Thomas Reed

THz MMICs based on InP HBT Technology

An indium-phosphide (InP) double-heterojunction bipolar transistor (DHBT) based suite of terahertz monolithic integrated circuits (TMICs) fabricated using 256nm InP DHBT transistors and a multipurpose three metal layer interconnect system is reported. The InP DHBT MMIC process is well suited for TMICs due to its high bandwidth (fmax = 808 GHz) and high breakdown voltage (BVCBo = 4V) and integrated 10-µm thick layer of BCB dielectric supporting both low-loss THz microstrip lines for LNA, PA, and VCO tuning networks, and high-density thin-film interconnects for compact digital and analog blocks. TMIC low noise and driver amplifiers, fixed and voltage controlled oscillators, dynamic frequency dividers, and double-balanced Gilbert cell mixers have been designed and fabricated. These results demonstrate the capability of 256nm InP DHBT technology to enable sophisticated single-chip heterodyne receivers and exciters for operation at THz frequencies.

40Gbit/s coherent optical receiver using a Costas loop

A highly integrated 40 Gbit/s coherent optical receiver is reported using a Costas loop as a homodyne optical phase locked loop (OPLL). A photonic IC, an electrical IC, and a hybrid loop filter are characterized, and the feedback loop system is fully analyzed to build a stable homodyne OPLL. All components are integrated on a single substrate within the compact size of 10 × 10mm(2), and a 1.1 GHz loop bandwidth and a 120 psloop delay are achieved. The binary phase-shift keying receiver exhibits error-free (BER<10(-12)) up to 35 Gbit/s and BER<10(-7) for 40 Gbit/s with no latency, and consumes less than 3 W power.

A 220 GHz InP HBT Solid-State Power Amplifier MMIC with 90mW POUT at 8.2dB Compressed Gain

A 220 GHz Solid State Power Amplifer MMIC is presented simultaneously demonstrating 90mW output power Pout and 8.2dB compressed gain. This 2-Stage, 8-Cell amplifier has 14.8 dB S21 gain at 220GHz, with small signal bandwidth from at least 190 to 240GHz. PDC is 4.46W. Amplifier cells were fabricated from a 250nm InP HBT technology, jointly with a substrate- shielded, thin-film microstrip wiring environment using BCB. The 90mW Pout is achieved by combining eight amplifier cascode cells. The use of two gain stages relaxes the RF source power demands, where only 13.6mW Pin is needed to achieve 90mW Pout. Over 10GHz bandwidth, at least 75mW Pout is observed from 210 to 220GHz.

A 180mW InP HBT Power Amplifier MMIC at 214 GHz

A solid state power amplifier MMIC is demonstrated with 180mW of saturated output power at 214GHz, from an unthinned die, and a small signal S21 gain of 22.0dB. 3-dB bandwidth extends from below 210GHz to 230GHz. PDC is 12.9W. PA Cell design uses a 250nm InP HBT process and a novel three-port tuning network. Three levels of on-wafer power combining in 5μm BCB microstrip are used to combine 16 PA cells in a power amplifier MMIC. The result is a 4x increase in output periphery versus the previous state-of-the-art for InP HBT power amplifier MMICs designed for 220GHz.

Development of a 220 GHz 50 W sheet beam travelling wave tube amplifier

We report on progress in developing a travelling wave tube amplifier with significant gain and power at 220 GHz. This paper provides an overview of the program, describing fabrication and test of slow-wave structures with bandwidths exceeding 50 GHz centered at 220 GHz, the production of a sheet electron beam, development of a solid state preamplifier delivering 50 mW to the tube with > 17 dB of gain and beam-wave simulation of the entire circuit leading to expected output powers of over 50 W. Two further papers from the group are also submitted to IVEC: from UC Davis describing the interaction structure fabrication and hot test, and from CPI describing the sheet electron beam, TWT design and beam - wave simulations. The tube is currently under test and results will be reported in this paper.

48.8 mW Multi-Cell InP HBT Amplifier with On-Wafer Power Combining at 220 GHz

We report 220 GHz Solid State Power Amplifier (SSPA) using a 250nm Indium Phosphide HBT technology. Amplifiers reported include designs having 2 and 4 power combined cells. The 4-cell amplifiers exhibited 10 dB small signal gain and 48.8 mW of output power with 4.5 dB gain at 220 GHz. These amplifiers have a 3-dB small signal bandwidth of greater than 48 GHz. A 5-µm thick BCB microstrip wiring environment with 4 levels of interconnects allowed for low-loss transmission lines, mm-wave tuning structures, and dense interconnects within each cell. The 2-cell amplifiers provide 10.9 dB small signal gain at 220 GHz with a 3-dB bandwidth of greater than 42 GHz and 26.3 mW of saturated output power at 208GHz.

A 1–20-GHz All-Digital InP HBT Optical Wavelength Synthesis IC

An integrated circuit (IC) for heterodyne optical phase locking in a 1-20-GHz offset range is hereby reported. The IC, implemented in a 500-nm InP HBT process, contains an emitter coupled logic digital single-sideband mixer to provide phase locking at a ± 20-GHz offset frequency, and a wideband phase-frequency detector designed to provide loop acquisition up to ±40-GHz initial frequency offset. The all-digital IC design has phase-frequency detection gain independent of IC process parameters or optical signal levels, and provides a wide offset locking range. A 100-ps delay decreases the overall loop delay, making wideband loop filter design possible. In addition, a medium-scale high-frequency logic design methodology is presented and fully discussed.

A 1–20 GHz InP HBT phase-lock-loop IC for optical wavelength synthesis

We report a PLL IC for locking, at a controlled frequency offset between 1 and 20 GHz, the optical phase and optical frequency of a slave semiconductor laser to that of a reference semiconductor laser. The IC, implemented in a 500 nm InP HBT process, contains an ECL digital single-sideband mixer to provide phase-locking at a +/− 20 GHz offset frequency, and also contains a wideband phase-frequency detector to provide loop acquisition given up to +/−40 GHz initial frequency offset.

A 58.4mW solid-state power amplifier at 220 GHz using InP HBTs

A 220 GHz solid state power amplifier MMIC is presented demonstrating 58.4 mW of output power with 5.4dB compressed gain. The 8-cell amplifier has a small signal gain of 8.9 dB at 220 GHz, and 3-dB bandwidth from 206 to 242GHz. Amplifier cells are formed using a 250nm InP HBT technology and a 5um BCB thin-film, non-inverted microstrip wiring environment. Power division and combining of the eight amplifier cells is done by a 2-1 quarter wave combiner series connected to a 4-1 Dolph-Chebyshev combiner. More than 50mW of output power was observed from 215 to 225GHz.

THz Indium Phosphide Bipolar Transistor Technology

Scaling laws and limits of THz indium Phosphide heterojunction bipolar transistors (HBTs) are presented. The primary limits to scaling through the 32 nm/3 THz node are the resistivity, penetration depth, and current-carrying capability of the emitter and base contacts. A processes flow with refractory dry-etch emitter and base contacts is presented. Beyond the 32 nm node, degenerate injection in the emitter-base junction limits transconductance and impedes scaling. At the 32 nm node, bandwidths will be sufficient for 1.4 THz transmitters and receivers.