List of relevant main papers (MP):
- A. Sayeed and N. Behdad, Continuous
Aperture Phased MIMO: Basic Theory and Applications,
Allerton 2010. Extended
- A. Sayeed and N. Behdad, A Novel Hybrid
Analog-Digital Architecture for Optimum AgileWireless
Communication Using Discrete Lens Arrays, NSF EAGER
- A. Babakhani, D. Rutledge, A. Hajimiri,
Near-Field Direct Antenna Modulation, IEEE Microwave
Magazine, Feb 2009.
- P. Daly and J. Bernhard, Directional
Modulation Technique for Phased Arrays, IEEE Trans.
Antenna and Propagation, Sep 2009. Earlier
- P. Daly, E. Daly and J. Bernhard, Demonstration
of Directional Modulation for Phased Arrays, IEEE
Trans. Antennas and Propagation, May 2010.
- IMAT white paper from
- D. Lawrence, Low
Probability of Intercept Antenna Array Beamforming,
IEEE Antennas and Propagation, Sep 2010.
- H. Kogelnik and T. Li, Laser
Beams and Resonators, Proceedings of the IEEE, October
1966. (Also in some cases Applied Optics, October 1966).
- H. Friis, A Note on A
Simple Transmission Formula, Proc. IRE, May 1946.
- H. Friis, An
Introduction to Radio and Radio Antennas, IEEE
Spectrum, April 1971.
Other papers (OP):
- S. A. Schelkunoff, A
Mathematical Theory of Linear Arrays, Bell Sys Tech
- J. B. Keller, Geometrical
Theory of Diffraction, J. Optical Society of America,
- M. Kales and R. Brown, Design
for Two-Dimensional Symmetric Bootlace Lenses, IEEE
Antennas and Propagation, July 1965.
- W. Kock,
Metallic Delay Lenses, Bell Sys Tech Journal,
- W. Kock, Path-length
Microwave Lenses, Proc. IRE, August 1949.
- D. McGrath, Planar
Three-Dimensional Constrained Lenses, IEEE
Transactions on Antennas and Propagation, Jan 1986.
- R. Harrington and J. Mautz, Theory of
Characteristic Modes for Conducting Bodies, IEEE
Trans. Antennas and Prop., Sep 1971.
- M. Cabedo-Fabres, E. Antonino-Daviu, A. Valero-Nogueira
and M. Ferrando Bataller, The Theory
of Characteristic Modes Revisited: A Contribution to the
Design of Antennas for Modern Applications, IEEE
Antennas and Prop. Magazine, Oct 2007.
- E. Antonino-Daviu, M. Cabedo-Fabres, M. Gallo, M.
Ferrando-Bataller, and M. Bozzetti, Design
of a Multimode MIMO Antenna Using Characteristic Modes,
European Conference on Antennas and Propagation, EuCAP
- W. Rotman and R. F. Turner, Wide-angle microwave
lens for line source applications, IEEE Trans.
Antennas and Propagation, Nov. 1963, pp 623-632.
- J. Dong, A.I. Zahloul, and R. Rotman, Phase-error
performance of multi-focal and non-focal two-dimensional
Rotman lens designs, Microwaves, Antennas &
Propagation, IET, Dec 2012, Vol. 4 Issue 12
Related presentations, white papers and articles (RP):
- R. Daniels, J. Murdoch, T. Rappaport, R. Heath, 60 GHz
Wireless: Upclose and Personal, IEEE Microwave
Magazine, Dec 2010.
- T. Rappaport, M. Corsi, R. Heath, Broadband
Wireless Personal Area Networks - 60 GHz and Beyond,
IEEE Globecomm, Business Forum, Dec 2010.
white paper - Defining the Future of Multi-gigabit
wireless communications, Wireless Gigabit Alliance,
- J. Wells, Faster
than Fiber - the future of multi-Gb/s wireless
communication, IEEE Microwave Magazine, May 2009.
- A. Niknejad, Siliconization
at 60GHz, IEEE Microwave Magazine, Feb 2010.
- Vijay Venkateswaran and Alle-Jan van der Veen,
Analog beamforming in MIMO communications with phase shift
networks and online channel estimation, IEEE Trans.
Signal Processing, August 2010.
- T. Marzetta, Noncooperative
Cellular Wireless with Unlimited Numbers of Base Station
Antennas, IEEE Transactions on Wireless
Communications, Nov 2011.
beamforming in MIMO-OFDM for WPAN, IEEE Wireless comm,
Communication Modes (Optics)
- D.A.B. Miller, Communicating
limits on coupling strengths,Applied Optics, April
- A. Burvall, P. Martinsson, A. Friberg,
Communication modes in large aperture approximation,
optics letter, march 2007.
