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US 6,549,066 B1Granted
Efficient implementation of a complex filter with on chip resistor tuning
AssigneeNational Semiconductor Corporation
InventorBrian Martin
Life of this patent
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Abstract
An apparatus is disclosed for implementing a complex filter of the type represented by a transfer function having a complex pole. The apparatus is capable of creating real and imaginary parts, Yr and Yi, of a complex output signal in response to receiving real and imaginary parts, Xr and Xi, of a complex input signal. The apparatus comprises a plurality of variable resistors that may be tuned to adjust various operating parameters of the complex filter.
Claims22
An apparatus for implementing a complex filter represented by a transfer function having a complex pole in the form:
- H ( j ω ) = A s + ( p ± j q )
- said apparatus comprising:
- an operational amplifier capable of creating an output signal −Yr where Yr is a real part of a complex output signal, said operational amplifier having a capacitor that couples an output terminal of said operational amplifier and an input terminal of said operational amplifier;
- an input circuit for providing an input signal to said operational amplifier wherein said input circuit comprises a first resistor having resistance R1, a second resistor having resistance R2, a third resistor having resistance R3, and a fourth resistor having resistance R4, said first, second, third, and fourth resistors connected in parallel,
- wherein said first resistor receives an input value of Xr where Xr is a real part of a complex input signal;
- wherein said second resistor receives an input value of −Yr where Yr is a real part of a complex output signal;
- wherein said third resistor receives an input value of Yi where Yi is an imaginary part of a complex output signal;
- and
- wherein said fourth resistor receives an input value of −Yi where Yi is said imaginary part of a complex output signal.
6 more elements
An apparatus for implementing a complex filter represented by a transfer function having a complex pole in the form:
- H ( j ω ) = A s + ( p ± j q )
- said apparatus comprising:
- an operational amplifier capable of creating an output signal −Yi where Yi is an imaginary part of a complex output signal, said operational amplifier having a capacitor that couples an output terminal of said operational amplifier and an input terminal of said operational amplifier;
- an input circuit for providing an input signal to said operational amplifier wherein said input circuit comprises a first resistor having resistance R1, a second resistor having resistance R2, a third resistor having resistance R3, and a fourth resistor having resistance R4, said first, second, third, and fourth resistors connected in parallel,
- wherein said first resistor receives an input value of Xi where Xi is an imaginary part of a complex input signal;
- wherein said second resistor receives an input value of −Yi where Yi is an imaginary part of a complex output signal;
- wherein said third resistor receives an input value of ∓Yr where Yr is a real part of a complex output signal;
- and
- wherein said fourth resistor receives an input value of −Yr where Yr is a real part of a complex output signal.
6 more elements
An apparatus for implementing a complex filter represented by a transfer function having a complex pole in the form:
- H ( j ω ) = A s + ( p ± j q )
- said apparatus comprising:
- a first operational amplifier that creates an output signal −Yr where Yr is a real part of a complex output signal, said first operational amplifier having a first capacitor that couples an output terminal of said first operational amplifier and an input terminal of said first operational amplifier;
- a first input circuit for providing an input signal to said first operational amplifier wherein said first input circuit comprises a first resistor having resistance R1, a second resistor having resistance R2, a third resistor having resistance R3, and a fourth resistor having resistance R4, said first, second, third, and fourth resistors connected in parallel,
- wherein said first resistor receives an input value of Xr where Xr is a real part of a complex input signal;
- wherein said second resistor receives an input value of −Yr where Yr is a real part of a complex output signal;
- wherein said third resistor receives an input value of ±Yi where Yi is an imaginary part of a complex output signal;
- and
- wherein said fourth resistor receives an input value of −Yi where Yi is an imaginary part of a complex output signal;
- and
- a second operational amplifier that creates an output signal −Yi where Yi is an imaginary part of a complex output signal, said second operational amplifier having a second capacitor that couples an output terminal of said second operational amplifier and an input terminal of said second operational amplifier;
- a second input circuit for providing an input signal to said second operational amplifier wherein said second input circuit comprises a fifth resistor having resistance R1, a sixth resistor having resistance R2, a seventh resistor having resistance R3, and an eighth resistor having resistance R4, said fifth, sixth, seventh, and eighth resistors coupled in parallel,
- wherein said fifth resistor receives an input value of Xi where Xi is an imaginary part of a complex input signal;
- wherein said sixth resistor receives an input value of −Yi where Yi is an imaginary part of a complex output signal;
- wherein said seventh resistor receives an input value of Yr where Yr is a real part of a complex output signal;
- and
- wherein said eighth resistor receives an input value of −Yr where Yr is a real part of a complex output signal.
