presented by: john lienau rf engineer...•a 3 db loss in antenna gain is equal to a loss of half...
TRANSCRIPT
Presented by: John Lienau – RF Engineer
• Author Introduction
• LS Research – who we are and what we do
• Antenna Review – basic terms and common parameters
• Device Considerations
• Common Antenna Topologies
• Antenna Tuning
• Wireless Range
• LSR Overview
• Graduated from Marquette University 2008 with BSEE
• Graduated from Marquette University 2009 with MSEE
– Focused on Electromagnetic Theory, Numerical Techniques, and Antenna Theory
• Began at LS Research April 2010
– RF Design Engineer
– Antenna Design Engineer
• LS Research delivers turnkey wireless solutions with design services, RF
module solutions, manufacturing, and an on-site FCC / CE / IC approved
test facility.
• We are part of Texas Instruments’ Elite Design House program and MCU
and Low Power RF Developer networks.
• LS Research has over 30 years of proven wireless leadership with locations
in Cedarburg and Madison, WI.
RF Modules
Design Services
Testing Services
“It is easy to design a marginal performing antenna but
difficult to design a really good antenna”
The antenna can be the one of most daunting
components of RF design, it is the most important part
and yet often the last consideration.
The antenna makes it wireless!
• The antenna is a key component of a successful wireless design
• An antenna is simply a conductor by which electromagnetic waves
are sent and received from.
• An electrical signal from the radio induces a current on the conductor
which results in electromagnetic waves.
• The shape, size, and material of that conductor determine the
antenna characteristics.
• Size of the antenna is dependent on frequency!
• Depending on the antenna type, the size is between λ/4 and λ/2
• However, the shape of the conductor and material around it can
be used to shrink the antenna
– Shrinking the antenna, will reduces performance
Frequency l / 4 (in) l / 2 (in)
5 GHz 0.59 1.2
2.4GHz 1.2 2.5
915MHz 3.2 6.4
868MHz 3.4 6.8
433MHz 6.8 13.6
Wavelength (λ) = Speed of Light Frequency
• Your antenna has an impedance that is dependent on frequency.
• Impedance is controlled by antenna dimensions, matching
components, and nearby materials.
– The same antenna will have different impedances at different
frequencies!
• In order to have maximum power transfer between the radio and
the antenna, they must have matching impedance.
ZAntenna
ZRF Amp
Input Power
Reflected Power
• VSWR and Return Loss
characterize an antenna’s
impedance match.
• Voltage Standing Wave Ratio
(VSWR) is the ratio of the
voltage maximum to the
voltage minimum of the wave
waveform.
• Return Loss (S11): A measure
of how much energy is
reflected back by the antenna
due to mismatch.
1
1VSWR
1
1log20)log(2011
VSWR
VSWRS
dB
Antenna gain describes how well an antenna converts input power to radio waves.
isotropic
dipole dipole
Gain patterns are typically given in the principle plane of interest.
Power measurements are referenced to isotropic antenna (dBi) as a theoretical model for comparison with all other antennas
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]/[;
4
srW
srW
P
U
U
Ug
t
rad
isotropic
radt
Gain patterns are like a balloon, the antenna designer can ‘push’ around power and shape the pattern as desired.
-30
-25
-20
-15
-10
-5
0
5
30
210
60
240
90
270
120
300
150
330
180 0
____ Total Gain (dBi) min: -18.7 max: +2.2 avg: -1.2
-30
-25
-20
-15
-10
-5
0
5
30
210
60
240
90
270
120
300
150
330
180 0
____ Total Gain (dBi) min: +0.5 max: +1.6 avg: +1.0
“It is easy to design a marginal performing antenna
but difficult to design a really good antenna”
• A 3 dB loss in antenna gain is equal to a loss of half the
TX power!
• Antenna gain affects both TX power and RX sensitivity.
• Antennas are one of the few electronic components that
cannot be adequately characterized on the lab bench
• Internal or external antenna
• Enclosure
– What is it made out of? Plastic? Metal?
– Where can the antenna be placed? Pick more than
one location!
– What will be near the antenna?
• How will the device be used? Who is using it?
– Mobile?
– Fixed?
• Incorporate antenna location into your design
process!
Distribution of
Current Magnitude
Charge
Accumulation
Current
Flow
Feed
Point
Voltage and Current at the feed will affect the impedance seen by the
transmission line
• Enclosure (dielectric loading)
• Human Body Loading (absorption & detuning)
• PCB Stack & Material (dielectric constant)
• PCB Ground Plane Size Important
• Just Like Real Estate: “location, location, location…”
• Cable and trace losses – avoid long runs to antenna
• Tune the antenna in its final environment
• Say NO to metallic enclosures, foil labels and metal flake paint
• Many different types
– Meander, F, Monopole
• Advantages and
Disadvantages
– Performance varies
depending on space
– Requires skilled
resources to properly
design
– Wide range of
performance – bigger is
always better
• Many different
combinations of wire
antennas
• Advantages and
Disadvantages
– Requires space in your
device
– May need mechanical
support
– Good gain and
bandwidth
– Precision in bending,
cutting, and placement
needed
• Many shapes and
sizes
• Advantages and
Disadvantages
– Can be complex and
very device specific
– Complicated to
manufacture
– Hand assembly
– Good gain and
bandwidth
• Chip Antennas
• Provide a small antenna
solution at the cost of
gain.
