Method for characterizing high-frequency mixers
View Patent ↗Novel excitation signals are specifically designed for testing a high-frequency mixer such that all of the desired intermodulation products are measurable after being converted by a sampling frequency converter. 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 converter are within the bandwidth of the sampling frequency converter output.
1. A method comprising the steps of:
providing a sampling frequency converter; and
calculating a first frequency and a second frequency such that a first predetermined integer times said first frequency plus a second predetermined integer times said second frequency is smaller than the output bandwidth of said sampling frequency converter; and
calculating a local oscillator frequency that equals plus or minus said first frequency plus a multiple of the sampling frequency of said sampling frequency converter; and
calculating an input signal frequency that equals plus or minus said second frequency plus a multiple of the sampling frequency of said sampling frequency converter; and
generating a local oscillator signal that contains spectral components having frequencies that are equal to said local oscillator frequency or to a multiple of said local oscillator frequency; and
generating an input signal that contains spectral components having frequencies that are equal to said input signal frequency or to a multiple of said input signal frequency; and
applying said local oscillator signal to the local oscillator terminal of a high-frequency mixer; and
applying said input signal to the input signal terminal of said high-frequency mixer; and
sensing the response signals that are generated at the terminals of said high-frequency mixer; and
frequency converting said response signals to intermediate frequency signals by sampling said response signals using said sampling frequency converter; and
generating digitized values of said intermediate frequency signals; and
storing said digitized values in the memory of a computer;
whereby said digitized values are used for characterizing the performance of said high-frequency mixer.
2. The method described in claim 1 further comprising the steps of:
calculating a third frequency such that said first predetermined integer times said first frequency plus said second predetermined integer times said second frequency plus a third predetermined integer times said third frequency is smaller than said output bandwidth of said sampling frequency converter; and
adding spectral components to said input signal such that said added spectral components have frequencies that are equal to said input signal frequency plus or minus said third frequency or to said input signal frequency plus or minus multiples of said third frequency.
3. The method described in claim 1 further comprising the steps of:
calculating a multitude of frequencies such that said first predetermined integer times said first frequency plus said second predetermined integer times said second frequency plus each of the frequencies of said multitude of frequencies times a predetermined integer is smaller than said output bandwidth of said sampling frequency converter; and
adding spectral components to said input signal such that said added spectral components have frequencies that are equal to said input signal frequency plus linear combinations with integer coefficients of said multitude of frequencies.