Araştırma- Tayfun Nesimoğlu

Araştırma- Tayfun Nesimoğlu

• Research Interests:
  • RF/microwave active and passive circuit design
  • Amplifier design and linearization techniques
  • Mixer design, frequency translation and linearization techniques
  • Tunable RF/microwave components
  • Interference suppression and dynamic range enhancement techniques
  • Power efficient transceiver design
  • 3G/4G/LTE mobile communication systems
  • Enabling technologies for Software defined radio (SDR).
  • Broadband transmitter/receiver RF front-end architectures

 

Harmonic Injection and Predistortion Techniques for Wideband Amplifier Linearization (PhD work at University of Bristol Sponsored by Lucent Technologies) 

The efficient utilization of allocated spectrum for mobile and wireless communication systems has become an important issue due to the increasing number of users and services. Distortion and interference impedes high bit rate transmission and degrades spectrum efficiency by allowing fewer channels in the available bandwidth. Increasing the talk time of mobile equipment requires extending thebattery life. The power amplifier is one of the most non-linear and power consuming parts in a transceiver. Extensive research has been carried out on several amplifier linearization schemes to force these devices to operate at their saturation points for maximum efficiency while generating less distortion. The importance of linearity has increased with the introduction of 3rd and 4th generation systems and Software Defined Radio (SDR) concept. These applications require excellent linearitytogether with broadband operation, which are contradictory properties and achieving one without compromising the other is a challenging task for the RF designer. Harmonic injection and analog polynomial predistortion techniques as potential solutions to these new challenges in the RF amplifier design.

 

Experimental results showing the harmonic (HD) and intermodulation distortion (IMD) products at the output of an amplifier.

Block Diagram of a harmonic injection amplifier, experimental results and pictures of some RF circuits. Experimental results demonstrate more than 25 dB of IMD suppression.Polynomial Predistortion for Amplifier Linearization (PhD work at University of Bristol Sponsored by Lucent Technologies)

Analog predistortion is a suitable technique for the applications where broadban capabilities are required. It can offer high efficiency and wide linearization bandwidth due to smaller circuitry, also leading to a possible integration into amplifier ICs  with little impact on size. Therefore, it can be an ideal candidate for PAs used in mobile devices  and also for a reconfigurable radio (SDR).

Block Diagram of a polynomial predistortion power amplifier.

Experimetal results with modulated carriers on average 15 dB suppression of ACPR was obtained. Important for SDR concept.

RF Mixer Linearization (IST-TRUST Project, partners included Siemens, Motorola, Toshiba, Kings Collage London, Panasonic, DoCoMo-Europe, University of Southampton, France Telecom, CSEM, Telefonica, TTI, and 3G.com)

Mixer non-linearity is a bottleneck in flexible transceiver design regardless of the chosen topology. Dr. Nesimoglu has invented a mixer linearisation technique named as

“frequency retranslation”

. The technique improves mixer linearity without compromising the output signal level, and the linearity of the other components in the system is not as critical as in the alternative techniques. Experimental results support the theoretical analysis and show a suppression of distortion products up to 33 dB.

Frequency retranslation block diagram, prototype and experimental results demostrating impressive adjacent channel power ratio (ACPR) improvement. Noise figure (NF) of the receiver was not increased.

MEMS Based Tunable RF Filters (IST-TRUST Project, partners included Siemens, Motorola, Toshiba, Kings Collage London, Panasonic, DoCoMo-Europe, University of Southampton, France Telecom, CSEM, Telefonica, TTI, and 3G.com)

Conventional RF/microwave components cannot be reconfigured and their characteristics cannot be controlled and modified after manufacturing. Frequency tunable RF/Microwave components are

enabling technologies 

for the concept of SDR.

 

An RF-MEMS capacitive switch and a frequency tunable filter utilizing MEMS technology

A MEMS ready frequency tunable filter where bandwidth and center frequency are both tunable 4G Multi-band Linear Power Amplifier (Toshiba Research Ltd. Project)

A tunable amplifier can be constructed that can accommodate GSM, Galileo, GPS, DCS1800, PCS1900, DECT, UMTS/TDD-FDD, Bluetooth, 802.11b/g (US/UK/Japan). Currently available multimode mobile equipment and PDAs require

at least 5

amplifiers to accommodate these standards.

