| 摘要 |
<p>An adaptive analogue-to-digital converter arrangement comprises an analogue-to-digital converter (21) preceded by a variable-gain amplifier (4). In order to provide an accurate measure of the relative gain of the amplifier at each gain setting the output signal of an a.c. reference signal source (12) is frequency-multiplexed with the arrangement input signal applied to an input (1). After conversion to digital form by means of the A/D converter (21) the multiplexed signal is separated into its two components by means of filters (23,24), these being directed to respective bit fields (2A,2B) of an output (2), the reference component after amplitude detection (25). The output amplitude of the reference source may be varied inversely with the gain of the amplifier (4) by means of a feedback loop (32,33) which is activated alternately with variation of the gain of the amplifier, a data processor (36) then being provided to calculate the cumulative variation in gain from the content of the reference signal bit field (2B) immediately before and after each gain variation. <IMAGE></p> |
