Measurement circuit and electronic device

Abstract

Provided is a measurement circuit that is provided in the same electronic device as a circuit under measurement, comprises a difference generating section and an integrating section, and performs a sigma-delta AD conversion on a signal under measurement output by the circuit under measurement, the measurement circuit further comprising a sampling section that is provided between an output end of the difference generating section and an input end of the integrating section, detects a level of a signal input thereto at predetermined sampling intervals, and outputs a sampled signal corresponding to the detected signal level. This measurement circuit is used to easily perform a sigma-delta AD conversion on a high-frequency signal under measurement.

1 . A measurement circuit that is provided in the same electronic device as a circuit under measurement, comprises a difference generating section and an integrating section, and performs a sigma-delta AD conversion on a signal under measurement output by the circuit under measurement, the measurement circuit further comprising:
 a sampling section that is provided between an output end of the difference generating section and an input end of the integrating section, detects a level of a signal input thereto at predetermined sampling intervals, and outputs a sampled signal corresponding to the detected signal level.   
     
     
         2 . The measurement circuit according to  claim 1 , further comprising a quantizing section and a feedback section, wherein
 the difference generating section decreases a signal level of the signal under measurement according to a feedback signal input thereto, and inputs the resulting signal to the sampling section,   the integrating section integrates the signal level of the sampled signal output by the sampling section,   the quantizing section outputs a digital signal corresponding to the integrated value from the integrating section, and   when the quantizing section outputs the digital signal, the feedback section inputs to the difference generating section the feedback signal with a signal level corresponding to a value of the digital signal.   
     
     
         3 . The measurement circuit according to  claim 1 , further comprising a quantizing section, a feedback section, and an error calculating section, wherein
 the difference generating section decreases a signal level of the signal under measurement according to a feedback signal input thereto, and outputs the resulting signal,   the quantizing section outputs a digital signal corresponding to a signal level of a signal output by the difference generating section,   the error calculating section calculates an error between the level of the signal output by the difference generating section and a value of the digital signal,   the integrating section integrates the error calculated by the error calculating section, and   the feedback section inputs to the difference generating section the feedback signal with a signal level corresponding to the integrated value from the integrating section.   
     
     
         4 . The measurement circuit according to  claim 3 , wherein
 the sampling section is provided between an output end of the difference generating section and an input end of the error calculating section.   
     
     
         5 . The measurement circuit according to  claim 3 , further comprising a branching path that branches the signal output by the difference generating section and inputs the resulting signals to the quantizing section and the error calculating section, wherein
 the sampling section is provided between the branching path and an input end of the error calculating section.   
     
     
         6 . The measurement circuit according to  claim 2 , wherein
 the sampling section detects the signal level output by the difference generating section, with an operational period that is greater than a period of the signal under measurement.   
     
     
         7 . The measurement circuit according to  claim 6 , wherein
 the quantizing section detects a value of the integration result from the integrating section, with a period equal to the operational period of the sampling section, and outputs a digital signal corresponding to the detected value.   
     
     
         8 . The measurement circuit according to  claim 2 , comprising a plurality of the sampling sections that are connected in cascade and that each have a different aperture timing for acquiring a level of a signal input thereto. 
     
     
         9 . The measurement circuit according to  claim 1 , wherein
 the sampling section outputs a sampled signal obtained by holding the signal level detected at each sampling interval for a time period corresponding to the sampling interval.   
     
     
         10 . An electronic device comprising:
 the measurement circuit according to  claim 1 ; and   the circuit under measurement.   
     
     
         11 . A measurement circuit that comprises a difference generating section and an integrating section and that performs a sigma-delta AD conversion on a signal under measurement, the measurement circuit further comprising:
 a sampling section that is provided between an output end of the difference generating section and an input end of the integrating section, detects a level of a signal input thereto at predetermined sampling intervals, and outputs a sampled signal obtained by holding the signal level detected at each sampling interval for a time period corresponding to the sampling interval.