Test considerations for NFC enabled devices in manufacturing

Transcription

1 WHITEPAPER Test considerations for NFC enabled devices in manufacturing Why it is Important and How to Perform Effective Tests 2016 LitePoint, A Teradyne Company. All rights reserved.

2 Table of Contents Abstract... 3 Overview of the NFC Market... 3 Introduction of the Technology... 3 Importance of NFC manufacturing test... 5 Key characteristics of NFC physical layer... 5 Golden DUT approach not providing a high quality test... 7 Key NFC measurements... 7 Frequency response... 8 Basic connectivity... 9 Tx parameters... 9 Rx sensitivity... 9 LitePoint NFC solution... 9 Summary References Test considerations for NFC enabled devices in manufacturing 2

3 Abstract Near Field Communication (NFC) technology has gained meaningful traction in the market and it is poised to build global scale. The technology is especially easy to use and versatile enough to support a wide range of consumer and business applications, which heighten its promise. Though considered a relatively simple technology, the performance of an NFC subsystem can be impacted by subtle variations that may occur during device production. Therefore, manufacturers need to employ verification tests to ensure that NFC-enabled products work as intended. The purpose of this article is to explain why NFC testing is important and how to ensure the accuracy and effectiveness of such production tests so the technology can advance in the market in a manner that encourages its success. Overview of the NFC Market Near field communication (NFC) products have been shipping for several years and while originally slow to gain traction, NFC services are finally evolving from trial to commercial status around the world. As of the end of 2013, around 10 chipset companies were producing NFC chips and hundreds of NFC-capable mobile phones and tablets were commercially available [1]. During the 2013 Mobile World Congress, nearly all smart device manufacturers showcased NFC-enabled products and many service providers, vendors and developers presented innovative applications illustrating the broad range of capabilities NFC offers. ABI Research forecasts that nearly two billion NFC-enabled devices will ship in 2017; the devices will include smartphones as well as tablets, PC accessories and gaming consoles [2]. Smartphones will represent a fundamental market for NFC. ABI Research expects that handsets will account for 75% of the two billion NFC devices shipped in 2017 [3]. The handset segment has already begun to take off and shipments in 2013 should double the number of units shipped in 2012, which reached 102 million. ABI Research asserts that NFC, now offered by nine of the top 10 OEMs, is on track to become a default technology in flagship devices [4]. NFC has generated considerable interest for its potential to facilitate mobile wallet and other financial transactions. While there are a variety of business and ecosystem challenges that must be overcome to make NFC-enabled financial transactions mainstream, both telecom and financial industries are pursuing this aggressively. ABI Research expects that the value of NFC-enabled transactions, estimated at $4 billion in 2012, will skyrocket to $100 billion in 2016 and reach $191 billion in 2017 [5]. Introduction of the Technology NFC is a set of short-range wireless technologies that builds on the RFID systems to enable two-way communication between devices. NFC enabled devices communicate through magnetic field induction between electronic devices in close proximity. It operates at MHz through Amplitude Shift Keying (ASK) at data rates from 106 to 848 kbit/s, typically over a distance of 4 cm or less. NFC is a peer-to-peer communication and always involves an initiator and a target. In one mode of communication, the initiator generates an electromagnetic field and the target is powered up by this field and starts communication. In this mode, the target requires no power source, or battery, and be made quite small, in simple form factors, such as tags, stickers, or plastic cards. Applications include bank cards, transportation payment system, fast WiFi/BT peering, etc. In another mode of communication, both initiator and target have their own power source and can carry out peer-to-peer communication. Applications include file exchange between smartphones such as Android Beam. Through these two modes of operation, NFC makes it possible for consumers, with the simple tap of a device, to interact with many types of appropriately enabled digital products and infrastructure. Figure 1 shows examples of various NFC applications and in different operation modes. Test considerations for NFC enabled devices in manufacturing 3

