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www.optenni.com www.optenni.com
Optenni Lab
Easy-to-use impedance matching tool for
antenna designers
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Optenni Lab • Optenni Lab is a fast and easy-to-use matching circuit
generation and antenna analysis tool tailored for
antenna designers
• Main features:
– Fast automatic matching circuit generation including a
component library and sensitivity analysis
– Simultaneous multiport matching
– Estimation of obtainable bandwidth of antennas at various
frequencies using the bandwidth potential technique
– Calculation of worst-case isolation for two-antenna
systems
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
MATCHING CIRCUIT
GENERATION
Main Features of Optenni Lab
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Traditional matching circuit generation
1. Using a circuit simulator, guess a suitable matching
circuit topology and give initial values for the
components
2. Set up frequency markers manually
3. Try to tune the circuit values by hand
4. Try to use the optimization features of the circuit
simulators
5. If the results are not good, start again and try
another topology
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Problems with the traditional method
• Circuit simulator skills needed
• Theoretical impedance matching knowledge needed
to select the matching circuit topologies
• Difficult to choose a correct topology for
multiresonant cases
• Optimization routines are difficult to use
– Setting frequency ranges is tedious
– Optimization criteria might not be the best ones
• Whole process takes many laborious iterations and
possibly hours
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Optenni Lab: Matching circuit generation 1. Select antenna impedance file
(multiport S parameters from a Touchstone file)
2. Select termination impedances
3. Select frequency ranges
4. Select number of components in matching circuits
5. Click OK
• Whole procedure takes less than 30 seconds
• No impedance matching or circuit simulation skills needed
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Results of matching circuit generation
Optenni Ltd, May 22, 2013
All previous results available
in a project tree
S parameters (S11, S21) through
the matching circuit
S11 on the
Smith chart
Generated
circuit
Multiple
topologies
generated
Circuit
performance
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Component library
• Optenni Lab includes a library of
commonly used inductors and
capacitors
• Initially almost 30 component series
from three major manufacturers are
supported and more are planned
• The optimization using components
from the library is fast and easy
• Component library is also compatible
with sensitivity analysis
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Sensitivity analysis
• The sensitivity of the results with
respect to component
tolerances can be analyzed for
both the generic component
models and the library models.
• Also yield and minimum
efficiency is calculated
• The sensitivity analysis only takes
a few seconds
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Optimization of efficiency
• For matching circuits with lossy matching
components, Optenni Lab is optimizing for S21,
which is equivalent to the total efficiency of the
matching circuit (including both impedance mismatch
losses and thermal losses in the matching circuit
components)
• Optimization of the impedance match alone would
lead to suboptimal total efficiency
• In many other programs it is difficult to optimize for
the total efficiency (S21).
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Options in matching circuit generation
• Manually given topologies
• Losses in matching circuit
components: S21 of circuit
optimized, component
losses calculated
• Fixed component values
• Limits for component
values
• Interactive tuning of
generated circuits
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Impedance trace • Impedance trace shows how
the components change the
impedance on the Smith chart
at the visualization frequency
• Very useful feature for
understanding the operation of
the matching circuit
• Can be combined with
component tuning and
interactive selection of the
visualization frequency
Optenni Ltd, May 22, 2013
Effect of series capacitor
Effect of shunt inductor
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SIMULTANEOUS MULTIPORT
MATCHING
Main Features of Optenni Lab
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Main features
• Simultaneous multiport matching compatible
with automatic topology creation,
component library, tolerance analysis etc.
• For antenna applications: optimization of
efficiency
• For filters or amplifiers: optimization of S21
etc.
• Arbitrary number of ports
• Termination of ports (internal ports for
single components)
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Multiport antenna matching
• Not enough to have good matching (e.g. both |S11|2
and |S22|2 small)
• Not enough to have good matching and isolation
(|S11|2 , |S21|
2 and |S22|2 small)
• Need to consider antenna total efficiency, taking into
account matching circuit losses and coupling to other
ports
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Multiport antenna matching
• Easy to use: just click on
the ports to set the
frequency ranges and the
circuits to set number of
components or topology
• Multiple topologies
optimized for each port
• Fast parallel optimization
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Output data
• Circuit topology
• Efficiencies
• S parameters
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Additional options
• Ports can be terminated using a
single component (e.g. internal
ports in EM simulations used
for component placement)
• Specifications for efficiency stop
bands and isolation
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
General multiport matching
• Applications: amplifiers, filters, switches, coupled coils
etc.
