A technique for dynamic range improvement of intermodulation distortion products for an Interpolating DAC-based Arbitrary Waveform Generator using a phase switching algorithm

Abstract

This paper describes a phase switching algorithm for Interpolating Digital-to-Analog Converter (DAC) based Arbitrary Waveform Generators (AWG). This was possible by using the standard phase switching algorithm with the addition of simple phase offset and systematic phase difference adjustment; this was discovered by experimenting with suppression of the intermodulation distortion (IMD) components of a two-tone signal. In this case, we examine the 3rd, 5th and 7th order IMD tones and the effect of the phase switching algorithm and phase shift has on the AWG by measurement with a digitizer. Then we show what the effect of the developed two-tone phase switching technique has upon the performance measurement of a 16-bit Analog-to-Digital Converter (ADC). It is shown that using the original algorithm, no improvement could be achieved for the odd order IMD products. However, by using an even order suppression technique (another phase difference) with a phase shift, a suppression was achieved compared to the standard two-tone signal generation (without phase switching). We show how this technique allows the use of a low-cost tester resource to test IMD products with a higher dynamic range than was previously possible.