- P. Martinsson, H. Lajunen, A. Friberg, Communication
modes with partially coherent fields, JOSA, October
- Shapiro et. al. Ultimate
Capacity of Optilcal links.
Ray Tracing Papers
1. R. Brem and T. F. Eibert, Multi-Radiation
Center Transmitter Models for Ray Tracing, IEEE
Transactions on Antennas and Propagation, Vol. 60, no.7,
July 2012 pp. 3382-3388.
- 10-11-2010. Akbar presented his allerton talk on capmimo.
- 10-18-2010. Nader presented a talk on biomimetic array
- 10-25-2010. discussion of DM and NF-DAM papers in relation
to cap-mimo. Papers: MP1, MP3, MP4
- DM versus NF-DAM. both DM and NF-DAM are aimed at using
the spatial dimension to create detectable modulation
(QAM) in a desired direction while obfuscating the signal
constellation in an undesired direction. Both can be used
for arrays of antennas and rely on the differences in the
signal path lengths from the array to a desired
single-antenna receiver versus an undesired receiver at a
differnet direction. A key difference is that NF-DAM
uses switches within an single array element (of size
lambda/2) to change its far-field radiation patterns and
signal constellation as a function of location, whereas DM
uses different phase patterns across the array to achieve
the same objective. In this regard, due to the limitation
of a single antenna element in producing changes in path
lenghts/phases, DM seems more effective. Furthermore,
NF-DAM is aimed at shorter links whereas DM can be used
for longer links. Both are for LoS comm.
- connection with CAP-MIMO. Certainly the idea of DM can
be realized in CAP-MIMO in the beamspace. There may even
be opportunities for doing a better job at secure
communication by working directly in beamspace. Further,
we can extend the idea to multipath propagation, wideband
transmission (via frequency-selective surfaces) and full
MIMO operation (higher rates) by sending multiple data
streams towards the receiver.
- Also discussed the spatial mode solution for a signal
dipole as a function of feed location, presented by Nader.
Its has a nice geometrical interpretation. Interesting
aspects would be to extend the patterhs for larger length
antennas and to explore further degrees of freedom in
exciting different spatial modes.
- Aside: Packers beat Vikings in a nail-biting (28-24)
finish the night before. Favre almost worked his magic
with a last minute touchdown to give Minnesota the lead,
but the touchdown was ruled in incomplete reception!
- 11-1-2010. Discussed the CAP-MIMO WARF project. Three main
tasks: 1) Detailed DLA phase profile design and full-wave
simulation, 2) DLA fabrication and the system building
(supports for focal feed elements at TX and RX), 3)
Phase-coherent system measurements and data processing. Need
to finish the tasks by June 2011. So, tentative deadlines
for the three tasks. Task 1: Jan-Feb 2011. Task 2: Feb-March
2011. Task 3: June 2011. Some intermediate steps to keep in
- Purchasing computers and software for full-wave
- Stitching together the full-wave simulation of the lens
(which gives the field amplitude/phase profile as a
function of feed excitation) with Ray tracing modeling of
the propagation from TX to RX.
- Preparing the students involved with both basic theory
and modeling and full wave simulation and measurement
process. Mudar will give a presentation on full-wave
simulation and measurements next week.
- 11-8-2010. Akbar and Nader were out. (Akbar at
Cowboys-Packers game; 45-7 blowout! Nader at a conference).
Mudar discussed FSS-based lens design and associated
software for simulation.
- 11-15-2010. 1) discussed the lens phase profile design.
Akbar will lead the effort with help from John and Pushkar.
Will share the matlab code. As a starting point we can
formulate lens design as a n-dimensional optimization
problem with n variables and n constraints (more details
later). 2) Nader provided information on the full-wave
simulation software choices. Will need both software and a
dedicated machine. need to make that decision soon. will
only simulate the lens design and then stitch with the
overall system via ray tracing (matlab-based approach). will
revisit the basic theory (periodic structures) behind
FSS-design approach (Nader and Mudar) for a better
understanding of the design and the resulting
errors/iterations needed. 3) Akbar led a discussion on the
directional modulation business. seems that having parasitic
feed elements on the focal surface may be the best union of
caltech and uiuc approaches. key conjecture: phase/amplitude
shifting with parasitic feed elements should not impact the
I/Q constellation much in the desired direction but
significant differences in other (unwated directions). The
other (parasitic) feeds for unwanted directions could be
used for additional noise in unwanted directions. would like
to include this aspect in APS paper (January deadline). Gi
Hong and Pushkar will work with Akbar on this.
