An Oscillator and a Mixer for 140-GHz Heterodyne Receiver Front-End based on SiGe HBT Technology

JOURNAL OF SEMICONDUCTOR TECHNOLOGY AND SCIENCE, VOL.15, NO.1, FEBRUARY, 2015 http://dx.doi.org/10.5573/jsts.2015.15.1.029 An Oscillator and a Mixer for 140-GHz Heterodyne Receiver Front-End based on SiGe HBT Technology Daekeun Yoon 1, Kiryong Song 1, Mehmet Kaynak 2, Bernd Tillack 2, and Jae-Sung Rieh 1 Abstract This paper reports a couple of key circuit blocks developed for heterodyne receiver front-ends operating near 140 GHz based on SiGe HBT technology. Firstly, a 123-GHz oscillator was developed based on Colpitts topology, which showed - 5 dbm output power and phase noise of -107.34 dbc/hz at 10 MHz. DC power dissipation was 25.6 mw. Secondly, a 135 GHz mixer was developed based on a modified Gilbert Cell topology, which exhibited a peak conversion gain of 3.6 db at 1 GHz IF at fixed LO frequency of 134 GHz. DC power dissipation was 3 mw, which mostly comes from the buffer. Index Terms SiGe HBT, oscillator, mixer I. INTRODUCTION The frequency band beyond 100 GHz is attracting increasing recent interests for various applications, which include broadband communication and mm-wave/thz imaging [1, 2]. The communications systems benefit from this raised frequency for the wide bandwidth available, while the image systems will show higher resolution with the reduced wavelength for this frequency band. For both communication and imaging applications, heterodyne systems play a great role. It is a well-known fact that heterodyne systems have long been Manuscript received Aug. 25, 2014; accepted Dec. 22, 2014 A part of this work was presented in Asia-Pacific Workshop on Fundamental and Applications of Advanced Semiconductor Devices, Kanazawa, Japan, July. 2014 Daekeun Yoon, Kiryong Song, Jae-Sung Rieh are with the School of Electrical Engineering, Korea University, Seoul, Korea. Mehmet Kaynak and Bernd Tillack are with IHP, Frankfurt (Oder) Germany E-mail : jsrieh@korea.ac.kr adopted for communication applications for various modulation schemes. Imaging systems also benefit from the heterodyne technique, especially for THz applications where direct detection is not readily available or heterodyne detection outperforms direct detection [2, 3]. Hence, the implementation of heterodyne systems operating beyond 100 GHz is of growing interest for high-end communication systems and imaging systems, as well as a wide range of other applications these days. In particular, the frequency band near 140 GHz is highly attractive since it falls on one of the earth atmospheric windows. It is located between an oxygen and a water absorption peak, leading to a low attenuation rate. For this reason, there have been plenty of recent reports to develop heterodyne systems near this band [4, 5]. For a heterodyne system, two circuit components are indispensable: oscillator and mixer. In this paper, we report an oscillator and a mixer that can be readily adopted for heterodyne systems operating near 140 GHz, both designed and fabricated based on IHP 0.13-mm SiGe HBT technology [6]. II. 123-GHZ OSCILLATOR The schematic of the oscillator developed in this work is shown in Fig. 1. As a fundamental-mode oscillator, it consists of an oscillator core based on Colpitts topology and an inductively degenerated common emitter buffer. The differential oscillator core is composed of two transistors, each connected to the ground and supply voltage through microstrip lines. The capacitive division, a key feature of Colpitts topology, is realized with the parasitic capacitance of the transistors as well as that of the passive components included. They also dictate the

30 DAEKEUN YOON et al : AN OSCILLATOR AND A MIXER FOR 140-GHZ HETERODYNE RECEIVER FRONT-END BASED ON D-band Mixer IF Power Supply DUT Spectrum Analyzer LO RF probe GPPPPG DC probe Spectrum Analyzer RF probe Power Supply x4 Source Module DUT GPPPPG DC probe x2 D-band Subharmonic Mixer Signal Generator Power Supply Fig. 1. Schematic of the oscillator, Die photo of fabricated oscillator. oscillation frequency of the oscillator. Such an approach leads to a compact design of the oscillator. The buffer isolates the core from the external load, which helps to suppress the loading effect. For characterization purpose only, one of the differential output nodes is terminated to 50 ohm to be compatible with a single-ended measurement. A die photo of the fabricated oscillator is shown in Fig. 1. It occupies an area of 630 700 mm2 including the pads. The oscillator was characterized with three different measurement setups, each for the output spectrum, the phase noise, and the RF output power. The three measurement setups are depicted in Fig. 2. The photo of the measurement setup for phase noise measurement, as an example, is shown in Fig. 3. For the measurement of the output spectrum, the output signal of the oscillator is first frequency downconverted with an externally connected Quinstar harmonic mixer and then captured by an Agilent 8565E spectrum analyzer. Local oscillation (LO) for the mixer is provided by the spectrum analyzer. The measured output spectrum is shown in Fig. 4. It indicates an oscillation frequency of 123 GHz, which may be applied to RF input signal ranging around 140 GHz with a proper PM4 Powermeter DUT RF probe GPPPPG DC probe (c) Fig. 2. Output spectrum frequency measurement setup, Phase noise measurement setup, (c) Output power measurement setup. Fig. 3. Photo of the measurement setup for phase noise. choice of IF frequency. The measurement setup for the phase noise, which is shown in Fig. 2, is similar to the one for output spectrum measurement but the frequency downconversion section is different. Instead of the harmonic mixer with a large harmonic number, a 2 subharmonic mixer (from VDI) is used, which shows a much smaller conversion loss. It requires an external separate LO,

