Analogue-to-digital converter using phase modulation

Abstract

An ultrahigh-speed analog-to-digital converter that does not use optical signals is implemented by means of simple circuit configurations. To achieve this, phase differences between a carrier and modulated signals are detected, the modulated signals having been obtained by modulating the phase of the carrier with an analog signal. Analog-to-digital conversion is then performed by applying binary weighting to the modulation factors of the phase modulations. Alternatively, different relative delays are applied stepwise in 2.sup.n -1 stages (where n is the resolution) between the carrier and the signal that has been phase modulated by the analog signal. The phase of the signals with these delays and the phase of the signal without any delay are respectively compared in 2.sup.n -1 stages. An n-bit digital signal is formed and output on the basis of the results of these comparisons. The carrier may also be respectively shifted in a plurality of stages n by means of delay elements, and the phases of the outputs of the n phase modulations may be respectively compared with the phase of the carrier. An n-bit digital signal is formed and output on the basis of the results of these comparisons. In this case, the amount of hardware can be decreased by combining this method with the previously described method. High-speed analog-to-digital conversion can be performed in these ways, and improvements in precision, accuracy and operating frequency can be achieved. Noise rejection is excellent, and improved signal quality and conversion efficiency can be obtained.