Publications

International Journal Articles

1. W. Choi and K. K. O, “Enabling Applications of Electromagnetic Waves at 0.3–1.0 THz Using Silicon Electronic Integrated Circuits,” ACS Photonics, Mar. 2024, doi: 10.1021/acsphotonics.3c01129.

2. P. R. Byreddy, Y. Zhu, S. Ghosh, H. S. Bakshi, W. S. Portillo, J. P. Van Marter, K. K. O, W. Choi, "Array of 296-GHz CMOS Concurrent Transceiver Pixels With Phase and Amplitude Extraction Circuits for Improving Reflection-Mode Imaging Resolution," in IEEE Transactions on Terahertz Science and Technology, vol. 14, no. 2, pp. 216-227, March 2024, doi: 10.1109/TTHZ.2024.3350515.

3. K. K. O, W. Choi, and R. Han, “Perspective on active submillimeter electromagnetic wave imaging using CMOS integrated circuits technologies,” Journal of Applied Physics, vol. 133, no. 15, p. 150903, Apr. 2023, doi: 10.1063/5.0143622.

4. P. R. Byreddy, W. E. Sosa, Y. Zhu, Z. Chen, B. Pouya, W. Choi, and K. K. O, "Lens-less Short-Range Reflection-Mode Imaging at 275 GHz Using CMOS Concurrent Transceivers," in IEEE Sensors Letters, vol. 7, no. 2, pp. 1-4, Feb. 2023, Art no. 3500204, doi: 10.1109/LSENS.2023.3239804.

5. K. K. O, W. Choi, Y. Zhu and H. Guo, "CMOS Platform for Everyday Applications Using Sub-Millimeter Electromagnetic Waves," in IEEE Open Journal of the Solid-State Circuits Society, 2022, doi: 10.1109/OJSSCS.2022.3222121.

6. W. Raza, E. Abele, J. O'Hara, B. Sadr, P. LoPresti, A. Imran, W. Choi, I. Song, S. Altunc, O. Kegege, and S. Ekin, "Towards a Hybrid RF/Optical Lunar Communication System (LunarComm)," in IEEE Network, vol. 36, no. 6, pp. 76-83, November/December 2022, doi: 10.1109/MNET.103.2100419.

7. Y. Zhu, P. R. Byreddy, K. K. O, and W. Choi, "426-GHz Concurrent Transceiver Pixel in 65-nm CMOS for Active Imaging," in IEEE Transactions on Terahertz Science and Technology, vol. 12, no. 5, pp. 446-456, Sept. 2022, doi: 10.1109/TTHZ.2022.3183159.

8. Z. Chen, W. Choi and K. K. O, "300-GHz Double-Balanced Up-Converter Using Asymmetric MOS Varactors in 65-nm CMOS," in IEEE Journal of Solid-State Circuits, vol. 57, no. 8, pp. 2336-2347, Aug. 2022, doi: 10.1109/JSSC.2022.3171545.

9. A. Kachroo, C. A. Thornton, M. A. R. Sarker, W. Choi, H. Bai, I. Song, J. O'Hara, and S. Ekin ,  "Emulating UAV Motion by Utilizing Robotic Arm for mmWave Wireless Channel Characterization," in IEEE Transactions on Antennas and Propagation, vol. 69, no. 10, pp. 6691-6701, Oct. 2021, doi: 10.1109/TAP.2021.3069484.

10. H. S. Bakshi, S. Dong, I. Momson, D. Chacon, Z. Chen, W. Choi, A. J. Blanchard, and K. K. O, "180-GHz Broadside Radiation Bond-Wire Antenna for Short-Range Wireless Communication," in IEEE Transactions on Components, Packaging and Manufacturing Technology, vol. 11, no. 3, pp. 530-532, March 2021, doi: 10.1109/TCPMT.2021.3053558.

11. S. Dong, I. Momson, S. Kshattry, P. Yelleswarapu, W. Choi and K. K. O, "A 10-Gb/s 180-GHz Phase-Locked-Loop Minimum Shift Keying Receiver," in IEEE Journal of Solid-State Circuits,  vol. 56, no. 3, pp. 681-693, March 2021, doi: 10.1109/JSSC.2020.3032972.

