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Papers by bulent yagci

Proceedings of the IEEE 12th Signal Processing and Communications Applications Conference, 2004.

Mikrogerit anten yapilannm; hafiflik, ucuzluk, yiizeysel kolay kullanim ve diger devrelerle tiiml... more Mikrogerit anten yapilannm; hafiflik, ucuzluk, yiizeysel kolay kullanim ve diger devrelerle tiimlegtirilebilme gibi 6nemli Bzellikleri nedeniyle, iizerinde genig olpiide paligmalar y a p h i $ ve pok &tli kullanim alanlan bulunmqtur.Ku bandinda iki farkli uydudan gelen yayinlan iziemek ipin, kupixk ve hllamgli bir alici anten sistemi tasanm paligmasi yapilmighr. Sistem belirli bir boylam farhnda yerlegtirilmig iki farkh uyduda bulunan igmtleri, elekhonik olarak ,gin demetini kaydrarak alia sisteme ilgili TVmata ipretleri aktarabilecek Bzellikte olacakhr. Ayni zamanda hareketli all? noktalannda da ban eklemelerle, uydu igaret aliqi gevklegtirebilecek lizellige sahip olabilecektir. Bu pahgmada iki ayn ism demetine sahip uydu alia anteni ipin hem elektromagnetik hem de elektronik devre gevklegtirimindeki zorluklar ve uygulamada kaqilqilan sorunlara iligkin p a z m yirntemleri geligtirilmi$ir.

This article has been accepted for inclusion in a future issue of this journal. Content is final ... more This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.

Abstract This paper is related to Turkiye's first TV channel Istanbul Technical University T... more Abstract This paper is related to Turkiye's first TV channel Istanbul Technical University TV's born and contribution to Turkish TV broadcasting. ITU TV was setted up as a laboratory in March 1952. Chair of the High Frequency Department, Prof. Dr. Mustafa Santur and his student Assistant Proffesor Adnan Ataman were the constitutive of the ITU-TV. ITU-TV is used as a laboratory for a long time.

In this work, a circularly polarized antenna array operating at 2.45 GHz has been designed. This ... more In this work, a circularly polarized antenna array operating at 2.45 GHz has been designed. This kinds of antennas should match the gain requirement of the system in order to communicate with experimental small satellites as they are used as ground station antennas. The easiest way to prevent polarization loss between receiver and transmitter because of unstable movement of the satellite which can go up to a few kilometers is to use circularly polarized antennas. In this work a 4 element circularly polarized antenna array has been designed using sequential rotation technique. As a result it has been seen that the return loss bandwidth is about 9 percent and axial ratio bandwidth is capable of covering ISM 2.4 band. It has been seen that maximum gain of the antenna is above 8dBic.

The phase and amplitude responses of a high power amplifier have a significant role in linearity ... more The phase and amplitude responses of a high power amplifier have a significant role in linearity performance. Analytical analysis of a high power solid-state device at linear and saturation regions can provide initial information about the overall performance before design and implementation. This study presents the analytical analysis of the amplitude and phase sensitivity of a GaN HEMT. The single-parameter and first-order analysis was considered to calculate sensitivity functions regarding the nonlinear components of the transistor. A simplified equivalent circuit model was used for the analysis. The analytic results were verified with a high power Class-AB amplifier at X-band while the maximum output power of 37 dBm at 8.2 GHz. The results show that the single-parameter and first-order sensitivity analysis can be used to evaluate the phase response of the amplifier to estimate the initial parameters before the final design and implementation of the amplifier.

Turkish Journal of Electrical Engineering and Computer Sciences, 2017

This article presents both a four-element novel microstrip array antenna and a low noise amplifie... more This article presents both a four-element novel microstrip array antenna and a low noise amplifier (LNA) for a Ku-band small satellite receiver. It includes all design details with measurement results of the fabricated array antenna and LNA. Measured minimum and maximum gains of the proposed antenna are 10.1 and 10.9 dBi in 11.9-12.9 GHz band frequency. The designed LNA has a noise figure lower than 1.5 dB and gain higher than 8 dB (at 2 V, 10 mA biasing). In order to reduce the design period and cost, discrete components are chosen and a hetero-junction FET is used as the active component because of better Ku band performance and stability. The simulation and fabricated measurement outcomes of the array antenna and LNA show competent and qualified matching that can be practically used together.

