Agilent CDMA2000 Test Solution

1. CDMA2000 System Overview

The CDMA digital communication system originated in North America and developed by Qualcomm introduced a new communication concept. Today, CDMA has been extended to the third generation of mobile communication technology. Compared with traditional analog and ordinary second generation digital cellular technology, CDMA technology provides higher system capacity and spectrum utilization, and has voice quality close to that of wired systems, and the mobile phone radiation power is small.

New technologies are used in the CDMA2000 system. For example, the mobile station transmits the pilot channel; it uses true QPSK modulation, while in cdmaOne, two-way BPSK is used ; in addition, it uses higher-speed convolutional coding; when transmitting high-speed data services, it also uses TURBO coding with higher processing gain than convolutional coding; at the same time, both the forward and reverse links of CDMA2000 use closed-loop power control. Since the reverse link of CDMA2000 includes pilot, access, service, control and other channels, the use of OQPSK can no longer effectively reduce the peak-to-average ratio of the transmitted signal. In order to reduce the peak-to-average ratio of the reverse channel, HPSK modulation is used.

2. CDMA2000 test requirements

For CDMA/CDMA2000 mobile phone testing, the test standard IS-98E, which is the minimum performance requirement for mobile phones, is used. Mobile phone air interface testing mainly includes transmitter and receiver testing.

CDMA2000 base station testing includes system testing and component testing. System testing is also divided into transmitter and receiver testing. Table 1 compares the main test indicators of mobile phones and base stations.

Table 1 Comparison of main test indicators of mobile phones and base stations

Replenish:

1. Using the powerful modulation analysis function of the vector signal analyzer, including frequency domain, time domain, phase and vector diagram, constellation diagram, phase diagram, vector error and other in-depth analysis, the root cause of the problem or fault can be found.

2. Analysis instrument: Agilent 89600 series vector signal analyzer, or E4445A with 89601A vector analysis software.

3. The relative accuracy between the AWGN and CDMA signals of the Agilent instrument fully meets the requirements of the IS-98E standard (+/-0.2dB). In addition, the accuracy of the average power test meets the standard's requirement for 0.2dB accuracy of the instrument.

3. CDMA2000 system development process and Agilent's test solution

CDMA2000 research and development can generally be divided into four stages:

• System design and simulation stage
• Component/circuit/part design and verification stage
• System integration and joint commissioning phase
• Pre-certification and conformance testing phase

Different testing solutions need to be applied according to the different characteristics of different stages in the R&D process

3.1 System Design and Simulation Phase and Agilent Test Solutions

Agilent ADS (Advanced Design System) is an EDA tool specifically for electronic system and circuit design simulation. It can provide the most complete system and circuit computer and semi-physical simulation functions. By closely combining system design and hardware prototype, product design can be completed faster and more efficiently. ADS can be easily connected to Agilent Technologies' test instruments to realize virtual prototypes and perform semi-physical simulation. Agilent Technologies' ESG, E4406A, 89600, etc. can be used. Among them, the interconnection between ADS and E4438C and 89600 can greatly shorten the circuit simulation and design cycle and save R&D costs. By making full use of the powerful functions of ADS and other Agilent Technologies test equipment, you will get a new and efficient R&D solution that exchanges software design with hardware prototypes.

3.2 Component/Circuit/Part Design and Verification Phase and Agilent Test Solutions

After the system design and simulation verification, the stage of component selection, circuit and part design and verification begins. Even if the system design is completely correct, if the final product is to pass the strict consistency test, the baseband and RF device circuits must first meet more stringent requirements. The tests at this stage include both traditional linear and nonlinear analysis (such as S parameters, compression point, third-order intermodulation, etc.) provided by vector network analyzers and spectrum analyzers, as well as network analysis of new digital modulation excitation signals (such as CCDF, ACP, EVM, etc.) composed of digital signal sources and vector signal analyzers. This part is discussed in another article.