12. Q. Zhong, W. Choi and K. K. O, "Terahertz Even-Order Subharmonic Mixer Using Symmetric MOS Varactors," in IEEE Journal of Solid-State Circuits, vol. 56, no. 2, pp. 355-366, Feb. 2021, doi: 10.1109/JSSC.2020.3024177.

13. Z. Chen, W. Choi and K. K. O., "300-GHz 2nd-Order Subharmonic Upconversion Mixer Using Symmetric MOS Varactors in 65-nm CMOS," in IEEE Solid-State Circuits Letters, vol. 3, pp. 538-541, 2020, doi: 10.1109/LSSC.2020.3036804.

14. E. Guerrero, A. Polednik, M. Ecker, A. Joshi‐Imre, W. Choi, G. Gutierrez‐Heredia, W. E. Voit, J. Maeng, "Indium–Gallium–Zinc Oxide Schottky Diodes Operating across the Glass Transition of Stimuli‐Responsive Polymers," in Adv. Electron. Mater. 2020, 1901210. doi: 10.1002/aelm.201901210

15. Z. Chen, Z. Chen, W. Choi and K. K.O., "610-GHz Fourth Harmonic Signal Reactively Generated in a CMOS Voltage Controlled Oscillator Using Differentially Pumped Varactors," in IEEE Solid-State Circuits Letters, vol. 3, pp. 46-49, 2020, doi: 10.1109/LSSC.2020.2978150.

16. H. S. Bakshi, P. R. Byreddy, K. K. O, A. Blanchard, M. Lee, E. Tuncer, W. Choi, "Low-Cost Packaging of 300 GHz Integrated Circuits With an On-Chip Patch Antenna," in IEEE Antennas and Wireless Propagation Letters, vol. 18, no. 11, pp. 2444-2448, Nov. 2019. doi: 10.1109/LAWP.2019.2943371 

17. Z. Chen, S. Dong, Z. Chen, W. Choi, S. Kshattry, I. Momson, Q. Zhong, K. K. O, "Generation of High Data Rate MSK-Modulated 180-GHz Signals," in IEEE Microwave and Wireless Components Letters, vol. 29, no. 11, pp. 757-760, Nov. 2019. doi: 10.1109/LMWC.2019.2940552

18. (invited) K. K. O, W. Choi, Q. Zhong, N. Sharma, Y. Zhang, R. Han, Z. Ahmad, D. Kim, S. Kshattry, I. R. Medvedev, D. J Larry, H. Nam, P. Raskin, I. Kim , “Opening Terahertz for Everyday Applications,” IEEE Communications Magazine, vol. 57, no. 8, pp. 70–76, Aug. 2019. [doi:10.1109/MCOM.2019.1800909]

19. (review) J. F. O’Hara, S. Ekin, W. Choi, and I. Song, “A Perspective on Terahertz Next-Generation Wireless Communications,” Technologies, vol. 7, no. 2, p. 43, Jun. 2019.  [doi:10.3390/technologies7020043]

20. W. Choi, P. R. Byreddy, Z. Chen, A. J. Chen, A. J. Newman, and K. K. O, “450×580 µm2 Pixel incorporating TX and coherent RX in CMOS for mm-wave active imaging using a single reflector,” IET Electron. Lett., vol. 54, no. 16, pp. 982–984, 2018. [doi:10.1049/el.2018.1086]

21. D. Shim, W. Choi, J. W. Lee, and K. K. O, “Self-Dynamic and Static Biasing for Output Power and Efficiency Enhancement of Complementary Antiparallel Diode Pair Frequency Tripler,” IEEE Microw. Wireless Compon. Lett., vol. 27, no. 12, pp. 1110–1112, Dec. 2017.  doi: 10.1109/LMWC.2017.2757845

22. S. Kshattry, W. Choi, C. Yu, and K. K. O, “Compact Diode Connected MOSFET Detector for On-Chip Millimeter-Wave Voltage Measurements,” IEEE Microw. Wireless Compon. Lett., vol. 26, no. 5, pp. 349–351, May 2016. doi: 10.1109/LMWC.2016.2548365

23. J. Zhang, N. Sharma, W. Choi, D. Shim, Q. Zhong, and K. K. O, “85-to-127 GHz CMOS Signal Generation Using a Quadrature VCO With Passive Coupling and Broadband Harmonic Combining for Rotational Spectroscopy,” IEEE J. Solid-State Circ., vol. 50, no. 6, pp. 1361–1371, June 2015. doi: 10.1109/JSSC.2015.2416312

