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US 7,583,127 B2Granted
High Q linear controlled variable capacitor using translinear amplifier
AssigneeDialog Semiconductor GmbH
InventorsAndreas Sibrai, Josef Niederl
Life of this patent
Estimating the term…
Abstract
A voltage controlled variable capacitor, formed of a larger number of fixed capacitor segments and a corresponding number of switching elements, uses translinear amplifiers to control each switching element. Each translinear amplifier linearly switches from the fully off to the fully on state; a minimum number of switching stages (ideally only one) is in the mode-of-change at any one time with a minimum overlap. The arrangement achieves a nearly linear change of capacitance at linear tuning voltage change, while resulting in high Q-factor due to the low RDSon and high RDSoff of the fully switched stages. The invention eliminates temperature and voltage dependencies of other solutions like varactor diodes.
Claims47
A circuit to control the capacitance of a variable capacitor in a strictly linear mode through a steady tuning voltage and to achieve a high Q-factor at the same time;
- comprising:
- a set of individual small capacitors;
- a set of capacitor switching stages, each stage comprising;
- a switching device, allowing a steady ramp-up/ramp-down phase between the points of being fully switched on and fully switched off, and where said switching device is connected in series with one of said capacitors, to connect a multiple of said capacitors in parallel;
- a circuit to control the switching operation of said switching device in a steady ramp-up/ramp-down manner between the points of being fully switched on and fully switched off, comprising:
- a translinear amplifier to produce a ramp-up/ramp-down signal for said switching device, where said translinear amplifier is implemented within said circuit to control the switching operation;
- a common circuit to provide a set of input and output reference levels for each of said capacitor switching stages, used as input reference levels and output reference levels for each of said translinear amplifiers, comprised within said circuits to control the switching operation;
- and
- input signals, each dependent on the tuning voltage, dedicated for the voltage controlled capacitance change, provided to an input of all of said capacitor switching stages.
6 more elements
A circuit to control the capacitance of a variable capacitor in a strictly linear mode through a steady tuning voltage and to achieve a high Q-factor at the same time, by controlling a multiple of switching devices through steady control signals when said switching devices operate within their steady ramp-up/ramp-down area and by sharply cutting off the control signals, when said switching devices operate outside their steady ramp-up/ramp-down area;
- comprising:
- a set of individual small capacitors;
- a set of capacitor switching stages, each stage comprising:
- a switching device allowing said steady ramp-up/ramp-down phase between the points of being fully switched on and fully switched off, and where said switching device is connected in series with one of said capacitors, to connect a multiple of said capacitors in parallel;
- a circuit to control the switching operation of said switching device in a steady ramp-up/ramp-down manner, comprising:
- a translinear amplifier to produce a steady ramp-up/ramp-down signal for said switching device, where said translinear amplifier is implemented within said circuit to control the switching operation;
- a first cut-off circuit to drive said switching device to a fully on status, when said switching device operates outside said steady ramp-up/ramp-down area on said switching device's low resistance side, and implemented in combination with said translinear amplifier;
- a second cut-off circuit to drive said switching device to a fully off status, when said switching device is beyond said steady ramp-up/ramp-down area on said switching device's high resistance side, and implemented in combination with said translinear amplifier;
- a common circuit to provide a set of input and output reference levels for each of said capacitor switching stages, used as input reference levels and output reference levels for each of said translinear amplifiers, comprised within said circuits to control the switching operation;
- and
- input signals, each dependent on the tuning voltage, dedicated for the voltage controlled capacitance change, provided to an input of all of said capacitor switching stages.
8 more elements
A circuit to control the capacitance of a variable capacitor in a strictly linear mode through a steady tuning voltage and to achieve a high Q-factor at the same time, by controlling a multiple of capacitor switching devices through steady control signals and by compensating the temperature deviation of said capacitor switching devices;
- comprising:
- a set of individual small capacitors;
- a set of capacitor switching stages, each stage comprising:
- a switching device allowing a steady ramp-up/ramp-down phase between the points of being fully switched on and fully switched off, and where said switching device is connected in series with one of said capacitors to connect a multiple of said capacitors in parallel;
- a circuit to control the switching operation of said switching device, in a steady ramp-up/ramp-down manner, comprising:
- a translinear amplifier to produce a control signal for said switching device, and implemented within said circuit to control the switching operation;
- a temperature compensating circuit to compensate the temperature deviation of said switching device, and connected to an output reference point of said circuit to control the switching operation;
- a common circuit to provide a set of input and output reference levels for each of said capacitor switching stages, used as input reference levels and output reference levels for each of said translinear amplifiers, comprised within said circuit to control the switching operation;
- and
- input signals, each dependent on the tuning voltage, dedicated for the voltage controlled capacitance change, provided to an input of all of said capacitor switching stages.
