A signal generating device comprising: a digital signal processing unit; two digital-to-analog converters, DACs, operating with a bandwidth of f c /2; and an analog multiplexer that is configured to alternatingly connect with a frequency f c /2 an output signal of one of the two DACs and an output signal of the other of the two DACs to an output, wherein the digital signal processing unit includes: means for generating a first signal that is equal to a sum of a parallel shifted signal multiplied by a constant and a low-frequency signal subtracted by a folded signal; and means for generating a second signal that is equal to the low-frequency signal subtracted by the folded signal and subtracted by the parallel shifted signal multiplied by the constant, that the low-frequency signal is a component of a desired output signal containing all frequencies of the desired output signal having an absolute value of f c /2 or less, wherein the desired output signal has an upper limit frequency of less than f c, the folded signal is defined as, a signal in which a positive frequency component of the desired output signal, having an absolute value of a frequency being substantially f c /2 or more, is shifted by -f c on a frequency axis and in which a negative frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by +f c on the frequency axis, and the parallel shifted signal is defined as a signal in which the positive frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by -f c /2 on the frequency axis and in which the negative frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by +f c /2 on the frequency axis and wherein: the digital signal processing unit connected to the two DACs is further configured to input the first signal into one of the two DACs and the second signal into the other of the two DACs. a digital signal processing unit; two digital-to-analog converters, DACs, operating with a bandwidth of f c /2; and an analog multiplexer that is configured to alternatingly connect with a frequency f c /2 an output signal of one of the two DACs and an output signal of the other of the two DACs to an output, wherein the digital signal processing unit includes: means for generating a first signal that is equal to a sum of a parallel shifted signal multiplied by a constant and a low-frequency signal subtracted by a folded signal; and means for generating a second signal that is equal to the low-frequency signal subtracted by the folded signal and subtracted by the parallel shifted signal multiplied by the constant, that the low-frequency signal is a component of a desired output signal containing all frequencies of the desired output signal having an absolute value of f c /2 or less, wherein the desired output signal has an upper limit frequency of less than f c, the folded signal is defined as, a signal in which a positive frequency component of the desired output signal, having an absolute value of a frequency being substantially f c /2 or more, is shifted by -f c on a frequency axis and in which a negative frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by +f c on the frequency axis, and the parallel shifted signal is defined as a signal in which the positive frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by -f c /2 on the frequency axis and in which the negative frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by +f c /2 on the frequency axis means for generating a first signal that is equal to a sum of a parallel shifted signal multiplied by a constant and a low-frequency signal subtracted by a folded signal; and means for generating a second signal that is equal to the low-frequency signal subtracted by the folded signal and subtracted by the parallel shifted signal multiplied by the constant, that the low-frequency signal is a component of a desired output signal containing all frequencies of the desired output signal having an absolute value of f c /2 or less, wherein the desired output signal has an upper limit frequency of less than f c, the folded signal is defined as, a signal in which a positive frequency component of the desired output signal, having an absolute value of a frequency being substantially f c /2 or more, is shifted by -f c on a frequency axis and in which a negative frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by +f c on the frequency axis, and the parallel shifted signal is defined as a signal in which the positive frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by -f c /2 on the frequency axis and in which the negative frequency component of the desired output signal, having an absolute value of a frequency being substantially fc/2 or more, is shifted by +f c /2 on the frequency axis and wherein: the digital signal processing unit connected to the two DACs is further configured to input the first signal into one of the two DACs and the second signal into the other of the two DACs.