D. Le Berre

Electromagnetic analysis of RF interconnect

Today, the performances of integrated electronic circuits are limited by global interconnects. To achieve in performance, one needs to consider new solutions to carry the information in the chips or along the system. This communication deals with the study of RF interconnects, which is among the options under discussion within the ITRS [1]. At first, we recall the concept of RF interconnects to further illustrate it in the case of 4-bit transmission. Then, we calculate the transfer function of a complete RF interconnect to identify the parameters to be optimized, in order to increase the gain and obtain relative plane curves over a wide frequency band. Finally, we conduct on electromagnetic study of various coupling options that can be expected when using the available technologies.

A WDM fiber-radio experiment incorporating a wavelength-self-tunable single-side-band filter

Optical single-side-band (OSSB) sources compensate for deleterious chromatic dispersion effects in fiber-radio systems. A wavelength-self-tunable filter based on an iron doped indium phosphide photorefractive crystal is used to provide OSSB signals. The device is incorporated into the WDM fiber-radio transmission of two optical signals modulated at a 16 GHz frequency and carrying 140 Mbit/s data streams.

Frequency Domain Analysis of Transmission Zeroes on High-Speed Interconnects in the Presence of an Orthogonal Metal Grid Underlayer

This paper addresses the topic of high-speed interconnects in high density systems [systems on chip (SoCs), systems in package (SiPs), systems on package (SoPs), and multichip modules (MCMs)]. These microstrip or coplanar lines have, often, an underlayer of orthogonal metal grids liable to affect transmission characteristics. The characterization proposed in this paper relies on S -parameter measurements and electromagnetic simulations. The grids under study are of two kinds: grounded (CC) and floating (CO). In both cases, the signal is distorted in the time domain further to the occurrence of transmission zeroes whose position depend mainly on the grid length and, of course, on the grid charge, i.e., CC or CO. In order to easily estimate this position, we developed a simple equivalent circuit model and validated it by measurements and electromagnetic simulations. Then it was used to develop a set of expressions enabling one to analytically pinpoint the location of transmission zeroes in the frequency domain, while remaining valid for any underlayer of orthogonal metal lines or grids.

3D frequency-dependent RLC elements extraction by full wave analysis: identification of the return current paths in complex power and ground grids of high speed VLSI circuits

This communication deals with the extraction and simulation of on-chip RLC per unit length (p.u.l.) elements for an efficient analysis of high speed digital circuits. In this context, the current distribution in the whole circuit, power and ground grids included, has to be known to correctly estimate inductance. By using a 3D full-wave finite elements method, we identified the current paths arising in the power and ground grids when an on-chip signal switches on a wire placed in a metal below the grids.

Simulation, Measurement and Modeling of Orthogonal On-Chip Interconnects

This paper explains the appearance of resonant frequency due to underlayer orthogonal metal grid in microstrip line structures. In the context of global interconnects, this resonant frequency may lead to noise and has to be estimate. A model, which allows one to approximate this resonant frequency, is validated by measurement

Effects of mode conversion on parasitic coupling in high-speed VLSI circuits

The mode conversion means that a modification of the electromagnetic field configuration occurs, generally, after discontinuities. In deep submicron digital ULSI circuits, the mode conversion analysis is indispensable to identify the signal return path, the return current distribution and therefore, for an accurate inductance modelling which remains a challenging problem (Y. I. Ismael and E. G. Friedman, 2000). On the other hand, switching activity of high speed CMOS circuit may produce large current derivatives in wires (crosstalk) and substrate. These current transients can generate large potential surges and coupled noise. In this mind, a reduction of the mode conversion phenomenon decreases noise in high speed ULSI circuits (Y. Quere et al., 2003). We have investigated the mode conversion, in the frequency domain, for multiple-line inter-layer transitions in CMOS devices. The signal integrity analysis in time domain proved the detrimental effects of mode conversion. Finally, we confirmed that our design rule reduces the mode conversion phenomenon in the case of transition with multiple coupled lines.

Broad-Band Laser Circuit Command Design for Antenna Deport

The fiequency response of a LASER diode generally presents an electrooptic resonance. The amplitude and the frequency resonance vary with the bias current. In view to improve the LASER response, we present an original method for LASER command circuit design. It can also be applied to a differential amplifier comprising the synthesis of an active load as well as a one stage amplifier. The synthesis, carried out. witH lumped elements, markes no a priori assumptions about network topology, and an illustration is shown for an antenna deport application in the 10.7 - 14.5 GHz bandwidth using an HEMT transistor.

Frequency domain analysis of transmission zeroes on high-speed interconnects in the presence of an orthogonal metal grid underlayer

This paper addresses high-speed interconnects in high density systems (systems on chip (SoC) in package (SiP) ...). These lines (of microstrip or coplanar type) often have an underlayer of orthogonal metal grids which can affect transmission characteristics. We subsequently present a characterization through S-parameter measurements and electromagnetic simulations. Two kinds of grid are studied; grounded (CC) and floating grid (CO). In both cases, transmission zeroes appear. The position of these transmission zeroes in the frequency domain depends mainly on the grid length and, of course, on the grid charge CC or CO. In order to easily estimate it, we propose a simple equivalent circuit model which we validate by measurements and electromagnetic simulations. We then determine a set of expressions based on this model enabling us to analytically pinpoint the location transmission zero in the frequency domain, valid for any underlayer of orthogonal metal lines or grids.

Techniques to reduce mode conversion phenomena in high-speed on chip interconnects

This paper describes frequency effects of mode conversion in very high-speed VLSI circuits through a set of full-wave simulations. Long on-chip interconnects such as clock nets are concerned by this phenomenon despite conventional shielding techniques. The solutions proposed for mode conversion reduction rely on transposition of design rules used in microwave circuits.

Fully integrated distributed amplifier design on InP HBT technology for optoelectronics application

The bandwidth required by the amplifiers used for the 40 Gbits/sec photonic communication systems are linked to the actual data rate required and to the modulation used: over 50 GHz bandwidth may be required in certain cases. This paper presents the design of a completely integrated distributed amplifier for high data rate type of applications. Thanks to the use a special DC bias circuit, the amplifier just requires one negative voltage (-5 V) supply. As no decoupling capacitor is used to bias the active cells, the amplifier has no low cutoff frequency. The amplifier gain is 15 dB and its 3 dB cutoff frequency bandwidth 65 GHz, which gives an equivalent gain bandwidth product of 390 GHz. This is at the state of the art for the technology used. The simulation of the electromagnetic extraction of the layout is compared to the measurements results from DC to 50 GHz.