Ublox NORA-W2 Series Quick setup guide

UBX-22005177 - R01
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NORA-W2 series
Stand-alone multiradio modules
Hardware integration manual
Abstract
Targeted towards hardware and software application engineers, this document describes how to
integrate NORA-W2 modules in application products and explains the hardware design-in, software,
component handling, regulatory compliance, and testing of the modules. It also lists the external
antennas approved for use with the module. NORA‑W2 modules come with pre-flashed application
software, 802.11b/g/n Wi-Fi, and Bluetooth Low Energy 5 connectivity with support for several
important embedded security features like secure boot. The modules are ideal for critical IoT
applications where security is important.

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Document information
Title
NORA-W2 series
Subtitle
Stand-alone multiradio modules
Document type
Hardware integration manual
Document number
UBX-22005177
Revision and date
R01
23-May-2023
Disclosure restriction
C1 –Public
Product status
Corresponding content status
Functional sample
Draft
For functional testing. Revised and supplementary data will be published later.
In development /
Prototype
Objective specification
Target values. Revised and supplementary data will be published later.
Engineering sample
Advance information
Data based on early testing. Revised and supplementary data will be published later.
Initial production
Early production information
Data from product verification. Revised and supplementary data may be published later.
Mass production /
End of life
Production information
Document contains the final product specification.
This document applies to the following products:
Product name
Ordering code
Type number
FW version
IN/PCN
Product status
NORA-W251AWS
NORA-W251AWS-00B
NORA-W251AWS-00B-00
1.1
N/A
Initial Production
NORA-W256AWS
NORA-W256AWS-00B
NORA-W256AWS-00B-00
1.1
N/A
Initial Production
For information about the related hardware, software, and status of listed product types, see the
NORA-W2 data sheet [2].
u-blox or third parties may hold intellectual property rights in the products, names, logos, and designs included in this
document. Copying, reproduction, or modification of this document or any part thereof is only permitted with the express
written permission of u-blox. Disclosure to third parties is permitted for clearly public documents only.
The information contained herein is provided “as is” and u-blox assumes no liability for its use. No warranty, either express or
implied, is given, including but not limited to, with respect to the accuracy, correctness, reliability, and fitness for a particular
purpose of the information. This document may be revised by u-blox at any time without notice. For the most recent
documents, visit www.u blox.com.
Copyright © u-blox AG.

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Contents
Document information .............................................................................................................................2
Contents .......................................................................................................................................................3
1Product overview.................................................................................................................................6
1.1 Module architecture ...................................................................................................................................6
1.2 Block diagram ..............................................................................................................................................7
2Module integration .............................................................................................................................8
2.1 Power supply ................................................................................................................................................8
2.1.1 Module supply input (VCC) ...............................................................................................................9
2.1.2 Digital I/O interfaces reference voltage (VCC_IO)........................................................................9
2.1.3 VCC application circuits....................................................................................................................9
2.2 CPU.................................................................................................................................................................9
2.3 System functions......................................................................................................................................10
2.3.1 Power modes .....................................................................................................................................10
2.3.2 Module reset......................................................................................................................................10
2.4 Antenna integration .................................................................................................................................10
2.4.1 Antenna solutions ............................................................................................................................10
2.4.2 Approved antenna designs.............................................................................................................11
2.5 Data interfaces..........................................................................................................................................12
2.5.1 Universal asynchronous serial interface (UART) .......................................................................12
2.6 Module control...........................................................................................................................................12
2.7 Other remarks............................................................................................................................................12
2.7.1 No-Connect pins (NC) ......................................................................................................................12
2.7.2 GND pins.............................................................................................................................................12
3Design-in............................................................................................................................................. 13
3.1 Overview......................................................................................................................................................13
3.2 RF interface................................................................................................................................................13
3.2.1 Antenna integration.........................................................................................................................13
3.2.2 RF transmission line design ...........................................................................................................15
3.2.3 NORA-W251AWS.............................................................................................................................17
3.2.4 NORA-W256AWS.............................................................................................................................19
3.3.1 Considerations for schematic design and PCB floor-planning ...............................................21
3.3.2 Component placement....................................................................................................................21
3.3.3 Layout and manufacturing.............................................................................................................21
3.4 Module footprint and paste mask.........................................................................................................22
3.5 Thermal guidelines ...................................................................................................................................22
3.6 ESD guidelines...........................................................................................................................................24
3.7 Design-in checklists .................................................................................................................................25
3.7.1 Schematic checklist.........................................................................................................................25
3.7.2 Layout checklist................................................................................................................................25
4AWS IoT ExpressLink...................................................................................................................... 26

