几年前很多人认为无线电频谱几乎已没有未用的波段．但广阔的空间令我们可以打破这一局限．进一步扩大宽带通信的覆盖范围。美国国家半导体提供了一系列型号齐备的芯片产品及完善的技术支持．帮助厂商及网络运营商实现移动电话的宽带通信。当数据传输率提高一倍,所需的蜂窝状小区便要多50％．同时载波频率提高．信号的穿透能力下降．被建筑及其他障碍物遮挡的地方则会难以接收信号。目前,调制及编码技术已将频谱使用效 A few years ago many people thought that there were almost no unused bands in the radio spectrum. But a vast space allows us to break this limitation. Further expand the coverage of broadband communications. National Semiconductor provides a full range of chip models and complete technical support. Help manufacturers and network operators to achieve broadband communication in mobile phones. When the data transmission rate is doubled, the required cell area will be 50% more. While increasing the carrier frequency. Signal penetration decreased. Where buildings and other obstructions are obscured, it is difficult to receive signals. At present, the modulation and coding techniques have been used spectrum efficiency