MIA-M10Q - Integration manual
Time information can be sent to the receiver at every startup. Coarse time information (accuracy
of the order of seconds) is sufficient for a warm start and to use AssistNow data. For a hot start,
accurate time information must be available on the host and provided to the receiver using the time
aiding feature. In addition to time information, also GNSS orbit data needs to be maintained in the
receiver's BBR or aided at startup for warm and hot starts.
If time information is not available, the receiver needs to acquire time from satellite signals before
GNSS orbit data can be used. Time acquisition takes approximately seven seconds under good
signal conditions whereas acquiring the GNSS orbit data takes significantly longer. Maintaining the
GNSS orbit data may therefore help to reduce TTFF even if time aiding is not used.
The time aiding feature with accurate time requires an external signal connected to the
EXTINT pin.
ON/OFF power save mode (PSMOO) and the software standby mode with a defined off
period are not supported without an RTC.
Figure 27: RTC not used
3.3 RF interference
The received GNSS signal power at the antenna is very low compared to other wireless
communication signals. The nominal -130 dBm received GNSS signal strength is below the thermal
noise floor, making a GNSS receiver susceptible to interference from nearby RF sources of any kind.
As an example, cellular applications emit signals with power levels of approxi30 dBm, while
the GNSS signal is less than -128 dBm when reaching the antenna. By simply comparing these
numbers it is obvious that interference issues must be seriously considered during the design
phase.
3.3.1 In-band interference
Although the radio communications standards prevent intentional RF signal sources from
interfering the GNSS frequencies, many devices emit RF power into the GNSS band at levels much
higher than the GNSS signal itself.
One reason is that the frequency band above 1 GHz is not well regulated with regards to EMI,
and even if permitted, signal levels are much higher than the GNSS signal power. In particular,
all types of digital equipment, such as PCs, digital cameras, LCD screens, etc. tend to emit a
broad frequency spectrum up to several GHz of frequency. Also wireless transmitters may generate
spurious emissions that fall into the GNSS band.
UBX-21028173 - R01
3 Hardware integration
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