Getac Technology ZX70U UHF RFID reader User Manual Module

Getac Technology Corporation UHF RFID reader Module

Contents

User Manual Module

www.ams.com
Revision 1.0 / 2012/06/26
Application Note: UHF RFID Fermi Reader
HW
-Description
AS3993
UHF RFID Single Chip Reader EPC
Class1 Gen2 Compatible
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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Table of Contents
1. Introduction .......................................................................................................................... 2
2. Key Features ....................................................................................................................... 3
3. Applications ......................................................................................................................... 4
4. Reader System Description .................................................................................................. 5
5 Interfaces ............................................................................................................................. 7
6 Reader Part ....................................................................................................................... 10
7 Controller Part .................................................................................................................... 16
Copyright .................................................................................................................................. 17
Disclaimer ................................................................................................................................. 17
Figure 1 - Reader Part ......................................................................................................................... 5
Figure 2 - Controller Part ..................................................................................................................... 6
Figure 3 - Pin Header Position (all dimensions in mm) ....................................................................... 8
Figure 4 - Programming Interface (all dimensions in mm) .................................................................. 9
Figure 5 - RF Tracks - Impedance Calculation (dimensions in mil) .................................................. 10
Figure 6 - RF Part - PCB Stackup ..................................................................................................... 10
Figure 7 - Schematic Reader Section ............................................................................................... 11
Figure 8 - Schematic Loop Filter ....................................................................................................... 11
Figure 9 - Reader Indicator LEDs ...................................................................................................... 12
Figure 10 - Schematic Balun Section ................................................................................................ 13
Figure 11 - Schematic PA Section .................................................................................................... 14
Figure 12 - Schematic Directional Coupler........................................................................................ 15
Figure 13 - OAD Pads ....................................................................................................................... 16
Figure 14 - Schematic MCU Section ................................................................................................. 16
5.1 USB ..........................................................................................................................
7
5.2 UART Interface .........................................................................................................
7
5.3 Pin Header Interface Description ..............................................................................
8
5.4 Programming Interface Description........................................................................... 9
6.1 RF Tracks – Impedance Calculation .......................................................................
10
6.2 Reader Part – PCB Stackup ...................................................................................
10
6.3 Reader Part – Schematics ......................................................................................
11
6.4 OAD Pins ............................................................................................................... 16
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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1. Introduction
The FERMI Reader is a small form factor and low costs EPC Class 1 Gen 2 UHF RFID
demonstration reader system. Leveraging AS3993 UHF RFID Reader IC, provides close to the
industry’s lowest BOM cost, best in class power consumption with the least amount of
complexity.
Second only to ams FERMI design the low reader BOM enables UHF RFID markets that have
previously been out of reach due to cost restraints. With regards to overall cost vs. performance
the FERMI UHF RFID demo reader is unmatched in the industry.
With an external PA delivering up to 22 dBm, it is ideally suited for those applications that have
similar cost constraints but require that extra power
The FERMI demo reader comes in two parts namely the analogue (reader) and digital
(controller) parts. The user can separate the two stacked boards to fully prove out their own RF
and digital parts. With this set up it also means the user can evaluate the suitability of RFID in
their current system.
The reader portion is designed such that it can be easily connected to a host MCU via SPI. The
high level of integration found on the AS3993 UHF RFID Reader IC allows for minimal code
loading and quick implementation.
The designs come with free, fully portable code and all Gerber data and schematics. This allows
for a quick, trouble free design in.
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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2. Key Features
• Interface
o Between the Controller and Host Computer: USB (optional UART)
o Between the Controller and the AS3993 is SPI via a low cost pin header
connection
o Between the RF board and the Antenna we use a U.FL (50 Ohm) SMA (Male)
• 5V power supply from USB.
