Introduction to WiMAX and its power amplifier test solution
WiMax (Worldwide Interoperability for Microwave Access) is a wireless transmission technology based on the IEEE 802.16 standard. As a technology that connects users to the "last mile", WiMax was developed to replace broadband cable networks such as DSL and support mobile broadband wireless access. It uses OFDM transmission technology for non-line-of-sight (NLOS) connections, providing up to 75 Mbit/s data rate. Among them, the IEEE 802.16-2004 physical layer is divided into two modes: OFDM and OFDMA (Orthogonal Frequency Division Multiplexing). In OFDM mode, all carriers (200) are used for data transmission in TDD or FDD mode; in OFDMA mode, the number of carriers is significantly increased, and is divided into several self-channels (subchannelizaTIon), one or more for each user. A sub-channel that serves multiple users at the same time. IEEE 802.16e is mainly proposed for WiMax mobile applications. The number of carriers can vary significantly depending on the FFT base used (128, 512, 1024, 2048). The Korean standard WIBRO is a special case of 802.16e. Unlike WLAN, the bandwidth of a WiMAX signal is not fixed, but is variable between 1.25MHz and 28MHz.
Main test parameters of the power amplifier
For general-purpose power amplifiers, the main test parameters are:
(1) Power gain, reflecting the amplifier's ability to amplify the signal;
(2) 1dB compression point, reflecting the linearity of the amplifier, that is, the ability of the amplifier to amplify large signals;
(3) Maximum output power, in fact, the first two indicators can reflect the maximum available output power of the amplifier. They are tested with CW signals, as long as the signal source has excellent RF specifications and power scanning capability.
For WiMAX power amplifiers, in order to fully measure the performance of the amplifier, the following test parameters are often also of concern.
(4) “Burst†output power: divided into minimum RMS “burst†output power, average RMS “burst†output power and maximum RMS “burst†output power.
(5) Frequency error: The frequency error can be described by the carrier frequency error relative to the center frequency of the spectrum analyzer. The frequency error between the transceivers will cause the movement of each subcarrier spectrum relative to the receiver FFT frequency, resulting in inter-carrier interference (ICI), as shown in Figure 1.
Figure 1 Inter-carrier interference caused by frequency error
(6) Symbol clock error: refers to the difference between the reference symbol clock relative to the system sampling clock and the actual measured symbol clock. If the symbol clock is lower than the reference clock, the OFDM signal is longer than required, causing the subcarrier spacing to decrease; otherwise, the subcarrier spacing is increased. In both cases, inter-carrier interference is generated, which deteriorates the EVM performance of the signal.
(7) EVM (Error Vector Amplitude): This is one of the most important test parameters to ensure that the amplifier achieves good signal quality while outputting sufficient power. The EVM result can be for all carriers, data carriers, and pilot carriers.
(8) ACPR (adjacent channel power ratio): ACPR refers to the ratio of the power measured by the adjacent channel to the power of the main channel, reflecting the interference of the amplifier distortion on the adjacent channel.
(9) Spectrum flatness: Reflects the power variation of WiMAX signal subcarriers, which measures the deviation of the average power of each subcarrier from the average power of all subcarriers.
(10) Spectrum difference: measures the power difference between adjacent subcarriers in the burst preamble.
(11) Spectrum mask: measures the “profile†of the transmitter's transmitted spectrum to ensure that there is not excessive power transmission outside the main channel.
For the above (5), (8), (9), (10), (11), although the multi-carrier continuous wave function of the general R&S standard signal source can simulate a WiMax signal for measurement, it is often troublesome to adjust. Not accurate enough; for (4), (6), (7), real WiMax signals are required for measurement, especially EVM. Therefore, a source that generates WiMax signals is essential for WiMAX power amplifier testing.
R&S WiMAX Amplifier Test Solution
R&S provides fast, accurate solutions for WiMAX amplifier testing. The test setup is shown in Figure 2 and consists of three parts.
Figure 2 WiMAX Power Amplifier Test Solution
(1) Signal source: 802.16-2004-OFDM, WiMAX 802.16e OFDMA and WIBRO signals can be easily generated using SMU200A and optional SMU-K49, or SMJ100A and optional SMJ-K49. In addition to excellent RF and baseband performance, the SMU200A also features powerful fading simulation, which is more suitable for R&D.
(2) Spectrum analyzer: FSQ series spectrum analyzer and option R&S FSQ-K92 supports 802.16-2004-OFDM signal analysis; or FSQ and option FSQ-K93 support WiMAX 802.16e OFDMA and WIBRO signal analysis; FSL can also be selected The family of spectrum analyzers and options FSL-K92 supports analysis of 802.16-2004-OFDM signals.
(3) External PC software DemoMeas_WiMAX: Control signal source (SMU200 and SMJ100) and spectrum analyzer (FSQ and FSL) via GPIB or LAN. As shown in Figure 3, the user only needs to select the parameter to be tested in the left column, and the software can automatically complete the settings required for the test, and generate a test report at the same time.
Figure 3 DemoMeas-WiMAX Software Window
In addition, for the three standards of OFDM, OFDMA and WIBRO, the required test parameters are different, so the choices provided by DemoMeas_WiMAX for users are also different (refer to Table 1), which includes a series of setting files corresponding to these three standards. The user can choose to measure the uplink or downlink and edit these settings files as needed.
In short, as a leader in the field of wireless testing, Rohde & Schwarz's WiMAX power amplifier test solution is based on its excellent signal source and spectrum analyzer, which fully demonstrates the superiority of automated testing, with simple, fast and accurate features. Greatly improve the user's testing efficiency.
The utility model provides a disposable electronic cigarette, comprising: a hollow shell, the bottom of the shell is provided with a lower cover; the shell contains an atomizer, and the outer side of the atomizer is sheathed with a disposable cigarette A bomb, a microphone cover is arranged under the atomizer, a microphone is covered under the microphone cover, a battery is arranged on one side of the atomizer, and an upper cover is arranged on the top of the casing; The atomizer includes an atomizing corThe utility model provides a disposable electronic cigarette, comprising: a hollow shell, the bottom of the shell is provided with a lower cover; the shell contains an atomizer, and the outer side of the atomizer is sheathed with a disposable cigarette A bomb, a microphone cover is arranged under the atomizer, a microphone is covered under the microphone cover, a battery is arranged on one side of the atomizer, and an upper cover is arranged on the top of the casing; The atomizer includes an atomizing core, an oil-absorbing cotton sleeved on the outside of the atomizing core, and an atomizer outer tube sleeved on the outside of the oil-absorbing cotton. The disposable electronic cigarette provided by the utility model absorbs the smoke oil on the surface through the absorbing cotton, and then atomizes the smoke through the atomizing core, which greatly reduces the risk of oil leakage, at the same time, reduces the burning of cotton and ensures the smoking taste.e, an oil-absorbing cotton sleeved on the outside of the atomizing core, and an atomizer outer tube sleeved on the outside of the oil-absorbing cotton. The disposable electronic cigarette provided by the utility model absorbs the smoke oil on the surface through the absorbing cotton, and then atomizes the smoke through the atomizing core, which greatly reduces the risk of oil leakage, at the same time, reduces the burning of cotton and ensures the smoking taste.
disposable vape,vape pen,vape accessories,vape store,vape battery,e-cigarettes,Disposable Pod
Suizhou simi intelligent technology development co., LTD , https://www.msmvape.com