Delta-sigma converter with bandpass filter for noise reduction in receivers
Double sampled biquad switched capacitor filter Patent #: 5495200
ApplicationNo. 585469 filed on 01/16/1996
US Classes:327/554, Switched capacitor filter327/337, Having switched capacitance327/552, Active filter330/9, WITH PERIODIC SWITCHING INPUT-OUTPUT (E.G., FOR DRIFT CORRECTION)333/173, Synchronous filters341/143Differential encoder and/or decoder (e.g., delta modulation, differential pulse code modulation)
ExaminersPrimary: Callahan, Timothy P.
Assistant: Le, Dinh T.
Attorney, Agent or Firm
International ClassesH03K 005/00
AbstractThe present invention discloses a biquadratic switched-capacitor filter, which merely utilizes one operational amplifier to implement a biquadratic transfer function. The biquadratic switched-capacitor filter further comprises ten switched-capacitor circuits, two feedback capacitors, and two individual switching devices. The switching devices in this switched-capacitor filter can be controlled by six different clock signals. The first and second clock signals are two-phase, complementary but non-overlapping pulse trains with a reference period. The third clock signal is a pulse train with double the reference period and coincident with the first clock signal. The fourth, the fifth, and the sixth clock signals are pulse trains that result from delaying the third, the fourth, and the fifth clock signals by half the reference period. The obtained switched-capacitor filter can be used to simplify some applications, such as sigma-delta modulators.
Field of SearchActive filter
Switched capacitor filter
With operational amplifier
Sample and hold
Having switched capacitance
WITH PERIODIC SWITCHING INPUT-OUTPUT (E.G., FOR DRIFT CORRECTION)
Differential encoder and/or decoder (e.g., delta modulation, differential pulse code modulation)
Using charge transfer devices (e.g., charge coupled devices, charge transfer by switched capacitances)