• GUI
o Adjust Output Power
o Adjust Receive – Sensitivity
o Adapt to different frequency schemes (FCC ETSI)
o Change Gen2 specific parameters like BLF, Coding, Anti-Collision Slots, …
o Diagnostic Features: RSSI Measurement, Reflected Power Measurement
o Support for sending AS3993 related direct commands
o Advanced Tag Manipulations: R/W to different memory banks, define passwords
o Associate tags with other applications like media player
o View and easily manipulate register settings with advance tool tip text.
• Low Power Consumption: complete reader system is only 780mW (typ), 830mW
(max)
• Fully Gen 2 compliant, ISO 18000-6b & 6c
• Differential TX chip-output configuration
• Differential RX chip-input configuration
• External power amplifier RF2172
• Maximum output power 22 dBm scalable in 20 steps
• Low cost MCU: Microchip (PIC24FJ64GB004)
• Indicator LEDs
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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3. Applications
Typical applications for the FERMI demo reader include:
• Embedded Consumer Applications
• Mobile Applications (Low Power Handheld, PDA’s, Smart Phones)
• Embedded Industrial Applications
• Gaming
• Desk top readers
• Low/Mid powered modules
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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4. Reader System Description
Figure 1 - Reader Part
1. AS3993 UHF RFID reader IC (ams)
2. Balun 2:1 (Johanson Technology)
3. Power Amplifier RF2172 (RFMD)
4. Directional coupler / Low pass filter combination (Johanson Technology)
5. U.FL antenna port (Hirose)
6. Loop Filter
7. OAD pins for debugging purposes
8. Balun 2:1 (Johanson Technology)
9. Crystal 20 MHz +/- 10ppm
1
3
2
5
4
7
8
9
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Figure 2 - Controller Part
1. MCU C8051F340 (Silabs)
2. USB connector
3. Interface connectors to reader PCB
4. UART connector
5. C2 programming interface for boot loader
6. Indicator LED
7. X-tal (for extended USB functionality)
8. LDO (5 V → 3.5 V)
1
3a
2
4
3c
3b
8
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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5 Interfaces
5.1 USB
The USB is used to communicate to the host computer and to supply the reader system. The 5V
USB voltage is regulated down to 3.5 V.
5.2 UART Interface
TX
GND
RX
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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In order to establish a connection to the host computer via UART it is recommend to use an USB
TTL serial cable with 3.3 Volt (FTDI TTL-232R-3V3-WE).
5.3 Pin Header Interface Description
Figure 3 - Pin Header Position (all dimensions in mm)
EN
IRQ
NCS
MISO
MOSI
CLSYS
CLK
GND
GP1
GP2
GND
GND
3V3
3V3
GP3
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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5.4 Programming Interface Description
Figure 4 - Programming Interface (all dimensions in mm)
PGEC
PGED
GND
3V3
MCLR
NC
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6 Reader Part
The reader part contains all RF and UHF RFID relevant components. In order to keep PCB costs
low the reader part is 2-layer PCB only while all components are located on the top layer. The
component placement was chosen to reach a small form factor PCB.
6.1 RF Tracks – Impedance Calculation
Figure 5 - RF Tracks - Impedance Calculation (dimensions in mil)
6.2 Reader Part – PCB Stackup
Figure 6 - RF Part - PCB Stackup
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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6.3 Reader Part – Schematics
Reader Section:
Figure 7 - Schematic Reader Section
Loop Filter:
Figure 8 - Schematic Loop Filter
The loop filter used for the PLL is partly inside the reader IC. The external part is shown above.
The loop filter values are provided by ams. Other values are possible and are mentioned in a
separate application note.
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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Indicator LEDs:
Figure 9 - Reader Indicator LEDs
The three indicator LEDs on the reader part together with the LED on the controller part are
used to display error states at the start-up of the reader system. LSB (bit 0) is the controller LED
and reader LEDs D1 – D3 are bit 1 – bit 3. If an error occurs during the start-up the LEDs are
slowly flashing the error code.
Error Codes:
0 : Everything OK. Controller LED flashes fast.
