High order sigma delta noise shaping direct digital frequency synthesizer

Abstract

A high stage Sigma Delta noise shaping direct digital frequency synthesizer includes a phase accumulator, a high stage Sigma Delta noise shaping interpolator, a sine or a cosine inquiry list, a D / A converter and a low-pass filter, among which, the interpolator includes a shaping accumulator and a delay circuit, outside N bit frequency digits are input into a phase accumulator and the output of which is connected with the shaping accumulator, the output of which is divided into a high p bit as the sine or cosine phase value and an intercepted low N-p bit and its output is connected with the delay circuit, the operation output of which is returned to the shaping accumulator, the output of the shaped phased value is output to the enquiry list, the output of which is connected with the input of the D / A converter, finally the output of which is connected to the input of the filter.

Description

technical field [0001] The invention relates to a high-order ΣΔ noise shaping direct digital frequency synthesizer for improving the dynamic characteristics of output signals. Background technique [0002] Direct digital frequency synthesizer (DDFS) is an important low-cost high-resolution frequency synthesis method. Unlike PLL-based synthesizers, DDFS is fully compatible with digital CMOS processes and is often embedded in baseband ASIC transceivers. Although DDFS has been around for many years, it can only be applied to narrow-band frequency synthesis due to the performance limitations of digital logic circuits and digital-to-analog converters. Recently, with the improvement of digital logic circuit and digital-to-analog converter technology, DDFS has become the mainstream of broadband frequency synthesis. Such as figure 1 As shown, a conventional DDFS includes a phase accumulator 20 that generates a phase value based on an input frequency word 10 . DDFS converts phase...

AI Technical Summary

Problems solved by technology

The most straightforward solution is to increase the length of the phase word, but this will result in a drastic increase in synthesizer hardware

And along with the increase of phase words, the number of bits of phase accumulator 20 also increases thereupon, will affect the speed of phase accumulator 20 accumulation like this

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