| Beidou satellite navigation system of China provides global autonomous geospatial positioning services.In addition to the passive satellite navigation function,the first and third-generation Beidou satellite navigation systems also have radio determination satellite service that provides short message communication service and position reporting service,and the power amplifier is a key component in the RDSS satellite communication navigation terminal.The long-distance communication between the RDSS satellite communication navigation terminal and the satellite,the long battery life of the terminal and the high fidelity of the RDSS satellite signal require higher output power,higher efficiency,and higher linearity for the RDSS power amplifiers.Therefore,it is of great significance to research high-power and high-efficiency linearized RDSS power amplifiers.In this paper,a 5-watt RDSS power amplifier chip is designed with In Ga P/Ga As HBT process.The main research work and contributions of this paper are as follows:1.The current mirror structure is used to design an adaptive linearization bias circuit.With circuit-electronical simulation,the relative change rate of the base-emitter voltage of the HBT die at the first level is 8% in-20?4 d Bm of the input power,the relative change rate of the base-emitter voltage of the HBT die at the second level is 4% in-10?10d Bm of the input power,the relative change rate of the base-emitter voltage of the HBT die at the third level is 10% in-10?20 d Bm of the input power range;and the change rate of the collector bias current of the HBT die at all levels with temperature is 11.25%,1.4%,4.3% in-25?70? of the temperature range,which indicates that designed bias circuit can excellently reduce the bias point drift caused by temperature rise and input power increase.2.The RF predistortion circuit with gain expansion and negative phase advancement when the input signal power increases is designed to improve the linearity of the power amplifier.The circuit-electronical simulation indicates that the P1 d B of the RF predistortion power amplifier chip is better 2 d B than the power amplifier without RF predistortion circuit.3.The final HBT output matching circuit with high suppression of the second,third and fifth harmonics is designed.The circuit-electronical simulation shows that the losses of the second and the third and the fifth harmonics of the output matching circuit are 37 d B,50 d B and 32 d B respectively,which increase the power added efficiency of the power amplifier chip by 1.375%.4.Designed a LGA package of power amplifier,and the circuit,electromagnetic,thermal characteristics of the 4 mm×4 mm×1 mm packaged 5 watt power amplifier chip were simulated,and the circuit-electronical-thermal multi-physics co-simulation shows that the RF predistortion power amplifier chip works in 1.6?1.65 GHz,the linear gain is higher than 38.02 d B,and the gain flatness is lower than ±0.08 d B,and the input/output standing wave ratio is less than 1.22:1 and 1.98:1,and the P1 d B is 37.28 d Bm,and the saturated output power is higher than 37.84 d Bm,the saturated power additional efficiency is higher than 36.5%,the second,third,and fifth harmonic suppression ratio are better than-62.5 d Bc;at an ambient temperature of 70 ?,the maximum junction temperature is 193.74 ?,which indicates the HBT has a long service life,and the temperature of the bias and output matching circuit PCB is less than 128 ?,which is much lower than the maximum operating temperature allowed by the PCB,whch indicates that the power amplifier chip has high thermal stability.The 5-watt RDSS power amplifier chip researched and designed in this paper has the advantages of high linearity,high efficiency,and high thermal stability,which provides a valuable technical solution for the development of high-performance RDSS terminal power amplifiers. |
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