Agilent’s RF test solution based on TD-SCDMA

In order to ensure the success of large-scale commercial use of China’s TD-SCDMA network, operators and equipment suppliers need to carry out a lot of testing work on network access equipment, among which radio frequency testing is particularly important. Agilent provides a comprehensive solution for TD-SCDMA RF testing that meets the requirements of 3GPP specifications, and has been widely used in various base stations, terminals, repeaters and other equipment testing. The following will introduce the solutions applied to receiver testing, transmitter testing (including repeater testing), RF conformance testing, and terminal calibration.

TD-SCDMA receiver performance index test

According to the RF conformance test specification requirements of 3GPP TS25.142 (base station) and TS34.122 (terminal), the wireless transmission and reception in TDD mode both define the corresponding transmitter and receiver and the performance of the system. Whether it is a base station or a terminal, most of the receiver test items are ultimately BER (Bit Error Rate) / BLER (Block Error Rate) tests.

Agilent’s N7612B Signal Studio for TD-SCDMA software, with signal generator ESG or MXG, provides a complete set of solutions for TD-SCDMA and TD-HSDPA signal generation, fully compliant with 3GPP and China Communications Standards Committee (CCSA) specification requirements. The advanced features of the N7612B provide fully coded test signals, ideal for performing receiver BER/BLER measurements on PRACH or DPCH channels. In order to isolate different receiver modules during the test, the data payload can be coded only on the physical layer, or can be coded on both the physical layer and the transport layer. In addition, S1/S2 rotation can be selected in DwPCH to test whether the terminal can correctly identify the P-*CH multiframe structure, mark the channel, or set different uplink transmission timing offsets in the UpPCH channel to check the module or system performance.

Agilent’s RF test solution based on TD-SCDMA

Figure 1 Base Station Receiver BER Test

Figure 1 shows an example reference of the Agilent test system applied to the base station manufacturer’s receiver BER test. The system has been successfully applied to the receiver performance verification test of many base station manufacturers such as Datang Mobile, ZTE, TD Tech and China Potevio. It has been widely used in the design and development of various base station manufacturers and the bidding and testing stage of operators.

In the test system shown in Figure 1, first select the corresponding RMC channel in the N7612B, and then set the waveform file trigger mode of the signal generator to calculate the BER/BLER at the receiving end of the base station through a dedicated test tool. In the actual field bidding test, generally another signal generator is used to generate multiple pre-configured interfering user signals or the AWGN signal generated by the signal generator itself is used to complete the performance index test of the receiver.

TD-SCDMA Transmitter Test Scheme

The radio frequency conformance test specification of the base station is mainly based on 3GPP TS25.142. Agilent’s PSA high-performance spectrum analyzer combined with the TD-SCDMA test suite (options 211, 212, and 213) provides a transmitter test program that conforms to the 3GPP standard. The test items of this series of options are all one-button measurement, which realizes automatic optimization of reference level and attenuation, eliminating the trouble of manual adjustment by users. In addition to the automatic test set according to the standard, this series of options also allows the user to change any parameter in order to meet the user’s special test needs.

The noise floor performance of PSA at around 2GHz can reach -167dBm/Hz, and the typical value is -169dBm/Hz, which fully meets the specification requirements of the spectrum analyzer for testing TD-SCDMA shutdown power -82dBm/1.28MHz, that is, DANL reaches -162dBm /Hz.

In order to measure the useful time-slot power up to +33dBm and the turn-off power below -82dBm at the same time, the PSA adopts the double sweep method, using the fast attenuator switch and the built-in preamplifier switch of the PSA, and using different time periods. Attenuator and preamp settings. The specific measurement method is: for the useful time slot of the large signal, set 40dB attenuation and turn off the preamp; for the shutdown power of the small signal, set the 0dB attenuation and turn on the preamp, and then fit the test result curve twice to get the real time template illustration.

