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Challenges in solid state power amplifier testing

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Author : AmpliVsionS
Update time : 2021-02-23 11:13:58

       Solid-State Power Amplifiers are very important components in wireless communication systems, which are mainly used to amplify the low-power RF signal generated by the modulation oscillator circuit to obtain enough RF output power to be fed to the antenna for radiation. But they are non-linear in themselves, which can cause spectrum proliferation and interfere with adjacent channels, and may violate out-of-band emission standards mandated by laws and regulations. This feature can even cause in-band distortion, which increases the bit error rate (BER) of the communication system and reduces the data transmission rate.

    Under the peak-to-average pow
er ratio (PAPR), the new OFDM transmission format will have more occasional peak power, making the PA difficult to be divided. This will reduce the compliance of the spectrum mask and expand the EVM of the entire waveform and increase the BER. To solve this problem, design engineers usually deliberately reduce the operating power of the PA. Unfortunately, this is a very inefficient method, because the PA reduces the operating power by 10% and loses 90% of the DC power.

      Most SSPAs nowadays support multiple modes, frequency ranges and modulation modes, making the test items more numerous. Thousands of test items are not uncommon. The application of new technologies such as crest factor reduction (CFR), digital predistortion (DPD) and envelope tracking (ET) helps to optimize PA performance and power efficiency, but these technologies will only make the test more complicated and extend significantly Design and test time. Increasing the bandwidth of the RF PA will increase the bandwidth required for DPD measurement by 5 times (maybe more than 1 GHz), resulting in a further increase in test complexity.

        According to the trend, in order to increase efficiency, SSPA components and front-end modules (FEM) will be more closely integrated, and a single FEM will support a wider range of frequency bands and modulation modes. Integrating the envelope tracking power supply or modulator into the FEM can effectively reduce the overall space requirement inside the mobile device. In order to support a larger operating frequency range, a large number of filter/duplexer slots are added, which will increase the complexity of mobile devices and the number of test items.