24. M. Seo, H. Lee, J. Gu, H. Kim, J. Ham, W. Choi, Y. Yun, K. K. O, and Y. Yang, “High-Efficiency Power Amplifier Using an Active Second-Harmonic Injection Technique Under Optimized Third-Harmonic Termination,” IEEE Trans. Circ. Syst. II: Express Briefs, vol. 61, no. 8, pp. 549–553, Aug. 2014. doi: 10.1109/TCSII.2014.2327382

25. C. Lee, W. Choi, R. Han, H. Shichijo, and K. K. O, “Broadband Root-Mean-Square Detector in CMOS for On-Chip Measurements of Millimeter-Wave Voltages,” IEEE Electron. Device Lett., vol. 33, no. 6, pp. 752 –754, Jun. 2012. doi: 10.1109/LED.2012.2190258

26. J. Kim, W. Choi, A. S. Quraishi, and Y. Kwon, "Millimeter-wave High-Linear CMOS Low-Noise Amplifier Using Multiple-Gate Transistors," ETRI Journal, Vol. 33, No. 3, pp. 462-465, Jun. 2011.  doi: 10.4218/etrij.11.0210.0235 

27. W. Choi, K. Park, Y. Kim, K. Kim, and Y. Kwon, "A V-band switched Beam-Forming Antenna Module Using Absorptive Switch Integrated with 4x4 Butler Matrix in 0.13-μm CMOS," IEEE Trans. Microw. Theory Tech., Vol. 58, No. 12, pp. 4052-4059, Dec. 2010. doi: 10.1109/TMTT.2010.2086472 

28. W. Choi, K. Kim, and Y. Kwon, "Ultra-Low-Power Series-Feedback Frequency Divider using 0.15-μm GaAs pHEMT’s at W-Band," IEEE Microw. Wireless Compon. Lett., Vol. 20, No. 11, pp. 634-636, Nov. 2010. doi: 10.1109/LMWC.2010.2067207

29. W. Choi, G. Jung, J. Kim, and Y. Kwon, “Scalable Small-Signal Modeling of RF CMOS FET Based on 3-D EM-Based Extraction of Parasitic Effects and Its Application to Millimeter-Wave Amplifier Design,” IEEE Trans. Microw. Theory Tech., vol. 57, No. 12, pp. 3345-3353., Dec. 2009. doi: 10.1109/TMTT.2009.2034067

30. S. Song, Y. Kim, W. Choi, Y. Kwon, and K.-S. Seo, “A V-Band Parallel-Feedback Oscillator with a Micromachined Cavity Integrated on a Thin-Film Substrate,” IEEE Microw. Wireless Compon. Lett., vol. 19, no. 2, pp. 107-109, Feb. 2009. doi: 10.1109/LMWC.2008.2011334 

31. J. Park, E. S. Shim, W. Choi, Y. Kim, Y. Kwon, and D. Cho, “A Non-Contact-Type RF MEMS Switch for 24-GHz Radar Applications,” IEEE J. Microelectromech. Sys., vol. 18, no. 1, pp. 163–173, Feb. 2009. doi: 10.1109/JMEMS.2008.2011124 

32. C. Lee, W. Choi, J. Kim, and Y. Kwon, “A 77 GHz 3-stage low noise amplifier with cascode structure utilizing positive feedback network using 0.13 μm CMOS process,” J. Semic. Tech. and Sci., vol. 8, no. 4, pp. 289–294, 2008. doi: 10.5573/JSTS.2008.8.4.289 

33. J. Jeong, S.W. Kim, W. Choi, K.-S. Seo, and Y. Kwon, “A distributed amplifier with 12.5-dB gain and 82.5-GHz bandwidth using 0.1 μm GaAs metamorphic HEMTs,” Microw. Optical Tech. Lett., vol. 49, No. 11, pp. 2873-2875, Nov. 2007. doi: 10.1002/mop.22844

34. W. Choi and Y. Kwon, “Phase Locked Loop Sub-Circuits for 24 GHz Signal Generation in 0.5 μm SiGe HBT technology,” J. Semic. Tech. Sci., vol. 7, no. 4, p. 281, 2007. doi: 10.5573/JSTS.2007.7.4.281 

