Narrow-band direct digital synthesizers

Direct digital synthesizers (DDS) are widely used in the synthesis of frequencies and signals. If a narrow bandwidth is needed, the frequency conversion methods using phase shifting technique are useful. These methods allow us to increase the maximal synthesized frequency, to decrease the cost and power consumption of the synthesizer without loss in accuracy of synthesized waveform. We offer a new type of synthesizer-direct digital synthesizer with samples commutation (DDS SC), using a multilevel digitally controlled phase shifter. We obtained the mathematical expressions for the Fourier coefficients of the output signal in DDS with sine wave, two level (square wave) and multilevel digitally controlled phase shifters, when the DDS operates in the frequency synthesizing mode and defined the possibility of using these DDS for generation of a signal with linear frequency modulation (LFM).