NEC—PN3PY系列寻呼机的指标测试

本文从实用的角度，以具有代表性的NEC数字式寻呼机PN3PY系列机为例，说明了在生产或维修时如何对数字寻呼机进行简便有效的指标测试．     

AF904无绝缘轨道电路安装调试技术

主要从技术角度论述AF904无绝缘轨道电路的基本原理、设备构成、安装、调试技术等.     

Research on the improved cooperative cellular system capacity

Recently, the multi-hop cellular networks have been widely studied in order to enhance the cell performances such as the cell capacity. While most of these works merely use the multi-hop methods instead of direct transmission without considering the co-channel inter-cell interference, signal transmission mode and the effects of the number of antennas. With the consideration of above important elements, this paper proposed an improved cellular system with multi-relay amplifies-and-forward (AF) cooperative transmission scheme and the corresponding capacity expression is derived under the corresponding environment. By using the potential space diversity and selecting relays based on maximizing the capacity, the cellular system capacity can be improved effectively. The simulation results show that with the assistance of optimal selected relays, the improved cooperative cellular system capacity with multi-relay AF transmission scheme performs better than single-hop cellular system.     

论扩音机与喇叭的阻抗匹配

本文论述扩音机与喇叭阻抗匹配的机理以及如何正确掌握扩音机与喇叭阻抗匹配的方法