Omeed Momeni

High Power Terahertz and Millimeter-Wave Oscillator Design: A Systematic Approach

A systematic approach to designing high frequency and high power oscillators using activity condition is introduced. This method finds the best topology to achieve frequencies close to the fmax of the transistors. It also determines the maximum frequency of oscillation for a fixed circuit topology, considering the quality factor of the passive components. Using this technique, in a 0.13 μm CMOS process, we design and implement 121 GHz and 104 GHz fundamental oscillators with the output power of -3.5 dBm and -2.7 dBm, respectively. Next, we introduce a novel triple-push structure to realize 256 GHz and 482 GHz oscillators. The 256 GHz oscillator was implemented in a 0.13 μm CMOS process and the output power of -17 dBm was measured. The 482 GHz oscillator generates -7.9 dBm (0.16 mW) in a 65 nm CMOS process.

A Novel CMOS High-Power Terahertz VCO Based on Coupled Oscillators: Theory and Implementation

We introduce a novel frequency tuning method for high-power terahertz sources in CMOS. In this technique, multiple core oscillators are coupled to generate, combine, and deliver their harmonic power to the output node without using varactors. By exploiting the theory of nonlinear dynamics, we control the coupling between the cores to set their phase shift and frequency. Using this method, two high-power terahertz VCOs are fabricated in a 65 nm LP bulk CMOS process. The first one has a measured output power of 0.76 mW at 290 GHz with 4.5% tuning range and the output power of the second VCO is 0.46 mW at 320 GHz with 2.6% tuning range. The output power of these signal sources is 4 orders of magnitude higher than previous CMOS VCOs and is even higher than VCOs implemented in compound semiconductors with much higher cut-off frequencies.

A Broadband mm-Wave and Terahertz Traveling-Wave Frequency Multiplier on CMOS

A wideband frequency multiplier that effectively generates and combines the even harmonics from multiple transistors is proposed. It takes advantage of standing-wave formation and loss cancellation in a distributed structure to generate high amplitude signals resulting in high harmonic power. Wide bandwidth operation and odd harmonic cancellation around the center frequency are the inherent properties of this frequency multiplier. Using this methodology, we implemented a frequency doubler that operates from 220 GHz to 275 GHz in a standard 65 nm CMOS process. Output power of 6.6 dBm (0.22 mW) and conversion loss of 11.4 dB are measured at 244 GHz.

A 283-to-296GHz VCO with 0.76mW peak output power in 65nm CMOS

Sub-mm-Wave and terahertz frequencies have many applications such as medical imaging, spectroscopy and communication systems. CMOS signal generation at this frequency range is a major challenge due to the limited cut-off frequency of transistors and their low breakdown voltage. A recent work has demonstrated generation of high power at a fixed frequency in the sub-mm-Wave range using a harmonic oscillator [1]. However, for most applications a tunable signal source is necessary. In previous works, frequency multipliers are used as an alternative for tunable power generation above 150GHz [2]. In this work, for the first time we introduce a tunable high-power oscillator at sub-mm-Wave frequencies in low-power (LP) bulk CMOS.

A 10-Gb/s Inductorless Transimpedance Amplifier

A new technique to design an inductorless transimpedance amplifier (TIA) is introduced. This technique uses N similar TIAs in parallel configuration to boost the overall bandwidth while keeping the transimpedance gain constant. Using this method, we design and implement a 10-Gb/s inductorless TIA with an active area of only 0.06 mm2 and a differential transimpedance gain of 62 dBΩ in a digital 0.13-μm CMOS process. There is good agreement among the theory, simulation, and experimental results.

A Silicon-Based 0.3 THz Frequency Synthesizer With Wide Locking Range

A 300 GHz frequency synthesizer incorporating a triple-push VCO with Colpitts-based active varactor (CAV) and a divider with three-phase injection is introduced. The CAV provides frequency tunability, enhances harmonic power, and buffers/injects the VCO fundamental signal from/to the divider. The locking range of the divider is vastly improved due to the fact that the three-phase injection introduces larger allowable phase change and injection power into the divider loop. Implemented in 90 nm SiGe BiCMOS, the synthesizer achieves a phase-noise of -77.8 dBc/Hz (-82.5 dBc/Hz) at 100 kHz (1 MHz) offset with a crystal reference, and an overall locking range of 280.32-303.36 GHz (7.9%).

A high gain 107 GHz amplifier in 130 nm CMOS

A systematic method to design high gain amplifiers at frequencies close to the ƒmax of the transistors is introduced. This approach finds the optimum termination conditions to reach the maximum achievable gain of the device. Using this technique in a standard 130 nm CMOS process, we design and implement a 107 GHz amplifier with a gain of 12.5 dB, PAE of 4.4%, and saturated output power of >2.3 dBm, consuming 31 mW from a 0.95 V supply.

14.7 A 300GHz frequency synthesizer with 7.9% locking range in 90nm SiGe BiCMOS

The THz/sub-mm-Wave band is known to provide unique applications in spectroscopy, imaging and high-data-rate wireless communication. An accurate THz source is essential in coherent communications, radar systems, and frequency metrology. Recently, THz sources based on coupled VCOs with harmonic generation have been proposed [1]. However, open-loop signal sources exhibit severe frequency fluctuation, and are vulnerable to temperature/process/supply-induced frequency drift. The need for precise oscillation frequency with wide tuning range and low close-in phase noise calls for closed-loop topologies. Millimeter-Wave PLLs incorporating push-push VCOs have been demonstrated up to 164GHz [2] in silicon technology. [3] presented a 300GHz PLL with 0.12% locking range in III-IV technology.

Electrical Prism: A High Quality Factor Filter for Millimeter-Wave and Terahertz Frequencies

A 2-D electrical filter is introduced that is compatible with todays conventional integrated circuit processes. The rich 2-D propagation properties of the medium are used to introduce a novel high quality factor filter called an electrical prism. The proposed filter shows a quality factor much larger than the quality factor of the individual components at high millimeter-wave and terahertz frequencies. This structure also provides a negative effective index in a low-pass LC lattice. Based on this idea, we show filters with quality factors of 130 at 230 GHz and 420 at 460 GHz consisting of elements with the quality factor of 10 and 20, respectively. The effect of component loss on the filter quality factor is discussed in this paper. The negative effective index and the filter behavior of the lattice is verified by measuring a prototype on a CMOS process at 32-40 GHz. There is good agreement among the theory, simulation, and experimental results.

A 260GHz amplifier with 9.2dB gain and −3.9dBm saturated power in 65nm CMOS

Terahertz and millimeter-wave systems are known to have unique and significant applications in health, security and industry. Recently, CMOS technology is used to implement these systems for applications such as imaging, high-speed communication and radar [1]. Signal amplification for the target THz and high mm-Wave applications entails daunting design challenges, as operation frequency is getting closer to the Maximum Oscillation Frequency (fmax) of the transistors. This is mostly because the maximum available gain (Gma) drops significantly below useful levels at frequencies close to fmax. In this paper we introduce an amplifier that can boost the gain of the transistors close to the maximum fundamental value and achieves 9.2dB of gain and -3.5dBm of saturated output power at around 260GHz.