Direct downconversion of multiband RF signals using bandpass sampling

Abstract-Bandpass sampling can be used by radio receivers to directly digitize the radio frequency (RF) signals. Although the bandpass sampling theory for single-band RF signals is well established, its counterpart for multiband RF signals is relatively immature. In this paper, we propose a novel and efficient method to find the ranges of valid bandpass sampling frequency for direct downconverting multiband RF signals. Simple formulas for the ranges of valid bandpass sampling frequency in terms of the frequency locations of the multiple RF bands are derived. The result can be used to design a multiband receiver for software defined radios.     

A NEW QUADRATURE SAMPLING APPROACH FOR ARBITRARY BANDPASS SIGNAL WITHIN BASEBAND SAMPLING RATE

A new quadrature sampling technique for arbitrary bandpass signal within baseband sampling rate is presented. The input bandpass signal whose carrier frequency lies in the A/D baseband sampling rate is first decimated by factor 2 and modulated by (- 1)n, and then is interpolated by a linear phase FIR all-pass filter, finally the modulated complex envelope of bandpass signal can be produced.     

基带采样率内任意带通信号的正交采样

提出了一种在基带采样率内对任意带通信号的正交采样技术。载频位于ADC(模/数转换器)基带采样率内的任意带通信号,经1/2抽取和(-1)n调制,再由全通线性多相滤波器内插后,得到其复包络的调制输出XI(n)和XQ(n)。     

A modular multistage approach to digital fdm demultiplexing for mobile SCPC satellite communications

A hierarchical multistage method (HMM) for digital demultiplexing of an FDM signal composed of L adjacent SCPC signals is described; L is preferably a power of two, here L=32. This HMM approach to FDM demultiplexing applies bandpass sampling and is based on the processing of complex-valued signals by linear-phase FIR filters, where at any stage of processing the respective signals are always oversampled by two. The simulation results fully confirm the predicted system performance. An electrical demonstration model constructed by cascading six identical specially designed signal processors is being built.     

A blind SNR estimator for digital bandpass signals

A subspace-based blind Signal-to-Noise Ratio （SNR） estimation algorithm for digital bandpass signals in Additive White Gaussian Noise （AWGN） channel is discussed. The lower bounds of the mean and variance of the estimation are derived, and simulations are performed for the commonly used digital bandpass signals, such as MPSK （M=2, 4, 8）, MFSK （M=2, 4） and MQAM （M=16, 64, 128, 256） signals. Theoretical analyses and simulation results indicate that the proposed algorithm is effective even when the SNR is below 0dB. Furthermore, the algorithm can provide a blind estimator in that it needs neither the parameters of the received signals, such as the carrier frequency, symbol rate and modulation scheme, nor the synchronization of the system.     

导航信号的射频直接采样与数字下变频方法

研究导航信号的射频直接采样与数字下变频方法,并对1.2GHz和1.5GHz2个频点附近的导航信号进行了仿真验证。首先运用带通采样原理,选择合适的采样频率完成对导航信号的射频直接采样,然后结合积分梳状滤波器、半带滤波器,对采样后的信号进行抽取滤波,实现了降采样率的目的。最后,通过Matlab对5个频点的导航信号进行了仿真验证,完成了导航信号的射频直接采样并降低了采样率,恢复且分离了原始导航信号,从而验证了射频直接采样与数字下变频方法是可行的。     

Direct bandpass sampling of multiple distinct RF signals

A goal in the software radio design philosophy is to place the analog-to-digital converter as near the antenna as possible. This objective has been demonstrated for the case of a single input signal. Bandpass sampling has been applied to downconvert, or intentionally alias, the information bandwidth of a radio frequency (RF) signal to a desired intermediate frequency. The design of the software radio becomes more interesting when two or more distinct signals are received. The traditional approach for multiple signals would be to bandpass sample a continuous span of spectrum containing all the desired signals. The disadvantage with this approach is that the sampling rate and associated discrete processing rate are based on the span of spectrum as opposed to the information bandwidths of the signals of interest. Proposed here is a technique to determine the absolute minimum sampling frequency for direct digitization of multiple, nonadjacent, frequency bands. The entire process is based on the calculation of a single parameter-the sampling frequency. The result is a simple, yet elegant, front-end design for the reception and bandpass sampling of multiple RF signals. Experimental results using RF transmissions from the US Global Positioning System-Standard Position Service (GPS-SPS) and the Russian Global Navigation Satellite System (GLONASS) are used to illustrate and verify the theory     

多带通信号直接均匀欠采样技术

该文讨论了宽带数字接收机中对多个复或实的带通信号的直接均匀采样。对这多个通带位置及带宽均是任意的实或复的带通信号给出了采样率应满足的关系,用此采样率采样使输入数据得到有效的压缩,同时结合滤波器将频谱进行搬移,最后给出了实例。     

SC filter for RF sampling and downconversion with wideband image rejection

In this paper we present an SC filter for RF downconversion using the direct RF sampling and decimation technique. The circuit architecture is generic and it features high image rejection for wideband signals and good linearity. An SC implementation in 0.13μm CMOS suitable for an RF of 2.4 GHz and 20 MHz signal bandwidth is presented as a demonstrator. Simulation results obtained using Cadence Spectre simulation tools are included.     

