Filter switching arrangement for a tuner
AssigneeRCA Licensing Corporation
InventorWilliam D. Anderson
Life of this patent
Estimating the term…
Abstract
In a tunable filter including first and second inductors, a varactor diode, and a bandswitching diode connected intermediate the inductors to select the inductor configuration for first and second tuning bands, a capacitor is connected in parallel with the bandswitching diode. When the bandswitching diode is in the high impedance "non-conducting" state, the capacitor is functionally connected with other elements of the tunable filter for purposes such as trapping or tracking. When the bandswitching diode is in the low impedance "non-conducting" state, the capacitance is functionally disconnected from the tunable circuit.
Claims21
Tuning apparatus for tuning channels with respective RF signals occurring in first and second frequency bands comprising:
- a RF signal input;
- a RF signal output;
- tunable filter means coupled between said RF signal input and said RF signal output and having a frequency selective response characteristic controlled in response to a tuning control signal representing a channel to be tuned for allowing the RF signal corresponding to the channel to be tuned to pass from said RF signal input to said RF signal output;
- said tunable filter means including a variable capacitance element responsive to said tuning control signal, first and second inductance elements, and a bandswitching diode having a high impedance state and a low impedance state selectable in response to a bandswitching signal representing the frequency band of the selected channel and connected to a point intermediate said first and second inductance elements for forming a first configuration of said tunable filter means including both of said first and second inductance elements for tuning channels in said band when in said high impedance state and for forming a second configuration of said tunable filter means including one but not the other of said second inductance elements for tuning channels in said second band when in said low impedance state;
- and
- a second capacitance element connected in parallel with said bandswitching diode to be functionally connected to said tunable filter means when said bandswitching diode is in said high impedance state and to be functionally disconnected from said tunable filter means when said bandswitching diode is in said low impedance state.
Tuning apparatus for tuning channels in lower and upper frequency bands comprising:
- a RF signal input;
- a RF amplifier having an input;
- a tunable filter coupled between said RF signal input and said input of said RF amplifier including first and second inductance elements connected in series, in the order named, between a point of reference and said RF signal input;
- third and fourth inductance elements and a varactor diode responsive to a tuning voltage connected in series, in the order named, between said RF signal input and said input of said RF amplifier;
- a bandswitching diode responsive to a bandswitching signal connected between a point intermediate said first and second inductance elements and a point intermediate said third and fourth inductance elements;
- said bandswitching diode being rendered non-conductive when a channel in said lower frequency band is selected for tuning and being rendered conductive when a channel in said upper frequency band is selected for tuning;
- and
- a capacitance element connected in parallel with said bandswitching diode.
Tuning apparatus for tuning channels in first and second frequency bands comprising:
- a tunable circuit including first and second inductance elements connected in series and a varactor diode responsive to a tuning control voltage;
- bandswitching means having a high impedance state and a low impedance state selectable in response to a bandswitching signal and connected to a point intermediate said first and second inductance elements for configuring said tunable circuit for tuning channels in said first band when in said high impedance state and for configuring said tunable circuit for tuning channels in said second band when in said low impedance state;
- and
- an additional reactance element connected in parallel with said bandswitching means.
Tuning apparatus, comprising:
- a tuned circuit including a variable capacitance element controllable in response to a tuning control signal, and at least first and second inductance elements;
- bandswitching means having a high impedance state and a low impedance selectable in response to a bandswitching signal and connected to at least one of said first and second inductance elements for selectively changing the inductance of said tuned circuit in response to said bandswitching signal:
- and
- an additional capacitance element connected in parallel with said bandswitching means to be functionally connected to said tuned circuit when said bandswitching means is in said high impedance state and functionally disconnected from said tuned circuit when said bandswitching means is in said low impedance state.
Dependencies are inferred from the claim text.