Frequently, voltage reference stability and noise defi nemeasurement limits in instrumentation systems. In particular,reference noise often sets stable resolution limits.Reference voltages have decreased with the continuingdrop in system power supply voltages, making referencenoise increasingly important. The compressed signalprocessing range mandates a commensurate reductionin reference noise to maintain resolution. Noise ultimatelytranslates into quantization uncertainty in A to D converters,introducing jitter in applications such as scales, inertialnavigation systems, infrared thermography, DVMs andmedical imaging apparatus. A new low voltage reference,the LTC6655, has only 0.3ppm (775nV) noise at 2.5VOUT.Figure 1 lists salient specifi cations in tabular form. Accuracyand temperature coeffi cient are characteristic ofhigh grade, low voltage references. 0.1Hz to 10Hz noise,particularly noteworthy, is unequalled by any low voltageelectronic reference.
標(biāo)簽：
低噪聲
電壓基準(zhǔn)
噪聲測量
上傳時(shí)間：
2013-10-30
上傳用戶：wxhwjf
Abstract-The effect of the companding process on QAM signals
has been under investigation for the past several years. The
compander, included in the PCM telephone network to improve
voice performance, has an unusual affect on digital QAM data
signals which are transmitted over the same channel. The quantization
noise, generated by the companding process which is multiplicative
(and asymmetric), degrades the detectability performance
of the outermost points of the QAM constellation more
than that of the inner points.
The combined effect of the companding noise and the inherent
white gaussian noise of the system, leads us to a re-examination of
signal constellation design.
In this paper we investigate the detectability performance of a
number of candidates for signal constellations including, a typical
rectangular QAM constellation, the same constellation with the
addition of a smear-desmear operation, and two new improved
QAM constellation designs with two-dimensional warpi
標(biāo)簽：
investigation
Abstract-The
companding
the
上傳時(shí)間：
2013-12-20
上傳用戶：英雄
