INSTALLATION AND OPERATION
USER MANUAL
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UM981 BDS Multi Frequency RTK INS Integrated Positioning Module

UM981
BDS/GPS/GLONASS/Galileo/QZSS
All-constellation Multi-frequency
RTK/INS Integrated Positioning Module
Copyright© 2009-2023, Unicore Communications, Inc.
Data subject to change without notice.

Revision History

Version	Revision History	Date
R1.0	First release	Sept. 2023

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This manual provides information and details on the products of Unicore
Communication, Inc. (“Unicore”) referred to herein.
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The information contained in this manual is provided “as is” and is believed to be true and correct at the time of its publication or revision. This manual does not represent, and in any case, shall not be construed as a commitments or warranty on the part of  Unicore with respect to the fitness for a particular purpose/use, the accuracy, reliability and correctness of the information contained herein.
Information, such as product specifications, descriptions, features and user guide in this manual, are subject to change by Unicore at any time without prior notice, which may not be completely consistent with such information of the specific product you purchase.
UM981 User Manual
Should you purchase our product and encounter any inconsistency, please contact us or our local authorized distributor for the most up-to-date version of this manual along with any addenda or corrigenda.

Foreword

This document describes the hardware information, specifications, packaging and the use of Unicore UM981 modules.
Target Readers
This document is written for technicians who are familiar with GNSS modules.

Introduction

UM981 is a new generation of GNSS high precision RTK/INS integrated positioning module from Unicore. It supports BDS/GPS/GLONASS/Galileo/QZSS all constellations and can simultaneously track BDS B1I/B2I/B3I/B1C/B2a/B2b, GPS L1/L2/L5, GLONASS G1/G2/G3, Galileo E1/E5a/E5b/E6, QZSS L1/L2/L5, NavIC L5 and SBAS. The module is mainly used in surveying and mapping, intelligent driving *, precision agriculture, etc.
UM981 is based on NebulasIV TM , a GNSS SoC which integrates the RF-baseband and high precision algorithm. Besides, the SoC integrates a dual-core CPU, a high speed floating point processor and an RTK co-processor. It is processed with 22 nm low power design and supports 1408 channels, being able to output 100 Hz IMU raw data and up to 50 Hz * RTK positioning result, providing powerful data processing ability.
With the built-in JamShield anti-jamming technology, UM981 has improved the performance of RTK solution for multiple modes and frequencies, ensuring fast RTK initialization speed, high accuracy of measurement and high reliability even in the most challenging environments such as urban canyons and tree shades.
Furthermore, UM981 supports various interfaces such as UART, I 2 * C , SPI * , as well as 1PPS, EVENT, CAN * , which meets customers’ needs in different applications. * The application marked with an asterisk is supported by customized model or firmware.
* Data update rate can reach 50 Hz after firmware upgrade.
* I 2 C, SPI, CAN: reserved interfaces, not supported currently

1.1 Key Features

• Based on the new generation GNSS SoC – NebulasIV TM, which integrates RF- baseband and high precision algorithm
• 17 mm × 22 mm × 2.6 mm, surface-mount device
• Supports all-constellation multi-frequency on-chip RTK positioning solution
• Supports BDS B1I/B2I/B3I/B1C/B2a/B2b + GPS L1/L2/L5 + GLONASS G1/G2/G3 + Galileo E1/E5a/E5b/E6 + QZSS L1/L2/L5 + NavIC L5 + SBAS
• All-constellation multi-frequency RTK engine and advanced RTK processing technology
• Instantaneous RTK initialization technology
• Independent tracking of different frequencies and 60 dB narrowband anti-jamming technology
• 100 Hz IMU raw data output and up to 50 Hz* RTK positioning result output

1.2 Key Specifications
Table 1-1 Technical Specifications

Basic Information
Channels	1408 channels, based on NebulasIVTM
Constellations	BDS/GPS/GLONASS/Galileo/QZSS
Frequencies	BDS: B1I, B2I, B3I, B1C, B2a, B2b GPS: L1 C/A, L1C, L2P (Y), L2C, L5 GLONASS: G1, G2, G3 Galileo: E1, E5a, E5b, E6 QZSS: L1, L2, L5 NavIC: L5
Power
Voltage	+3.0 V ~ +3.6 V DC
Power Consumption	480 mW (Typical)

