Demodulating apparatus and demodulating method
View Patent ↗This invention relates to a demodulating apparatus and a demodulating method for demodulating an input signal more quickly than before when the channels of the input signal are inverted. A correlator 152 calculates a correlation value indicative of the correlation between a known delayed detection sequence made of symbols of correct delayed detection values of a known sequence inserted in the input signal and a received delayed detection sequence obtained through delay detection of the input signal. If the imaginary part of the correlation value is less than zero, a channel control section 132 switches the channels of the input signal before feeding the signal to a frame synchronization circuit 122 . This invention can be applied illustratively to a satellite broadcast receiving apparatus.
1. A demodulating apparatus for demodulating an input signal split into an in phase (I)-channel signal and an orthogonal(Q)-channel signal, said demodulating apparatus comprising:
correlation detection means for calculating a correlation value between a known sequence made of symbols of known values inserted in said input signal and a received sequence formed by the symbols obtained by detecting said input signal, and
channel control means for switching the channels of said input signal if the correlation between said known sequence and said received sequence corresponding to said known sequence is found to be a negative correlation.
2. The demodulating apparatus according to claim 1 , wherein, if frame synchronization of said input signal is not established within a predetermined time period after the channels of said input signal have been switched, then said channel control means again switches the channels of said input signal.
3. The demodulating apparatus according to claim 1 , further comprising:
confidence level determination means for determining the confidence level of said correlation value based on the magnitude of said correlation value;
wherein, if the confidence level of said correlation value is not determined to be sufficient, then said channel control means switches said channels on the basis of the result of decoding synchronization of said input signal.
4. The demodulating apparatus according to claim 1 , wherein said known sequence is modulated through π/2 shift BPSK (Binary Phase Shift Keying) when inserted into said input signal.
5. The demodulating apparatus according to claim 4 , further comprising:
confidence level determination means for determining the confidence level of said correlation value based on the magnitude of a deflection angle of said correlation value;
wherein, it the confidence level of said correlation value is not determined to be sufficient, then said channel control means switches said channels on the basis of the result of decoding synchronization of said input signal.
6. A demodulating method for use with a demodulating apparatus for demodulating an input signal split into an in-phase (I)-channel signal and an orthogonal (Q)-channel signal, said demodulating method comprising the steps of:
calculating, by a processor, a correlation value between a known sequence made of symbols of known values inserted in said input signal and a received sequence formed by the symbols obtained by detecting, said input signal; and
switching the channels of said input signal if the correlation between said known sequence and said received sequence corresponding to said known sequence is found to be a negative correlation.