B. Eged

Measurement by vector-network analyzer and simulation of crosstalk reduction on printed circuit boards with additional center traces

Reduction of crosstalk among interconnects and printed circuit board (PCB) traces to a tolerable level is an important goal in circuit design. The authors show that even though crosstalk can be reduced by additional grounded PCB tracks, the grounded traces behave like resonators and produce unwanted ringing. The ringing frequency is determined by the electrical length of grounded segments. The amplitude of ringing can be reduced by applying band-limited signals to the network.<<ETX>>

Measurement and simulation of crosstalk reduction by discrete discontinuities along coupled PCB traces

Crosstalk among interconnects and printed-circuit board (PCB) traces is a major limiting factor of signal quality in high-speed digital and communication equipment. The paper evaluates coupled surface microstrip transmission lines with periodical loading and coupling. The situation may represent stray coupling and loading of digital buses due to connector pins, plated through holes at connector slots, and stubs as well as the input capacitance of active devices. This paper shows that discrete periodical coupling along coupled surface microstrip transmission lines may be used to reduce far-end crosstalk. An expression is given to calculate the discrete coupling capacitance to achieve optimum far-end crosstalk reduction. The reduction of far-end crosstalk is verified by measurements, and the good agreement between the simulated and measured data is shown. On the other hand, discrete loading does not significantly reduce near-end crosstalk, but will introduce additional ringing in the time domain. >

Reduction of far-end crosstalk on coupled microstrip PCB interconnects

Crosstalk among interconnects and PCB traces is a major limiting of signal quality in highspeed digital equipment. The paper evaluates a possible way of far-end crosstalk reduction with a special geometry of traces. This paper shows that increasing capacitive coupling along coupled surface microstrip traces may be used to reduce far-end crosstalk.<<ETX>>

Analytical calculation of the impedance of lossy power/ground planes

Power and ground planes are required to have low impedance over a wide range of frequencies. Parallel ground and power planes in multilayer printed-circuit boards exhibit multiple resonances, which increase the impedance. Dissipative loading the radial transmission line structure of the planes reducing the peaks of the resonances. The dissipative loads can be realized by resistors distributed on the surface or edges of plain pairs and lossy dielectric material can be applied for distributed loading. Calculations based on the analytical method and measurements results are presented for comparing to the calculated and simulated impedances.

Emulation of ad-hoc networks on IEEE 802.11

This paper reports on the emulation of ad-hoc networks based on the IEEE 802.11 standard using the Berkeley Network Simulator including its CMU Monarch (ad-hoc) extension (NS). We examined the emulation capabilities of the Network Simulator. Performance and verification tests also have been done using the emulator. Requirements of the emulator were tested. Some important attributes of emulation, like real-time requirements and CPU power were shown by the tests.

Server side round-trip delay measurements in WAP environments

Wireless Internet access is one of highest increasing service segments in telecom area. It offers the freedom of mobility and mass information backbone to the user. Providing general service quality framework around the system is necessary for a lot of reasons. Measurements and continuous monitoring of network performance is one of the key element of such framework. The methods developed for performance measurements in normal Internet environment cannot be directly applied due to the different properties of the wireless client terminals, used protocol stack and the server content. However, the methodology is usable and with the appropriate modifications the required procedures can be defined. The paper deals with the definition and implementation of the measurements and monitoring of the round trip delay in a WAP based wireless access environment.

The ALICE DAQ: current status and future challenges

The ALICE data acquisition system has been designed to support an aggregate event-building bandwidth of up to 2.5 GByte/s and a storage capability of up to 1.25 GByte/s to mass storage. A general framework called the ALICE Data Acquisition Test Environment (DATE) system has been developed as a basis for prototyping the components of the DAQ. DATE supports a wide spectrum of configurations from simple systems to more complex systems with multiple detectors and multiple event builders. Prototypes of several key components of the ALICE DAQ have been developed and integrated with the DATE system such as the ALICE Detector Data Link, the online data monitoring from ROOT and the interface to the mass storage systems. Combined tests of several of these components are being pursued during the ALICE Data Challenges. The architecture of the ALICE DAQ system will be presented together with the current status of the different prototypes. The recent addition of a Transition Radiation Detector (TRD) to ALICE has required a revision of the requirements and the architecture of the DAQ. This will allow for a higher level of data selection. These new opportunities and implementation challenges will also be presented.

Measurement and computer simulation of discrete discontinuities along coupled PCB traces

Crosstalk among interconnects and printed circuit board (PCB) traces is a major limiting factor of signal quality in high-speed digital and communication equipment. The authors evaluate coupled surface microstrip transmission lines with periodical loading and coupling. The situation represents stray coupling and loading of digital buses due to connector pins and plated through holes at connector slots. It is shown that discrete periodical coupling along coupled surface microstrip transmission lines may be used to reduce far-end crosstalk. An expression is given to calculate the discrete coupling capacitance to achieve optimum far-end crosstalk-reduction. Discrete loading does not significantly reduce near-end crosstalk, but will introduce additional ringing in the time domain.<<ETX>>

A direct microwave down-conversion method for software radios

Over the past few years, the software radio has emerged from theoretical research as a commercially viable and flexible digital communication system. Advances in digital technology are quickly making the software radio an attractive strategy for low-cost multi-dimensional transceivers. In software radios a relevant problem is the down-conversion with high image frequency suppression. For this purpose a down-converter has been developed utilizing a signal processing method along with the homodyne reception principle. A simplified system has been built to test this new method. For comparison the development of intermediate frequency digital sampling approach is in progress.

Digital Compensation in IF Modulated Upconversion Software Radio Architecture

In the transmitter path of software radios a relevant problem is the upconversion of the baseband or IF signal with high image frequency suppression. For this purpose an up-converter based on a quadrature modulator has been developed utilizing a signal processing method for increasing the image sideband supression. A simplified system has been built to test this new method. For extending the posibble modulation types and bandwidth the development of digital modulation approach using a direct digital synthesizer is in progress.