Patent ID: 7391349

Claim:
A test apparatus for testing an analog/digital converter (AD converter), comprising: a memory which provides a digital test signal at its output, a digital/analog converter (DA converter) which converts the digital test signal into a sinusoidal analog test signal of frequency ω 0 which is fed to the AD converter to be tested, as a result of which the AD converter to be tested outputs an N-bit digital test response, a frequency converter which takes the digital test signal and produces a sinusoidal m-bit digital reference signal at the frequency Ω, wherein Ω is equal to or an integer multiple of the frequency ω 0 , a frequency selector which contains a phase shifter, two digital multipliers and two digital filters, wherein the phase shifter shifts the digital reference signal through π/2, wherein both multipliers respectively have two input channels and an output channel, wherein their first input channel is respectively connected to the digital test response, and wherein the second input channel has the digital reference signal connected to it in the case of the first multiplier and has the output channel from the phase shifter connected to it in the case of the second multiplier, wherein the filters determine and output the DC components of the output signals from the multipliers, an evaluation/control unit which receives output signals from the frequency selector.