| 摘要 |
A signal to be discriminated of frequency f1 and a reference signal of frequency f2 are applied to a mixer which outputs two quadrature phase related, reversible beat frequency signals ea and eb, in accordance with the frequency conditions of f1 < f2 or f1 > f2. The signals ea and eb are coded into two level signals as to their respective levels. A phase discrimination circuit receives the signals ea and eb and outputs an AC signal at the beat frequency, selectively at one or the other of its two output terminals in accordance with a leading or lagging (delayed) phase relation of one beat frequency signal relative to the other, the phase of which is taken as a reference. The phase discrimination circuit includes a memory circuit which stores the condition of the levels of the level coded signals ea and eb occurring during a predetermined one-fourth period of a cycle and produces a corresponding output. Means then respond to the memory output and at least one of the beat frequency signals to produce an output indicative of the leading or lagging phase relation of one beat frequency signal relative to the other. |
