Chenhui Jiang

EM simulation accuracy enhancement for broadband modeling of on-wafer passive components

This paper describes methods for accuracy enhancement in broadband modeling of on-wafer passive components using electromagnetic (EM) simulation. It is shown that standard excitation schemes for integrated component simulation leads to poor correlation with on-wafer measurements beyond the lower GHz frequency range. We show that this is due to parasitic effects and higher-order modes caused by the excitation schemes. We propose a simple equivalent circuit for the parasitic effects in the well-known ground ring excitation scheme. An extended L-2L calibration method is shown to improve significantly the accuracy of the on-wafer component modeling, when applied to parasitic effect removal associated with the excitation schemes.

A Novel Method for HBT Intrinsic Collector Resistance Extraction from S-Parameters

In this paper the extraction of series resistances for high-speed InP DHBT devices is investigated. Known extraction methods based on measured S-parameters are reviewed and error terms are identified. A novel method for intrinsic collector resistance extraction is proposed. The method is based on S- parameters measured in saturation and forward active regions. The results are applied to the large-signal modeling of InP DHBT devices using the UCSD HBT model and very accurate model response is obtained.

Optimization of integrated electro-absorption modulated laser structures for 100 Gbit/s ethernet using electromagnetic simulation

In this paper three options for very-high bit rate integrated electro-absorption modulated laser (EML) structures are investigated using electromagnetic simulation. A physics based distributed equivalent circuit model taking the slow- wave propagation characteristics of the modulation signal into account is proposed for the electro-absorption modulator (EAM) electrode arrangement. This model makes it possible to apply an EM/circuit co-simulation approach to estimate the electrical to optical transmission bandwidth for the integrated EML. It is shown that a transmission bandwidth of 70 GHz seems feasible with the investigated EML structures if the driving impedance is reduced to 25 Omega. It is also shown that the influence of electromagnetic cross-talk between components can be neglected in the estimation of the transmission bandwidth even in the case of very short separation zones. Finally, a slight decrease in transmission bandwidth is observed for an EML structure without ground pillars.

Broadband Packaging of Photodetectors for 100 Gb/s Ethernet Applications

The packing structure of functional modules is a major limitation in achieving a desired performance for 100 Gb/s ethernet applications. This paper presents a methodology of developing advanced packaging of photodetectors (PDs) for highspeed data transmission applications by using 3-D electromagnetic (EM) simulations. A simplified model of the PD module is first used to analyze and optimize packaging structures and propose an optimal packaging design based on the simplified model. Although a PD module with improved performance proved the success of the optimal packaging design, the simplified model could not identify other important bandwidth limitation effects. Therefore, a full 3-D EM model of PD modules is developed to predict the optical-to-electrical response of the module, and with this model, it is possible to identify a critical mode mismatch effect as another important factor of limiting the bandwidth of PD modules. After eliminating the mode mismatch effect by improving the chip-conductor-backed coplanar waveguide transition, a final optimal packaging structure is implemented for the PD module with reduced attenuation up to 100 GHz and a broader 3-dB bandwidth of more than 90 GHz. Furthermore, the PD module exhibits excellent performance under the high-speed data-transmission experiment with 107 Gb/s data rate.

GaAs wideband low noise amplifier design for breast cancer detection system

Modern wideband systems require low-noise receivers with bandwidth approaching 10 GHz. This paper presents ultra-wideband stable low-noise amplifier MMIC with cascode and source follower buffer configuration using GaAs technology. Source degeneration, gate and shunt peaking inductors are used to explore simultaneous wideband noise optimization and input power matching requirement. The low-noise amplifier circuit operates across a band of 0.3 to 10 GHz with a gain of around 14 dB and the measured noise figure NF below 1.5 dB up to 8 GHz. Measured small-signal results show good stability and very good agreement with simulated values. It is discussed in the paper that with more inductive peaking amplifier operation can be extended to even higher frequency, resulting in an even larger bandwidth.