Agilent’s RF test solution based on TD-SCDMA

Figure 2 Base station transmitter test

Using PSA’s TD-SCDMA test suite package can complete all base station transmitter test items, the system connection is simple (as shown in Figure 2), only the base station needs to provide reference clock signal and frame synchronization signal.

Agilent’s RF test solution based on TD-SCDMA

Figure 3 Repeater test

Figure 3 shows the system connection diagram of the test repeater. Since the TD-SCDMA repeater works in both directions, it is necessary to measure the uplink and downlink signals at the same time. Using MXG or ESG with special software (N7612B Signal Studio for TD-SCDMA) can configure and generate test signals (including DwPTS and UpPTS) with both uplink and downlink time slots open for repeater testing, using PSA’s TD-SCDMA test The kit (including options 211, 212 and 213) can analyze the output signal of the repeater.

The example shown in Figure 3 uses ESG or MXG with N7612B Signal Studio for TD-SCDMA software, not only can configure uplink and downlink time slots (including DwPTS and UpPTS) at the same time, but also can flexibly configure the code channel and spreading factor of each time slot , modulation method, power, midamble, and DwPTS phase rotation.

Agilent’s RF test solution based on TD-SCDMA

Figure 4 T D-HSDPA signal EVM measurement (16QAM)

PSA takes advantage of the synchronization characteristics of the midamble of TD-SCDMA, and provides users with the choice of two synchronization methods: pilot synchronization or midamble synchronization. In the absence of DwPTS, the midamble synchronization method can be selected, and the spectrum analyzer can still find synchronization and demodulate and measure EVM and PCDE. And PSA also provides ACLR, SEM, Tx Power, EVM, PCDE and other test items for non-service time slot-DwPTS/UpPTS.

ACLR, EVM and PCDE are measured in Test Mode 4 specified in the Repeater Test Profile, which is a three-carrier signal and only one carrier contains DwPTS. If testing the EVM of a specific time slot without DwPTS, the midamble synchronization method of PSA is required.

There are many test items about synchronous switching and time in the repeater test line, such as switching accuracy, rising edge time, falling edge time, etc. PSA’s launch time template provides such advanced test functions, users can use the expanded functional area of ​​the time axis to observe the details of rising or falling edges, and complete corresponding tests with functions such as Trigger Line, Burst Line and Ramp Line. In addition, the user can directly read the off power (Off Power) and Trig Delay Diff, and can change the delay between the Trig Delay Diff compensation trigger signal and the actual test burst signal.

Agilent’s RF test solution based on TD-SCDMA

Figure 5 RF Conformance Test System

HSDPA test

TD-HSDPA is the hot spot of TD-SCDMA network. The discontinuous pulse TD-HSDPA channel and multi-carrier signal pose great challenges to the measurement and verification of TD-SCDMA base station and terminal transceivers.

Agilent was the first to introduce a TD-SCDMA HSDPA test solution in 2006. Using ESG or MXG and PSA, TD-HSDPA’s ACLR, PVT, EVM, PCDE, etc. tests can be accurately and quickly completed, thereby significantly improving design and test efficiency. ESG or MXG with N7612B Signal Studio for TD-SCDMA software has powerful TD-HSDPA signal generation capability, supports TX/DTX, ACK/NACK/CQI configuration, and supports up to 12 carriers and data rates up to 2.8Mbps per carrier . PSA’s 213 option is an option specially designed for HSDPA testing. After selecting this option, users can perform EVM and PCDE measurements on 8PSK and HSDPA 16QAM signals, providing great help for users’ R&D and production.

Agilent’s RF test solution based on TD-SCDMA

Figure 6 Illustration of cell phone calibration measurement

TD-SCDMA RF Conformance Test Solution

For the performance testing of receivers, transmitters and channel simulation conditions specified in TS34.122, Agilent has launched the TD-SCDMA RF conformance test system, which fully supports the RF testing requirements specified in TS34.122.

