0 to 20 MHz DDS Function Generator [130264-I]
The heart of this project is AD9834 – Direct Digital Synthesizer chip, which is capable to generate sine and triangular wave upto 37.5MHz. The inbuilt comparator in the DDS chip can be used to generate square wave signal from the sine wave. The chip is controlled by a PIC microcontroller using a serial communication interfa
The heart of this project is AD9834 – Direct Digital Synthesizer chip, which is capable to generate sine and triangular wave upto 37.5MHz. The inbuilt comparator in the DDS chip can be used to generate square wave signal from the sine wave. The chip is controlled by a PIC microcontroller using a serial communication interface (SPI). A programmable gain amplifier (LMH6505), where gain is set by a control voltage from a digital potential divider and a buffer amplifier, amplify the output of DDS to a required level. A DC shift of output signal is also possible.
The PIC microcontroller provides the necessary user interface with LCD display, and keypad. Using this one can set frequency, output level, dc offset etc. easily.
Discussie (4 opmerking(en))
spo256al2 11 jaar geleden
Hi,
You could use the triangular function and comparator to produce a duty cycle. I am interresting by this.
Your seven pole filter is a 50ohm imedance. On AD9834 data sheet seems that best impedance is for 200ohm for best noise amplitude compromise.What do you think about symetrical 30MHz filter.
ras 11 jaar geleden
TonGiesberts 11 jaar geleden
Can you attach all schematics (with values), if available the PCB(s) and the source code of the firmware. We would also like a detailed BOM (distributor order codes, manufacturer references and footprints). A photograph of your prototype would be nice.
efrs 11 jaar geleden
I'm working now with a similar chip an AD9833, looks very similar, but lower frequency (about 10MHz max).
I use an AD9833 module obtained in ebay. A PIC18F45K22 as the controller, (it's cheap and I have some in my junkbox ). It's easy to control the AD9833 (see AN1070 -programming AD9833 and AD9834- from Analog Devices ).
I've not tried a keyboard input (future improvements). If a PC control would be needed i will use a PIC18F46j50 instead(it has direct USB).
My problem is obtaining some sort of 'continous tuning' now I'm working with a 10 turn pot as the tuning device and a single turn pot as fine tuning, still not very satisfied with the result.
Any ideas...
CBec 11 jaar geleden
It would be great to extend the functionality of this generator so it could perform as a network analyser instrument from a few Hz to 20MHz