Performance

Positioning Accuracy	Single Point Positioning’ (RMS)	Horizontal: 1.5 m
		Vertical: 2.5 m
	DGPS (RMS)12	Horizontal: 0.4 m
		Vertical: 0.8 m
	RTK (RMS)1.2	Horizontal: 0.8 cm + 1 ppm
		Vertical: 1.5 cm + 1 ppm
	Tilt Measurement		10 mm + 0.7 mm/°tilt (accuracy < 2.5 cm within 30°)
Attitude Accuracy	Heading		0.3°
	Roll		0.2°
	Pitch		0.2°
Observation Accuracy (RMS)	BDS	GPS	GLONASS	Galileo
B11/B1C/L1C/L1 C/A/GI/El Pseudorange	10cm	10cm	10cm	10 cm
B1I/B1C/L1C/L1 C/A/G1/E1 Carrier Phase	1 mm	1 mm	1 mm	1 mm
B3I/L2P(Y)/L2C/G2/E6 Pseudorange	10cm	10cm	10cm	10 cm
B3I/L2P(Y)/L2C/G2/E6 Carrier Phase	1 mm	1 mm	1 mm	1 mm
B2I/B2a/B2b/L5/G3/E5a/E5b Pseudorange	10cm	10cm	10cm	10 cm

1 Test results may be biased due to atmospheric conditions, baseline length, GNSS antenna type, multipath effect, number of visible satellites, and satellite geometry.
2 The measurement uses 1 km baseline and a receiver with good antenna performance, regardless of possible errors of antenna phase center offset.

B21/B2a/B2b/L5/03/E5a/E5b Carrier Phase	1 mm	1 1 mm	1 1 mm	1 mm
Time Pulse Accuracy (RMS)	20 ns
Velocity Accuracy3 (RMS)	0.03 m/s
Time to First Fix’ (TTFF)	Cold Start < 12 s
	Hot Start < 4 s
Initialization Time’	< 5 s (Typical)
Initialization Reliability’	> 99.9%
Data Update Rates	100 Hz IMU 50 Hz RTK
Differential Data	RTC M 3.X
Data Format	NMEA-0183, Unicore
Physical Characteristics
Package	54 pin LGA
Dimensions	22 mm x 17 mm x 2.6 mm
Weight	1.91 g t 0.03 g
Environmental Specifications
Operating Temperature	-40 °C — +85 °C
Storage Temperature	-55 °C — +95 °C
Humidity	95% No condensation
Vibration	GJB150.16A-2009, MIL-STD-810F
Shock	GJB150.18A-2009, MIL-STD-810F

3 Open sky, unobstructed scene, 99% @ static
4 -130dBm @ more than 12 available satellites
5 The 50 Hz data update rate is supported after firmware upgrade

Functional Ports

UART × 3
2I * C × 1
SPI * × 1		Slave
CAN * × 1		Shared with UART3

1.3 Block Diagram

RF Part
The receiver gets filtered and enhanced GNSS signal from the antenna via a coaxial cable. The RF part converts the RF input signals into the IF signals, and converts IF analog signals into digital signals required for NebulasIV TM chip (UC9810).
NebulasIV TM SoC (UC9810) 
NebulasIV (UC9810) is UNICORECOMM’s new generation high precision GNSS SoC with
* I 2 C, SPI, CAN: reserved interfaces, not supported currently
22 nm low power design, supporting all constellations and all frequencies with 1408 channels. It integrates a dual-core CPU, a high speed floating point processor and an RTK co-processor, which can fulfill the high precision baseband processing and RTK
positioning on a single chip.

External Interfaces

The external interfaces of UM981 include UART, I 2 * C , SPI * , CAN * , PPS, EVENT, RTK_STAT, PVT_STAT, ERR_STAT, RESET_N, etc.

