An apparatus for frequency characterization of an electronic system , comprising: two terminals configured to couple to the electronic system ; a control circuit configured to generate a test signal , wherein the test signal is a square-wave signal, and wherein a length of a square-wave window of the square-wave signal is set depending on a desired measurable frequency range; a coupling circuit comprising an adjustable impedance and a switch which are coupled in series, wherein end nodes of the coupling circuit are coupled to the two terminals , and wherein the switch is configured to electrically couple the two terminals based on the test signal ; and a measurement circuit configured to generate a first measurement signal representing the current through the coupling circuit , and a second measurement signal representing the voltage across the coupling circuit , wherein the measurement circuit is further configured to generate the first measurement signal and the second measurement signal synchronously with the test signal , wherein the control circuit is further configured to: based on a first cross-correlation of the first measurement signal and the test signal as well as a subsequent Fourier transformation of the result of the first cross-correlation, generate a first signal representing a frequency course of the current through the coupling circuit ; and based on a second cross-correlation of the second measurement signal and the test signal as well as a subsequent Fourier transformation of the result of the second cross-correlation, generate a second signal representing a frequency course of the voltage across the coupling circuit . two terminals configured to couple to the electronic system ; a control circuit configured to generate a test signal , wherein the test signal is a square-wave signal, and wherein a length of a square-wave window of the square-wave signal is set depending on a desired measurable frequency range; a coupling circuit comprising an adjustable impedance and a switch which are coupled in series, wherein end nodes of the coupling circuit are coupled to the two terminals , and wherein the switch is configured to electrically couple the two terminals based on the test signal ; and a measurement circuit configured to generate a first measurement signal representing the current through the coupling circuit , and a second measurement signal representing the voltage across the coupling circuit , wherein the measurement circuit is further configured to generate the first measurement signal and the second measurement signal synchronously with the test signal , wherein the control circuit is further configured to: based on a first cross-correlation of the first measurement signal and the test signal as well as a subsequent Fourier transformation of the result of the first cross-correlation, generate a first signal representing a frequency course of the current through the coupling circuit ; and based on a second cross-correlation of the second measurement signal and the test signal as well as a subsequent Fourier transformation of the result of the second cross-correlation, generate a second signal representing a frequency course of the voltage across the coupling circuit . based on a first cross-correlation of the first measurement signal and the test signal as well as a subsequent Fourier transformation of the result of the first cross-correlation, generate a first signal representing a frequency course of the current through the coupling circuit ; and based on a second cross-correlation of the second measurement signal and the test signal as well as a subsequent Fourier transformation of the result of the second cross-correlation, generate a second signal representing a frequency course of the voltage across the coupling circuit . <EOS>