在通信系统的接收端,高放电路的作用是( )
A. 只是放大天线上接收下来的所有频道的高频信号
B. 只是从所有频道信号中进行选台
C. 将从天线上接收下来的所有频道的高频信号进行放大并选台
在通信系统的接收端,混频电路的作用是( )
A. 将高频信号转换为中频信号
B. 将高频信号转换为更高频信号
C. 将高频信号转换为低频信号
在通信系统的接收端,本振电路产生的振荡信号的频率要比送到混频器的某个频道的调制信号的载频差出一个固定的频率。( )
A. 对
B. 错
spend cost golden usual explore require experiencetemporary lifelong businessmen various develop scholarslay foundationYou will 1) ________ at least four years in college. College days will be the 2) ________ time in your life. There are many opportunities for you to 3) ________ the unknown and you can 4) ________ a lot. You can make 5) ________ friends; you can enjoy 6) ________ kinds of activities; you can 7) ________ your personal interests; and you will meet some outstanding 8) ________. Keep a good balance and 9) ________ a solid foundation. There are many doors to your dreams. You decide how many you can open.