University of Manchester

School of Computer Science

Advanced Processor Technology (APT) Research Group

Dr. Barry M.G.Cheetham B.Sc., PhD., C.Eng., MIET, MIEEE

barry@man.ac.uk

       Senior Lecturer in Signal Processing and Telecommunications for Mobile Systems Architecture (MSA)

 

Appointed to current post in February 1998.
From October 1979 until January 1998,
Barry was a lecturer in the Department of Electrical Engineering & Electronics, Liverpool University, UK.

 

 

 

 

 

Current research interests:

  • Voice processing for high quality ‘voice-over-wireless LAN’ (VoWLAN) over converged enterprise networks
  • Coding of speech for mobile communications
  • Computer network technology for distance learning
  • Speech technology (speech coding, analysis and synthesis)
  • Implementation of speech processing algorithms on an asynchronous DSP core
  • Digital signal processing applied to the acoustical analysis of musical performance
  • Digital signal processing applied to the analysis and monitoring of biomedical signals (pulmonary sounds analysis)

I have held about 25 research grants, including 5 EPSRC and 2 EU grants including a European "concerted action”.

I supervised 29 successful Ph.D. projects, and had long term involvement with a number of communications companies including BT.

I have published 1 book, 2 book chapters, 27 journal papers, 40 international conference papers, 20 colloquium papers, 9 abstracts, 3 articles and have been responsible for four patents held by BT.

I have extensive teaching and administrational experience including that of being instigator and Director of an M.Sc.(Eng.) Course in Telecommunications and Micro-electronic Systems. I also set up and ran a short course for industry on "Digital Signal Processing".

I have been a member and chairman of the IEE E10 "Circuits & Systems" professional group committee, a member of IEE Divisional Board, Premiums Committees, and other professional groups.

I have been external examiner for 21 Ph.D. and two M.Phil projects, and have served on the organising committee for major international conferences: including ECCTD’89 , IEEE ISCAS’94 and ILSA’97 and ICLSP’98.

Current research projects:

  • "Implementation of DSP speech coding algorithms on an asynchronous DSP core", Ph. D. student: X. NI
  • "Peer to peer networks for interactive real time communication in distance learning" A. Tramantzas
  • "Measuring real-time QoS parameters for network simulation applied to distance learning",
  • High quality (DECT) voice over WLAN: WINDECT  (www.WINDECT.ethz.ch )
  • Other research projects & vacancies: http://www.cs.man.ac.uk/~barry/mydocs/Research

Recently completed Research Projects:

  • 2001 "Sinusoidal transform coding of speech for mobile communications" , Dr. M.S. HO
  • 2002 "The discrete all-pole model applied to speech coding and synthesis" , Dr. D. MOLYNEUX
  • 2003 "Variable bit-rate speech coding for mobile telephony", Ph. D Student: N. LI
  • 2004 "Internet technology for distance learning", Ph.D. Student: L.R. HE
  • 2004 " Modulation techniques for future mobile radio", M.Phil student: A. ESHHUBI
  • 2005 " Time-frequency analysis applied to biomedical signals", Ph.D.Student: Y.H. HIEW
  • 2006 "Time-frequency analysis of musical performance", Ph.D. student: A. EARIS
  • 2006 ‘Energy aware compilations for an asynchronous DSP core’ student X. NI

Recent research contracts:

1998  "Techniques for the short term spectral analysis of speech as required for low bit rate coding" British Telecom (ML770603/MH183 GG272NEY)

1993-96 "Efficient Techniques for speech synthesis using an articulatory model" (GR/H79013 /RGEEFD)

1995-98 "Variable bit-rate speech coding for mobile radio networks" (DTI/EPSRC LINK project with BT Laboratories & Ensigma Ltd)

1994-97 European research grant under "Biomed III": Concerted Action: "CORSA" Helsinki University, Liverpool University (with Fazakerley Hospital), Leiden University (Netherlands), Universite de Paris Sud (France) and Ospidale

2000-01 (with David Tait) ESPICO: Implementation of speech processing algorithms on DSP cores.

