dc1959b-a DC1959B-A DC1959B-A LTC6948-1 Demo Board | Ultralow Noise and Spurious 373MHz to 3.74GHz Frac-N Synthesizer with Integrated VCO, (Requires DC590 or DC2026) Demonstration circuit 1959B features the LTC6948, an Ultralow Noise and Spurious Fractional-N Synthesizer with Integrated VCO.