Introduction
The ability to accurately produce and control waveforms of various frequencies and profiles has become a key requirement across numerous industries. Designers have options like PLL-based techniques and DAC programming, but DDS is popular due to its ability to generate high-resolution, programmable analog waveforms with compact, low-cost single-chip ICs.
DDS offers agile, low-phase-noise frequency sources for communications and frequency stimuli for industrial and biomedical equipment.
Direct digital synthesis (DDS) is a method of producing an analog waveform—usually a sine wave—by generating a time-varying signal in digital form and then performing a digital-to-analog conversion.
DDS is used in applications such as signal generation, local oscillators in communication systems, function generators, mixers, modulators, sound synthesizers and as part of a digital phase-locked loop.
How does a DDS device create a sine wave?
The main components of DDS device are a phase accumulator, a means of phase-to-amplitude conversion (often a sine look-up table), and a DAC. These blocks are represented here,
A DDS produces a sine wave at a given frequency. The frequency depends on two variables, the reference-clock frequency and the binary number programmed into the frequency register.
The binary number in the frequency register provides the main input to the phase accumulator. If a sine look-up table is used, the phase accumulator computes a phase (angle) address for the look-up table, which outputs the digital value of amplitude—corresponding to the sine of that phase angle—to the DAC. The DAC, in turn, converts that number to a corresponding value of analog voltage or current. To generate a fixed-frequency sine wave, a constant value (the phase increment—which is determined by the binary number) is added to the phase accumulator with each clock cycle. If the phase increment is large, the phase accumulator will step quickly through the sine look-up table and thus generate a high frequency sine wave. If the phase increment is small, the phase accumulator will take many more steps, accordingly, generating a slower waveform.
What kind of outputs can I generate with a typical DDS device?
DDS devices are not limited to purely sinusoidal outputs. Figure shows the square-, triangular-, and sinusoidal outputs available from an AD9833.
What are the main benefits of using a DDS?
DDS devices can be programmed through a high-speed serial peripheral-interface (SPI) and need only an external clock to generate simple sine waves. DDS devices are now available that can generate frequencies from less than 1 Hz up to 400 MHz (based on a 1-GHz clock).
The benefits of their low power, low cost, and single small package, combined with their inherent excellent performance and the ability to digitally program (and reprogram) the output waveform, make DDS devices an extremely attractive solution—preferable to less-flexible solutions comprising aggregations of discrete elements.
Key performance specification of a DDS based system:
Phase noise, jitter, and spurious-free dynamic range (SFDR).
Phase noise: Noise in a sampled system is influenced by several factors. Reference-clock jitter manifests as phase noise in a DDS system, while phase truncation introduces errors depending on the chosen code word. Exact ratios expressed by truncated binary-coded words have no truncation error, but ratios requiring more bits produce phase noise truncation errors visible as spurs in spectral plots. Their magnitudes and distribution depend on the code word chosen.
The DAC adds noise through quantization and linearity errors, which can lead to noise and harmonic distortion.
Jitter: Jitter is the dynamic displacement of digital signal edges from their long-term average positions, measured in degrees rms. Oscillator jitter comes from thermal noise, instability in electronics, and external interference via power sources, ground, and connections. RF interference from nearby transmitters and magnetic or electric fields also affect the oscillator. Simple components like amplifiers or buffers can add jitter to signals.
The output of a DDS device will add a certain amount of jitter. Since every clock will already have an intrinsic level of jitter, choosing an oscillator with low jitter is critical to begin with. Dividing down the frequency of a high-frequency clock is one way to reduce jitter. With frequency division, the same amount of jitter occurs within a longer period, reducing its percentage of system time.
Spurious-Free Dynamic Range (SFDR): refers to the ratio (decibels) between the highest level of the fundamental signal and the highest level of any spurious signal—including aliases and harmonically related frequency components—in the spectrum.
SFDR is an important specification in an application where the frequency spectrum is being shared with other communication channels and applications. If a transmitter’s output sends spurious signals into other frequency bands, they can corrupt, or interrupt neighboring signals.
Applications:
DDS applications can be segmented into two primary categories:
- Communication and radar systems that require agile frequency sources for data encoding and modulation applications
- Measurement, industrial, and optical applications that require a generic frequency synthesis function with programmable tuning, sweeping, and excitation
In both cases, an increasing trend towards higher spectral purity (lower phase noise and higher spurious-free dynamic range) is coupled with low operating power and size requirements for remote or battery-operated equipment.
Find more information on DDS devices.