Envelope Elimination and Restoration (EER) can exploit power efficient switching amplifiers (Toshiba Research Ltd. Project)

An envelope elimination and restoration amplifier has been designed that can provide up to around 75% power added efficiency (PAE) and satisfy the emission specifications of WLAN. Current WLAN amplifiers can only achieve around 3-5% PAE for satisfying the WLAN emission specification standards.

 

Patent Publications (International):

1. T. Nesimoglu and M. A. Beach, Linearised mixer using frequency retranslation, World Intellectual Property Organisation (WIPO) patent publication, WO03009464 A2 – 2003-01-30 and WO03009464 A3 – 2003-09-25.

2. T. Nesimoglu and M. A. Beach, Linearised mixer using frequency retranslation, Australian Patent Publication AU2002314389, 2003-03-03.

3. T. Nesimoglu and M. A. Beach, Linearised mixer using frequency retranslation, European patent publication, EP1425847 A2, 2004-06-09.

4. T. Nesimoglu and M. A. Beach, Mixer linearisation using frequency retranslation, UK patent publication, GB0117801D D0 – 2001-09-12 and GB2377837 A – 2003-01-22.

5. T. Nesimoglu and M. A. Beach, Linearised mixer using frequency retranslation, US patent publication, US2004242180 A1 – 2004-12-02.

6. T. Nesimoglu and K. A. Morris, Signal processor for use with a power amplifier in a wireless circuit, World Intellectual Property Organisation (WIPO) patent publication WO2007064007 A1 – 2007-06-07.

7. T. Nesimoglu and K. A. Morris, An EER RF amplifier with PWM signal switching, UK patent publication, GB0524426D D0 – 2006-01-11 and GB2432982 A – 2007-06-06.

8. T. Nesimoglu and K. A. Morris, Signal processor for use with a power amplifier in a wireless circuit, US patent publication US2007123184 A1 – 2007-05-31.

9. T. Nesimoglu and K. A. Morris, Signal processor for use with a power amplifier in a wireless circuit, China Patent and Trademark Office, CN101044689, 2007-09-26.

 

International Journals:

1. T. Nesimoglu, S.C.J. Parker, K.A. Morris, J.P. Mcgeehan, The performance and efficiency of envelope elimination and restoration transmitters for future multiple-input multiple-output wireless local area networks, IET Communications, Volume 2, Issue 3, March 2008, Pages:473 – 483.

2. B. E. Carey-Smith, P. A. Warr, M. A. Beach and T. Nesimoglu, Wide Tuning-Range Planar Filters Using Lumped-Distributed Coupled Resonators, IEEE Transactions on Microwave Theory and Techniques, Volume: 53, Issue: 2, Feb. 2005, Pages: 777-785.

3. B. E. Carey-Smith, P. A. Warr, M. A. Beach and T. Nesimoglu, Tunable lumped-distributed capacitively-coupled transmission-line filter, IEE Electronics Letters, Volume 40, Issue: 7, 1 April 2004 Pages:434 – 436.

4. T. Nesimoglu, M. A. Beach, P. A. Warr and J. R. MacLeod, Linearised Mixer using Frequency Retranslation, IEE Electronics Letters, December 2001, Vol. 37, No. 25, Pages: 1493-1494.

5. T. Nesimoglu, C. N. Canagarajah and J. P. McGeehan, The Analysis and Performance of A Simple Active Feedback Linearisation Scheme, IEE Electronics Letters, April 2000, Vol. 36, No. 8, Pages: 703-705.

 

International Conferences:

1. Turgul, V.; Dirim, M.; Bilgin, S.B.; Gok, H.I.; Nesimoglu, T., Broadband signal search and direction finding at UHF frequencies, 5th Mediterranean Microwave Symposium (MMS), Middle East Technical University, Northern Cyprus Campus, August 2010, Pages: 288 – 291.

2. T. Nesimoglu, Z. Charalampopoulos and M. A. Beach, Interference Suppression in Radio Receivers by using Frequency Retranslation, IEEE Wireless and Microwave Technology Conference, Florida, USA, April 2009.

