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SE873 Family  Product User Guide 

 

RF Signals 

 

1VV0301216

 Rev.4

 

Page 46 of 69 

2018-08-24

  

The most common source of interference is digital noise, often created by the fast rise and fall 
times and high clock speeds of modern digital circuitry. For example, a popular netbook computer 
uses an Atom processor clocked at 1.6 GHz. This is only 25 MHz away from the GNSS signal, 
and depending upon temperature of the SAW filter, can be within its passband. Because of the 
nature of the address and data lines, this would be broadband digital noise at a relatively high 
level. 

Such devices are required to adhere to a regulatory standard for emissions such as FCC Part 15 
Subpart J Class B or CISPR 22. However, these regulatory emission levels are far higher than 
the GNSS signal. 

 

Shielding 

Shielding the RF circuitry generally is ineffective because the interference is received by the 
GNSS antenna itself, the most sensitive portion of the RF path. The antenna cannot be shielded 
because it could not then receive the GNSS signals. 

There are two solutions, one is to move the antenna away from the source of interference, and 
the other is to shield the digital interference source to prevent it from getting to the antenna. 

 

Powering an External LNA 

An external LNA requires a source of power. Many active antennas accept a 3 V or  
5 V DC voltage that is impressed upon the RF signal line.  

Two approaches can be used:  

1.  Use an inductor to tie directly to the RF trace. This inductor should be at self-resonant at L1 

(1.57542 GHz) and should have good Q for low loss. The higher the inductor Q, the lower 
the loss will be. The side of the inductor connecting to the antenna supply voltage should be 
bypassed to ground with a good quality RF capacitor, again with self-resonance at the L1 
frequency. 
 

2.  Use a quarter wave stub in place of the inductor. The length of the stub is designed to be 

exactly ¼ wavelength at L1, which has the effect of making an RF short at one end of the 
stub to appear as an RF open at the other end. The RF short is created by a high quality RF 
capacitor operating at self-resonance. 

 

The choice between the two would be determined by: 

•

 

RF path loss introduced by either the inductor or quarter wave stub.

 

•

 

Cost of the inductor.

 

•

 

Space availability for the quarter wave stub. 

Simulations done by Telit show the following losses: 

 

 

 

 

 

Table 9-1 Inductor Loss 

Since this additional loss occurs after the LNA, it is generally not significant unless the circuit is 
being designed to work with both active and passive antennas. 

Inductor 

Additional signal loss 

(dB) 

Murata LQG15HS27NJ02  

0.65 

Quarter wave stub on FR4 

0.59 

Coilcraft B09TJLC (used in ref. design) 

0.37 

Содержание SE873 Series

Страница 1: ...SE873 Family Product User Guide 1VV0301216 Rev 4 2018 08 24...

Страница 2: ...s for copyrighted material including the exclusive right to copy reproduce in any form distribute and make derivative works of the copyrighted material Accordingly any copyrighted material of Telit an...

Страница 3: ...Activities IV Trademarks TELIT and the Stylized T Logo are registered in Trademark Office All other product or service names are the property of their respective owners V Third Party Rights The softw...

Страница 4: ...SE873 Family Product User Guide Product Applicability Table 1VV0301216 Rev 4 Page 4 of 69 2018 08 24 PRODUCT APPLICABILITY TABLE PRODUCT SE873 SE873Q5 Table 0 1 Product Applicability Table...

Страница 5: ...valuation Unit 17 4 PRODUCT FEATURES 18 Multi Constellation Navigation 18 Quasi Zenith Satellite System QZSS support 18 Satellite Based Augmentation System SBAS 18 SBAS Corrections 18 SBAS Ranging 18...

Страница 6: ...sentences and their rates 27 Change data rate 27 Switch to OSP protocol 27 OSP Output Messages 28 OSP Input Commands 28 Change output messages 28 Change data rate 28 Switch to NMEA protocol and data...

Страница 7: ...versus Passive Antenna 43 GNSS Antenna Gain 43 System Noise Floor 44 PCB stack and Trace Impedance 44 RF Trace Losses 45 Implications of the Pre Select SAW Filter 45 RF Interference 45 Shielding 46 Po...

Страница 8: ...rage Environmental Limits 58 15 COMPLIANCES 59 EU RED Certification 59 eCall Compliance 59 GOST R 55534 Certification 59 EU RED Declarations of Conformity 60 16 GLOSSARY AND ACRONYMS 62 17 SAFETY RECO...

