CALIBRATION OF LINEAR TIME-INVARIANT SYSTEM'S STEP RESPONSE

• US 20110043267A1
• Filed: 04/30/2009
• Published: 02/24/2011
• Est. Priority Date: 05/06/2008
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: De Jong, Gerben Willem, Jeurissen, Dennis, Van Sinderen, Jan
• Granted Patent: US 8,686,779 B2
• Time in Patent Office: Days
• US Class Current: 327/306
• CPC Class Codes: G01R 31/2837 Characterising or performance testing, e.g. of frequency response transient response G01R27/28

Abstract

The invention concerns in general measurement of the transfer function of linear time invariant systems, more particular the calibration of such systems based on a measured transfer function. According to a first aspect the present invention an arrangement for measuring the transfer function of a linear time-invariant system is disclosed. According to a second aspect of the present invention the arrangement is implemented into a linear time-invariant circuitry having a transfer function representing the amplitude and phase characteristic of the circuitry, where by means of the arrangement for measuring the transfer function the transfer function can be optimized in accordance with certain criteria on-the-fly, i.e. in or before operation of the circuit. Finally, an effective and simple method for measuring of the transfer function of a linear time-invariant system together with the use or application of the method is shown.

Claims

1. An arrangement for measuring a transfer function of a linear time-invariant system, the arrangement comprising:

a test signal generator connected to an input of the system and configured to input a test signal for exciting of the system,

a buffer for storing an instantaneous sample of a response signal at an output of the system,

a trigger unit for triggering the buffer to store and to provide at an output of the buffer, in response to the test signal, at least one respective instantaneous value of the response signal,

wherein the arrangement is further configured to generate a sequence of samples of discrete values of the response signal by iterative exciting the system with the test signal, with an iterative adjusted predetermined delayed action of the trigger unit, until enough samples have been taken, from which the transfer function can be derived.

2. Arrangement according to claim 1, wherein the system comprises an amplifier circuit, which amplifier circuit comprises a group with at least one amplification stage and further comprises at least one feed back path from an output of one amplification stage of the group back to at least an input of one amplification stage of the group.

3. Arrangement according to claim 1,

wherein the trigger unit comprises a delay unit connected to the test signal generator and configured to receive and to delay the test signal by an adjustable delay, and further to supply the delayed test signal to the buffer,

wherein the buffer is further configured such that the delayed test signal triggers the buffer to store the respective instantaneous value of the response signal and further to provide the sample at an output of the buffer.

4. Arrangement according to claim 3, wherein the delay unit is a delay circuit comprising a plurality of different delay elements configured to be selected by a selection unit so that the delay elements can be selectively applied on the test signal.

5. Arrangement according to claim 1, wherein the buffer comprises a buffer circuit comprising a track and hold circuit connected to the output of the linear time-invariant system, the track and hold circuit being configured such that the hold function is controlled by the delayed test signal that the instantaneous value of the response signal is hold and provided at the output of the track and hold circuit.

6. Arrangement according to claim 1, wherein the test signal comprises a step function and the test signal generator comprises a Square Wave Generator.

7. Linear time-invariant circuitry having a transfer function representing an amplitude and a phase characteristic of the circuitry, the circuitry comprising:

at least one feed back path between an output and an input of the circuitry,

a selectively adjustable feed back circuit within the feed back path, and

a circuit arrangement according to claim 1,

wherein the circuit arrangement is configured to measure the transfer function of the circuitry and to modify the transfer function by adjusting the feedback circuit based on the measured transfer function with respect to a stability criteria.

8. Circuitry according to claim 7, wherein the feed back circuit is a pole-splitting circuit comprising switchable circuit elements including at least one of a condensator, an inductor, and a resistor.

9. Circuitry according to claim 7, wherein the stability criteria is a phase margin at a frequency where a loop-gain becomes 1 or 0 dB.

10. Circuit according to claim 7, wherein the circuitry is an amplifier circuit in a feedback configuration, which amplifier circuit comprises a group with at least one amplification stage and further comprises at least one feed back path from an output of one amplification stage of the group back to at least an input of one amplification stage of the group.

11. Method for measuring a transfer function of a linear time-invariant system, the method comprising:

a) exciting the system by a test signal at an input thereof;

b) measuring after a predetermined delay time an instantaneous value of a response signal at an output of the system;

c) increasing the predetermined delay time by a predetermined duration;

d) repeating the steps a) to c) until enough samples from the response signal have been taken, from which the transfer function can be derived.

12. Method according to claim 11, wherein the measuring step comprises tracking the response signal of the system until the predetermined delay time is lapsed and then holding the instantaneous value of the response signal.

13. Method according to claim 11, further comprising converting the measured instantaneous values of the response signal into digital data and storing the digital data.

14. Method according to claim 11, wherein the measuring step further comprises measuring multiple samples of the response signal with a same delay time and generating one representative sample for each delay time by predetermined processing, optionally, averaging.

15. A method according to claim 11, wherein the method is for evaluating a linear time-invariant system with respect to a stability criterion, and wherein the time-invariant system is an electronic circuit and the transfer function thereof is modified based on the evaluated stability criteria.