Packaging Aspects of Photodetector Modules for 100 Gbit/s Ethernet Applications

Packaging is a major problem at millimetre-wave frequencies approaching 100 GHz. In this paper we present that insertion losses in a multi-chip module (MCM) can be less IL <0.6 dB at 100 GHz. The paper also analyzes in detail resonance modes in the packages. The characteristic of conductor-backed coplanar waveguides (CBCPWs) with vias is accurately analyzed using 3D electromagnetic (EM) simulation over a wide frequency range. Patch antenna mode resonances are identified as a major origin of resonances in simulated and measured transmission characteristics of the CBCPW with vias. Based on EM simulations, we propose several optimized arrangements for vias and bonding wires placement, to efficiently suppress the resonances and achieve excellent transmission performance of the PD module packaging. Based on our simulated results we postulate that it is possible to obtain resonance-free electrical transmission in the PD package with IL <0.6 dB over a frequency from DC to 110 GHz.

Optimization of Packaging for PIN Photodiode Modules for 100Gbit/s Ethernet Applications

In this paper the packaging of optical components is investigated employing a conductor backed coplanar waveguide (CBCPW). The study is performed using 3D electromagnetic (EM) simulations in a broadband range up to 110 GHz. Higher-order resonances are observed in both measurement and simulation results. Based on the verified EM simulation setup, the origin of resonances is identified and remedies are suggested in the paper. Several optimization schemes for achieving good transmission characteristics for the planar structure as well as for the coax-CPW transition are proposed such as properly coating side metallization on the CPW, substrate spacing to the metal housing, and developing metal posts in the substrate of the CPW.

Electromagnetic modeling and optimization of packaged photodetector modules for 100 Gbit/s applications

In this paper, we propose an accurate full 3D EM behavioral model of PD chips for the first time. The model, which is meshed at 130 GHz, runs for about 17 minutes on an Intel Core2 Duo CPU@3 GHz PC with 3.5 GB of RAM. The impact of various parameters in wire- bonding transitions for transmission characteristic is summarized in the Table I. When numbers of bonding wires are placed separately all through strips of CBCPWs as well as keeping an optimized gap of transitions, more than 10 GHz bandwidth improvement can be achieved compared the worst case. We also notice that optimization on bonding wires does not significantly improve the fast decay beyond 60 GHz. Further investigation and optimization of the transition is required including a redesign of the CBCPW.

Wireless and photonic high-speed communication technologies, circuits and design tools

Wireless and Ethernet communications aim at millimeter-wave frequency operation and gigabit-per-second data transmission. Increased data rates in wireless systems can only be achieved at frequencies beyond 60 GHz or 80 GHz and in 100 Gbit/s (100-G) data transmission over fibre. Both systems are fundamental to emerging consumer and professional applications. These systems start to emerge as near future applications and are subject of ongoing research activities in Europe, for example within the EU FP6 GIBON project. Wireless systems with over 100 GHz carriers as well as first over 100-G fibre systems were reported. These communication systems present new challenges for circuit designers. The presentation will be devoted to technologies and various aspects of circuit design for 100 G applications. We will present overview on wired and wireless systems demonstrating the challenges of this research including design challenges, relevant trade-offs and the present bottlenecks. Different system architectures will be presented with their impact on component requirements. Similarities and differences of wired and wireless applications will be pointed out. Design methodologies, necessary tools and circuit performances obtained in various technologies (Si, SiGe, GaAs and InP) will be presented and discussed. Finally, modeling, measurements and packaging problems at such high frequencies/speeds will be also addressed.

Packaging of photodetector modules for 100 Gbit/s applications using electromagnetic simulations

In this paper we demonstrate ultra-broadband packaging and interconnection designs for photodetector (PD) modules for 100 Gbit/s data transmission applications. The design of packaging and interconnection structures is based on accurate and reliable 3D electromagnetic (EM) simulations. Mode conversion loss due to mode mismatch is identified as the dominant effect of limiting bandwidth of packaged modules. Finally, PD chips are successfully packaged by using wire-bonding technology and conventional coplanar waveguide (CPW) for avoiding mode mismatch. The new packaged PD module demonstrates approximately 100 GHz 3 dB bandwidth.