DDS (Direct Digital Synthesis) Analog Devices AD9910 Arduino Shield by GRA & AFCH

Easy connection to Arduino MEGA 2560 without additional wires and converters

All functions of the DDS AD9910 are brought to the contacts of the Arduino MEGA

With this you can fully reveal all the capabilities of the DDS AD9910 Shield

Opensource Software available on our GitHub repository: https://github.com/afch/DDS-AD9910-Arduino-Shield

Video review on our YouTube channel : https://youtu.be/_MUsmr0cAD4

Listing includes:

• AD9910 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 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]

Key Benefits:

• Low harmonics no more than -60dBc. 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 at 1 GHz.
2. TCXO – 10 MHz 1 ppm external oscillator PLL at 1 GHz.
3. EGEN – external generator up to 1.5 GHz. (To connect an external clock source of up to 1.5 GHz, this source is NOT INCLUDED).
4. OCXO – Oven Controlled Crystal Oscillators deliver the ultimate piezo electric performance with stabilities down to less than ±1 ppm.

Additionally balancing transformer is used for TCXO, EGEN and OCXO options:

• Easy to connect OLED display.
• Control buttons for control via the program menu.
• The synthesizer is capable to generate sine wave, AM or FM modulated signal.
• 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 AD9910 core to 1.5 GHz (heatsink is recommended).
• DDS AD9910 Shield has ability to generate a signal up to 600 MHz with a core overclocking up to 1.5 GHz (to suppress harmonics, it is recommended to  overclock the AD9910 for frequencies above 400 MHz).
• Has ability to increase output power by +4 dBm when “DAC Current HI” is activated.

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 AD9910, when designing our DDS AD9910 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 AD9910 Arduino Shield, You can focus on the data from the datasheet on the AD9910.

Figure 16 shows the noise level when using the built-in PLL in DDS. The PLL multiplies the frequency of a 50 MHz generator by 20 times. We use a similar frequency – 40 MHz (x25 Multiplier) or 50 MHz (x20 Multiplier) from TCXO which gives even more stability.

And figure 15 shows the noise level when using an external reference clock 1 GHZ, with the PLL off.

Comparing these two plots, for example, for Fout = 201.1 MHz and the internal PLL turned on at 10 kHz carrier offset, the phase noise level is -130 dBc @ 10 kHz. And with the PLL off and using external clocking, the phase noise is 145 dBc @ 10kHz. That is, when using an external clock phase noise by 15 dBc better (lower).

For the same frequency Fout = 201.1 MHz, and the internal PLL turned on at 1 MHz carrier offset, the phase noise level is -124 dBc @ 1 MHz. And with the PLL off and using external clocking, the phase noise is 158 dBc @ 1 MHz. That is, when using an external clock phase noise by 34 dBc 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:

DDS AD9910 Core Clock Menu

DDS AD9910 Core Clock Menu

DDS AD9910 AM Modulation Menu

DDS AD9910 FM Modulation Menu

Specifications:

* When overclocking the core to 1.5 GHz
** When the “DAC Current HI” function is activated

DDS AD9910 Arduino Shield Spectrograms:

GRA & AFCH DDS AD9910 Shield VS DDS Board from China Spectrograms Comparison:

GRA & AFCH DDS AD9910 Shield Spectrograms:

DDS AD9910 Arduino Shield Thermal images:

AD9910 Board temperature measured with Flir E8 thermal imager at Core Clock @ 1000 MHz

AD9910 Board temperature measured with Flir E8 thermal imager at Core Clock @ 1440 MHz

Arduino MEGA to Shield AD9910 Pinout Scheme:

DDS Arduino Shield AD9910 RF Signal Generator Overview:

DDS Arduino Shield AD9910 RF Signal Generator: