ON Semiconductor AND9670/D User manual

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APPLICATION NOTE
©Semiconductor Components Industries, LLC, 2017
March, 2018 −Rev. 1
1Publication Order Number:
AND9670/D
AND9670/D
IoT Development Kit (IDK)
IDKSmartPassiveSensor_
RFID Shield
Quick Start Guide: Bring Up Test of
SPS_RFID Shield
INTRODUCTION
This document describes how to use the RFID shield on the IDK
Baseboard and shows the good reading range performance of the
RFID shield with the attached helical whip antenna
Software and Hardware Preparation
Software Requirement:
Windows PC with minimum 1 USB port, installed Java JRE/JDK
v.8u101 or higher, Operation system Windows 7, 8 or 10, mini USB
cable, Installed IDK IDE v3.6.5 or higher
Hardware Requirement:
•IDK Baseboard with Power connection cable (IoT Baseboard to the
RFID shield)
•DC Power Supply Adapter, Recommended SMI24−12−V−P6
RFID shield kit is provided with:
•RFID Shield
•1/4Wave Whip Antenna for ETSI 866MHz
•Header 1x 10; 2x 8;1x
•Smart Passive Sensor™(SPS) Tag Samples
Figure 1. RFID Shield Mounted on the IDK Baseboard
RESET button

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Procedure:
1. Mount the header and the antenna provided with the SPS_RFID shield kit on the SPS_RFID shield header connector
and on the SMA antenna connector respectively
2. Mount the SPS_RFID shield onto Baseboard over the Arduino header connector
3. Connect the power cabling between the IDK Baseboard and the SPS_RFID shield. Connect mini−USB cable with the
IDK Baseboard and computer
4. Connect power supply adapter or any other supporting output voltage (7−12 V) to the IDK Baseboard and ensure that
the two green LED are on as shown in the left picture in Figure 1
Smart Passive Sensor
ON Semiconductor’s Smart Passive Sensors (SPS) are UHF RFUD wireless sensors that allow the passive sensing of fluid
level, temperature and mosisture values from the respective tags. The tag digitizes sensed information which can be read by
a standard UHF RFID Gen 2 compliant reader. The sensor IC of the SPS, powered by the UHF reader, utilizes the patented
self−tunning Chameleon engine which optimizes the detunned antenna condition by internal variable capacitance. The sensor
IC has the ability to measure the amount of RF power received referred to as On−Chip RSSI and sends this information to the
reader as a digital value.
The detailed information of each Smart Passive Sensors can be found in the respective datasheets which can be downloaded
in the ON Semiconductor’s homepage [1].
The following table shows the overview of the SPS family with the operating frequency in UHF band and sensing
functionaitly respectively.
Table 1. OVERVIEW OF SMART PASSIVE SENSOR FAMILY
Product (old = new Partnumber) Feature UHF Band
SPS1M002A = SPS1M002PET Moisture FCC (902–928 MHz)
SPS1M002B = SPS2M002PET Moisture ETSI (860–880 MHz)
SPS2T001A = SPS1T001PET Temperature FCC (902–928 MHz)
SPS2T001B = SPS2T001PET Temperature ETSI (860–880 MHz)
SPS1M003A = SPS1M003PET Fluid Level FCC (902–928 MHz)
SPS1M003B = SPS2M003PET Fluid Level ETSI (860–880 MHz)
Partnumber Nomenclature: SPSxYzzzVVV
•SPS = Smart Passive Sensor
•X= Region, 1 = FCC, 2 = ETSI
•Y = Sensing Function
•zzz = unique iterative number
•VVV = Form Factor: FOM = Foam; PET = flexible PET; PCB =
Printed Circuit Board; CRM = Ceramic Substrate

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UHF RFID Band
EPC Gen 2 RFID tags work in the frequency band from 869 MHz to 950 MHz which covers the main frequency sub−bands
used in different geographical regions. The IDK RFID sample program implemented 4 sub−bands covering 4 regions
•Europe, India, Middle East, Africa: 865−868 MHz
•US, South America and some regions of Asia: 902−928 MHz
•Japan: 950–956 MHz
•China: 920.5−924.5 MHz
The UHF RFID sub−bands is implemented in the IDK RFID sample program as following:
const char* getRfidFreqBandName(const FreqBandEnum band)
{
switch (band)
{
case FCC: return “FCC”;
case ETSI: return “ETSI”;
case PRC: return “PRC”;
case JAPAN: return “JAPAN”;
case FCC_center: return “FCC_center”;
case ETSI_center: return “ETSI_center”;
default: return “UNKNOWN”;
}
}
And can be set with the API
if (initializeRfid(ETSI) < 0)
The attached whip antenna is optimized to cover the ETSI UFH band. Covering all UHF RFID sub−bands above, the LHCP
antenna [5] is recommended.
GETTING STARTED
•Open the IDK SW by clicking onto IDK icon in start menu or via IDK reference icon on your desktop
Figure 2.
•When the IDK environment is opened, click with left mouse button on Examples ³Simple and select the simple
example RFID to run a simple application

