Mediumfrequencies and horizontal magnetic dipoles (vertical loop antennas) can be used in underground radio communication in mining sections of coal mines.
中频频率和水平磁偶极子天线(垂直环状天线)是井下采区无线通信可使用的频段和天线型式。
2
The propagation velocity of elastic wave with different frequencies in same medium is various, which is called dispersive problem of frequency.
相同介质中不同频率的弹性波传播速度是有差异的，即频散问题。
3
One embodiment of the present invention transmits ultra-wideband signals that occupy radio frequencies that are not used by other electromagnetic signals present in a wire medium of interest.