Frequency selective level meter with an automatic distortion eliminator

Claim 3

The method according to claim 1 wherein the step of simultaneously adjusting the input attenuation level and the amplification gain between two distinct levels includes simultaneously switching a fixed attenuating pad into the level meter signal path prior to the non-linear active electronic device and a fixed gain amplifier into the level meter signal path after the non-linear active electronic device, the fixed attenuation and the fixed gain having equal decibel levels.

Claim 4

The method according to claim 1 wherein said two distinct levels differ by substantially 2 decibels.

Claim 5

The method according to claim 1 wherein the defined signal range of the measuring circuits is significantly less than the range of the input attenuation, and further wherein a difference between said two distinct levels is a small fraction of the defined signal range of the measuring circuits.

Claim 6

The method according to claim 1 which includes an initial step of adjusting said input attenuation level without adjusting the amplification in order to first bring the input signal level within said defined range of said measuring circuits.

Claim 7

The method according to claim 1 wherein the step of automatically increasing the input attenuation and the output amplification includes making such increases one step at a time only after the signal level differs from the reference signal amount for a plurality of cycles in succession of the simultaneous cycling of the attenuation level and the amplification between said two distinct levels, whereby simultaneous automatic increases of the input attenuation and the output amplification are less likely to occur from instantaneous noise at the signal input.

Claim 8

The method according to claim 1 wherein the method additionally comprises the initial steps of maintaining the output amplification of the level meter at its lowest level, initially setting the input attenuation at its lowest level and then increasing the attenuation level of the input attenuator without adjusting the amplification of the level meter in order to first bring the input signal level within said defined range of said measuring circuits.

Claim 9

The method according to claim 7 wherein the step of increasing the attenuation level of the input attenuator includes adding discrete steps of attenuation, the method additionally comprising the steps of monitoring whether an increase of the input attenuation from one step to a next successive step drives the input signal level at the measuring circuits from outside its said defined range on one side and through the defined range and outside thereof on its other side, and increasing the level of output attenuation and the level of input attenuation of the level meter equally in a manner to keep the overall gain constant in order to reduce the distortion which causes the signal level at the measuring circuits to pass completely through its said defined range when the input attenuator is increased alone from one step to another.

Claim 10

A level meter, comprising: an adjustable attenuator for receiving at an input a signal to be measured, a non-linear electronic element receiving a signal from the adjustable attenuator, an adjustable gain element connected to amplify an output of the non-linear element, a signal measuring and display circuit having a defined input signal level range receiving the output of said adjustable gain element, means for alternating between two fixed levels the gain or attenuation in the path of the signal simultaneously at both the input and output sides of said non-linear element in a manner to keep the overall gain of the circuit constant, and means responsive to the signal applied to said measuring and display circuits for automatically adjusting simultaneously the input adjustable attenuator and the amplification of said adjustable gain element to minimize any differences that may exist in the signal level to the measuring and display circuit when the gain or attenuation in the path of the signal at both sides of the frequency selecting means is simultaneously alternated between said two fixed levels.

Claim 11

A level meter, comprising: an adjustable attenuator for receiving at an input a signal to be measured, a non-linear electronic element receiving a signal from the adjustable attenuator, an adjustable gain element connected to amplify an output of the non-linear element, a signal measuring and display circuit having a defined input signal level range receiving the output of said adjustable gain element, means for alternating between two fixed levels the gain or attenuation in the path of the signal simultaneously at both the input and output sides of said non-linear element in a manner to keep the overall gain of the circuit constant, and means responsive to the signal applied to said measuring and display circuits for automatically adjusting simultaneously the input adjustable attenuator and the amplification of said adjustable gain element to minimize any differences that may exist in the signal level to the measuring and display circuit when the gain or attenuation in the path of the signal at both sides of the frequency selecting means is simultaneously alternated between said two fixed levels.

Claim 12

A level meter according to claim 9 wherein the automatic adjusting means includes a means for comparing to a threshold value any difference in the signal to the measuring and display circuit as said fixed gain or attenuation is switched between its said two fixed levels and causing adjustment of the input attenuation and adjustable gain element only if said difference exceeds said threshold.

Claim 13

A level meter according to claim 10 wherein said automatic adjusting means additionally includes means for examining whether said signal level difference at the input to the measuring and display circuit exceeds a threshold level for a plurality of cycles of alternating between said two fixed levels of gain or attenuation before an adjustment of the input attenuator and the amplifier is permitted to take place, whereby adjustment thereof in response to random instantaneous noise is prevented.

Claim 14

A signal level meter according to claim 9 wherein a difference between said two fixed levels of gain or attenuation in the path of the signal at both the input and output sides of said non-linear element is significantly less in magnitude than the range of said measuring and display circuit.

