A crop harvesting header for mounting on a propulsion vehicle such as a swather tractor or combine harvester includes a main frame structure supporting a crop receiving table with a cutter bar across a front of the table and side drapers on the table for moving the cut crop toward a discharge location of the header. A thickness of at least one of the front glass substrate and the back glass substrate is 2. A carrier period integration circuit 106 integrates the multiplication result with respect to the period of the carrier, and the integration result is then binarized in a discriminator 107, thereby realizing demodulation.