Simple Comparison for GPS Modules: Ublox, Sirf III, and MTK GPS
In the GPS tracking business, many manufacturers and designers use GPS modules as below: Ublox, Sirf Star III, and MTK GPS.
Below are the comparisons between the three GPS chips based on our designing and manufacturing experience:
MTK GPS
newcomer in the GPS tracking business, and fast-growing. it has a little bad performance in GPS signal acquisition and stability. If the vehicle comes out of the tunnel, it may take some time to get the GPS signal. But the cost is good.
Sirf III GPS
the cost and performance are between Ublox and MTK GPS. Globalsat and RoyalTek GPS modules are based on the Sirf Star III. The techniques may be a little old compared to the Ublox GPS module nowadays. The accuracy of GPS signals when the vehicles are still would be a little wild sometimes.
Ublox GPS
it works very stable and good performance. it acquires GPS signals very fast whether the vehicles are moving or still. Also, the GPS signal acquisition is best if the vehicles come out of the tunnels. and GPS accuracy is best. The craftsmanship and appearance of Ublox are better. But the cost is higher.
Do you want to know the uBLox GPS accuracy in real life? Checking below!
With Ublox GPS chip M8U or M8L, we developed a wonderful feature: dead-reckoning, which allows you to track your car in underground parking or tunnels. Even in severe environments with plenty of containers and weak GPS signal, NEO-M8U or NEO-M8L still has good performance
GPS tracker shows the dead-reckoning in underground parking and tunnels ↓<
GPS tracker shows the dead-reckoning between containers in seaport ↓
These three GPS chips are popular on the market, especially with Chinese GPS tracking manufacturers. Because of different and specific needs for GPS tracking, people would choose the right modules for their customization. GPS tracking business is more like a niche market. Clients’ needs are not the same mostly because most of them are trying to control and manage their different vehicles or fleets.
What can we do to improve the GPS performance?
These drawbacks for Sirf III and MTK GPS (even uBlox) can be avoided by a good algorithm in firmware or the delicate hardware design or professional installation especially the better GPS antenna location. So manufacturers can make most of the three GPS modules meeting client’s needs.
good algorithm in firmware
Good algorithm in firmware means a robust firmware structure that can handle most known or unknown bugs. GPS drifting issue can’t be eliminated due to the restriction of GPS by the US military and GPS signal reception. But we can filter these driftings by monitoring other important factors like an engine on/off status, trembles status intensity level, and time of duration—-no trembles or slight trembles indicate no car running, speed offered by GPS-car can’t drive 200km/h instantaneously when it was 0km/h seconds ago, mileage taken—-car can’t fly hundreds of miles away in seconds. One good method is that keep using the same old position coordinates in the coming data string when engine status is off or no trembles.
delicate hardware design
Delicate hardware design requires experienced hardware engineers’ work. in the design trends, the GPS part is designed smaller and internal in devices. So engineers would consider much more on layout of PCB. The GPS part should be placed away from other metal components and other chip components, resistors, capacitors, and inductors. Make sure the GPS part lives in a clean and quiet environment: no any type of components under it; or it could be acceptable worse: make sure the GPS part is on top of all components. The metal shielding cover should be Electroplated and connected to the Ground well. Keep away from the EMC noise sources like CPU, SDRAM, oscillators DC/CD, and power source. Car explosion-proof membrane would affect the GPS signal, too. In other words, the GPS part should be treated well.
better device placement
An external GPS antenna is better than an internal one. An active GPS antenna is better than a passive one. Try to place the GPS antenna outside of car, on top of the car. Or on the dashboard, under the windshield. The arched side faces the sky, and flat side towards ground. Actually the gps coordinates indicates the position where the gps antenna is, not the installed gps tracker position.
MTK gps chip MT3337 GPS All-in-one:
• Specifications
-22 tracking / 66 acquisition-channel GPS receiver
-Supports up to 210PRN channels
-Supports WAAS/EGNOS/MSAS/GAGAN
-12 multi-tone active interference cancelllers(ISSCC2011 award)
-RTCM ready
-Indoor and outdoor multi-path detection and compensation
-Supports FCC E911 compliance and A-GPS
-Max. fixed updata rate to 5Hz
• Advanced software features
-AlwaysLocateTM advanced location awareness technology
-EPOTM orbit prediction
-Support logger function •Reference oscillator
-TCXO
•Frequency: 16.368 MHz, 26 MHz
•Frequency variation: +/-2.0ppm
•RF configuration
-4-bit IF signal
-SoC, integrated in single chip with CMOS process
•ARM7EJ-S CPU
-Up to 98MHz processor clock
-Dynamic clock rate control
•Pulse-per-second(PPS) GPS time reference
-Adjustable duty cycle
-Typical accuracy:+/- ns
•Power scheme
-A 1.8 volts SMPS build-in SOC
-Direct lithium battery connection(2.8-4.3 volts)
-Self build 1.2 volts RTC LDO, 1.2 volts core LDO, and 2.8 volts TCXO LDO
•Build-in reset controller media Confidential
-Does not need of external reset control IC
•Internal real-time clock(RTC)
-32.768 KHz +/-ppm crystal
-Timer pin for external device on/off control
-1.2volts RTC clock output
•Serial interface
-UART: 4800/9600/38400/115200 bps
-GPIO interface(up to 16 pins) •NMEA
-NMEA 0183 standard V3.01 and backward compliance
-Supports 219 difference data
•Superior sensitivities
-Acquisition:-148 dBm(cold)/-163dBm(hot)
-Tracking: -165dBm
Ultra-low power consumption
-Acquisition: 25mW
-Tracking: 18mW
-AlwaysLocateTM: 3mW
•Package
-VFBGA: 4.3m*4.3m, 57balls, 0.5mm pitch
•Sim hardware design
-52mm2 solution footprint with all software features inside
-9 passive external components