Claim 15

A signal level meter according to claim 12 wherein said difference between said two fixed levels is substantially two decibels and the range of said measuring and display circuit is substantially 10 decibels.

Claim 16

A signal level meter according to claim 13 wherein the adjustable input attenuator and the amplifier are each adjustable by steps of substantially 10 decibels.

Claim 17

A signal level meter, comprising: an adjustable attenuator for receiving at an input a signal to be measured, a non-linear electronic element receiving a signal from the adjustable attenuator, an adjustable gain element connected to amplify an output of the non-linear element, a signal measuring and display circuit having an input signal level range that is significantly less than the range of adjustment of said input attenuator, said measuring and display circuits receiving the output of said amplifier, means for alternating between two fixed levels the gain or attenuation in the path of the signal simultaneously at both the input and output sides of said non-linear element in a manner to keep the overall gain of the circuit constant, and means responsive to the signal applied to said measuring and display circuits for automatically adjusting simultaneously the input adjustable attenuator and the amplification of said adjustable gain element to minimize any differences that may exist in the signal level to the measuring and display circuit when the gain or attenuation in the path of the signal at both sides of the frequency selecting means is simultaneously alternated between said two fixed levels, said automatic adjusting means comprising means for examining whether said signal level difference at the input to the measuring and display circuit exceeds a threshold level for a plurality of successive cycles of alternating between said two fixed levels of gain or attenuation before an adjustment of the input attenuator and the amplifier is permitted to take place, said examining means including a digital counter that is advanced in count a predetermined amount in response to the difference in signal level at the input to the measuring and testing circuit exceeding said threshold level during one cycle of changing between said two fixed levels of gain or attenuation, said counter being reset when said signal level difference is less than said threshold level during one cycle of changing between said two fixed levels, and further wherein said counter emits an overflow signal upon exceeding its maximum count which simultaneously effects a change in the setting of the adjustable input attenuator and the intermediate frequency amplifier.

Claim 18

A signal level meter, comprising: an adjustable attenuator for receiving at an input a signal to be measured, a non-linear electronic element receiving a signal from the adjustable attenuator, an adjustable gain element connected to amplify an output of the non-linear element, a signal measuring and display circuit having an input signal level range that is significantly less than the range of adjustment of said input attenuator, said measuring and display circuits receiving the output of said amplifier, means for alternating between two fixed levels the gain or attenuation in the path of the signal simultaneously at both the input and output sides of said non-linear element in a manner to keep the overall gain of the circuit constant, and means responsive to the signal applied to said measuring and display circuits for automatically adjusting simultaneously the input adjustable attenuator and the amplification of said adjustable gain element to minimize any differences that may exist in the signal level to the measuring and display circuit when the gain or attenuation in the path of the signal at both sides of the frequency selecting means is simultaneously alternated between said two fixed levels, said automatic adjusting means comprising means for examining whether said signal level difference at the input to the measuring and display circuit exceeds a threshold level for a plurality of successive cycles of alternating between said two fixed levels of gain or attenuation before an adjustment of the input attenuator and the amplifier is permitted to take place, said examining means including a digital counter that is advanced in count a predetermined amount in response to the difference in signal level at the input to the measuring and testing circuit exceeding said threshold level during one cycle of changing between said two fixed levels of gain or attenuation, said counter being reset when said signal level difference is less than said threshold level during one cycle of changing between said two fixed levels, and further wherein said counter emits an overflow signal upon exceeding its maximum count which simultaneously effects a change in the setting of the adjustable input attenuator and the intermediate frequency amplifier.

Claim 19

A frequency selective level meter, comprising: an input attenuator that is adjustable between a plurality of attenuation levels, a frequency translator including a mixer and an adjustable oscillator for translating a signal at an output of the attenuator to a fixed frequency bandwidth, a high gain amplifier Having a plurality of adjustable gain values for receiving a fixed frequency signal output of the frequency translator and applying it to a measuring and display circuit of a fixed input signal range, a digital decoding circuit responsive to a first digital input for changing the attenuation level of said input attenuator and further responsive to a second digital input for simultaneously increasing the attenuation of said input attenuator and increasing the gain of said high gain amplifier by equal amounts, means for applying a first digital signal to said decoding circuit in response to the detection of a signal level input to the measuring and display circuit falling outside the range of said measuring and display circuit, a first means between said input attenuator and said frequency translator for switching between two attenuation or gain levels separated a preset amount, a second means at the output of said frequency translator for switching between said two gain or attenuation levels separated by said preset amount, means for simultaneously cycling said first and second switching means between said two levels in a manner that the overall gain of the signal level circuits remains constant, said switching means being enabled only after the signal to said measuring and display circuits has been adjusted to be within its said input signal range by operation of said first digital signal applying means, means responsive to the signal applied to the measuring and display circuits for determining when said signal varies in level by more than a predetermined threshold amount as said first and second switching means are cycled between their two gain or attenuation levels, and means responsive to said detecting means for generating a signal that is applied to said decoding means as its second digital input when the difference signal to the measuring and detecting circuits is greater than said threshold for a plurality of consecutive cycles of said first and second switching means.