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4.1 AWS IoT ExpressLink programmer's guide.........................................................................................26
4.2 AWS-specific AT commands for u-blox module ................................................................................26
4.2.1 AT+DIAG SCAN [time_out_in_seconds].......................................................................................26
4.2.2 AT+DIAG CONNECT.........................................................................................................................26
4.2.3 AT+DIAG IPCONFIG..........................................................................................................................26
4.2.4 AT+DIAG PING <host>.....................................................................................................................27
4.3 Device claiming..........................................................................................................................................27
4.4 Updating NORA-W2 firmware................................................................................................................27
4.4.1 Updating firmware over UART.......................................................................................................27
4.4.2 Updating firmware Over the Air (OTA).........................................................................................28
4.5 Bluetooth Low Energy device provisioning ..........................................................................................28
4.5.1 Connect to the device ......................................................................................................................29
4.5.2 Scan for available networks............................................................................................................29
4.5.3 Provision device.................................................................................................................................30
5Handling and soldering................................................................................................................... 32
5.1 ESD handling precautions.......................................................................................................................32
5.2 Packaging, shipping, storage, and moisture preconditioning .........................................................32
5.3 Reflow soldering process.........................................................................................................................33
5.3.1 Cleaning ..............................................................................................................................................34
5.3.2 Other remarks ...................................................................................................................................34
6Regulatory compliance................................................................................................................... 35
6.1 Country approvals.....................................................................................................................................35
6.2 European Union regulatory compliance ...............................................................................................35
6.2.1 Radio Equipment Directive (RED) 2014/53/EU ..........................................................................35
6.2.2 Compliance with the RoHS directive ............................................................................................35
6.2.3 CE End-product regulatory compliance .......................................................................................35
6.3 Great Britain regulatory compliance .....................................................................................................35
6.3.1 UK Conformity Assessed (UKCA)..................................................................................................36
6.4 FCC/ISED compliance ..............................................................................................................................36
6.4.1 FCC compliance statements..........................................................................................................36
6.4.2 Configuration control and software security of end-products ...............................................37
6.4.3 Operating frequencies.....................................................................................................................38
6.4.4 RF exposure statement...................................................................................................................38
6.4.5 End-product user manual instructions........................................................................................39
6.4.6 End-product labeling requirements..............................................................................................39
6.4.7 End-product compliance.................................................................................................................40
6.5 Japan radio equipment compliance......................................................................................................41
6.5.1 Compliance statement....................................................................................................................41
6.5.2 End product labelling requirement................................................................................................41
6.5.3 End product user manual requirement ........................................................................................42
6.6 NCC Taiwan compliance..........................................................................................................................42
6.6.1 Taiwan NCC Warning Statement..................................................................................................42

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6.6.2 Labeling requirements for end product .......................................................................................42
6.7 KCC South Korea compliance.................................................................................................................43
6.8 Brazil compliance ......................................................................................................................................43
6.9 Australia and New Zealand regulatory compliance ...........................................................................44
6.10South Africa regulatory compliance .....................................................................................................44
6.11Safety compliance ....................................................................................................................................44
7Pre-approved antennas list........................................................................................................... 45
7.1 Antenna accessories................................................................................................................................45
7.2 Single band antennas ..............................................................................................................................46
8Product testing................................................................................................................................. 49
8.1 Radio test and compliance......................................................................................................................49
8.2 u-blox in-line production test..................................................................................................................49
8.3 OEM manufacturer production test .....................................................................................................50
8.3.1 “Go/No go” tests for integrated devices ......................................................................................51
Appendix .................................................................................................................................................... 52
AProtobuf examples........................................................................................................................... 52
A.1 Session........................................................................................................................................................52
A.2 Wi-Fi scan message .................................................................................................................................53
A.3 Wi-Fi provisioning messages..................................................................................................................56
BGlossary .............................................................................................................................................. 59
Related documentation......................................................................................................................... 61
Revision history ....................................................................................................................................... 61
Contact....................................................................................................................................................... 61