- 11-22-2010. Akbar discussed the connection between
CAP-MIMO theory and the notion of spatial modes in Laser
Beams and Resonators (MP 8 paper - thanks to Prof. Ron
Vernon). This is also connected to the theory of
characteristic modes that John had discovered (OP 7).
- 11-29-2010. Discussed the CAP-MIMO WARF project
timeline through June 2011. On track for detailed prototype
design by the end of semester (Milestone M1a). Allocated a
rough timeline for the other two milestones: M1b (prototype
hardware development for 1D arrays, including full-wave
simulation of the DLA design - mid March), and M1c: system
measurements and data processing (June 2011). Tentative
assignment of responsibilities for graduate students:
FSS-based DLA design and fullwave simulations -John Brady.
Prototype hardware development, including the nature of feed
antennas and focal arc assembly for the feeds - Pushkar.
System measurents: all (John, Pushkar, Gi Hong). Data
processing (Gi Hong). Mudar along with Akbar and Nader will
be involved in all aspects. Need to finalize the purchase of
software by end of semester. Further purchasing of hardware
will be in Spring.
- 12-6-2010. Agenda: discussion of DLA phase profile design,
including the choice of feed antennas, and the nature of
- 1-24-2011. Present: Akbar, John, Gi Hong, Puskhkar, and
Mudar. Update on DLA beampattern measurement results from
Mudar. Some issues regarding theoretical versus measurement
results. John will replicate the theoretical results and
compare with Mudar's.
- 1-31-2011. Present: All. Discussed three issues: 1) New
GEMS software: whether its needed and when to purchase it.
Consensus was to contact them for a trial offer for
simulating a full lens and estimate its phase profile via
the software and compare it to the designed phase profile.
This would give us an idea of whether the software can
handle the job (and subsequent ones) to make it a worthwhile
purchase. will start a discussion with them and perhaps have
the full-wave simulation of lens after Mudar-Nader have
published their first paper on the design. John (and
Pushkar) will lead the DLA full-wave simulation with
guidance from Mudar and Nader. 2) Finalization of the DLA
profile design and TX/RX DLA fabrication. John will lead
this effort. Generate theoretical beampatterns to compare
with Mudar's measurements and theoretical plots. Perhaps do
additional measurement to isolate the source of possible
errors (measurement vs inherent DLA design) before
finalizing on the phase profile design prior to ordering
fabrication. Timeline: to finalize the DLA phase profile
design by end of Feb. 3) Discussed the system measurement
set up and design for the prototype CAP-MIMO link. Starting
point is the current set up Mudar has for the 27cm lens.
Possible ideas: Increase the size of the insulator
surrounding the lens aperture. Perhaps put an isolation box
around the DLA to avoid leakage. Pushkar will lead this
effort and we will go to lab to see Mudar's set in an
upcoming meeting. 4) Gi Hong will lead the system
measurement and data processing part. Create a detailed
step-by-step protocol for system mesurements and processing.
- 2-7-2011. No meeting in celebration of Packers' 31-25
superbowl victory over the Steelers. Go Packers! CAP-MIMO
- 2-14-2011. Got an update from Brady and Gi Hong on the
lens design and comparison with Mudar's measurement
data. (Brady: ppt file here). went over the different
tasks in the WARF project and deadlines.
- 2-21-2011. No meeting.
- 2-28-2001. updates and discussion of upcoming WARF
interview on Mar 2.
- 3-7-2011. No meeting. Akbar met with Gi Hong and John for
update on lens design.
- 3-14-2011. No meeting. Spring break.
- 3-21-2011. Got update from Gi Hong on the lens design
capacity assessment. Brady making progress on physical
design specification to send out for fabrication. Some
issues: how much errors do we expect in the design process?
(both design software as well as manufacturing tolerance).
Tentative choice of feeds: dipoles antennas. Key issue here
is to have an adequate SNR. Pushkar will do some
calculations build a second dipole antenna if necessary to
do some measurements.
- 3-28-2011. no meeting.
- 4-4-2011. John gave update on lens design; to do:
accounting for bonding layer effects, and angle of incidence
effects. Gi Hong gave an update: showed capacity results for
random phase errors (upto 10 deg) in the optimum phase
profile. While there was significant (about 20%) power loss
compared to the optimum, an interesting result was that
there were still 2 dominant eigenvalues (as in the no-error
case), thereby making it feasible to demonstrate the capmimo
gains over dish. Pushkar gave an update on feed design.