Claim 20

A frequency selective level meter, comprising: an input attenuator that is adjustable between a plurality of attenuation levels, a frequency translator including a mixer and an adjustable oscillator for translating a signal at an output of the attenuator to a fixed frequency bandwidth, a high gain amplifier Having a plurality of adjustable gain values for receiving a fixed frequency signal output of the frequency translator and applying it to a measuring and display circuit of a fixed input signal range, a digital decoding circuit responsive to a first digital input for changing the attenuation level of said input attenuator and further responsive to a second digital input for simultaneously increasing the attenuation of said input attenuator and increasing the gain of said high gain amplifier by equal amounts, means for applying a first digital signal to said decoding circuit in response to the detection of a signal level input to the measuring and display circuit falling outside the range of said measuring and display circuit, a first means between said input attenuator and said frequency translator for switching between two attenuation or gain levels separated a preset amount, a second means at the output of said frequency translator for switching between said two gain or attenuation levels separated by said preset amount, means for simultaneously cycling said first and second switching means between said two levels in a manner that the overall gain of the signal level circuits remains constant, said switching means being enabled only after the signal to said measuring and display circuits has been adjusted to be within its said input signal range by operation of said first digital signal applying means, means responsive to the signal applied to the measuring and display circuits for determining when said signal varies in level by more than a predetermined threshold amount as said first and second switching means are cycled between their two gain or attenuation levels, and means responsive to said detecting means for generating a signal that is applied to said decoding means as its second digital input when the difference signal to the measuring and detecting circuits is greater than said threshold for a plurality of consecutive cycles of said first and second switching means.

Claim 21

A frequency selective level meter according to claim 16 which additionally comprises a transition detector for generating a signal that is applied to said decoding circuit as its second digital input when in response to its first digital input said decoding circuit causes the signal level to the measuring and display circuits to pass completely through its said input signal range.

Claim 22

A level meter, comprising: an adjustable attenuator for receiving at an input a signal to be measured, a non-linear electronic element receiving a signal from the adjustable attenuator, an adjustable gain element connected to amplify an output of the non-linear element, a signal measuring and display circuit having an input signal level range that is significantly less than the range of adjustment of said input attenuator, said measuring and display circuits receiving the output of said amplifier, means sensing the level of the signal applied to said measuring and display circuit for increasing attenuation of the adjustable attenuator to bring the signal level within said input range while adjustable gain element remains fixed, means operable after the signal level to the measuring and display circuits falls within its said input range for alternating between two fixed levels the gain or attenuation in the path of the signal simultaneously at both the input and output sides of said non-linear element in a manner to keep the overall gain of the circuit constant, and means responsive to the signal applied to said measuring and display circuits for automatically adjusting simultaneously the input adjustable attenuator and the amplification of said adjustable gain element to minimize any differences that may exist in the signal level to the measuring and display circuit when the gain or attenuation in the path of the signal at both sides of the frequency selecting means is simultaneously alternated between said two fixed levels.

Claim 23

A level meter, comprising: an adjustable attenuator for receiving at an input a signal to be measured, a non-linear electronic element receiving a signal from the adjustable attenuator, an adjustable gain element connected to amplify an output of the non-linear element, a signal measuring and display circuit having an input signal level range that is significantly less than the range of adjustment of said input attenuator, said measuring and display circuits receiving the output of said amplifier, means sensing the level of the signal applied to said measuring and display circuit for increasing attenuation of the adjustable attenuator to bring the signal level within said input range while adjustable gain element remains fixed, means operable after the signal level to the measuring and display circuits falls within its said input range for alternating between two fixed levels the gain or attenuation in the path of the signal simultaneously at both the input and output sides of said non-linear element in a manner to keep the overall gain of the circuit constant, and means responsive to the signal applied to said measuring and display circuits for automatically adjusting simultaneously the input adjustable attenuator and the amplification of said adjustable gain element to minimize any differences that may exist in the signal level to the measuring and display circuit when the gain or attenuation in the path of the signal at both sides of the frequency selecting means is simultaneously alternated between said two fixed levels.

Claim 24

A level metEr according to claim 18 which additionally comprises means for detecting when the input signal level to the measuring and display circuits passes completely through its input signal level range upon addition of one step of attenuation of the adjustable attenuator, and means enabled by said detecting means for simultaneously increasing the attenuation level of the adjustable attenuator and the amplification of the adjustable gain element by equal increments until the addition of one step of attenuation of the adjustable attenuator by the sensing means no longer causes the signal level to the measuring and display circuits to pass through its said input range.