EVA-8M and EVA-M8 series - Hardware Integration Manual
UBX-16010593 - R06
Design-in
Page 16 of 47
Early Production Information
2.4.4
Time aiding
Time can also be sent by UBX message at every startup of the EVA-8M / EVA-M8 series GNSS
modules. This can be done to enable warm starts, AssistNow Autonomous and AssistNow Offline.
This can be done when no RTC is maintained.
To enable hot starts correctly, the time information must be known accurately and thus the
TimeMark feature has to be used.
For more information about time aiding or timemark see the
u-blox 8 / u-blox M8 Receiver Description
Including Protocol Specification [3].
☞
For information of this use case, it is mandatory to contact u-blox support team.
☞
For Power Save Mode operations where the RTC is needed, the time aiding cannot be used. This is
because the host does not have any information about when the EVA-8M / EVA-M8 series GNSS
modules turn from OFF status to ON status during ON/OFF operation of Power Save Mode.
2.5
RF input
The EVA-8M / EVA-M8 series GNSS module RF-input is already matched to 50
Ω
and has an internal
DC block. To achieve the performance values as written in the
EVA-M8 Data Sheet [1] and the EVA-
8M Data Sheet [2], an active antenna with a good LNA inside or the mandatory LNA with passive
antenna in front of EVA-8M / EVA-M8M GNSS module (must have a noise figure below 1dB). EVA-
M8Q with the passive antenna an external LNA is only recommended.
The EVA-M8 series GNSS modules can receive and track multiple GNSS system (e.g. GPS, Galileo,
GLONASS, BeiDou and QZSS signals). Because of the dual-frequency RF front-end architecture, two
GNSS signals (GPS L1C/A, GLONASS L1OF, Galileo E1B/C and BeiDou B1) can be received and
processed concurrently. This concurrent operation is extended to 3 GNSS when GPS and Galileo are
used in addition to GLONASS or BeiDou
The EVA-8M can receive GPS L1C/A and GLONASS L1OF signals. However, because of differing
center frequencies, the receiver has to be switched to GPS or GLONASS mode by using a UBX
message.
☞
Concurrent reception of both GPS and GLONASS is not possible with the EVA-8M.
2.5.1
Active Antenna
In case an active antenna is used, just the active antenna supply circuit has to be added in front of the
modules RF-input, see Figure 16. In case the active antenna has to be supervised, either the 2-pin
active antenna supervisor circuit (see Figure 19) or the 3-pin active antenna supervisor circuit (see
Figure 20), has to be added to the active antenna circuit. These active antenna supervisor circuits also
make sure that the active antenna is turned off in Power Save Mode stages.
2.5.2
Passive Antenna
If a passive antenna is connected to a EVA-8M / EVA-M8M series GNSS module, it is mandatory to
use an additional LNA in front of module to achieve the performance values as written in the
EVA-M8
Data Sheet [1] and the EVA-8M Data Sheet [2], see Annex A. EVA-M8Q with passive antenna, an
external LNA is only recommended. An LNA (U1) alone would make the modules more sensitive to out-
band jammers, so an additional GNSS SAW filter (F1) has to be connected between the external LNA
(U1) and the EVA-8M / EVA-M8M series GNSS module RF-input. If strong out-band jammers are close
to the GNSS antenna (e.g. a GSM antenna), see section 2.5.3.
The LNA (U1) can be selected to deliver the performance needed by the application in terms of:
•
Noise figure (sensitivity)