2000-03 Wythenshawe Hospital: ‘DSP applied to the analysis and monitoring of chronic cough’

1996-2000  Fazakerley Hospital:  ‘DSP applied to pulmonary sounds’

2003-2006 WINDECT : EU ‘Framework 6’ Specific targetted research & Innovation Project in collaboration with Ascom (Switzerland), Winfinity (Berlin), IHP (Frankfurt-Oder), ETH (Zurich), Josef Stefan Institute (Ljubjana  Slovenia) & Manchester University (UK)
WINDECT aims to merge wireless networks by integrating professional quality telephony into WLANs to achieve high quality voice over WLAN. This will lead to an innovative application in the field of wireless and mobile communications in converged enterprise networks. ( www.windect.ethz.ch )

 

Barry’s Teaching and Administration

Lecture courses:

CS3291: Year 3: ‘Digital Signal Processing’: http://www.cs.man.ac.uk/~barry/mydocs/CS3291

CS3282: Year 3: ‘Digital Communications’: http://www.cs.man.ac.uk/~barry/mydocs/CS3282

COMP30291 Year 3 ‘Digital media processing’ http://www.cs.man.ac.uk/~barry/mydocs/COMP30291

 

Final Year & MSc Computer Science Projects (2009-10):   http://www.cs.man.ac.uk/~barry/mydocs/Projects

 

COMP18112: Year 1: ‘Foundations of Distributed Computing’: http://www.cs.man.ac.uk/~barry/mydocs/MyCOMP18112         

                                                                                                 

COMP28512: Year 2: ‘Mobile Systems’: http://www.cs.man.ac.uk/~barry/mydocs/MyCOMP28512 

 

COMP61232: M.Sc.: ‘Mobile Communications’ given by Dr. Barry Cheetham and Dr. Nick Filer:

                                                                                    http://www.cs.man.ac.uk/~barry/mydocs/MyCOMP61232   

 

COMP80131: PhD Scientific Methods 1: ‘Scientific Evaluation, Experimental Design & Statistical Methods’ (Barry & Goran)

                                                                                    http://www.cs.man.ac.uk/~barry/mydocs/MyCOMP80131

                                                                 

Administration:

PGR-Postgraduate Research Student Admissions & CS-CDT Acting Manager

Organizer:  Final Year Projects.

Chairman: Siemens medal award committee for Computer Science.

Member: Computer Science ‘Mathematics’ committee

Other interests:

Manchester University Chorus:  http://orgs.man.ac.uk/chorus

Father   http://www.cs.man.ac.uk/~barry/mydocs/Father

 

Some recent publications (compiled Mar’06)

 

(1) A Nenadic, N Zhang, BMG Cheetham, CA Goble, 'RSA based certified delivery of E-goods using verifiable and recoverable signature encryption',

       Journal of Universal Computer Science, Springer-Verlag, , ISSN 094869x, pp 175-192, vol 11(1), 1 Jan 2005

 

 (2) He LR & Cheetham BMG, "Real time multi-media facilities for distance learning over a network link", Proc. IEE Seventeenth UK Teletraffic Symposium,  Dublin, 16-18 May 2001, pp. 3/1-3/5,

 

(3) MS Ho, DY Molyneux, BMG Cheetham, "A hybrid sub-band sinusoidal coding scheme", Proc Eurospeech 2001, Aalborg, Denmark, vol 3,

      pp 1985-1988,  Sept 2001. (ISBN 87-90834-09-7 & ISBN 87-90834-10-0)

 

(4) A. Earis, BMG Cheetham,  "Analysing expression in musical performance", Institute of Acoustics (IOA) ‘Acoustics Bulletin’ 29 (4), 2004, pp29-33,

       ISSN 0308-437X, www.ioa.org.uk/bulletin.asp

 

(5) A Earis & BMG Cheetham " Extraction of expressive performance parameters from recordings of piano music",

      Proc Institute of Acoustics Spring Conference 2004, University of Southampton, UK, Mar 2004, IOA publication ref 1183, www.ioa.org.uk

 

 (6) A. Earis, BMG Cheetham & DJ Tait, "Extraction of performance parameters from acoustic recordings of piano music", Proc Institute of Acoustics

       Spring Conference, 2002, ISBN 1901656454, ISSN 03098117, volume 24 (2), Salford, UK, IOA publication ref 1169,  www.ioa.org.uk

 

 (7) A. Earis BMG Cheetham & DJ Tait "Quantative analysis of expressive timing and dynamics of musical performance", Investigating Music performance:

       Fourth International meeting of Society for Education, Music & Psychology Research (SEMPRE), Royal College of Music, London, April 2002

