Apparatus and systems for testing and monitoring receiver equipment, including system capability for continuous in-service performance monitoring

Claim 2

Automatic noise-figure indication test apparatus for testing receiver equipment comprising a logarithmic voltage-controlled attenuator having input and output connections and also having a control connection for providing an attenuation between said input and output connections which is a logarithmic function of the D.C. component of voltage applied to said control connection, means for connecting said input connection of the attenuator to the receiver to be tested, a fast-acting automatic gain control feedback loop which is connected from said output connection of the attenuator to said control connection of the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of noise voltage, and read out means in said apparatus connected to said control connection and responsive to the level of the alternating voltage in said control connection for providing information as to the receiver noise figure.

Claim 7

A monitoring system for monitoring receivers while the receivers are on-line in actual service utilizing test noise wherein the test noise is introduced at an energy level substantially below the receiver noise energy level so as not to interfere with the normal operation of the receiver comprising a noise source, a high frequency modulator for modulating the noise source at a high frequency F2, a low frequency modulator for gating the modulated noise source on-and-off at a low frequency F1, where F2 is preferably at least 10 times F1, means for connecting said modulated noise source to the receiver input, said monitoring system including means for providing square-law detection, said square law detection means being includable in the receiver or in the test system, a narrow band filter connected in circuit after said square-law detection means and in circuit with the receiver, said narrow band filter having a bandwidth more than twice F1, a logarithmic voltage-controlled attenuator having input and output connections and also having a control connection for providing an attenuation between said input and output connections which is a logarithmic function of the D.C. component of voltage applied to said control connection, said attenuator having its input connected in circuit with said narrow band filter, a fast-acting automatic gain control feedback loop which is connected from said output connection of the attenuator to said control connection of the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of noise voltage, and read out means in said apparatus connected to said control connection and responsive to the level of the alternating voltage in said control connection for providing information as to the receiver noise figure.

Claim 8

A monitoring system for monitoring receivers while the receivers are on-line in actual service utilizing test noise wherein the test noise is introduced at an energy level substantially below the receiver noise energy level so as not to interfere with the normal operation of the receiver comprising a noise source, a high frequency modulator for modulating the noise source at a high frequency F2, a low frequency modulator for gating the modulated noise source on-and-off at a low frequency F1, where F2 is preferably at least 10 times F1, means for connecting said modulated noise source to the receiver input, said monitoring system including means for providing square-law detection, said square law detection means being includable in the receiver or in the test system, a narrow band filter connected in circuit after said square-law detection means and in circuit with the receiver, said narrow band filter having a bandwidth more than twice F1, a logarithmic voltage-controlled attenuator having input and output connections and also having a control connection for providing an attenuation between said input and output connections which is a logarithmic function of the D.C. component of voltage applied to said control connection, said attenuator having its input connected in circuit with said narrow band filter, a fast-acting automatic gain control feedback loop which is connected from said output connection of the attenuator to said control connection of the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of noise voltage, and read out means in said apparatus connected to said control connection and responsive to the level of the alternating voltage in said control connection for providing information as to the receiver noise figure.

Claim 9

A monitoring system for monitoring receivers while the receivers are on-line in actual service utilizing test noise wherein the test noise is introduced at an energy level substantially below the receiver noise energy level so as not to interfere with the normal operation of the receiver and said monitoring systeM being capable of accurately performing its monitoring function in the presence of strong signals being received having a predetermined frequency spectral characteristic comprising a noise source, a high frequency modulator for modulating the noise source at a high frequency F2, a low frequency modulator for gating the modulated noise source on-and-off at a low frequency F1, where F2 is preferably at least ten times F1, means for connecting said modulated noise source to the receiver input, said monitoring system including means for providing square-law detection, said square law detection means being includable in the receiver or in the test system, a broad band filter connected to the receiver and tuned to a range of frequencies displaced from the frequency sectral characteristics of the strong signals being received, said broad band filter having a bandwidth more than twice F2, a narrow band filter connected in circuit after said square law detection means and also after said broad band filter, said narrow band filter having a bandwidth more than twice F1, a logarithmic voltage-controlled attenuator having input and output connections and also having a control connection for providing an attenuation between said input and output connections which is a logarithmic function of the D.C. component of voltage applied to said control connection, said attenuator having its input connected in circuit with said narrow band filter, a fast-acting automatic gain control feedback loop which is connected from said output connection to said control connection of the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of noise voltage, and read out means in said apparatus connected to said control connection and responsive to the level of the alternating voltage in said control connection for providing information as to the receiver noise figure.