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1Product overview
The NORA-W2 series of stand-alone, multiradio modules integrate a powerful 32-bit, dual-core
microcontroller unit (MCU) and a radio for wireless communication. The radio supports Wi-Fi
802.11b/g/n in the 2.4 GHz ISM band and Bluetooth Low Energy 5.
The embedded AWS IoT ExpressLink-compliant software includes the required and pre-installed,
security certificates for “out of the box” connectivity with Amazon Web Services (AWS). NORA-W2
modules also support secure over-the air (OTA) updates of both the module firmware and the host
application. Control and data communication with the module is managed using stateless AT-
commands over the serial interface.
The NORA-W2 AWS IoT ExpressLink grants OEM ownership of the end-product when activated using
the AWS Multi Account Registration (MAR) process. Fleet management, monitoring, and security
auditing are supported with AWS IoT Device Management and AWS IoT Device Defender.
The wireless MCU, flash memory, crystal, and other integrated components used for antenna
matching, filtering, and decoupling, make NORA-W2 a compact, stand-alone, multiradio module.
Featuring Secure Boot for protection against malicious access, NORA-W2 runs only in the presence
of authenticated software.
The small size and the embedded security capabilities make NORA-W2 modules ideal for critical IoT
applications, where security is important. Intended applications include consumer products,
telematics, low power sensors, connected factories, connected buildings (appliances and
surveillance), point-of-sales, and health devices.
The NORA-W2 series is globally certified, which reduces time to market for the end-product. To
ensure operation in harsh professional environments, the modules are industrial grade and qualified
according to AEC-Q104, supporting an extended temperature range of –40 °C to +85 °C.
1.1 Module architecture
Integrating the ESP32-S3 MCU, NORA-W2 is the second generation of u-blox modules based on
Espressif Wi-Fi and Bluetooth chipsets. NINA-W1/B2 modules, representing the first generation, are
based on the Espressif ESP32 chip [3]. The simple device design allows developers to use an external
antenna (NORA-W251AWS) or utilize the internal antenna (NORA-W256AWS) in the application
design.
These compact modules include the wireless MCU, flash memory, crystal, and other components for
matching, filtering, antenna, decoupling, and antenna operation.
Model
Description
NORA-W251AWS
Includes an antenna RF pin for use with an external antenna
NORA-W256AWS
Supports an internal PCB trace antenna that is specifically designed for embedded devices
Table 1: Supported configurations of the NORA-W2 module series

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1.2 Block diagram
*Not supported by current software
Figure 1: NORA-W2 series block diagram
Linear voltage regulators
RF
Wi-Fi
baseband
Bluetooth LE
Baseband
IO buffers
Xtensa Dual-core 32-bit LX7 MCU
SRAM
(512 kB)
Cryptographic
hardware
accelerators
PLL
VCC_IO
VCC (3.0- 3.6V)
40 MHz
Reset
UART
USB*
I2C*
SPI*
QPI*
Quad/Octal SPI*
JTAG*
GPIO
(WAKEEVENT
ADC*
Flash
(8MB)
OPI*
LPO*
EFuse
ROM
(384 kB)
PCB trace antenna
(NORA-W256AWS)
ANT pad
(NORA-W251AWS)
NORA-W2
ESP32-S3

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2Module integration
NORA-W2 must be integrated together with a host CPU system, as shown in Figure .
Figure 3: NORA-W2 integration in host system
NORA-W2 series modules come with the pre-flashed application software, supporting IEEE 802.11
b/g/n single-band 2.4 GHz operation. The host system can set up and control the module through the
UART interface.
☞UART is the only data interface available for establishing connection with AWS and host CPU.
Control signals for reset, interrupt, and module wake up are used to control NORA-W2 from host CPU.
The power supply is sourced from the VCC and VIO pins.
If external antennas are needed, NORA-W251 supports U.FL connector pads for RF connection.
NORA-W251, with U.FL connectors is especially useful if the application product is hosted in a metal
enclosure and external antennas must be used.
NORA-W256 has an integrated antenna and is suitable for products mounted in a plastic housing.
For correct operation, it is important to implement the appropriate configuration settings and correct
start-up sequence, as described in the NORA-W2 data sheet [2]. This puts requirements on the
enabling of power sources and on the timing and assertion of PDn.
☞For pin-out and pin assignment information, see the NORA-W2 series data sheet [2].
2.1 Power supply
The power for NORA-W2 series modules is supplied through VCC and VCC_IO pins by DC voltage.

