DDS (Direct Digital Synthesis) Analog Devices AD9912 Arduino Shield by GRA & AFCH

Easy connection to Arduino MEGA 2560 without additional wires and converters

All functions of the DDS AD9912 are brought to the contacts of the Arduino MEGA

With this you can fully reveal all the capabilities of the DDS AD9912 Shield

Opensource Software available on our GitHub repository: https://github.com/afch/DDS-AD9912-Arduino-Shield

RF Signal Generator DDS AD9912 Arduino Shield

Listing includes:

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

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

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.

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

Short description

• Easy to connect OLED display
• One encoder for control via the program menu
• The synthesizer is capable to generate sine wave, CMOS and HSTL signals
• 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
• This Shield Board support overclocking of the AD9912 core up to 1.3 GHz (heatsink is recommended)
• DDS AD9912 Shield has ability to generate a signal of up to 600 MHz with a core overclocking up to 1.3 GHz (to suppress harmonics it is recommended to  overclock the AD9912 for frequencies above 400 MHz)

Key Benefits:

• Low harmonics no more than -60dBc. An output RF transformer is used for the correct operation of the current mirror
• The AD9912 built-in 50 Ohm resistors achieve better noise and harmonic results than the AD9910
• Small spurs
• 4 layer Board. Signal lines – TOP and Bottom, Inner layers – Ground and Power
• Low Noise LDO Stabilizers
• Separate power supply for all analog and digital lines (1.8V and 3.3V), 7 pcs IC voltage stabilizers are used. Additionally there is an RF Ferrite boad interchange
• High speed decoupling Level converter and TTL 5V matching
• Additional balancing transformer used for TCXO and EGEN options
• Standard Mode: up to 400 MHz sine wave output, 1 GSPS internal or external clock speed
• Overclocking Mode: up to 600 MHz sine wave output, up to 1.3 GSPS internal or external clock speed
• Differential HSTL Output up to 1 GHz
• CMOS Output to up to 200 MHz
• 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)

Specifications:

* when overclocking the core to 1.3 GHz

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 – 10 MHz 1 ppm external oscillator PLL at 1 GHz
3. EGEN – external generator up to 1 GHz (to connect an external clock source of up to 1.3 GHz, the source itself is NOT INCLUDED)

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). Therefore, when buying our DDS AD9912 Arduino Shield you can focus on the data from the datasheet on the AD9912.

Figure below shows measured by Anritsu MS2781B the noise level when using the built-in PLL in DDS. The PLL multiplies the frequency of a 40 MHz generator by 26 times

And another figure below (from Analog Devices AD9912 Datasheet Rev. F) shows the noise level when using an external reference clock 1 GHZ with the PLL OFF

Conclusion: when using external clocking 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 generator

OLED Display Menus:

DDS AD9912 Core Clock Menu

DDS AD9912 Sweep Menu

DDS AD9912 Main Screen

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

DDS AD9912 Arduino Shield Spectrograms:

GRA & AFCH DDS AD9912 Spectrograms:

GRA & AFCH DDS AD9912 Shield Oscillograms CMOS/HSTL:

DDS AD9912 Arduino Shield Thermal images:

AD9912 Board temperature measured with Flir E8 thermal imager at Core Clock @ 1040 MHz Powered from USB

Arduino MEGA to Shield AD9912 Pinout Scheme:

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