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US 9,184,729 B2Granted
Reconfigurable Nth-order filter
AssigneesKing Fahd University of Petroleum and Minerals, King Abdulaziz City for Science and Technology
InventorHussain Alzaher
Life of this patent
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Abstract
The reconfigurable Nth-order filter includes a CCII adopting active current division networks for implementing the proposed filter. This digitally programmable second generation current conveyor leads to wide control of filter coefficients for reconfiguration of the filter. Programmability characteristics are demonstrated through experimental results obtained from integrated circuit chips fabricated in a 0.18 μm CMOS process.
Claims16
A reconfigurable Nth-order filter, comprising:
- a filter stage which includes a second generation current conveyor (CCII) having a y input, an x input, first, second, and third current sense non-inverting outputs, for all stages except a first of said filter stage, second current sense non-inverting output connected to an ungrounded lead of a capacitor portion of a passive circuit having a time constant τi;
- the filter stage further including a first current division network (CDN) having an analog input, an analog output, and a digital control input βb, the first current sense non-inverting CCII output being connected to the first CDN analog input;
- the filter stage further including a first digitally controlled current follower (DCCF) having an input, a digital control input αb, and for all stages except a last said filter stage an inverting output connected to a current source bi, output of the first CDN being connected to the first DCCF input;
- the filter stage further including a second CDN having an analog input, an analog output, and a digital control input βa, the third current sense non-inverting CCII output being connected to the second CDN analog input;
- the filter stage further including a second DCCF having an input, a digital control input αa, and an inverting output connected to a current source ai, output of the second CDN being connected to the second DCCF input;
- a cascade connection of said filter stages, for all stages except a last stage, said passive circuit being formed by a capacitor connected between the y input of the stage and ground, and a resistor connected between the x input of the stage and ground;
- except for the last stage, said first DCCF outputs of the stages being connected to each other in a feedback loop, said feedback loop connecting the current source bi and terminating at the x input of the last stage, the x input accepting an input signal is;
- said second DCCF outputs of the stages being connected to each other in a feedforward configuration, the first stage delivering an output signal iout;
- and
- wherein the reconfigurable Nth-order filter is defined by a pair of transfer functions characterized by the equations,
- i
- m
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- (
- s
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- i
- s
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- s
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- α
- am
-
- s
- i
-
- Π
- i
- =
- m
- n
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- 1
-
- 1
- C
- i
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- 1
-
- R
- i
- s
- n
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- Σ
- i
- =
- 0
- n
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- β
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- α
- bi
-
- s
- i
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- Π
- j
- =
- i
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- 1
-
- 1
- C
- j
- +
- 1
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- ,
- and
- i
- n
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- i
- s
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- s
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- an
- s
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- n
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-
- α
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- i
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- =
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- .
144 more elements
Dependencies are inferred from the claim text.