Страница 9: ...Trace Examples 45 Figure 10 1 SE873 Reference Design Passive Antenna 47 Figure 10 2 SE873 Reference Design Active Antenna 48 Figure 11 1 SE873 Family Mechanical Drawing 50 Figure 12 1 SE873 Family PC...

Страница 10: ...873 Pin out Function Table 31 Table 8 2 DC Characteristics 32 Table 8 3 Absolute Maximum Ratings 32 Table 8 4 DC Supply Voltage 33 Table 8 5 Power Consumption SE873 34 Table 8 6 Power Consumption SE87...

Страница 11: ...iled information about where you can buy the Telit modules or for recommendations on accessories and components visit http www telit com Our aim is to make this guide as helpful as possible Keep us in...

Страница 12: ...tion Danger This information MUST be followed or catastrophic equipment failure and or bodily injury may occur Caution or Warning This is an important point about integrating the product into a system...

Страница 13: ...xtended ephemeris using local or server based solutions o Client Generated Extended Ephemeris CGEE o Server Generated Extended Ephemeris SGEE Jamming Rejection Multipath mitigation Supports passive or...

Страница 14: ...SE873 Family Product User Guide Product Description 1VV0301216 Rev 4 Page 14 of 69 2018 08 24 Block Diagram Figure 2 1 SE873 Block Diagram...

Страница 15: ...SE873 Family Product User Guide Product Description 1VV0301216 Rev 4 Page 15 of 69 2018 08 24 SE873 Modules Photos Figure 2 2 SE873 module photo Figure 2 3 SE873Q5 module photo...

Страница 16: ...SE873 Family Product User Guide SE873 Evaluaton Kit EVK 1VV0301216 Rev 4 Page 16 of 69 2018 08 24 3 SE873 EVALUATON KIT EVK Figure 3 1 Evaluation Kit EVK contents...

Страница 17: ...SE873 Family Product User Guide SE873 Evaluaton Kit EVK 1VV0301216 Rev 4 Page 17 of 69 2018 08 24 SE873 Evaluation Unit Figure 3 2 SE873 Evaluation unit...

Страница 18: ...llites SBAS corrections are disabled by default but can be enabled via OSP MIDs 133 138 and 170 commands Thereafter the receiver will demodulate and use corrections data from the SBAS signal for satel...

Страница 19: ...eceiver assumes a value for altitude and uses it to estimate the nav solution Under warm and hot start conditions the receiver uses the last known value of altitude which is a good assumption in most...

Страница 20: ...hen this feature is enabled the receiver starts in 1 Hz mode and continues until it achieves an over determined fix with 5 or more satellites It then computes and outputs solutions 5 or 10 times per s...

Страница 21: ...in high gain mode total RF gain should not exceed the recommend limit of 30dB When GPIO8 is high the external LNA should be enabled When low it should be disabled Active antenna or External LNA with L...

Страница 22: ...r based on satellite signal strength SiRFSmartGNSS 1 SiRFSmartGNSS 2 Periodic Fixes Trickle Power Power cycling RUN STANDBY Push To Fix Power cycling RUN HIBERNATE SiRFAware Periodic data collection u...

Страница 23: ...will go to FULL POWER if signals are weak or the fix is lost 1PPS is not available TricklePower mode yields significant power savings in strong signal conditions Push to Fix This mode cycles between F...

Страница 24: ...ss 1 5 GPS BeiDou 2 5 Test Conditions 24 hr Static 130 dBm Full Power mode Table 5 1 SE873 Family Horizontal Position Accuracy Time to First Fix Constellations s Start Type Max TTFF s GPS Hot 1 1 Warm...

Страница 25: ...s State Minimum Signal Level dBm SE873 SE873Q5 GPS Acquisition 146 147 Navigation 161 160 Tracking 165 164 GPS GLO Acquisition 146 146 Navigation 161 161 Tracking 165 167 GPS BeiDou Acquisition 146 14...

Страница 26: ...ng the output messages NMEA Output Messages 1 Hz fix rate 5 Hz or 10 Hz may be selected Standard Messages These messages are sent by default Message ID Description Frequency RMC GNSS Recommended minim...

Страница 27: ...mmand responses This interface provides configuration and control over selected firmware features and operational properties of the module The format of a command is command ID parameters cr lf Comman...