Claim 10

A monitoring system for monitoring receivers while the receivers are on-line in actual service utilizing test noise wherein the test noise is introduced at an energy level substantially below the receiver noise energy level so as not to interfere with the normal operation of the receiver and said monitoring systeM being capable of accurately performing its monitoring function in the presence of strong signals being received having a predetermined frequency spectral characteristic comprising a noise source, a high frequency modulator for modulating the noise source at a high frequency F2, a low frequency modulator for gating the modulated noise source on-and-off at a low frequency F1, where F2 is preferably at least ten times F1, means for connecting said modulated noise source to the receiver input, said monitoring system including means for providing square-law detection, said square law detection means being includable in the receiver or in the test system, a broad band filter connected to the receiver and tuned to a range of frequencies displaced from the frequency sectral characteristics of the strong signals being received, said broad band filter having a bandwidth more than twice F2, a narrow band filter connected in circuit after said square law detection means and also after said broad band filter, said narrow band filter having a bandwidth more than twice F1, a logarithmic voltage-controlled attenuator having input and output connections and also having a control connection for providing an attenuation between said input and output connections which is a logarithmic function of the D.C. component of voltage applied to said control connection, said attenuator having its input connected in circuit with said narrow band filter, a fast-acting automatic gain control feedback loop which is connected from said output connection to said control connection of the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of noise voltage, and read out means in said apparatus connected to said control connection and responsive to the level of the alternating voltage in said control connection for providing information as to the receiver noise figure.

Claim 11

Automatic noise-figure indication test apparatus for testing receiver equipment comprising a logarithmic voltage-controlled attenuator having input and output connections and also having a control connection for providing an attenuation between said input and output connections which is a logarithmic function of the D.C. component of voltage applied to said control connection, means for connecting said input connection of the attenuator to the receiver to be tested, a fast-acting automatic gain control feedback loop which is connected from said output connection of the attenuator to said control connection of the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of noise voltage, a slow-acting A.G.C. loop responsive to the output from said attenuator and connected to a point in said test apparatus ahead of said input connection of the attenuator, and read out means in said apparatus connected to said control connection and responsive to the level of the alternating voltage in said control connection for providing information as to the receiver noise figure.

Claim 12

Automatic noise-figure indication test apparatus for testing receiver equipment comprising a logarithmic voltage-controlled attenuator having input and output connections and also having a control connection for providing an attenuation between said input and output connections which is a logarithmic function of the D.C. component of voltage applied to said control connection, means for connecting said input connection of the attenuator to the receiver to be tested, a fast-acting automatic gain control feedback loop which is connected from said output connection of the attenuator to said control connection of the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of noise voltage, a slow-acting A.G.C. loop responsive to the output from said attenuator and connected to a point in said test apparatus ahead of said input connection of the attenuator, and read out means in said apparatus connected to said control connection and responsive to the level of the alternating voltage in said control connection for providing information as to the receiver noise figure.

Claim 13

A parameter monitoring system for continuously monitoring the performance of receiver parameters while the receiver is in service comprising a white noise source, a modulator associated with said noise source for modulating the output of said noise source, coupling means for coupling the output of said modulated noise source into the receiver input, a logarithmic voltage controlled attenuator, means for connecting the attenuator to the receiver to be tested, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of noise, and read out means connected to said feed-back loop and responsive to the level of the alternAting voltage in said feedback loop for providing information as to the receiver performance.

Claim 14

A parameter monitoring system for continuously monitoring the performance of receiver parameters while the receiver is in service comprising a white noise source, a modulator associated with said noise source for modulating the output of said noise source, coupling means for coupling the output of said modulated noise source into the receiver input, a logarithmic voltage controlled attenuator, means for connecting the attenuator to the receiver to be tested, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of noise, and read out means connected to said feed-back loop and responsive to the level of the alternAting voltage in said feedback loop for providing information as to the receiver performance.