4 Applications OS CPU Secure Element or SIM NFC Chip NFC coil Load Modulation RF MHz Load Modulation RF MHz Card Emulation Mode Transport & Ticketing Access Control Mobile Payment Phone (Passive) Reader (Active) Reader Mode Smart Posters ID Check Mobile Advertising Phone (Active) Device (Passive) Peer to Peer Mode Data Exchange P2P Payment Figure 1 NFC application examples RF MHz Phone (Active) Device (Active) There are a number of ISO standards and industry forums that define the NFC specifications and ensure interoperability between devices. Table 1 summarizes the NFC standards, use cases and terminologies. Standard Main Use Cases DUT as Transmitter DUT as Receiver ISO Type A and B (Proximity) Contactless smart cards (mobile identification, ticketing, access control, transit, toll-gate) ISO (Vicinity) VCD VICC ISO E-Wallet, mobile phone data transfer Initiator Target PCD PICC NFC Forum Based on ISO and ISO standards. Promote NFC and ensure interoperability Polling Device Listening Device FeliCa Based on Japanese standard Polling Device Listening Device EMVco Contactless specification for payment systems PCD PICC Table 1 NFC standards Test considerations for NFC enabled devices in manufacturing 4

5 Importance of NFC manufacturing test Manufacturers of NFC products are entering a critical period in the technology s market growth. While momentum is building, the technology s ability to sustain this momentum and achieve ongoing mainstream usage depends on its ability to consistently deliver a successful customer experience. Thus far, the lack of NFC applications and consumer awareness has minimized its uptake and as a result, the industry probably does not fully understand if the devices in the field actually work as well as they should. With market growth now intensifying, manufacturers must make sure their products offer the best possible performance to support a positive customer experience. Given the broad applicability of NFC and the imaginative ways in which it might be used across industries, malfunctioning devices could have broad implications. The media, when reviewing new products and services, will draw attention to real or perceived performance issues. One NFC reviewer in All Things Digital recently noted that she had to tap her NFC smartphone against the payment terminal several times to complete a purchase transaction in a retail store [6]. While the transaction did eventually go through and she did assert that she fully expects smartphone NFC payment services to improve, she noted that a routine credit card process would have been faster. This example illustrates the importance of properly functioning NFC devices. A malfunction that disrupts payments, for example, could undermine the value of the potentially lucrative financial transactions market. Businesses offering devices and services associated with the failed transactions could lose not only revenue but also brand equity. Similar impacts could be felt in the transportation industry if passengers are unable to use their NFC devices to enter a subway station or board a plane. Likewise, businesses will feel the impact if their employees can t enter the workplace or log onto the corporate network with their NFC devices, to cite just a few examples. Key characteristics of NFC physical layer NFC is simple in concept but it actually is a very sophisticated technology. It operates very differently as compared to other wireless technologies such as WiFi and cellular standards. NFC relies on near field induction as communication media and uses resonant analog circuits to provide efficient power transfer. However, such circuits are sensitive to analog component variations. LitePoint carried out simulations on a typical NFC circuit design by assuming 5% analog component variation, which is typical for manufacturing. The simulation results (Figure 2) show a wide spread shift in frequency response. Frequency response shift has significant impact on NFC performance. For example, a 500 khz shift can reduce the transmitted energy by nearly 50%. This results in higher power consumption and reduced operation range for NFC devices, which leads to poor user experience. Test considerations for NFC enabled devices in manufacturing 5

6 CASE 2 COUPLED RESPONSE COMPONENTS VARIED K FIXED Nearly 50% reduction in transmitted energy COUPLED LOSS (db) DB ( S(2,1) ) Case 2 coupled_response_ components_varied_k_fixed FREQUENCY (MHz) 500 khz Shift (on a 1 MHz BW Signal) Figure 2 A small shift in matching component values and/or tolerances can dramatically impact system performance The new NFC coil designs are getting smaller and smaller (Figure 3). The smaller coils are becoming more popular in smartphone designs due to size constrains. Although small coils are easier to design into devices, they present significant challenges in achieving the required NFC RF performance. Smaller coils have much lower tolerance levels on inductive coupling than larger coils. This makes them very sensitive to device placement during NFC transactions. For example, it may require that the two NFC devices be at touching distance with direct coil alignment. If frequency response of the matching circuit is off, NFC may not work at all for the smaller coils. This makes it even more important that the resonant frequency be in the right range to ensure operation and performance. Figure 3 NFC antenna coils 30x30mm 17x30mm 10x10mm Test considerations for NFC enabled devices in manufacturing 6

