Ahmet Cagri Ulusoy

On the Analysis and Design of Low-Loss Single-Pole Double-Throw W-Band Switches Utilizing Saturated SiGe HBTs

This paper describes the analysis and design of saturated silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) switches for millimeter-wave applications. A switch optimization procedure is developed based on detailed theoretical analysis and is then used to design multiple switch variants. The switches utilize IBMs 90-nm 9HP technology, which features SiGe HBTs with peak f T/ fmax of 300/350 GHz. Using a reverse-saturated configuration, a single-pole double-throw switch with a measured insertion loss of 1.05 dB and isolation of 22 dB is achieved at 94 GHz after de-embedding pad losses. The switch draws 5.2 mA from a 1.1-V supply, limiting power consumption to less than 6 mW. The switching speed is analyzed and the simulated turn-on and turn-off times are found to be less than 200 ps. A technique is also introduced to significantly increase the power-handling capabilities of saturated SiGe switches up to an input-referred 1-dB compression point of 22 dBm. Finally, the impact of RF stress on this novel configuration is investigated and initial measurements over a 48-h period show little performance degradation. These results demonstrate that SiGe-based switches may provide significant benefits to millimeter-wave systems.

A 40 Gb/s Monolithically Integrated Linear Photonic Receiver in a

This letter presents the first 40 Gb/s monolithically integrated silicon photonics linear receiver (Rx) comprising a germanium photodiode (Ge-PD) and a linear transimpedance amplifier (TIA). Measured optical-electrical (O/E) 3 dB bandwidth (BW) of the Rx is 31 GHz. At 40 Gb/s, the Rx achieves a sensitivity of -3 dBm average optical input power with BER of 2.5×10-11. It operates at λ = 1.55 μm wavelength, uses 3.3 and 3.7 V power supplies, dissipates 275 mW of power, provides maximum differential output amplitude of 500 mVpp, and occupies an area of 3.2 mm2. The presented receiver achieves the highest bit rate among the published work in monolithically integrated silicon photonics receivers.

0.25~\mu {\rm m}

This work demonstrates two 94 GHz SPDT quarter-wave shunt switches using saturated SiGe HBTs. A new mode of operation, called reverse saturation, using the emitter at the RF output node of the switch, is utilized to take advantage of the higher emitter doping and improved isolation from the substrate. The switches were designed in a 180 nm SiGe BiCMOS technology featuring 90 nm SiGe HBTs (selective emitter shrink) with fT/fmax of 250/300+ GHz. The forward-saturated switch achieves an insertion loss and isolation at 94 GHz of 1.8 dB and 19.3 dB, respectively. The reverse-saturated switch achieves a similar isolation, but reduces the insertion loss to 1.4 dB. This result represents a 30% improvement in insertion loss in comparison to the best CMOS SPDT at 94 GHz.

BiCMOS SiGe:C Technology

This paper investigates the impact of the interconnect between the bottom and the top metal layers on the transistor RF performance of CMOS and silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) technologies. State-of-the-art 32-nm silicon-on-insulator (SOI) CMOS and 120-nm SiGe HBT technologies are analyzed in detail. Measured results indicate a significant reduction in the unity-gain frequency (fT) from the bottom to the top metal layer for advanced CMOS technology nodes, but only a slight reduction for SiGe HBTs. The 32-nm SOI CMOS and SiGe HBT technologies have a reduction in the maximum oscillation frequency (fmax) from the bottom to the top metal layer of ~12% and 5%, respectively. By analyzing technology scaling trends, it is clear that SiGe HBTs can now achieve a similar peak fT at the top metal layer in comparison with advanced CMOS technology nodes, and a significantly higher fmax. Furthermore, in CMOS technologies, the top metal layer fmax appears to have reached a peak around the 45-65-nm technology nodes, a result which has significant implications.

A 94 GHz, 1.4 dB Insertion Loss Single-Pole Double-Throw Switch Using Reverse-Saturated SiGe HBTs

In this paper a linear optical modulator driver fabricated in a 0.13 μm BiCMOS SiGe:C technology is presented. The prototype is to be used in hybrid configuration with an InP segmented Mach-Zehnder modulator (SE-MZM), forming a transmitter sub-system with direct interface to the digital to analog converter (DAC), which is suitable for high order modulation formats. A tunable broadband delay line that provides for better optical and electrical delay synchronization was also implemented. The driver, designed for a 16-segments modulator, features 8 dB of gain, 32 GHz of 3-dB bandwidth and delivers a differential output swing of 2.5 Vpp, dissipating 1.65 W of DC power. The measured total harmonic distortion (THD) at 1 GHz is lower than 3.7%. The delay line allows for a ±15% of delay tuning from the nominal value of 3.68 ps per segment. To the best knowledge of the authors, this is the first time a linear driver for a SE-MZM is presented.