7 more elements
A method to control the capacitance of a variable capacitor in a strictly linear mode through a tuning voltage and to achieve a high Q-factor at the same time;
- comprising:
- providing a set of individual small capacitors, a set of capacitor switching stages, each comprising:
- a switching device allowing a steady ramp-up/ramp-down phase between the points of being fully switched on and fully switched off, and where said switching device is connected in series with one of said capacitors, to connect a multiple of said capacitors in parallel, a circuit to control the switching operation of said switching device in a ramp-up/ramp-down manner between the points of being fully switched on and fully switched off and comprising a translinear amplifier, a common circuit to provide a set of input reference levels and output reference levels for said capacitor switching stages, and input signals, dependent on the tuning voltage and dedicated for the voltage controlled capacitance change;
- providing an individual input reference level and an output reference level for each capacitor switching stage;
- supplying one of said input signals, dependent on the tuning voltage, dedicated for a voltage controlled capacitance change, to all of said capacitor switching stages;
- amplifying, by means of said translinear amplifier, a difference of said tuning voltage and said input reference level within each capacitor switching stage, to produce a linear control signal for a ramp-up/ramp-down switching operation;
- fully switching on one of said switching devices in order to completely switch one of said small capacitors in parallel to the already switched on capacitors, one after the other to linearly increase the total capacitance;
- fully switching off one of said switching devices in order to completely disconnect one of said small capacitors from the other switched on capacitors, one after the other, to linearly decrease the total capacitance;
- and
- ramping up or ramping down the switching operation of one of said switching devices to partially switch, with increasing or decreasing share, one of said small capacitors in parallel to the already switched on capacitors, one after the other.
7 more elements
A method to control the capacitance of a variable capacitor in a strictly linear mode through a tuning voltage and to achieve a high Q-factor at the same time by sharply cutting off the control signal, when a switching device operates outside its steady ramp-up/ramp-down area;
- comprising:
- providing a set of individual small capacitors, a set of capacitor switching stages, each comprising:
- a switching device allowing a steady ramp-up/ramp-down phase between the points of being fully switched on and fully switched off, and where said switching device is connected in series with one of said capacitors, to connect a multiple of said capacitors in parallel, a circuit to control the switching operation of said switching device in a ramp-up/ramp-down manner between the points of being fully switched on and fully switched off and comprising, in addition to a translinear amplifier, a first cut-off circuit to drive it to a fully-on status, as well as a second cut-off circuit to drive it to a fully-off status, a common circuit to provide a set of input reference levels and output reference levels for said capacitor switching stages, and input signals, dependent on the tuning voltage and dedicated for the voltage controlled capacitance change;
- providing an individual input reference level for each capacitor switching stage;
- supplying one of said input signals, dependent on the tuning voltage, dedicated for a voltage controlled capacitance change, to all of said capacitor switching stages;
- amplifying, with said translinear amplifier, the difference of said tuning voltage and said individual input reference level within each capacitor switching stage, to produce a linear control signal for a ramp-up/ramp-down switching operation;
- steadily ramp-up/ramp-down switching on or off said switching device in order to partially switch, with increasing or decreasing share, said small capacitor in parallel to the already switched on capacitors, one after the other, to linearly increase or decrease the total capacitance;
- linearly controlling the switching function for each of said switching device with steady ramp-up/ramp-down phase, when said switching device is in its steady ramp-up/ramp-down area;
- activating said first cut-off circuit, when said switching device operates outside its steady ramp-up/ramp-down area on said switching device's low resistance side and thus taking over full control of said switching device by driving it to a fully-on state;
- and
- activating said second cut-off circuit, when said switching device is beyond its steady ramp-up/ramp-down area on said switching device's high resistance side, and thus taking over full control of said switching device by driving it to a fully-off state.
8 more elements
A method to control the capacitance of a variable capacitor in a strictly linear mode through a tuning voltage and to achieve a high Q-factor at the same time and to compensate the temperature deviation of the capacitor switching device;
- comprising:
- providing a set of individual small capacitors, a set of capacitor switching stages, each comprising:
- a switching device with steady ramp-up/ramp-down phase to continually switch on said capacitors in parallel, a circuit to control the switching operation of said switching device and comprising a translinear amplifier, a temperature compensating circuit to compensate the temperature deviation of said switching device, a common circuit to provide set of input reference levels and output reference levels for each individual capacitor switching stage, and input signals, dependent on the tuning voltage and dedicated for the voltage controlled capacitance change;
- providing an individual input reference level and an output reference level for each capacitor switching stage;
- supplying one of said input signals, dependent on the tuning voltage, dedicated for the voltage controlled capacitance change, to all of said capacitor switching stages;
- amplifying, with said translinear amplifier, the difference of said tuning voltage and said individual input reference level within each capacitor switching stage, to produce a linear control signal for a ramp-up/ramp-down switching operation;
- continually switching on one of said switching devices with steady ramp-up/ramp-down phase in order to switch one of said small capacitors in parallel to the already switched on capacitors, one after the other;
- linearly controlling the switching function for each of said switching devices with steady ramp-up/ramp-down phase;
- and
- compensating the temperature deviation of said switching device, using said temperature compensating circuit to compensate the temperature deviation of said switching device and providing a compensated output reference level to said circuit to control the switching operation.
7 more elements
Dependencies are inferred from the claim text.