论文部分内容阅读
在任何纬度地区,全球手持设备用户都可借助铱星网络的66颗商业卫星使用陆海移动卫星通信(简称Sotm)服务,但是数据调用速率较低,只能达到2.4~10kb/s。宽带卫星通信要求更高频率,比如甚高频波段(300MHz~3GHz)、X波段(8~12GHz)、Ku波段(12~18GHz)以及Ka波段(26.5~40GHz)。另外,它还须有窄束高增益天线,必须时刻精确指向卫星方向,而这是车载通信系统的工程难题,因为即使车辆行驶在崎岖道路上,也要保持信号连接。
At any latitude, users of handheld devices worldwide can use land-mobile satellite communications (Sotm) service with 66 commercial satellites on the Iridium satellite network, but the data transfer rate is low, which can only reach 2.4 ~ 10kb / s. Broadband satellite communications require higher frequencies such as the VHF band (300MHz-3GHz), the X-band (8-12GHz), the Ku-band (12-18GHz) and the Ka-band (26.5-40GHz). In addition, it requires a narrow-beam, high-gain antenna that must always be pointed at the satellite, which is an engineering challenge for on-board communication systems because signal connections must be maintained even when the vehicle is on a rough road.