35. H. Kim, W. Choi, and Y. Kwon, “V-band MMIC oscillator array,” IET Electron. Lett., vol. 41, No. 8, pp. 481-483, Apr. 2005. doi: 10.1049/el:20050082

36. J. Jeong, S. Kim, W. Choi, H. Noh, K. Lee, K.-S. Seo, and Y. Kwon, “W-band divide-by-3 frequency divider using 0.1 μm InAlAs/InGaAs metamorphic HEMT technology,” IET Electron. Lett., vol. 41, No. 18, pp. 1005-1006, Sep. 2005.  doi: 10.1049/el:20052191 

37. C.-W. Baek, S. Song, J.-H. Park, S. Lee, J.-M. Kim, W. Choi, Changyul-Cheon, Y.-K. Kim, and Y. Kwon, “A V-band micromachined 2-D beam-steering antenna driven by magnetic force with polymer-based hinges,” IEEE Trans. Microw. Theory Tech., vol. 51, no. 1, pp. 325–331, Jan. 2003. doi: 10.1109/TMTT.2002.806516 

38. J.-H. Park, H.-T. Kim, W. Choi, Y. Kwon, and Y.-K. Kim, “V-band reflection-type phase shifters using micromachined CPW coupler and RF switches,” IEEE J. Microelectromech. Sys., vol. 11, no. 6, pp. 808–814, Dec. 2002. doi: 10.1109/JMEMS.2002.805042 

International Conference Papers

1. J. Hu, J. Stine, W. Choi, and E. Dyke, “Research Experiences for Teachers on Chip Design,” in 2024 IEEE International Symposium on Circuits and Systems (ISCAS), May 2024, pp. 1–5. doi: 10.1109/ISCAS58744.2024.10558044.

2. S. Azmeen-ur-Rahman, M. O. Hasna, S. Ekin, and W. Choi, “Two-Port Characterization of Symmetric Varactors in 65-nm CMOS Process for Mixer Applications,” in 2023 IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS), Apr. 2023, pp. 1–4. doi: 10.1109/WMCS58822.2023.10194281.

3. H. Mehraban, W.-S. Park, H.-B. Jo, S.-M. Choi, D.-H. Kim, S.-K. Kim, J. Yun, T. Kim, W. Choi, "A W-Band Low-Noise Amplifier in 50-nm InP HEMT Technology," in 2023 IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS), Apr. 2023, pp. 1–4. doi: 10.1109/WMCS58822.2023.10194275.

4. K. Strecker, W. Choi, J. O’Hara, "A Wideband Millimeter-Wave Communication and Sensing Testbed for 75-500 GHz," in 2023 IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS), Apr. 2023, pp. 1–5. doi: 10.1109/WMCS58822.2023.10194272.

5. H. S. Cankurtaran, A. Kachroo, W. Choi, J. O'Hara, S. Yarkan, K. A. Qaraqe, M. O. Hasna, and S. Ekin, "Propeller Effects on mmWave UAV Channels: A Statistical and Empirical Modeling Study," 2022 IEEE International Black Sea Conference on Communications and Networking (BlackSeaCom), 2022, pp. 30-35, doi: 10.1109/BlackSeaCom54372.2022.9858315.

6. M. T. Anas, S. Azmeen-ur-Rahman and W. Choi, "A 410-GHz Detector using AC-coupled Substrate-Integrated Waveguide Slot Antenna in CMOS," 2022 IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS), 2022, pp. 1-5, doi: 10.1109/WMCS55582.2022.9866391.

7. Y. Zhu, P. R. Byreddy, S. Dong, K. K. O and W. Choi, "A 430GHz CMOS Concurrent Transceiver Pixel Array for High Angular Resolution Reflection-Mode Active Imaging," 2022 IEEE International Solid-State Circuits Conference (ISSCC), 2022, pp. 1-3, doi: 10.1109/ISSCC42614.2022.9731698.

8. C. Thornton, A. Kachroo, H. Bai, S. Ekin, and W. Choi, "De-embedding Motion Artifacts from Robotic Arm Assisted Propagation Measurements," 2021 IEEE Texas Symposium on Wireless and Microwave Circuits and Systems (WMCS), 2021, pp. 1-6, doi: 10.1109/WMCS52222.2021.9493296.