Tech Forum
Product Selection Guide (DDS)
Maximum speed writing to a Direct Digital Synthesis (DDS)
250 MHz single-tone signals using DDS evaluation boards AD9910/PCBZ
Video Library
IDT 8V97051 RF Synthesizer | Digi-Key Daily
Article Library
The Basics of Direct Digital Synthesizers (DDSs) and How to Select and Use Them
DDS
ProductTraining Modules
Direct Digital Synthesis Tutorial Series (1 of 7): Introduction
DDS
Product Highlights
DDS
Products Example:
| MFR PART # | AD9852ASVZ |
|---|---|
| DIGI-KEY PART # | AD9852ASVZ-ND |
| MANUFACTURER | Analog Devices Inc. |
| DESCRIPTION | IC DDS 300MHZ 12BIT 80TQFP |
| DATASHEET | Click Here |
| MFR PART # | AD9837ACPZ-RL7 |
|---|---|
| DIGI-KEY PART # | 505-AD9837ACPZ-RL7TR-ND |
| MANUFACTURER | Analog Devices Inc. |
| DESCRIPTION | IC DDS 5MHZ 10BIT 10LFCSP |
| DATASHEET | Click Here |
Applicable Part Numbers
| DigiKey Part Number | Manufacturer Part Number |
|---|---|
| 505-AD9837ACPZ-RL7TR-ND,505-AD9837ACPZ-RL7CT-ND,505-AD9837ACPZ-RL7DKR-ND | AD9837ACPZ-RL7 |
| AD9837ACPZ-RLTR-ND,AD9837ACPZ-RLCT-ND,AD9837ACPZ-RLDKR-ND | AD9837ACPZ-RL |
| 505-AD9837BCPZ-RL7TR-ND,505-AD9837BCPZ-RL7CT-ND,505-AD9837BCPZ-RL7DKR-ND | AD9837BCPZ-RL7 |
| 505-AD9838BCPZ-RL7TR-ND,505-AD9838BCPZ-RL7CT-ND,505-AD9838BCPZ-RL7DKR-ND | AD9838BCPZ-RL7 |
| AD9834BRUZ-REEL7TR-ND,AD9834BRUZ-REEL7CT-ND,AD9834BRUZ-REEL7DKR-ND | AD9834BRUZ-REEL7 |
| 505-AD5932YRUZ-ND | AD5932YRUZ |
| 505-AD9833BRMZ-ND | AD9833BRMZ |
| AD9833BRMZ-REELTR-ND,AD9833BRMZ-REELCT-ND,AD9833BRMZ-REELDKR-ND | AD9833BRMZ-REEL |
| 505-AD9833BRMZ-REEL7TR-ND,505-AD9833BRMZ-REEL7CT-ND,505-AD9833BRMZ-REEL7DKR-ND | AD9833BRMZ-REEL7 |
| 505-AD9834BRUZ-ND | AD9834BRUZ |
| 505-AD9834CRUZ-ND | AD9834CRUZ |
| 505-AD9834CRUZ-REEL7TR-ND,505-AD9834CRUZ-REEL7CT-ND,505-AD9834CRUZ-REEL7DKR-ND | AD9834CRUZ-REEL7 |
| AD9832BRUZ-REEL7TR-ND,AD9832BRUZ-REEL7CT-ND,AD9832BRUZ-REEL7DKR-ND | AD9832BRUZ-REEL7 |
| 505-AD9832BRUZ-ND | AD9832BRUZ |
| AD9835BRUZ-REEL7TR-ND,AD9835BRUZ-REEL7CT-ND,AD9835BRUZ-REEL7DKR-ND | AD9835BRUZ-REEL7 |
| 505-AD5933WYRSZ-REEL7TR-ND,505-AD5933WYRSZ-REEL7CT-ND,505-AD5933WYRSZ-REEL7DKR-ND | AD5933WYRSZ-REEL7 |
| 505-AD5933YRSZ-ND | AD5933YRSZ |
| AD5933YRSZ-REEL7TR-ND,AD5933YRSZ-REEL7CT-ND,AD5933YRSZ-REEL7DKR-ND | AD5933YRSZ-REEL7 |
| 505-AD9913BCPZ-ND | AD9913BCPZ |