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⚠The system power supply circuit must be able to support peak power. The current drawn from VCC
and VCC_IO can vary significantly based on Wi-Fi power consumption profiles.
2.1.1 Module supply input (VCC)
NORA-W2 series modules use an integrated Linear Voltage converter to transform and stabilize the
supply voltage applied to the VCC pin.
2.1.2 Digital I/O interfaces reference voltage (VCC_IO)
All NORA-W2 series modules support an additional supply input for setting the I/O voltage level.
A separate VCC_IO pin allows integration of the module into applications with different voltage levels.
NORA-W2 modules support a 3.3 V IO voltage level only.
2.1.3 VCC application circuits
The power for NORA-W2 series modules is applied through the VCC pins. These supplies are taken
from either of the following sources:
•Switching Mode Power Supply (SMPS)
•Low Drop Out (LDO) regulator
An SMPS is the ideal design choice when the available primary supply source is of a higher value than
the operating supply voltage of the module. This offers the best power efficiency for the application
design and minimizes the amount of current drawn from the main supply source.
⚠When taking VCC supplies from an SMPS make sure that the AC ripple voltage is kept as low as
possible at the switching frequency. Design layouts should focus on minimizing the impact of any
high-frequency ringing.
Use an LDO linear regulator for primary VCC supplies that have a relatively low voltage. As LDO linear
regulators dissipate a considerable amount of energy, LDOs are not recommended for the step down
of high voltages.
DC/DC efficiency should be regarded as a trade-off between the active and idle duty cycles of an
application. Although some DC/DC devices achieve high efficiency at light loads, these efficiencies
typically degrade as soon as the idle current drops below a few milliamps. This can have a negative
impact on the life of the battery.
If decoupling capacitors are needed on the supply rails, it is best practice to position these as close as
possible to the NORA-W2 series module. The power routing of some host system designs makes
decoupling capacitance unnecessary.
For electrical specifications, see the appropriate NORA-W2 series data sheet [2].
2.2 CPU
NORA-W2 series modules have a dual-core system with two Harvard Architecture Xtensa LX7 CPUs
operating at a maximum 240 MHz internal clock frequency.
The main features of the internal NORA-W2 memory include:
•384 Kbyte ROM for booting and core functions
•512 Kbyte SRAM for data and instruction
•8 Mbyte FLASH for code storage, including hardware encryption to protect programs.
•4 kbit EFUSE (non-erasable memory) for MAC addresses, module configuration, flash encryption,
and chip ID

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NORA-W2 series modules can be used to design solutions with top-grade security. Including
integrated cryptographic hardware accelerators, NORA-W2 modules feature secure boot
functionality that ensures that they can only be restarted with authenticated software.
2.3 System functions
2.3.1 Power modes
NORA-W2 series modules are power efficient devices capable of operating in power saving mode. The
following system power modes are available:
•Standby state –stops Wi-Fi until the EXPRESSLINK_WAKE pin is asserted, the time has elapsed,
or activity on AT UART port is detected.
•Light sleep –reduces the supply voltage of the digital peripherals, most of the RAM and CPU, and
keeps them clock-gated. The device wakes up on optional timeout, EXPRESSLINK_WAKE pin, or
UART input.
•Deep sleep –powers off all digital peripherals, most of the RAM and CPU, and changes the clock
sources of these parts to the clock, APB_CLK. The device wakes up on optional timeout or
EXPRESSLINK_WAKE pin.
•Idle - No power savings. Device will wake up on optional timeout, EXPRESSLINK_WAKE pin or
UART input.
Toggling the EXPRESSLINK_WAKE pin on NORA-W2 module when module is in light sleep or deep
sleep or idle mode, allows the module to enter active wake mode.
2.3.2 Module reset
NORA-W2 series modules can be reset (rebooted) in any of the following ways:
•RESET_N pin. Normally set high by an internal pull-up, a logical low state on this signal low causes
a “reset” of the module. RESET_N should be driven by an open drain, open collector, or contact
switch.
•EXPRESSLINK_RST. Similar reset on NORA-W2 modules can be asserted using software AT
command.
2.4 Antenna integration
Antenna interfaces are different for each module variant in the NORA-W2 series. The modules
support either an internal antenna (NORA-W256AWS) or external/integrated antennas connected
through a dedicated antenna pin (NORA-W251AWS).
2.4.1 Antenna solutions
NORA-W2 series modules support three different antenna solutions:
•NORA-W251AWS has an antenna pin that can be used with either the integrated SMD chip
antenna or external antenna.
•NORA-W256AWS includes an internal PCB trace antenna which is specifically designed and
optimized for the NORA-W2 module. There is no need for an RF trace design on the host PCB which
means less effort is required in the test lab.

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Figure 2 summarizes each of the available antenna options.
Figure 2: Antenna options
2.4.2 Approved antenna designs
NORA-W2 modules come with a pre-certified design that can be used to save costs and time during
the certification process. To leverage this benefit, customers are required to implement an antenna
layout that is fully compliant with the u-blox reference design outlined in this document. Reference
design source files are available from u-blox on request.
1
The designer integrating a u-blox reference design into an end-product is solely responsible for any
unintentional emission levels produced by the end product.
For Bluetooth and Wi-Fi operation, NORA-W2 modules have been tested and approved for use with
the antennas featured in the listed in the Pre-approved antennas list.
⚠To avoid invalidating the compliance and pre-certification of u-blox modules with the various
regulatory bodies, use only external antennas included on the Pre-approved antennas list .
Reference design source files are available from u-blox on request.
The module may be integrated with other antennas. In which case, the OEM installer must certify the
design with respective regulatory agencies.
1
Reference design files to be made available only after certification

