优化参数对CPM-PSWF信号性能的影响

基于椭圆球面波信号的连续相位调制(Continuous Phase Modulation Based on Prolate Spheroi-dal Wave Function,CPM-PSWF)方法是一种新颖的数字调制方式,调制参数的优化与其调制信号性能有着直接联系.分析不同调制参数对CPM-PSWF信号性能的影响,优化选择调制参数,对获得能量聚集性和功率效率都较高的CPM信号具有重要意义.首先,对基于椭圆球面波信号的CPM信号进行描述;其次,采用韦尔奇(Welch)谱密度估计法,对时间带宽积、调制指数、关联长度等不同参数对CPM-PSWF调制信号的功率谱密度和带宽特性的影响进行了仿真分析.实验结果表明,选用0阶椭圆球面波信号,小时间带宽积、调制指数和符号进制数越小,关联长度越大时,CPM-PSWF信号具有频谱带外高频滚降快、占用带宽小的特点.     

基于 Givens旋转变换的PSWF脉冲调制信号PAPR抑制方法

针对基于椭圆球面波函数(Prolate Spheroidal Wave Function, PSWF)脉冲的调制信号峰均功率比过高的问题,该文提出一种基于Givens旋转的PSWF脉冲峰均功率比抑制方法.该方法从正交PSWF脉冲组的特征向量加权表示入手,利用 Givens旋转矩阵(,,)i j qG 对所有子坐标平面(,)i j 进行q角度的旋转,搜寻使脉冲组PAPR (Peak-to-Average Power Ratio, PAPR)值最小的旋转矩阵,最后利用该矩阵对原PSWF脉冲组进行Givens变换,从而实现降低PAPR的目标.针对Givens旋转次数较多导致计算复杂度大的问题,该文提出分组flipping迭代的算法实现方案.理论证明了该变换方法能够保持脉冲组的带内能量聚集和正交性.仿真结果表明,该方法有效降低了脉冲组的PAPR,同时系统传输效率、调制信号功率谱密度与系统误码率性能均保持不变.     

时间反转水声通信系统的优化设计与仿真

针对现有时间反转(Time Reversal,TR)水声通信存在的传输波形能量聚集性低和难以准确跟踪信道特性变化的问题,从脉冲波形设计和接收解调方案2个方面入手,对TR水声通信系统进行了优化设计。利用具有最佳时频能量聚集性的椭圆球面波函数(Prolate Spheroidal Wave Functions,PSWF),设计了TR水声通信的传输波形,提出了基于接收参考的时间反转传输方案。仿真结果表明,该方法在改善调制信号功率谱密度的同时,有效地提高了系统在水声信道下的误码率性能。     

基于椭圆球面波函数的最佳窗函数分析

针对椭圆球面波函数在窗函数中的应用问题,从能量聚集性角度理论证明了椭圆球面波函数（PSWF）是最佳窗函数,采用基于特征值分解的数值算法求解椭圆球面波函数,筒化了求解过程,算法简便,易于实现。通过仿真分析,与现有的窗函数相比,在相同持续时间和边瓣峰值条件下,椭圆球面波窗函数主瓣最窄、能量聚集性最好,频谱分辨率最高。     

基于PSWF框架的非正交脉冲波形调制方法

现有调制方法主要基于正弦函数,并利用其正交性传输信息.本文突破对调制信号的正弦函数约束和正交性限定,从椭圆球面波函数(Prolate Spheroidal Wave Function,PSWF)的高能量聚集性和框架函数系的过完备特性入手,提出基于PSWF框架的非正交脉冲波形调制方法(Nonorthogonal Pulse Shape Modulation,NPSM).该方法利用频谱交叠的非正交PSWF获得了优良的功率谱特性,同时利用框架函数的过完备特性,在提高系统频带利用率的同时,有效消除码间串扰.与目前广泛应用的QAM-OFDM方法进行性能相比,在相同调制幅度数和误码率的情况下有2dB的优势,且该优势随调制进制数增加而扩大,同时其调制信号具有良好的功率谱特性,PAPR性能比相同频带利用率的QAM-OFDM有3dB的优势.     