| AD9850BRSZ-REELTR-ND,AD9850BRSZ-REELCT-ND,AD9850BRSZ-REELDKR-ND | AD9850BRSZ-REEL |
| 505-AD9850BRSZ-ND | AD9850BRSZ |
| AD9957BSVZ-REELTR-ND,AD9957BSVZ-REELCT-ND,AD9957BSVZ-REELDKR-ND | AD9957BSVZ-REEL |
| 505-AD9951YSVZ-ND | AD9951YSVZ |
| AD9851BRSZRLTR-ND,AD9851BRSZRLCT-ND,AD9851BRSZRLDKR-ND | AD9851BRSZRL |
| 505-AD9851BRSZ-ND | AD9851BRSZ |
| 505-AD9911BCPZ-ND | AD9911BCPZ |
| AD9953YSVZ-ND | AD9953YSVZ |
| AD9952YSVZ-REEL7TR-ND,AD9952YSVZ-REEL7CT-ND,AD9952YSVZ-REEL7DKR-ND | AD9952YSVZ-REEL7 |
| 505-AD9952YSVZ-ND | AD9952YSVZ |
| AD9954YSVZ-REEL7TR-ND,AD9954YSVZ-REEL7CT-ND,AD9954YSVZ-REEL7DKR-ND | AD9954YSVZ-REEL7 |
| 505-AD9956YCPZ-ND | AD9956YCPZ |
| 505-AD9954YSVZ-ND | AD9954YSVZ |
| AD9958BCPZ-REEL7TR-ND,AD9958BCPZ-REEL7CT-ND,AD9958BCPZ-REEL7DKR-ND | AD9958BCPZ-REEL7 |
| 505-AD9958BCPZ-ND | AD9958BCPZ |
| 505-AD9957BSVZ-ND | AD9957BSVZ |
| AD9851BRS-ND | AD9851BRS |
| 505-AD9854ASTZ-ND | AD9854ASTZ |
| AD9852ASVZ-ND | AD9852ASVZ |
| 505-AD9854ASVZ-ND | AD9854ASVZ |
| 505-AD9910BSVZ-REELTR-ND,505-AD9910BSVZ-REELCT-ND,505-AD9910BSVZ-REELDKR-ND | AD9910BSVZ-REEL |
| 505-AD9910BSVZ-ND | AD9910BSVZ |
| AD9959BCPZ-REEL7TR-ND,AD9959BCPZ-REEL7CT-ND,AD9959BCPZ-REEL7DKR-ND | AD9959BCPZ-REEL7 |
| 505-AD9959BCPZ-ND | AD9959BCPZ |
| 505-AD9912ABCPZ-REEL7TR-ND,505-AD9912ABCPZ-REEL7CT-ND,505-AD9912ABCPZ-REEL7DKR-ND | AD9912ABCPZ-REEL7 |
| 505-AD9912ABCPZ-ND | AD9912ABCPZ |
| 505-AD9858BSVZ-ND | AD9858BSVZ |
| AD9915BCPZ-ND | AD9915BCPZ |
| 505-AD9914BCPZ-REEL7TR-ND,505-AD9914BCPZ-REEL7CT-ND,505-AD9914BCPZ-REEL7DKR-ND | AD9914BCPZ-REEL7 |
| AD9914BCPZ-ND | AD9914BCPZ |
| AD9838ACPZ-RL7TR-ND,AD9838ACPZ-RL7CT-ND,AD9838ACPZ-RL7DKR-ND | AD9838ACPZ-RL7 |
| 505-AD5932YRUZ-REEL7TR-ND,505-AD5932YRUZ-REEL7CT-ND,505-AD5932YRUZ-REEL7DKR-ND | AD5932YRUZ-REEL7 |
| AD9831ASTZ-ND | AD9831ASTZ |
| 505-AD9833WBRMZ-REELTR-ND,505-AD9833WBRMZ-REELCT-ND,505-AD9833WBRMZ-REELDKR-ND | AD9833WBRMZ-REEL |
| 505-AD5930YRUZ-ND | AD5930YRUZ |
| AD9913BCPZ-REEL7TR-ND,AD9913BCPZ-REEL7CT-ND,AD9913BCPZ-REEL7DKR-ND | AD9913BCPZ-REEL7 |
| 505-AD9835BRUZ-ND | AD9835BRUZ |
| 505-AD5934YRSZ-ND | AD5934YRSZ |
| AD9850BRS-ND | AD9850BRS |
| AD5934YRSZ-REEL7TR-ND,AD5934YRSZ-REEL7CT-ND,AD5934YRSZ-REEL7DKR-ND | AD5934YRSZ-REEL7 |
| AD9859YSVZ-ND | AD9859YSVZ |
