| 摘要 |
PURPOSE: To realize a high transmission speed for a communication system by selecting pair number of interdigital electrode pairs of a coding electrode corresponding to one code to be more than one pair and to be less than a ratio of a carrier frequency to a chip rate. CONSTITUTION: An interdigital input electrode 2 made of a material such as Al formed by using the photo lithography technology, an output coding electrode 3 apart by a prescribed interval from the input electrode 2, and a sound absorption section 4 outside the input electrode 2 and the coding electrode 3 are formed on a crystal substrate 1. Then number of pairs of interdigital electrode pairs corresponding to each code of the coding electrode 3 is selected to be more than one pair and to be less than a frequency depending the speed of the surface acoustic wave in use and the interval of the interdigital electrodes, that is, a carrier frequency, and a frequency depending on the interval of the interdigital electrode pairs corresponding to each code of the coding electrode 3, that is, a chip rate. Thus, the efficiency is enhanced (by 2dB for 4 pairs) and waveform distortion is reduced (nearly -6dB for 4 pairs). |