 

(8) Hiew Y. H., Smith J.A., Earis J.E., Cheetham B.M.G., Woodcock A.A. "DSP Algorithms for Cough identification and counting",

     Proc.IEEE  International Conference of Acoustic, Speech & Signal Processing 2002 (ICASSP), Orlando, USA, volume IV,
    pp.3888-3891 (ISBN 0-7803-7403-7)

 

(9)  N. Li & BMG Cheetham, 'A variable frame-rate scheme for sinusoidal transform coding' Proc IEEE ICASSP2002, 1 May 2002, 4163-4167, vol. 4,
       (ISBN 0-7803-7403-7)

 

(10) BMG Cheetham, "Real time multimedia communications for distance learning networks" Invited paper, Proc International Conference on e-Education,

       (ICEE2001),  Malaysia Oct 2001

 

(11) LR He, I Rogers, LS He, BMG Cheetham, W Suntiamorntut  'A New Transport Control Protocol Applied to Real-Time Multimedia  Distance Learning',Proc ICICS Dec 2005, Bangkok, Thailand, http://www.icics.org/2005

 

(12) Kuhn M.,  Ettefagh A., Lunn, A., Cheetham B., Spegel M, "Professional quality voice over WLAN",

        Proc 60th IEEE Vehicular Technology Conference, (VTC2004-Fall), Los Angeles, California, 26-29 September, 2004
       .(ISBN 0-7803-8521-7, ISSN 1090-3038)

 

(13) A. Lunn, Marc Kuhn, Michael Kuhn, A Ettefagh, BMG Cheetham, M Spegel,  "High quality telephony over WLAN"

        ECWT 2004, Amsterdam, 2004

 

(14) BMG. Cheetham, T Becker, FM Krause, K Tittelbach-Helmrich, M Methfessel, A Lunn, " DECT over WLAN with seamless hand-over and load
    balancing",  First International Symposium on Broadband Communications, (ISBC'04), 12-15 December, 2004, Harrogate (Leeds), UK

 

 (15) A Lunn, M Kuhn,  BMG Cheetham, "Providing professional quality voice over WLAN using DECT", ‘WIFI VOICE’ Conference 2005:

         Achieving VoIP over WLAN,  Paris,  10-13 May 2005, www.upperside.fr/wifi05/wifivoice2005program.htm

 

(16)  Ettafagh A., Kuhn M., Cheetham B.M.G., Wittneben A.,

      “ Comparison of distributed and co-located antenna diversity schemes for the coverage improvement of VoWLAN systems”,

       Proc 16th IEEE Int Symposium on Personal & Indoor Radio Communications, PIMRC 2005, vol 1, 11-14 Sept 2005, pp77-81

 

 (17) Tramanzas A., Cheetham BMG, van Harmelen M.,& . Walker A.C.,  ‘Peer-to-peer networks based on hierarchies of trust’, Proc 5th IEEE Conference on Peer-to-peer Computing 2005 (P2P 2005), pp160-161, 0-7695-5/05 $20.00, http://doi.ieeecomputersociety.org/10.1109/P2P.2005.26 , 2005

 

(18) BMG Cheetham , A Ettafagh, M Spegel, KM Nasr, E Ravnikar “ Voice over WLAN for Converged Enterprise Networks”,
       15th IST Mobile & Wireless Communications Summit 2006,  Mykonos accepted, (paper id. MS2006-880), 4-8 June, 2006

 

(19) BMG Cheetham & K. Nasr “Error concealment for Voice over WLAN in Converged Enterprise Networks”,
       15th IST Mobile & Wireless Communications Summit 2006,  Mykonos, accepted,(paper id. MS2006-967), 4-8 June 2006

 

(20) Hiew Y. H., Smith J.A., Tait D.J., Cheetham B.M.G., Earis J.E., Woodcock A.A."Long-term Objective Cough Recognition And Quantification",

        IEE Medical Application of Signal Processing, London,  Ref. no. 2002/110, pp. 20/1-4,  October 2002,

 

(21) Lizzie's PREP conf. paper and Paris paper

 

(22) BMG Cheetham & A.I Eshhubi, "Voice over an OFDM based wireless LAN", Proc IEE Colloquium on DSP Enabled Radio, 22-23 September 2003,

        ILSI, Scotland, UK, pp6/1-4

 

 (23) X. Ni, W Suntiamorntut, BMG Cheetham, LEM Brackenbury & DJ Tait,

        "Design of an asynchronous function unit and software development tools for a low power DSP" 

          Proc. IEE Colloquium on DSP enabled radio, 22-23 September 2003, ILSI, Scotland, UK, pp 8/1-4

 

(24) BMG Cheetham & A.I Eshhubi, "Voice over IEEE 802.11 Wireless LAN", COST273 Technical Document TD(03)146, Brussels, Belgium,
      May22-23, presented at the COST273 meeting Paris May 22-23, 2003.