7 Golden DUT approach not providing a high quality test Some NFC device manufacturers use a reference or golden DUT or an NFC card reader to verify the NFC operation of devices during production. While the use of a golden unit is a practical and common production test method, this approach has its limitations. For example, it only yields a pass-fail or go/no go result and might pass a unit that has underlying issues. Even when it detects a failed unit, the test can t yield quantitative information to identify the cause of the failure. Another limitation is that golden DUTs or card readers can t detect a marginal unit. A device might work in the controlled conditions present on the production line and pass a go/no go factory test but lack the capability to operate in uncontrolled, real-world conditions when it might have to interact with non-ideal card readers or NFC tags or function in a wide range of temperatures. Ultimately, because golden DUT or NFC readers cannot reveal errors in manufacturing, large quantities of units could conceivably ship with defects that require higher power consumption and reduce the product s operating range. Manufacturers can protect their businesses from this risk by employing RF parametric tests to identify and correct performance variations during production. Key NFC measurements Figure 4 shows a typical NFC enabled smart phone architecture. As discussed earlier the multi-standard chip, matching and resonating components, and antenna coil are the key components that should be tested in manufacturing. Therefore, we recommend carrying out a frequency response test, as well as a basic connectivity test during which the basic functions of NFC standards are exercised. We feel, in most cases, this is sufficient to determine the product is free from defects and meets requirements. Given the product design has been fully characterized and verified to the applicable standards in the R&D and Design Verification phase, running the exact standard defined tests are both unwise and unnecessary in the manufacturing environment. It is felt that A resonance sweep in manufacturing is sufficient to find any matching or resonance performance related defects that would impact operation over the required operating envelope, provided that the design has be fully verified, and that performance of the verified design is characterized (and limits defined) in the manufacturing test fixturing. Application Processor C NFC Die R L C or Secure Element EEPROM R Figure 4 NFC-enabled smartphone architecture Multi-standard Resonant circuit Smaller coil Test considerations for NFC enabled devices in manufacturing 7

8 Frequency response The frequency response measurement can be carried out by running a Return Loss sweep of the test fixture coil, to get the energy absorbed by the device under test, over the frequency range of interest for NFC (e.g. 10 to 20MHz). Figure 5 shows an example of frequency response of a NFC device. This provides quantitative data on the physical characteristics of NFC circuit components, board, interconnects and antenna coil, as well as any packaging effects. Simple numerical results such as center frequency, 3dB bandwidth and Q factor can be obtained and used to determine pass/fail performance. It ensures all the components in the transceiver RF path are correctly installed, within tolerance and no assembly defects exist. This measurement can be made through a network analyzer type of architecture in which a CW source sweeps a frequency range and an analyzer monitors the return signal and compares that with the CW source. This allows the tester to measure resonant frequency of the DUT matching circuit and coil. 0 RETURN LOSS (db) FREQUENCY (MHz) Name Q (peak level) Q (geometric mean of 3dB BW boundries) 3 db BW Resonant Frequency (peak level) Resonant Frequency (geometric mean of 3dB BW boundries) Value Unit MHz MHz MHz Figure 5 Example of frequency sweep for a NFC device Test considerations for NFC enabled devices in manufacturing 8

9 Basic connectivity Basic connectivity test is carried out by initiating communications and going through initial hand-shakes of NFC protocol stacks. This provides a system level functional check and ensures the DUT can both receive and transmit correctly on all the supported NFC standards. It essentially checks that the IC has not been damaged during assembly, its pins are correctly soldered and the digital circuit is corrected connected. During development testing and, optionally, for manufacturing testing (during the above connectivity tests), the field strength level and modulation depth of the tester can be reduced to verify that any sensitivity, transmit level or loss related defects are uncovered. As well as additional Tx parameters can be measured. See Tx parameters and Rx sensitivity below. Tx parameters Depending on the DUT design, transmitter RF parametric tests can be useful for uncovering defects. They provide detailed information of the physical layer performance parameters, such as field strength, frequency error (carrier and/or subcarrier), modulation quality and depth, and frame delay time. If the DUT is capable of being initiator and target, both modes should be independently tested. Rx sensitivity This test measures the minimum signal level that can be detected by the DUT (after which it produces a response back to the sender). As the DUT is moved away from its NFC peer, the signal level dropped exponentially with the distance. Therefore the Rx sensitivity test directly relates to the operation range of the DUT. As opposed to physically moving the DUT to test coupling distance, sensitivity can be tested by reducing the tester generated field strength or modulation depth and monitoring the DUT response until such a point that the tester doesn t receive a response back from DUT, and measuring the level set for the tester to determine DUT sensitivity level. LitePoint NFC solution LitePoint NFC solution (IQnfc+) is a compact and rugged test system that s optimized for both production lines and labs. It s a simple-to-setup and easy-to-use system that allows one-click operation to quickly characterize the DUT in the production lines, while also provides intuitive GUI for detailed waveform analysis and flexible APIs to customize test flow in the labs. IQnfc+ supports measurement of all key NFC standards in both initiator and target modes. See Table 2. The tester also has comprehensive coverage of all the key NFC measurements. See Table 3. Figure 6 LitePoint IQnfc+ tester Test considerations for NFC enabled devices in manufacturing 9

