DDS (Direct Digital Synthesis) Analog Devices AD9912 Arduino Shield by GRA & AFCH
This device is designed to ensure seamless integration with Arduino MEGA 2560
It does not require any extra wires or converters to work properly
For maximum performance we recommend Ultra-low noise reference oscillator RCLN1000
All AD9912 pins are connected to the Arduino MEGA pins
With this you can fully reveal all the capabilities of the DDS AD9912 Shield
PCB Design Schematics Case and Software made by GRA & AFCH

Opensource Software available on our GitHub repository: https://github.com/afch/DDS-AD9912-Arduino-Shield
DDS AD9912 Firmware compilation and uploading to Arduino Mega Tutorial: youtu.be/Zn1xLlvlVXE
Video review of DDS AD9912 Shield on our YouTube channel: youtu.be/_MUsmr0cAD4

Listing includes:

• AD9912 DDS Shield Board (assembled)
• OLED Display (optional, choose in selector)
• Arduino MEGA 2560 Control Board (optional, choose in selector)
• Clock Chip (optional, choose in selector)

Types of possible reference oscillators (choose one of them in the selector):

1. XO – Crystal 25 MHz 20 ppm internal oscillator with PLL at 1 GHz
2. TCXO – 50 MHz 1 ppm oscillator PLL x 20 at 1 GHz
3. REF CLK IN – external generator up to 1 GHz
   (to connect an external clock source of up to 1.3 GHz, the source itself is NOT INCLUDED)

Applications:

• Oscillator Ultra Low jitter Fout=50MHz -160dBc @ 10khz, Fout=400MHz -138dBc @ 10khz (external reference clock)
• Local oscillator (LO) for HAM Radio
• Receiver/Transmitter communications
• Agile local oscillator (LO) frequency synthesis
• For teaching students at Universities and Institutes
• Secure communications
• Test and measurement equipment

Functional features:

• Support of OLED display (selectable in options)
• One encoder for controlling all functions through a graphical menu
• The synthesizer is capable to generate Sine Wave, CMOS and HSTL signals
• Differential HSTL Output up to 1 GHz
• CMOS Output to up to 200 MHz
• The software allows you to select and configure the frequency of the clock generator through the user menu
  (without the need to recompile the program)
• Any settings can be stored in non-volatile EEPROM memory (located at Arduino Mega)
• Basic settings are applied and saved automatically
• Expanded and convenient DDS Clock source menu
• This Shield Board support overclocking of the AD9912 core up to 1.3 GHz (heatsink is recommended)
• The DDS AD9912 Shield has the capability to generate a signal with a frequency of up to 600 MHz,
  with a core overclocking potential of up to 1.3 GHz (when the output frequency exceeds 400 MHz,
  it is recommended to overclock the DDS core for harmonic suppression)
• Standard Mode: up to 400 MHz sine wave output, 1 GSPS (1.0 GHz) internal or external clock speed
• Overclocking Mode: up to 600 MHz sine wave output, up to 1.3 GSPS (1.3 GHz) internal or external clock speed
• Output Filter LPF 9-order
• Spur Killer* 2 channels to suppress spurs in the frequency spectrum* (not yet implemented)
• Integrated 14 bit DAC 48 bit frequency tuning word with 4 μHz resolution 0.000004Hz (optional)

Electrical performance:

• Ensured low harmonic level with levels not exceeding -70dBc,
  this is due to the use of an output RF transformer for optimal current mirror operation
• Low Noise LDO Stabilizers with separate power supply for all analog and digital lines (1.8V and 3.3V),
  they utilizes 7 IC voltage stabilizers; additionally there is an RF Ferrite bead interchange
• Additional balancing transformer used for TCXO and REF CLK IN options
• 4 layered PCB with signal lines on Top and Bottom and inner layers Ground and Power
• High-speed decoupling Level converter and TTL 5V matching
• The built-in 50-ohm resistors in the AD9912 chip provide better noise and harmonic performance compared to the AD9910
• Remote control of the DDS Generator through a USB connection and PC using the terminal serial port

Specifications:

* when overclocking the core to 1.3 GHz

Phase Noise:

This parameter is very important and interesting for those who buy and want to use DDS Shield Board.
Since the internal phase noise of DDS is obviously less than that of PLL generators, the final value are highly dependent on the clock source.
In order to achieve the values stated in the datasheet on AD9912, when designing our DDS AD9912 Arduino Shield, we strictly adhered to all recommendations from Analog Devices:

PCB layout in 4 layers, 8 low noise voltage regulators for all power lines (3.3 V digital, 3.3 V analog, 1.8 V digital, and 1.8 V analog and etc.).
We measured the phase noise of our DDS AD9912 with the Anritsu MS2781B and found that the phase noise is below the instrument’s measurement capability
(shown as a red line on the graph).

