The polynomial model is commonly used in power amplifier (PA) modeling and predistorter design. However, the conventional polynomial model exhibits numerical instabilities when higher order terms are included. In this paper, we introduce a novel set of orthogonal polynomials, which can be used for PA as well as predistorter modeling. Theoretically, the conventional and orthogonal polynomial models are "equivalent" and, thus, should behave similarly. In practice, however, the two approaches can perform quite differently in the presence of finite precision processing. Simulation results show that the orthogonal polynomials can alleviate the numerical instability problem associated with the conventional polynomials and generally yield better PA modeling accuracy as well as predistortion linearization performance.

Orthogonal polynomials for power amplifier modeling and predistorter design

An amplifier system is provided that switches between a linear mode of operation, an envelope tracking mode of operation and a polar mode of operation. The amplifier system switches between modes of operation based upon a characteristic of an input signal relative to a first threshold level and a second threshold level. A mode selector selects the operation mode by transmitting an amplitude modulated signal plus a variable headroom voltage to a supply terminal of a power amplifier during the envelope tracking mode, an amplitude modulated signal to the supply terminal and phase modulated input signal during the polar mode and a substantially constant amplitude signal to the supply terminal during the linear mode.

Multi-mode amplifier system

An LCD groups pixels in each row into a plurality of blocks, and calculates difference in gray between every two image data applied to a pair of adjacent odd and even pixels in each block including pixels in a row for each of first to third colors. It is determined that a block is first or second dot block depending on a sign of the gray difference when a magnitude of the gray difference between the odd pixel and the even pixel in each pair in the block for at least one color is equal to or larger than a critical value. A current block in a current row and in columns is determined to be a one-dot block when the current block is the first dot block and a previous block in a previous row and in the columns is the second dot block. When the number of the one-dot blocks is a predetermined percentage of the number of the total blocks, it is determined that a one-dot pattern is generated and one-dot inversion of the LCD is changed into another inversion. In this way, a pattern generating flicker is determined and the inversion type is changed for reducing the flicker.

Liquid crystal display and driving method thereof

This paper presents two new algorithms for wideband spectrum sensing at sub-Nyquist sampling rates, for both single nodes and cooperative multiple nodes. In single-node spectrum sensing, a two-phase spectrum sensing algorithm based on compressive sensing is proposed to reduce the computational complexity and improve the robustness at secondary users (SUs). In the cooperative multiple nodes case, the signals received at SUs exhibit a sparsity property that yields a low-rank matrix of compressed measurements at the fusion center. This therefore leads to a two-phase cooperative spectrum sensing algorithm for cooperative multiple SUs based on low-rank matrix completion. In addition, the two proposed spectrum sensing algorithms are evaluated on the TV white space (TVWS), in which pioneering work aimed at enabling dynamic spectrum access into practice has been promoted by both the Federal Communications Commission and the U.K. Office of Communications. The proposed algorithms are tested on the real-time signals after they have been validated by the simulated signals in TVWS. The numerical results show that our proposed algorithms are more robust to channel noise and have lower computational complexity than the state-of-the-art algorithms.

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Wideband Spectrum Sensing on Real-Time Signals at Sub-Nyquist Sampling Rates in Single and Cooperative Multiple Nodes

The present invention, generally speaking, incorporates the power amplifier as a fundamental constituent of a modulator, using polar modulation techniques. Thus, it is possible to achieve the combination of precision signal generation (including envelope variations) along with high energy efficiency in combinations not possible heretofore. In accordance with one embodiment of the invention, a modulated radio (passband) signal generator produces high quality signals of general type, which specifically includes signals with varying envelopes. Signals are generated with high energy efficiency in the conversion of applied DC power to output RF signal power. The result is longer battery life for products such as mobile phone handsets. Dramatically improved efficiency also allows for a dramatic reduction (10 to 1 or greater) in the size of any required heatsink for the radio transmitter, which significantly lowers both cost and size. Furthermore, continuous operation of these radio transmitters is made possible with small temperature rises using small heatsinks, or even without any heatsink components. This provides for high operating reliability, as well as for greater throughput due to the longer operating time allowed. Another aspect of the invention allows the generation of high quality signals with wide bandwidth, without the need for continuous feedback during operation. This further reduces costs by greatly simplifying the design, manufacturing, and complexity of the transmitter circuitry.

High-efficiency power modulators

In this paper, we analyze the performance of spectrum sensing based on energy detection. We do not assume the exact noise variance is known a priori. Instead, an estimated noise variance is used to calculate the threshold used in the spectrum sensing based on energy detection. We propose a new analytical model to evaluate the statistical performance of the energy detection. We claim some characteristics of this model, and analyze how these characteristics affect the performance of spectrum sensing. The analytical results are verified through numerical examples and simulations. Through these examples, we demonstrate the effectiveness of our analytical model: we show how it can be used to set the appropriate threshold such that more spectrum sharing can be facilitated, especially when combined with cooperative spectrum sensing method.

