Continuous Phase Modulation--Part I: Full Response Signaling

The continuous phase modulation (CPM) signaling scheme has gained interest in recent years because of its attractive spectral properties. Data symbol pulse shaping has previously been studied with regard to spectra, for binary data and modulation index 0.5. In this paper these results have been extended to theM-ary case, where the pulse shaping is over a one symbol interval, the so-called full response systems. Results are given for modulation indexes of practical interest, concerning both performance and spectrum. Comparisons are made with minimum shift keying (MSK) and systems have been found which are significantly better inE_{b}/N_{0}for a large signal-to-noise ratio (SNR) without expanded bandwidth. Schemes with the same bit error probability as MSK but with considerably smaller bandwidth have also been found. Significant improvement in both power and bandwidth are obtained by increasing the number of levelsMfrom 2 to 4.     

部分响应连续相位调制信号的循环平稳特性分析

根据部分响应连续相位调制信号在不同调制指数下的基带循环谱,由数字调制信号的基带循环谱与带通循环谱的关系式,推导了其相应带通信号循环谱的表达式并进行了详细的分析,得出了不同调制指数下循环频率与载频、峰值频偏以及码元宽度之间的关系式。仿真实验证明其这些结论是正确的。     

A Class of Reduced-Complexity Viterbi Detectors for Partial Response Continuous Phase Modulation

Partial response continuous phase modulation (CPM) gives constant envelope digital modulation schemes with excellent power spectra. Both narrow main lobe and low spectral tails can be achieved. When these signals are detected in an optimum coherent maximum likelihood sequence detector (Viterbi detector), power efficient schemes can also be designed, sometimes at the expense of receiver complexity. This paper describes a general class of simple Viterbi detectors with reduced complexity compared to the optimum case. The key idea is that the approximate receiver is based on a less complex CPM scheme than the transmitted scheme. The asymptotically optimum reduced-complexity receiver is found for a variety of transmitted schemes and various complexity reduction factors, for a specific class of receivers and modulation indexes. A new distance measure is introduced for the performance analysis. Smooth schemes based on raised cosine pulses are analyzed and simulated for the case of simplified reception. A graceful performance degradation occurs with the reduction of complexity.     

Alamouti Code with Quadrature Partial Response Signaling

In this letter, the Alamouti code combined with partial response signaling (PRS) is proposed. The bit error rate of the proposed quadrature PRS (QPRS) Alamouti code is derived for the quasi-static Rayleigh fading and additive white Gaussian noise channel. Furthermore, its performance in a severely bandlimited channel is simulated by using chopping filter and compared with the conventional Alamouti code. The numerical results show that the proposed QPRS Alamouti code outperforms the conventional Alamouti code under the chopping environment.     

Continuous Varactor-Diode Phase Shifter with Optimized Frequency Response

A method is introduced for designing continuous varactor-diode phase shifters with optimum frequency response. The circuit used gives very small frequency variations of the phase shift if the maximum phase shift of the device is less than about 200/spl deg/. Measurement results on a 180/spl deg/ L-band phase shifter are presented. This unit gives less than 5/spl deg/ variation of any given phase shift less than 180/spl deg/, when the frequency is changed from 1.5 to 1.7 GHz.     

Effect of Phase Ripple on Class 4 Partial Response Data Signals

An expression is derived for the mean square error of a SSBAM or a baseband multilevel class 4 partial response data signal when distorted by a channel which has a sinusoidal phase ripple. Such characteristics are approximated when the channel has been equalized by so called "bump" group delay equalizers. Included are the expressions for the optimum carrier phase and sampling time. For a low frequency group delay ripple, it is shown that the error can vary by a factor of seven for differing frequency and phasing of the ripple with the same peak group delay variation.     

基于CPM的部分带干扰抑制技术

提出了一种空时编码慢跳频连续相位调制（CPM）系统用于抗部分带噪声干扰。由于CPM信号的内在记忆性,传统的检测方法复杂度较高,结合Laurent分解和差分预编码方法部分消除了CPM信号的内在记忆性,提出了一种软输入软输出的线性接收机,联合信道译码进行迭代检测,大大降低了接收机的复杂度并且提高了系统的抗干扰性能。最后,利用迭代干扰状态信息（JSI）估计,进一步改善了系统的抗干扰性能。     

A Spread Spectrum System with Frequency Hopping and Sequentially Balanced Modulation--Part II: Operation in Jamming and Multipath

The broad-band noise performance of a spread spectrum system with frequency hopping and sequentially balanced modulation was analyzed in Part I of this paper. Here, the analysis is extended to include operation In jamming environments and in specular multipath. Bit-error probability and ranging accuracy curves are presented in each case.     