 

(25) BMG Cheetham & A.I Eshhubi, "Voice over OFDM based Wireless LAN", COST273 Technical Document TD(03) 068, Brussels, Belgium, Jan 2003, presented at the COST273 meeting in Barcelona, Jan 16-17, 2003

.

(26 )M Spegel & BMG Cheetham, ‘WINDECT: DECT over WLAN’, Presented at EU IST-Framework 6 (Communication Technologies)

       ‘Broadband Air Interface (BAI) Cluster’ meeting in Brussels, 23 Sept 2005. www.cordis.lu/ist/ct/neweve/concertation/6_06concertagenda.htm

 

 (27) BMG Cheetham ‘VoWLAN in converged enterprise networks (WINDECT)’,  Workshop on ‘Voice over WLAN’, IBBT Broadband Europe conference

         (BBEurope) held in Palais des Congres de Bordeaux, France, 12-14 Dec 2005, www.bbeurope.org  contribution WE-WS03.

 

Some less recent publications

1. Wong, W. T. K., Mack, R. M., Cheetham, B. M. G. & Sun, X. Q., "Low rate speech coding for telecommunications", BT Technology Journal, Vol. 14, No.1, January 1996, pp28-44.

2. Spence D.P.S., Graham D.R., Jamieson G., Cheetham B.M.G., Calverly, P.M.A. & Earis J.E. , "The relationship between wheezing and lung mechanics during methacholine induced broncho-constriction in asthmatic subjects", American Journal of Respiratory and Critical Care Medicine, vol 154 , Sept 1996, pp. 290-294.

3. Pollard M.P , Cheetham B.M.G., Goodyear C.C., M.D. Edgington (BT) " Enhanced shape - invariant pitch and time-scale modification for concatenative speech synthesis", Proc. Int. Conf. for Spoken Language Processing, ICLSP’96, Vol 3, pp 1429-1433. Oct ‘96, Philadelphia,

4. Pollard M.P., Cheetham B.M.G, Goodyear C.C.& Edgington M.D. " Phase interpolation methods for pitch and time-scale modification of voiced speech" Proc. Institute of Acoustics, vol 18 part 9 (1996), pp91-98, Nov 1996

5. Plante F., Kessler H, Cheetham B.M.G. & Earis J.E. " Speech Monitoring of infective laryngitis", Proc. Int. Conf. for Spoken Language Processing, ICLSP’96, Vol 1, pp 700-704. Oct ‘96, Philadelphia.

6. Pollard M.P , Cheetham B.M.G., Goodyear C.C. & M.D. Edgington (BT), "Shape-invariant pitch and time-scale modification of speech by variable order phase interpolation" Proc. IEEE Int. Conf. ICASSP’97, Munich, April 1997 (Vol 2 pp.919-923)

7. Sun X.Q., Plante F, Cheetham BMG & Wong WTK, "Phase modelling of speech excitation for low bit-rate sinusoidal transform coding", Proc. IEEE Int. Conf. ICASSP’97, Munich, April 1997 (Vol 3, pp.1691-1694).

8. Cheetham B.M.G., Choi H.B., Sun X.Q., Goodyear C.C.,Plante F., Wong WTK, "All-pass excitation phase modelling for low bit-rate speech coding", IEEE Int. Symposium on Circuits & Systems, ISCAS’97 Hong Kong, 9-12 June 1997, (paper TH1K15), vol. 4, pp2633-2636

9.. Plante F., Salian S., Scholder J., Cheetham BMG, Earis J. "Inverse filtering of voiced sounds for the study of laryngeal disease" Proc. Int. Conf. Larynx 97, Marseille France, June 16-18, 1997, pp51-54.

