Signal demodulation method and apparatus therefor using multi-ary sampling

摘要

A signal demodulation apparatus using a multi-ary sampling for beam formation of a received signal reduces a difference between a sampling point of time of an in-phase signal and a sampling point of time of a quadrature signal due to an existing secondary sampling method. Each of a plurality of analog-to-digital converters produces a first in-phase signal and at least two first quadrature signals adjacent to the first in-phase signal by sampling each input signal input via a plurality of channels at a sampling point of time having a sampling period of the input signal and other sampling points of time having a sampling interval smaller than the sampling period of the input signal. A quadrature component calculator of each channel produces second quadrature signals in which an error due to a difference between the sampling point of time of the first in-phase signal and the sampling points of time of the first quadrature signal is reduced. A first accumulator accumulates first in-phase signals of all the channels to produce a second in-phase signal and a second accumulator accumulates second quadrature signals of all the channels to produce a third quadrature signal. The second in-phase signal and the third quadrature signal are used for detection of an envelope signal of the received signal. The apparatus can be used in a sonar and a radar as well as an ultrasonic image apparatus, rendering an effect capable of obtaining an in-phase signal and a quadrature signal from which an error due to a difference between sampling points of time is remarkably reduced compared with the existing secondary sampling method. <IMAGE>