With the rapid growth of wireless data services, the continuous introduction of new air interface technologies, and market competition from WiMAX, UMTS faces challenges in supporting real-time data services and large data volume services, and needs to evolve. LTE features flexible spectrum usage, seamless interoperability with existing technologies, and low network deployment and management costs. Whether a new technology can survive and thrive in the market depends on the end-user's recognition of the technology, and the key is whether these technologies can meet the expectations of end users. Therefore, operators will conduct extensive testing on network devices and mobile terminals.
The RF test of the LTE terminal not only examines the indicators of the terminal radio frequency chip, but also tests the whole machine of the terminal to examine the performance of the whole machine.
The overall requirements for LTE terminal RF indicators are:
â— For transmitters, on the one hand, it is required to accurately generate LTE useful signals that meet the standard requirements, and on the other hand, it is required to control the unwanted emission and interference levels within a certain level.
â— For the receiver, it is required to be able to receive and demodulate useful signals reliably and accurately under certain environmental conditions, and also to be able to withstand certain interference signals.
The LTE terminal RF test project is divided into four parts, namely, transmitter indicators, receiver indicators, performance requirements, and channel status information reporting. Although the LTE signal structure is different from UMTS, the LTE terminal RF test requirements basically come from the UMTS defined RF requirements, and only a small number of new test items are added. In terms of receiver and performance statistics, the UMTS system measures reception performance by BER and BLER, while the LTE system is measured by throughput. In the performance test part, the channel demodulation performance index is also added for the channel structure of LTE. In addition, for the LTE terminal RF test, it is necessary to test multiple bandwidths, multiple RB configurations, and multiple modulation modes supported by the terminal, and the test amount is also very large. The following is a brief description of most of the four test items.
(1) In the transmitter indicator, the following types of test items are included:
â—Transmission power related items
For example, the maximum output power of the UE, the maximum power backoff (MPR), and the configuration power of the UE. These test items are mainly to check whether the transmission power of the terminal meets the standard requirements. If the maximum transmit power of the terminal is too large, it will cause interference to other channels or systems. If the maximum transmit power is too small, the system coverage will be reduced. The maximum power backoff is a new test item, which will be analyzed in detail later.
â—Output power dynamic range
Such as minimum output power, transmit power, switching time template, etc. These test items mainly focus on whether the output power range of the terminal meets the standard requirements. If the minimum output power and shutdown power are too large, it will cause interference to other terminals and systems. The switch time template verifies whether the terminal can accurately turn on or off its transmitter, otherwise it will cause interference to other channels or increase the transmission error of the uplink channel.
â—Power control
Such as absolute power control tolerance, relative power control tolerance and so on. The purpose of power control is to limit the interference level of the terminal and compensate channel fading. This part of the test is mainly to verify whether the terminal can correctly set its transmit power, and the transmit power is within a certain tolerance range.
â—Signal signal quality
Such as frequency error, error vector magnitude EVM, carrier leakage, in-band emission of unassigned RB, spectral flatness of EVM equalizer, etc. The quality of the transmitted signal of the terminal is a very important indicator to examine the modulation performance of the terminal transmitter. We know that OFDM systems are sensitive to frequency offset and phase noise. The method of OFDM technology to distinguish each subchannel is to utilize the strict orthogonality between each subcarrier. The frequency offset and phase noise will degrade the orthogonal characteristics between the subcarriers, causing the performance of the LTE system to degrade. Therefore, frequency error, EVM, carrier leakage (IQ imbalance), etc. are indicators that LTE terminals must examine.
â— Output RF spectrum emission
Such as occupied bandwidth, spectrum emission template, adjacent channel leakage power ratio (ACLR), transmitter spurious radiation. The useful spectrum emission of the terminal must strictly comply with the standard requirements, while the out-of-band emission and spurious emission are unwanted emission, and more strict restrictions are required, otherwise it will cause serious interference to other users' systems.
â—Transmitting intermodulation
When two or more frequencies of RF signal power appear in a passive RF device at the same time, passive intermodulation products are generated. Generally, the third-order intermodulation is the most serious. The test principle of transmitting intermodulation is to set the terminal to be at the maximum transmission power. After configuring the interference signal, it is necessary to observe whether the intermodulation product exceeds the standard in the frequency band. The ratio of the useful signal and the intermodulation product power (in dBc) is lower than the limit. This test project is mainly to verify the ability of the terminal to suppress its intermodulation products.
(2) In the receiver indicator, the following types of test items are included:
â—Reference sensitivity level
Investigate the ability of the terminal to receive small signals. If the terminal sensitivity is too low, it will reduce the effective coverage of the eNodeB.
â—Maximum input level
Investigate the ability of the terminal to receive large signals. If the terminal's maximum input level fails, it will reduce the coverage of the eNodeB's near-end.
â— Adjacent channel selectivity, blocking characteristics, spurious response, and intermodulation characteristics
The above categories are to consider the receiving performance of the terminal in the presence of interference signals (mono/dual/modulation interference). If the terminal's anti-interference ability is too poor, the terminal receiver performance will be degraded.
â— stray radiation
The ability of the receiver to suppress the power of spurious signals generated or amplified in the receiver is examined.
For more LTE related articles, please refer to the electronic enthusiasts Designs of week column - "Resolve 4G quality problems? LTE test out!"
TM1914 Digital LED Strip is a double signal transmission led strip,mainly use in 5050RGBWW 5in 1 led strip,the TM1914IC is outside on the strip,
To achieve the Digital and dimmer color by a extend controller . More functions can to change the range of digital color,
the Color Temperature is range of the 2600-6500K. Meet the needs of different scenarios.
TM1914 Digital LED Strip
Rgbw Led,Tm1914 White LED Strip Light,TM1914 LED Strip,TM1914 Digital LED Strip
SHEN ZHEN SEL LIGHTING CO.,LTD , https://www.sel-lighting.com