Method for determination of errors in analogue-digital conversion

A method for determining time errors in connection with analogue-digital conversion of quadrature detected signals, comprising the steps of:

• feeding a periodically repeated signal, whose frequency is changed during each period, to a device whose time error is to be determined;
• quadrature detecting the signal, whereby two quadrature components are formed;
• sampling the quadrature components and converting the samples to digital form, whereby the quadrature components for every period of the signal are each sampled at at least two different time points;
• Fourier transforming those samples from a number of periods of the signal associated with the determined time points to form a spectrum which contains expressions that describe a fundamental tone of the signal and an image tone;
• and
• determining the time error based on at least two time points according to a relationship between the fundamental tone and the image tone based on the expressions, wherein
• the expressions describe the fundamental tone and image tone of the signal with regard to amplitude and phase, and
• the expressions are ##EQU10## where .DELTA.t is the time error, .omega. is an angular frequency of the signal, t is a time distance between a start time point of the signal and the sampling time points and .mu. is an angular frequency change of the signal per time unit.