14 more elements
An apparatus for implementing a complex filter represented by a transfer function having a complex pole in the form:
- H ( j ω ) = A s + ( p ± j q )
- said apparatus comprising:
- an operational amplifier that creates an output signal −Yr on an inverting output of said operational amplifier where Yr is a real part of a complex output signal, said operational amplifier having a first capacitor that couples an inverting output terminal of said operational amplifier and an inverting input terminal of said operational amplifier;
- a first input circuit for providing an input signal to said inverting input terminal of said operational amplifier wherein said first input circuit comprises a first resistor having resistance R1, a second resistor having resistance R2, a third resistor having resistance R3, and a fourth resistor having resistance R4, said first, second, third, and fourth resistors connected in parallel,
- wherein said first resistor receives an input value of Xr where Xr is a real part of a complex input signal;
- wherein said second resistor receives an input value of −Yr where Yr is a real part of a complex output signal;
- wherein said third resistor receives an input value of ±Yi where Yi is an imaginary part of a complex output signal;
- and
- wherein said fourth resistor receives an input value of −Yi where Yi is an imaginary part of a complex output signal;
- and
- wherein said operational amplifier is capable of creating an output signal +Yr on a non-inverting output of said operational amplifier where Yr is a real part of a complex output signal, said operational amplifier having a second capacitor that couples a non-inverting output terminal of said operational amplifier and a non-inverting input terminal of said operational amplifier;
- a second input circuit for providing an input signal to a non-inverting input of said operational amplifier wherein said second input circuit comprises a fifth resistor having resistance R1, a sixth resistor having resistance R2, a seventh resistor having resistance R3, and an eighth resistor having resistance R4, said fifth, sixth, seventh, and eighth resistors coupled in parallel,
- wherein said fifth resistor receives an input value of −Xr where Xr is a real part of a complex input signal;
- wherein said sixth resistor receives an input value of Yr where Yr is a real part of a complex output signal;
- wherein said seventh resistor receives an input value of ±t Yi where Yi is an imaginary part of a complex output signal;
- and
- wherein said eighth resistor receives an input value of Yi where Yi is an imaginary part of a complex output signal.
14 more elements
An apparatus for implementing a complex filter represented by a transfer function having a complex pole in the form:
- H ( j ω ) = A s + ( p ± j q )
- said apparatus comprising:
- an operational amplifier that creates an output signal −Yi on an inverting output of said operational amplifier where Yi is an imaginary part of a complex output signal, said operational amplifier having a first capacitor that couples an inverting output terminal of said operational amplifier and an inverting input terminal of said operational amplifier;
- a first input circuit for providing an input signal to said inverting input terminal of said operational amplifier wherein said first input circuit comprises a first resistor having resistance R1, a second resistor having resistance R2, a third resistor having resistance R3, and a fourth resistor having resistance R4, said first, second, third, and fourth resistors connected in parallel,
- wherein said first resistor receives an input value of Xi where Xi is an imaginary part of a complex input signal;
- wherein said second resistor receives an input value of −Yi where Yi is an imaginary part of a complex output signal;
- wherein said third resistor receives an input value of ∓Yr where Yr is a real part of a complex output signal;
- and
- wherein said fourth resistor receives an input value of −Yr where Yr is a real part of a complex output signal;
- and
- wherein said operational amplifier is capable of creating an output signal +Yi on a non-inverting output of said operational amplifier where Yi is an imaginary part of a complex output signal, said operational amplifier having a second capacitor that couples a non-inverting output terminal of said operational amplifier and a non-inverting input terminal of said operational amplifier;
- a second input circuit for providing an input signal to a non-inverting input of said operational amplifier wherein said second input circuit comprises a fifth resistor having resistance R1, a sixth resistor having resistance R2, a seventh resistor having resistance R3, and an eighth resistor having resistance R4, said fifth, sixth, seventh, and eighth resistors coupled in parallel,
- wherein said fifth resistor receives an input value of −Xi where Xi is an imaginary part of a complex input signal;
- wherein said sixth resistor receives an input value of Yi where Yi is an imaginary part of a complex output signal;
- wherein said seventh resistor receives an input value of ±Yr where Yr is a real part of a complex output signal;
- and
- wherein said eighth resistor receives an input value of Yr where Yr is a real part of a complex output signal.
14 more elements
Dependencies are inferred from the claim text.