3.3 System Integration and Joint Debugging Phase and Agilent Testing Solutions

System integration and joint debugging are the core stages in the CDMA2000 R&D process. In this stage, the software and hardware of the transmitter and receiver must be jointly debugged, the key items of the whole machine must be generally verified, the high-level protocol must be functionally tested and signaling analyzed, and a large number of fault diagnosis and elimination must be performed. For this, Agilent can provide a complete solution, including the 8960W CDMA mobile phone comprehensive tester, E4438C digital signal source, 89600 vector signal analyzer and PSA series high-performance spectrum analyzer. ADS software can be used for semi-physical simulation at this stage.

The following is an introduction to the main test instruments used by Agilent in this phase of CDMA2000 development:

8960 Mobile Station Comprehensive Tester

E5515C is a truly multi-standard mobile station integrated tester. It not only supports CDMA2000 mobile phone testing, but also supports GSM, GPRS, EDGE, WCDMA, AMPS, IS-136, cdmaOne, CDMA20001xEV-DO, and other standards. It is truly multi-standard, supporting not only transceiver testing, but also protocol analysis, audio and spectrum analysis, with very high test accuracy and test speed, and only needs to be calibrated once every two years. Using 8960, you can accurately and authoritatively test mobile phones of various standards. For example, when testing CDMA and CDMA2000 mobile phones, the national standard and IS-98 standard stipulate that the relative accuracy of the test instrument's AWGN noise source and CDMA signal source must be within +/-0.2dB. 8960 is the only mobile phone integrated tester that fully meets this indicator.

The basic configuration of 8960 integrated tester is shown in the following table:

Figure 1

Table 2

E4438C Analog and Digital Signal Generator

The E4438C signal generator has excellent analog performance and provides a variety of digital modulation functions. They can not only generate standard W-CDMA , GSM , cdmaOne , CDMA2000 , CDMA2000 1xEV-DO, EDGE , NADC, PDC, DECT, PHS , TETRA signals, but also generate user-defined modulation signals. It supports receiver testing of base stations and mobile stations, and can generate multi-channel, multi-carrier CDMA signals. It can store ultra-long waveform data through 64M memory and 6GB hard disk.

Figure 2

Table 3

PSA Series High Performance Spectrum Analyzer

Agilent E4440A is a high-performance spectrum analyzer from Agilent. This spectrum analyzer is the first high-performance spectrum analyzer that uses all-digital intermediate frequency processing technology. Its test accuracy, dynamic range and test speed all represent the highest level of spectrum analyzers today. It can complete the test of transmitters of various standards, including the test of base stations and mobile stations of W-CDMA, GSM, cdmaOne, CDMA2000, CDMA2000 1xEV-DO, EDGE, NADC and PDC. In addition, PSA also provides the test of noise figure (NF) and phase noise. PSA can also be used as a downconverter. It provides an intermediate frequency output of 321.4MHz and 70MHz (option H70). The input frequency can be as high as 50GHz (E4448A) depending on the PSA model.

Figure 3

Table 4

89600 Series Vector Signal Analyzers

89600 is a powerful vector signal analyzer series. They consist of vector signal analysis software and RF and A/D front ends running on Windows2000 and Windows XP, and can be connected to a variety of instruments including VXI-structured RF and A/D modules, PSA series spectrum analyzers, ESA series spectrum analyzers, Infinium digital storage oscilloscopes, etc. The configuration is extremely flexible, with a frequency range of up to 26.5GHz and an analysis bandwidth of up to 80MHz. It has various flexible demodulation measurement capabilities and powerful vector analysis methods, supports various 2G, 2.5G and 3G standards, and is an important analysis and diagnosis tool in WCDMA research and development.

Figure 4

Figure 5

Channel fading simulator and digital input and output interface N5101A+N5115A+N5102A

Agilent's channel fading simulator consists of the baseband processing PCI card N5101A and the simulation software N5115A as shown below:

Figure 6

Figure 7

Agilent's channel fading simulator is a baseband-based simulator and has advantages over RF channel fading simulators:

• The software has pre-built-in fading parameters defined by various standards, which is very easy to use and does not require tedious item-by-item settings.
• There is no RF channel fading simulator to down-convert the RF signal and then up-convert it, so the signal is more accurate and pure.
• The built-in noise source is not attenuated and the C/N or Eb/No value can be set. This saves the cost of additional noise sources required for general simulators and avoids the tedious process of calibrating external attenuated signals and noise and the errors caused by it.