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2.5 Data interfaces
2.5.1 Universal asynchronous serial interface (UART)
NORA-W2 series modules support a UART interface for communication with an application host
processor (AT commands, data communication, and software upgrades).
The following UART signals are available:
•Data lines (EXPRESSLINK_RXD as input, EXPRESSLINK_TXD as output)
•Frame format configuration:
o8 data bits
oEven or no-parity bit
o1 stop bit
o115200 bits/s baud rate
•Default frame configuration is 8N1 means eight (8) data bits, no (N) parity bit, and one (1) stop bit.
☞It is advisable to connect or make available a header for test points, debugging, and radio testing.
See also Radio test and compliance.
☞The IO level of the UART follows VCC_IO.
2.6 Module control
NORA-W2 series modules provide wake-up and event signals that handle the low-power modes for
both Wi-Fi and Bluetooth. See also Power management.
The wake-up signals are used to exit NORA-W2 or Host CPU from sleep modes. Wake-up signals are
powered by the VIO voltage domain.
Name
I/O
Description
EXPRESSLINK_WAKE
I/O
Host to Module wake-up signal [Pin G2]
EXPRESSLINK_EVENT
I/O
Interrupt signal from Host to Module [Pin G3]
Table 2: Wake-up signal definitions
2.7 Other remarks
2.7.1 No-Connect pins (NC)
NORA-W2 modules have unconnected (NC) pins that are reserved for future use. These pins must be
left unconnected on the application PCB.
2.7.2 GND pins
Good electrical connection of module GND pins, using solid ground layer of the host application board,
is required for correct RF performance. Firm connections provide a thermal heat sink for the module
and significantly reduce EMC issues.

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3Design-in
Follow the design guidelines stated in this chapter to optimize the integration of NORA-W2 series
modules in the final application board.
3.1 Overview
Although all application circuits must be properly designed, there are several points that require
special attention during application design. A list of these points, in order of importance, follows:
•Module antenna connection: ANT Pad
Antenna circuits affect the RF compliance of all applications that include the certification
schemes related to the module. To maintain compliance and subsequent certification of the
application design, it is important to observe the applicable parts of antenna schematic and layout
design described in Antenna interfaces.
•Module supply: VCC, VCC_IO, and GND pins.
Supply circuits can affect the RF performance. It is important to observe the schematic and layout
design for these supplies. See also Supply interfaces.
Modules normally includes several supply pins listed in the module’s Data sheet Pin out list.
•High-speed interfaces: UART pins.
High-speed interfaces are a potential source of radiated noise that can affect the regulatory
compliance standards for radiated emissions. It is important to follow the schematic and layout
design recommendations described in the General high-speed layout guidelines.
•System functions: RESET_N, GPIO and other System input and output pins
Careful utilization of these pins in the application design is required to guarantee for correct boot
up and system operation. Ensure that the voltage level is correctly defined during module boot. It
is important to follow the schematic and layout design recommendations described in the General
high-speed layout guidelines
•Other pins: LED and NC pins.
Careful utilization of these pins is required to guarantee proper functionality. It is important to
follow the schematic and layout design recommendations described in the General high-speed
layout guidelines.
3.2 RF interface
As the unit cannot be mounted arbitrarily, the placement should be chosen with consideration so that
it does not interfere with radio communication. The NORA-W256 module (that includes a PCB trace
antenna) cannot be mounted in a metal enclosure. No metal casing or plastics using metal flakes
should be used. Avoid metallic based paint or lacquer as well. NORA-W251 offers more freedom as
an external antenna can be mounted further away from the module.
⚠According to the FCC regulations, the transmission line from the module antenna pin to the
antenna or antenna connector on the host PCB is considered part of the approved antenna design.
Therefore, module integrators must either follow exactly one of the antenna reference designs
used in the module’s FCC type approval or certify their own designs.
3.2.1 Antenna integration
At the start the application design phase, when the mechanical design and the physical dimensions
of the board are still under analysis/decision, the antenna integration shall be considered. Apart from
the product’s performance the compliance and subsequent certification of the RF design depends
heavily on the radiating performance of the antennas.