10. Watson S.D., Cheetham BMG, Wong WTK, Barrett PA & Lewis AV, "Voice activity detector for ITU-T 8kbit/s speech coding standard G729", Proc Eurospeech’97, Vol 3, pp 1571-1574, Rhodes, Greece, Sept 1997

11. Jones D., Watson, Evans KG Cheetham BMG, "A network speech echo canceller with comfort noise" Proc. Eurospeech ’97, Vol 5, pp. 2607-2610, Rhodes, Greece, Sept, 1997

12. Sun X.Q. & Cheetham BMG, "Speech excitation modelling for low bit-rate speech coding", IEEE Speech Coding Workshop, Philadelphia, USA, 7-10 Sept 1997

13. Doherty, M. J., Spence, D. P., Graham, D., Cheetham, B. M. G., Sun, X. Q. and Earis, J. E., " A vibrating trachea", Thorax, 1997 ; 53: 230-231.

14. Sun XQ and Cheetham BMG, "Chapter 13: Advanced Speech Coding Techniques", In "Insights into Mobile Multimedia Communications" edited by D. Bull et al., pp 207-220, Academic Press Ltd, 1998, ISBN 0-12-140310-6,.

15. Sun X.Q., Cheetham BMG, Earis, JE, "Real time analysis of lung sounds", "Technology and Health Care", Volume 6, no. 1, June 1998, pp. 3-10

16. Plante, F., Kessler, H., Sun, XQ, Cheetham, BMG & Earis, J.E., "Inverse filtering applied to upper airway sounds", "Technology and Health Care", Volume 6, No. 1, June 1998, pp. 23-32.

17. Pollard M.P., Cheetham B.M.G , Goodyear C.C., Edgington M. "Voiced Speech Excitation Synthesis using a sinusoidal model", IEE Electronics Letters,. Vol 34 no 6, 19 March 1998, pp531-532

18. Wong W.T.K., Mak R. M., Cheetham B.M.G. & Sun X.Q. "Chapter 3 : Low bit-rate speech coding", In "Speech Technology for Telecommunications", ed. FA Westall, RD Johnson & AV Lewis, Chapman & Hall 1998, isbn 0 412 79080 7. pp73-103.

19. Sun, XQ, Cheetham, BMG, Evans, KG & Earis JE, "Estimation of analogue prefiltering charactersistics for CORSA standardisation", Technology and Health Care, vol.6, no.4, Nov. 1998, pp.275-283

20. Plante F., Cheetham BMG, et Al "Variable bit-rate speech coding", Proc ICSLP’98, Sydney, Australia, Dec 1998, pp.

21 . Molyneux D, Cheetham BMG, Paris C & Sun, XQ " Discrete all-pole modelling applied to speech coding", Proc ICSLP ’98, Sydney, Australia, Dec 1998, pp.

22. D.J. Molyneux, M.S. Ho, B.M.G. Cheetham, "Application of discrete all-pole modelling to sinusoidal transform coding", Proc. International Conference of Acoust., Speech & Signal Proc., Istanbul, Jun 2000.

23. M.S. Ho, D.J. Molyneux, B.M.G. Cheetham, "Voicing detection in DAP-STC", Proc. IEEE Speech Coding Workshop 2000, Delaware, WI, Sept 2000, pp.

24. N. Li, D.J. Molyneux, M.S. Ho, B.M.G. Cheetham, "Variable bit-rate sinusoidal transform coding using variable order spectral estimation", Proc. International Conference of Speech and Language Processing, Beijing, Oct 2000,.

25 .T.M Jones, M.Trabold, F Plante, BMG Cheetham, J.E Earis, "Objective assessment of hoarseness by measuring jitter".Clinical Otolaryngology 2000, 25, pp.1-4

26. J.E. Earis & BMG Cheetham "Future perspectives for respiratory sound research", European Respiratory Review 2000, (ISSN 0905-9180), 10:77, pp.641-646

27. BMG Cheetham G Charbonneau. A Giordano P Helisto J. Vanderschoot , "Digitisation of Data for Respiratory Sound Recording", European Respiratory Review 2000 10:77, pp.621-624

28. G. Charbonneau, A Edemovic B Cheetham LP Malmberg, J. Vanderschoot , ARA Sovijarvi, "Basic Techniques for Respiratory Sound Analysis" European Respiratory Review 2000: 10:77, pp.625-635

