Project C04 - Silicon Integrated Transceiver Components for Multi-Color
Imaging and Mobile CW Spectroscopy

Principal Investigator: Prof. Dr. Ullrich Pfeiffer

Achieved Results in the 1st Phase

The 1st phase of C04 addressed the fundamental bandwidth, output power and sensitivity limitations of integrated continuous-wave transmitters and receivers, resolving various issues related to the second research sub-question (Circuits). Fig. 1 summarizes the progress of C04. The central aim of the 1st phase was to extend the multi-color concept toward gapless spectral coverage of a whole decade of bandwidth with a dynamic range larger than 50 dB (0.15-1.5 THz). Achieving this aim required substantial progress in sub-harmonic THz front-end design, circuit-antenna co-integration, and the design of broadband on on-chip frequency multiplier-chains. Table 1 highlights the breakthroughs achieved in these fields within C04 and compares them to the state of the art prior to MARIE. By using novel methods for efficient harmonic signal generation, we achieved world records [C] and a four times improvement of the output power for silicon-integrated single-element THz sources around 450 GHz. Moreover, we have increased the bandwidth of on-chip frequency multiplier-chains by a factor of two, while at the same time increasing the maximum output power by a factor of ten around 300 GHz. Although we expect further progress regarding circuit design methods and device technology to be necessary for realizing remote spectroscopy in the whole THz band, the herein achieved component-level advances now enable us to build bistatic silicon-based THz spectroscopy systems for the frequency range between 0.15-1.5 THz. Addressing the first research sub-question (Multi-color spectroscopy systems), we will present an integrated multi-color spectrometer chip-set continuously covering this frequency range with a (simulated) dynamic range larger than 75 dB at the end of the 1st phase. However, several questions remain still unsolved. With the system of the 1st phase relying on separated Tx and Rx chips and thus bistatic set-ups, major system-integration challenges for the realization of mobile remote spectroscopy systems operating in reflection-mode lie ahead of us. These will be the research focus of C04’s 2nd phase. The key results and methods of the 1st phase are summarized below.

Table 1

High-power harmonic SiGe-HBT sources

With the proposed research applying to the device operation region exceeding fmax, C04 investigated novel methods to maximize the harmonic extraction efficiency of harmonic generators (WP2). It was found in C04 that appropriate harmonic feedback of SiGe-HBT devices configured in a balanced common-collector doubler topology can simultaneously offer large harmonic power and bandwidth if a circuit-antenna codesign approach is followed. Based on this finding, two harmonic radiators were designed and fabricated. First, a free-running narrowband oscillator-doubler radiation source with up to -6.3 dBm output power and 0.14% DC-to-RF efficiency at 430 GHz was demonstrated in 0.13-µm SiGe-HBT technology [C]. To extend the concept toward the coherent wideband systems targeted in C04, a multiplier-chain-based doubler source exploiting differential antenna-doubler co-integration to achieve a broadband optimum antenna impedance profile was developed in 0.13-µm SiGe-HBT technology. Here, the doubler circuitry is placed within the antenna layout to avoid additional bandwidth-limiting tuning elements in the doubler output network. A radiated power of -3.9 dBm with a 3-dB bandwidth spanning from 438 GHz to 489 GHz was demonstrated.

Broadband SiGe-HBT multiplier-chains

A leap in on-chip driving circuit bandwidth is necessary to enable gapless spectral coverage with the multi-color approach, which motivated our research in novel multiplier-chain architectures in C04 (WP2). We achieved a record 3-dB bandwidth for on-chip multiplier-chains by exploiting broadband optimization of phase relations between the transconductance pair and the switching quad in three cascaded Gilbert-cell doublers [F]. The measured 3-dB bandwidth spans between 210-290 GHz (32%), and the measured output power is -7.7 dBm, while the power consumption is 237 mW. During the 1st phase we identified that complex parasitic harmonic content of conventional on-chip multiplier chains may severely impair multi-color spectrometers due to resulting intermodulation distortions. Thus, we investigated novel frequency-tripler-based multiplier-chains with dedicated harmonic filters between the multiplication stages. The filters exploit the odd and even symmetry of differential circuits for wideband all-pass filtering of parasitic harmonic content by using tightly coupled line sections. This was used for the synthesis of a new class of compact low-loss on-chip filters. An x9 multiplier-chain with cascaded triplers, amplifiers, filters, and broadband interstage matching is currently fabricated in a high-speed 0.13-µm SiGe-HBT technology with an fmax of 650 GHz serving as a basis for the final multi-color demonstrator. Simulations show a 3-dB bandwidth spanning 247-328 GHz (28%), a peak output power of 10 dBm, and a spurious-free dynamic range between 25 dB and 50 dB in the entire passband.

Integrated multi-color spectrometer

Different system topologies were studied for the final multi-color spectrometer (WP1). Despite the advances in circuit bandwidth, a single multiplier-chain is not capable of providing gapless frequency coverage. Notably, an odd- and even-mode harmonic generator, e.g., a single-ended driven non-linear device, would require a relative bandwidth of at least 66% for continuous spectral coverage. Thus, C04 utilized two parallel frequency multiplier paths with different multiplication factors to close the covered spectrum by harmonic interleaving in both the receiver and the transmitter. The two multiplier-chain paths feed separate harmonic generators or sub-harmonic mixers. The interleaved harmonic content is then radiated orthogonally with dual-polarized on-chip antennas. Our simulations indicate that it should be technically feasible to cover the entire frequency range between 0.15-1.5 THz with a dynamic range larger than 70 dB (when referred to a 1-Hz bandwidth) without any gaps. The system is currently fabricated in a high-speed 0.13‑µm SiGe-HBT technology with an fmax of 650 GHz. Moreover, low-cost incoherent spectrometers that exploit the angular sampling properties of CMOS THz cameras with dispersive optics have been investigated in C04 [H]. Such systems are promising for broadband transmission-mode spectroscopy in static laboratory set-ups, but because of their immobility and complex optics, this approach will not be pursued in the 2nd phase.



