GB1341852A - Performance checking and measuring devices and methods for signal channels - Google Patents

Abstract

1341852 Measuring peak/average ratio MARCONI INSTRUMENTS Ltd 19 April 1971 [26 March 1970] 14714/70 Headings G1U A pulse train Fig. 6 having a mark/space ratio proportional to (V peak /V average - 1) where V peak is the peak voltage, and V average is the average voltage, of an input waveform 1, Fig.1, is produced by detecting both the peak and average voltages by diode-capacitor detectors 2, 3 by applying the peak voltage to an integrator 6 for the duration T 1 of a positive clock pulse, Fig.2, applied to a terminal 17, to produce a negative going voltage Fig.4, at the integrator output, then applying the average voltage to the integrator 6 until its output becomes zero, and then producing a pulse in the output pulse train Fig.6, which lasts from the instant the integrator output Fig.4, becomes zero to the beginning of the next positive clock pulse, Fig.2, whereupon the whole process repeats. The clock pulses Fig.2, are applied via a terminal 17 directly to a switch 7 and via an inverter 18 and a gate 16 to a switch 8. For the duration of a positive clock pulse switch 7 is opened and the peak voltage is applied to the integrator. Its output is applied to a sign detector 10, which, since the integrator output starts from zero and proceeds negatively, Fig.4, produces a positive output. This positive output tends to open gate 16 but has no effect since the inverted clock pulse applied to it is negative. At the end of the positive clock pulse switch 7 closes, and gate 16 opens to open switch 8. The average voltage is now applied to the integrator, whose output now rises. When it reaches zero, the output of the sign detector 10 changes to negative thereby closing gate 16 and removing the average voltage from the input of the integrator. The output of the sign detector 10 is also applied via an inverter 12 and a gate 14 - which is open since a negative clock pulse is present on terminal 17 - to produce an output pulse, Fig.6, on a terminal 21 lasting until the next positive clock pulse arrives. It can be shown that the mark/space ratio of the resulting pulse train Fig.6, is as stated above, and it may be displayed on an average reading meter.