| 505-AD9830ASTZ-ND | AD9830ASTZ |
| 505-AD9833SRMZ-EP-RL7TR-ND,505-AD9833SRMZ-EP-RL7CT-ND,505-AD9833SRMZ-EP-RL7DKR-ND | AD9833SRMZ-EP-RL7 |
| 505-AD9852ASTZ-ND | AD9852ASTZ |
| AD9859YSVZ-REEL7TR-ND,AD9859YSVZ-REEL7CT-ND,AD9859YSVZ-REEL7DKR-ND | AD9859YSVZ-REEL7 |
| AD9915BCPZ-REEL7TR-ND,AD9915BCPZ-REEL7CT-ND,AD9915BCPZ-REEL7DKR-ND | AD9915BCPZ-REEL7 |
| AD5930YRUZ-REEL7TR-ND,2156-AD5930YRUZ-REEL7-ND | AD5930YRUZ-REEL7 |
| 505-AD9834BRUZ-REELTR-ND,505-AD9834BRUZ-REELCT-ND | AD9834BRUZ-REEL |
| 505-AD9832BRUZ-REELTR-ND,505-AD9832BRUZ-REELCT-ND | AD9832BRUZ-REEL |
| AD9830ASTZ-REELTR-ND,2156-AD9830ASTZ-REEL-ND | AD9830ASTZ-REEL |
| 2156-AD9954YSV-REEL7-ND | AD9954YSV-REEL7 |
| 505-AD9956YCPZ-REEL7TR-ND,505-AD9956YCPZ-REEL7CT-ND | AD9956YCPZ-REEL7 |
| 505-AD9914BCPZ-CSL-ND | AD9914BCPZ-CSL |
| AD9831ASTZ-REELTR-ND,2156-AD9831ASTZ-REEL-ND | AD9831ASTZ-REEL |
| 2156-TMC2340AH5C-ND | TMC2340AH5C |
| 2156-TMC2340AH5C1-ND | TMC2340AH5C1 |
| AD9837BCPZ-RL-ND | AD9837BCPZ-RL |
| AD9838ACPZ-RL-ND | AD9838ACPZ-RL |
| AD9838BCPZ-RL-ND | AD9838BCPZ-RL |
| AD9835BRUZ-REELTR-ND | AD9835BRUZ-REEL |
| AD9911BCPZ-REEL7TR-ND | AD9911BCPZ-REEL7 |
| AD9953YSVZ-REEL7TR-ND | AD9953YSVZ-REEL7 |
| 505-AD9914BCPZ-RL7-CSLTR-ND | AD9914BCPZ-RL7-CSL |
| AD9957/PCBZ-ND | AD9957/PCBZ |
| AD9959/PCBZ-ND | AD9959/PCBZ |
| AD9910/PCBZ-ND | AD9910/PCBZ |
| 505-AD9912A/PCBZ-ND | AD9912A/PCBZ |
| 505-AD9914/PCBZ-ND | AD9914/PCBZ |
| AD9915/PCBZ-ND | AD9915/PCBZ |
| 505-EVAL-AD9833SDZ-ND | EVAL-AD9833SDZ |
| 505-EVAL-CN0304-SDZ-ND | EVAL-CN0304-SDZ |
| 296-DRV8461EVM-ND | DRV8461EVM |
| AD9913/PCBZ-ND | AD9913/PCBZ |
| 505-AD9958/PCBZ-ND | AD9958/PCBZ |
| EVAL-AD9838SDZ-ND | EVAL-AD9838SDZ |
| 505-EVAL-AD9837SDZ-ND | EVAL-AD9837SDZ |
| EVAL-AD9832SDZ-ND | EVAL-AD9832SDZ |
| AD9911/PCBZ-ND | AD9911/PCBZ |
| AD9956/PCBZ-ND | AD9956/PCBZ |
| AD9956-VCO/PCBZ-ND | AD9956-VCO/PCBZ |
| AD9954/PCBZ-ND | AD9954/PCBZ |
| EVAL-AD5934EBZ-ND | EVAL-AD5934EBZ |
| EVAL-AD9835SDZ-ND | EVAL-AD9835SDZ |
| EVAL-AD9831EBZ-ND | EVAL-AD9831EBZ |
| EVAL-AD9834SDZ-ND | EVAL-AD9834SDZ |
| EVAL-AD9830EBZ-ND | EVAL-AD9830EBZ |
| EVAL-AD9835EBZ-ND | EVAL-AD9835EBZ |
| AD9859/PCBZ-ND | AD9859/PCBZ |
| ADZS-2189M-EZLITE-ND | ADZS-2189M-EZLITE |
| ISL5314EVAL2-ND | ISL5314EVAL2 |
| 1597-1158-ND | 109990080 |