| 摘要 |
The invention concerns a signal frequency processing device for measuring the frequency of an input signal, wherein the frequency is so much processed that it can be used for producing a TTL-compatible signal. The input signal is mixed with the frequency of a frequency generator and filtered by a band pass filter having a predetermined centre frequency. The resulting signal is mixed again with the oscillator signal of the frequency generator to provide a second intermediate signal. When this second intermediate signal has been passed through a second band pass filter an output signal is obtained which directly corresponds to the input frequency. Unlike in prior art, the control voltage of the frequency generator is not measured and evaluated as an output quantity, but instead the second intermediate frequency obtained in the second mixer.
|