Claim 15

A parameter monitoring system as claimed in claim 7, in which the receiver includes a pair of receiver channels each having input connections and output connections, a divider is connected to the output from said modulated noise source, said coupling means includes a pair of couplers in circuit between said divider and the respective input connections of said pair of receiver channels, and switch means is included for periodically feeding energy from the output connections of the respective channels to said attenuator for monitoring the gain tracking of said pair of channels over a wide band of frequencies equal to the full operating band width of the receiver channels.

Claim 16

A parameter monitoring system as claimed in claim 7, in which the receiver includes a plurality of receiver channels each having input connections and output connections, said coupling means includes a plurality of couplers in circuit between said divider and all of the respective input connections, second coupling means is connected to all of the respective output connections of the respective receivers, and said switch means is periodically switched between the output connection for one of said channels chosen as a ''''standard'''' and the output connection from the other channels in turn for comparing the performance of the other channels with said ''''standard'''' channel.

Claim 17

A monitoring system for continuously monitoring the performance of receiver system parameters while the receiver system is in service comprising a white noise source, a high frequency modulator associated with said noise source for modulating the output of said noise source at a high frequency, first circuit means for feeding the energy output from said modulated noise source into the receiver system input, second circuit means for feeding energy from the receiver output, switch means in one of said circuit means for periodically interrupting said one circuit means at a predetermined switching rate, said high frequency being sufficiently high to be operatively spaced from the switching rate of said switching means and preferably at least 10 times said switching rate, a logarithmic voltage controlled attenuator, said second circuit means connecting the attenuator to the receiver to be tested, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of noise, and read out means in said apparatus connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for providing information as to the receiver performance.

Claim 18

A monitoring system for continuously monitoring the performance of receiver system parameters while the receiver system is in service comprising a white noise source, a high frequency modulator associated with said noise source for modulating the output of said noise source at a high frequency, first circuit means for feeding the energy output from said modulated noise source into the receiver system input, second circuit means for feeding energy from the receiver output, switch means in one of said circuit means for periodically interrupting said one circuit means at a predetermined switching rate, said high frequency being sufficiently high to be operatively spaced from the switching rate of said switching means and preferably at least 10 times said switching rate, a logarithmic voltage controlled attenuator, said second circuit means connecting the attenuator to the receiver to be tested, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of noise, and read out means in said apparatus connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for providing information as to the receiver performance.

Claim 21

A system for continuously monitoring the gain tracking performance of a plurality of receiver channels as claimed in claim 11, in which said read out means is preferably narrow band responsive and is tuned to be responsive at the switching rate F1.

Claim 22

A system for continuously monitoring the gain tracking performance of a plurality of receiver channels as claimed in claim 11, in which synchronous detection means is included in said system associated with said read out means and is controlled in accordance with the switching of said switching means.

Claim 23

A performance monitoring system for continuously monitoring the phase tracking of a pluraity of receiver channels while the receiver channels are in normal service without significantly interfering with their normal service comprising a white noise source, a high frequency modulator associated with said white noise sourcefor modulating the output of said white noise source at a high frequency F2, first coupling means of equal effective electrical length for injecting the modulated white noise into the inputs of a plurality of said receiver channels at the same energy level and also at the same phase, a hybrid and second coupling means associated with the outputs of said receiver channels for coupling said hybrid to a predetermined pair of said outputs, a narrow band filter arranged to receive energy from the output of said hybrid, said narrow band filter having its pass-band center frequency at the frequency F2, said monitoring system including means for providing square-law detection located ahead of said narrow band filter, said square-law detection means being located in said monitoring system ahead of said narrow band filter and behind said hybrid, a logarithmic voltage controlled attenuator connected to said narrow band filter, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of the modulated white noise from said noise source, and read out means in said monitoring system connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for providing information as to the phase tracking of said receiver channels.

