Electronic Design

Test Solutions Rise To Meet The Bluetooth Development Challenge

A multifaceted and fast-growing communications technology is calling for a new breed of test equipment.

The unprecedented growth in the Bluetooth standard has led to a great demand for tools to perform design/development, pre-certification, conformance, and manufacturing testing. An assortment of specialized test equipment now offered by the leading manufacturers provides testing solutions for the entire product cycle. Also, there is a demand for tools because every product must pass the Bluetooth qualification tests before it can be sold. These tools, therefore, play a major role in preparing for the mandatory conformance tests.

Bluetooth is a wireless communications standard for seamlessly connecting notebook computers, cellular phones, PDAs, and other portable handheld devices (see "A Low-Power, Frequency-Hopping System" p. 98). Due to its low cost, small form factor, and low power, it's rapidly gaining momentum and is poised to become the leading wireless communication technology for small mobile devices. It's backed by giant companies, such as Ericsson, IBM, Intel, Lucent, Microsoft, Motorola, Nokia, and Toshiba—the initial promoters of the Bluetooth Special Interest Group (SIG).

According to Allied Business Intelligence (ABI), annual shipments of Bluetooth-enabled devices will reach a whopping 1.4 billion units in 2005. That's more than a 25-fold increase in shipments from 53 million units this year.

The "Bluetooth" name actually dates back to the 10th century Danish king, Harald Blatand (or "Bluetooth" in English), who was credited with the unification of Denmark and Norway. Little did he know that 10 centuries later, a new technology representing the unification of the telecommunication and computer industries would be named in his honor. This multifaceted, emerging technology poses many design challenges ranging from analog RF to digital to protocol analysis. These are recognized by the leading manufacturers of test and design tools, and these companies are now offering a broad range of equipment that addresses the development, characterization, and verification of the Bluetooth components and products.

The most fundamental tool, the oscilloscope, requires good performance in bandwidth, input sensitivity, and sample rate for Bluetooth design and troubleshooting applications. Tektronix's TDS 3000 series of digital phosphor oscilloscopes can be used here. Suitable for Bluetooth development, they feature bandwidths of up to 500 MHz and sample rates of up to 5 Gsamples/s.

Additionally, the TDS 3000 family offers an impressive variety of acquisition modes and trigger types that are critical to accurate measurement and analysis. For example, the peak detect acquisition mode is used for capturing high-frequency and random glitches as narrow as 1 ns. The trigger system supports different trigger modes, including edge, logic, and pulse triggers. A waveform-processing feature allows channel-to-channel deskewing of ±10 ns for better timing measurement and accurate math waveforms. It also permits the addition, subtraction, multiplication, and division of waveforms.

Similarly, the 54620 series of mixed-signal oscilloscopes from Agilent Technologies is optimized for the verification and debugging of Bluetooth baseband signals. These combine the detailed signal analysis of an oscilloscope with the multichannel timing measurements of a logic analyzer, permitting simultaneous testing and monitoring of the high-speed digital signals and lower-speed analog signals.

Designers of mixers, oscillators, modulators, amplifiers, and other components frequently need to provide stimuli to the device under test (DUT) prior to the availability of a Bluetooth component in their system. Correct modulation, burst-profile, test-data sequences, hopping characteristics, and spectral shapes are necessary to determine performance under real-world conditions. For receiver designers, extremely accurate low-level outputs of test signals are required to test sensitivity. They're needed to test receiver performance in the presence of both modulated and carrier wave interfering carriers, too.

Tektronix's SMIQ series of signal generators and AMIQ arbitrary waveform generators were designed for such tasks. They feature 14-bit resolution, a 4 million sample memory depth, a 100-MHz sample rate, calculation of digitally modulated I/Q and IF signals, and superposition/simulation of impairments, as well as single-carrier, multicarrier, and CDMA signals.

Analysis And Qualification Testing
Qualification to the Bluetooth standard is extremely important for manufacturers of Bluetooth systems, but little if any qualification test equipment is available to help. One of the few, Agilent's ESG-D series arbitrary waveform generator, provides a flexible solution for Bluetooth product qualification standards. It generates standard-compliant signals for both transmitter and receiver testing. An optional internal bit-error-rate analyzer can be used to verify Bluetooth receiver performance. Plus, it can perform receiver measurements, such as sensitivity, blocking performance, intermodulation performance, and maximum input level. For the transmitter measurements, the ESG-D series supplies a standard Bluetooth signal to a DUT operating in the loopback mode.

Bluetooth is a frequency-hopping system that's expected to operate in a high-interference environment. Transient interference can come from other products such as microwave ovens, and other RF sources can impair Bluetooth transmission and reception. Furthermore, the set-on time and settling performance of the hopping transmitter can be subject to design flaws in hardware. For frequency-hopping testing, Tektronix's WCA389 spectrum analyzer and Agilent's ESG-D can be employed in conjunction with the E6432A VXI microwave synthesizer to produce standard-compliant frequency-hopped signals at 1600 hops/s.

A fundamental tool for de-bugging a network system is a protocol analyzer. The successful design of Bluetooth products requires hardware/software integration and design and debugging, including packet-data error generation, data decryption, real-time protocol decoding and display, and sophisticated triggering.

From Computer Access Technology Corp. (CATC), the Merlin Bluetooth protocol analyzer is a nonintrusive test tool that captures and displays Piconet data. It features programmable real-time event triggering and capture filtering. This is a critical feature in any protocol analyzer because it indicates the analyzer's ability to extract useful information from a crowded stream of bus traffic. Identifying and selectively recording transactions is crucial for successful debugging. This advanced triggering mechanism is supported by sophisticated event counting and a sequencing facility in Merlin.

