| 摘要 |
<p>An improvement to the reflective multistrip coupler of the surface acoustic wave device described in EPA No. 0098661 for overcoming the k-determined bandwidth limitation wherein, instead of being uniform, the electrode spacing is varied correspondingly along the input and output arrays of the coupler with the result that different frequency bands will be reflected by different groups of electrodes, and at least two reflective couplers (24, 25) with complementary spacing variations are included in the path coupling the input and output transducers (2, 3) so that all frequencies in the overall passband have substantially the same overall time delay. Contiguous bands of frequencies F,, f2, f3, f4, may be reflected by individual related groups 26, 27, 28, 29, of uniformly spaced electrodes forming either a monotonic or a permutated sequence, or the spacing can be varied continuously and monotonically.</p> |
