Introduction to Bluetooth wireless testing

Introduction to Bluetooth wireless testing

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This article discusses the indicators and methods of Bluetooth wireless testing, and briefly introduces the anli bluetooth wireless testing solution.

Key words compatibility test wireless testing RF indicator bluetooth wireless Tester

　
To obtain the Bluetooth trademark, the Bluetooth product manufacturer must hand over the Bluetooth Product to the bqtf (Bluetooth certified Testing Device) for testing and send the testing results and products to bqb for review.
Query. Bluetooth Authentication is complicated. Each time a Bluetooth Authentication is performed, the applicant must pay a considerable fee to the bqrb (Bluetooth Certification Evaluation Board. Therefore, it is necessary for Bluetooth Product manufacturers to pre-configure Bluetooth
Authentication. Bluetooth testing includes compatibility testing and Connectivity testing. Bluetooth wireless testing is a compatibility test to verify that the RF performance of Bluetooth products complies with the Bluetooth RF specifications. Many OEM manufacturers have obtained direct purchase
Bluetooth-certified bluetooth chips or modules are used to develop Bluetooth products, such as mobile phones, personal digital assistants (PDAs), computers, printers, MP3 players, digital cameras, automobiles, and toys. Different Types
The requirement of the product may need to change the antenna, or because of the impact of other wireless modules or clock modules and power changes, these will lead to changes in the RF performance of the Bluetooth end product, therefore, R & D and production
During the process, the RF performance of the product must be tested to ensure that its wireless indicators comply with the requirements of Bluetooth RF specifications.

1. Bluetooth wireless testing methods and indicators

Currently
The Bluetooth wireless Test Specification Version is 0.91. It defines the bluetooth wireless test indicators and their testing methods. The Bluetooth wireless test configuration includes a tester and the tested device (EUT,
Equipment under
Test), in which the tester acts as the main unit and the EUT acts as the slave unit. The two can be connected through a RF Cable or through an antenna over the air. The tester sends the LMP command to activate the EUT
In the test mode, and configure some parameters of the bluetooth link between the tester and EUT. For example, whether the test method is loop back or send, whether the frequency hopping is required, whether the group is a single time slot group or multiple time slot groups,
The net bytes of the group are pn9, 00001111, or 01010101. The test mode is a special State. For security reasons, the EUT must first be set to the "enalle" state.
Before activation in the air to enter the test mode.

The following describes the bluetooth wireless indicators and test methods.

1.1 sender Test

(1) Output Power

　
The tester sets the initial status as follows: the link is frequency hopping, And the EUT is set to loop (Loop
Back ). The net charge sent by the tester is pn9, and the group type is the maximum supported group length. The EUT decodes the Group sent by the tester, and use the same group type to load the net back with its maximum output power
To the tester. The tester measures the peak power and average power in the entire burst range at low, medium, and high frequency points. The specifications require that the peak power and average power be smaller than 23dbm and 20dbm respectively and meet
The following requirements: If the EUT power level is 1, the average power>
0 dBm; if the power level of EUT is 2,-6dbm <average power <4dbm; if the power level of EUT is 3, the average power is <0dbm.

(2) power density

The initial state is the same as (1). the tester finds the highest-power frequency point within the MHz band by scanning the frequency point, and then performs a Time Domain scan (the scanning time is 1 minute) to measure the maximum value, it must be less than 20dbm/100 kHz.

(3) Power Control

The initial status is loop back, not frequency hopping. The EUT operates at low, medium, and high frequencies, and the return modulation signal is a dh1 group of pn9. The tester controls the EUT output power through LMP signaling and tests the range of the power control step. The specification must be between 2 dB and 8 dB.

(4) Frequency Range

　
The initial state is the same as (3). the tester performs scanning measurement on the dh1 group with the Net Load returned by EUT as pn9. When the EUT works at the lowest frequency, the tester finds that the power density drops to-80dbm/Hz.
Frequency FL; when the EUT works at the highest frequency, the tester finds the frequency FH when the power density drops to-80 DBM/Hz. For systems with 79 channels, FL and FH are required to be located
2.4 ~ Within the range of 2.4835ghz.

(5) 20 dB bandwidth

The initial status is the same as (3). The EUT operates at low, medium, and high frequency points, and the send-back modulation signal is a dh1 group of pn9. The tester scans the frequency points corresponding to the maximum power, and finds the FL and FH corresponding to the left and right sides of the tester when the power is reduced by 20 dB, 20 dB bandwidth df = | FH-fl |, the DF is required to be less than 1 MHz.

