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Title: Digitally tuned circuit including switching of bank capacitors between plural tuned circuits
Claims: What is claimed is: 1. An electrically tunable filter system comprising at least two filter portions having signal inputs and signal outputs and adapted to respond to an input signal supplied at said signal input for filtering said signal so that only those components of said input signal which are within a selected frequency range appear at said signal output, each of said filter portions further having a tuning input to which a capacitive impedance is to be connected for setting said selected frequency range; capacitive impedance means comprising plural individual capacitor elements and first controllable coupling means responsive to a first control signal for controllably coupling a selected combination of said capacitor elements to a capacitive impedance output; filter system input and output means; second controllable coupling means responsive to a second control signal for selectively coupling said signal input and signal output of a selected filter portion to said filter system input means and filter system output and for also coupling said capacitive impedance output of said capacitive impedance means to said tuning input of said selected filter portion; means for providing a frequency selection signal indicative of a selected frequency range; and, filter control means responsive to said frequency selection signal for providing said first and second control signals in accordance therewith so as to couple a selected combination of said capacitor elements to said capacitive impedance output, and so as to further couple a selected filter portion to said system input and output, and said capacitive impedance means to said tuning input of said selected filter portion whereby said selected frequency range of said filter system is automatically set into said filter system in accordance with said frequency selection signal. 2. An electrically tunable filter system as set forth in claim 1, wherein each of said filter portions includes at least two tuned circuits, each having a said tuning input, wherein said capacitive impedance means comprises at least two capacitor banks each including plural individual capacitor elements and a corresponding said capacitive impedance output, and wherein said second controllable coupling means serves to couple said capacitive impedance outputs of each of said at least two capacitor banks to a corresponding said tuning input of said selected filter portion. 3. An electrically tunable filter system as set forth in claim 1, wherein said filter control means includes storage means having stored at addressable positions therein coded signals indicative of all permissible values of said first and second control signals, addressing means responsive to said frequency selection signal for addressing said storage means so as to recover therefrom selected ones of said coded signals, and means responsive to said recovered coded signals for providing first and second control signals in accordance therewith. 4. An electrically tunable filter system as set forth in claim 3, wherein said storage means comprises a programmable logic array having said coded signals programmed at addressable locations therein, said coded signals corresponding directly to said first and second control signals such that said programmable logic array has directly stored therein coded signals corresponding to all permissible values of said control signals. 5. An electrically tunable filter system as set forth in claim 4, wherein each of said coded signals is stored at an address having a value directly related to the value of the center tuning frequency of said electrically tunable filter system which would result if said coded signal were addressed, and wherein said addressing means comprises means responsive to said frequency selection signal for providing a corresponding said address. 6. An electrically tunable filter system as set forth in claim 1, wherein said filter control means comprises programmable computer means programmed to respond to said frequency selection signal for deriving therefrom the first and second control signals which will provide said tunable filter system with a center tuning frequency most nearly corresponding to said selected frequency. 7. An electrically tunable filter system as set forth in claim 1, and further comprising input overload protection means associated with said filter system input for blocking the supply of those signals to said filter system which could potentially damage said filter system, and output overload protection means associated with said filter output for blocking the supply of those signals appearing at said filter output which could potentially damage an output circuit to which said signals would otherwise be directed. 8. An electrically tunable filter system as set forth in claim 1, and further comprising fixed filter means and third controllable coupling means responsive to a third control signal for selectively coupling said fixed filter between said filter system input and filter system output, and wherein said filter control means is further responsive to said frequency selection signals to provide said third conrol signals so as to cause said fixed filter means to be coupled between said filter system input and output when said selected frequency range falls outside of the frequency ranges obtainable through use of said filter portions and within the range of said fixed filter means. Other info: Inventors: Luhowy, Gabriel J. (Lima, NY, US) Application Number: 832680 Filing Date: 1977-09-12 Publication_date: 1979-02-06 Assignee: Harris Corporation (Cleveland, OH) Primary Class(es): 334/55 327/99, 327/552, 333/177, 334/11, 334/19, 455/173.1, 455/217, 455/289, 455/291 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Gensler, Paul L. Assistant Examiner: Attorney: |
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