- 4-11-2011. Gi Hong updated that he got better results
(less power loss) when he incorporated the smaller cell-size
compared to lambda/2; needs to incorporate amplitude change
using John's results. John updated that bonding layer stuff
is taking more time. should have more results next week. but
he has a coarse amplitude/phase profile that he could give
to Gi Hong. currently focusing on 5th order filter design.
Pushkar updated that he simulated the dipole feeds and found
asymmetric beam patterns - needs to carefully read the
papers and revisit it. Nader noted that we need to finalize
on the cable orders soon since they take upto 6 weeks.
Updated deadlines: lens design (John) asap, no later than
end of April. Pushkar: end of april for feed design. Full
measurement apparatus by end of May (design/dimensions to be
finalized by Mid May). Akbar updated that he had talked to
Booske about space.
- 4-18-2011. John updated on lens design - some problems
with frequency response at the edges - will talk with Mudar
- deadline May 15. Did a quick calculations due to angle of
incidence at the edge of the lens- upto 10-15 degrees phase
errors. Gi Hong updated on channel calculations with phase
errors and smaller cell-size on phase profile - results look
promising - even with 6 deg phase errors two dominant
eigenvalues are present. Pushkar updated on feed design - a
balanced dipole. The simulations indicated a tilt in teh
beampatterns - fairly symmetric though. Nader suggested
simulating hte components - the dipole and hte driving
circuit separately as sanity checks to see if the circuit is
behaving as expected. Akbar suggested going back to the
beampattern analysis of a dipole to see what causes a tilt.
That could be useful because tilting precisely corresponds
to different beam directions, so this may be a clue to
generating different beam directions. perhaps something to
do with the phase difference between the two feeds to the
- 4-25-11. pushkar created two dipoles to act as feeds and
receivers on the focal surfaces. did S21 measurements on the
two at a distance of about 10feet (link length). Got a -60dB
measurement for S21 between the two dipoles. The noise floor
of the VNA is -90dB so with the expected gain for the lenses
we should be okay. Finalized on hte order for two 20' feet
cables with a 12dB loss. Each about $1000.
- 5-2-11 (Bin Laden killed!). Everything on track.
discussed lens design sanity check with John with regard to
transder function. Puskkar investigated the beam patterns of
dipole - seems like cannot produce too much of a beam shift
even with larger apertures due to the feed structure (this
to be revisited).
- 5-17-11. met for a short meeting. Everthinng on track. Gi
Hong will investigate optimization of feed locations (later
results showed that the original positions are pretty good).
- 5-24-11. John got a quote on the lens manufacture and also
on materials. makes sense. discussed metamaterials, power
and information with Nader. The combined gain of the feed
and the lens is a tricky calculations - will have to
- 5-31-11. Lens material arrived. John accounting for angle
of incidence in design.
- 6-7-11. Pushkar ordered the absorbers. costly!
- 6-21-11. gi hong gave a presentation on off broadside
channels. interesting results.
- 6-28-11. John finished lens design! Should receive the
lenses next week. Pushkar made significant progress on
prototype design and building. Should be done by the end of
the week. Akbar and Nader will be at APS symp. in Spokane
- 7-5-11. No meeting. Akbar and Nader at APS. Beautiful
country north of Spokane.
- 7-12-11. Akbar, John and Gi Hong met. Reviewed the
prototype construction. Only one lens arrived. Will test the
first lens and then order the fab of second lens by next
Monday. The lens looks beautiful.
- 7-19-11. Meeting cancelled to escape the heat and the lack
of A/C in EH.
- 7-26-11. Gi Hong, John, Pushkar, and Akbar met to discuss
prototype status and initial measurements. The prototype is
nearly finished. The second lens is here and final steps on
finishing the building. First set of measurements, without
metal sheet or absorbers, expected by the end of the week or
early next week. The measurement results would demonstrate
the final milestone of phase 1 of WARF project.
- 8-2-11. The first set of measurements without metal sheet
showed asymmetry but still demonstrated two eigenmodes. So,
the team put metal sheets and redid the measurements for a
1D 2x2 system. The results are close to what we expect
theoretically and demonsrate the cap-mimo technology (Phase
1 of WARF project).
- 8-9-11. Additional measurements were done on a 4x4 (2D)
system and the results are again comparable to theory and
demonstrate the existence of 4 dominant 2D modes.
Theoretically, we expect upto 9 modes. Pushkar is optimizing
feed design (flat dipole, patch, or waveguide). The next
steps for John and Gi Hong are P2MP operation (and lens
design). Also mutual coupling. The linear aspects of mutual
coupling (at the feeds) can be readily incorporated in the
CAP-MIMO theory. Akbar did some preliminary calculations and
saw that mutual coupling can actually provide further
increase in performance (contrary to conventional wisdom).