(6) adjacent channel power

　
The initial status is the same as (3 ),
The EUT operation frequency is 3rd channel, 39th channel, and 75th channel respectively, and the return net load is the dh1 group of pn9. The tester scans the entire Bluetooth band and tests the power of each channel. Adjacent 2nd
The leakage power of the channel is less than-20dbm, and the leakage power of the adjacent 3rd channels and above is less than-40dbm. (7) modulation characteristics

The initial status is the same as (3 ),
EUT operates at low, medium, and high frequencies. The tester sends a Net Load of 11110000 to the maximum supported group length, and calculates the peak value and average value of the frequency offset for the EUT return group,
Marked as df1max
And df1avg. The tester sends a Net Load of 10101010 to the maximum supported group length, and calculates the peak value and average value of the frequency offset for the EUT return group, respectively, as df2max
And df2avg must meet the following requirements: At least 99.9% df1max meets 140 kHz <df1max
<175 kHz; at least 99.9% df2max 3115 kHz; df2avg/df1avg 30.8.

(8) initial carrier margin

The EUT is in the loop status, and the return net load is the dh1 of pn9 to the tester. The tester first sets the link to non-frequency hopping, And the EUT operates at low, medium, and high frequencies respectively, and then sets the link to frequency hopping. The tester calculates the carrier frequency f0 based on four guide codes. The difference between the ftx and the nominal frequency is less than 75 kHz.

(9) carrier frequency drift

　
The initial status is the same as (3). The EUT operates at low, medium, and high frequencies, and the send-back modulated signals are 10101010 dh1/DH3/DH5 groups. The tester calculates the load according to four guide codes.
The wave frequency f0 is tested every 10 bits. The difference between the frequency and the initial carrier frequency is instantaneous frequency drift. Finally, the tester turned on the frequency hopping and re-tested the instantaneous frequency drift at all frequency points. Instantaneous frequency drift
The difference is defined as the drift rate. For dh1 groups, the instantaneous drift of each operation must be less than 25 kHz. For DH3 And DH5 groups, the instantaneous Carrier Drift must be less than 40 kHz. The specification also requires Carrier
The drift rate is less than 4000Hz/10 μs.

1.2 test the receiver

The above describes the wireless indicators of the Bluetooth sender and their tests. Test the receiver
All indicators are tested based on bitrate error statistics, and at least 1600000 bits must be counted. As we all know, it is meaningless to calculate the bit rate when the frame rate is large. Therefore
To accurately test the performance of the receiver, the tester must be able to test the fer caused by the following six conditions: CRC error, incorrect Net Load Length, synchronization word error, Hec error, EUT to mt8850a
The Nack group does not receive the EUT group within the expected time slot. The following describes how to test a bluetooth receiver.

(1) single time slot sensitivity

Chu
The initial status is the same as 1.1 (3). The EUT operates at low, medium, and high frequencies, and the return modulation signal is a dh1 group of pn9. According to the requirements of Bluetooth specifications, the tester controls its output power to enable EUT
The receiving power is-70dbm. The Bluetooth specification allows the RF signal sent by EUT to have an initial error of 75 kHz and a frequency drift of 40 kHz, that is, a total of an error of 115khz is allowed. In addition,
The error caused by modulation and symbol timing should also be considered. If the performance of the EUT receiver is tested by a tester that outputs "perfect" signals, the test results are insufficient to provide redundancy to adapt to the real wireless transmission ring.
The user will get an error about the quality of the receiver. Experience tells us that for a disturbance test, the sensitivity of the bluetooth receiver may deteriorate by 4 ~ 10 dB, specific value and group length, and Bluetooth chip type
. The tester must support dirty.
Transmitter), see Table 1. Add interference to the sent Bluetooth signal, every 20 ms, from the first group to the tenth group, and then return to the first group, repeated. In addition, the Bluetooth baseband signal
It is also modulated by a sine wave. The tester collects statistics on the error rate. The error rate must be less than 0.1%. In addition, if there are conditions, it is best to test again in the frequency hopping status.

(2) multi-time slot sensitivity

It is similar to the sensitivity test of a single time slot, but the group type is DH3 And DH5.

(3) c/I Performance

The initial status is the same as 1.1 (3), and The EUT operates at low, medium, and high frequencies respectively. The tester sends a valid signal to the dh1 Group of the net-mounted pn9 and a Bluetooth interference signal of the net-mounted pn15. For the power levels of useful and interference signals, see table 2. The tester performs error rate statistics, and requires ber <0.1%.

