Numerically Controlled Oscillators (NCO), also called Direct Digital Synthesizers (DDS), offer several advantages over other types of oscillators in terms of accuracy, stability and reliability. NCOs provide a flexible architecture that enables easy programmability such as on-the-fly frequency/phase. NCOs are used in many communications systems including digital up/down converters used in 3G wireless and software radio systems, digital PLLs, radar systems, drivers for optical or acoustic transmissions, and multilevel FSK/PSK modulators/demodulators.
Lattice provides a parameterizable NCO IP core that supports multiple channels and a Quadrature Amplitude Modulation (QAM) mode, in addition to other usual configurations. The resource utilization and performance trade-off can be tuned by configuring different parameters of the IP core to obtain the optimal Spurious Free Dynamic Range (SFDR) result. The Lattice NCO core offers a variety of memory reduction schemes and mechanisms for SFDR improvement.
- Supports single or multi channel operation up to 16 channels
- Run time variable phase increment input Δθ and phase offset input φ
- Up to 32-bit user-configurable phase resolution
- Up to 20-bit user-configurable quantizer resolution
- Up to 32-bit user-configurable amplitude resolution
- User-configurable memory saving architectures – 1/2 wave, 1/4 wave or full wave
- User-selectable sum of angles (SOA) optimization for memory saving
- Up to 4-bit user-selectable phase dithering correction
- User-selectable trigonometric correction for SFDR improvement
- Option for truncating or rounding the quantizer output when neither dithering nor trigonometric correction is used.
- User-selectable QAM mode support
- Provides high-SFDR up to 115 dB
- Provides sine, cosine or quadrature outputs.
- User configurable output polarity
Block Diagram of the Numerically Controlled Oscillator IP Core