Broadband low-phase noise frequency synthesizer without frequency divider based on harmonic mixing

Abstract

The invention relates to a broadband low-phase noise frequency synthesizer without a frequency divider based on harmonic mixing. The frequency synthesizer comprises a harmonic extraction module, a phase-locked loop, a direct frequency digital synthesizer and a reference source. The harmonic extraction module is used for extracting multiple-harmonic components of the reference source; appropriate components are elected and provided for an interpolation mixer; meanwhile, a reference clock of the direct frequency digital synthesizer is provided. The phase-locked loop is used for locking output signals and reference signals of a voltage-controlled oscillator. A feedback loop of the phase-locked loop comprises a frequency mixer which is used for guaranteeing broadband frequency outputting. By adopting the broadband low-phase noise frequency synthesizer without the frequency divider based on harmonic mixing, the broadband output frequency range of over one octave can be realized; the frequency divider is thoroughly omitted in the feedback loop, so that phase noise is reduced greatly; the frequency synthesizer supports wide bands and can be applied to a signal source, a frequency spectrograph and other high-performance measuring instruments, thereby having a wider application range.

Description

technical field [0001] The present invention relates to the field of frequency synthesis, in particular to the field of frequency synthesis of broadband low phase noise, in particular to a harmonic frequency mixing-based broadband low phase noise frequency synthesizer. Background technique [0002] A frequency synthesizer is one of the core components of an RF microwave system. It performs operations such as addition, subtraction, multiplication, and division on several reference frequency components, and synthesizes and outputs other frequencies. Frequency synthesis technology originated in the 1930s and has been widely used in mobile communications, satellite navigation, instrumentation, digital television and other fields. [0003] According to the realization principle, frequency synthesis technology can be roughly divided into: direct frequency synthesis technology (DS), direct digital frequency synthesis technology (DDS), indirect frequency synthesis technology, and hy...

AI Technical Summary

Problems solved by technology

However, the newly added PLL introduces new phase noise, which limits the overall phase noise index and increases the difficulty of design

The setting of the frequency division ratio N in the feedback loop of the main loop will inevitably lead to the deterioration of the phase noise of 20lgN

The biggest problem with this solution is the contradiction between broadband characteristics and low phase noise characteristics. If you want to maintain broadband characteristics, either the output range of PLL2 is wide but the phase noise is poor, or the output range of PLL2 is narrow but N is still relatively large in some frequency bands. Big

In short, the improvement of phase noise by this scheme is incomplete

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