ABSTRACT In this paper, free space path loss, ray tracing with one and two reflection points and ... more ABSTRACT In this paper, free space path loss, ray tracing with one and two reflection points and logarithmic distance path loss models are used to determine distance between nodes according to RSSI values. First of all, required parameters to use called models are determined by making RSSI characterization study in corridors. Then determined parameters are used to perform a localization test RSSI characterization and localization tests are carried out for different areas and environments' effects and success of all models are investigated.

Abstract— This paper describes effects of different frequencies on RSSI measurements and proposes... more Abstract— This paper describes effects of different frequencies on RSSI measurements and proposes how to increase distance measurement accuracy by using these effects as a new method. RSSI values depend on communication frequency and distance between receiver and ...

... Osman Ceylan Dept. of Electronics Engineering Istanbul Technical University Istanbul, Turkey ... more ... Osman Ceylan Dept. of Electronics Engineering Istanbul Technical University Istanbul, Turkey ceylanos@itu.edu.tr Bulent Yagci Dept. of Electronics Engineering Istanbul Technical University Istanbul, Turkey bulent.yagci@itu.edu.tr ...

Beykent üniversitesi fen ve mühendislik bilimleri dergisi, Jun 26, 2016

Software defined radio (SDR) applications are usually preferred in low power flexible communicati... more Software defined radio (SDR) applications are usually preferred in low power flexible communication systems. In this paper, a software defined Frequency Modulation (FM) demodulator is presented. Mixed demodulation technique is used to build a digital FM demodulator which has 16 MHz sampling rate. Proposed system was implemented successfully on a Field Programmable Gate Array (FPGA). The system uses 1247 logic elements. FPGA's power consumption is 113.56 mW. The system was tested and verified with a test bed including Analog Digital Converter (ADC) and Digital Analog Converter (DAC).

IEEE Microwave Magazine, Mar 1, 2016

T he space race has played a significant role in the history of the last half century, and satell... more T he space race has played a significant role in the history of the last half century, and satellites are among the most important parts of space race and technology. More than 6,000 artificial satellites have been deployed since the first, Sputnik, in 1957; some 1,000 are still in operation [1]. When most people not involved in satellite technologies see or hear the word "satellite," they think of satellites weighing several tons. However, developing material, rocket, and mechanical and electrical technologies are rapidly changing the world of artificial satellites.

Beykent üniversitesi fen ve mühendislik bilimleri dergisi, Dec 29, 2015

Bu calismada 2.4 GHz frekansinda 5W cikis gucune sahip AB sinifi bir guc kuvvetlendiricisi tasarl... more Bu calismada 2.4 GHz frekansinda 5W cikis gucune sahip AB sinifi bir guc kuvvetlendiricisi tasarlanmis ve gerceklenmistir. Tasarimda Sumitomo Electric firmasinin SGNE010MK GaN HEMT’i kullanilmistir. Firma tarafindan saglanan dogrusal olmayan model ile bilgisayar destekli analiz ve tasarim yapilmistir. Taban olarak Taconic firmasinin 0.76mm kalinliginda, dielektrik katsayisi 3 olan TSM-DS3 tabani kullanilmistir. Tasarlanan kuvvetlendiricinin, surekli dalga isaret ile 5W cikis gucunde en yuksek eklenmis verimi % 44 olarak olculmustur ve 50 MHz bant genisliginde %40 uzerinde verime sahiptir. Elde edilen sonuclara gore, tasarlanan kuvvetlendirici ayni tranzistor ile tasarlanmis olan raporlanmis AB sinifi guc kuvvetlendiricilerine gore daha yuksek frekansta daha yuksek verime sahiptir.

... Seyyid M. Dilek, İsmail Bayram, M. Emin Şafak, Osman Ceylan, H. Bülent Yağcı ... Modülasyon s... more ... Seyyid M. Dilek, İsmail Bayram, M. Emin Şafak, Osman Ceylan, H. Bülent Yağcı ... Modülasyon sürekli olduğundan dolayı iletilen her sembol bir önceki sembole bağımlıdır, bununla beraber hafıza gereksinimi doğar [4]. Spektral etkinliği ve sabit zarfı sayesinde Mobil ...

