PHASE COHERENCY

HSM Series & HS9000 Series RF Synthesizers

Holzworth's proprietary non-PLL based RF synthesis architectures offer many unique performance advantages over more traditional PLL based synthesizer designs. One of the many important performance advantages is known as Phase Coherency, which is directly related to the incredible, relative channel-to-channel phase/frequency stability that the Holzworth synthesizers provide in a multi-channel configuration.


"Phase Coherency" is a term that is commonly used to define how direct analog synthesizers operate. Due to the nature of the direct analog architecture, the term has also been adopted to define a synthesizer's ability to maintain the phase of a frequency after a frequency change so that upon returning to said frequency, its original phase trajectory is unaltered. This is very useful for radar frequency hopping and is more universally referred to as "phase memory". Phase coherency in synthesizers defines a precise phase relationship between multiple frequency sources while being clocked by the same reference signal. This absolutely holds true for direct analog designs as all frequencies are ever present and precisely related to the reference clock. The direct analog system simply switches/routes the desired frequency to the RF output port. The phase coherent definition also holds true for Holzworth's ultra stable, non-PLL designs when multiple synthesizers are clocked by one reference signal.

Holzworth non-PLL Design Overview

Holzworth synthesizers are designed with a digital front end and a proprietary, direct analog back end. The proprietary architecture maintains low spurious response while also providing industry leading phase noise performance, exhibiting signal jitter performance of far less than 100fs.


The PLL was originally excluded from the Holzworth designs for optimal signal stability and fast switching speeds. Unlike PLL designs, there is no post switch settling time to reach the new frequency. PLL based designs exhibit switching speeds similar to the Holzworth designs, but also include a post switch frequency variance that is often as great as ±100kHz. This should be specified as settling time. Holzworth synthesizers exhibit little or no settling time under most switching scenarios.


The phase coherent nature of the non-PLL synthesizer creates very precise frequency relationships between multiple channels. The integer related outputs demonstrate a relative channel-channel phase drift of less than ±0.5ps over a one hour time frame. While operating in a controlled environment (±1C) to minimize thermal effects, the design can maintain this sub-picosecond channel-to-channel phase drift indefinitely.

   
... HSM SERIES: .. Single Channel Synthesizer Modules.

 

 
   
.... HS9000 SERIES: .. Multi-Channel RF Synthesizers

 

 
   

WHITE PAPER: ..Coherent Multi-Channel RF Synthesis

There are many paths to accomplishing a broadband RF synthesis architecture. Depending on the application, there are trade offs to be considered. This white paper compares the advantages and disadvantages among three common architectures: DDS/Direct Analog, PLL-based, and Analog.

 
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PRODUCT SPOTLIGHT: ..Ultra Low Phase Noise, Phase Coherent Synthesizers

Microwave Journal reports on Holzworth's unique multi-channel synthesizer architecture in August's Military Microwave Supplement. This product feature outlines the advantages of Holzworth's proprietary architecture which allows for the highest channel density of independently tunable synthesizers. Phase coherency and channel-to-channel phase drift are notable key advantages in addition to the performance for which Holzworth synthesizers are known. The article can be downloaded here or viewed at Microwave Journal online.

 
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WHITE PAPER: ..Phase Coherent Multi-Channel RF Synthesis

This white paper was written for Microwave Journal to explain the key advantages to using a multiplied synthesis architecture instead of a phase locked loop architecture. The white paper is available here or can be downloaded directly from Microwave Journal.

 
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PRESS RELEASE: ..

Holzworth Instrumentation releases Phase Coherent, Multi-Ch RF Synthesizers

Holzworth’s ultra low phase noise synthesizers are unique in that they do not utilize PLL based architectures to achieve broadband, low phase noise frequency generation... multi-channel synthesizers benefit greatly from the elimination of phase locked loops...

 
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