JOURNAL OF SEMICONDUCTOR TECHNOLOGY AND SCIENCE, VOL.15, NO.1, FEBRUARY, 2015 31 Fig. 4. Measured output spectrum of the oscillator, Measured phase noise of the oscillator. though, and a V-band source module driven by an Agilent E8247C signal generator was employed for the purpose. The measured phase noise is shown in Fig. 4, which exhibits a value of -107 dbc/hz at 10 MHz frequency offset. The output power was measured with a much simpler setup as illustrated in Fig. 2(c). The output of the oscillator is directly acquired by an Erickson PM4 power meter without frequency down-conversion. In such a measurement, it is naturally assumed that the dominant RF power injected into the power meter is that from the oscillator. Such a guess is quite practical, since the Dband waveguide probe that is used for probing the circuit will filter out the signal below the cut-off frequency of the waveguide. It is true that the frequency components beyond the D-band may survive through the over-mode propagation in the waveguide, but there should be no significant component at such upper frequency bands except for the harmonics of the intended output signal, the power of which is supposed to be much smaller than the fundamental signal being measured. The measured output power of the oscillator was -5 dbm, in which the Fig. 5. Schematic of the mixer developed, Die photo of the fabricated mixer. losses from the GGB waveguide probe were accounted for. The oscillator was operated with a supply voltage of 1.6 V for both oscillator core and buffer, which draws current of 12 ma and 4 ma, respectively, leading to a total DC power consumption of 25.6 mw. III. 135-GHZ MIXER The schematic of a mixer developed in this work is shown in Fig. 5. The mixer, which is operating in a fundamental mode, is basically based on a Gilbert Cell. However, it is slightly different from the conventional Gilbert Cell in that the RF signal is injected to the mixer core through passive matching network, instead of a differential transistor pair. Such an approach will relax the voltage budget, and also help to reduce the DC power dissipation. Baluns are inserted at RF and LO input nodes to allow single-ended measurement, which is not explicitly shown in the schematic. The mixer core

32 DAEKEUN YOON et al : AN OSCILLATOR AND A MIXER FOR 140-GHZ HETERODYNE RECEIVER FRONT-END BASED ON Fig. 7. Photo of the measurement setup for the mixer. Fig. 6. Diagram of the measurement setup for the mixer. consists of two pairs of transistors that mix the RF and LO signals, which are both differentially injected. The transistors are operating almost in a passive mode, dissipating negligible DC power. The mixer core is followed by a differential emitter follower output buffer, which provides output impedance matching for IF node. The die photo of the fabricated mixer is shown in Fig. 5, which occupies an area of 800 880 mm 2 including the pads. The performance of the mixer was characterized with the measurement setup described in Fig. 6. The RF signal is provided by a Quinstar D-band tripler that is driven by an HP 83650B signal generator with frequency tunability. A Millitech D-band attenuator is inserted between the waveguide probe and the tripler to control the RF input power. The LO is supplied by a Gunn oscillator with a fixed frequency of 134 GHz. It is noted that both RF and LO signals are externally provided in a single-ended manner, but eventually converted into differential signals by an internally integrated baluns. The photo of the measurement setup is shown in Fig. 7. Fig. 8 plots the measured conversion gain of the mixer with RF frequency swept from 115 to 150 GHz. With an LO power fixed at 7 dbm, a peak conversion gain of 3.6 db was obtained around 135 GHz. A deep observed at 134 GHz marks the point that corresponds to IF frequency of 0. The linearity of the mixer is shown in Fig. 8, where the conversion gain and the output power are plotted as a function of the RF input power Fig. 8. Measured conversion gain of the mixer, Measured linearity characteristics of the mixer. that was varied from -33 dbm to -15 dbm with LO power fixed at 7 dbm. RF and LO frequencies are 136 and 134 GHz, respectively. Based on the plot, 1-dB compression point (P 1dB ) is estimated to be around -22 dbm. The supply voltage for the mixer core and buffer are 2 V and 1.5 V, respectively. The buffer draws 2 ma while the current through the mixer core is negligibly small, leading to a total DC power consumption of 3 mw.

