Envelope tracking using transient waveform switching shaping supply modulation

Summary Burst‐mode operation of power amplifier (PA) based on multilevel pulse‐width modulation (MPWM) has been frequently discussed as a potential solution to achieve higher efficiency in radio frequency (RF) transmitters. In this paper, a novel multilevel PWM modulator is proposed that utilizes adaptive triangular reference waveforms. As compared with conventional MPWM modulators, the proposed architecture provides significant wider design space such that the efficiency of system can be effectively optimized. A general transmitter architecture based on the proposed concept is analyzed in terms of power efficiency. Efficiency optimization procedures are presented according to input magnitude statistics. Based on the proposed modulator, an optimized 2.4‐GHz RF transmitter is designed in a 0.18‐μm complementary metal‐oxide‐semiconductor (CMOS) process. The circuit‐level simulations show that it delivers 25.8‐dBm peak output power with 46.1% peak efficiency. For a 20‐MHz worldwide interoperability for microwave access (WiMAX) signal with 8.5‐dB peak‐to‐average‐power ratio (PAPR), this transmitter achieves 28.8% (average) efficiency at 17.3‐dBm (average) output power with an error vector magnitude (EVM) of 2.97% rms.

Section: A Prototype Transmitter Design and Simulation Resultsmentioning

confidence: 99%

“…By substituting (19) into (8) and using (6), the average coding efficiency of the proposed RAMPWM modulator employing PWO is obtained as:…”

Section: State Optimization Of Rampwmmentioning

confidence: 99%

Power‐efficient burst‐mode RF transmitter based on reference‐adaptive multilevel pulse‐width modulation

Arian

Jannesari

2017

“…1 Many solutions have been presented in the literature to boost the efficiency at lower power levels of PAs. The Doherty amplifier 2 and envelope tracking (ET) 3 techniques are used for the linear PAs, while the concepts of envelope elimination and restoration (EER) 4 and linear amplification using nonlinear components (LINC) 5,6 are applied to the saturated or switched-mode PAs.…”

Section: Introductionmentioning

confidence: 99%

High dynamic range pseudo–two‐level digital pulse‐width modulation for power‐efficient RF transmitters

Arian

Jannesari

2018

Radio frequency (RF) power amplification based on pulse-width modulation (PWM) has been widely discussed as a potential solution to achieve higher efficiency in RF transmitters. A digitally implemented PWM introduces a large amount of in-band distortion due to spectral aliasing. In this paper, a novel memoryless PWM modulator with a built-in anti-aliasing filter is proposed that effectively reduces the in-band distortion in digital implementation. The spectral characteristics of the proposed PWM modulator as well as the statistical properties of its output PWM signal are analytically studied. The pseudotwo-level output of the proposed modulator provides the capability to compromise between the efficiency, linearity, and complexity of transmitter, based on the given design targets. The proposed PWM method benefits from a simple circuit implementation in both digital and RF sections of the transmitter.Moreover, it preserves the low distortion property at low oversampling ratios of digital baseband. Simulations, as well as measurements, verify the performance of the proposed method. low level of RF input signal, PA consumes no power, while at the high level, PA can be designed to work in saturated output power where it presents the best efficiency performance.Although PA in a PWM-based transmitter operates in its most power-efficient regions, converting RF magnitude into the pulse train generates a significant amount of unwanted frequency components in the output spectrum of PA. 17 As depicted in Figure 2, these spurs are located at integer multiples of PWM frequency ( f PWM ) around the RF carrier frequency ( f c ). The bandpass filter (BPF) in Figure 1 is located at the output of PA to remove these undesired spurs and obtain the amplified version of the RF input. The quality of the signal recovered by BPF highly depends on the amount of distortion around the band of interest in the spectrum of RF PWM signal. The dynamic range (DR) gives a criterion to measure this type of distortion. It is defined as the ratio between the average power of the desired in-band signal and the power of the surrounding distortion, which is given in dB (or dBc). A sufficiently high DR is essential at the output spectrum of PA to satisfy the in-band signal quality and tight spectral requirements imposed by modern wireless standards. This is not feasible unless the RF PWM signal driving the PA itself benefits from excellent spectral characteristics.The spectral characteristics of the analog PWM (APWM) signal have been frequently studied in previous works. [17][18][19][20][21][22] An APWM signal occupies a wide bandwidth with a spectral content that tends to roughly roll-off as ∝ 1= f f PWM with increasing the frequency. By choosing a large enough PWM frequency, f PWM , of the APWM modulator, an arbitrary high DR could be theoretically achieved 19,21 at the cost of a wider output spectral bandwidth. Nevertheless, the practical achievable DR of the modulator is significantly restricted by the accuracy and bandwidth limitation of its analog ...

“…Series or parallel hybrid envelope modulators have been designed in several cases [12][13][14][15][16]. As shown in Figure 2a, in series hybrid envelope modulator, the switching regulator is used in series with the linear amplifier [11,17,18] to improve the efficiency. In Kim et al [17], an array of linear regulators are also used to further enhance the efficiency.…”

Section: Introductionmentioning

confidence: 99%

An adaptive digital processor for power efficiency enhancement in hybrid supply modulators

Salimi

Dehghani

Nabavi

2015

SUMMARYA novel digital envelope modulator for envelope tracking radio frequency power amplifier is presented in this paper. The proposed modulator consists of a parallel combination of linear class AB and switching class D power amplifiers that are controlled digitally. In the previous analog architectures, the requirements needed for the AB operational amplifier such as high-current driving capability, high bandwidth and large output swing is usually obtainable at high overall static power dissipation. The digitally controlled power opamp presented here not only provides the aforementioned requirements but also reduces power dissipation compared with previous work. Furthermore, the digital control of the modulator makes it adaptive to the input signal variations in comparison with conventional analog parallel hybrid envelope modulators. The digital processor of the modulator is evaluated with a 45-nm complementary metal oxide semiconductor technology. The overall power consumption of the digital processor is around 142 mW at 1.5-GHz clock frequency. As an application, the designed digital class AB is incorporated in a complete envelope modulator architecture. The overall efficiency of the modulator, including the digital processor power consumption, is around 82% at an average 32 dBm output power for a 5-MHz input signal.