29. J.E.Earis & BMG Cheetham "Current Methods used for computerised respiratory sound analysis"
European Respiratory Review, 2000: (ISSN 0905-9180), 10:77 , pp.586-590

30. L Vannuccinni, J Earis, P Helisto B Cheetham M Rossi, ARA Sovijarvi J Vanderschoot, "Capturing and preprocessing of respiratory sounds", European Respiratory Review, (ISSN 0905-9180), 2000: 10:77, pp.616-620

Article:

BMG Cheetham, PA Barratt & Dave Marston, "Variable bit-rate speech coding for mobile radio", EPSRC "Impact", Sept 1999

Selection from refereed International Conference papers:

(1) T.M. Jones, M.S. Ho, S. Donohugue, B.M.G. Cheetham, P.M.A. Calverley, A.C.S. Swift, J.E. Earis, "Measurements before and after palatoplasty", accepted for publication in American Thoracic Society, San Francisco, USA, May 2001.

(2) T.M. Jones, M.S. Ho, B.M.G. Cheetham, A.C. Swift, J.E. Earis, "Outcome of snoring surgery 1993-1998", accepted for publication in American Thoracic Society, San Francisco, USA, May 2001.

Colloquium papers:

(1). Plante F., Kessler H., Sun X.Q., Cheetham B.M.G. And Earis J.E., "Inverse filtering applied to upper airway sounds", Proc. Second CORSA WPIII Symposium on Signal Processing in Lung Sound Analysis, Sjolulla, Finland,7-8 June 1996.

(2). Sun X.Q., Cheetham B.M.G., Evans K.G. And Earis J.E. "Estimation of analogue pre-filtering characteristics for CORSA standardisation", Proc. Second CORSA WP III Symposium on Signal Processing in Lung Sound Analysis, Sjolulla, Finland, 7-8 June 1996.

(3) D.J. Molyneux, M.S. Ho, B.M.G. Cheetham, P.A. Barrett, "Modified approach to spectral estimation for sinusoidal transform coding", IEE Colloq. On Speech Coding Algorithms for Radio Channels, April 2000.

(4) B.M.G. Cheetham, X.Q. Sun, "All-pass model", in IEE Colloq. On Speech Coding Algorithm for Radio Channels, April 2000.

(5) N. Li & BMG Cheetham paper in Keele, April 2001

(6) LR He & BMG Cheetham paper in Keele, April 2001

Conference papers (abstracts only published):

(1). Sun X.Q., Cheetham B M G, Evans K G & Earis JE, "Characterisation of pre-filter response for lung sounds measurements ", Proc. 21st Int. Conf. on Lung Sounds, Chester, UK, Sept 1996

(2). Plante F, Kessler H, Sun X Q, Cheetham BMG, & Earis JE "The analysis of upper airway sounds by inverse filtering", Proc. 21st Int. Conf. on Lung Sounds, Chester, UK, Sept. 1996

(3). Cheetham BMG, Molyneux D, Sun XQ Earis JE " Discrete All-Pole Modeling applied to upper airways sounds" Proc 23rd INT Conf on Lung Sounds, Boston Oct 1998

(4). Earis JE, Plante, Cheetham Bmg Et Al " Inverse filtering applied to the analysis of hoarse voice", Proc 23rd INT Conf on Lung Sounds, Boston, Oct 1998

(5) T. Jones, M.S. Ho, B.M.G. Cheetham, J.E. Earis, "Measurements before and after palatoplasty", Proc. 25th International Lung Sounds Conference, Chicago, IL, Sep 2000.

(6) T. Jones, M.S. Ho, B.M.G. Cheetham, J.E. Earis, "Acoustic analysis of patients undergoing palatoplasty", Proc. 24th International Lung Sounds Conference, Marburg, Germany, Oct 1999.

Patents:

1. CHEETHAM B.M.G., HOLT C. and MUNDAY E. "Polyphonic coding" U.K. Patent no. 891378.2, 1989. Extended world-wide.

2. CROZIER P., CHEETHAM B.M.G. HOLT C.E. & MUNDAY E. "Noise Reduction" 1993, UK patent number PCT/GB94/00278 (Applicants ref A 24530/WO)

3. As above, Canada and USA patent, Sept 95

4. CHEETHAM SUN and CHOI "All pass model"’ 1998