DDS (Direct Digital Synthesis) Analog Devices AD9959 Arduino Shield by GRA & AFCH

Easy connection to Arduino MEGA 2560 without additional wires and converters

All functions of the DDS AD9959 are brought to the contacts of the Arduino MEGA

With this you can fully reveal all the capabilities of the DDS AD9959 Shield

Opensource Software available on our GitHub repository: https://github.com/afch/DDS-AD9959-Arduino-Shield

Video review on our YouTube channel : https://www.youtube.com/watch?v=HpigQwjc9mg&feature=youtu.be

Download page for the DDS AD9959: https://gra-afch.com/Downloads/RF Units/DDS AD9959 v1.1

Listing includes:

• RF AD DDS Unit [AD9959 Shield Board]
• Display [OLED] (optional, choose in selector)
• Clock Source (XO, TCXO, EGEN) (optional, choose in selector)
• Arduino Control Board [MEGA 2560] (optional, choose in selector)
• Power Supply [DC 7.5V/2A] [US, EU, UK] [AC plug] (optional, choose in selector)
• Operating Manual

We recommend RF Amplifier and Low-Pass Filter for AD9910 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

Key Benefits:

• Convenient and fast control with an encoder.
• 4 synchronized DDS channels 225MHz @ up to 600 MSPS
• Low harmonics no more than -60 dBc. An output RF transformer is used for the correct operation of the current mirror.
• 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), 5 pcs IC voltage stabilizers are used. Additionally, there is an RF Ferrite bead interchange.
• High-speed decoupling Level converter and TTL 5V matching.

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

1. XO – Crystal 25 MHz 20 ppm internal oscillator with PLL up to 600 MHz.
2. TCXO – 40MHz (Supports 10 – 50 MHz) 1 ppm external oscillator PLL up to 600 MHz.
3. REF CLK IN – external reference clock input, up to 600 MHz. (this source is NOT INCLUDED).

Features:

• At the output of each channel is a transformer to reduce even harmonics.
• Additionally balancing transformer is used for XO, TCXO and REF CLK IN options.
• Easy to connect OLED display.
• Device control with one encoder and one button.
• The synthesizer is capable to generate sine wave.
• 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 support overclocking the AD9959 core up to 600 MHz.
• DDS AD9959 Shield has ability to generate a signal up to 225 MHz with a core overclocking up to 600 MHz (to suppress harmonics, it is recommended to  overclock the AD9959 for frequencies above 200 MHz).

Phase Noise

This parameter is very important and interesting for those who buy DDS.
Since the intrinsic phase noise of DDS is obviously less than that of PLL generators, the final value is highly dependent on the clock source. In order to achieve the values stated in the datasheet on AD9959, when designing our DDS AD9959 Arduino Shield, we strictly adhered to all recommendations from Analog Devices: PCB layout in 4 layers, separate power supply of all 4 power lines (3.3 V digital, 3.3 V analog, 1.8 V digital, and 1.8 V analog).

Figure below shows the phase noise level of DDS9959 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 10. The output frequency is 100 MHz.

Figure below shows the phase noise level when using an external reference clock frequency of 500 MHz, 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 -113 dBc/Hz, while with the PLL system disengaged and using external clocking, the phase noise is -132 dBc/Hz. This means that using an external clock signal results in a phase noise that is 11 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 -107 dBc, while with the PLL system disengaged and using external clocking, the phase noise is -144 dBc/Hz. This means that using external clocking results in phase noise that is 37 dBc/Hz better (lower).

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:

Specifications:

Serial Port Commands:

List of Serial Port Commands:

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

C — Set the current output Channel: (0 — 3)
F — Sets Frequency in Hz (100000 — 225000000)
A — Sets the power (Amplitude) level of the selected channel in dBm (-60 — -7)
P — Sets the Phase of the selected channel in dBm (0 — 360)
M — Gets Model
E — Enable Outputs (ALL)
D — Disable Outputs (ALL)
V — Gets Firmware Version
h — This Help
; — Commands Separator

Example:
C0;F100000;A-10
Sets the Frequency to 100 kHz, and Output Power (Amplitude) to -10 dBm on Channel 0 (RF OUT0).
Any number of commands in any order is allowed, but the very first command must be “C”

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

DDS AD9959 Arduino Shield Spectrograms:

GRA & AFCH DDS AD9959 Shield External Clock Source VS Internal Clock Source Comparison:

GRA & AFCH DDS AD9959 Shield Oscillogram:

Arduino MEGA to Shield AD9959 Pinout Scheme:

DDS Arduino Shield AD9959 RF Signal Generator Overview:

DDS Arduino Shield AD9959 RF Signal Generator:

Operating Manual

Connection Diagram