一种新的PSWF调制信号PAPR抑制方法

针对椭圆球面波(Prolate Spheroidal Wave Function,PSWF)时域正交调制信号峰均功率比(Peak-to-Average Power Ratio,PAPR)过高,易受功率放大器非线性特性影响,造成PSWF脉冲间良好正交性下降,导致系统解调性能下降的问题,引入A律压缩,提出了一种基于A律压缩的PSWF调制信号PAPR抑制方法。该方法能够有效抑制PSWF调制信号PAPR,改善经过功放后调制信号的功率谱和系统误码性能。     

椭圆球面波函数时频能量聚集性研究

椭圆球面波函数(PSWF)集是时频域上能量聚集性最佳的信号形式,在提高系统频谱利用率、降低频带间干扰方面具有天然优势.本文针对椭圆球面波函数最佳时频能量聚集性及其在工程中应用的问题,重点研究了时限PSWF在频域的最佳能量聚集性,及其乘、加、卷积运算对PSWF能量聚集性的影响,讨论了乘加卷积运算对PSWF工程应用的影响.理论分析和仿真结果表明,两个同频段同时间带宽积PSWF信号相加后带内能量聚集度介于两者之间;奇数阶PSWF与偶数阶PSWF相乘后带内能量聚集度提高,奇数阶与奇数阶或偶数阶与偶数阶PSWF相乘后带内能量聚集度大幅下降;两个同频段同时间带宽积PSWF信号卷积后能量聚集度提高,且相卷积的两个PSWF阶数越低,运算后能量聚集度越高.     

椭圆球面波信号乘加卷积运算后频谱特性研究

椭圆球面波函数(Prolate Spheroidal Wave Function, PSWF)集是时频域能量聚集性最佳的信号形式, 在提高系统频谱利用率、降低频带间干扰方面具有天然的优势.针对椭圆球面波信号在放大、检测及滤波等工程应用中频谱发生变化的问题, 重点研究了椭圆球面波信号相加、相乘和时域卷积运算后频谱特性的变化, 通过理论分析和仿真验证给出了椭圆球面波信号乘加卷积运算后频谱特性的变化规律, 讨论了乘加卷积运算对椭圆球面波函数工程应用的影响, 为椭圆球面波脉冲信号相关研究提供一定的理论参考.     

正交椭圆球面波函数脉冲调制方法

为了提高通信系统的功率效率和频谱效率,该文提出正交椭圆球面波函数(PSWF)脉冲调制方法。该方法利用具有高能量聚集性的椭圆球面波函数作为传输波形来提高通信系统的功率效率,采用时域正交、频谱混叠或交叠的正交脉冲组传输信息,以减小信息传输带宽,提高通信系统的频谱效率。理论分析及仿真结果表明,该方法可使通信系统的单位频带利用率快速接近2 Baud/Hz,且已调信号具有较好的频域能量聚集性,不仅有利于提高系统的功率效率,还可有效减小对相邻通信用户的电磁干扰。     

基于PSWF的多进制PPM-UWB系统分析

椭圆球面波函数(Prolate Spheroidal Wave Function,PSWF)脉冲具有最佳时域能量聚集性和频谱灵活可控性的特点,被认为是符合超宽带(ultra-wideband,UWB)系统要求的一种性能优良的脉冲。首先给出了满足FCC频谱掩膜要求的UWB脉冲波形设计方法,并将该方法应用于多进制TH-PPM超宽带系统中。分析了多进制TH-PPM超宽带系统原理,理论上推导了基于PSWF脉冲的多进制PPM-UWB系统的符号差错率公式,并与高斯脉冲进行比较。仿真结果表明,基于PSWF脉冲的UWB系统符号差错率性能要明显优于Gauss脉冲。     

On the representation of CPM signals by linear superposition ofimpulses in the bandpass domain

A novel signal generation concept for continuous phase modulations (CPMs) with modulation index 1/2 based on real impulses is presented. With this concept, bandpass CPM signals can be generated directly in one step instead of the two consecutive steps, namely, the generation of the complex envelope and the modulation of the carrier by the complex envelope, which are necessary in conventional signal generators. Mathematical expressions for both the real impulses and the bandpass CPM signals are derived and a simple modulator structure is discussed. Examples for the real impulses are given. Among these are the well-known CPM schemes of minimum shift keying (MSK), sinusoidal frequency shift keying (SFSK), and Gaussian minimum shift keying (GMSK). As an example, the validity of the novel signal generation concept is shown for the latter CPM scheme     

Results of optimal discrete pulse shaping for MSK-type signals

This paper presents the results of discrete bandwidth optimizations used on minimum shift keying (MSK)-type signals. Bandwidth-optimal pulse shaping achieves maximum spectral confinement with respect to given confinement frequencies and given levels of allowable modulated signal envelope nonuniformity. This paper presents a family of design curves defining optimal confinement with respect to confinement frequency and the level of modulated signal amplitude modulation (AM)     