3. T. Nesimoglu, K. A. Morris, S. C. J. Parker and J. P. McGeehan, Improved EER Transmitters for WLAN, IEEE Radio and Wireless Symposium, 17-19 January 2006, San Diego, California, USA, Pages: 239-242.

4. B. E. Carey-Smith, P. A. Warr, M. A. Beach and T. Nesimoglu, A MEMS-Ready Wide Tuning Range Planar Resonator With Application to Microwave Flexible Filters, Asia Pacific Microwave Conference, Seoul, Korea, November 2003, Pages: 1581-1584.

5. T. Nesimoglu, M. A. Beach, J. R. MacLeod and P. A. Warr, A Novel Mixer Linearisation Technique using Frequency Retranslation, IST Mobile & Wireless Telecommunications Summit, June 2002, Thessaloniki, Greece, Pages: 570-574.

6. T. Nesimoglu, M. A. Beach, J. R. MacLeod and P. A. Warr, Mixer Linearisation for Software Defined Radio Applications, IEEE Vehicular Technology Conference, September 2002, Vancouver, Canada, Pages: 134-138.

7. J. R. MacLeod, T. Nesimoglu, M. A. Beach and P. A. Warr, Miniature Distributed Filters for Software Re-configurable Radio Applications, IST Mobile & Wireless Telecommunications Summit, June 2002, Thessaloniki, Greece, Pages: 159-163.

8. J. R. MacLeod, T. Nesimoglu, M. A. Beach and P. A. Warr, Enabling Technologies for Software Defined Radio Transceivers, Military Communications Conference-MILCOM, October 2002, California, USA.

9. T. Nesimoglu, C. N. Canagarajah and J. P. McGeehan, A Broadband Polynomial Predistorter for Reconfigurable Radio, IEEE Vehicular Technology Conference, Rhodes, May 2001, IEEE CDROM Catalogue No: 01CH37202C.

10. J. R. MacLeod, M. A. Beach, P. A. Warr and T. Nesimoglu, A Software Defined Radio Receiver Test-Bed, IEEE Vehicular Technology Conference 2001-Fall, Atlantic City, Volume: 3, Pages: 1565-1569.

11. J. R. MacLeod, M. A. Beach, P. A. Warr and T. Nesimoglu, Filter Considerations in the Design of a Software-Defined Radio, IST Mobile Summit, September 2001, Barcelona, Spain, Pages: 363-368.

12. T. Nesimoglu, C. N. Canagarajah and J. P. McGeehan, An Active Feedback for Wideband Amplifier Linearisation, International Conference on 3G Mobile Communication Technologies, London, March 2000, Pages: 112-116.

13. T. Nesimoglu, C. N. Canagarajah, J. P. McGeehan and R. J. Wilkinson, A Novel Wideband Active Feedback Amplifier Linearisation Scheme Suitable for Handsets, IEEE Vehicular Technology Conference, Tokyo, May 2000.

14. T. Nesimoglu, R. J. Wilkinson, C. N. Canagarajah and J. P. McGeehan, Second Harmonic Zone Injection for Amplifier Linearisation, IEEE Vehicular Technology Conference, Houston, May 1999, Pages: 2353-2357.

15. T. Nesimoglu, D. Budimir, R. M. Moazzam, and C. S. Aitchison, Second Harmonic Injecting Technique for Low Intermodulation RF/Microwave Amplifiers, Third IEEE High Frequency Colloquium, 19 September 1997, University of Leeds, Leeds, UK.

 

Reviewed technical papers for:

1. IEEE International Conference on Communications, ICC.

2. IEEE Vehicular Technology Conference, VTC.

3. IEEE Transactions on Circuits and Systems, TCAS.

4. IEEE Transactions on Wireless Communications.

5. IEEE Wireless Communications and Networking Conference.

6. IEE Proceedings of Microwaves Antennas and Propagation.

7. International Symposium on Wireless Communication Systems, ISWCS.

 

Contact for more information

Dr. Tayfun Nesimoglu
Middle East Technical University
Northern Cyprus Campus (METU-NCC)
Office: R-218
Kalkanli, Guzelyurt, TRNC
Mersin 10, Turkey

Tel: + 90 (0)392 661 2935 (Office)

Fax: + 90 (0)392 661 2949

Email: ntayfunmetu.edu.tr

Web: http://www.metu.edu.tr/~ntayfun/