Jackson Labs Mini-JLT GNSS, Руководство пользователя

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Mini-JLT GNSS™
User Manual
By selecting gain values of >1, the PLL loop parameter Proportional gain (SERV:EFCscale) will be
increased after power on, thus increasing loop aggressiveness and improving lock PLL time. It is not
desirable to maintain a high loop gain for longer than necessary to lock the PLL since high loop gains
come at the expense of increased phase noise (reduced short term stability). The FASTLOCK
mechanism will automatically reduce the FASTLOCK gain over a period of time specified by the
SERVo:FALEngth command, during which time the FASTLOCK gain is slowly decreased from its
initial value to 1.0x.
Setting the FASTLOCK gain to 2 for example will result in the Proportional gain value stored in the
SERVo:EFCscale parameter to be multiplied by 2x initially after power on.
This dynamic gain is slowly reduced until the gain is back to 1.0x, the value stored in the
SERVo:EFCScale parameter.
For example:
if we set SERVo:FASTlock to 2, and SERVo:FALEngth to 3600, and SERVo:EFCScale is set to 0.7
Then initially the unit will multiply the EFCscale by 2x, and an effective EFCscale value of 1.4 is
applied to the PLL loop.
This increased gain value difference will be reduced every second by 1/3600, so that the gain after
two seconds would be: 1.3998, until after 3600 seconds the gain has been reduced back to its long
term value of 0.70 as stored in the SERVo:EFCscale parameter.
Disabling the FASTLOCK mode is accomplished by setting the SERVo:FASTlock to 1. This will set
the dynamic gain to 1.0, effectively disabling the fastlock feature.
This command has the following format:
SERVo:FASTlock <int> [1,20]
3.10.2 SERVo:FALEngth
This command adjusts the length of time during which the FASTLOCK feature is active, please see
the command SERVo:FASTlock above.
It can be set from 100 seconds to 20.000 seconds. The Dynamic FASTLOCK gain is slowly reduced
until it reaches a gain of 1.0 after the FALEngth period of seconds. During this time the PLL loop
gain is increased by the amount specified in the SERVo:FASTlock parameter, which will result in a
faster initial phase lock to UTC after power-on, while giving the lowest possible noise floor (best
short term stability) during normal operation.
This command has the following format:
SERVo:FALEngth <int> [100,20000]
3.10.3 SERVo:COARSeDac
This command sets the coarse DAC that controls the EFC. The Mini-JLT™ control loop
automatically adjusts this setting. The user should not have to change this value.
This command has the following format:
SERVo:COARSeDac <int> [0,225]