In this submission, we present the characterization of a silicon electro-optical modulator using Mach-Zehnder interferometer structure. We characterize the transmission spectra upon various DC and RF voltage supplies with different input optical power. We show the slope efficiency dependence on the optical input power. We also measured the spur-free dynamic range of the modulator using two-tone method, showing an optical power dependent SFDR with maximum value of ~ 7.5 dBc.
Wideband directional couplers with high isolation are designed for millimeter-wave applications and implemented in two different in-house Si-based technologies processes - Si-benzocyclobutene (Si-BCB) process and LIGA-like process (lithography, electroplating, and molding). Two 3D tandem directional couplers for millimeter-wave/THz applications have been constructed using the Si-BCB process. The coupling and isolation of tandem coupler have been analyzed from circuit topology. A branch-line coupler is also constructed using the LIGA-like process. The electrical characteristics of these couplers have been simulated in 3D simulator. By comparing the results, the proposed Si-BCB process is noted to provide flexibilities in both the design and implementation of passive components.
Design of quadrature oscillator at 10-GHz is demonstrated, which involved development of direct parameter extraction technique of scalable varactor. The varactor is used in the tank circuit. The effects of the substrate parasitic of SiGe in quadrature LC oscillator design were also investigated. Exploiting the substrate effect and accurate device characterization, a quadrature oscillator with -106-dB phase noise at 1-MHz offset using 2.50-V single supply was measured. The core oscillator consumes only 1.6-mA each at 10-GHz.
A high capacitance density (C/sub density/) metal-insulator-metal (MIM) capacitor with niobium pentoxide (Nb 2 O 5 ) whose k value is higher than 40, is developed for integrated RF bypass or decoupling capacitor application. Nb 2 O 5 MIM with HfO 2 /Al 2 O 3 barriers delivers a high C/sub density/ of >17 fF/μm 2 with excellent RF properties, while maintaining comparable leakage current and reliability properties with other high-k dielectrics. The capacitance from the dielectric is shown to be stable up to 20 GHz, and resonant frequency of 4.2 GHz and Q of 50 (at 1 GHz) is demonstrated when the capacitor is integrated using Cu-BEOL process.
The through silicon via (TSV) technology provides a promising option to realize a compact millimeter-wave (mmW) and terahertz (THz) system with high performance. As the fundamental elements in this system, transmission lines (T-lines) and interconnects are very important and therefore studied in this paper. A TSV-based substrate integrated waveguide (SIW) is also characterized. The results show that, the T-lines and interconnects are viable at frequencies lower than ~150 GHz whereas SIW can operate relatively well up to 300 GHz. In addition, two mmW components, i.e., a hairpin filter and a patch antenna, are designed by the TSV technology. Results of all the above passive components indicate that the low-resistivity silicon is the main cause of the total loss. Afterwards, two novel TSV-based topologies are proposed to efficiently integrate an antenna with active circuits for the mmW and THz applications.
This paper presents a terahertz (THz) transmitter (Tx) and receiver (Rx) chipset operating around 400 GHz in 0.13- μm SiGe BiCMOS technology. The Tx chip consists of a voltage-controlled oscillator, a buffer, a modulator, a power amplifier, a frequency tripler, and a substrate integrated waveguide (SIW) antenna. This antenna has an additional high-pass filtering characteristic to suppress the unwanted fundamental ( f0 ) and second harmonic (2 f0 ) signals by 50 and 30 dB, respectively. The Rx chip includes a proposed reconfigurable SIW antenna and a novel two-mode subharmonic mixer with ~ 5-dB reduction of conversion loss. The Rx chip consumes 50 nA from a 1.2-V supply. The measurement results of the Tx and Rx chips and a back-to-back test of the Tx/Rx chipset show the feasibility and pave the way of implementing a fully integrated THz system in silicon technology for mass production.
High-data-rate short-range communication and image systems beyond 100GHz impose crucial requirements on signal sources, demanding superior purity and stability. Using frequency multipliers with high efficiency and multiplication factor to generate the N th harmonic signal that is phase-locked by a PLL at the fundamental frequency provides an alternative solution. The desired signal in an active frequency multiplier can be generated using Class B/C amplifiers, where a half-wave signal containing all harmonics is first created and then filtered to remove the undesired harmonic components [1]. Another approach is to apply the same signal to both the IF and RF ports of a mixer to construct a doubler followed by cascading to form the quadrupler [3]. The linear superposition (LS) technique that superimposes four phase-shifted half-waves of 0°, 90°, 180°, and 270° is another popular scheme [5]. For multipliers with high multiplication factors, these prior techniques may offer very low power efficiency (η). Quadrupler cores based on Class B/C amplifiers, mixers, or the LS technique had been reported with η of 0.9% [1], 0.04% [3] and 0.0002% [5], respectively. Therefore, instead of improving the η of the multiplier cores, the design of the subsequent amplifiers after the multiplier to boost the η and output power has become a popular approach. We have substantially enhanced the η of a frequency quadrupler core using a phase-controlled push-push (PCPP) technique to directly synthesize the 4 th harmonic. We noted that in an ideal situation, the proposed quadrupler circuit is able to generate almost no other harmonics, attaining an η of 50%. In this paper, we present a 121-to-137GHz frequency quadrupler based on a 0.13μm SiGe BiCMOS process. For the purpose of measurement, a balun coupled with buffers to provide the differential signals is also designed. The DC power consumptions of the quadrupler core and input buffers are 6.4mW and 28.8mW, respectively. Our demonstrated quadrupler core is able to achieve 9% (1.6% including input buffers) power efficiency at 1.6V, with a -2.4dBm output signal.
In modern CMOS technologies, metal dummy fills are required to maintain metal density uniformity and to planarize the layers. As frequency increases, the effect of the metal dummy fills on the CMOS integrated circuits or components should be taken into account. This work presents experimental results of the effect of metal dummy fills on the microwave behavior of spiral inductors fabricated in a standard 0.18-μm CMOS technology. The influences on the equivalent model parameters and the Q-factor are characterized based on measured S-parameters of inductors with and without metal dummy fills.
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