ABSTRACT In this paper, implementation of a FPGA-based and VHDL coded reconfigurable frequency sh... more ABSTRACT In this paper, implementation of a FPGA-based and VHDL coded reconfigurable frequency shift keying (FSK) modulator for nano-satellite communication systems is presented. Reconfigurable FSK modulator includes 2-FSK and 4-FSK modulators. The system is compatible with AX.25 data link layer protocol for general amateur radio communication which is popular in micro/nano satellite communication. ROM based direct digital synthesizer (DDS) generates a sinusoidal wave at the output with a specified frequency and phase.

ABSTRACT In recent years, small satellites have begun to draw attention due to reconstruction in ... more ABSTRACT In recent years, small satellites have begun to draw attention due to reconstruction in low cost of manufacture and faster building time. In this project, radio transmitter system is built for nano and micro satellites. Transmitter broadcasts 1W power in 435 MHz free amateur satellite communication band, and also has software defined radio structure in all modules except upconvertion part. Design was capable of DE0-Nano evaluation board connection; it is regard of PC104 connector structure standard. FSK modulation and AX.25 data link layer protocol are designed using digital circuit in FPGA and implemented with VHDL.

Nan o satellite structures have limited communication ability due to limited power and size. Most... more Nan o satellite structures have limited communication ability due to limited power and size. Most of satellite includes sensors, for instance camera, also image transfer requires more data transfer speed. In this project, 2.4 GHz (S Band) communication system is designed for LEO satellites (700-900 km). System includes system-on-chip transmitter device, preamplifier, band pass filter, power amplifier and microstrip antenna

Mikroşerit anten yapılarının; hafiflik, ucuzluk, yüzeysel kolay kullanım ve diğer devrelerle... more Mikroşerit anten yapılarının; hafiflik, ucuzluk, yüzeysel kolay kullanım ve diğer devrelerle tümleştirilebilme gibi önemli özellikleri nedeniyle, üzerinde geniş ölçüde çalışmalar yapılmış ve çok çeşitli kullanım alanları bulunmuştur.Ku bandında uydu yayınlarını izlemek için kullanılabilecek ucuz, küçük ve verimli bir alıcı sistemi tasarım çalışması yapılmıştır. Sistem belirli bir boylam farkında yerleştirilmiş bulunan yer sabit yörüngeli uyduları, elektronik olarak ışın demetini kaydırarak, alıcı sisteme ilgili TV/Data işaretleri aktarabilecek özellikte olacaktır. Aynı zamanda hareketli alış noktalarında da bazı eklemelerle, uydu işaret alışı gerçekleştirebilecek özelliğe sahip olabilecektir. Bu çalışmada hem elektromagnetik hem de elektronik devre gerçekleştirimindeki zorluklar ve uygulamada karşılaşılan sorunlara ilişkin çözüm y&ou...

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2018

Class-F type amplification stands on proper termination of harmonics such as short for even harmo... more Class-F type amplification stands on proper termination of harmonics such as short for even harmonics and open for odd harmonics. Moreover, termination of only the first few harmonics is practical for high-frequency circuits, while obtaining satisfactory short and open terminations at high frequencies is a challenging design issue. In the present study, a topology of harmonics termination for Class-F load network with 2nd and 3rd harmonics and its relative analytical analysis are presented. The proposed output termination structure for Class-F type amplification provides an improved short termination of 2nd harmonic; therefore, the efficiency of the power amplifier increases. In addition, the topology implemented with the microstrip lines has a tunable structure, and it is suitable for very high-frequency applications due to its straightforward architecture. An X-Band high power amplifier for a small satellite transmitter is designed and fabricated with the proposed method. A 0.25 µm GaN on SiC HEMT having a total gate width of 1.25 mm is used. The PA achieves the peak P AE of 55% at 8.1 GHz while the output power is 36 dBm at the 3 − dB compression point. The Class-F PA has higher than 50% P AE and 35.5 dBm output power in the band of 7.9 − 8.2 GHz. The measured linear power gain is 16.2 dB .