• Typical figure of merit: |S21|2 to be large in passband
and small in stopband
• Maximum possible |S21|2 given by the concept of
electromagnetic isolation
• Targets: pass and stop bands for Sij
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
ESTIMATION OF
OBTAINABLE BANDWIDTH:
BANDWIDTH POTENTIAL
Main Features of Optenni Lab
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Estimation of obtainable bandwidth • The obtainable bandwidth
of an antenna through a
two-component matching
circuit can be quickly
estimated using the
bandwidth potential
technique
• The analysis makes it easy
to compare antenna
prototypes (without
matching them explicitly)
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Benefits of bandwidth potential
• Quikcly shows the obtainable bandwidth of a
prototype without explicit tuning
• Differently matched antennas can be compared
• Can be used to select the best antenna candidate
• Shows at which frequency the best bandwidth is
obtained
• Can be used to verify the antenna operation: best
bandwidth should be obtained at the operation
frequency bands
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Example of bandwidth potential usage
• Ground plane: 40 mm by 100 mm
• Patch: 25 by 20 mm, height 5 mm
Optenni Ltd, May 22, 2013
Case 1 Case 2: 19 mm by 14 mm removed
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Impedances of example antennas
Optenni Ltd, May 22, 2013
Based on original unmatched
impedances it is difficult to
say which antenna is more
wideband and how large
bandwidth could be
obtained.
www.optenni.com www.optenni.com
Bandwidth potential results
Optenni Ltd, May 22, 2013
Case 1 Case 2
Bandwidth potential calculation
shows that antenna 1 is more
wideband at the lower operating
frequency but antenna 2 is more
wideband at the upper
frequencies (although the antenna
is smaller).
www.optenni.com www.optenni.com
Bandwidth potential and parameter sweeps Height of antenna 2 varied
Optenni Ltd, May 22, 2013
Difficult to see the effect of the
height. Seems to lower the upper
resonance frequency?
The maximum bandwidth of the
upper resonance stays at the
same frequency, lower resonance
becomes more wideband.
Raw impedance data Bandwidth potential
www.optenni.com www.optenni.com
Summary of bandwidth potential
• Using raw impedance data it is difficult to compare
differently matched antennas and it is difficult to see
how large bandwidth could be obtained with
impedance tuning.
• Bandwidth potential calculations show the obtainable
bandwidth at all frequencies, making comparison of
different antennas easy. Bandwidth potential can also
be used with parameter sweeps.
• Bandwidth potential saves antenna design time and
reduces the number of prototypes.
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
CALCULATION OF WORST-
CASE ISOLATION
Main Features of Optenni Lab
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Calculation of electromagnetic isolation • Electromagnetic isolation is the worst case isolation at each
frequency when two ports are simultaneously conjugate
matched at that frequency.
• It can be used to compare different antenna systems (e.g. in
diversity applications) in terms of their isolation
characteristics without matching the ports manually.
Optenni Ltd, May 22, 2013
S21
Electromagnetic isolation
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Usage of electromagnetic isolation
• Electromagnetic isolation can be used to select best
position for diversity antennas.
• Moving the diversity antenna will change the
matching of diversity and main antennas and thus
also the antenna isolation. Observed isolation might
be large only due to poor matching.
• Electromagnetic isolation shows how the isolation
changes in the case that both antennas would be
matched and can thus be used to reliably compare
the isolation in different positions.
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
OTHER FEATURES AND
SUMMARY
Optenni Lab
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Additional features
• Generation of matching circuits that obtain conjugate
matching to the termination impedance or maximize
the bandwidth around a starting frequency
• Calculation of radiation efficiency from impedance
and total efficiency data with different frequency
grids
• Capability to read and write project files containing
the previously computed results
• Comparison of different results on the same plot
• On-line manual
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Link between CST and Optenni Lab
• A two-way link between
Optenni Lab and CST
STUDIO SUITE™ has been
developed
• Optenni Lab can be launched
from within CST
• Matching circuits generated
in Optenni Lab can be
transferred to CST DESIGN
STUDIO™ for further
analysis
Optenni Ltd, May 22, 2013
www.optenni.com www.optenni.com
Advantages of using Optenni Lab • Fast matching circuit generation
• Rapid estimation of obtainable bandwidth
• Easy comparison and evaluation of antenna
prototypes
• Optimal total antenna performance obtained
• Very intuitive graphical user interface
• Can be easily operated also by nonspecialists
• Developed further based on user feedback
• Optenni Lab increases the productivity of antenna
designers and reduces the design times of antennas
Optenni Ltd, May 22, 2013