JOURNAL OF SEMICONDUCTOR TECHNOLOGY AND SCIENCE, VOL.15, NO.1, FEBRUARY, 2015 33 IV. CONCLUSIONS An oscillator oscillating at 123 GHz and a mixer operating around 135 GHz have been developed based on IHP 0.13-mm SiGe HBT technology in this work. It is expected that the integration of these circuits would lead to a D-band heterodyne receiver, which can be applied to various applications including broadband communication and imaging. [6] B. Heinemann, R. Barth, D. Bolze, J. Drews, G. G. Fischer, A. Fox, O. Fursenko, T. Grabolla, U. Haak, D. Knoll, R. Kurps, M. Lisker, S. Marschmeyer, Ru, x, H. cker, D. Schmidt, J. Schmidt, M. A. Schubert, B. Tillack, C. Wipf, D. Wolansky, and Y. Yamamoto, "SiGe HBT technology with ft/fmax of 300GHz/500GHz and 2.0 ps CML gate delay," in IEEE International Electron Devices Meeting, pp. 30.5.1-30.5.4, 2010. ACKNOWLEDGMENTS This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (2012R1A2A1A01005584) REFERENCES [1] J.-S. Rieh, B. Jagannathan, D. R. Greenberg, M. Meghelli, A. Rylyakov, F. Guarin, Zhijian Yang, D. C. Ahlgren, G. Freeman, P. Cottrell, and D. Harame, "SiGe heterojunction bipolar transistors and circuits toward terahertz communication applications," IEEE Transactions on Microwave Theory and Techniques, vol. 52, pp. 2390-2408, 2004. [2] D. Yoon and J.-S. Rieh, "A 200-GHz Heterodyne Image Receiver with an Integrated VCO in a SiGe BiCMOS Technology," to appear in IEEE Microwave and Wireless Components Letters, 2014. [3] B. Thomas, A. Maestrini, J. Gill, C. Lee, R. Lin, I. Mehdi, and P. de Maagt, "A Broadband 835-900- GHz Fundamental Balanced Mixer Based on Monolithic GaAs Membrane Schottky Diodes," IEEE Transactions on Microwave Theory and Techniques, vol. 58, pp. 1917-1924, 2010. [4] Z. Xu, Q. J. Gu, Y.-C. Wu, A. Tang, Y.-L. Lin, H.- H. Chen, C. Jou, and M. C. F. Chang, "D-band CMOS transmitter and receiver for multi-gigabit/sec wireless data link," in IEEE Custom Integrated Circuits Conference, pp. 1-4, 2010. [5] E. Laskin, P. Chevalier, B. Sautreuil, and S. P. Voinigescu, "A 140-GHz double-sideband transceiver with amplitude and frequency modulation operating over a few meters," in IEEE Bipolar/BiCMOS Circuits and Technology Meeting, pp. 178-181, 2009. Daekeun Yoon received his B.S. degree in the department of electrical engineering from Korea University, Korea, in 2006. He is currently working toward his Ph.D. degree in the department of electrical engineering from Korea University, Korea. His primary research interests concern high frequency communication system and terahertz imaging system. Kiryong Song received his B.S. degree in electronic engineering from Korea University in 2012. He is currently pursuing the Ph.D. degree in the School of Electrical Engineering, Korea University. His major research interest lies in the design of Si-based mm-wave oscillators and mixers for high speed wireless communication and imaging systems. Mehmet Kaynak received his B.S degree from Electronics and Communication Engineering Department of Istanbul Technical University (ITU) in 2004, took the M.S degree from Microelectronic program of Sabanci University, Istanbul, Turkey in 2006 and received the PhD degree from Technical University of Berlin, Berlin Germany in 2014. He joined the technology group of IHP Microelectronics, Frankfurt (Oder), Germany in 2008. He is currently working on development and integration of embedded MEMS technologies and leading the MEMS group at IHP. Dr. Kaynak has received the young scientist award of Leibniz institute for the year of 2014.

34 DAEKEUN YOON et al : AN OSCILLATOR AND A MIXER FOR 140-GHZ HETERODYNE RECEIVER FRONT-END BASED ON Bernd Tillack received the PhD degree from the University HalleMerseburg in 1980. In 1981 he joined the IHP Frankfurt (Oder), Germany, as a staff member of the process technology. He had been the project leader of different IHP Si/SiGe technology projects. His research interests include SiGe BiCMOS technology development following the More than Moore strategy for embedded system applications. Since 2004 he is in charge of the Si/SiGe process and device technology in the IHP. In 2008 he got a professorship for Si based high frequency technologies at the Berlin Institute of Technology (TU Berlin). Since September 2014 he is the scientific director of IHP. Jae-Sung Rieh received the B.S. and M.S. degrees in electronics engineering from Seoul National University, Seoul, Korea, in 1991 and 1995, respectively, and the Ph.D. degree in electrical engineering from the University of Michigan, Ann Arbor, MI, USA, in 1999. In 1999, he joined IBM Semiconductor R&D Center, where he worked on SiGe HBT technologies. Since 2004, he has been with the School of Electrical Engineering, Korea University, Seoul, Korea, where he is currently a Professor. His major interest lies in the Si-based RF devices and their application to mm-wave and terahertz circuits. Dr. Rieh is a recipient of 2004 IBM Faculty Award and a corecipient of 2002 and 2006 IEEE EDS George E. Smith Awards and 2013 IEEE Microwave and Wireless Component Letters Tatsuo Itoh Best Paper Award. He served as an Associate Editor of the IEEE Microwave and Wireless Components Letters and is currently serving as an Associate Editor of the IEEE Transactions on Microwave Theory and Techniques.