9. Z. Chen, W. Choi and K. K. O, "23.1 270-to-300GHz Double-Balanced Parametric Upconverter Using Asymmetric MOS Varactors and a Power-Splitting-Transformer Hybrid in 65nm CMOS," 2021 IEEE International Solid-State Circuits Conference (ISSCC), 2021, pp. 324-326, doi: 10.1109/ISSCC42613.2021.9365953.

10. P. R. Byreddy, Y. Zhu, H. S. Bakshi, K. K. O and W. Choi, "287-GHz CMOS Transceiver Pixel Array in a QFN Package for Active Imaging," 2020 IEEE Asian Solid-State Circuits Conference (A-SSCC), 2020, pp. 1-4, doi: 10.1109/A-SSCC48613.2020.9336111.

11. I. Momson, S. Dong, P. Yelleswarapu, W. Choi and K. K. O, "315-GHz Self-Synchronizing Minimum Shift Keying Receiver in 65-nm CMOS," 2020 IEEE Symposium on VLSI Circuits, Honolulu, HI, USA, 2020, pp. 1-2, doi: 10.1109/VLSICircuits18222.2020.9162779.

12. N. Sharma, Q. Zhong, W. Choi, J. Zhang, Z. Chen, Z. Ahmad, I. R. Medvedev, D. J. Lary, H.-J. Nam, P. Raskin, I. Kim, K. K. O., "Complementary metal oxide semiconductor integrated circuits for rotational spectroscopy," Proc. SPIE 11390, Next-Generation Spectroscopic Technologies XIII, 113900K (19 May 2020); https://doi.org/10.1117/12.2557169

13. S. Dong, I. Momson, S. Kshattry, P. Yelleswarapu, W. Choi and K. K. O, "A Wideband 180-GHz Phase-Locked-Loop Based MSK Receiver," 2020 IEEE Custom Integrated Circuits Conference (CICC), Boston, MA, USA, 2020, pp. 1-4, doi: 10.1109/CICC48029.2020.9075939.

14. (invited) S. Kshattry, C.-K. Yu, C.-L. Wu, Y. Yun, C. Lee, C.-Y. Cha, W. Choi, N. Preisler, K. K. O, "High-Impedance, Broadband and Compact RMS Detectors for On-Chip Measurements of Millimeter Wave Voltages for Built-In Self-Testing and Debugging," 2020 IEEE 20th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF), San Antonio, TX, USA, 2020, pp. 22-25, doi: 10.1109/SIRF46766.2020.9040184.

15. (invited) W. Choi, Y. Zhu, P. R. Byreddy, Z. Chen, Z. Chen, A. J. Newman and K. K. O, "CMOS Transceiver Pixels for Terahertz Imaging," 2019 IEEE International Symposium on Radio-Frequency Integrated Technology (RFIT), Aug. 2019, Nanjing, China. doi: 10.1109/RFIT.2019.8929129

16. Y. Zhu, P. R. Byreddy, K. K. O, and W. Choi, “426-GHz Imaging Pixel Integrating a Transmitter and a Coherent Receiver with an Area of 380×470μm2 in 65-nm CMOS,” 2019 IEEE Symp. VLSI Circ. (VLSIC), June 2019, pp. C18–C19. [doi:10.23919/VLSIC.2019.8778039]

17. (invited) W. Choi, D. Kim, Z. Ahmad, P Byreddy, Y. Zhu, J. Newman, and K. K. O, “CMOS Circuits for THz Imaging,” in Micro- and Nanotechnology Sensors, Systems, and Applications XI (SPIE DCS), 2019, vol. 10982, p. 1098231. [doi:10.1117/12.2518654]

18. Q. Zhong, W. Choi, K. K. O, “Terahertz RF Front‐End Employing Even‐Order Subharmonic MOS Symmetric Varactor Mixers in 65‐nm CMOS for Hydration Measurements at 560 GHz,” 2018 IEEE Symp. VLSI Circ. (VLSIC), June 2018. [doi:10.1109/VLSIC.2018.8502297]

19. Q. Zhong, Z. Chen, N. Sharma, S. Kshattry, W. Choi, and K. O. Kenneth, “300-GHz CMOS QPSK transmitter for 30-Gbps dielectric waveguide communication,” IEEE CICC 2018, Apr. 2018, pp. 1–4. [doi:10.1109/CICC.2018.8357053]

