چكيده به لاتين
With the rapid growth in modern communication systems such as Massive MIMO and the significant increase in the transmitted data rates and the volume of RF / Microwave circuits, reducing the price and power consumption and integrating transmitter blocks is become one of the strategic needs. In addition to this, in analog / hybrid beamforming, many RF modules are needed to drive each antenna element, including phase shifter, power amplifiers (PAs), and linearization circuitry. However, implementing these systems with the DPD linearization method is not cost-effective. Therefore, integrating a phase-shifter and PA with its linearization circuitry in any RF path with adjustability in a wide frequency bandwidth and power range can be a good option. For this purpose, a new method of PA linearization based on the second harmonic signal injection is proposed in this thesis, which can help the PA achieve the required linearity even driven with modern broadband communication signals.
In order to evaluate the performance of the proposed method, the second harmonic generation (SHG) network using low power GaAs transistors with the ability to adjust the amplitude and phase of the injection signal in a feedback path was designed and fabricated with a 10 W class AB GaN PA in the 1.4 GHz to 1.6 GHz frequency band. As a result, the IMD3 of the PA was improved by 35 dB at 4 dB output back-off (OBO). Moreover, its ACPR was improved by 8 dB (at dB-3 saturation point) and 15 dB (at 4 dB OBO) when driven with an 8 MS/s 64-QAM modulated signal. Power efficiency was also significantly improved by at least 25% at a similar IMD3 or ACPR level of PA.
Also, the integrability of the proposed method with the PA was investigated by embedding GaN amplifiers in the SHG network, and outstanding results were obtained.
In another design, to evaluate the ability of the SHG network to improve the power and efficiency of the PA at the 1-dB saturation point rather than linearity improving, a three-port linearizer circuit including the SHG was built independently. According to OP1dB measurements, the OP1dB increased from 33.5 dBm to 39.5 dBm, and its efficiency increased from 27% to 46%. Also, in the 5 dB OBO, the IMD3 was improved by 39 dB. According to the results of the modulated signal test at 6 dB OBO, ACPR was improved by 16 dB, 14 dB, and 15 dB at the frequencies of 1.4 GHz, 1.5 GHz, and 1.6 GHz, respectively.
