| 摘要 |
PROBLEM TO BE SOLVED: To stably enable a reception even when a noise characteristic is excellent and the level of a reception signal is low, in a digital radio transmitter/ receiver. SOLUTION: This device is provided with a costas loop 30 generating the reference carrier wave signal necessary for the operation in a synchronizing detection system, a delay element 4 generating the reference carrier wave signal necessary for the operation in a delay detection system, a changeover switch 11 switching the reference carrier wave signals due to these parts and a switching control circuit 15 controlling this changeover switch 11. When the level of a reception signal is large, the output of the costas loop 30 is selected and the operation in the synchronizing detection system is made to be performed. When the reception level is small, the output of the delay element 40 is selected and the operation is made to be performed in the delay detection system. Thus, even when a signal to noise characteristic is excellent and the reception level is lowered by the extension of a simple switching circuit, a detection circuit device which is capable of performing a reception and has high performance and high reliability can be easily obtained. |