Energy Detection Using Estimated Noise Variance for Spectrum Sensing in Cognitive Radio Networks

A method (200) and device (100) provide an efficient linear power amplifier that generates a variable-envelope radio frequency RF signal. The method includes the steps of: A) using an efficient envelope-following unit to output a supply voltage in accordance with a variable envelope of an input baseband signal, wherein using the efficient envelope-following unit includes: 1) using a bandwidth-limiting mapping unit to determine a reference signal based on the baseband signal; and 2) using an envelope-tracking power converter to output a supply voltage, responsive to the reference signal, to the linear RF power amplifier; B) providing an RF input signal with amplitude and phase information to a linear RF power amplifier; and C) using the linear RF power amplifier to output a power-efficient amplified variable-envelope RF signal with substantially a same amplitude and phase information as the RF input signal.

Method, device, phone and base station for providing envelope-following for variable envelope radio frequency signals

A power amplifier circuit for receiving a variable envelope input signal and for producing an amplified output signal is provided. The power amplifier circuit includes an envelope approximation circuit, an envelope amplifier circuit, a phasor approximation circuit, a quadrature modulation circuit, and a power amplifier. The envelope approximation circuit receives the variable envelope input signal and produces a bandlimited estimated envelope signal, corresponding to the amplitude of the variable envelope input signal. The bandlimited estimated envelope signal is then amplified by an envelope amplifier circuit. The amplified envelope signal is then coupled to the supply input of the power amplifer. The phasor approximation circuit receives the variable envelope input signal and produces a bandlimited estimated phasor signal. The quadrature modulation circuit receives the estimated phase signal and produces a modulated phase signal. The modulated phase signal is then coupled to the signal input of the power amplifier. The power amplifier then produces an amplified output signal.

Power amplifier circuit and method using bandlimited signal component estimates

Cognitive radios (CR) are proposed to alleviate the spectrum scarcity problems facing wireless service providers. In US, the FCC is considering spectrum regulation changes by allowing unlicensed operation in the TV broadcast bands provided that no harmful interference is caused. In this paper, we discuss the spectrum sensing aspects of cognitive radios. We particularly focus on the detection method based on cyclostationary spectrum density (CSD) estimation. The advantage of CSD is its relative robustness against noise uncertainty compared with energy detection methods. CSD estimation is a two dimensional transformation; therefore it is computationally complex. We transform the algorithm from the two dimensional space to a one dimensional case, therefore making the real time implementation more feasible. Through analysis and simulation, we identify the features with highest SNR to be used for CSD based detection. Based on the simulation results, we further propose dedicated hardware implementation architecture for CSD estimation using field programmable logic array (FPGA). Our implementation can achieve greater than 90% detection probability on BPSK signals with SNR of -18 dB, when the probability of false alarm is less than 10%.

Spectrum Sensing Using Cyclostationary Spectrum Density for Cognitive Radios

A device ( 400 ), method ( 1200 ), phone ( 400 ) and basestation ( 400 ) for providing scalar measurement-based predistortion for linearization in a radio frequency RF power amplifier, includes: a polynomial predistortion unit ( 406 ), coupled to receive an input baseband signal and polynomial coefficient weights, for predistorting the baseband signal to provide a predistorted baseband signal in accordance with the polynomial coefficient weights; an RF modulator ( 402 ), coupled to the polynomial predistortion unit ( 406 ) and to an RF generator ( 403 ), for modulating the predistorted baseband signal to provide an RF signal; an RF power amplifier ( 401 ), coupled to the RF modulator ( 402 ) and to a power supply ( 408 ), for amplifying the RF signal to provide an amplified RF signal, a scalar cost function generator ( 405 ), coupled to receive the amplified RF signal, for computing a scalar cost function; and a coefficient update unit ( 407 ), coupled to receive the scalar out-of-band-energy cost function, for tuning the polynomial coefficients in accordance with minimizing the scalar cost function to provide a linear amplified RF signal.

John Grosspietsch

Papers

Energy Detection Using Estimated Noise Variance for Spectrum Sensing in Cognitive Radio Networks

Method, device, phone and base station for providing envelope-following for variable envelope radio frequency signals

Power amplifier circuit and method using bandlimited signal component estimates

Spectrum Sensing Using Cyclostationary Spectrum Density for Cognitive Radios

Scalar cost function based predistortion linearizing device, method, phone and basestation