Linearity Enhanced Wide-Bandwidth Pulse-Modulated Polar Transmitters for LTE Femtocell Applications

Chen, Jau-Horng; Yang, Hao-Shun

doi:10.1109/tmtt.2015.2504498

Cited by 13 publications

(14 citation statements)

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“…[7][8][9][10][11][12][13][14][15][16] In a conventional PWM-based transmitter, the magnitude of RF signal is converted into a two-level square wave with variable pulse-width. [7][8][9][10][11][12][13][14][15][16] In a conventional PWM-based transmitter, the magnitude of RF signal is converted into a two-level square wave with variable pulse-width.…”

Section: Introductionmentioning

confidence: 99%

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

Arian

Jannesari

2018

Circuit Theory & Apps

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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 ...

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Section: Introductionmentioning

confidence: 99%

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

Arian

Jannesari

2018

Circuit Theory & Apps

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“…In recent years, the concept of burst‐mode operation has been widely addressed as a promising approach toward highly efficient RF transmitters . In a conventional carrier amplitude‐burst transmitter, the RF magnitude is converted into a 2‐level square wave with variable pulse‐width.…”

Section: Introductionmentioning

confidence: 99%

“…In recent years, the concept of burst-mode operation has been widely addressed as a promising approach toward highly efficient RF transmitters. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] In a conventional carrier amplitude-burst transmitter, the RF magnitude is converted into a 2-level square wave with variable pulse-width. Two common techniques to encode the magnitude into a pulse-width are delta-sigma and pulse-width modulations which the latter is the focus of this paper.…”

Section: Introductionmentioning

confidence: 99%

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

Arian

Jannesari

2017

Circuit Theory & Apps

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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.

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“…The aliasing-Free PWM transmitter [71,[73][74][75] (AF-PWMT) eliminates the aliasing and image distortion by limiting the number of harmonics of the digital PWM signal. The block diagram of the AF-PWMT is shown in Fig.…”

Section: Aliasing-free Pwm Transmitter 421 Conceptmentioning

confidence: 99%

Pulse-Width Modulated RF Transmitters

Haque¹

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To my mother, father, and uncle (mamoo), AbstractThe market for wireless portable devices has grown significantly over the recent years. Wireless devices with ever-increased functionality require high rate data transmission and reduced costs. High data rate is achieved through communication standards such as LTE and WLAN, which generate signals with high peak-to-average-power ratio (PAPR), hence requiring a power amplifier (PA) that can handle a large dynamic range signal. To keep the costs low, modern CMOS processes allow the integration of the digital, analog and radio functions on to a single chip. However, the design of PAs with large dynamic range and high efficiency is challenging due to the low voltage headroom.To prolong the battery life, the PAs have to be power-efficient as they consume a sizable percentage of the total power. For LTE and WLAN, traditional transmitters operate the PA at back-off power, below their peak efficiency, whereas pulse-width modulation (PWM) transmitters use the PA at their peak power, resulting in a higher efficiency. PWM transmitters can use both linear and SMPAs where the latter are more power efficient and easy to implement in nanometer CMOS. The PWM transmitters have a higher efficiency but suffer from image and aliasing distortion, resulting in a lower dynamic range, amplitude and phase resolution.This thesis studies several new transmitter architectures to improve the dynamic range, amplitude and phase resolution of PWM transmitters with relaxed filtering requirements. The architectures are suited for fully integrated CMOS solutions, in particular for portable applications.The first transmitter (MAF-PWMT) eliminates aliasing and image distortions while allowing the use of SMPAs by combining RF-PWM and band-limited PWM. The transmitter can be implemented using all-digital techniques and exhibits an improved linearity and spectral performance. The approach is validated using a Class-D PA based transmitter where an improvement of 10.2 dB in the dynamic range compared to a PWM transmitter for a 1.4 MHz of LTE signal is achieved.The second transmitter (AC-PWMT) compensates for aliasing distortion by combining PWM and outphasing. It can be used with switch-mode PAs (SMPAs) or linear PAs at peak power. The proposed transmitter shows better linearity, improved spectral performance and increased dynamic range as it does not suffer from AM-AM distortion of the PAs and aliasing distortion due to digital PWM. The idea is validated using push-pull PAs and the proposed transmitter shows an improvement of 9 dB in the dynamic range as compared v vi Abstract to a PWM transmitter using digital pulse-width modulation for a 1.4 MHz LTE signal.The third transmitter (MD-PWMT) is an all-digital implementation of the second transmitter. The PWM is implemented using a Field Programmable Gate Array (FPGA) core, and outphasing is implemented as pulse-position modulation using FPGA transceivers, which drive two class-D PAs. The digital implementation offers the flexibility to adapt the transmitter...

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Linearity Enhanced Wide-Bandwidth Pulse-Modulated Polar Transmitters for LTE Femtocell Applications

Cited by 13 publications

References 13 publications

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

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

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

Pulse-Width Modulated RF Transmitters

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