Resolution filter for a spectrum analyzer

Details Resolution filter for a spectrum analyzer Resolution filter for a spectrum analyzer

2002-02-05

2004-07-13

Decady, Albert (Department: 2133)

Data processing: measuring, calibrating, or testing

Measurement system

Measured signal processing

C324S076270, C708S300000

Reexamination Certificate

active

06763323

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a resolution filter for a spectrum analyzer.
BACKGROUND OF THE INVENTION
During a spectrum analysis, a predetermined frequency range is swept with a resolution filter that has a predetermined band width, which is why the resolution filter is also referred to as a sweep filter. One resolution filter for a spectrum analyzer with an analog construction is described for instance in U.S. Pat. No. 5,736,845. With resolution filters which have a conventional analog construction, it is possible to achieve only a limited sweeping speed, referred to as the K-factor, which determines and limits how fast the sweeping is conducted in conventional resolution filters.
It has been generally assumed up until now that sweeping can be conducted within T
res
with an order of magnitude of 1/B
res
=T
res
so that the resolution filter would be still able to respond. This statement has been taught as a fact, similar to the time law in information technology. In any case, this statement is correct only if it is based on the principle of a fixed filter for all sweeping speeds.
Therefore, there is a need for a resolution filter that makes it possible to achieve an optimal resolution with a high sweeping speed.
SUMMARY OF THE INVENTION
These and other needs are addressed by a resolution filter that has either a complex pulse response h
used
(t)=C
1
·e
−C
2
·t
2
·e
−j·C
3
·t
2
or a real pulse response h
used
(t)=C
4
·e
−C
5
·t
2
, in which C
1
, C
2
, C
3
, C
4
and C
5
are constants. Accordingly, sweeping can be conducted even with an infinite speed with an optimal complex resolution filter, without causing by this occurrences of amplitude and band width errors.
It has been further also shown that, although sweeping cannot be conducted with an unlimited speed in case of a real resolution filter, it is still possible to achieve a minimum K-factor of K
min
=0.88. Definition of the K factor: sweeping is conducted within T
res
with 1/K·B
res
.
Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive.


REFERENCES:
patent: 5075619 (1991-12-01), Said
patent: 5706202 (1998-01-01), Itahara et al.
patent: 5926793 (1999-07-01), de Rafael et al.
patent: 6275020 (2001-08-01), Nagano
patent: 196 27 784 (1997-06-01), None
patent: 196 27 788 (1998-01-01), None
Mallat, A wavelet Tour of Signal Processing, 1998, 1999, Academic Press, Second Edition, pp. 2,3,71 and 87.

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