Страница 28: ...Please refer to SiRF OSP documentation OSP Input Commands Change output messages Use OSP MID 166 to change the output messages Change data rate Use OSP MID 134 to change the baud rate Switch to NMEA...

Страница 29: ...y 1VV0301216 Rev 4 Page 29 of 69 2018 08 24 7 FLASH UPGRADABILITY The firmware stored in the internal Flash memory of the SE873 may be upgraded via the serial port TX RX pads Please refer to the SE873...

Страница 30: ...SE873 Family Product User Guide Electrical Interface 1VV0301216 Rev 4 Page 30 of 69 2018 08 24 8 ELECTRICAL INTERFACE Module Pin out Figure 8 1 SE873 Pin out Diagram...

Страница 31: ...or SPI signal lines depending on the firmware options enabled See section 8 5 Serial I O Ports Configuration and Operation 12 GPIO7 I Output 7 SYSTEM ON O Indicates the power state of the module Also...

Страница 32: ...al pull down resistor equivalent 51 91 180 k LI Input leakage at VI 1 8 V or 0 V 10 10 A LO Tristate output leakage at VO 1 8 V or 0 V 10 10 A CI Input capacitance digital output 8 pF Table 8 2 DC Cha...

Страница 33: ...he memory from accidental writes during a power down condition This reset forces the module into a low power stand by state To prevent the reset the 1 8 volt supply must be regulated to be within 50 m...

Страница 34: ...igation Tracking GPS Only 51 83 63 91 mW GPS and Glonass 62 92 94 124 mW GPS and BeiDou 71 111 93 135 mW Table 8 5 Power Consumption SE873 Low Power Modes State Constellation Typ Units Trickle Power G...

Страница 35: ...racking GPS Only 44 67 61 83 mW GPS and Glonass 44 70 52 81 77 101 mW GPS and BeiDou 55 87 83 95 mW Operating temperature 25 C Supply voltage 1 8 VDC nominal Table 8 7 Power Consumption SE873Q5 Low Po...

Страница 36: ...The module transitions between RUN and STANDBY via TricklePower modes and between RUN and HIBERNATE via PushToFixII and SiRFaware modes It can also transition from RUN to HIBERNATE by de asserting th...

Страница 37: ...ought out to a test point Max voltage is 1 8 V Status output Signals SYSTEM ON See section 8 3 1 ON OFF input and SYSTEM ON output GNSS_ON GPIO8 See section 4 12 Internal LNA for details 1PPS 1PPS is...

Страница 38: ...p Pulldown UART I2 C MULTI MASTER SPI slave GPIO6 Weak internal pulldown Pullup 10 k to 1 8 V may become CTS Float Float becomes SCLK GPIO7 Weak internal pullup Float may become RTS Pulldown 10 k to g...

Страница 39: ...ested and verified If the module is operated in TricklePower mode a baud rate of at least 38 400 is recommended This reduces the time required to empty the output buffer and allows the receiver to dro...

Страница 40: ...6V power supply are required on the clock and data lines Table 8 11 I2C Pin Assignments SPI Operation See section 8 5 1 Primary Serial Port Configuration to specify SPI interface for the primary port...

Страница 41: ...ctive antenna or external LNA is used an external bias T is required to provide voltage to it A DC blocking capacitor is also required to prevent DC voltage from being applied to RF IN pin Burnout Pro...

Страница 42: ...an angle 5 of degrees or more above the horizon The receiver will display a reported C No of 40 dB Hz for a GPS signal level of 130 dBm at the RF input This assumes a SEN system equivalent noise of th...

Страница 43: ...nal is attenuating the line of sight signal then the RHCP antenna would show a higher signal level than a linearly polarized antenna because the interfering signal is rejected However in the case wher...

Страница 44: ...an the difference between being able to use a particular satellite signal or not System Noise Floor The receiver will display a reported C No of 40 dB Hz for an input signal level of 130 dBm The C No...

Страница 45: ...If an external amplifier is to be used with the receiver the overall design should be checked for RF stability to prevent the external amplifier from oscillating Amplifiers that are unconditionally st...

Страница 46: ...xternal LNA An external LNA requires a source of power Many active antennas accept a 3 V or 5 V DC voltage that is impressed upon the RF signal line Two approaches can be used 1 Use an inductor to tie...

Страница 47: ...Family Product User Guide Reference Designs 1VV0301216 Rev 4 Page 47 of 69 2018 08 24 10 REFERENCE DESIGNS Note XC6221 is the DC voltage supply regulator Figure 10 1 SE873 Reference Design Passive An...

