| 摘要 |
<p>PURPOSE:To simply execute a frequency discrimination and also to reduce the cost of a device, by supplying two kinds of high and low local oscillation frequencies to a frequency mixer by applying a bushing voltage which ascends and descends periodically. CONSTITUTION:A first frequency converting means consisting of a first frequency mixer 13 and a first local oscillator 11 for supplying alternately two kinds of local oscillation frequencies to the mixer 13 by a bushing voltage which ascends and descends periodically converts an input frequency to the first intermediate frequency of a lower frequency. A first intermediate frequency is converted to a second intermediate frequency of a lower frequency by the second frequency converting means consisting of the second frequency mixer 19 and the second local oscillator 18 for supplying a local oscillation frequency having a sweep axis to the mixer 19 by a sweep voltage for executing a sweep synchronously with an ascent and a descent of the bushing voltage. In this state, by deciding whether a difference of periods of the second intermediate frequency, which are converted alternately is positive or negative, the input frequency is discriminated.</p> |
