US 7,429,889 B2 · Control system for programmable filters

Abstract

Control system for programmable filters, master-slave calibration system and fully programmable high precision filter for use in such control system, such filters being provided with a filter input and a filter output including a first, first order low pass filter section comprising first and second mutually identical operational transconductance amplifiers (OTAs), having a controllable transconductance Gm from a differential voltage input having first and second differential voltage input terminals to a single current output carrying a single phase current output signals, said first and second OTAs being provided with first and second control inputs, respectively, said filter input being coupled to the first differential voltage input terminal of said first OTA. The current outputs of both first and second OTAs are being resistorless coupled to a first capacitor, the current output of the second OTA is negatively fed back to its first differential voltage input terminal to form a variable positive virtual resistance across said first capacitor, the common connection of the single current outputs of the first and second OTAs and the first capacitor constituting an output terminal of the first, first order low pass filter section, which is coupled to said filter output, the second differential voltage input terminals of the first and second OTAs being respectively coupled to first and second DC reference voltage levels, a gain and a bandwidth control signal being respectively supplied to the first and second control input terminals of said first and second OTA. To obtain an unambiguous and orthogonal control of filter parameters, such as gain, bandwidth, quality factor and/or tuning frequency, said gain control signal is provided through a first multiplier to said first control input terminal of the first, first order low pass filter section for multiplying the gain control signal with said bandwidth control signal and said bandwidth control signal at least to said second control input terminal of the first, first order low pass filter section.

Claims20

Dependent claims

A control system for a fully programmable high precision filter having a filter input and a filter output including a first first-order low pass filter section comprising first and second mutually identical operational transconductance amplifiers (OTAs), each having a differential voltage input with first and second differential voltage input terminals and a single current output carrying a single phase current output signal, the first and second OTAs each having a controllable transconductance Gm from the differential voltage input to the single current output and being provided with first and second control inputs, respectively, the filter input being coupled to the first differential voltage input terminal of the first OTA, the current outputs of both first and second OTAs being resistorless coupled to a first capacitor, the current output of the second OTA being negatively fed back to its first differential voltage input terminal to form a variable positive virtual resistance across the first capacitor, the common connection of the single current outputs of the first and second OTAs and the first capacitor constituting an output terminal of the first first-order low pass filter section, which is coupled to the filter output, the second differential voltage input terminals of the first and second OTAs being respectively coupled to first and second DC reference voltage levels, comprising:

a control signal device that is configured to receive an input gain control signal and a bandwidth control signal and includes a first multiplier that is configured to multiply the input gain control signal with the bandwidth control signal to provide an output gain control signal, and
wherein:
the output gain control signal is coupled to the first control input, and
the bandwidth control signal is coupled to the second control input.

1 more element

A system comprising

a master-slave calibration system that includes:
a master filter device, and
a slave filter device,
wherein:
the master filter device is configured to provide a frequency calibration signal to the slave filter device,
the slave filter device and the master filter device respectively include N and M fully programmable high precision filters that include a control system that provides orthogonal control of gain and frequency characteristics via corresponding gain control and frequency control terminals,
the M fully programmable high precision filters of the master filter device are arranged in a regenerative feedback loop to constitute a master oscillator generating a master oscillator signal, the master oscillator signal being frequency locked to a reference frequency through a phase or frequency locked loop (PLL/FLL) carrying a PLL/FLL signal being fed back to the frequency control terminal of the master filter device and providing the frequency calibration signal,
an automatic gain control (AGC) loop is configured to provide an AGC signal derived from an output amplitude of the master filter device to the gain control terminal of the master filter device, thereby providing a gain calibration signal,
the PLL/FLL signal and the AGC signal are configured to calibrate a phase shift and gain within the regenerative feedback loop to meet oscillation conditions at the reference frequency, and
at least one of the frequency calibration signal and the gain calibration signal is coupled to corresponding frequency and gain control terminals of the N fully programmable high precision filters of the slave filter device for at least one of a bandwidth, tuning, and gain calibration thereof.

7 more elements

A filter that is configured to receive an input signal and provide a filtered output signal, comprising:

a first first-order filter section that includes:
a first operational transconductance amplifier (OTA),
a second OTA, and
a multiplier,
wherein:
each of the first and second OTAs have an associated transconductance that is controlled by a transconductance control input, and
the first OTA includes a signal input that is configured to receive the input signal, and an output that is configured to provide the filtered output signal, based on the transconductance of the first OTA,
the second OTA having a second transconductance control input and a second output that is directly coupled to the first output and to a first capacitor, and
a multiplier that is configured to multiply an input gain control signal and a bandwidth control signal to provide the first transconductance control input,
the bandwidth control signal being coupled to the second transconductance input.

7 more elements

Dependencies are inferred from the claim text.

Control system for programmable filters

Life of this patent

Control system for programmable filters

Life of this patent

Abstract

Claims20