Digitally supported feed-forward harmonic cancellation for filter-less ultra-wideband transmitters

Rawat, Meenakshi; Roblin, Patrick; Quindroit, Christophe; Salam, Khan; Xie, Cheggang

doi:10.1109/imarc.2014.7038976

Cited by 15 publications

(10 citation statements)

References 5 publications

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“…where e k i is the error term for the i th neuron in the k th layer and f (net k i ) is the 1 st derivative of the activation function. For finding the convergence condition, one must minimize the error energy, which is given in (9). The backward computation is responsible for adjusting the bias and synaptic weights of the network.…”

Section: ) Backward Computationmentioning

confidence: 99%

“…In this algorithm, firstly, the network parameters are initialized. Then the average sum of square error is computed using (9). The updation of weights takes place by calculating the Jacobian matrix and the error gradient vector.…”

Section: ) Backward Computationmentioning

confidence: 99%

“…This digitally controlled harmonic cancellation techniques can omit the switched filter bank, as shown in Fig. 1, and result into filter-less multi-octave transmitter architecture [9]- [15]. This filter-less multi-octave transmitter architecture can present frequency agile and miniaturized solution in VHF/UHF bands particularly suitable for SDR application.…”

Section: Introductionmentioning

confidence: 99%

“…This filter-less multi-octave transmitter architecture can present frequency agile and miniaturized solution in VHF/UHF bands particularly suitable for SDR application. The harmonic modeling in [9]- [11] requires additional reference signals to be injected at the input of the PA. Therefore, to employ these models in feed-forward cancellation requires the signals injection at both the input and output at harmonic frequencies.…”

Section: Introductionmentioning

confidence: 99%

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Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Singhal

Rawat

2020

IEEE Access

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This paper presents and demonstrates the design of a filter-less transmitter architecture with digitally assisted harmonic cancellation. A neural network is used to model the harmonics as well as IMD for digital predistortion applications. This neural network-based harmonic modeling does not require any reference signal to be injected at the input of PA, thereby reducing the complexity in characterizing the harmonics. An in-house 10 W PA operating from VHF to L-band has been designed and characterized for its harmonic suppression. This PA is used along with agile RF transceiver AD9361 from Analog Device and Xilinx embedding platform using Zynq ZC-706 system-on-chip for implementing the entire transmitter. The receiver of AD9361 captures the nonlinearity of the PA in terms of harmonics as well as intermodulation distortion (IMD) components for modeling and predistortion. The proposed architecture can handle all types of distortions due to hardware as well as PA nonlinearity. Besides, it is also able to cancel the harmonics using a harmonic injection in the feed-forward configuration. This transmitter architecture has the advantages of being low cost, filter-less, wideband, frequency agile, reconfigurable and less bulky compared to the conventional scheme. The proposed scheme is demonstrated to transmit 5 MHz LTE signal at different frequencies over the range of 100 MHz to 400 MHz. In such a case, the second and third harmonics appear over the frequency range from 200 MHz to 1.2 GHz, which are within the amplification range of PA, yet they are suppressed without using any filter at the output. More than −40 dBc harmonic rejection is achieved over the entire operating range of this filter-less transmitter. The adjacent channel leakage ratio (ACLR) is always better than −45 dBc after applying digital predistortion.

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Section: ) Backward Computationmentioning

confidence: 99%

Section: ) Backward Computationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Singhal

Rawat

2020

IEEE Access

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“…Keeping this futuristic trend in mind, there had been very few recent attempts to model PA harmonics [27]. Harmonic cancellation feedforward techniques are proposed in [28] by injecting an uncorrelated signal at harmonic frequency, whereas [29] proposed a tunable third harmonic elimination technique for envelope-tracking amplifiers. However, to the best of the authors' knowledge, the interference of harmonics has not been studied in dual-band concurrent transmitters.…”

mentioning

confidence: 99%

Concurrent Dual-Band Modeling and Digital Predistortion in the Presence of Unfilterable Harmonic Signal Interference

Rawat

Roblin

Quindroit

et al. 2015

IEEE Trans. Microwave Theory Techn.

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Motivated by advanced-generation signals and corresponding trends for multiband, broadband, and ultra-wideband transmitters, several models have recently been proposed for digital predistortion in a dual-band concurrent transmission. These state-of-the-art models assume that two frequencies of operation are uncorrelated and harmonic products can be filtered out. However, when the harmonic of one signal falls on the frequency band of another signal, it cannot be removed with filters. This paper proposes a 3-D harmonic memory polynomial based model for the dual-band concurrent transmission in the presence of harmonic interferences. The model is extracted and predistortion is implemented using a low-cost field-programmable gate-array-based system including a transmitter and a feedback receiver. Using the proposed model, a performance improvement up to 22 dB in terms of normalized mean square error and performance improvement up to 20 dB in terms of the adjacent channel power ratio is achieved compared to a conventional dual-band memory polynomial model not including harmonics.

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Digital Techniques for Broadband and Linearized Transmitters

Rawat

Roblin

Koul

2020

Analog Circuits and Signal Processing

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Digitally supported feed-forward harmonic cancellation for filter-less ultra-wideband transmitters

Cited by 15 publications

References 5 publications

Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Digitally Assisted Harmonic Cancellation for Multi-Octave Filter-Less Transmitter

Concurrent Dual-Band Modeling and Digital Predistortion in the Presence of Unfilterable Harmonic Signal Interference

Digital Techniques for Broadband and Linearized Transmitters

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