20. (invited) Q. Zhong, W. Choi, ..., and K. K. O, “CMOS Terahertz Receivers,” IEEE CICC 2018, Apr. 2018. [doi:10.1109/CICC.2018.8357054]

21. (invited) K. K. O, Z. Ahmad, W. Choi et al., “(Keynote) Devices in CMOS for Terahertz Circuits and Systems,” Electrochemical Society Trans., vol. 80, no. 4, pp. 3–15, Aug. 2017. doi: 10.1149/08004.0003ecst

22. (invited) Z. Ahmad, W. Choi, ..., and K. K. O, “Devices and Circuits in CMOS for THz Applications,” IEDM 2016, Dec. 2016. doi: 10.1109/IEDM.2016.7838509 

23. N. Sharma, Q. Zhong, Z. Chen, W. Choi, J. P. McMillan, C. F. Neese, R. Schueler, I. Medvedev, F. De Lucia, K. K. O, “200-280GHz CMOS RF Front-End of Transmitter for Rotational Spectroscopy,” 2016 Symp. VLSI Tech., June 2016. doi: 10.1109/VLSIT.2016.7573400 

24. W. Choi, and K. K. O, “Kelvin Inductance and Resistance Measurements Using an AC Source and DC Voltmeters,” IMS 2016, May 2016. doi: 10.1109/MWSYM.2016.7540355 

25. Q. Zhong, W. Choi, N. Sharma, Z. Ahmad, J. P. McMillan, C. F. Neese, F. C. De Lucia, and K. K. O, “225–280GHz Receiver for Rotational Spectroscopy,” RFIC 2016, May 2016. doi: 10.1109/RFIC.2016.7508310 

26. N. Sharma, W. Choi, K. K. O, “160–310GHz Frequency Doubler in 65-nm CMOS with 3-dBm Peak Output Power for Rotational Spectroscopy,” RFIC 2016, May 2016. doi: 10.1109/RFIC.2016.7508282 

27. Q. Zhong, W. Choi, C. Miller, R. Henderson, K. K. O, “A 210-to-305GHz CMOS Receiver for Rotational Spectroscopy”, 2016 ISSCC, Feb. 2016. doi: 10.1109/ISSCC.2016.7418089 

28. (invited) Z. Ahmad, D.-Y. Kim, R. Han, W. Choi, and K. K. O, “Terahertz imaging circuits in CMOS,” Asia-Pacific Microw. Conf. (APMC), Dec. 2015. doi: 10.1109/APMC.2015.7411757 

29. W. Choi, Z. Ahmad, A. Jha, J.-Y. Lee, I. Kim, and K. K. O, “410-GHz CMOS Imager Using a 4th Sub-harmonic Mixer with Effective NEP of 0.3 fW/Hz0.5 at 1-kHz Noise Bandwidth” 2015 Symp. VLSI Circ., Jun. 2015. doi: 10.1109/VLSIC.2015.7231299 

30. T. Xi, S. Huang, S. Guo, P. Gui, J. Zhang, W. Choi, D. Huang, K. O, "A new compact high-efficiency mmWave power amplifier in 65 nm CMOS process," 2015 IEEE MTT-S International Microwave Symposium, 2015, pp. 1-4.

31. S. Guo, T. Xi, P. Gui, J. Zhang, W. Choi, K. O, Y. Fan, D. Huang, R. Gu, and M. Morgan, “54 GHz CMOS LNAs with 3.6 dB NF and 28.2 dB gain using transformer feedback Gm-boosting technique,” 2104 ASSCC, pp. 185–188, Nov. 2014. doi: 10.1109/ASSCC.2014.7008891 

32. N. Sharma, J. Zhang, Q. Zhong, W. Choi, J. P. McMillan, C. F. Neese, F. C. De Lucia, and K. K. O., “85-to-127 GHz CMOS transmitter for rotational spectroscopy,” CICC 2014, Sept. 2014. doi: 10.1109/CICC.2014.6946140 

33. W. Choi, S. Nelson, D. Ferwalt, R. Mongia, H. Shichijo, K. K. O, “Three-harmonic Time-domain Load-pull Measurement System with the 40-GHz Maximum Third Order Harmonic Frequency for Nonlinear Device Characterization,” 82th Microw. Measurement Symp. (ARFTG), Nov. 2013. doi: 10.1109/ARFTG-2.2013.6737344 