• Cheap and easy to
incorporate in the
manufacturing process.
• Directivity and gain
determined by PCB
• Often datasheets claim
much higher.
I’ve got my antenna! Am I done?
Nope. It’s time to put the antenna in
your product…
• The near field is related to
the current distribution on
the antenna
• Perturb the near field, you
change the current
distribution and vice versa.
• Critical to know the
electrical properties of
nearby materials.
– Conductive?
– Loss characteristics
Trace
F-Antenna
• ‘Matching’ refers to the use
of inductors and capacitors
to transform the antenna
impedance to 50 Ohms.
50 Ohm Output
From T-Line
1.0 pF
1.8 pF
4.3 nH
8.2 pF
Before After
• Range is dependent on the
environment your device
operates in.
• All object have unique
material properties that affect
the RF signal differently.
• Metal objects, cement walls,
water, have very negative
impact.
• ‘Line of Sight’ – no
obstructions between TX and
RX
• Office – lots of walls, cubes,
people
• Manufacturing - heavy
machinery, thick solid walls,
• Most datasheets state ‘Line of
Sight’ range
• Buildings are the most
unpredictable
environments
• You have no control
over how a consumer
actually uses your
device
• Plan for worst case
scenario
– Link Budget
• Floors 10-20 dB
attenuation, interior
walls 5-10 dB
• Indoor environments
produce many reflections
• Multipath will cause
additive and subtractive
interference.
• May eliminate nulls in
antenna pattern
100 200 300 400 500 600 700 800 900
-90
-85
-80
-75
RS
SI
dB
m
Sedona Module Performance
20 40 60 80 100 120 140 160 1800
50
100
Packer
Err
or
Rate
Sample Number
20 40 60 80 100 120 140 160 180
-90
-85
-80
-75
Avg R
SS
I dB
m
• Two antennas are better
than one
– Improve gain pattern
– Move out of nulls
• More expensive and
complex
• Antenna measurements need to be done in a location that:
1. Reflect no radiated energy
2. Is devoid of any outside RF energy
• Typically the measurements of interest include:
1. Measure the radiation pattern (See Above).
2. Measure the radiated power across the bandwidth of interest.
z
x
y
+ =
LS Research is a global leader in enabling advanced wireless technology platforms.
Start to finish, whatever the requirement, LS Research has the right solution.
• Design Services
– Wireless electrical / RF
hardware design
– Software design:
Embedded, FPGA, DSP
– Antenna simulation,
design, and testing
– EMC failure analysis
– Industrial Design
– Mechanical Design
– Turn-Key Manufacturing
• Testing Services
– EMC testing and radio
certification services:
FCC / IC / ETSI and
more…
– EMC failure analysis
• RF Modules
– TiWi-uB2™: Bluetooth ® /
BLE
– TiWi™: WiFi - Bluetooth ® /
BLE - ANT+
– ModFLEX™: 802.15.4 2.4
GHz and 900 MHz ZigBee -
6LoWPAN - proprietary
protocols
RF Modules
Design Services
Testing Services
• 802.11 a/b/g/n
• Bluetooth / BLE
• 802.15.4 / ZigBee / RF4CE
• NFC / RFID
• DECT
• 6LoWPAN
• ANT+
• Remote Keyless Entry 315/390/433
• Medical Implant Communications Service (MICS)
• <1 GHz, 2.4 GHz, 5.8 GHz, ISM
• White Spaces
• Mesh Networks
• GPS
LS Research is one of few facilities that can simulate, design, tune
and characterize antenna performance in real world configurations
all at the same facility.
– Complete antenna simulation
CST Microwave Studio 3D
Enclosure and antenna analysis
Body model simulations
– Network analyzer
– Anechoic antenna test chamber
Gain and antenna patterns on-site
• Antennas
2400 – 2483 MHz Dipole 2dBi for reverse polarity SMA
Dual band 2400-2500MHz, 5150-5850MHz Dipole
2dBi for reverse polarity SMA
902 – 928 MHz Dipole 2dBi for reverse polarity SMA
Select Chip Antennas
• Cable Assembly
U.FL to reverse polarity SMA bulkhead (female)
Antenna Shop Program Overview
Remove the guesswork!
Full complement of tools + experience
Match and optimize off-the-shelf solution or custom
design
Antenna examples include:
PIFA Patch Helical
Dipole Loop Slot
Monopole PCB Medical Implant
Program Overview
LSR has created 7 simple options to choose from to fit your antenna requirements
Program Overview
Option Cost Average
Duration
Antenna patterns on existing implementation $3,500 1 wk
Antenna match of existing implementation $6,800 1 wk
Antenna match of existing implementation (with patterns) $9,000 2 wks
Implementation of COTS antenna onto PCB $11,000 2 wks
Implementation of COTS antenna onto PCB (with patterns) $13,200 3 wks
Custom antenna design with defined enclosure $16,000 3 wks
Custom antenna design with undefined enclosure $22,000 4 wks
COMING SOON:
FlexAntenna Products
Provide companies with a more flexible antenna
platform
that requires less user design, and error in
implementation,
to ensure maximum antenna performance.
The initial platform of embedded antennas will
include:
2.4 GHz FlexPIFA
2.4 GHz FlexNotch
Features Include:
Adhesive mounting for accommodating of a
range of enclosure types and shapes
Tuned for plastic, metal and body worn
enclosures
FlexAntenna Overview