PURPOSE: To contrive the improvement of interference and interruption characteristics while a comparatively wide band filter, which is available actually, can be provided at a receiving input means by preventing the overlapping of a frequency which can be selected by respective filters in the same time period as the change-over sequence of the frequency.

CONSTITUTION: After a frequency hopping signal inputted from a receiving input terminal 1 passes through an RF filter group 2 having respective frequency bands shown by FL1, FL2,∼FLM, the signal is supplied to an RF amplifier 3. Here, the RF filter group 2 is composed of the M pieces of filters and changed over with a switch corresponding to the hopping. The band width of respective filters includes the N pieces of hopping frequency groups, and a frequency hopping sequence is controlled so as to select only one of f1, f2,..., fN out of one filter in the same time period. Consequently, when the synchronization of the time period is obtained during the transmitting and receiving, one (f) can be selected from one filter in the same time period.