34. W. Choi, D. Y. C. Lie, J. Lopez, D. Ma, R. Mongia, S. Nelson, K. K. O, S. Shichijo, M. Walker, R. Bondade, M. Song, “Wideband Class J High Efficiency Envelope Tracked Power Amplifiers,” 2013 GOMACTech Conf., Mar. 2013

35. Y. Park, Y. Kim, W. Choi, J. Woo, and Y. Kown, "X-to-K-band Broadband Watt-level Power Amplifier Using Stacked-FET Unit Cells," RFIC2011, June 2011. doi: 10.1109/RFIC.2011.5940620 

36. K. Park, W. Choi, Y. Kim, K. Kim, and Y. Kwon, “A V-band Switched Beam-Forming Network Using Absorptive SP4T Switch Integrated with 4x4 Butler Matrix in 0.13-μm CMOS,” IMS 2010, May 2010. doi: 10.1109/MWSYM.2010.5515849 

37. J. Kim, W. Choi, Y. Park, and Y. Kwon, “60 GHz broadband image rejection receiver using varactor tuning,” RFIC2010, pp. 381-384, May 2010. doi: 10.1109/RFIC.2010.5477351 

38. G. Jung, W. Choi, and Y. Kwon, “Scalable small-signal modeling of RF CMOS FET based on 3-D EM-based extraction of parasitic effects,” IMS 2009, pp. 873-876, June 2009. doi: 10.1109/MWSYM.2009.5165836 

39. S.-W. Kim, Y.-M. Koh, W. Choi, H.-T. Kim, Y. Kwon, and K. S. Seo, "W-band low-noise amplifier with 50 nm In0.8GaP/In0.4AlAs/In0.35GaAs metamorphic HEMT," Int. Conf. InP and Related Materials, May 2008. doi: 10.1109/ICIPRM.2008.4702951 

40. E. S. Shim, J. Park, W. Choi, Y. Kim, Y. Kwon, J. S. No, S. Nam, and D. Cho, “Hot-Switching Test of Non-Contact Type MEMS Switch,” IMS 2007, pp. 1809–1812, June 2007. doi: 10.1109/MWSYM.2007.380100 

41. K. Kim, W. Choi, S. Kim, G. Seol, K.-S. Seo, and Y. Kwon, “A 77 GHz Transceiver for Automotive Radar System Using a 120nm In0.4AlAs/In0.35GaAs Metamorphic HEMTs,” Comp. Semic. Integ. Circ. Symp. Dig., pp. 201-204, Nov. 2006. doi: 10.1109/CSICS.2006.319963 

42. S. Kim, W. Choi, D. Kim, J. Huh, K. Jang, Y. Kwon, and K.-S. Seo, "77GHz low noise sub block MMICs with 120 nm In0.4AlAs/In0.35GaAs metamorphic HEMTs," Eur. Microw. Integr. Circ. Conf. (EuMIC), pp. 103-106, Sep. 2006. doi: 10.1109/EMICC.2006.282761 

43. W. Choi, C. Cheon, and Y. Kwon, “A V-band MMIC Self Oscillating Mixer Active Integrated Antenna Using a Push-Pull Patch Antenna,” IMS 2006, pp. 630-633, June 2006. doi: 10.1109/MWSYM.2006.249692 

44. S. Song, S. Kim, J. Y. Lee, S. Lee, W. Choi, Y. Kwon, and K.-S. Seo, "Flip-Chip Mounted MMICs Technology using the Modified MCM-D Substrate for Low-Cost W-band Transceiver," IMS 2005, June 2005. doi: 10.1109/MWSYM.2005.1516838 

45. S. Kim, S. Song, W. Choi, S. Lee, Y. Kwon, and K.-S. Seo, "High Performance of W-band MMICs Using 60nm InGaAs HEMT Technology." Int. Conf. InP and Related Materials, pp. 20-23, 31 May-4 June 2004. doi: 10.1109/ICIPRM.2004.1442601 

46. H.-T. Kim, W. Choi, S. Lee, Y. Kwon, and C. Cheon, “A V-band MMIC Oscillator Array using Wide Band Microstrip Patch Antenna,” 2003 Asia-Pacific Microwave Conference (APMC), Nov. 2003.

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