An apparatus for frequency characterization of an electronic system, comprising: two terminals (110, 120) 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 (141, 142) of the coupling circuit are coupled to the two terminals (110, 120), and wherein the switch is configured to electrically couple the two terminals (110, 120) based on the test signal; and a measurement circuit (270, 280) 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 (270, 280) 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 (110, 120) 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 (141, 142) of the coupling circuit are coupled to the two terminals (110, 120), and wherein the switch is configured to electrically couple the two terminals (110, 120) based on the test signal; and a measurement circuit (270, 280) 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 (270, 280) 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.