Lin Maoliu

Design of two-channel hybrid analog/digital banks satisfying near-perfect reconstruction

In this paper, a novel method is presented to design two-channel hybrid filter banks satisfying near-perfect reconstruction. The analog analysis filters to divide the overall system bandwidth are not the low-pass, band-pass or high-pass filters by using conventional methods, but analog filters that satisfy the pairwise power complementary property derived from the perfect reconstruction property. And parameters of the analog analysis filters based on power complementary pair are optimized. The digital synthesis filters are designed by means of the optimization method based on IFFT to ensure the near-perfect reconstruction. A two-channel hybrid filter bank with 3rd-order analysis filters and 32nd-order FIR synthesis filters, which introduces 2.1/spl times/10-9 dB average deviation from 0 dB, distortion and -118 dB average aliasing, are suitable for systems up to 16 bits resolution. And the HFB, whose aliasing error is small enough at the low-frequency region, has 2.2/spl times/10-9 dB max deviation from 0 dB distortion and -110 dB max aliasing.

Minimum phase response reconstruction of sampling oscilloscopes based on the NTN calibration

This paper describes an algorithm for determining the minimum phase response of sampling oscilloscopes of a linear time-invariant response function from its magnitude. The procedure is based on Kramers-Kronig relations in combination with the harmonic phase response measurement of the NTN calibration. Although the truncation of the Hilbert transform gives rise to large errors in estimated phase, these errors may be approximated by using three basis functions. As an example, we got the minimum-phase response reconstruction of sampling oscilloscopes in the frequency domain; its frequency resolution achieves 1 MHz.

Characterization of harmonic distortion and memory effects for RF power amplifiers based on volterra algorithm

The characterization of RF power amplifiers can benefit from the classic Volterra series theory. As a frequency domain form of Volterra series, Volterra algorithm is constituted by Volterra basis and Volterra coefficients. In this paper, the process of extracting Volterra coefficients is proposed and simulated with the harmonic balance simulator. A five order Volterra algorithm has been used to predict time domain waveforms, and a better agreement has been achieved, contrasting with X-parameter model. As an application, two Volterra coefficients concerned with three-order intermodulations is useful for characterizing memory effects influenced by modulation bandwidth.

Nonlinear behavioral modeling and simulation of Rf device with memory effects based on Volterra series

This paper is aiming at making behavioral model of RF device by using Volterra series theory. When we consider the periodic input signal, the Volterra series will presents a discrete form. In this paper, a five-order nonlinear system is applied to derive the Volterra series expansions which can express DC term and harmonic components in frequency domain. The simulation shows that the performance of this behavioral modeling method is good, especially when higher order Volterra series expansion is used. We also conclude that the method given by this paper is valid to both small signal and large signal.

Bitrate allocation for 3-D wavelet video coder

Wavelet Transform Coding Scheme is very promising due to its high coding efficiency. The coder of this scheme provides the coded bit stream can be truncated at any point adapting to best effort delivery of network. In this work, we investigate R-D (Rate-Distortion) model for each subband based on statistical property of coefficients. Then, a constrained bitrate allocation method is derived by exploiting the R-D performance of the coder. Experimental results show that the proposed method can provides bitrate-distortion tradeoff, and achieves target bitrate allocation and guarantees both good subjective and objective quality.

X-parameter measurement and simulation of an RF amplifier designed to drive a comb-generator

X- parameters, referred to as the parameters of the Poly-Harmonic Distortion (PHD) nonlinear behavioral model as well, have been introduced as the natural extension of S-parameters to nonlinear devices under large-signal drive. This paper describes the approach and procedure of X-parameter characterization and nonlinear simulation of an RF amplifier designed to drive a comb-generator, including measurement experiment, modeling, and model validation. Firstly, a specially configured Nonlinear Vector Network Analyzer (NVNA) is used to the measurements. Secondly, the X-parameters are extracted. Then the parameters are used with the X-parameter framework in ADS to enable accurate nonlinear simulation of device behavior. Independent NVNA measurements validate the model predictions, and show the inadequacy of ‘Hot S22’ in predicting such performance.

Analysis of Spectral Regrowth on Forward-Link CDMA Signals Based on Fifth-order Nonlinear Distortion

In this paper, based on the time domain model of the forward-link CDMA signal, analytical expressions relating the spectral regrowth of the CDMA signal passed through a nonlinear amplifier with a digitally modulated carrier to both the third-order intercept point and fifth-order intercept point, IP3 and IP5, were derived using the power series and high-order cumulant. This statistical method considers the nonlinear transformation of statistical properties of moments of a complex Gaussian random variable to develop a simple expression for the autocorrelation of the output signal. Analytical results are useful in finding optimal operating conditions of the power amplifier. In the end, the comparison between the simulation and practical measurement show that a better fit using both IP3 and IP5 than using only IP3.

A novel envelope-domain approach for in-band intermodulation distortions characterization

To characterize the in-band intermodulation (IM) distortions of the microwave amplifiers, a novel prediction method based on the dynamic X-parameters theory is proposed in this paper. The proposed method describes the relationships between the input two-tone signal and the IMs products. Compared to the traditional approaches, it can accurately predict both the amplitudes and the consistent phase information of the output signals at all desired frequencies, which is an important supplement and extension to the theory of behavioral modeling. Benefit from the wideband detection of the pulse profile measurement, the in-band IMs products are sampled and down converted with the RF signal simultaneously in the NVNA. Therefore, it provides a possibility to distinguish each of the frequency spectrum products. Finally, the output spectrums of the RF pre-amplifier ZFL_11AD have been analyzed and verified based on the theoretical and practical measurements.

Fine frequency grid calibration and the experiment for NVNA based on squared crystal

This paper studies on the low phase resolution of the phase calibration of a mixer-based two-port coaxial Nonlinear Vector Network Analyzer (NVNA), especially the absolute calibration techniques. A new method of fine frequency grid calibration based on squared crystal detector has been made. The narrowband calibration principle of the way to calibrate the NVNA by using the squared crystal detector is deduced, and the calibration process is given. Simulation results of ADS and the experiment prove the effectiveness of the proposed method, and its phase calibration resolution achieves 100KHz.

Throughput maximization and interference power analysis based on sequential energy detector

One of the main challenges in cognitive communication is to minimize the interference to the primary user and maximize the throughput of second user. Sequential energy detection (SED) is a faster and lower complexity spectrum sensing technology. In this paper, we formulate an optimization problem to design the sensing parameter and optimize the transmitting power based on SED in order to maximize the second user throughput while avoiding the interference to the primary user under a threshold constraint. Through theoretical and numerical simulation analysis, we find that optimizing the transmit power and the sensing parameter play an important role in maximizing the second user throughput.