The count and sequence options define the rules for data recording sessions, and these options enable configuring and controlling of the order in which events must occur before triggering. Merlin provides reliable and accurate (100-ns resolution) time stamping of recorded traffic and comprehensive error detection and analysis. It detects and alerts the user to every potential bus error and protocol violation, including such error conditions as CRC error, HEC error, FEC error, invalid packet type, header length error, payload length error, and sync lost.

Another Bluetooth analyzer product, Sniffer from Digianswer Ireland Ltd., consists of a USB-based hardware unit and a software application called the Data Collector. Together, they make it possible to set up a log session during which users can intercept all of the data transmitted between the devices forming a Bluetooth Piconet.

Another application that works with the Sniffer is known as the Bluetooth Packet Analyzer. Its function is to analyze the data logged during a session. The Packet Analyzer can isolate, decode, and display LMP, L2CAP, RFCOMM, and SDP packets, as well as OBEX commands, events, and data packets. Tektronix's BPA100 protocol analyzer, which features Bluetooth SIG, qualified radio, baseband, and hot-stack technology, provides functionality similar to that of the Sniffer (Fig. 1).

There's a real need for test equipment that can effectively measure faster and more complex RF devices that use wider channel bandwidths. One of the first instruments to offer this capability is the MI 4115A Modulated Vector Network Analyzer (MVNA) from Credence Systems Corp. This device can implement any modulated or unmodulated stimulus for measuring next-generation Bluetooth and 3G cellular devices, instead of the sinusoidal-only stimulus provided by existing vector network analyzers. It also provides increased accuracy by simultaneously measuring S-parameter, spectrum, power, and power-envelope data. This eliminates the requirement of employing multiple instruments, and it provides a single and consistent set of data from which all RF parameters are calculated.

The instrument is used as an amplifier test system that offers high- and low-power configurations for infrastructure and RF device applications. Concurrently, it achieves a wide bandwidth and an 80-dB dynamic range in a system that can sample at 60 Msamples/s.

A parallel receiver architecture and the ability to calculate multiple measurements from a single data acquisition further enhance the instrument's speed. The MV 415A is based on a modular CompactPCI architecture and makes use of the Windows NT operating system.

For production, development, and maintenance of devices with integrated Bluetooth wireless technology, a radio tester is necessary. Tektronix's CMU200 Radio Tester, with its Bluetooth option, permits users to set up a Bluetooth connection to a device that's under test via an RF interface. The CMU200 can switch the DUT into the test mode and perform a number of RF measurements, which can all be accomplished in hopping, reduced hopping, or nonhopping modes. The CMU supports measurements using DH1, DH3, and DH5 packets.

RTX Telecom A/S offers the RTX2204 Bluetooth RF tester with similar functionalities, but it requires an external PC to serve as a graphical user interface to control the tester. Agilent's E1852A Bluetooth Communication Test Set also offers similar functional and parametric test capabilities (Fig. 2).

Customers with final-stage Bluetooth designs that include protocol-layer software will need to verify conformance to executable test cases (ETC) developed by the Bluetooth SIG. These test cases require exercising the DUT in a series of specified real-world conditions. To achieve this level of testing, it's necessary to operate the DUT via the air interface in a live Piconet. A piece of equipment that can help is the Tektronix PTW60 Protocol Tester.

This Bluetooth real-time signaling unit can simulate the Bluetooth Piconet. It operates as a master in up to two Piconets and provides test-mode signaling and the ability to inject custom messages in addition to running the ETCs specified by the SIG. It also supports Tree and Tabular Combined Notation (TTCN) test cases for the Bluetooth profiles.

Another test tool called Bluetooth PreQual from Telelogic North America Inc. allows pre-qualification of Bluetooth applications. It uses the same conformance test suites written in TTCN that are used for the official qualification of Bluetooth products. PreQual includes a test suite for the host controller interface (HCI) too. The MSC logging function provides adequate documentation for the declaration with the evidence, which is needed for qualification tests in categories B and C. Currently, PreQual is available for Windows 2000 platforms.

Finally, at the completion of the Bluetooth product design, when a product is released to manufacturing, obligatory RF measurements for the qualification of Bluetooth devices are performed. These measurements and tests include the conformance to such parameters as occupied bandwidth (OBW), power, and spectrum occupancy.

Tektronix's TS8960 is a qualification measurement system that fits the bill for such measurements. Based on the Bluetooth Core Specification 1.0 and the Bluetooth RF Test Specification 0.7, it can be implemented for conformance testing as well as testing during development and the quality assurance process.

Bluetooth is an emerging technology with enormous growth potential and elaborate and sophisticated conformance-to-test requirements. It be-hooves the designers and manufacturers of Bluetooth equipment to not only understand these requirements, but also to have access to the appropriate equipment and tools that will help them complete and pass the mandatory tests.

Bluetooth information Web sites:
www.bluetooth.com: Official Bluetooth SIG Web site.
www.palopt.com.au/bluetooth: Extensive list of links to Bluetooth resources on the net.
www.bluetooth.net: Independent Bluetooth site sponsored by Digianswer.

Companies Mentioned In This Report
Agilent Technologies
(650) 752-5000

Computer Access Technology Corp.
(408) 727-6600

Credence Systems Corp.
(510) 623-4774

Digianswer Ireland Ltd.
+353 1 860 0136

RTX Telecom A/S
+45 96322300

Tektronix Inc.
(800) 835-9433

Telelogic North America Inc.
(408) 451-3160

TAGS: Mobile Intel
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