Abstract: IN MODERN HIGH-FREQUENCY ELECTRONIC SYSTEMS SUCH AS COMMUNICATION, RADAR, AND PRECISION INSTRUMENTS, THE PHASE NOISE OF SIGNAL SOURCES IS ONE OF THE CRITICAL PARAMETERS DETERMINING SYSTEM PERFORMANCE. DEGRADATION IN PHASE NOISE CAN LEAD TO INCREASED BIT ERROR RATES IN COMMUNICATION, REDUCED RADAR RESOLUTION, AND EVEN COMPROMISED MEASUREMENT ACCURACY IN INSTRUMENTS. AS A WIDELY USED FREQUENCY SOURCE, THE PHASE NOISE CHARACTERISTICS OF THE OUTPUT SIGNAL FROM A DIRECT DIGITAL SYNTHESIZER (DDS) ARE CLOSELY RELATED TO THE QUALITY OF ITS INPUT CLOCK. SAPPHIRE RESONATOR OSCILLATORS, WHICH EMPLOY HIGH-Q SAPPHIRE RESONATORS TO CONSTRUCT OSCILLATION CIRCUITS, DELIVER ULTRA-LOW PHASE NOISE SIGNALS WHILE AVOIDING THE PHASE NOISE DEGRADATION ASSOCIATED WITH TRADITIONAL FREQUENCY MULTIPLICATION METHODS. IN THIS STUDY, A SAPPHIRE RESONATOR OSCILLATOR (SRO) IS UTILIZED AS THE DDS CLOCK SOURCE. BY DIVIDING THE 10 GHZ OUTPUT OF THE SRO DOWN TO 5 GHZ AS THE DDS CLOCK INPUT, TEST RESULTS DEMONSTRATE SIGNIFICANT IMPROVEMENTS IN PHASE NOISE AT ALL OUTPUT FREQUENCIES OF THE DDS, THEREBY MARKEDLY ENHANCING SYSTEM PERFORMANCE.