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•Code structure of the example appears on left window under Project Explorer, named AS3993_RFID. It usually
happens there is a small red cross visible close to the name of the project. This is due to indexing that has to be
rebuilt. In order to remove the red cross, right click on the AS3993_RFID, go to Index and left click on Rebuild. It
disappears after few seconds.
Figure 3. IDE
•Go to Device Manager and identify the USB Port number. In this example COM3 was recognized and the value in
file “config.cfg” was modified with the COM3. Save the modified file
Figure 4. USB Port Configuration
•Left click on the project AS3993_RFID to highlight the selected project and press the ON icon in the menu bar as
depicted in the Figure 5 below. A console window opens with the prompt to reset the board and starts the time
count−down immediately

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Figure 5.
•Once the RESET button on the IoT Baseboard is pushed, the flash programming starts as illustrated in the console
window below
Figure 6.
Now you can start to run the RFID application in the console window by adding a sample tag near the antenna and pressing
the RESET button on the IDK Baseboard.
The example below shows the RFID reading process of three sample tags: 2 temperature and one moisture tag identified by
the RFID Reader.
Figure 7.

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RFID READER READING RANGE AREA
The maximum distance or the reading area of the RFID shield to the tag position depends on the reader antenna type and
the tag orientation itself regards to the reader antenna position. Due to different environment conditions, like the reflection of
the nearby objects causing multipath interference as well as influence of the human body holding the tag in the proximity of
the reader antenna, the maximum read range can vary and cannot be precisely predicted in advance.
The following chapter illustrates the different RFID reader range areas based on the evaluation results in an ordinary
environment.
The IDK RFID shield kit is provided with the helical whip antenna [3] with the omni−directional radiation pattern
characteristics.
The whip antenna is mounted on the left corner edge of the RFID shield as shown in the picture below which effects the
radiation pattern directivity due to the ground plane of the RFID shield itself.
Within the optimum reader reading range, up to 10 SPS tags can be detected as shown below.
Figure 8. Reading of 10 SPS Tags Simultaneously
The commonly used mounting position of the whip antenna are in horizontal and vertical plane with regard to the ground
plane.
In H−plane position, the antenna is mounted with the pointing position parallel to the earth ground floor as shown in the
Figure 8.

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The second generally used antenna mounting position is in vertical plane, in following referred as V−plane, whereby the whip
antenna is pointing to the ceiling and perpendicular to the shield and ground plane. To mount the whip antenna vertically on
the RFID shield, an additional right angle adaptor [4] has been used as shown in picture below.
Figure 9. Whip Antenna in Vertical Mounting Position
To get flexible antenna position, a RF coaxial cable can be used to connect the antenna far away from the RFID shield, for
example a RF cable length of 1 m with the attenuation of about ~ 0.5 dB in UHF range can be used without a significant RF
power degradation.

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RFID Reader Antenna in H−Plane
The Figure 10 illustrates the RFID shield reading area with the attached whip antenna and measured in an ordinary
environment. The baseboard with the RFID shield is placed on the desk with the hight of table to ground about 78 cm and the
tag is placed in the horizontal polarized position whereby the height of antenna to the tag at reference position is 7 cm.
At the reference position, the RSSI is about 30. The tag is moved to the different position on the same place to characterize
the tag reading area. In this measurement setup, the optimum reading position is right side of the RFID shield where the
maximum reading distance up to 60 cm has been achieved. The second readng area in red with an omni−directional radiation
characteristics can be observed when the tag is in the vertical position to the earth ground plane.
Figure 10. Top View of Tag Reading Area in H−Plane Position

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RFID Reader Antenna in V−Plane
The picture below shows the optimum tag reading area with the vertical mounted whip antenna.
The first blue area the tag is positioned in the horizontal plane that means orthogonal to the vertical mounted whip antenne,
the second reading area in red, the tag is in the vertical position as the mounted whip antenna.
In this setup, the max reading distance of the tag is about 60 cm in x−axis direction.
The blue reading area shows similar shape as in the horizontal mounted whip antenna above while the tag in the vertical
position shows omni−directional shape. The tag position in the y−axis with max 42 cm is better than x−axis direction.
Figure 11. Top View of Tag Reading Area in V−Plane Position
z
y
x

