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Commands Chapter 5
EuroPak-15a Receiver User Manual Rev 5 65
5.3.15 SPLLBW Configure Phase-Lock-Loop Bandwidth
1. This command can fundamentally change the way that the receiver operates. Do not alter the default
settings unless you are confident that you understand the consequences.
2. When you change this command, the selected channel loses lock and the locktime for its tracking
satellite is reset to zero.
3. The log order for the C/A signal is 3rd order.
This command sets the PLL low-pass filter bandwidth for one signal channel.
A time filtered square of the L1 carrier phase tracking loop error signal is used to track the performance of this
tracking loop. This value is used as the variance of L1 carrier phase measurements. The threshold specified by
this command is compared with the loop variance to determine when the signal tracking lock time is reset. The
resetting of the signal lock time is used to indicate that conditions exist in which a cycle slip might occur.
The time filtering that is performed on the loop variance determination is controlled using the third argument of
this command. This value is used to compute the first order time constant that provides a noise equivalent
bandwidth for the specified bandwidth. The filtering equation used is:
new value = e
-ΔTω
× (old data) + (1 - e
-ΔTω
) × (new data)
where
ΔT = the PLL sampling rate, and
ω = 4 × filter constant
Syntax: Message ID: 801
Example:
SPLLBW 0 1.0
Table 32: PLL Bandwidth Values
SPLLBW PSIGCHAN BW
Field
Field
Name
Valid Values Description Format
Binary
Bytes
Binary
Offset
1 header
This field contains the Abbreviated ASCII command name. See Section 4.1
on Page 31.
H 0
2 psigchan 0-15
The parameters should be applied to
this signal channel.
Ulong 4 H
3 bw
See Table 32 below.
PLL low-pass filter bandwidth in Hz. Float 4 H+4
Frequency Valid Bandwidth Values
GPS C/A signals 0.5 to 15 Hz
Galileo L1 signals 0.5 to 15 Hz
Galileo E5a signals 0.5 to 15 Hz