Continuous Phase Chirp (CPC) Signals for Binary Data Communication--Part II: Noncoherent Detection

Previous work has shown that coherent multiple bit observation of binary continuous phase chirp (CPC) signals gives improved error rate performance compared to the conventional bit-by-bit detection scheme. This paper determines bounds on the error rate improvement made possible by multiple bit observation for optimum and suboptimum [average matched filter (AMF)] noncoherent detection of binary CPC signals in additive white Gaussian noise (AWGN). For the same observation interval, it is shown that noncoherent CPC receivers provide higher signal-to-noise (SNR) gain than coherent receivers compared to the respective optimum single bit schemes. In particular, the three-bit noncoherent AMF receiver is shown to yield 3 dB SNR gain over a wide range of signal parameters.     

Robust Time and Phase Synchronization for Continuous Phase Modulation

A novel joint timing and phase-recovery technique is proposed for continuous phase modulation (CPM) systems based on Kalman filtering and an approximate representation of CPM signals with nonorthogonal exponential expansions (nOEE). Compared with existing techniques, the proposed synchronizer requires a less complex front-end processor, and can achieve reliable acquisition performance with a shorter preamble. The asymptotic stability and convergence of the proposed synchronizer is analyzed, including the effect of statistical channel-modeling errors on the convergence characteristics. The selection of suboptimal nOEEs and the design of triple-initialized Kalman filters are also discussed. Both theoretical and simulation results show that the proposed synchronizer is robust in acquiring and tracking both the time shift and the phase offset on either time-invariant or time-variant channels.     

连续相位板优化设计

提出一种适用于连续相位板设计的改进Gerchberg-Saxton(GS)算法,该算法应用相位展开相关原理,结合滤波处理使GS算法设计的近场相位连续分布,同时提出在GS算法的远场迭代中采用经过修正的振幅函数,可使远场光斑的包络更接近目标函数。模拟实验表明,该方法解决了现有连续相位板设计中相位连续性与靶面光强控制效果难以同时优化的矛盾,可满足惯性约速聚变(ICF)对束匀滑元件相位连续性、光斑包络及能量集中度的要求。     

具有连续相位的8PSK调制

连续相位的QPSK信号具有恒定包络,解决了传统QPSK信号由于相位跳变所带来的包络起伏问题,但其频带利用率没有8PSK高,为提高频带利用率,提出了连续相位8PSK(CP8PSK)调制。本文首先利用差分编码规则来表征8PSK信号一个符号周期的相位变化,进而将其表示为连续相位调制(CPM)的形式,再使用频率脉冲对其相位进行脉冲整形,最终得到具有连续相位的CP8PSK表达式。为了降低系统的整体复杂度,本文还对CP8PSK进行了Laurent分解。根据理论分析CP8PSK信号应当具有恒定包络,而且比连续相位的QPSK调制要有更高的带宽效率和更平滑的频谱,通过MATLAB进行仿真之后,得到的CP8PSK具有恒定包络,且带宽效率在同等情况下要高于整形的交错QPSK(SOQPSK)和8PSK,频谱也更加平滑,抗误码性能与理想8PSK相比损失也不大。      

Continuous Phase Modulation of F-QPSK-B Signals

A continuous phase modulation (CPM) implementation alternative of a recently standardized class of Feher-patented quadrature phase-shift keying (F-QPSK-B) modulation is proposed. Based on the fact that the F-QPSK-B signal has a quasi-constant envelope and continuous phase characteristics, it is shown that it can indeed be generated by the CPM scheme. For example, an F-QPSK-B signal can be fully generated using an existing FM-based transmitter with a modulation index of 0.5. Furthermore, a premodulation filter and an alternating change monitor differential encoder for the continuous-phase-modulated F-QPSK-B signal to be fully compatible with the I/Q modulated F-QPSK-B signal are proposed, allowing direct symbol-by-symbol coherent detection without the use of any special decoding schemes inherent in all CPM schemes. It is shown that the power spectral density and eye diagram of the continuous-phase-modulated F-QPSK-B signal are practically the same as those of the I/Q modulated F-QPSK-B signal. By utilizing CPM characteristics, an optimum maximum-likelihood (ML) coherent receiver for the F-QPSK-B signal is proposed. It is shown that the bit-error-rate performances of the optimum ML coherent detection, symbol-by-symbol coherent detection, and noncoherent detection of the continuous-phase-modulated F-QPSK-B signal are almost the same as those of the I/Q modulated F-QPSK-B signal     