Hardware

2.1 Pin DefinitionTable 2-1 Pin Description

No.	Pin	I/O	Description
1	GND	—	Ground
2	ANT_IN	I	GNSS antenna signal input
3	GND	—	Ground
4	ANT_DETECT	I	Antenna signal detection
5	ANT_OFF	O	Disable external LNA
6	ANT_SHORT_N	I	Antenna short circuit detection; active low
7	VCC_RF	O	External LNA power supply
8	SPIS_CSN	I	Chip select pin for SPI slave
9	SPIS_MOSI	I	Master Out / Slave In. This pin is used to receive data in slave mode.
10	SPIS_CLK	I	Clock input pin for SPI slave
11	SPIS_MISO	O	Master In / Slave Out. This pin is used to transmit data in slave mode.
12	GND	—	Ground
13	RSV	—	Reserved
14	GND	—	Ground
15	NC	—	No connection inside
16	NC	—	No connection inside
17	NC	—	No connection inside
18	NC	—	No connection inside
19	PVT_STAT	O	PVT status: active high; Outputs high when positioning and low when not positioning
20	RTK_STAT	O	RTK status: active high; Outputs high for RTK fixed solution and low for other positioning status or no positioning
21	ERR_STAT	O	Error status: active high; Outputs high when failing self-test and low when passing self-test
22	RSV	—	Reserved, recommended to be floating
23	RSV	—	Reserved, recommended to be floating
24	NC	—	No connection inside
25	NC	—	No connection inside
26	RXD2	I	COM2 input, LVTTL
27	TXD2	O	COM2 output, LVTTL
28	BIF	—	Built-in function; recommended to add a through-hole testing point and a 10 kΩ pullup resistor; cannot connect ground or power  supply or input/output data, but can be  floating
29	BIF	—	Built-in function; recommended to add a through-hole testing point and a 10 kΩ pullup resistor; cannot connect ground or power  supply or input/output data, but can be  floating
30	TXD3	O	COM3 output, can be used as CAN TXD, LVTTL
31	RXD3	I	COM3 input, can be used as CAN RXD, LVTTL
32	GND	—	Ground
33	VCC	I	Power supply
34	VCC	I	Power supply
35	RSV	—	Reserved
36	V_BCKP	I	When the main power supply VCC is cut off, V_BCKP supplies power to RTC and relevant register. Level requirement: 2.0 V ~ 3.6 V, and the working current is less than 60 μA at 25 °C. If you do not use the hot start function, connect V_BCKP to VCC. Do NOT connect it to ground or leave it floating.
37	GND	—	Ground
38	NC	—	No connection inside
39	NC	—	No connection inside
40	NC	—	No connection inside
41	GND	—	Ground
42	TXD1	O	COM1 output, LVTTL
43	RXD1	I	COM1 input, LVTTL
44	SDA	I/O	2I C data
45	SCL	I/O	2 I C clock
46	NC	—	No connection inside
47	NC	—	No connection inside
48	GND	—	Ground
49	RESET_N	I	System reset; active Low. The active time should be no less than 5 ms.
50	NC	—	No connection inside
51	EVENT	I	Event mark input, with adjustable frequency and polarity
52	NC	—	No connection inside
53	PPS	O	Pulse per second, with adjustable pulse width and polarity
54	NC	—	No connection inside

2.2 Electrical Specifications
2.2.1 Absolute Maximum Ratings
Table 2-2 Absolute Maximum Ratings

Parameter	Symbol	Min.	Max.	Unit
Power Supply Voltage	VCC	-0.3	3.6	V
Input Voltage	Vin	-0.3	3.6	V
GNSS Antenna Signal Input	ANT_IN	-0.3	6	V
Antenna RF Input Power	ANT_IN input power		+10	dBm
External LNA Power Supply	VCC_RF	-0.3	3.6	V
VCC_RF Output Current	ICC_RF		100	mA
Storage Temperature	Tstg	-55	95	°C

2.2.2 Operating Conditions
Table 2-3 Operating Conditions

Parameter	Symbol	Min.	Typ.	Max.	Unit	Condition
Power Supply Voltage7	VCC	3.0	3.3	3.6	V
Maximum VCC Ripple	Vrpp	0		50	mV
Working Current8	Iopr		145	180	mA	VCC=3.3 V
VCC_RF Output Voltage	VCC_RF		VCC-0.1		V
VCC_RF Output Current	ICC_RF			50	mA
Operating Temperature	Topr	-40		85	°C
Power Consumption	P		480		mW

2.2.3 IO Threshold
Table 2-4 IO Threshold

Parameter	Symbol	Min.	Typ.	Max.	Unit	Condition
Low Level Input Voltage	Vin _ow	0		0.6	V
High Level Input Voltage	Vio_high	VCC x 0.7		VCC + 0.2	V
Low Level Output Voltage	Voutiow	0		0.45	V	lout = 2 mA
High Level Output Voltage	Vout_high	VCC – 0.45		VCC	V	lout = 2 mA