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Left Hand Circular Polarized Antenna
The following tag reading measurement is performed with the antenna[5] provided with the SensorRFA−GEVB[2].
The reading distance about 135 cm can be achieved, in front of the antenna with the tag in the horizontal plane as shown in
the picture below. The blue reading area as referenec shows the max distance with the whip antenna about 60 cm.
Figure 12. Reading Distance with Circular Antenna vs. Whip Antenna
Optimum reader range area and maximum reading distance can be selected depending on the application with the reader
antenna type and tag position/orientation respectively. If the tag position is mostly in front of the antenna and higher reading
distance is required, the circular polarized antenna[5] can be used but at the expense of higher price and size. But even with
a small sized and cheap whip antenna [3], a decent reading performance can be achieved if the position and orientation for both
antenna and tag are selected carefully.
AUTOPOWER AND TX ATTENUATOR
After successuful reading of the SPS tag, the console window output following data e.g. for temperature sensor:
Found Tag (type = TEMP, label = 55c97, temp = 23.8, rssi = 13, tx_att = 6)
whereby
•Label = Last 5 hex digits of tag Tag Identification Data (TID)
•Temp = Temperature of the tag
•RSSI = Received Signal Strenght Indicator (RSSI) value from 0−31 whereby 0 ist the weakest and 31 is the strongest
signal
•TX Attenuator used for the reading the tag and can be set from 0 to 19 wherby the value 0 dB is set with highest RF
power and 19 dB results in the lowest RF power
The loaded sample program is using the pre−compiled library instanced with AS3993_RFID rfid in the main.c file.
In order to be able to change the TX attenuator or switch on/off the Autopower parameter within the AS3993_RFID library,
following steps are recommended to import the library into the workspace:

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•Go to the IDK installation path, in this example the IDK installation directory is C:\OnSemiconductor
•Go to the folder C:\OnSemiconductor\samples\AS3993_RFID and copy two files AS3993_RFID.cpp and
AS3993_RFID.h into your working directory within the workspace and rename the files in order not to confuse with
the pre−compiled library, in this example renamed to: myAS3993_RFID.cpp and myAS3993_RFID.h
•Press within the IDE F5 button to make the copied files visible
•Now the project explorer window lists the copied file, double click on the file myAS3993_RFID.cpp and press
Ctrl−F
•In the find/replace window enter AS3993_RFID in the “find” field and myAS3993_RFID in the “replace” field as
shown in the Figure below and press “Replace All” button
Figure 13. AS3993 class
•Do the same steps for the files AS3993_RFI.h;main.cpp; Shield.h;header.h
•Rebuild the project AS3993_RFID again
Now you can modify the parameter like TX attenuation and Autopower on/off in the myAS3993_RFID library.
By default, the TX attenuation is set to 6 and Autopower = off
To change the TX Attenuator value go to myAS3993_RFID.h and set the values of your interest and rebuild, in the example
below TX Attenuator value is 6 dB
#define TEMP_MIN_TX_ATTENUATION 6
#define MOIST_MIN_TX_ATTENUATION 6
The Autopower functionality can be switched on or off in the myAS3993_RFID.cpp file with the parameter
“tempAutopower”. Press Ctrl−F and type tempAutopower in the file myAS3993_RFID.cpp and set the value of the
tempAutoPower to “true” if you want to switch on the Autopower parameter and rebuild the project.
Int mzAS3993_RFID: :measureTempTags()
{
TempAutoPower = true; //false by default;
Do the same modification for the member function myAS3993_RFID::measureMoistTags() in the same file.
If Autopower is switched on, the TX attenuation value will be varied automatically from set value to max 19 dB according to
the strength of the reflected signal from the tag.

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RFID SHIELD BOARD TEMPERATURE MEASUREMENT
Measurement Setup:
•RFID Shield Rev2.0 on IDK Baseboard
•FLIR A655sc IR camera with software Flir ResearchIR Max
♦Emissivity = 0.95
♦Refl. Temperature = 24 °C
•HP 34401A Multimeter for Power Supply Current Measurement
•Keithly DC Power Supply to Baseboard
•RFID Tags : 2x Temperature Tag(SPS2T001B) + 1x Moisture Tag(SPS1M002B)
•RFID Operation Frequency: ETSI (860–880 MHz)
Table 2.
Measurement Condition Max RF Output Power
Supply Voltage 12 V
Average Supply Current 295 mA
Peak Supply Current 598 mA
Max Temp at PA 55.8 °C
Max Temp at LDO 38.9 °C
Max Temp at U10: MMIC Amplifier 44.3 °C
Max Temp at U6: LDO 44.4 °C
Max Temp at U7: LDO 45 °C
Max Temp at L6.7: RF inductor 44.6 °C
Figure 14.

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REFERENCES
[1] www.onsemi.com
[2] EVBUM2508−D.PDF
[3] ant−868−cw−rh.pdf
[4] Linx Conssma010
[5] ATLAS_MTI_MT−242025_TRH_A_RHCP_Outdoor_RFID_Antenna_865−956_MHz; Part Number:
MT−242025/NRH
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