Posted on 04 Aug 2008
The heart of the synthesizer is a set of 2 Analog Devices AD9850 direct digital synthesis (DDS) chips. These provide 2 channels of sinewave output which may differ in frequency and relative phase. The output stage of the synthesizer also includes separate variable attenuators for the 2 channels. These attenuators have a range of 0.0 - 63.9 dB of attenuation, in 0.1 dB steps. The user therefore has control over five parameters: 2 output frequencies, 2 output attenuations, and relative phase between the 2 channels.[more]
Posted on 01 Aug 2008
Here is an extremely simple and low cost Sine/Square wave generator based on the Analog Devices AD9835 Direct Digital Synthesis (DDS) Generator chip. The frequency can be set for any frequency from 1Hz to 10MHz in 1Hz resolution steps! All this with three push buttons and a novel “sliding window” LED display. The controller chip is a Microchip PIC16F628. [more]
Posted on 01 Aug 2008
The aim was to produce a DDS controller with minimum hardware, that would offer a good linear tuning rate at 10Hz steps.The project uses an AD 9850BRS from analog devices, an industry standard two line LCD display, two PIC16F84 processors to manage the DDS and display, an optical shaft encoder and a pair of MMIC amplifiers to generate up to +10dBm to drive a diode ring mixer.[more]
Posted on 01 Aug 2008
Here’s a wonderfully-simple project first done by Curtis Preuss, WB2V in the July ‘97 issue of QEX. The article was entitled “Building a Direct Digital Synthesis VFO” and was geared as a straightforward starting point for building and evaluating a DDS VFO based on the Analog Devices AD9850 chip.Curtis used the PIC1654 microcontroller but this project ported the PIC16C54 software to work on the PIC16C84 .[more]
Posted on 29 Jul 2008
This is a simple signal generator which produces sine waves (or any waveform really) at audio frequencies using DDS and is controlled a USB serial connection.Only 2 chips are used in this circuit. The AVR ATmega88 which produces the signal, and an FT232R for the USB interface. While a computer is required to control the varying frequency of the oscillator, a fixed frequency project could be made without the USB interface.[more]
