Measuring amplitude of sparsely sampled sinusoidal signal

Abstract

Sparse sampling of an analog signal is desirable because it allows a large number of analog signals to be monitored using a minimum of electronics. The analog signals may be multiplexed and the multiplexed signal applied to a single analog-to-digital converter (ADC) driving a single digital processor. However, such sparse sampling undesirably lengthens the time it takes to get an accurate measurement of the signal. This delay is minimized by Hilbert transforming the digitized signal 16 to produce an in-phase signal I and a quadrature-phase signal Q, and by measuring I.sup.2 +Q.sup.2. I.sup.2 +Q.sup.2 is the square of the amplitude of the input signal. The input signal 12 is sampled at about four times the signal's frequency. DC bias is eliminated in a two-delay delay-subtracter dc blocker 18B. The de-blocked signal 20 is applied to a two-delay Hilbert transformer 22. Only five samples are required to accurately measure the amplitude of the input signal 12. This is only two samples more than the theoretical minimum.

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