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To ensure proper performance of the application product carefully follow the guidelines outlined
below. Note also that the RF certification of the module is extended through to the application design.
•External antennas, including, linear monopole classes:
oPlace the module and antenna in any convenient area on the board. External antennas do not
impose any restriction on where the module is placed on the PCB.
oSelect antennas with an optimal radiating performance in the operating bands. The radiation
performance depends mainly on the antennas.
oChoose RF cables that offer minimum insertion loss. Unnecessary insertion loss is introduced
by low quality or long cables. Large insertion losses reduce radiation performance.
oUse a high-quality 50 coaxial connector for proper PCB-to-RF-cable transition.
•Integrated antennas, such as patch-like antennas:
oInternal integrated antennas impose some physical restrictions on the PCB design:
-Integrated antennas excite RF currents on its counterpoise, typically the PCB ground plane
of the device that becomes part of the antenna; its dimension defines the minimum
frequency that can be radiated. Therefore, the ground plane can be reduced to a minimum
size that should not be smaller than a quarter of the wavelength of the minimum frequency
that has to be radiated, given that the orientation of the ground plane related to the
antenna element must be considered.
-Find a numerical example to estimate the physical restrictions on a PCB, where:
Frequency = 2.4 GHz →Wavelength = 12.5 cm →Quarter wavelength = 3.5 cm in free space
or 1.5 cm on a FR4 substrate PCB.
•Choose antennas with optimal radiating performance in the operating bands. Radiation
performance depends on the complete product and antenna system design, including the
mechanical design and usage of the product. Table 3 summarizes the requirements for the
antenna RF interface.
•Make the RF isolation between the system antennas as high as possible, and the correlation
between the 3D radiation patterns of the two antennas as low as possible. In general, RF
separation of at least a quarter wavelength between the two antennas is required to achieve some
isolation and low pattern correlation. If possible, increase the separation to maximize the
performance and fulfill the requirements in Table 4.
Item
Requirements
Remarks
Impedance
50 nominal characteristic
impedance
The impedance of the antenna RF connection must match
the 50 impedance of Antenna pins.
Frequency Range
2400 - 2500 MHz
5150 - 5850 MHz
For 802.11b/g/n/ax and Bluetooth.
For 802.11a/n/ac/ax.
Return Loss
S11 < -10 dB (VSWR < 2:1)
recommended
S11 < -6 dB (VSWR < 3:1) acceptable
The Return loss or the S11, as the VSWR, refers to the
amount of reflected power, measuring how well the primary
antenna RF connection matches the 50 characteristic
impedance of antenna pins.
The impedance of the antenna termination must match as
much as possible the 50 nominal impedance of antenna
pins over the operating frequency range, to maximize the
amount of power transferred to the antenna.
Efficiency
> -1.5 dB ( > 70% ) recommended
> -3.0 dB ( > 50% ) acceptable
Radiation efficiency is the ratio of the radiated power to the
power fed to the antenna input: the efficiency is a measure
of how well an antenna receives or transmits.
Maximum Gain
To comply with regulatory agencies radiation exposure
limits, the maximum antenna gain must not exceed the
value specified in type approval documentation.
Table 3: Summary of antenna interface requirements

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Table 4 specifies additional requirements for implementing a dual antenna design.
Item
Requirements
Remarks
Isolation
(in-band)
S21 > 30 dB recommended
The antenna-to-antenna isolation is the S21 parameter
between the two antennas in the band of operation.
Lower isolation might be acceptable depending on use-
case scenario and performance requirements.
Isolation
(out-of-band)
S21 > 35 dB recommended
S21 > 30 dB acceptable
Out-of-band isolation is evaluated in the band of the
aggressor. This ensures that the transmitting signal from
the other radio is sufficiently attenuated by the receiving
antenna. It also avoids any saturation and intermodulation
effect on the receiver port.
Envelope Correlation
Coefficient (ECC)
ECC < 0.1 recommended
ECC < 0.5 acceptable
The ECC parameter correlates the far field parameters
between antennas in the same system. A low ECC
parameter is fundamental in improving the performance of
MIMO-based systems.
Table 4: Summary of Wi-Fi/Bluetooth coexistence requirements
⚠When operating dual antennas in the same 2.4 GHz band, sufficient isolation is critical for
attaining an optimal throughput performance in Wi-Fi/Bluetooth coexistence mode.
Select antennas that provide:
•Optimal return loss (or VSWR) over all the operating frequencies.
•Optimal efficiency figure over all the operating frequencies.
•An appropriate gain that does not exceed the regulatory limits specified in some regulatory country
authorities like the FCC in the United States.
A useful approach for the antenna micro-strip design is to place a U.FL connector close to the
embedded PCB or chip antenna. The U.FL connector only needs to be mounted on units used for
verification.
3.2.2 RF transmission line design
RF transmission lines, such as those that connect from RF_ANT pins to their related antenna
connectors or antenna, must be designed with a characteristic impedance of 50 .
Figure 3 shows the design options for implementing a transmission line, namely:
•Microstrip –track separated with dielectric material and coupled to a single ground plane.
•Coplanar microstrip –track separated with dielectric material and coupled to both the ground
plane and side conductor. This in the most common transmission line implementation.
•Stripline –track separated by dielectric material and sandwiched between two parallel ground
planes.
The parameters shown in the cross-sectional area of each trace design include:
•Width (W) –shows the width of the copper layer on the top layer
•Distance (S) –shows the distance between the top copper layer and the two adjacent GND planes.
•Dielectric substrate thickness (H) –shows the distance between the GND reference on the bottom
plane and the copper layer on the top layer.
•Thickness of the copper layer (T) –can also be represented by “Base Copper Weight”, which is
commonly used as the parameter for PCB stack-up.
Dielectric constant (εr) defines the ratio between the electric permeability of the material against the
electric permeability of free space
☞The width of a 50 Ω microstrip depends on mainly “εr”and “H”, which must be calculated for each
PCB layer stack-up.