(4) Blocking Performance

　
Blocking refers to the ability of the receiver to receive useful signals when large interference signals exist in other frequencies. The initial status is the same as 1.1 (3), and The EUT transmission frequency is 2460 MHz (Channel 58 ). Test
The device not only sends dh1 groups with pn9 net load as useful signals, but also sends Continuous Wave Interference signals between 30 MHz and 12.75ghz. The power level of useful signals is higher than the reference sensitivity
3 dB, reference sensitivity refers to the minimum level that the receiver can receive when a certain bit error rate is met. The level of the interference signal is 2db larger than that given in table 3. The tester calculates the error rate. If Ber>
0.1%, the tester records the frequency of the interference signal at this time, and requires that the number of frequency points be less than 24. Other conditions remain unchanged. Only the level of the interference signal is reduced to-50dbm, And the tester records the Ber>
The frequency of the interference signal at 0.1% must be smaller than five.

(5) intermodulation Performance

Mutual adjustment refers to the existence of two or more
The ability to receive interference signals that have a specific frequency relationship with useful signals (their intermodulation products fall within the useful signal band. The initial status is the same as 1.1 (3), and The EUT transmission frequency is the same, which is low
, Medium, and high frequency. The tester not only sends dh1 groups with pn9 net load as useful signals, but its power ratio is 6db higher than the reference sensitivity. Moreover, the tester sends sine wave interference with-39dbm power and F1 frequency.
Signal, and Bluetooth interference signals modulated by pn15 with-39dbm power and F2 frequency. The difference between F1 and F2 is exactly equal to the receiving frequency of EUT, and F2-F1
= 3 MHz, 4 MHz, or 5 MHz. The error rate of the tester, which must be less than 0.1%.

(6) maximum input level

The saturation level of the bluetooth receiver. The initial state is the same as 1.1 (3), and EUT works at low, medium, and high frequency points. The tester sends a dh1 group signal with a net load of pn9 and controls its transmit power so that the level at the entrance of the EUT receiver is-20dbm. The error rate of the tester, which must be less than 0.1%.

In addition, both the receiving and sending devices need to test out-of-band stray power. That is, according to the ETS or FCC standard, the EUT is in the working and standby states, 30 MHz ~ Out-of-band stray in the 12.75ghz frequency range, including antenna transmit stray and chassis radiation stray.

2 bluetooth wireless Tester

　
The above describes the basic indicators for Bluetooth wireless testing. As a Bluetooth tester, the tester must meet the following requirements: to establish a bluetooth link with EUT, the tester must have a Bluetooth protocol stack; for Bluetooth wireless testing, testing
The test instrument must fully support the Bluetooth test mode protocol. It must be able to perform 1600 frequency hops per second. It must support "Dirty transmitter ".

Alibaba Cloud launches
The Bluetooth wireless tester mt8850a fully meets the above requirements. It complies with the latest bluetooth wireless Test Specification Version 0.91 and can test eight bluetooth wireless indicators: For the test output function of the sender
Rate, power control, initial carrier frequency, carrier frequency drift, and modulation. For the receiver, the single-time slot sensitivity, multi-time slot sensitivity, and maximum input level are tested. Mt8850a features accuracy, speed, and flexibility.
Mt8850a has a very fast testing speed and is used for typical testing on the production line. It takes only 3 s to test the four indicators of power, frequency, modulation, and receiver sensitivity, this improves the efficiency of the Bluetooth production line.
. You can edit the test script on mt8850a. The test script is a collection of Bluetooth test items. You can select a required test project and edit the test environment, such as the number of groups,
Frequency Hopping mode. Once mt8850a is configured, you can perform a single-key test. Just click "run ",
Mt8850a automatically creates a bluetooth link, activates the test mode, performs the test automatically, and reports the test results.

Me7865a is a pre-certification of Bluetooth Wireless Technology launched by anli.
System. You are currently applying for bqtf. It can test 16 wireless indicators specified by the Bluetooth RF specification. Me7865a is mainly composed of two mt8850a, one spectrum analyzer, one power meter and one
PC, composed of a RF switching box, and the instrument is connected through the GUI (universal interface bus). One mt8850a is used as the main tester, and the other mt8850a generates a Bluetooth interference signal.
Me7865a automatically Tests 16 Bluetooth RF metrics and generates a test report in Word format. You can submit the test report to bqb.