Bluetooth Testing: Tools and Techniques for RF and PHY Conformance

This page provides an overview of Bluetooth testing, focusing on transmitter and receiver testing, including RF and baseband (PHY) conformance aspects. We’ll also explore Bluetooth test tools available from leading vendors.

Bluetooth, a ubiquitous wireless technology, is used in applications ranging from Bluetooth headsets for mobile calls to data and file transfer. Several Bluetooth versions exist, including V1.0, V1.2, V2.0, V2.1, V3.0, and V4.0, each supporting different modulation schemes (e.g., GFSK, DQPSK, DPSK), packet formats, and data rates.

Bluetooth packets fall into two main categories: basic rate and enhanced data rate (EDR). A basic rate packet consists of an access code, header, and payload. EDR packets, on the other hand, comprise an access code, header, guard, sync, EDR payload, and trailer.

The Bluetooth standard defines different power classes for Bluetooth devices: class-1, class-2, and class-3. These classes dictate varying transmit power profiles, including power ranges and minimum/maximum power limits.

Generally, Bluetooth devices support two test modes to streamline mass production testing: loopback test mode and transmit test mode, illustrated below:

Loopback Test Mode: The Bluetooth device transmits the packet it receives from the Bluetooth tester, echoing the same payload. The tester then compares the transmitted payload with the original to determine a pass/fail result.

Transmit Test Mode: The Bluetooth device receives instructions from the tester regarding which packet to transmit. It transmits the designated packet, and the tester compares the transmission with the instructions provided.

Furthermore, Bluetooth devices must be evaluated against the protocol stack, depicted here:

Two primary technology standards underpin Bluetooth device development: standard legacy Bluetooth (pre-V4.0) and Bluetooth Low Energy (BLE, version 4.0 and later). Various conformance test tools, as detailed below, are available for testing Bluetooth physical layer, RF layer, and upper-layer specifications.

A crucial aspect of Bluetooth RF testing is evaluating modulation characteristics and the RF channel frequency of the device. Standard Bluetooth devices utilize 79 channels from 2.4 GHz to 2.4835 GHz, spaced 1 MHz apart. BLE devices use 40 channels from 2.402 GHz to 2.480 GHz, including 3 advertising and 37 data channels.

Transmitter Testing

The following tests are commonly performed during Bluetooth device transmitter testing:

• Transmit power measurements: Including maximum output power, maximum power density, power control range, and EDR relative transmit power.
• Transmit spectral measurements: Covering frequency range, 20 dB bandwidth, adjacent channel power, in-band spurious emissions, and out-of-band spurious emissions.
• Transmit modulation measurements: Assessing modulation characteristics such as frequency deviation, carrier frequency drift, carrier frequency error, EDR-carrier frequency stability, EDR-differential phase encoding, and EDR-differential error vector magnitude (EVM) or modulation accuracy.

Receiver Testing

The following tests are performed during Bluetooth device receiver testing:

• Sensitivity
• C/I (Carrier-to-Interference ratio) performance
• Intermodulation
• Maximum usable receiver level
• EDR- BER (Bit Error Rate) performance characteristics

Bluetooth Test Tools

The following table lists various Bluetooth test tools from reputable vendors and manufacturers, designed to meet conformance requirements for RF, PHYSICAL (baseband), and upper layers, including the MAC layer.