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Figure 3: Transmission line trace design
Follow these recommendations to design a 50 transmission line correctly:
•The designer should provide enough clearance from surrounding traces and ground in the same
layer; in general, a trace to ground clearance of at least two times the trace width should be
considered. The transmission line should also be ‘guarded’ by ground plane area on each side.
•The characteristic impedance can be calculated as first iteration using tools provided by the layout
software. It is advisable to ask the PCB manufacturer to provide the final values that are usually
calculated using dedicated software and available stack-ups from production. It could also be
possible to request an impedance coupon on panel’s side to measure the real impedance of the
traces.
•FR-4 dielectric material, although its high losses at high frequencies can be considered in RF
designs provided that:
oRF trace length must be minimized to reduce dielectric losses.
oIf traces longer than few centimeters are needed, it is recommended to use a coaxial connector
and cable to reduce losses
oStack-up should allow for thick 50 traces and at least 200 µm trace width is recommended
to assure good impedance control over the PCB manufacturing process.
oFR-4 material exhibits poor thickness stability and thus less control of impedance over the
trace length. Contact the PCB manufacturer for specific tolerance of controlled impedance
traces.
•The transmission lines width and spacing to the GND must be uniform and routed as smoothly as
possible: route RF lines in 45 °C angle or in arcs.
•Add GND stitching vias around transmission lines.
•Ensure solid metal connection of the adjacent metal layer on the PCB stack-up to main ground
layer, providing enough vias on the adjacent metal layer.
•Route RF transmission lines far from any noise source (as switching supplies and digital lines) and
from any sensitive circuit to avoid crosstalk between RF traces and Hi-impedance or analog
signals.
•Avoid stubs on the transmission lines, any component on the transmission line should be placed
with the connected pad over the trace. Also avoid any unnecessary component on RF traces.

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Figure 4: Example of RF trace and ground design from NORA-W2 Evaluation Kit (EVK)
3.2.3 NORA-W251AWS
NORA-W251AWS is suited for designs when an external antenna is needed due to mechanical
integration or placement of the module.
Designers must take care of the antennas from all perspective at the beginning of the design phase
when the physical dimensions of the application board are under analysis/decision, as the RF
compliance of the device integrating NORA-W251AWS module with all the applicable required
certification schemes heavily depends on the radiating performance of the antennas. The designer is
encouraged to consider one of the u-blox suggested antenna part numbers and follow the layout
requirements.
3.2.3.1 RF connector design
If an external antenna is required, the designer should consider using a proper RF connector. It is the
responsibility of the designer to verify the compatibility between plugs and receptacles used in the
design.
Table 5 suggests several RF connector plugs that can be used by the designers to connect RF coaxial
cables based on the declaration of the respective manufacturers. The Hirose U.FL-R-SMT RF
receptacles (or similar parts) require a suitable mated RF plug from the same connector series. Due
to wide usage of this connector, several manufacturers offer compatible equivalents.
Manufacturer
Series
Remarks
Hirose
U.FL® Ultra Small Surface Mount Coaxial Connector
Recommended
I-PEX
MHF® Micro Coaxial Connector
Tyco
UMCC® Ultra-Miniature Coax Connector
Amphenol RF
AMC® Amphenol Micro Coaxial
Lighthorse Technologies, Inc.
IPX ultra micro-miniature RF connector
Table 5: U.FL compatible plug connector