Continuous Phase Modulation--Part II: Partial Response Signaling

An analysis of constant envelope digital partial response continuous Phase modulation (CPM) systems is reported. Coherent detection is assumed and the channel is Gaussian. The receiver observes the received signal over more than one symbol interval to make use of the correlative properties of the transmitted signal. The Systems areM-ary, and baseband pulse shaping over several symbol intervals is considered. An optimum receiver based on the Viterbi algorithm is presented. Constant envelope digital modulation schemes with excellent spectral tail properties are given. The spectra have extremely low sidelobes. It is concluded that partial response CPM systems have spectrum compaction properties. Furthermore, at equal or even smaller bandwidth than minimum shift keying (MSK), a considerable gain in transmitter power can be obtained. This gain increases withM. Receiver and transmitter configurations are presented.     

A New Two-Branch Amplification Architecture and its Application with Various Modulated Signals

This paper proposes a new two-branch amplification architecture that combines baseband signal decomposition with RF front-end optimization. In the proposed architecture, the filtered modulated signals are separated into two components that are then amplified independently and combined to regenerate an amplified version of the original signal. A branch with an efficient amplifier transmits a low-varying envelope signal that contains the main part of the information. Another branch amplifies the residual portion of the signal. The baseband decomposition and parameters of the RF part are optimized to find the configuration that gives the best power efficiency and linearity. For M-ary quadrature amplitude modulation （M-QAM） signals, this technique is limited in terms of power efficiency. However, for filtered continuous phase modulation （CPM） signals, especially for minimum shift keying （MSK） and Gaussian MSK （GMSK） signals, high power efficiency can be achieved with no significant impact on the overall linearity. The results show that this technique gives better performance than the single-ended ctass-B amplifier.     

Frequency offset estimation in the intermediate frequency for satellite-based AIS signals

In this paper, an accurate frequency offset estimator is investigated in the intermediate frequency for the satellite-based automatic identification system (AIS) signals. Using Gaussian minimum shift keying (GMSK) modulation for transmission, the AIS signal is shown to be a plane wave with the modulated phase information and carrier frequency resulting from the Doppler effects. Hence, the phase information can be eliminated with a re-modulated signal, and the frequency offset can be estimated by the ratio of the maximum spectral amplitude and its neighbor spectral amplitude based on the fast Fourier transformation (FFT) interpolation. The estimator has low complexity, and it is easy to implement. Computer simulations are used to assess the performance of the estimator.     

Fractional Multi‐bit Differential Detection Technique for Continuous Phase Modulation

A new low‐complexity differential detection technique, fractional multi‐bit differential detection (FMDD), is proposed in order to improve the performance of continuous phase modulation (CPM) signals such as Gaussian minimum shift keying (GMSK) and Gaussian frequency shift keying (GFSK). In comparison to conventional one‐bit differential detected (1DD) GFSK, the FMDD‐employed GFSK provides a signal‐to‐noise ratio advantage of up to 1.8 dB in an AWGN channel. Thus, the bit‐error rate performance of the proposed FMDD is brought close to that of an ideal coherent detection while avoiding the implementation complexity associated with the carrier recovery. In the adjacent channel interference environment, FMDD achieves an even larger SNR advantage compared to 1DD.     

Nonlinear continuous phase frequency shift keying

A novel signal-space coded CPM (continuous phase modulated) signaling technique, called nonlinear CPFSK (continuous phase frequency shift keying) signaling, which guarantees the maximum constraint length allowed by the number of states is introduced. Nonlinear CPFSK signals use a suitably selected state transition matrix during all signaling intervals. The selected state transition matrix is realized by changing the modulation index of the signals, hence the modulation index used during any interval depends on the transmitted symbol as well as on the state of the system. Binary nonlinear CPFSK signaling schemes are constructed and analyzed. Numerical results indicate that nonlinear CPFSK signals can achieve attractive minimum distances compared with other existing CPM signaling formats     

New bandwidth efficient overlapped pulse shape

A new pulse shape of duration twice the symbol interval is proposed for bandwidth efficient modulation. The proposed pulse shape is obtained by convolving a square pulse shape with a sinusoidal frequency shift keying (SFSK) pulse shape. The power spectral density (PSD) of a signal with the proposed pulse shape shows less power in spectral sidelobes than that of a signal with overlapped raised-cosine pulse shape