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Energy efficiency has been a growing requirement in the latest development of wireless communication systems, and it has led to research on off-grid relay nodes with simultaneous wireless information and power transfer (SWIPT) capabilities. Two SWIPT protocols have been developed in the past, named power splitting and time switching. Both protocols have been theoretically proven to improve energy-constrained...
We present the design of a low-noise amplifier (LNA) with high-gain and differential output suitable for Long Term Evolution (LTE) receivers front-ends operating in 700 MHz band. The circuit, built in 130 nm CMOS technology, occupies an area of 453 × 259 μm2 (without pads). The LNA is powered with 3.3 V and consumes a current of 6 mA (core). It reaches a power gain of 24.98 dB with a maximum noise...
A design of a MOS Gilbert mixer cell intended for LTE band 28 is presented in this work. The objective is directed to a design with low noise and low third-order intermodulation distortion. The designed mixer can be used in a fully-differential chain, avoiding the implementation of a balun. Since the overall IP3 of a full front-end depends on the IP3 of the each stage, specially those behind the low-noise...
A complex-allpass-based multiple notch IIR filter is proposed to suppress Radio Frequency Interference (RFI) that affect VDSL systems. A notch filter realization based on complex allpass cascaded second-order sections is presented and evaluated in this paper. Two different algorithms, using the Recursive Prediction Error (RPE) method and an alternative (similar to the Steiglitz-McBride) method, are...
We present a prediction-based resource allocation algorithm (RA) for OFDMA downlink over mobile wireless channels, where prediction errors are incorporated in the problem formulation. A solution based on the empirical characterization of the prediction error is proposed. We test the proposed scheme on a realistic scenario using a practical low complexity channel predictor, suitable for implementation...
Nonlinear effects of a power amplifier (PA) in communications systems include spectral spreading, which causes adjacent channel interference. For predistorter design, it is crucial to employ a model that can sufficiently model the intermodulation distortion (IMD) caused by the PA. The order of IMD generated by a polynomial is determined by its highest order basis. For a piecewise linear function,...
We propose two practical schemes for the cancellation of nonlinear distortions caused by the power amplifiers (PA) in Orthogonal Frequency Division Multiplexing (OFDM) systems. The algorithms are iterative and located at the receiver. They utilize a soft channel decoder to improve the capabilities of the distortion estimation and relay all the computational complexity to the receiver. Simulation results...
We present an approach for compensating nonlinearities in a continuous-time (CT) first-order sigma-delta converter (SDC) with one bit quantization. A reduction of an order of magnitude is obtained in the measured squared error when compared to the uncompensated SDC. Our results confirm a significant improvement in Signal to Noise and Distortion Ratio (SINAD) for single tone input signals and in Spurius...
The extension of OFDM to multiuser structures like space division multiple access (SDMA) helps to increase the spectral efficiency and system capacity. However, power amplifier nonlinearities reduce severely the performance due to the high peak to average power ratio (PAPR) that is a typical characteristic of multicarrier systems. This paper derives a theoretical upper bound on the bit error rate...
This paper formulates in a common framework some results from the fields of robust filtering, function approximation with orthogonal basis, and adaptive filtering, and applies them for the design of a general deconvolution processor for SISO systems. The processor is designed to be robust to small parametric uncertainties in the system model, with a partially adaptive orthogonal structure. A simple...
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