10 Test mode (NFC Forum) ISO Standard Initiator Target NFC A 14443A (EMVco) NFC B 14443B (EMVco) NFC F (FeliCa) NFC P2P peer to peer Table 2 IQnfc+ standard coverage Test Basic functional Test Field strength Frequency accuracy Target frame delay time Modulation depth/index/ timing profile Rx sensitivity Payload data CRC error Description Carry out initialization procedure (DUT as initiator and target) Measure carrier field strength (DUT as initiator) Measure DUT frequency error (DUT as initiator) Measure the DUT response time (DUT as target) Measure waveform shape (DUT as initiator and target) Min detectable field strength (DUT as initiator and target) Provide results of received payload data (DUT as initiator and target) Provide results of CRC error (DUT as initiator and target) Table 3 IQnfc+ test coverage Test considerations for NFC enabled devices in manufacturing 10

11 Summary LitePoint is the market leader in production test of connectivity and cellular devices. We maintain our market leadership with innovative solutions that rapidly address emerging wireless technologies. With the emergence of NFC-enabled devices, LitePoint is ready to handle your production requirements with the IQnfc+ test solution. Please contact our representatives to further discuss how this innovative new NFC solution can help achieve your NFC test requirements. References [1] Full list of NFC enabled phones, updated on Jan.2, [2] NFC will Come Out of the Trial Phase in 2013 as 285 Million Enabled Devices are Expected to be Shipped, ABI Research press release Nov. 21, [3] ABI Raises NFC Handset Forecast, by Mike Clark, in NFC World, Nov. 22, [4] NFC will Come Out of the Trial Phase in 2013 as 285 Million Enabled Devices are Expected to be Shipped, ABI Research press release Nov. 21, [5] NFC Mobile Payment Transaction Spend to Hit the $100 billion Mark in 2016, ABI Research press release, Oct. 18, [6] NFC: What You Need to Know, by Lauren Goode, in All Things Digital, Feb. 18, Test considerations for NFC enabled devices in manufacturing 11

12 Copyright 2016 LitePoint, A Teradyne Company. All rights reserved RESTRICTED RIGHTS LEGEND No part of this document may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language or computer language, in any form or by any means, electronic, mechanical, magnetic, optical, chemical, manual, or otherwise, without the prior written permission of LitePoint Corporation. TRADEMARKS LitePoint and the LitePoint logo are registered trademarks of LitePoint Corporation. IQnfc+ is a trademark of LitePoint Corporation. All other trademarks or registered trademarks are owned by their respective owners. DISCLAIMER LitePoint Corporation makes no representations or warranties with respect to the contents of this manual or of the associated LitePoint Corporation products, and specifically disclaims any implied warranties of merchantability or fitness for any particular purpose. LitePoint Corporation shall under no circumstances be liable for incidental or consequential damages or related expenses resulting from the use of this product, even if it has been notified of the possibility of such damages. If you find errors or problems with this documentation, please notify LitePoint Corporation at the address listed below. LitePoint Corporation does not guarantee that this document is errorfree. LitePoint Corporation reserves the right to make changes in specifications and other information contained in this document without prior notice. CONTACT INFORMATION LitePoint Corporation 965 W. Maude Ave. Sunnyvale, CA United States of America Telephone: Facsimile: LITEPOINT TECHNICAL SUPPORT Doc: September 2016 Rev 3