DDS (Direct Digital Synthesis) Analog Devices AD9914 Arduino Shield by GRA & AFCH

Easy connection to Arduino MEGA 2560 without additional wires and converters

All functions of the DDS AD9914 are brought to the contacts of the Arduino MEGA

With this you can fully reveal all the capabilities of the DDS AD9914 Shield

Opensource Software available on our GitHub repository: https://github.com/afch/DDS-AD9914-Arduino-Shield

Listing includes:

• RF AD DDS Unit [AD9914 Shield Board]
• Display [OLED] (0,94″ or 1,54″) (optional, choose in selector)
• Clock Source (TCXO, EGEN) (optional, choose in selector)
• Arduino Control Board [MEGA 2560] (optional, choose in selector)
• Power Supply [DC 12V/1A] [US, EU, UK, AU] [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 [GOLD PLATED]

AD9914 and AD9915 differences:

Key Benefits:

• Convenient and fast control with an encoder.
• Core overclocking up to 4 GHz (external reference clocking).
• Low harmonics.
• 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.
• Temperature sensor.
• Active fan cooling (due to the high heat dissipation of the AD9914, we had to install a fan).

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

1. TCXO – 50MHz (Supports 5 – 125 MHz) 1 ppm external oscillator PLL up to 2600 MHz. (Support OCXO via SMA REF CLK IN)
2. REF CLK IN – external reference clock input, up to 4000 MHz (this source is NOT INCLUDED).

Features:

• At the output is a transformer installed to reduce even harmonics.
• Additionally balancing transformer is used for TCXO and REF CLK IN options.
• Easy to connect OLED display.
• Device control only with one encoder.
• 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 core overclocking the AD9914 core up to 4000 MHz.
• DDS AD9914 Shield has ability to generate a signal up to 1700 MHz with a core overclocking up to 4000 MHz (for frequencies above 1400 MHz output filter needs replacement).

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 AD9914, when designing our DDS AD9914 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). Therefore, when buying our DDS AD9914 Arduino Shield, You can focus on the data from the datasheet on the AD9914.

Figure 19 shows the noise level when using the built-in PLL in DDS:

And figure 19 shows the noise level when using an external reference clock 3500 MHZ, with the PLL off:

We realize that direct comparison of these graphs is incorrect, but nevertheless, on average, when offset from the carrier frequency by 10 kHz and using an external generator, the noise level is 20 dB less than when 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.

F – Set Frequency in Hz (100000 – CoreFrequency/2)
P – Set Output Power in dBm (-68 – 0)
M – Get Model
E – Enable Output
D – Disable Output
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

DDS AD9914 Arduino Shield Spectrograms:

DDS AD9914 100 MHz, TCXO 40 MHz x66 @ 2640 MHZ

In this graph you can see the fundamental frequency of 1.0 GHz and its mirror harmonic at 1.64 GHz, so clocking occurs at a frequency of 2.64 GHz (2.64 – 1.0 = 1.64). By default, our board has an output LC low-pass filter with a cutoff frequency of 1.5 GHz, so it cannot completely suppress the mirror harmonic at a frequency of 1.64 GHz, and besides, it attenuates the level of the fundamental frequency at a frequency of 1 GHz by 4 dB. (On request, a ceramic filter with a different cutoff frequency and with lower losses can be installed)

DDS Arduino Shield AD9914 RF Signal Generator:

Operating Manual