* I 2 C, SPI, CAN: reserved interfaces, not supported currently
6 Not recommended to take VCC_RF as ANT_BIAS to feed the antenna. See section 3.2 for more
7 The voltage range of VCC (3.0 V ~ 3.6 V) has already included the ripple voltage.
8 Since the product has capacitors inside, inrush current occurs during power-on. You should evaluate in the actual environment in order to check the effect of the supply voltage drop caused by inrush current in the system.
2.2.4 Antenna Feature
Table 2-5 Antenna Feature

Parameter  ………………. Symbol	Min.	Typ.	Max.	Unit	Condition
Optimum Input………… Gant	18	30	36	dB

2.3 Dimensions
Table 2-6 Dimensions

Parameter	Min. (mm)	Typ. (mm)	Max. (mm)
A	21.80	22.00	22.50
B	16.80	17.00	17.50
C	2.40	2.60	2.80
D	3.75	3.85	3.95
E	0.95	1.05	1.15
F	1.80	1.90	2.00
G	1.00	1.10	1.20
H	0.70	0.80	0.90
K	1.40	1.50	1.60
M	3.55	3.65	3.75
N	3.15	3.25	3.35
P	2.00	2.10	2.20
R	1.00	1.10	1.20
X	0.72	0.82	0.92

Hardware Design

3.1 Recommended Minimal DesignL1: 68 nH RF inductor in 0603 package is recommended
C1: 100 nF + 100 pF capacitors connected in parallel is recommended
C2: 100 pF capacitor is recommended
C3: N * 10 μF + 1 * 100 nF capacitors connected in parallel is recommended, and the total inductance should be no less than 30 μF
R1: 10 kΩ resistor is recommended
3.2 Antenna Feed Design
UM981 just supports feeding the antenna from the outside of the module rather than from the inside. It is recommended to use devices with high power and that can withstand high voltage. Gas discharge tube, varistor, TVS tube and other high-power protective devices may also be used in the power supply circuit to further protect the module from lightning strike and surge.
If the antenna feed supply ANT_BIAS and the module’s main supply VCC use the same power rail, the ESD, surge and overvoltage from the antenna will have an effect on VCC, which may cause damage to the module. Therefore, it is recommended to design an independent power rail for the ANT_BIAS to reduce the possibility of module damage. Notes:

1. L1: feed inductor, 68 nH RF inductor in 0603 package is recommended
2. C1: decoupling capacitor, recommended to connect two capacitors of 100 nF/100 pF in parallel
3. C2: DC blocking capacitor, recommended 100 pF capacitor
4. It is not recommended to take VCC_RF as ANT_BIAS to feed the antenna (VCC_RF is not optimized for anti-lightning strike, anti-surge and over current protection due to the compact size of the module)
5. D1: ESD diode, choose the ESD protection device that supports high frequency signals (above 2000 MHz)
6. D2: TVS diode, choose a TVS diode with appropriate clamping specification according to the requirement of feed voltage and the antenna withstand voltage

3.3 Power-on and Power-off
VCC

• The VCC initial level when power-on should be less than 0.4 V.
• The VCC ramp when power-on should be monotonic, without plateaus.
• The voltages of undershoot and ringing should be within 5% VCC.
• VCC power-on waveform: The time interval from 10% rising to 90% must be within 100 μs ~1 ms.
• Power-on time interval: The time interval between the power-off (VCC < 0.4 V) to the next power-on must be larger than 500 ms.

V_BCKP

• The V_BCKP initial level when power-on should be less than 0.4 V.
• The V_BCKP ramp when power-on should be monotonic, without plateaus.
• The voltages of undershoot and ringing should be within 5% V_BCKP.
• V_BCKP power-on waveform: The time interval from 10% rising to 90% must be within 100 us ~1 ms.
• Power-on time interval: The time interval between the power-off (V_BCKP < 0.4 V) to the next power-on must be larger than 500 ms.

