| 摘要 |
PROBLEM TO BE SOLVED: To quickly and accurately detect a null symbol even under any circumstance in the case of utilizing a broadcast signal including the null symbol. SOLUTION: A digital audio broadcast(DAB) broadcast signal is received and selected and the broadcast signal that is received and selected is orthogonally demodulated. An I component delay circuit 51 and a Q component delay circuit 52 delay signals I, Q obtained through orthogonal demodulation by a valid symbol to generate delay signals Id, Qd, and the correlation among the delay signals Id, Qd and the signals I, Q that are not delayed is taken. A peak discrimination circuit 56 discriminates a peak level of this correlation and a level pattern discrimination circuit 62 detects a pattern of a level of the peak value. When a peak value with a lower level is included, a time interval discrimination circuit 63 calculates a length of a period of a null symbol and discriminates whether or not the length of the null symbol period is the same as the length of the null symbol period of the received and selected DAB broadcast signal to detect the position of the null symbol. |
