Changes in mobile communication terminal design
The value of mobile phone wireless communication is no longer so important, so the cost requirements for implementing it are getting lower and lower, and no one is willing to spend a lot of design, manufacturing and testing time for a communication chip of only a few dollars.
In order to meet various applications in different environments, designers have to put a variety of wireless technologies into small mobile phones, and to ensure stable and reliable performance. The technical difficulty of design and manufacture is constantly increasing.
New challenges in production testing
The production test process is usually divided into two stages: board test and final test. The board test calibrates the wireless module on the circuit board. The purpose is to write parameters to the original blank mobile phone board and adjust the difference in the overall RF performance of the mobile phone due to the differences between the individual components. The basic approach is to adjust the gain of the transmitter power amplifier by frequency and power level, adjust the frequency error of the baseband modulator, and adjust the gain of the low-noise amplifier at the front end of the receiver. The whole process is tested by the instrument and provides test signals. The final test is used to verify the quality of the calibration. The test instrument and the mobile phone under test first establish a voice call connection, and then the instrument measures the performance of the transmitter and receiver. In addition, some manufacturers will verify the voice quality or antenna radiation performance at this site. If the mobile phone supports technologies such as Bluetooth / FM / WLAN and GPS, then the function of the test station must be upgraded, and even a special test station is added.
Traditional processes are becoming increasingly unsuitable for the production requirements of complex mobile phones. Through observation, it can be found that the following factors in the traditional method have a greater impact on the test time: test software, control equipment and instrument initialization, mobile phone switch-on, calibration process, data interaction between the control software and mobile phone; call establishment; final test In the test of the BER of the mobile phone receiver; switching between frequency bands and standards.
With the advent of multi-mode mobile phones, the time required for testing has increased exponentially, which also means that the cost of testing continues to increase. The complete test time of a typical dual-mode mobile phone is generally 3 to 5 minutes, or even longer. At the same time, the addition of technologies such as Bluetooth / FM / WLAN and GPS has made the configuration and application of the entire test program, test fixtures, connecting devices and instruments more complicated.
Now major mobile phone manufacturers have begun to reform the original test mode, the purpose is only one, that is to reduce test costs and simplify the test process.
The following trends are increasingly clear in the field of testing.
Use non-signaling mode
In the traditional method, the actions of establishing a voice call, switching the system, switching between the test mode and the normal mode, and switching the machine on and off take a lot of time. The signaling action is to test whether the mobile phone executes the high-level protocol information correctly, and it can be transferred to the R & D stage for testing. Therefore, in the future, the final test will be performed in the non-signaling mode just like calibration. In the past, it was necessary to use the signaling mode to build the bit error rate test for the transceiver loop. With the improvement of the chip and instrument capabilities, it can also be completed under non-signaling conditions.
Pre-defined test steps and modes
Increase productivity
There is a lot of data interaction between the software and the mobile phone during calibration. The speed of the current instrument is very fast, such as the CMU200 of Rohde & Schwarz, a single power measurement only takes tens of milliseconds. However, the time required for a large amount of data interaction is much longer than the test itself, which forms a speed bottleneck.
Mobile phone chips have begun to become more intelligent. The test program only needs to send an instruction to the chip once, instructing the mobile phone to send a signal sequence of different power and frequency, and the mobile phone can continue to operate. At the same time, the instrument uses a technology such as intelligent calibration to perform a one-time test, thereby saving time. In addition, based on the capabilities of chips and instruments, engineers have also developed new applications for multi-system parallel measurement.
Use next-generation broadband wireless comprehensive tester
Due to design constraints, existing wireless integrated testers often cannot generate and analyze broadband signals, such as OFDMA modulation signals used in LTE and WiMAX technologies, nor can they process MIMO, WLAN / GPS / DVB / CMMB and other technologies. In order to meet the new testing needs, Rohde & Schwarz launched the CMW platform of broadband wireless comprehensive tester. The platform includes a series of products covering different needs such as protocol testing, R & D testing, and production testing. It has the advantages of large demodulation bandwidth, strong scalability, fast test speed, and full compatibility with previous technologies. All major mobile phone manufacturers have begun to use this new test platform.
Modulation technology, multiple access, duplex mode and measurement
The form of the wireless signal determines which test method should be used and the test results that can be obtained. Modern wireless communication systems are using complex digital modulation and multiple access technologies. For bandwidth, frame structure, modulation method, symbol (chip) rate, filter type, channel coding and error correction methods, many lower layers (usually For PHY, MAC and RLC layer) parameters have clear requirements, these parameters will affect the implementation of the test method. Of course, in order to facilitate the customer's use, the wireless comprehensive tester usually has a special test tool, which is customized according to the different characteristics of the signal.
Different wireless technologies have corresponding test specifications, such as GSM mobile phone test according to 3GPP 51.010, WCDMA mobile phone test according to 3GPP 34.121. But the production line usually does not need to test all items, otherwise the cost will be very large. Table 1 shows the test items commonly used in the general R & D stage and production line. These items can ensure the qualification of the most basic RF performance of mobile phones.
Table 1 Common RF test items
Moreover, with the development of technology, test specifications are also constantly adding new content. Like LTE, many projects are still being perfected. For example, the impact of MIMO technology on LTE terminal throughput and receiver bit error rate is still being explored by various terminal manufacturers. The CMW platform is currently the only solution in the industry that implements the LTE terminal signaling test function. Using this platform, many signaling actions of LTE base stations can be simulated to complete the early test of the terminal. CMW can also be expanded into an independent dual-channel meter to achieve MIMO traffic and receiver testing.
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