Claim 24

A performance monitoring system for continuously monitoring the phase tracking of a pluraity of receiver channels while the receiver channels are in normal service without significantly interfering with their normal service comprising a white noise source, a high frequency modulator associated with said white noise sourcefor modulating the output of said white noise source at a high frequency F2, first coupling means of equal effective electrical length for injecting the modulated white noise into the inputs of a plurality of said receiver channels at the same energy level and also at the same phase, a hybrid and second coupling means associated with the outputs of said receiver channels for coupling said hybrid to a predetermined pair of said outputs, a narrow band filter arranged to receive energy from the output of said hybrid, said narrow band filter having its pass-band center frequency at the frequency F2, said monitoring system including means for providing square-law detection located ahead of said narrow band filter, said square-law detection means being located in said monitoring system ahead of said narrow band filter and behind said hybrid, a logarithmic voltage controlled attenuator connected to said narrow band filter, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast acting A.G.C. loop being sufficiently fast to follow the changes in the root means square value of the modulated white noise from said noise source, and read out means in said monitoring system connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for providing information as to the phase tracking of said receiver channels.

Claim 25

A performance monitoring system for continuously monitoring the phase tracking of a plurality of receiver channels as claimed in claim 14, in which said read out means is preferably narrow band responsive and is tuned to be responsive at the switching rate F1.

Claim 26

A performance monitoring system for continuously monitoring the phase tracking of a plurality of receiver channels as claimed in claim 14, in which synchronous detection means is included in said system associated with said read out means and is controlled in accordance with the switching of said switching means.

Claim 27

A monitoring system for continuously monitoring the antenna voltage standing wave ratio (VWSR) of a receiver while the receiver is in normal service without significantly interfering with the normal service of the receiver, comprising a white noise source, a high frequency modulator associated with said noise source for modulating the output of said noiSe source at a high frequency F2, directional coupling means associated with the input line extending from the antenna to the receiver for injecting energy into the input line after the antenna, an attenuator connected to one port of said coupling means, an isolator connected to the other port of said coupling means, switch means between said modulated noise source and said attenuator and isolator and being switchable back and forth between a first and a second condition, said switch means in said first condition feeding modulated white noise through said attenuator and through said directional coupling means into the input line in a direction toward the receiver, said switch means in said second condition feeding modulated white noise through said isolator and through said coupling means into the input line in a direction toward the antenna so as to be reflected by the antenna back toward the receiver, second coupling means associated with the receiver output, a narrow band filter arranged to receive energy from the second coupling means, said monitoring system including means for providing square-law detection located ahead of said narrow band filter and preferably in the receiver, a logarithmic voltage controlled attenuator connected to said narrow band filter, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of the modulated white noise from said noise source, and read out means in said monitoring system connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for continuously providing information as to the antenna VSWR within the bandwidth of the receiver.

Claim 28

A monitoring system for continuously monitoring the antenna voltage standing wave ratio (VWSR) of a receiver while the receiver is in normal service without significantly interfering with the normal service of the receiver, comprising a white noise source, a high frequency modulator associated with said noise source for modulating the output of said noiSe source at a high frequency F2, directional coupling means associated with the input line extending from the antenna to the receiver for injecting energy into the input line after the antenna, an attenuator connected to one port of said coupling means, an isolator connected to the other port of said coupling means, switch means between said modulated noise source and said attenuator and isolator and being switchable back and forth between a first and a second condition, said switch means in said first condition feeding modulated white noise through said attenuator and through said directional coupling means into the input line in a direction toward the receiver, said switch means in said second condition feeding modulated white noise through said isolator and through said coupling means into the input line in a direction toward the antenna so as to be reflected by the antenna back toward the receiver, second coupling means associated with the receiver output, a narrow band filter arranged to receive energy from the second coupling means, said monitoring system including means for providing square-law detection located ahead of said narrow band filter and preferably in the receiver, a logarithmic voltage controlled attenuator connected to said narrow band filter, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of the modulated white noise from said noise source, and read out means in said monitoring system connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for continuously providing information as to the antenna VSWR within the bandwidth of the receiver.

Claim 29

A monitoring system for antenna VSWR as claimed in claim 17, in which said read out means is preferably narrow band responsive and is tuned to be responsive at the switching rate F1.