Figure below shows the phase noise level when using the built-in PLL in DDS. The PLL multiplies the frequency of the on-board 50 MHz TCXO generator by a factor of 20.
The output frequency is 100 MHz.

Figure below shows the phase noise level of DDS9912 when using an external reference clock frequency of 1 GHz (RCLN1000), with the PLL OFF.
The output frequency of the DDS is 100 MHz.

Let’s compare these two graphs, for example, at a 10 kHz offset from the carrier:
with the internal PLL system engaged, the phase noise level is -133 dBc/Hz, while with the PLL system disengaged and using external clocking, the phase noise is -143 dBc/Hz.
This means that using an external clock signal results in a phase noise that is 10 dBc/Hz better (lower).

For the same output frequency, but at a 1 MHz offset from the carrier, with the internal PLL system engaged,
the phase noise level is -130 dBc/Hz, while with the PLL system disengaged and using external clocking, the phase noise is -146 dBc/Hz.
This means that using external clocking results in phase noise that is 16 dBc/Hz better (lower).

Conclusion:
When using external clock, you can get much lower phase noise than using the built-in PLL.
But do not forget that in order to achieve such results, increased requirements are put forward to the external oscillator.
For maximum performance we recommend our Ultra-low noise reference oscillator 1GHz RCLN1000.

Ultra Low Noise Reference Oscillator for AD9910 Shield:

1GHz Ultra Low Noise Reference Oscillator -130dBc/Hz @ 10kHz RCLN1000 for DDS AD9910 DDS9912 Units

If you need higher power output:

The simplest method to increase the power is connecting an external RF signal Amplifier, such as the MMIC MRFA89.
It allows obtaining a DDS signal output power of up to +20 dBm.

IMPORTANT: Since the MMIC MRFA89 Amplifier has maximum output power of +20 dBm and gain of 20 dB, the recommended maximum input signal level is 0 dBm.

NOTE: as most amplifiers generate harmonics, it is advised to connect an LPF Filter to the Amplifier output for harmonic suppression.
For example, one from the LPF 7th Order Elliptical series that we offer.

We recommend RF Amplifier and Low-Pass Filter for AD9912 DDS Shield:

RF Amplifier 8-2000 MHz, GAIN = 20 dB, P = +20 dBm MMIC MRFA89 SOT-89 [GOLD PLATED]

Low-Pass Filter LPF 7th Order Elliptical 1-1000Mhz 3.5, 7, 14, 28, 144, 433MHz etc for RF Amlifier, Receiver, Transmitter, Mixer, Transceiver, Antenna.

OLED Display Menus:

Remote control of DDS Generator through USB connection from PC using the terminal serial port:

List of Serial Port Commands:

Starting with version 1.02, the ability to control via the serial port has been added.

F – Set Frequency in Hz (100000 – 500000000)
H – Set HSTL Output: 0 – OFF, 1 – ON, 2 – Doubler ON
C – Set CMOS Output: 0 – OFF, 1 – ON
D – Set CMOS Divider (1 – 65353)
P – Set Output Power in dBm (-7 – +4)
M – Get Model
E – Enable Outputs (ALL)
S – Shut down Outputs (ALL)
V – Get Firmware Version
h – Help
; – Commands Separator

Example:
F100000;P-2
Set Frequency to 100 kHz, and Output Power to -2 dBm.
Any number of commands in any order is allowed.

Serial Port Settings:

Speed – 115200 Bouds
Data Bits – 8
Stop Bits – 1
Parity – No
DTR – OFF

Windows:

An example of setting up a serial port in the Windows console:

mode COM3 baud=115200 DTR=OFF Data=8

Usage example:
echo F100000000 > COM3

Ubuntu 22.04:

An example of setting up a serial port in the Ubuntu:

sudo usermod -aG dialout $USER_NAME$
sudo chmod a+rw /dev/ttyUSB0
sudo stty -F /dev/ttyUSB0 115200 cs8 ixoff -hupcl -echo

Usage example:
echo “F100000000” > /dev/ttyUSB0

example of command prompt with serial commands for AD9910 DDS RF Unit

DDS AD9912 Arduino Shield Spectrograms:

GRA & AFCH DDS AD9912 Spectrograms:

GRA & AFCH DDS AD9912 Shield Oscillograms CMOS/HSTL:

DDS AD9912 Arduino Shield Thermal images:

DDS AD9912 Shield Board Connection Diagram:

DDS Arduino Shield AD9912 RF Signal Generator by GRA & AFCH:

Operating Instruction