion covering a ll LTE and Legacy 3G bands in 6 tun ing s ta tes
Page 30
• Phone chassis: ~58x120mm • Modular Antenna: x=59mm, y=9.5mm
(from display edge), z=3.7mm Antenna volume (incl. keep out) = 2075mm3 Fully populated antenna module with
speaker, microphone, USB3
Versitune-LTE Antenna Speaker Module Design Example
y =9.5mm
Antenna Elements
Flex PCB Antenna (Double Sided FPCB)
Plastic Carrier With Speaker Box
Embedded Speaker
Audio Port
Microphone
USB Connector
Tuning Components
Page 31
Versitune-LTE Module Performance Summary
Key Features: • Speaker, Microphone,
USB connector and associated flex films integrated into assembly
• Vibrator, cameras an associated flex films in close proximity to the antenna
• Open Loop tuning with 3 tuning states for each low band: 17, 5, 8
• Supports CA for bands 4 & 17
Versitune Performance Summary Simulations
Main TX Main Rx
Band & Freq Eff
(dB) Goal delta
Eff (dB)
Goal delta
1 1920 - 1980 -2.7 NS -3.9 NS
2 1850 - 1910 -2.9 -3 0.1 -2.6 -6 3.4
4 1710 - 1755 -3.0 -3 0 -3.7 -4 0.3
5 824 - 849 -3.8 -4 0.3 -4.2 -5 0.8
8 880 – 915 -3.4 NS -3.7 NS
17 704 - 716 -3.8 -4 0.2 -4.4 -5 0.7
Free Space Cross Correlation Diversity RX
Band & Freq CC Goal delta Eff
(dB) Goal delta
1 2110 - 2170 0.0 NS -2.8 NS
2 1930 - 1990 0.0 0.5 -0.5 -5.7 -7 1.3
4 2110 - 2155 0.0 0.5 -0.5 -2.4 -7 4.6
5 869 - 894 0.3 0.5 -0.2 -8.0 -8 0
8 925 – 960 0.1 NS -8.1 NS
17 734 - 746 0.4 0.5 -0.1 -5.1 -8 2.9
Page 32
Versitune LTE Efficiency - Primary/Secondary Port Primary Port
Secondary Port
Performance data includes speaker, cameras, microphone, vibrator, micro USB and associated flex interconnects in the antenna near field
Tuning states 1,2,3
Page 33
Versitune LTE Coupling (S12) - Primary/Secondary Port Primary Port
Secondary Port
Performance data includes speaker, cameras, microphone, vibrator, micro USB and associated flex interconnects in the antenna near field
Page 34
Versitune LTE - Envelope Correlation Primary
Secondary
Performance data includes speaker, cameras, microphone, vibrator, micro USB and associated flex interconnects in the antenna near field
Page 35
iMAT 2x2 Antenna
iMAT 2x2 Beam Forming Application
Page 36
Antenna Beam Forming Problem for Handset Application
• Beam forming is accomplished by combining signals in two or more antennas at different phases
• For conventional antennas, as antenna separation decreases, the benefits of beam forming diminish due to the detrimental effects of antenna mutual coupling
• The separation between antennas, in terms of wavelength, is small for handset and mobile device applications (typically < 0.1 wavelength)
~
~
Antenna Array Combined Signal
Phase Shifter
s <0.1 wavelength at cellular frequencies
Page 37
• A balanced iMAT design may be well suited for beam forming applications
• Both ports of iMAT antenna can be driven simultaneously
• Applying the same RF signal to both ports with a variable relative phase delay enables a beam forming solution
• Beam forming can provide 3 dB signal gain at the tower for same client device TRP
• Because there are two PAs, each needs to provide only half the total output power of the traditional PA.
Port 1 Excitation
Ф TX
PA
PA
iMAT antenna
Beam Forming – iMAT Technology
Page 38
Page 39
Beam Forming Application Analysis Comparing iMAT to Conventional Antennas
Analysis Result – single iMAT antenna produces better beam forming gain than a pair of conventional dipoles
Improvement due to iMAT
Summary
1. LTE-A requirements are driving the need for new, more complex antenna technologies
2. Close attention to the antenna early in the design stage is even more critical due to higher levels of complexity
3. Antenna designs that may utilize a combination of technologies can be used as a competitive advantage that allows for product differentiation
Page 40
This is truly an exciting time to be a mobile device antenna designer!
THANK YOU!