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Title: Circuit arrangement for digital frequency indication in a radio receiver
Claims: 1. In a circuit arrangement for digitally indicating the frequency to which a radio receiver having both an AM tuning oscillator and an FM tuning oscillator is tuned, said circuit arrangement including amplifying means, means for coupling the output signals from said AM and FM oscillator to the input of said amplifying means, means for converting the amplified output signals from said oscillators into rectangular signals, electronic counting means for counting the frequency of the rectangular signals and means responsive to the output signals from said counting means for providing a digital indication of the frequency to which the particular tuning oscillator is tuned, the improvement wherein said amplifying means comprises a common broadband amplifier having a bandwidth which is sufficiently broad so as to pass and amplify signal frequencies from both the AM and FM tuning oscillators; and wherein said coupling means comprises means for sufficiently loosely coupling the output signals of said AM tuning oscillator and of said FM tuning oscillator to the common input of said broadband amplifier so that said tuning oscillators are not noticeably detuned by changes in capacity in said broadband amplifier. 2. A circuit arrangement as defined in claim 1 wherein said means for loosely coupling the output signals of said AM tuning oscillator and of said FM tuning oscillator to said common input of said broadband amplifier comprises first and second capacitors each having one end connected to the output of a respective one of said tuning oscillators and its other end connected to a common connection point, and a common coaxial line connecting said common connection point to said input of said broadband amplifier. 3. A circuit arrangement as defined in claim 2 wherein said means for loosely coupling further includes a third capacitor connected between said common connecting point and ground. 4. A circuit arrangement as defined in claim 1, wherein said means for loosely coupling the output signals of said AM tuning oscillator and of said FM tuning oscillator does so in a low-ohmic manner and comprises first and second series connected inductances with each of said inductances being inductively coupled to one of said tuning oscillators, one end of said series connected inductances being connected with said common input of said common broadband amplifier, and the other end being connected to ground. 5. A circuit arrangement as defined in claim 1 wherein said means for converting includes means in said broadband amplifier for limiting the amplitude of the oscillations to transform same into rectangular oscillations. 6. A circuit arrangement as defined in claim 5 further including means for superimposing a direct current component on the rectangular output signals at the output of said broadband amplifier. 7. A circuit arrangement as defined in claim 1 wherein the operating voltage of said broadband amplifier simultaneously serves as the operating voltage for said electronic counter means. 8. A circuit arrangement as defined in claim 1 wherein said electronic counter means includes a frequency divider connected to the output of said broadband amplifier and having a plurality of dividing stages, wherein the first dividing stage of said frequency divider has a dividing ratio of 1:2 or 1:4 and wherein a second dividing stage with a dividing ratio of 1:5 or 1:25 is connected in series with said first dividing stage in order to produce a full decimal dividing ratio. 9. A circuit arrangement as defined in claim 8 wherein decimal dividers are used to produce said dividing ratio of 1:5 or 1:25, respectively, the oscillations being fed in at the input of the first flip stage and being obtained at the output of the second flip stage. 10. A circuit arrangement as defined in claim 8 wherein said frequency divider additionally includes a third dividing stage with a dividing ratio of 1:10, and a controllable switch means for connecting the input of said further dividing stage to either the output of said first dividing stage or the output of said second dividing stage. Other info: Inventors: Klank, Otto (Arpke, DT) Rottmann, Dieter (Misburg, DT) Application Number: 526052 Filing Date: 1974-11-21 Publication_date: 1976-04-06 Assignee: Licentia Patent-Verwaltungs-G.m.b.H. (Frankfurt am Main, DT) Primary Class(es): 455/144 455/158.3 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Mayer, Albert J. Assistant Examiner: Attorney: Spencer & Kaye |
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