Highly efficient switched-mode transmitter using a current mode class-D RF amplifier

Abstract

This article presents a switched-mode transmitter architecture using a current mode class-D (CMCD) amplifier. To achieve high average efficiency for a modulated signal the envelope of the complex baseband signal is transformed into pulses such that the CMCD amplifier is operated either at its peak efficiency or completely switched off. The CMCD amplifier has been designed based on single-tone active harmonic load-pull measurements to achieve a power-added efficiency (PAE) of 61.5% with 25 W output power at 900 MHz using LDMOS FETs. Removing the losses of the demodulation filter and of the amplifier a 10% higher efficiency than in an ideal class-B amplifier can be obtained for burst-mode operation with a peak-to-average power ratio of 10 dB. V C 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE 20: 446-457, 2010.

A common drain parallel amplifier in GaN using baseband PWM and direct filter connection for efficiency enhancement

“…Trace η TH depicts the theoretical drain efficiency curve of the circuit in Fig. 3 according to (1), while trace η D shows the simulation results for a modulation frequency of 20.7 MHz. The difference between the two traces is attributed to the residual losses in the modulation sidebands and due to signal transitions.…”

“…A method which aims to improve the PA efficiency is baseband pulse width modulation (BB PWM) [1], [2]. Fig.…”

An RF Carrier Bursting System Using Partial Quantization Noise Cancellation

“…The efficiency measurements can therefore give insight into the intrinsic efficiency of the PA without having to solve the complex issue of integrating the output reconstruction filter with the PAs [25]. However, due to the highly idealized assumptions made for the class B model in III and the bandpass characteristics of the actual PA, accurate estimations of absolute η figures should not be expected.…”

“…Such M + 1-level topology generates a signal |S q,c [n]|, which envelope PDF is a Rician mixture of M +1 components, described in the same manner as (25) with…”

Radio frequency carrier amplitude‐burst transmitters – from architecture to circuit

“…The impact of the filter in the SMPA performance was identified in [11,12], with the observation that, with the used implementation, the out-of-band energy was reflected back to the amplifier. So, in order to protect the SMPA, the researchers inserted an isolator, at the expense of a substantial degradation of the system power efficiency.…”