| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem in which conventional echo detection using a discrete Fourier transform after conversion into a digital signal to process a received echo requires complicated processing and large circuitry.SOLUTION: An echo detection circuit 200 detects an echo by detecting the magnitude of a digitally mixed representation of a received acoustic signal and reference sine and cosine signals. That magnitude is then compared 235 against an echo threshold to verify the presence or absence of an echo signal. A low pass filter 233A, 233B with a configurable cut-off frequency may be used to define the selectivity of the echo detector. |