A Comparison of the Degradation in RF Performance Due to Device Interconnects in Advanced SiGe HBT and CMOS Technologies

This paper outlines the design and electrical characterization of an optical modulator driver fabricated in a 0.13 μm BiCMOS SiGe:C technology. The prototype, optimized for hybrid assembly with a 15-segment InP segmented Mach-Zehnder modulator (SE-MZM), displays integrated 4-bit digital-to-analog converter (DAC) functionality, allowing the generation of PAM-16 modulation format. The driver delivers a differential output swing of 2.5 Vpp across all 15 segments, dissipating less than 1 W of power. Electrical eye diagrams up to 40 Gb/s are reported, demonstrating the capability for high speed 4 × 40 Gb/s electro-optical transmission. The devised hybrid solution proves the potential of SiGe HBT drivers for achieving higher speeds over their CMOS counterparts, with comparable power dissipation.

A 2.5 Vppd broadband 32 GHz BiCMOS linear driver with tunable delay line for InP segmented Mach-Zehnder modulators

In this paper, a monolithically integrated segmented linear driver and Mach-Zehnder modulator (MZM) are presented. The transmitter is fabricated in electronic-photonic integrated circuit 0.25-μm SiGe:C BiCMOS technology, with fT/fmax = 190 GHz. The driver and the modulator are divided into 16 segments and the MZM phase shifter has a total length of 6.08 mm. The segmented driver delivers a maximum of 4 Vpp differentially, featuring a gain of 13 dB and total harmonic distortion below 5%. Electro-optical time-domain measurements using PAM-4 modulation format are performed, demonstrating optical eye-diagrams up to 25 Gbaud. The electro-optical bandwidth of the transmitter is 18 GHz. The power dissipation of the driver is 1.5 W, resulting in an energy per bit of 30 pJ/bit at 50 Gb/s. The reported optical transmitter demonstrates for the first time an implementation of a linear driver integrated with an MZM in a Si monolithic process.

A 40 Gbaud SiGe:C BiCMOS driver for InP segmented MZMs with integrated DAC functionality for PAM-16 generation

In this work, a monolithically integrated segmented driver and Mach-Zehnder modulator (MZM) in 0.25 μm SiGe:C BiCMOS technology is presented. The driver and the modulator are divided in 16 segments and the MZM has a total length of 6.08 mm. The driver has a maximum gain of 14.5 dB. Electro-optical time-domain measurements were performed and an optical eye-diagram with more than 13 dB of extinction ratio at 28 Gb/s is demonstrated. The driver dissipates a total of 2 W of DC power. To the best knowledge of the authors, the presented work shows the highest extinction ratio achieved at 28 Gb/s in silicon modulators.

A Monolithically Integrated Segmented Linear Driver and Modulator in EPIC 0.25-

This work demonstrates the implementation of a D-band single-pole double-throw switch(SPDT) in 32 nm CMOS SOI technology. A tuned shunt topology is used to achieve the lowest insertion loss. The switch demonstrates state-of-the art performance showing an insertion loss of 2.6 dB at 140 GHz and good matching across the whole D-band. Measurements also show high isolation of greater than 20 dB from 110 to 170 GHz. This is the lowest insertion loss of an SPDT switch that has been designed for the D-band and reported in a 32 nm CMOS SOI process.

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In this work, a modulator driver in 0.13 μm SiGe:C BiCMOS technology for 25 Ω travelling wave electrode (TWE) Mach-Zehnder Modulators (MZM) is presented. The design integrates two channels for differential driving of IQ signals. The driver delivers a differential output signal of 4 Vpp, exhibits a differential gain of 12 dB and has an output return loss better than 9 dB. It works from a 4.7 V supply and dissipates 1.1 W per channel. Data rate of 40 Gb/s is demonstrated by time-domain measurements. To the best knowledge of the authors, this is the first time a design of a driver suitable for 25 Ω TWE MZMs is presented.