Method of and means for measuring the level of test signals over selected wide band frequency ranges

Claim 1

A method of determining the level of received test signals over selected frequency ranges of different bandwidths B bounded by a lower limiting frequency f' and an upper limiting frequency f", comprising the steps of: establishing a frequency window of fixed width b≦B within a selected frequency range; shifting said window in the presence of said test signals across the selected range with the midfrequency f m of said window varying in a sweep cycle between f'+b/2 and f"-b/2; integrating the RMS values of signal amplitudes appearing in said window throughout the sweep cycle; shifting at least one of said limiting frequencies for changing to a different frequency range; and measuring the integrated RMS values of each frequency range after multiplying said values with a corrective factor proportional to the bandwidth B of the respective frequency range.

Claim 2

A method of determining the level of received test signals over selected frequency ranges of different bandwidths B bounded by a lower limiting frequency f' and an upper limiting frequency f", comprising the steps of: establishing a frequency window of fixed width b≦B within a selected frequency range; shifting said window in the presence of said test signals across the selected range with the midfrequency f m of said window varying in a sweep cycle between f'+b/2 and f"-b/2; integrating the RMS values of signal amplitudes appearing in said window throughout the sweep cycle; shifting at least one of said limiting frequencies for changing to a different frequency range; and measuring the integrated RMS values of each frequency range after multiplying said values with a corrective factor proportional to the bandwidth B of the respective frequency range.

Claim 8

A system for determining the level of received test signals over selected frequency ranges of different bandwidths B, comprising: input means for receiving test signals lying within a selected frequency range; filter means having a pass band of substantially constant width b≦B outside the selectable frequency ranges, said pass band having a fixed center frequency f c ; a generator of variable modulating frequency, ranging in a recurrent sweep between a minimum value f'-f c +b/2 and a maximum value f"-f c -b/2 wherein f' is a lower limiting frequency and f" is an upper limiting frequency of the selected range; mixer means connected to said input means upstream of said filter means and further connected to said generator for heterodyning said test signals with said modulating frequency to generate beat-frequency oscillations passed by said filter means, said beat-frequency oscillations corresponding to test signals present in a frequency window of width b centered on a midfrequency f m ; scanning means for periodically varying said modulating frequency between said minimum and maximum values, thereby shifting said midfrequency f m between limits f'+b/2 and f"-b/2, said scanning means including a range selector operable to vary at least one of said limiting frequencies; output means including rectification, storage and weighting circuitry connected to said filter means for integrating the RMS values of signal voltages appearing within said frequency window throughout at least one sweep cycle and multiplying said signal voltages by a corrective factor proportional to said bandwidth B; and indicator means connected to said circuitry for giving a reading of the integrated signal voltages so multiplied, said range selector being coupled with said output means for automatically modifying said corrective factor in conformity with the bandwidth B of the selected range.

Claim 9

A system for determining the level of received test signals over selected frequency ranges of different bandwidths B, comprising: input means for receiving test signals lying within a selected frequency range; filter means having a pass band of substantially constant width b≦B outside the selectable frequency ranges, said pass band having a fixed center frequency f c ; a generator of variable modulating frequency, ranging in a recurrent sweep between a minimum value f'-f c +b/2 and a maximum value f"-f c -b/2 wherein f' is a lower limiting frequency and f" is an upper limiting frequency of the selected range; mixer means connected to said input means upstream of said filter means and further connected to said generator for heterodyning said test signals with said modulating frequency to generate beat-frequency oscillations passed by said filter means, said beat-frequency oscillations corresponding to test signals present in a frequency window of width b centered on a midfrequency f m ; scanning means for periodically varying said modulating frequency between said minimum and maximum values, thereby shifting said midfrequency f m between limits f'+b/2 and f"-b/2, said scanning means including a range selector operable to vary at least one of said limiting frequencies; output means including rectification, storage and weighting circuitry connected to said filter means for integrating the RMS values of signal voltages appearing within said frequency window throughout at least one sweep cycle and multiplying said signal voltages by a corrective factor proportional to said bandwidth B; and indicator means connected to said circuitry for giving a reading of the integrated signal voltages so multiplied, said range selector being coupled with said output means for automatically modifying said corrective factor in conformity with the bandwidth B of the selected range.