Analogue predistortion lineariser control schemes for ultra‐broadband signal transmission in 5G transmitters

Abstract

Analogue predistorter (APD) has gained a new significance due to the need for high bandwidth in the fifth generation (5G) communication. As predistorted signal is generated in the analogue domain, it is free from data converter bandwidth limitation and presents an attractive linearisation solution for power amplifier (PA) in the 5G base station. Furthermore, it also finds its application in the multicarrier repeater system for long‐distance communication, where the baseband information is not readily available. However, the performance of the conventional APD is dependent on the appropriate control of gain and phase of the predistorted signal. The state‐of‐the‐art work in analogue linearisation solutions mostly utilises vector multiplier for such a control. This work points out the limitations of such a scheme and proposes a novel control scheme (CS) that is capable of extracting better benefits of the APD. An experimental validation is carried out by linearising 10 W HMC8500 broadband GaN PA, excited by a eight‐component carrier 160 MHz ultra‐broadband long‐term evolution signal. The proposed Type‐II CS delivers an adjacent channel power ratio of −45.05 dBc with an improvement of 18 dB, which is 4 dB better than Type‐I CS.

Predistortion-Based Linearization for 5G and Beyond Millimeter-Wave Transceiver Systems: A Comprehensive Survey

“…Therefore, another variant of the PD scheme, known as analog predistortion (APD), with its wideband operating capability, can target the out-of-band (OOB) distortions more effectively than DPD [31]. Besides, APD can provide a high degree of freedom in its cost-effective analog techniques, comes in different typologies [32]- [37]. As a result, it is formidable in ultra-dense 5G BS-FEMs to employ a compact APD before each PA, significantly relaxing the digital hardware complexities and safeguarding the OOB spectral regrowth.…”

Broadband linearizer based on equivalent power‐dependent impedance function of diode and load match network

“…4,5 Vector modulator and vector multiplier are used for gain and phase control of the input signal to obtain excellent linearization performance. 6,7 In Reference 8, the admittance of forward and reversed diode are measured in different bias voltages to design the linearizer. However, these techniques aim at improving the design accuracy at a single frequency.…”

“…Spice model of diode is used to calculate the characteristic of the linearizer 4,5 . Vector modulator and vector multiplier are used for gain and phase control of the input signal to obtain excellent linearization performance 6,7 . In Reference 8, the admittance of forward and reversed diode are measured in different bias voltages to design the linearizer.…”

Complete analysis and design for a Q/V band (46‐52 GHz ) wideband analog predistorter

“…Therefore, different linearization methods such as feedback, feedforward, digital predistortion, and analog predistortion technique 2‐6 are widely employed to improve the linear characteristics of TWTAs. Owing to its wideband operation, and high frequency, analog predistortion is commonly used in microwave and millimeter wave systems 7‐16 .…”