a broadband multibit digital radio - frequency signal is synthesized digitally . to convert the digital signal to a high - power analog signal for rf transmission . each bit of the digital signal is first separately amplified using a fast switching amplifier with a controlled dc power supply voltage . the dc voltages are weighted to match the significance of the bits , and controlled by a set of calibrated dc reference sources to maintain high precision . the amplified digital signals from the various bits are then combined and passed through an appropriate analog filter to generate the rf signal to be transmitted . such a signal can exhibit broad bandwidth , high dynamic range , excellent linearity , and low noise . preferred embodiments of this system can incorporate superconducting electronic elements . for ultimate precision , a set of primary or secondary dc voltage standards can be used to regulate the switching amplifier supply voltages .