| 摘要 |
A frequency detector circuit mixes two reference signals (in quadrature) with the input signal. The resulting signal is fed to a band limiter (16,17) and the output of the latter goes to an amplitude analyser (18,19) which detects the presence or absence of the sought frequency. Two further reference signals (4,5) in quadrature are mixed with the input signal and the resulting signal goes to a second band limiter (6,7). The signals from the latter are squared and added (8,9,10). The reference signals are produced by an oscillator (22) connected by frequency dividers (23,24) to two phase shifters (25,26). |