Low Complexity Carrier Phase Tracking Decoders for Continuous Phase Modulations

Phase tracking capability is incorporated into two sequence estimation decoders for continuous phase modulations. One decoder employs the Viterbi algorithm; the other uses a reduced-survivor approach proposed earlier by one of the authors [11] for the more bandwidth efficient of these modulations. Computational complexity with the simplest of the joint data/phase algorithms is only marginally greater than that required for the equivalent decoding algorithm employing an externally derived carrier phase reference as supplied by a conventional carrier recovery circuit. Simulations with representative partial response modulations demonstrate the phase synchronization and tracking capabilities of the decoders. High SNR losses relative to an optimal receiver having perfect phase knowledge are found to be small (∼ 1 dB).     

Carrier Phase and Clock Recovery for Continuous Phase Modulated Signals

This paper presents an analysis of a synchronization circuit to be used for carrier-phase and symbol-timing recovery in continuous phase modulation systems.M-ary modulation formats with arbitrary pulse shaping and rational modulation indexes are assumed. Circuit performance is expressed in terms of variances of phase and timing errors. Numerical results are provided for some important cases, including minimum shift keying and tamed frequency modulation. Theoretical results are found in good agreement with computer simulations.     

Convolutional Coding Combined with Continuous Phase Modulation

Background theory and specific coding designs for combined coding/modulation schemes utilizing convolutional codes and continuous-phase modulation (CPM) are presented. In this paper the case ofr = 1/2coding onto a 4-ary CPM is emphasized, with short-constraint length codes presented for continuous-phase FSK, double-raised-cosine, and triple-raised-cosine modulation. Coding buys several decibels of coding gain over the Gaussian channel, with an attendant increase of bandwidth. Performance comparisons in the power-bandwidth tradeoff with other approaches are made.     

Space-Time Coded Systems using Continuous Phase Modulation

We develop space-time trellis coded (STC) schemes using continuous-phase modulation (CPM). We employ the Rimoldi model of CPM to create a decomposed model of STC-CPM. The decomposition separates the coding from the modulation. The space-time encoding and the inherent CPM encoding is combined into a single trellis encoder on the ring of integers modulo-. This is followed by a bank of memoryless modulators. The model allows the search for good space-time codes to take into account the inherent encoding of the modulation.     

符号内连续相位差分相移键控调制方法

提出了一种幅度准恒包络、相位连续的差分相移键控调制与解调方法.该方法设计了一组基带信号集合,根据输入的信息值和状态值选择基带信号来实现信号调制.在信号解调中,通过计算接收信号在一个符号持续时间内的相位变化累积量来判决发送信息.仿真结果表明,该调制方法具有良好的频谱特性和准恒包络特性,并且避免了本振偏离、多普勒频移等引起的符号间相位变化对信号解调的影响.     

An Audio Response Unit Based on Partial Autocorrelation

This paper describes an audio response unit used in data communication services. The speech segments necessary to respond are stored in a large capacity magnetic drum in terms of partial autocorrelation (PARCOR) coefficients and excitation source information. PARCOR coefficient is a new parameter to express accurately the spectrum envelope of speech signals. Multiple speech signals can be synthesized simultaneously by means of a timemultiplexed digital filter composed of a high-speed arithmetic unit. The unit is able to respond to more than 7000 speech segments of 1-s duration.     

Error Rate Monitoring in a Partial Response System

Pseudoerror monitoring techniques, besides providing a precursive, measure of system degradation, can also be used in extrapolation schemes to estimate the actual bit error rate of a digital link. This study examines pseudoerror techniques as applied to a precoded, modified duobinary system. Two known methods of pseudoerror generation, namely, threshold modification and sampling offset, are compared with two new monitors using controlled amounts of amplitude and phase distortion. The threshold modification monitor is most robust to channel degradations, while amplitude or phase distortion monitors seem to be more accurate in estimating the actual error rate but less robust. The sampling offset monitor seems to be less robust than the other monitors due to its unavoidable sensitivity to degradations affecting the system phase. Methods of improving the estimation accuracy by the choice of degradation parameters are also examined.