s-38.3310 tietoverkkotekniikan diplomityöseminaari 09.05.2006

Tuesday, May 09, 2006Elcoteq Presentation / Jussi Savolainen 1

S-38.3310 Tietoverkkotekniikan diplomityöseminaari

09.05.2006

Title: Automatic Bluetooth Radio Frequency Measurement System

Author: Jussi Savolainen

Supervisor: Prof. Sven-Gustav Häggman

Instructor: Petteri Yrjälä, M.Sc.

Work carried out at: Elcoteq Design Center Oy, Salo


Presentation outline

• Background• Research problem• Research methods• Bluetooth essentials• Bluetooth RF measurements• System setup• Software implementation• Conclusions and further work


Background

• Bluetooth RF conformance testing by far the most expensive (time and cost) of the conformance tests, because– off-the-shelf test systems > 1 M€ (cost)– response time using external test houses too long (time)

• Projects need a heap of test data in a short amount of time for statistical analysis, etc.

• Failing in type approval tests is expensive


Research problem

• How to automatically perform the Bluetooth RF conformance tests according to Bluetooth Test Specification version 2.0+EDR in prequalification phase of the design

• How to perform the tests simultaneously for a number of devices

• How to support different Bluetooth products and product types


Research methods

• Literary study (Bluetooth RF specification, Bluetooth test specification, measurement device vendor application notes, etc.)

• Vendor audits/interviews

• HW Designer interviews

• UI usability study

• Data storage study


Bluetooth essentials

• Bluetooth connects portable or fixed equipment, and it is a cable replacing technology, which is cheap and robust with low power consumption

• Technology initially developed at Ericsson in 1994• Bluetooth SIG established in 1998, first version of specification

out same year• Most recent version 2.0+EDR came out in 2004 with support to

higher data rates than previously• Operates on unlicensed (but not unregulated!) 2.4GHz ISM band

M

S S

S

M/S

S

piconet 1

piconet 2

ps

sb

ps

Scatternet with two piconets


Bluetooth essentials – protocol stack

• Bluetooth protocol stack is a fuzzy structure• Controller and Host can be separated using HCI, chipset and

applications implemented separately• Thesis discusses mainly radio layer

RADIO

BASEBAND AND LINK CONTROLLER

LINK MANAGER

L2CAP

HOST CONTROLLER INTERFACE

RFCOMM

OBEX WAP TCS SDP

APPLICATIONS

two-way voice control

data

HOST

CONTROLLER


Bluetooth essentials – packet structure

• Basic rate 1Mb/s• Enhanced Data Rate 2Mb/s or 3Mb/s• in EDR packets modulation is changed during the burst from

2FSK to PSK (backwards compatible)• EDR mostly affects radio layer

LSB

ACCESS CODE

HEADER

MSB

PAYLOAD

68/72b 54b 0-2745b

LSB

ACCESS CODE

HEADER

MSB

PAYLOAD

72b 54b 16-8200b

GUARD SYNC

5 µs 11 µs

2FSK PSK

General basic rate packet format

General enhanced data rate packet format


Bluetooth RF measurements - basics

• Device Under Test (DUT) can be placed to test mode, which allows configuration and control of the DUT

• Some tests must be performed under extreme temperature and voltage conditions

• Tests divided in transmitter (TX), receiver (RX) and transceiver (TRC) measurements

• TX and RX tests according to Bluetooth RF test specification

• TRC tests according to ETSI EN 300 328


Bluetooth RF measurements – TX tests

Measurement Description

Output power Maximum peak and average power of the burst

Power density Maximum RF-output power density

Power control Verification of power control

Frequency range Emissions inside the operating frequency within limits

20dB bandwidth Emissions inside the operating frequency within limits

Adjacent channel power Emissions inside the operating frequency within limits

Modulation characteristics Modulation index

Initial carrier frequency tolerance Transmitter carrier frequency accuracy

Carrier frequency drift Transmitter centre frequency drift within a packet

EDR relative transmit power Difference in power during 2FSK and PSK portions of packet

EDR carrier frequency stability and modulation accuracy

Carrier frequency stability and modulation accuracy

EDR differential phase encoding Differential phase encoded data correctness

EDR in-band spurious emissions Unwanted signal levels on adjacent channels

• TX tests either power measurement as function of frequency or frequency as function of time


Bluetooth RF measurements – RX tests

• RX tests are BER measurements performed under different stimulus conditions

Measurement Description

Sensitivity – Single slot packets Required sensitivity with non-ideal signal

Sensitivity – Multi slot packets Required sensitivity with non-ideal signal

C/I performance Sensitivity in presence of co-/adjacent channel interference

Blocking performance Sensitivity in presence of out-of-band interference

Intermodulation performance Verification of receiver’s intermodulation characteristics

Maximum input level Receiver performance in presence of high power signal

EDR sensitivity Required sensitivity with non-ideal signal

EDR BER floor performance Receiver performance for 10^-5 BER

EDR C/I performance Sensitivity in presence of co-/adjacent channel interference

EDR maximum input level Receiver performance in presence of high power signal


Bluetooth RF measurements – TRC tests

• Out-of-band spurious emissions measured according to ETSI EN 300 328

• Does not belong to Bluetooth conformance tests

• Measures harmonics of the carrier signal, cabinet radiation and modulation products


System setup

• All Bluetooth RF conformance tests and out-of-band spurious emission measurement must be performed automatically with one setup

• 12 DUTs measured simultaneously• Capable of measuring any Bluetooth device which implements at

minimum the controller

Relay box

RF Shield

Multiplexer1x12

Climate chamber

Multiplexer1x4

IQ

CW

SpectrAn

BT tester

Multiplexer1x12

GSMSignalingGSM

Multiplexer1x4

Multiplexer1x4

ATT


System setup - equipment

Device Description

BT tester Bluetooth signaling tester capable of performing EDR measurements

RF shield Attenuates interfering RF signals

Temperature chamber

Used in extreme temperature conditions (typ. -20ºC and +55 ºC)

Relay box Used to filter unwanted frequencies e.g. in out-of-band spurious measurement

IQ Signal generator capable of producing Bluetooth modulated interfering signals

CW Signal generator capable of producing continuous wave signals

Spectr an Spectrum analyzer capable of gating

GSM signaling GSM & 3G signaling tester for coexistence testing

• Altogether ~ 200 k€• Calibration of the transmission paths from 30MHz to 13GHz with

1MHz steps


Software implementation - UI


Software implementation – data storage

• System creates ~50Mb/day of data text files or excel sheets are not an option

• Writer (test system/test engineer) and reader (customer project/RF designer) are separated

• Graphs and reports must be easily extractable from database

• Short response time for new graphs and reports


Conclusions and further work

• This type of system is never finished as interface to a new DUT must be built every time and data storage is updated

• Error handling updates

• Calibration

• Measurement equipment SW updates


¿Questions?

DANKE!


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s-38.3310 tietoverkkotekniikan diplomityöseminaari 09.05.2006

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