| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a method that accurately detects a level of a communication signal and accurately detects propriety of reception of digital broadcasting or even communication as well as analog broadcasting at a high speed. <P>SOLUTION: A low pass filter 3 cuts off frequencies of an object signal in excess of a frequency Fd being an integer multiple (twice or over) of a center frequency Fb of the object signal, a splitter 4 splits an output of the filter 3 into two, a λ/2 delay line 5 delays one of the split outputs by a half of a wavelength λb with respect to the center frequency Fb, that is, λb/2, and a DBM (double balanced mixer) 6 multiplies the delayed output with the other output not delayed to provide an output of the product. Another low pass filter 7 smoothes the output of the product. <P>COPYRIGHT: (C)2004,JPO |