Proceedings of the IEEE 12th Signal Processing and Communications Applications Conference, 2004.

Mikrogerit anten yapilannm; hafiflik, ucuzluk, yiizeysel kolay kullanim ve diger devrelerle tiiml... more Mikrogerit anten yapilannm; hafiflik, ucuzluk, yiizeysel kolay kullanim ve diger devrelerle tiimlegtirilebilme gibi 6nemli Bzellikleri nedeniyle, iizerinde genig olpiide paligmalar y a p h i $ ve pok &tli kullanim alanlan bulunmqtur.Ku bandinda iki farkli uydudan gelen yayinlan iziemek ipin, kupixk ve hllamgli bir alici anten sistemi tasanm paligmasi yapilmighr. Sistem belirli bir boylam farhnda yerlegtirilmig iki farkh uyduda bulunan igmtleri, elekhonik olarak ,gin demetini kaydrarak alia sisteme ilgili TVmata ipretleri aktarabilecek Bzellikte olacakhr. Ayni zamanda hareketli all? noktalannda da ban eklemelerle, uydu igaret aliqi gevklegtirebilecek lizellige sahip olabilecektir. Bu pahgmada iki ayn ism demetine sahip uydu alia anteni ipin hem elektromagnetik hem de elektronik devre gevklegtirimindeki zorluklar ve uygulamada kaqilqilan sorunlara iligkin p a z m yirntemleri geligtirilmi$ir.

This article has been accepted for inclusion in a future issue of this journal. Content is final ... more This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.

Abstract This paper is related to Turkiye's first TV channel Istanbul Technical University T... more Abstract This paper is related to Turkiye's first TV channel Istanbul Technical University TV's born and contribution to Turkish TV broadcasting. ITU TV was setted up as a laboratory in March 1952. Chair of the High Frequency Department, Prof. Dr. Mustafa Santur and his student Assistant Proffesor Adnan Ataman were the constitutive of the ITU-TV. ITU-TV is used as a laboratory for a long time.

In this work, a circularly polarized antenna array operating at 2.45 GHz has been designed. This ... more In this work, a circularly polarized antenna array operating at 2.45 GHz has been designed. This kinds of antennas should match the gain requirement of the system in order to communicate with experimental small satellites as they are used as ground station antennas. The easiest way to prevent polarization loss between receiver and transmitter because of unstable movement of the satellite which can go up to a few kilometers is to use circularly polarized antennas. In this work a 4 element circularly polarized antenna array has been designed using sequential rotation technique. As a result it has been seen that the return loss bandwidth is about 9 percent and axial ratio bandwidth is capable of covering ISM 2.4 band. It has been seen that maximum gain of the antenna is above 8dBic.

The phase and amplitude responses of a high power amplifier have a significant role in linearity ... more The phase and amplitude responses of a high power amplifier have a significant role in linearity performance. Analytical analysis of a high power solid-state device at linear and saturation regions can provide initial information about the overall performance before design and implementation. This study presents the analytical analysis of the amplitude and phase sensitivity of a GaN HEMT. The single-parameter and first-order analysis was considered to calculate sensitivity functions regarding the nonlinear components of the transistor. A simplified equivalent circuit model was used for the analysis. The analytic results were verified with a high power Class-AB amplifier at X-band while the maximum output power of 37 dBm at 8.2 GHz. The results show that the single-parameter and first-order sensitivity analysis can be used to evaluate the phase response of the amplifier to estimate the initial parameters before the final design and implementation of the amplifier.

Turkish Journal of Electrical Engineering and Computer Sciences, 2017

This article presents both a four-element novel microstrip array antenna and a low noise amplifie... more This article presents both a four-element novel microstrip array antenna and a low noise amplifier (LNA) for a Ku-band small satellite receiver. It includes all design details with measurement results of the fabricated array antenna and LNA. Measured minimum and maximum gains of the proposed antenna are 10.1 and 10.9 dBi in 11.9-12.9 GHz band frequency. The designed LNA has a noise figure lower than 1.5 dB and gain higher than 8 dB (at 2 V, 10 mA biasing). In order to reduce the design period and cost, discrete components are chosen and a hetero-junction FET is used as the active component because of better Ku band performance and stability. The simulation and fabricated measurement outcomes of the array antenna and LNA show competent and qualified matching that can be practically used together.

