| 摘要 |
PURPOSE:To simplify the circuit and to obtain a strong immunity to jamming by providing a Costas loop PLL including a narrow band loop adding offset signals for frequency hopping and the 1st and 2nd frame period control circuits. CONSTITUTION:An input signal of a reception system is multiplied (50, 51) with a signal of a voltage controlled oscillator 58, the phase difference component obtained is added (54) with a hopping pattern signal and the result is used to control an oscillator 58 thereby constituting a narrow band loop PLL and when not added, a normal Costas loop is formed. In selecting a switch 60 to the high position and the switch 61 to the open state, an FM demodulation signal passes through a correlation device 62 for frame synchronous sweep pattern signal extraction and a frame synchronous signal is extracted. Then a control circuit 66 starts a frequency hopping pattern and scramble at the initial frame synchronization and controls the changeover with a loop constant at the 2nd frame synchronization. |