3.4 Grounding and Heat Dissipation

The 48 pads in the rectangle area are used for grounding and heat dissipation. In the PCB design, the pads should be connected to a large-size ground to strengthen the heat dissipation.
3.5 Recommended PCB Package Design
See the following figure for the recommended PCB package design.Notes:
For the convenience of testing, the soldering pads of the pins are designed long, exceeding the module border much more. For example:

• The pads denoted as detail C are 1.79 mm longer than the module border.
• The pad denoted as detail A is 0.50 mm longer than the module border. It is relatively short as it is an RF pin pad, so we hope the trace on the surface is as short as possible to reduce the impact of external interference on the RF signals.

Production Requirement

Recommended soldering temperature curve is as follows: Temperature Rising Stage

• Rising slope: Max. 3 ° C/s
• Rising temperature range: 50 ° C ~ 150 °C

Preheating Stage

• Preheating time: 60s ~ 120 s
• Preheating temperature range: 150 °C ~ 180 °C

Reflux Stage

• Over melting temperature (217 °C) time: 40s ~ 60 s
• Peak temperature for soldering: no higher than 245 °C

Cooling Stage

• Cooling slope: Max. 4 °C / s
• In order to prevent falling off during soldering of the module, do not solder it on the back of the board during design, and it is not recommended to go through soldering cycle twice.
• The setting of soldering temperature depends on many factors of the factory, such as board type, solder paste type, solder paste thickness etc. Please also refer to the relevant IPC standards and indicators of solder paste.
• Since the lead soldering temperature is relatively low, if using this method, please give priority to other components on the board.
• The opening of the stencil needs to meet your design requirement and comply with the examine standards. The thickness of the stencil is recommended to be 0.15 mm.

Packaging

5.1 Label Description5.2 Product Packaging
The UM981 module uses carrier tape and reel (suitable for mainstream surface mount devices), packaged in vacuum-sealed aluminum foil antistatic bags, with a desiccant inside to prevent moisture. When using reflow soldering process to solder modules, please strictly comply with IPC standard to conduct temperature and humidity control on the modules. As packaging materials such as the carrier tape can only withstand the temperature of 55 degrees Celsius, modules shall be removed from the package during baking.  Note:

1. The cumulative tolerance of 10 side holes should not exceed ± 0.2 mm.
2. Material of the tape: Black antistatic PS (surface impedance 10 5 -10 11 ) (surface static voltage <100 V), thickness: 0.35 mm.
3. Total length of the 13-inch reel package: 6.816 m (Length of the first part of empty packets: 0.408 m, length of packets containing modules: 6 m, length of the last part of empty packets: 0.408 m).
4. Total number of packets in the 13-inch reel package: 284 (Number of the first part of empty packets: 17; actual number of modules in the packets: 250; number of the last part of empty packets: 17).
5. All dimension designs are in accordance with EIA-481-C-2003.
6. The maximum bending degree of the carrier tape within the length of 250 mm should not exceed 1 mm (see the figure below).

Table 5-1 Package Description

Item	Description
Module Number	250 pieces/reel
Reel Size	Tray: 13″ External diameter: 330 ± 2 mm, Internal diameter: 180 ± 2mm, Width: 44.5 ± 0.5 mm Thickness: 2.0 ± 0.2 mm
Carrier Tape	Space between (center-to-center distance): 24 mm

Before surface mounting, make sure that the color of the 30% circle on the HUMIDITY INDICATOR is blue (see Figure 5-4). If the color of the 20% circle is pink and the color of the 30% circle is lavender (see Figure 5-5), you must bake the module until it turns to blue. The UM981 is rated at MSL level 3. Please refer to the IPC/JEDEC J-STD-033 standards for the package and operation requirements. You may also access to the website www.jedec.org to get more information.The shelf life of the UM981 module packaged in vacuum-sealed aluminum foil antistatic bags is one year.

Unicore Communications, Inc.
F3, No.7, Fengxian East Road,
Haidian, Beijing, P.R.China, 100094
www.unicorecomm.com
Phone: 86-10-69939800
Fax: 86-10-69939888
info@unicorecomm.com
www.unicorecomm.com

Documents / Resources

unicore UM981 BDS Multi Frequency RTK INS Integrated Positioning Module [pdf] Instruction Manual UM981 BDS Multi Frequency RTK INS Integrated Positioning Module, UM981, BDS Multi Frequency RTK INS Integrated Positioning Module, RTK INS Integrated Positioning Module, Integrated Positioning Module, Positioning Module

References

• User Manual