Wide Coverage, Low Spurious Frequency Synthesizer Developed

Frequency synthesizer is a core component of the radar system, the phase noise and spur levels have a direct impact on the excellent performance of radar systems. With the rapid development of electronic technology and defense technology, changes happened in the modern war form, especially the "information war" appeared, frequency synthesizer technology have become increasingly demanding targets,often require a wide coverage, low phase noise , low spur levels, small step, frequency-agile, high stability and other characteristics of the spectrum.In the radar system, how to generate high spectral purity and stability of the local oscillator has been a technology difficult point, but also requires the system miniaturization.This paper describes the main specifications, phase-locked loop structure, working principle and its various components have a impact on the phase nosie of the final output signal.Common frequency synthesizer scheme is based on the output frequency band, frequency step, spectrum purity, frequency resolution, frequency stability design.This paper detailed analysis of the current mainstream technology, the basic principle of frequency synthesis, advantages and disadvantages and their application occasions, and analyzes the DDS phase noise and spurious targets. Secondly, this article summarized based on previous comparative advantages and disadvantages of the various frequency synthesizer scheme, combined with the specific technical requirements of this project realize a frequency synthesizer with a phase-locked loop frequency multiplier.in theory, this paper calculate the phase noise and spur levels of the final output signal, they can reach an agreement on the provision of technical indicators.This paper has analyzed the technology which the actual hardware realizes key and the difficulty,and has given the corresponding solution, by setting a reasonable loop bandwidth, in conjunction with software control module regulating non-linear PLL chip charge pump current compensation in order to achieve a constant loop bandwidth.In a wide frequency coverage,it's a good solution to solve phase noise and spur levels compatibility.Actual test results show that: the final output signal in the 3 ~ 4GHz phase noise is better than the average -9 3d Bc / Hz @10kHz, in the 6 ~ 11GHz phase noise is better than the average -8 5d Bc / Hz @10kHz, in the 14 ~ 16GHz phase noise is better than the average - 83d Bc / Hz @10kHz, Full-band spurious level is better than -60dB.The output power is better than 10dBm, the provisions of the agreement to meet the requirements of technical indicators. For this project, the emergence of some phenomena and problems were analyzed, and gives the appropriate solution, summed up the shortcomings of this project and make recommendations for improvement, right after the wide coverage of a similar low spurious frequency synthesizer designed to have a certain reference and guiding significance.