Страница 48: ...mily Product User Guide Reference Designs 1VV0301216 Rev 4 Page 48 of 69 2018 08 24 Note XC6221 is the DC voltage supply regulator Figure 10 2 SE873 Reference Design Active Antenna See notes on the ne...

Страница 49: ...a standard serial input usually a UART with a default bit rate of 9600 bps 8 data bits 1 stop bit and no parity As is the case with all UART data the idle state is logic one This is a 1 8 volt logic l...

Страница 50: ...SE873 Family Product User Guide Mechanical Drawing 1VV0301216 Rev 4 Page 50 of 69 2018 08 24 11 MECHANICAL DRAWING Figure 11 1 SE873 Family Mechanical Drawing...

Страница 51: ...SE873 Family Product User Guide PCB Footprint 1VV0301216 Rev 4 Page 51 of 69 2018 08 24 12 PCB FOOTPRINT Figure 12 1 SE873 Family PCB Footprint...

Страница 52: ...ode with the module serial number Contact a Telit representative for information on specific module serial numbers Product Label SE873 Family Figure 13 1 SE873Q5 Product Label Key Description 0 Pin 1...

Страница 53: ...ackaging and Delivery SE873 modules are available in Tape and Reel packaging of 450 pcs or 1500 pcs Each reel is dry packaged and vacuum sealed in a Moisture Barrier Bag MBB with two silica gel packs...

Страница 54: ...SE873 Family Product User Guide Product Packaging and Handling 1VV0301216 Rev 4 Page 54 of 69 2018 08 24 Figure 13 3 Product Packaging Tape and Reel 450 pcs...

Страница 55: ...with desiccant and humidity indicator card The SE873 parts must be placed and reflowed within 168 hours of first opening the hermetic seal provided the factory conditions are less than 30 C and less t...

Страница 56: ...SE873 Family Product User Guide Product Packaging and Handling 1VV0301216 Rev 4 Page 56 of 69 2018 08 24 Figure 13 4 Moisture Sensitive Device Label...

Страница 57: ...older reaches liquidus temperature while the module is inverted Note JEDEC standards are available for free from the JEDEC website http www jedec org Assembly Considerations During board assembly and...

Страница 58: ...bulb temperature of 35 C whichever is less Altitude 1500 m to 100 000 m Maximum Vehicle Dynamics 600 m s acquisition and navigation 2 G acceleration Table 14 1 Operating Environmental Limits Storage...

Страница 59: ...zardous substances in electrical and electronic equipment RoHS Manufactured in an ISO 9000 2008 accredited facility Manufactured to TS 16949 2009 requirement upon request EU RED Certification The Teli...

Страница 60: ...SE873 Family Product User Guide Compliances 1VV0301216 Rev 4 Page 60 of 69 2018 08 24 EU RED Declarations of Conformity Figure 15 1 EU RED Declaration of Conformity SE873...

Страница 61: ...SE873 Family Product User Guide Compliances 1VV0301216 Rev 4 Page 61 of 69 2018 08 24 Figure 15 2 EU RED Declaration of Conformity SE873Q5...

Страница 62: ...urs when a receiver begins operation with unknown position time and ephemeris data typically when it is powered up after a period on inactivity Almanac information may be used to identify previously v...

Страница 63: ...GLONASS BDS and Galileo GPS Global Positioning System The U S GNSS a satellite based positioning system that provides accurate position velocity and time data GPS is operated by the US Department of D...

Страница 64: ...t can also result from a power up See Cold Start Warm Start and Hot Start Contrast with Reset and Reacquisition Reset A receiver beginning operation after a hardware reset signal on a pin generally us...

Страница 65: ...osition solution from a specified starting condition This value will vary with the operating state of the receiver the length of time since the last position fix the location of the last fix and the s...

Страница 66: ...m integrator is responsible for the functioning of the final product therefore care must be taken with components external to the module as well as for any project or installation issue Should there b...

Страница 67: ...ity class The device must be supplied with a limited power source that meets clause 2 5 of the EN 60950 1 standard These requirements are For power supplies without overcurrent protection device Short...

Страница 68: ...iption of GPI08 Corrected SYSTEM_ON to ON_OFF in 9 4 4 Corrected active antenna reference design Corrected LNA Noise Figure example Added package description in 2 1 Updated glossary Clarified GLONASS...

Страница 69: ......

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