Jackson Labs Mini-JLT GNSS, Руководство пользователя

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Mini-JLT GNSS™
User Manual
The SCPI and NMEA outputs are sent to both the TTL serial output and the USB output, and the
SCPI control commands can be sent to either the TTL serial port, or the USB serial input, both
signals are “ored” together on the board. Commands can thus be sent to the board via both ports, but
should not be sent to the TTL serial port and the USB serial port simultaneously, as this will result in
non-destructive garbling of the serial transmission.
Connect an active or passive GNSS antenna that is compatible to 3.3V or 5V antenna power, and
connect this antenna prior to turning-on the board. Use a lightning arrestor on the antenna feed for
safety and to prevent damage, injury, or death in case of a lightning strike.
2.1.4 Coaxial Connectors
The GNSS antenna connector, the 1PPS connector, and the 10MHz connectors on the Mini-JLT™
board are generic SMA types.
2.2 Power
The unit is powered from a +4.0V to +6V DC source, with +5.0V nominal voltage. The current is
typically less than 0.6A at 5V. Connect a clean +5V power supply to pin 6 of J1, and ground to pin 4
of J1. Both USB power and ex5V power can be connected at the same time to the unit, but
USB power will not be used to drive circuits on the PCB.
2.3 Multi-GNSS Capabilities
The Mini-JLT GNSS™ is capable of simultaneously receiving multiple GNSS systems at one time.
Concurrent GNSS operation aids performance by allowing reception of up to 72 GNSS satellites in
challenged reception areas such as in urban canyons, under foliage, indoors, or close to the earth's
poles, etc. Using multiple GNSS systems also increases robustness by not relying on a single GNSS
system. Several of the systems operate at different carrier frequencies, so using multiple can increase
immunity against jamming which often occurs at only one frequency.
The multiple GNSS systems each have their own reference time and representation of UTC. For
example, GPS uses the GPS time standard and provides a method to convert GPS time to UTC as
defined by the US Naval Observatory (USNO). GLONASS, Galileo and BeiDou have similar
reference times and UTC definitions. The Mini-JLT GNSS™ automatically adjusts for offsets
between the different GNSS time reference standards and synchronizes the 1PPS output to UTC
(USNO) when GPS is being received. If GPS is not being received, the 1PPS output is synchronized
to the best representation of UTC (USNO) available.
The selection of GNSS systems is made with the GPS:SYST:SEL command as detailed in
Section
3.3.29 . Because these systems operate at different carrier frequencies with different
bandwidths, it is necessary to use a GNSS antenna that is designed to receive all the required GNSS
systems.
Also, the internal GNSS receiver is restricted to operation at two different carrier frequencies. GPS,
SBAS, QZSS and Galileo operate at the same L1/E1 carrier frequency. GLONASS operates at a
separate G1 carrier frequency and BeiDou separately at the B1 carrier frequency. Based on this
restriction below are several valid combinations of GNSS systems that can be selected:
GPS, SBAS, GLONASS