Agilent’s TD-SCDMA RF conformance test system is built on Agilent’s standard wireless test management (WTM) software platform. The application software is mainly developed with VC, and some use VB to interface with WTM and programming interface, including three independent parts: test application program, system calibration program, and data query program. The application software fully considers the modular system structure, which is easy to upgrade and maintain. At the same time, it can be flexibly expanded to make the system adapt to the measurement needs of various wireless communication standards.

The test system integrates the latest Agilent RF instruments such as E4445A, E4438C, E8257D, etc., and supports the latest test functions of each instrument, such as the various TD-SCDMA test options mentioned above.

The RF interface box, the core equipment of the test system, is designed locally in China and manufactured in Malaysia. It consists of two parts: basic switching unit and dedicated filtering unit, which maximizes its flexibility. It can be integrated with Agilent GS8800 conformance test system or upgraded by itself to support other wireless technology formats such as GSM, WCDMA, and CDMA.

The test system implements the test cases specified in Chapters 5, 6, and 7 of TS34.122 and is used by national authorities for type approval.

TD-SCDMA mobile phone calibration application solution Mobile phone RF calibration mainly includes three parts: transmitter power calibration, receiver gain calibration and VCO (voltage controlled oscillator)/frequency calibration:

(1) Transmitter power calibration is to let the mobile phone transmit signals of different powers at different frequencies.

(2) The receiver gain calibration requires the comprehensive tester to generate and transmit standard signals at different frequency and specified power levels, and the mobile phone to measure the RSSI of the received signal strength, thereby calibrating the gain of the mobile phone receiving channel.

(3) There are two methods for VCO/frequency calibration: the first method is to let the comprehensive tester transmit the signal of the specified frequency, and the mobile phone adjusts its VCO according to the standard signal; the second method is to let the mobile phone transmit the specified frequency under the condition that it is not synchronized with the network The signal, the comprehensive tester measures its frequency error, so as to adjust the VCO of the mobile phone.

Table 1 Agilent signal source and spectrum analyzer test method

The E6601A is Agilent’s next-generation comprehensive tester platform designed to provide mobile phone manufacturers with a low-cost calibration solution. It adopts the open Windows XP platform, and users can directly develop, download and execute test programs on the tester, which greatly saves the space and cost of traditional test systems; its new measurement architecture specially designed for high-speed measurement and industry-leading precision, Repeatability and measurement integrity can significantly reduce mobile phone testing costs; its flexible license allows users to effectively reduce equipment costs and optimize resource utilization by purchasing license options that best suit their manufacturing needs.

Following Agilent’s introduction of GSM/GPRS/EDGE/W-CDMA/HSDPA/cdma2000/1xEV-DO calibration applications on the E6601A platform in 2006, Agilent launched the E6835A TD-SCDMA mobile phone calibration application this year. A brief introduction to the TD-SCDMA mobile phone calibration application:

Diverse and flexible signal source functions: E6835A can generate TD-SCDMA modulated signal, continuous wave signal (CW), amplitude modulated signal (AM), frequency modulated signal (FM) and double sideband suppressed carrier signal (DSB-SC), for different The different needs of chip manufacturers’ mobile phone calibration provide a strong guarantee.

Complete measurement functions: E6835A provides a variety of measurement functions in line with test standards, such as channel power (power test with RRC filter and power test without RRC filter), adjacent channel power ratio (ACLR), spectrum spurious (SEM), EVM, frequency error, peak code domain power, spectrum analysis, etc.

Dynamic power calibration function: In addition, E6835A also provides a fast calibration solution for mobile phone transmitters – dynamic power calibration function. It can complete the calibration of transmitter output power at different power levels on the same frequency at one time, thereby greatly improving the efficiency of mobile phone transmitter calibration.

Epilogue

Agilent provides a complete solution for TD-SCDMA RF testing to help users diagnose and locate faults. Table 1 summarizes the specific situation of Agilent’s vector signal source MXG/ESG and high-performance spectrum analyzer PSA, which can meet the specific conditions of the test items required by 3GPP specifications after configuring the TD-SCDMA test option respectively.

Source: Qingwu Seeking Dreams

The Links:   SKB52/08 LB104S02-TL01