Analog signal generator for BIST of wideband IF signals bandpass sigma-delta modulator

This paper presents improvements in generation of wideband and high dynamic range analog signal for area-efficient MADBIST, especially for the on-chip testing of wireless communication IF digitizing sigma-delta modulator chip. Via increasing the order of the one-bit bandpass sigma-delta modulation algorithm up to 12 and using finite repetitious bitstream approximating scheme, it can achieve great improvements in signal bandwidth instead of purity at the cost of very little hardware overhead. Another contribution in this work is to provide the theoretical analysis of the reconstructed signal degradation due to harmonic distortion and clock jitter. Such on-chip analog stimulus generation scheme is especially fit for IF digitizing bandpass sigma-delta modulator chip's production-time testing and in-the-field diagnostics. The technique can also be extended to mixed-signal communication SoC built-in-self-test.     

Operator basis for analytic signal construction

The operator basis for one-dimensional analytical signal construction is considered. Why the Hilbert transform plays a fundamental role is clarified. Extension to the case of multidimensional signals is considered. Possible ramifications for the definition of a fractional analytic signal are discussed.     

Sampling theorems for uniform and periodic nonuniform MIMO sampling of multiband signals

We examine a multiple-input multiple-output (MIMO) sampling scheme for a linear time-invariant continuous-time MIMO channel. The input signals are modeled as multiband signals with different spectral supports, and the channel outputs are sampled on either uniform or periodic nonuniform sampling sets, with possibly different but commensurate intervals on the different outputs. This scheme encompasses Papoulis' generalized sampling and several nonuniform sampling schemes as special cases. We derive necessary and sufficient conditions on the channel and the sampling rate that allow stable perfect reconstruction of the inputs or, equivalently, perfect inversion of the channel. From an implementation viewpoint, we note that it is desirable that the reconstruction filters have continuous frequency responses. We derive necessary and sufficient conditions that guarantee this continuity property. The frequency responses of the reconstruction filters are specified as solutions to a system of linear equations. Finally, we demonstrate that perfect reconstruction may be possible, even when the channel outputs are sampled at an average rate that does not allow the reconstruction of any output from its samples alone. In certain instances, this average rate can achieve the recently presented fundamental bounds on MIMO sampling density.     

Nonuniform sampling of bandlimited modulated signals

In this paper it is shown that an unequally spaced sampling can be implemented on the base of sinc-composition function usually used in the uniform sampling expansion. The nonuniform sampler is based on a level crossing detector (LCD) which produces a sample of carrier whenever the integral of modulating function crosses a threshold level. The information about the modulated signal is contained in the carrier samples taken at the instants which are defined by modulating function. The Riemann-Stieltjes uniform integral sum representation of the Fourier transform of signal is used as a mathematical base for the derivation of the principal results. In the particular case of the representation of single-valued real positive function, the suggested method leads to the signal representation by the equally weighted sampling at the nonuniformly distributed instants. The error estimation and numerical example illustrating the methods are given.     

Perfect reconstruction formulas and bounds on aliasing error insub-Nyquist nonuniform sampling of multiband signals

We examine the problem of periodic nonuniform sampling of a multiband signal and its reconstruction from the samples. This sampling scheme, which has been studied previously, has an interesting optimality property that uniform sampling lacks: one can sample and reconstruct the class ℬ(ℱ) of multiband signals with spectral support ℱ, at rates arbitrarily close to the Landau (1969) minimum rate equal to the Lebesgue measure of ℱ, even when ℱ does not tile R under translation. Using the conditions for exact reconstruction, we derive an explicit reconstruction formula. We compute bounds on the peak value and the energy of the aliasing error in the event that the input signal is band-limited to the “span of ℱ” (the smallest interval containing ℱ) which is a bigger class than the valid signals ℬ(ℱ), band-limited to ℱ. We also examine the performance of the reconstruction system when the input contains additive sample noise     

带通信号的数字正交采样定理及优化设计

在数字正交采样中,带通信号存在频谱迁移问题,虽然满足带通信号的采样定理,仍可能产生频谱混叠。该文证明了带通信号的数字正交采样定理,并讨论了这种采样系统的优化设计。     

Exact solution of a bandpass matching problem

This paper discusses the exact design of a bandpass matching circuit for transmission of power from a source of internal resistanceR ₁ to a load of resistanceR ₂. The design is obtained in terms of an unknownQ factor, the value of which is to be determined by solving a cubic equation.     

连续时间信号的采样与重构及其实现

介绍了连续时间信号的采样和重构的基本原理,并通过MATLAB实现了对指数信号的采样及重构。     

基于带通采样的椭圆球面波函数数值解法

针对椭圆球面波函数原数值解法存在计算量大、计算时间长的问题,提出了基于带通采样的新数值解法.新数值解法根据带通采样定理确定采样频率,利用原数值解法求得椭圆球面波函数带通采样值,对带通采样值进行上抽样、数字滤波和格拉姆-施密特正交化,求得椭圆球面波函数的近似数值解.理论分析和仿真结果表明,新数值解法能有效降低计算量、计算...     

采样时钟抖动在弱光信号检测中的影响分析

信号采样是弱光信号检测的关键技术环节,由于采样时钟抖动引起的采样信号的输出误差会影响后续的信号检测和处理。为此,分析了输入光信号为近高斯分布波形时由时钟抖动引起的采样误差,推导出了采样输出的信噪比损失公式,讨论了采样带宽、输入信噪比以及信号脉宽对输出信噪比损失的影响,最后以取样积分检测技术为对象,计算了在不同累积次数的条件下采样抖动对取样积分检测性能的影响,对弱光信号检测中的采样时钟选取具有一定的指导意义。     

雷达数字接收机中的中频带通采样和数字I/Q解调及其实现

带通采样技术是实现微字接收机的关键技术。数字接收机的载频和带宽影响其采样和处理的形式.本文首先较为详细地讨论了带通采样理论,然后在此基础上提出了两种采样形式的数字接收机的设计方案.