Convergence of Gaussian-beam modes in corrugated conical horns

Autor: F. Martín-Jiménez, J. A. López Fernández, J. Martín-Pintado, F. Tercero, E. García, Créidhe O'Sullivan, L. de Haro, M. Sierra-Castañer
Rok vydání: 2005
Předmět:
Zdroj: Microwave and Optical Technology Letters. 45:199-203
ISSN: 0895-2477
DOI: 10.1002/mop.20769
Popis: 4.5. LVDS signals, ground/power, and TTL signals in the daughter boards and backplane are placed in different layers, respectively, so that the TTL and LVDS signals will be isolated by the ground/ power plane(s) in order to minimize the noise coupling into LVDS signals from the large-swing TTL signals. A photograph of the daughter board and backplane in the demo system is shown in Figure 11. All the active devices are placed on daughter boards that transmit and receive the LVDS and TTL data streams. The circuit on the daughter boards is uniformity designed, but different functions (Tx or Rx) are approached by means of programming and provided with compatibility [9, 10]. A passive backplane is designed with various interconnects according to the requirement for investigating the SI issue of different interconnects. Point-to-point LVDS links are used for data transmission in the demo system for obtaining the perfect transfer performance and SI investigation. The unidirectional transmission of 10 pairs of the LVDS links group is used for the LVDS group data transmission in the demo system, which involves eight data pairs, a clock pair, and a frame pair [11]. The DDR operation mode is used for the LVDS clock. Each pair of LVDS links with the transmission rate of 500 M/bs is designed for a 250-MHz clock frequency. The throughput of 4 Gb/s is provided to each group of LVDS. CONCLUSION In this paper, the SI analysis of high-speed digital systems has been systematically performed using the full-wave electromagnetic analysis method. From the simulated and measured results, we can observe that high-speed digital signals at 500 M/bs can be smoothly transmitted in the designed long interconnects on the backplane. Transmission-line discontinuities generate the main problems, which cause signal degradation for high-speed signal transfer on PCBs. Such discontinuities can be sharp bends on the trace, skews between conductors within a differential pair, and vias through the board. In the other words, these discontinuities are points that cause impedance discontinuities of the transmission line, which cause reflections. The following layout rules for transmission lines are summarized to enhance board operation: avoid 90° turns and use arcs or 45° bevels. The distance between two traces should remain constant in order to avoid discontinuities in differential impedance. If vias cannot be avoided, use as few as possible.
Databáze: OpenAIRE