Method and an apparatus for measuring high-frequency intermodulation products
OwnerJan Verspechtinventor
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Abstract
Novel excitation signals are specifically designed for testing a nonlinear device-under-test such that all of the desired intermodulation products are measurable after being converted by a sampling frequency convertor. This is achieved by using excitation frequencies which are equal to an integer multiple of the sampling frequency of the sampling frequency convertor plus or minus small frequency offsets. The offset frequencies are carefully choosen such that the frequencies of all the significant intermodulation products after being converted by the sampling frequency convertor are within the bandwidth of the sampling frequency convertor output.
Claims3
A method for measuring high-frequency intermodulation products that are generated by a device-under-test comprising the steps of:
- applying multitone excitation signals to the signal ports of said device-under-test
- sensing and frequency converting the excitation and response signals of said device under-test by sampling said signals using a sampling frequency convertor that samples at a specific sampling rate, whereby said multitone excitation signals contain spectral components at a discrete set of frequencies;
- and whereby the response signals contain intermodulation products with significant power upto a specific order;
- and whereby each of said frequencies of said discrete set is equal to an integer multiple of said sampling rate plus or minus a frequency offset that is substantially smaller than said sampling rate;
- and whereby said frequency offsets are chosen such that the frequencies of the response signals appearing at the output of said sampling frequency convertor are within the output bandwidth of said sampling frequency convertor.
The method described in 1 whereby said frequency offsets are chosen such that the minimum distance between any two frequencies at said output of said sampling frequency convertor is larger than a predetermined frequency resolution.
The method described in 1 whereby each of said small frequency offsets is proportional to the corresponding frequency of said multitone excitation signal.
Dependencies are inferred from the claim text.