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Amplitude Measurement Method for Periodic Signal

IP.com Disclosure Number: IPCOM000115816D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 121K

Publishing Venue

IBM

Related People

Liu, CC: AUTHOR

Abstract

This article describes a digital sampling method for measuring the fundamental amplitude and odd harmonic component amplitude in a periodic burst signal. The frequency of the sampling clock is uniquely related to the fundamental component of the burst. No phase coherence is assumed between the sampling clock and the burst. Therefore, no phase lock loop is required. This method can be described in two steps: 1. the resultant burst amplitude and the third harmonic amplitude are measured, separately, and 2. the fundamental amplitude is recovered by using a new digital algorithm and with the amplitude information already acquired in (1). This method is immune to D.C. offset and even harmonics in the burst.

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Amplitude Measurement Method for Periodic Signal

      This article describes a digital sampling method for measuring
the fundamental amplitude and odd harmonic component amplitude in a
periodic burst signal.  The frequency of the sampling clock is
uniquely
related to the fundamental component of the burst.  No phase
coherence
is assumed between the sampling clock and the burst.  Therefore, no
phase
lock loop is required.  This method can be described in two steps:
  1.  the resultant burst amplitude and the third harmonic amplitude
       are measured, separately, and
  2.  the fundamental amplitude is recovered by using a new digital
       algorithm and with the amplitude information already acquired
       in (1).
  This method is immune to D.C. offset and even harmonics in the
burst.

Theory of Operation - A simplified block diagram of the invention is
shown in Fig. 1.  Described below are theory of operations,
algorithms,
and a basic accumulator configuration:

      A periodic burst signal is applied to a variable gain
amplifier, VGA, and a filter, and is sampled by a flash
Analog-to-Digital Converter (ADC).  The sampling clock frequency is F
sub S, and a sampling period of T, where T = 1 / F sub S.

      For this illustration, consider a burst consists of D.C.
offset, fundamental, second and third harmonics.  Harmonics higher
than the third are removed by the filter.  Signal samples are
selectively steered into two accumulators, S-Accumulator and
T-Accumulator, by their respective clock pulses, lbrace phi sub S,
phi sub T rbrace.  No phase coherence is assumed between the sampling
clock pulses and the burst.

      The S-Accumulator, is for the measurement of the resultant
amplitude of the burst, whereas the T-Accumulator for the amplitude
of the third harmonic.  Each accumulator produces a pair of output,
an in-phase (I) component, and a quadrature (Q) component,
respectively.  Then, the two respective pairs are processed further
through a 'DIFFerence' and a 'SUM' block as shown.  Finally, a new
pair, lbrace I sub 1, Q sub 1 rbrace, is obtained which contains the
fundamental amplitude information only.

Basic Accumulator - Fig. 2 shows a basic accumulator configuration
that can be used for each of the accumulator.  It consists of six
adders of which four at the input (U11, U12, U21, U22), and two at
the output (V1, V2).

Sampling Clock Frequency - The relation between the sampling clock
frequency, F sub S, and the frequency of t...