[1]           H. Rücker, and B. Heinemann, “High-performance SiGe HBTs for next generation BiCMOS technology,” Semiconductor Science and Technology, Oct. 2018.

[2]           F. Golcuk, O. D. Gurbuz, and G. M. Rebeiz, "A 0.39–0.44 THz 2x4 Amplifier-Quadrupler Array With Peak EIRP of 3–4 dBm," IEEE Transactions on Microwave Theory and Techniques, Dec. 2013.

[3]           Z. Hu, M. Kaynak, and R. Han, "High-Power Radiation at 1 THz in Silicon: A Fully Scalable Array Using a Multi-Functional Radiating Mesh Structure," IEEE Journal of Solid-State Circuits, May 2018.

[4]           K. Guo, Y. Zhang, and P. Reynaert, "A 0.53-THz Subharmonic Injection-Locked Phased Array With 63-µW Radiated Power in 40-nm CMOS," IEEE Journal of Solid-State Circuits, Feb. 2019.

[5]           K. Schmalz, N. Rothbart, P. F. -. Neumaier, J. Borngräber, H. Hübers, and D. Kissinger, "Gas Spectroscopy System for Breath Analysis at mm-wave/THz Using SiGe BiCMOS Circuits," IEEE Transactions on Microwave Theory and Techniques, May 2017.

[6]           C. Wang and R. Han, "Dual-Terahertz-Comb Spectrometer on CMOS for Rapid, Wide-Range Gas Detection With Absolute Specificity," IEEE Journal of Solid-State Circuits, Dec. 2017.

[7]           B. Jamali and A. Babakhani, "A Fully Integrated 50–280-GHz Frequency Comb Detector for Coherent Broadband Sensing," IEEE Transactions on Terahertz Science and Technology, Nov. 2019

Project-related publications by participating researchers

a) Peer-reviewed publications and books

[A]           P. Hillger, J. Grzyb, R. Jain, and U. R. Pfeiffer, “Terahertz Imaging and Sensing Applications With Silicon-Based Technologies“, IEEE Transactions on Terahertz Science and Technology, Jan. 2019 – Most popular IEEE Transactions on Terahertz Science article since its appearance.

[B]           K. Statnikov, J. Grzyb, B. Heinemann, and U. R. Pfeiffer, "160-GHz to 1-THz Multi-Color Active Imaging With a Lens-Coupled SiGe HBT Chip-Set," IEEE Transactions on Microwave Theory and Techniques, Feb. 2015.

[C]          P. Hillger, J. Grzyb, S. Malz, B. Heinemann, and U. R. Pfeiffer, “A lens-integrated 430 GHz SiGe HBT source with up to -6.3 dBm radiated power”, in IEEE Radio Frequency Integrated Circuits Symposium (RFIC), Honolulu, 4-6 June, 2017.

[D]           N. Sarmah, B. Heinemann, and U. R. Pfeiffer, "235–275 GHz (x16) frequency multiplier chains with up to 0 dBm peak output power and low DC power consumption," in 2014 IEEE Radio Frequency Integrated Circuits Symposium (RFIC), Tampa, 2014.

[E]           E. Öjefors, B. Heinemann, and U. R. Pfeiffer, "Active 220- and 325-GHz Frequency Multiplier Chains in an SiGe HBT Technology," IEEE Transactions on Microwave Theory and Techniques, May 2011.

[F]           T. Bücher, S. Malz, K. Aufinger, and U. R. Pfeiffer, "A 210-291-GHz (8x) Frequency Multiplier Chain With Low Power Consumption in 0.13-μm SiGe," IEEE Microwave and Wireless Components Letters, April 2020.

[G]       P. Hillger, J. Grzyb, R. Lachner, and U. Pfeiffer, "An antenna-coupled 0.49 THz SiGe HBT source for active illumination in terahertz imaging applications," in 2015 10th European Microwave Integrated Circuits Conference (EuMIC), Paris, 2015.

[H]          D. Headland, P. Hillger, R. Zatta, and U. R. Pfeiffer, “Terahertz spectroscope using CMOS camera and dispersive optics”, IEEE Transactions on Terahertz Science and Technology, accepted in June 2020.

[I]            P. Hillger, M. van Delden, U. S. Miriya Thanthrige, A. Mostafa Ahmed, J. Wittemeier, K. Arzi, M. Andree, B. Sievert, W. Prost, A. Rennings, D. Erni, T. Musch, N. Weimann, A. Sezgin, N. Pohl, and U. R. Pfeiffer, “Toward Mobile Integrated Electronic Systems at THz Frequencies”, Journal of Infrared, Millimeter, and Terahertz Waves, June, 2020 Joined MARIE journal publication coordinated by the IHCT Lab.

[J]            R. Jain, P. Hillger, J. Grzyb, and U. R. Pfeiffer, "29.1 A 0.42THz 9.2dBm 64-Pixel Source-Array SoC with Spatial Modulation Diversity for Computational Terahertz Imaging," in 2020 IEEE International Solid- State Circuits Conference (ISSCC), San Francisco, 2020.