Gi Hong will likely take the lead on the mutual coupling
- 8-17-11. Met with Pushkar and Nader to discuss feed
designs. Two commercially viable ones: square and circular
waveguide feeds (both give about 9db gain). Pushkar is
checking on physical specs and cost. In terms of homemade
design, between fat dipole and patch, the latter looks more
promising. Fat dipole issues: sensitivity to feed location
and the construction of ground plane. Pushkar will further
investigate the patch design. Some issues: size of patch,
size of ground plane (no larger that .9lambdax.9lamda), gap
between patch and ground plane, and the dielectric constant
of the gap
- 8-18-11. ****
Met with Brady and Gi Hong. Discussed the plan for Gi Hong:
performance assessment of CAP-MIMO for three TX/RX
structures with or without channel estimation errors. The
three structures: 1) Benchmark system corresponding to n
dimensional SVD of H with p modes. 2) Beamspace channel with
ideal DFT (H_o) and with lens (H_L). Ideal DFT (U_o), Lens:
U_L. based on p_eff dimensional SVD. Relationship between
p_eff and p to be determined; e.g based on capturing the
same fraction (.98?) of total channel power. 3)
Beamspace/Lens channel with independent transmisson on p_eff
feed locations (beams) and MMSE receivers. Do capacity
comparison (spectral efficiency vs energy efficiency
(Eb/No)) for all three systems and also P_e analysis for
uncoded (e.g., QPSK) transmission. Then Repeat above
analysis with channel estimation errors. Channel estimation
errors could be due to errors in channel estimation. But
also consider other forms of errors (e.g., orientation of
antennas). Brady will create an outline of the lens paper.
Also gave him pointers for a few things: 1) Does U_L have a
kronecker structure? If so, may reduce computation. 2) Next
set of measurements. 3) Viewing the different mode
propagation to TX aperture, RX aperture, RX focal surface.
This would also allow us to estimation fraction of power
that couples to receiver.
- 8-23-11. John updated on computational framework for DLA
and system modeling. Showed contour plots for different
beams at the RX aperture. Pushkar updated on waveguide
- 8-30-11. Pushkar updated on costs for circular,
rectangular (standard), and square (custom) waveguides.
Akbar discussed plans for Phase II to be presented at the
next WARF meeting on Sep 21.
- 9-21-11. Presented Phase I results to the WARF catalyst
group, including plan for Phase II and a tour of the
prototype lab. Very useful and informative meeting.
- 10-11-11. Updates from Brady on new lens measurements. Gi
Hong updated on MMSE and SVD transceivers and impact of
channel estimation errors. The MMSE results look very
promising. The error analysis needs to be updated.
- 10-18-11. No meeting. Students busy with midterms.
- 10-25-11. Gi Hong updated results on MMSE and SVD
transceivers. 2D-MMSE looks very promising. Still some
problem with SVD. John updated on teh cost of various
waveguides and transitions for hte next prototype.
- 10-31-11. Phase II proposal finally finished and submitted
- 11-1-11. Discussed initial plans for Phase II and
got updated from Gi Hong and Brady. Gi Hong's results
looking very promisng. fixed the problem with SVD-based
- 11-8-11. Discussed the first telecon with Samsung
(Akbar and Brady could make it).
- 11-15-11. Discussed Phase II plans and also Samsung
- 11-23-11. Telecon with Samsung: Akbar, Nader, Jerry Pi,
Farooq Khan, and Chirala.
- 11-29-11. Discussed the NSF proposal.
- 12-6-11. Further discussion of the planning for the NSF
- 2-6-12. NSF proposal submitted.
- 2-20-12. Charlie Zhang (Samsung) visited and gave an
- 2-21-12. Discussed the various forms of technology for
phased arrays. And power capabilities. Also, ongoing
discussions with Samsung. Also discussed the recent visit by
- 2-28-12. Discussed power calculations for the prototype to
account for any losses and for reconciling theory with
measurements. In particular, the importance of power not
coupled between teh TX and RX and the use of ratios of
coupled to total power. Also, first principle continuous
- 3-16-12. Brady discussed his paper plan, now that he is
done with the qualifiers. In particular doing some
modifications for the prototype in view of upcoming
- 3-27-12. Discussed Gi Hong's results on MF receiver
performance. Brady's paper preparation and measurement
schedule. Basically, detailed P2P measurements (NB), and BW
measurements only for broadside. For P2MP, do broadside
measruements for 0-60 deg, with 4-5deg increments. Then do
spot measurments 2x2 measurements and BW measurements for
30, 60. Add as necessary. Akbar discussed Friis formula and
some modifications that may be needed in our context.