| 摘要 |
PURPOSE:To improve the separation in low frequency band, by inserting a compensation filter to the detection system of a sum signal. CONSTITUTION:A cut-off frequency fc of a PM detector provided in a PM detection system 3 is selected to an arbitrary frequency in the range of 50- 100Hz. A high pass filter 10 is provided between an AM detection system 2 and a matrix circuit 4. The cut-off frequency fc and a Q are selected to match with the fc and Q of the PM detector. In this selection, an AM detection output, i.e., the amplitude characteristic of a sum signal (L+R) is arranged to the amplitude characteristic of the PM detection output, i.e., differential signal (L-R) and the level difference between the sum and difference signals is eliminated. The phase characteristic of the sum signal (L+R) determined with the fc and Q coincides with the phase characteristic of the differential signal (L-R). Thus, since the cut-off frequency of the PM detector is selected comparatively higher and the amplitude and phase characteristics coincide, the separation at low frequency band is not deteriorated. |