ABSTRACT In this paper, free space path loss, ray tracing with one and two reflection points and ... more ABSTRACT In this paper, free space path loss, ray tracing with one and two reflection points and logarithmic distance path loss models are used to determine distance between nodes according to RSSI values. First of all, required parameters to use called models are determined by making RSSI characterization study in corridors. Then determined parameters are used to perform a localization test RSSI characterization and localization tests are carried out for different areas and environments' effects and success of all models are investigated.

Abstract— This paper describes effects of different frequencies on RSSI measurements and proposes... more Abstract— This paper describes effects of different frequencies on RSSI measurements and proposes how to increase distance measurement accuracy by using these effects as a new method. RSSI values depend on communication frequency and distance between receiver and ...

... Osman Ceylan Dept. of Electronics Engineering Istanbul Technical University Istanbul, Turkey ... more ... Osman Ceylan Dept. of Electronics Engineering Istanbul Technical University Istanbul, Turkey ceylanos@itu.edu.tr Bulent Yagci Dept. of Electronics Engineering Istanbul Technical University Istanbul, Turkey bulent.yagci@itu.edu.tr ...

Beykent üniversitesi fen ve mühendislik bilimleri dergisi, Jun 26, 2016

Software defined radio (SDR) applications are usually preferred in low power flexible communicati... more Software defined radio (SDR) applications are usually preferred in low power flexible communication systems. In this paper, a software defined Frequency Modulation (FM) demodulator is presented. Mixed demodulation technique is used to build a digital FM demodulator which has 16 MHz sampling rate. Proposed system was implemented successfully on a Field Programmable Gate Array (FPGA). The system uses 1247 logic elements. FPGA's power consumption is 113.56 mW. The system was tested and verified with a test bed including Analog Digital Converter (ADC) and Digital Analog Converter (DAC).

IEEE Microwave Magazine, Mar 1, 2016

T he space race has played a significant role in the history of the last half century, and satell... more T he space race has played a significant role in the history of the last half century, and satellites are among the most important parts of space race and technology. More than 6,000 artificial satellites have been deployed since the first, Sputnik, in 1957; some 1,000 are still in operation [1]. When most people not involved in satellite technologies see or hear the word "satellite," they think of satellites weighing several tons. However, developing material, rocket, and mechanical and electrical technologies are rapidly changing the world of artificial satellites.

Beykent üniversitesi fen ve mühendislik bilimleri dergisi, Dec 29, 2015

Bu calismada 2.4 GHz frekansinda 5W cikis gucune sahip AB sinifi bir guc kuvvetlendiricisi tasarl... more Bu calismada 2.4 GHz frekansinda 5W cikis gucune sahip AB sinifi bir guc kuvvetlendiricisi tasarlanmis ve gerceklenmistir. Tasarimda Sumitomo Electric firmasinin SGNE010MK GaN HEMT’i kullanilmistir. Firma tarafindan saglanan dogrusal olmayan model ile bilgisayar destekli analiz ve tasarim yapilmistir. Taban olarak Taconic firmasinin 0.76mm kalinliginda, dielektrik katsayisi 3 olan TSM-DS3 tabani kullanilmistir. Tasarlanan kuvvetlendiricinin, surekli dalga isaret ile 5W cikis gucunde en yuksek eklenmis verimi % 44 olarak olculmustur ve 50 MHz bant genisliginde %40 uzerinde verime sahiptir. Elde edilen sonuclara gore, tasarlanan kuvvetlendirici ayni tranzistor ile tasarlanmis olan raporlanmis AB sinifi guc kuvvetlendiricilerine gore daha yuksek frekansta daha yuksek verime sahiptir.

... Seyyid M. Dilek, İsmail Bayram, M. Emin Şafak, Osman Ceylan, H. Bülent Yağcı ... Modülasyon s... more ... Seyyid M. Dilek, İsmail Bayram, M. Emin Şafak, Osman Ceylan, H. Bülent Yağcı ... Modülasyon sürekli olduğundan dolayı iletilen her sembol bir önceki sembole bağımlıdır, bununla beraber hafıza gereksinimi doğar [4]. Spektral etkinliği ve sabit zarfı sayesinde Mobil ...