Claim 30

A monitoring system for antenna VSWR as claimed in claim 17, in which synchronous detection means is included in said system associated with said read out means and is controlled in accordance with the switching of said switch means.

Claim 31

A monitoring system for antenna VSWR as claimed in claim 17, in which said receiver is tunable in frequency and the claimed system enables the antenna VSWR to be measured at different frequencies by tuning the receiver to such frequencies.

Claim 32

A performance monitoring system for continuously monitoring the amplitude non-linearity in a receiver as caused by the undesired interaction in the receiver by two signals of different frequency, said monitoring system being operable while the receiver is in normal service without significantly interfering with the normal service thereof comprising a white noise source, a high frequency modulator associated with the noise source for modulating the output of said noise source at a high frequency F2, first coupling means for injecting the modulated white noise into the receiver input, means for producing a carrier signal of fixed frequency and for varying the amplitude of said carrier signal, said carrier signal having a frequency which is tuned away from the operating pass-band of the receiver, second coupling means for injecting said carrier signal of varying amplitude into the receiver input, third coupling means associated with the receiver output, a narrow band filter arranged to receive energy from said third coupling means, square-law detection means in said system ahead of said narrow band filter and preferably included in the receiver being monitored, a logarithmic voltage controlled attenuator connected to said narrow band filter, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of the Modulated white noise from said noise source, and read out means in said monitoring system connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for providing information as to the amplitude non-linearity of said receiver.

Claim 33

A performance monitoring system for continuously monitoring the amplitude non-linearity in a receiver as caused by the undesired interaction in the receiver by two signals of different frequency, said monitoring system being operable while the receiver is in normal service without significantly interfering with the normal service thereof comprising a white noise source, a high frequency modulator associated with the noise source for modulating the output of said noise source at a high frequency F2, first coupling means for injecting the modulated white noise into the receiver input, means for producing a carrier signal of fixed frequency and for varying the amplitude of said carrier signal, said carrier signal having a frequency which is tuned away from the operating pass-band of the receiver, second coupling means for injecting said carrier signal of varying amplitude into the receiver input, third coupling means associated with the receiver output, a narrow band filter arranged to receive energy from said third coupling means, square-law detection means in said system ahead of said narrow band filter and preferably included in the receiver being monitored, a logarithmic voltage controlled attenuator connected to said narrow band filter, a fast-acting automatic gain control feedback loop which is connected to the attenuator for keeping the attenuator output constant, said fast acting A.G.C. loop being sufficiently fast to follow the changes in the root mean square value of the Modulated white noise from said noise source, and read out means in said monitoring system connected to said feedback loop and responsive to the level of the alternating voltage in said feedback loop for providing information as to the amplitude non-linearity of said receiver.

Claim 34

A performance monitoring system as claimed in claim 21, in which said read out means is preferably narrow band responsive and is tuned to be responsive at the switching rate F1.

Claim 35

A monitoring system for continuously monitoring a parameter of a medium through which radio frequency energy can be transmitted comprising a white noise source, means for feeding noise energy from said source through the medium to be monitored, means for changing the noise source back and forth between first and second conditions, a logarithmic controllable attenuator, means for connecting said attenuator to receive the noise energy which has passed through said transmission medium, a fast-acting automatic gain control feedback loop connected to said attenuator to keept the attentuator output effectively constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in root mean square value of the noise energy, and read out means coupled to said A.G.C. loop and indicating the ratio of the levels of the signals in said A.G.C. loop under said first and second conditions, respectively.

Claim 36

A monitoring system for continuously monitoring a parameter of a medium through which radio frequency energy can be transmitted comprising a white noise source, means for feeding noise energy from said source through the medium to be monitored, means for changing the noise source back and forth between first and second conditions, a logarithmic controllable attenuator, means for connecting said attenuator to receive the noise energy which has passed through said transmission medium, a fast-acting automatic gain control feedback loop connected to said attenuator to keept the attentuator output effectively constant, said fast-acting A.G.C. loop being sufficiently fast to follow the changes in root mean square value of the noise energy, and read out means coupled to said A.G.C. loop and indicating the ratio of the levels of the signals in said A.G.C. loop under said first and second conditions, respectively.