# System and method for constructing filters for detecting signals whose frequency content varies with time

## Abstract

A system and method are disclosed for constructing a bank of filters which detect the presence of signals whose frequency content varies with time. The present invention includes a novel system and method for developing one or more time templates designed to match the received signals of interest and the bank of matched filters use the one or more time templates to detect the received signals. Each matched filter compares the received signal x(t) with a respective, unique time template that has been designed to approximate a form of the signals of interest. The robust time domain template is assumed to be of the order of w(t)=A(t)cos(2{pi}{phi}(t)) and the present invention uses the trajectory of a joint time-frequency representation of x(t) as an approximation of the instantaneous frequency function {phi}{prime}(t). First, numerous data samples of the received signal x(t) are collected. A joint time frequency representation is then applied to represent the signal, preferably using the time frequency distribution series. The joint time-frequency transformation represents the analyzed signal energy at time t and frequency f, P(t,f), which is a three-dimensional plot of time vs. frequency vs. signal energy. Then P(t,f) is reduced to a multivalued function f(t), a two dimensionalmore »

- Inventors:

- Issue Date:

- Research Org.:
- Univ. of California (United States)

- OSTI Identifier:
- 403670

- Patent Number(s):
- 5574639

- Application Number:
- PAN: 8-322,053

- Assignee:
- National Instruments Corp., Austin, TX (United States)

- DOE Contract Number:
- W-7405-ENG-36

- Resource Type:
- Patent

- Resource Relation:
- Other Information: PBD: 12 Nov 1996

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; PULSE ANALYZERS; DESIGN; FREQUENCY MEASUREMENT; VARIATIONS; SIGNAL CONDITIONERS; TIME DEPENDENCE

### Citation Formats

```
Qian, S, and Dunham, M E.
```*System and method for constructing filters for detecting signals whose frequency content varies with time*. United States: N. p., 1996.
Web.

```
Qian, S, & Dunham, M E.
```*System and method for constructing filters for detecting signals whose frequency content varies with time*. United States.

```
Qian, S, and Dunham, M E. Tue .
"System and method for constructing filters for detecting signals whose frequency content varies with time". United States.
```

```
@article{osti_403670,
```

title = {System and method for constructing filters for detecting signals whose frequency content varies with time},

author = {Qian, S and Dunham, M E},

abstractNote = {A system and method are disclosed for constructing a bank of filters which detect the presence of signals whose frequency content varies with time. The present invention includes a novel system and method for developing one or more time templates designed to match the received signals of interest and the bank of matched filters use the one or more time templates to detect the received signals. Each matched filter compares the received signal x(t) with a respective, unique time template that has been designed to approximate a form of the signals of interest. The robust time domain template is assumed to be of the order of w(t)=A(t)cos(2{pi}{phi}(t)) and the present invention uses the trajectory of a joint time-frequency representation of x(t) as an approximation of the instantaneous frequency function {phi}{prime}(t). First, numerous data samples of the received signal x(t) are collected. A joint time frequency representation is then applied to represent the signal, preferably using the time frequency distribution series. The joint time-frequency transformation represents the analyzed signal energy at time t and frequency f, P(t,f), which is a three-dimensional plot of time vs. frequency vs. signal energy. Then P(t,f) is reduced to a multivalued function f(t), a two dimensional plot of time vs. frequency, using a thresholding process. Curve fitting steps are then performed on the time/frequency plot, preferably using Levenberg-Marquardt curve fitting techniques, to derive a general instantaneous frequency function {phi}{prime}(t) which best fits the multivalued function f(t). Integrating {phi}{prime}(t) along t yields {phi}{prime}(t), which is then inserted into the form of the time template equation. A suitable amplitude A(t) is also preferably determined. Once the time template has been determined, one or more filters are developed which each use a version or form of the time template. 7 figs.},

doi = {},

journal = {},

number = ,

volume = ,

place = {United States},

year = {1996},

month = {11}

}