Seungyong Baek

Analysis of noise coupling from a power distribution network to signal traces in high-speed multilayer printed circuit boards

As layout density increases in highly integrated multilayer printed circuit boards (PCBs), the noise that exists in the power distribution network (PDN) is increasingly coupled to the signal traces, and precise modeling to describe the coupling phenomenon becomes necessary. This paper presents a model to describe noise coupling between the power/ground planes and signal traces in multilayer systems. An analytical model for the coupling has been successfully derived, and the coupling mechanism was rigorously analyzed and clarified. Wave equations for a signal trace with power/ground noise were solved by imposing boundary conditions. Measurements in both the frequency and time domains have been conducted to confirm the validity of the proposed model.

Reduction of crosstalk noise in modular jack for high-speed differential signal interconnection

Crosstalk noise has become a significant problem in the design of high-speed digital interconnections. In this paper, we demonstrate a crosstalk reduction method, which has been successfully applied to the design of a CAT-5E modular jack. The CAT-5E is a newly adopted cabling and connector standard for advanced cabling network systems to assure more robust, reliable and high-speed operation, which is based on differential mode signal transmission using unshielded twist pair (UTP) cable. The improved design of the modular jack shows minimal crosstalk noise and return loss over a wide range of manufacturing conditions. The improved crosstalk characteristics of the modular jack were accomplished by inserting embedded capacitors on the printed circuit board (PCB) of the modular jack. The embedded capacitors compensate for the unbalanced capacitive crosstalk that occurs in the plug and insert. In particular, the embedded balancing capacitor is designed to have maximum capacitance, with limited PCB area, by using a double-sided PCB design. Less than -45 dB near-end-crosstalk (NEXT) was achieved after the crosstalk noise compensation, satisfying the CAT-5E specification for frequencies up to 100 MHz.

Accurate high frequency lossy model of differential signal line including mode-conversion and common-mode propagation effect

The loss in multilayer printed circuit boards (PCB) becomes a crucial problem and lacks precise models in high-speed interconnections such as the SerDes channel. Moreover, unbalanced and discontinuous structures generate undesirable mode-conversion, differential-to-common mode and common-to-differential mode. We have propose an accurate and efficient differential line model where all of the mode-conversion, common-mode propagation and frequency-dependent loss are taken into consideration over the GHz frequency range.

Noise coupling to signal trace and via from power/ground simultaneous switching noise in high speed double data rates memory module

We suggested the model to demonstrate simultaneous switching noise (SSN) coupling to signal and verified experimentally. There are two coupling mechanisms; one is the SSN coupling through the reference changing via, and the other is the SSN coupling through the signal trace. Through measurement and analysis, we confirmed that the worst SSN coupling occurs when strip lines have the signal via changing reference plane with SSN. Furthermore, we demonstrated that the power/ground noise coupling to the signal is reduced by placing the reference changing via at the position where the power/ground cavity impedance is low, or by adjusting the line length between two reference changing vias.

Increased radiated emission and impedance change by edge placement of high-speed differential lines on printed circuit board

An edge placement of high-speed differential lines breaks the balance of differential pair, that results in reducing current of each line of the differential pair. The impedance of the lines is deviated from the desired value. Moreover it becomes a significant source of the radiated emission. In this paper, the authors present a variation of differential mode impedance and common mode impedance caused by the edge placement of microstrip differential pair with finite ground width. Also, they demonstrate the effect of the edge-placement of the differential pair on the increase of the radiated emission noise.

GHz twisted differential line structure on printed circuit board to minimize EMI and crosstalk noises

The concept of twisted pair on the cable interconnection can be readily applied to the differential lines on printed circuit board (PCB), which enables enhanced immunity against crosstalk and radiated emission. In this paper, twisted differential line (TDL) is implemented on PCB and fully characterized. First, the transmission characteristics of TDL including propagation constant and differential impedance are extracted by using 3D full-wave analysis. The potential of TDL for the transmission of over GHz signal and enhanced immunity against crosstalk and radiated emission is clearly shown. Second, the measurement results reconfirm TDLs capability as a good transmission line structure over several GHz. Also, it is modeled by a simple equivalent circuit, based on measurement results. Third, the enhanced immunity of TDL against crosstalk and radiated emission is clearly demonstrated by measurement results. TDL is compared with other transmission line structures showing its superiority. Finally, several ideas to improve TDLs performance are suggested and verified to be useful.

Enhanced immunity against crosstalk and EMI using GHz twisted differential line structure on PCB

There is a growing tendency to adopt a differential signaling scheme for critical signals. To support differential signaling, differential transmission lines are required. The concept of twisted pair on the cable interconnection can be readily applied to differential transmission lines on printed circuit boards (PCBs), which enables enhanced immunity against crosstalk and radiated emission. The new differential transmission line called twisted differential line (TDL) has been introduced. In this paper the enhanced immunity of TDL against crosstalk and radiated emission is clearly demonstrated with both simulation and measurement. TDL is compared with other differential transmission lines showing its superiority. Moreover several ideas to improve the performance of TDL are proposed and verified to be useful. Offset-TDL (O-TDL) improves crosstalk immunity further and vertical-TDL (V-TDL) enables reduced routing area while maintaining performance.

A novel twisted differential line for high-speed on-chip interconnections with reduced crosstalk

Differential signaling has become a popular choice for high-speed interconnection schemes, offering superior immunity to external noise. However, conventional differential transmission lines still have problems, such as crosstalk and radiated emission. To overcome these, we propose a twisted differential line (TDL) structure. In this paper, experimental results of the proposed structure on a multi-layer PCB are summarized. Its improved immunity to crosstalk, and the reduced radiated emission have been successfully demonstrated. Furthermore, the TDL is firstly implemented on a chip and the preliminary results are reported. Finally, it is demonstrated that the proposed TDL delivers a promising solution for high-speed and high-density digital interconnection designs.

Compensation of ESD and device input capacitance by using embedded inductor on PCB substrate for 3 Gbps SerDes applications

We first propose a simple and efficient reactive termination circuit for compensation of the parasitic capacitance which results from the ESD protection circuit and device input capacitance. By using this compensation circuit, the broadband impedance of the receiver circuit is controlled and matched, and the distortion of the high speed signal due to the inherent parasitic capacitance is significantly reduced. A conventional preemphasis circuit is applied concurrently to the design of a high-speed transceiver together with this technique. The required parameter values for the preemphasis circuit and the suggested reactive termination circuit are optimized in the frequency domain. Simulations in the time domain shows an improvement in the eye diagram.

Pulse-coupling measurement of coupled microstrip lines using a micromachined picosecond optical near-field probe

By measuring the transverse electric-field distributions using a newly developed micromachined optical near-field mapping probe, pulse-coupling phenomena on coupled microstrip lines are reported for the first time. The measured field distribution of the propagating coupled pulse provides useful information to aid understanding of the coupling phenomena; this cannot be obtained by conventional external-port access test instruments. The measurement is performed based on the picosecond photoconductivity of low-temperature-grown GaAs (LT-GaAs). A system for the measurement of the internal electric field distribution using the optical near-field probe is described and characterized. It is capable of measuring independent orthogonal components of free-space electric fields with less than 2-ps temporal resolution and with minimal loading effects. The loading effects of the probe are minimized by adopting a micromachining technique for the use of a 1-/spl mu/m-thick LT-GaAs epilayer as a substrate, and by using silver-paint-coated optical fibers for electrical connections.