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Multi Spider - ORG4572 Datasheet

Revision 3.0

November 23, 2014

20. DESIGN CONSIDERATIONS

20.1. ANTENNA

Antennas for GPS and GLONASS have a wider bandwidth than pure GPS antennas.

Some wideband antennas may not have a good axial ratio to block reflections of RHCP GPS and

GLONASS signals. These antennas have lower rejection of multipath reflections and tend to degrade

the overall performance of the receiver.

20.1.1. PASSIVE ANTENNA

Design with passive antenna requires RF layout skills and can be challenging.

20.1.2. ACTIVE ANTENNA

While designing with active antenna consider using WAKEUP output to control auxiliary DC bias.

20.2. RF

Multi Spider ORG4572 operates with received signal levels down to -167dBm and can be affected by

high absolute levels of RF signals, moderate levels of RF interference near the GNSS bands and by low-

levels of RF noise in the GNSS band.

RF interference from nearby electronic circuits or radio transmitters can contain enough energy to

desensitize ORG4572. These systems may also produce levels of energy outside of GNSS band, high

enough to leak through RF filters and degrade the operation of the radios in ORG4572.

This issue becomes more critical in small products, where there are industrial design constraints.

In that environment, transmitters for Wi-Fi, Bluetooth, RFID, cellular and other radios may have

antennas physically close to the GNSS receiver antenna.

To prevent degraded performance of ORG4572, OriginGPS recommends performing EMI/jamming

susceptibility tests for radiated and conducted noise on prototypes and assessing risks of other factors.

Contact OriginGPS for application specific recommendations and design review services.

21. OPERATION

When power is first applied, ORG4572 goes into a Hibernate state while integrated RTC starts and internal

Finite State Machine (FSM) sequences though to “Ready-to-Start” state.

Host is not required to control external master reset since module’s internal reset circuitry handles detection

of power application.

While in “Ready-to-Start” state, ORG4572 awaits a pulse to the ON_OFF input.

Since integrated RTC startup times are variable, host is required either to wait for a fixed interval or to

monitor a short Low-High-Low pulse on WAKEUP output that indicates FSM “Ready-to-Start” state.

Another option is to repeat a pulse on the ON_OFF input every second until the module starts by either

detecting a stable logic high level on WAKEUP output or neither generation of UART messages.