1 : writing + reading SPI failed.
2 : Reset via EN low + high failed.
3 : IRQ line failed.
4 : Crystal not stable (Bit0 in AGC and Internal Status register 0x2A)
5 : PLL not locked (Bits1 in AGC and Internal Status register 0x2A)
Example - PLL not locked: Controller LED and reader LED D2 are flashing slowly.
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Balun Section:
Figure 10 - Schematic Balun Section
The output impedance of the 0 dBm (low power) outputs are 100 ohm differential. Therefore a
2:1 Balun is used to convert the RF track impedance to 50 ohm single ended. In case the ouput
power should be very low the resistor R8, R9 and R10 (Pi-Pad) can be used to attenuate the RF
signal. It would be also possible to reduce the output power via reader IC register settings but
this should be done only down to -6 dB as the local oscillator signal inside the IC would become
too low. Per default the Pi-Pad is not installed.
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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PA Section:
Figure 11 - Schematic PA Section
The PA is supplied by the reader ICs internal voltage regulators. Since the reader ICs internal PA is
not used the corresponding voltage regulator (VDD_PA) is used for the external PA supply. The
power down pin of the external PA is supplied by the VDD_B regulator which is also supplies the 0
dBm output driver of the reader IC. The PA circuitry matches the proposal of the RF2172 datasheet.
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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Directional Coupler and RX Balun Section:
Figure 12 - Schematic Directional Coupler
The directional coupler also includes a low pass filter which attenuates the higher order
harmonics of the carrier signal. The directional coupler is needed in order to prevent the TX
signal leaking into the receiver. The used coupler is a trade-off between cost and directivity. The
antenna connector is a U.FL connector which is compatible with a microcoaxial connectors.
Since the directional coupler is a 10 dB coupler only 10 dB of the incoming tag signal is fed to
the RX Balun which converts the 50 ohm single ended impedance back to 100 ohm differential
need for the differential RX ports of the reader IC.
AS3993 – AN13 – Received Signal Strength Indicator (RSSI)
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6.4 OAD Pins
The pads J1 and J2 are connected to the OAD pins of the reader IC which can be used to output
analog/digital RX subcarrier signals or TX / RX based band signals.
Figure 13 - OAD Pads
7 Controller Part
The controller part contains the low cost MCU and the LDO used for reducing the USB voltage
down to 3.5 Volts. All the interfaces (USB, UART, …) are located on the controller part as well.
In order to allow USB functionality across all tolerances a crystal with 12 MHz is available.
Figure 14 - Schematic MCU Section
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Copyright
Copyright © 1997-2012, ams AG, Tobelbader Strasse 30, 8141 Unterpremstaetten, Austria-Europe.
Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged,
translated, stored, or used without the prior written consent of the copyright owner.
All products and companies mentioned are trademarks or registered trademarks of their respective companies.
Disclaimer
Devices sold by ams AG are covered by the warranty and patent indemnification provisions appearing in its
Term of Sale. ams AG makes no warranty, express, statutory, implied, or by description regarding the
information set forth herein or regarding the freedom of the described devices from patent infringement. ams
AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to
designing this product into a system, it is necessary to check with ams AG for current information.
This product is intended for use in normal commercial applications. Applications requiring extended
temperature range, unusual environmental requirements, or high reliability applications, such as military,
medical life-support or lifesustaining equipment are specifically not recommended without additional
processing by ams AG for each application. For shipments of less than 100 parts the manufacturing flow might
show deviations from the standard production flow, such as test flow or test location.
The information furnished here by ams AG is believed to be correct and accurate. However, ams AG shall not
be liable to recipient or any third party for any damages, including but not limited to personal injury, property
damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential
damages, of any kind, in connection with or arising out of the furnishing, performance or use of the technical
data herein. No obligation or liability to recipient or any third party shall arise or flow out of ams AG rendering of
technical or other services.
Contact Information
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ams AG
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