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Typically, the RF plug is available as a cable assembly. Different types of cable assembly are available;
the user should select the cable assembly best suited to the application. The key characteristics are:
•RF plug type: select U.FL or equivalent
•Nominal impedance: 50 
•Cable thickness: Typically, from 0.8 mm to 1.37 mm. Select thicker cables to minimize insertion
loss.
•Cable length: Standard length is typically 100 mm or 200 mm; custom lengths may be available on
request. Select shorter cables to minimize insertion loss.
•RF connector on the other side of the cable: For example, another U.FL. (for board-to-board
connection) or SMA (for panel mounting)
Consider that SMT connectors are typically rated for a limited number of insertion cycles.
Additionally, the RF coaxial cable may be relatively fragile compared to other types of cables. To
increase application ruggedness, connect U.FL connector to a more robust connector such as SMA
fixed on panel.
Figure 5: U.FL connector layout, top layer to the left and inner layer 1 to the right
☞A de-facto standard for SMA connectors implies the usage of reverse polarity connectors
(RP-SMA) on Wi-Fi and Bluetooth®end products to increase the difficulty for the end user to
replace the antenna with higher gain versions and exceed regulatory limits.
The following recommendations apply for proper layout of the connector:
•Strictly follow the connector manufacturer’s recommended layout:
oSMA Pin-Through-Hole connectors require GND keep-out (that is, clearance, a void area) on all
the layers around the central pin up to annular pads of the four GND posts.
oU.FL. surface mounted connectors require no conductive traces (that is, clearance, a void area)
in the area below the connector between the GND land pads.
If the connector’s RF pad size is wider than the micro strip, remove the GND layer beneath the RF
connector to minimize the stray capacitance thus keeping the RF line 50 Ω. For example, the active
pad of the U.FL. connector must have a GND keep-out (that is, clearance, a void area) at least on the
first inner layer to reduce parasitic capacitance to ground.
3.2.3.2 Integrated antenna design
If integrated antennas are used, the transmission line is terminated by the integrated antennas
themselves. Follow the guidelines mentioned below:
•The antenna design process should begin at the start of the whole product design process. Self-
made PCBs and antenna assembly are useful in estimating overall efficiency and radiation path of
the intended design.
•Use antennas designed by an antenna manufacturer providing the best possible return loss (or
VSWR).
•Provide a ground plane large enough according to the related integrated antenna requirements.
The ground plane of the application PCB may be reduced to a minimum size that must be similar
to one quarter of wavelength of the minimum frequency that has to be radiated; however overall
antenna efficiency may benefit from larger ground planes.

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•Proper placement of the antenna and its surroundings is also critical for antenna performance.
Avoid placing the antenna close to conductive or RF-absorbing parts such as metal objects, ferrite
sheets and so on as they may absorb part of the radiated power or shift the resonant frequency of
the antenna or affect the antenna radiation pattern.
•It is highly recommended to strictly follow the detailed and specific guidelines provided by the
antenna manufacturer regarding correct installation and deployment of the antenna system,
including PCB layout and matching circuitry.
•Further to the custom PCB and product restrictions, antennas may require tuning/matching to
comply with all the applicable required certification schemes. It is recommended that you plan
measurement and validation activities with the antenna manufacturer before releasing the end-
product to manufacturing.
•RF section may be affected by noise sources like hi-speed digital buses. Avoid placing the antenna
close to buses such as DDR or consider taking specific countermeasures like metal shields or
ferrite sheets to reduce the interference.
⚠Take care of the interaction between co-located RF systems like LTE sidebands on 2.4 GHz band.
Transmitted power may interact or disturb the performance of NORA-W2 series modules.
3.2.4 NORA-W256AWS
If a plastic enclosure is used, it is possible to use NORA-W256AWS with the embedded antenna. To
reach optimum operating performance, follow the instructions in this section.
3.2.4.1 Internal or PCB trace antenna
•The module shall be placed in the center of an edge of the host PCB.
•A large ground plane on the host PCB is a prerequisite for good antenna performance. It is
recommended to have the ground plane extending at least 10 mm on the three non-edge sides of
the module. See also Figure 6.
•The host PCB shall include a full GND plane underneath the entire module, with a ground cut out
under the PCB trace antenna according to the description in Figure 7.
•The NORA-W256AWS has six extra GND pads under the antenna that need to be connected for a
good antenna performance. Detailed measurements of the footprint including this extra GND
pads can be found in the NORA-W2 series data sheet [2].
•High / large parts including metal shall not be placed closer than 10 mm to the module’s antenna.
•At least 10 mm clearance between the antenna and the casing is recommended. If the clearance
is less than 10 mm, the antenna performance can be adversely affected.
•The module shall be placed such that the antenna faces outwards from the product and is not
obstructed by any external items in close vicinity of the products intended use case.

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Figure 6: GND plane guard area enclosing the NORA-W256AWS module
Figure 7: Size of the GND cut out for the PCB trace antenna on NORA-W256AWS