ABSTRACT In this paper, implementation of a FPGA-based and VHDL coded reconfigurable frequency sh... more ABSTRACT In this paper, implementation of a FPGA-based and VHDL coded reconfigurable frequency shift keying (FSK) modulator for nano-satellite communication systems is presented. Reconfigurable FSK modulator includes 2-FSK and 4-FSK modulators. The system is compatible with AX.25 data link layer protocol for general amateur radio communication which is popular in micro/nano satellite communication. ROM based direct digital synthesizer (DDS) generates a sinusoidal wave at the output with a specified frequency and phase.

ABSTRACT In recent years, small satellites have begun to draw attention due to reconstruction in ... more ABSTRACT In recent years, small satellites have begun to draw attention due to reconstruction in low cost of manufacture and faster building time. In this project, radio transmitter system is built for nano and micro satellites. Transmitter broadcasts 1W power in 435 MHz free amateur satellite communication band, and also has software defined radio structure in all modules except upconvertion part. Design was capable of DE0-Nano evaluation board connection; it is regard of PC104 connector structure standard. FSK modulation and AX.25 data link layer protocol are designed using digital circuit in FPGA and implemented with VHDL.

Nan o satellite structures have limited communication ability due to limited power and size. Most... more Nan o satellite structures have limited communication ability due to limited power and size. Most of satellite includes sensors, for instance camera, also image transfer requires more data transfer speed. In this project, 2.4 GHz (S Band) communication system is designed for LEO satellites (700-900 km). System includes system-on-chip transmitter device, preamplifier, band pass filter, power amplifier and microstrip antenna

Mikroşerit anten yapılarının; hafiflik, ucuzluk, yüzeysel kolay kullanım ve diğer devrelerle... more Mikroşerit anten yapılarının; hafiflik, ucuzluk, yüzeysel kolay kullanım ve diğer devrelerle tümleştirilebilme gibi önemli özellikleri nedeniyle, üzerinde geniş ölçüde çalışmalar yapılmış ve çok çeşitli kullanım alanları bulunmuştur.Ku bandında uydu yayınlarını izlemek için kullanılabilecek ucuz, küçük ve verimli bir alıcı sistemi tasarım çalışması yapılmıştır. Sistem belirli bir boylam farkında yerleştirilmiş bulunan yer sabit yörüngeli uyduları, elektronik olarak ışın demetini kaydırarak, alıcı sisteme ilgili TV/Data işaretleri aktarabilecek özellikte olacaktır. Aynı zamanda hareketli alış noktalarında da bazı eklemelerle, uydu işaret alışı gerçekleştirebilecek özelliğe sahip olabilecektir. Bu çalışmada hem elektromagnetik hem de elektronik devre gerçekleştirimindeki zorluklar ve uygulamada karşılaşılan sorunlara ilişkin çözüm y&ou...

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2018

Class-F type amplification stands on proper termination of harmonics such as short for even harmo... more Class-F type amplification stands on proper termination of harmonics such as short for even harmonics and open for odd harmonics. Moreover, termination of only the first few harmonics is practical for high-frequency circuits, while obtaining satisfactory short and open terminations at high frequencies is a challenging design issue. In the present study, a topology of harmonics termination for Class-F load network with 2nd and 3rd harmonics and its relative analytical analysis are presented. The proposed output termination structure for Class-F type amplification provides an improved short termination of 2nd harmonic; therefore, the efficiency of the power amplifier increases. In addition, the topology implemented with the microstrip lines has a tunable structure, and it is suitable for very high-frequency applications due to its straightforward architecture. An X-Band high power amplifier for a small satellite transmitter is designed and fabricated with the proposed method. A 0.25 µm GaN on SiC HEMT having a total gate width of 1.25 mm is used. The PA achieves the peak P AE of 55% at 8.1 GHz while the output power is 36 dBm at the 3 − dB compression point. The Class-F PA has higher than 50% P AE and 35.5 dBm output power in the band of 7.9 − 8.2 GHz. The measured linear power gain is 16.2 dB .