Radio frequency multilevel switching mode power amplifiers with pulse-position and pulse-width modulation for efficient power amplification of broadband mobile communication signals

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Efficient and linear radio-frequency power amplifiers are a key component for the wireless and mobile connected world. Efficiency and linearity are antagonistic properties for the design of classical class A, B and C power amplifiers. A current method to increase the efficiency is envelope tracking, i.e. the supply voltage tracks the envelope of the RF output signal. Envelope tracking needs a fast and efficient supply voltage modulator. The design of such modulator is increasingly challenging for the mobile communication signals with bandwidths over 100 MHz. RF switching mode power amplifiers (SMPA), driven by binary signals, offer the opportunity to achieve high linearity and efficiency simultaneously. The amplitude- and phase information of the transmit signal is encoded into the pulse width and pulse position (PWP) of a binary signal by means of a PWP-modulator. Such PWPM signals can drive switching mode power amplifiers. But amplifier systems based on the PWPM and SMPA usually suffer from a limited amplitude dynamic range, as very short pulses can’t be amplified due to the limited rise and fall times of the SMPA output voltage. The main idea behind in the digital power amplifier system of this project is to encode the phase and the fine resolution of the amplitude into the pulse width and pulse position of a binary signal. This pulse-with and pulse-position modulated signal is fed to an efficient switching mode power amplifier. The course resolution of the amplitude will be encoded into few discrete output voltage- (VM-SMPA) or output current levels (CM-SMPA) of a multilevel switching mode PA. Compared to the envelope tracking system a fast supply voltage modulator is not necessary.The main goal of this project is to do research on high frequency multilevel-switching mode power amplifiers (ML-SMPA) in voltage mode and in current mode and to drive them with pulse width and pulse position modulated signals, in order to amplify high frequency signals with high dynamic range with high efficiency and high linearity.Three steps shall reach this goal. At first, new high frequency switching mode power amplifier circuit topologies in voltage- and current mode with several output signal levels are evaluated and designed in a 28 nm-FDSOI-CMOS technology. Then an existing pulse width- and pulse position modulator-IC will be used as driver for the designed multilevel-switching mode power amplifiers. Finally, mobile communication- and wireless signals with high bandwidth and high bandwidth efficiency shall be demonstrated by a amplifier system consisting of a FPGA as base band signal source, the existing PWPM-IC and the realized high frequency multilevel switching mode power amplifiers. The frequency range addressed in this project is between 450 MHz and 6 GHz and the targeted output signal bandwidth is up to 400 MHz.