Theory of False Lock in Costas Loops

This paper is concerned with new results on data related false lock of Costas loops caused by arm filter distortion of the data. The false lock phenomena is demonstrated to occur for random as well as periodic data and the relative levels of lock are predicted. It is shown that, for the case of random data with Manchester symbols, strong lock points exist when the incoming carrier frequency and the loop VCO frequency differ bynR_{s}/2 (n = 1, 2, 3, ...)Hz where Rsis the data symbol rate. In addition to the loop error signal the lock detection signal(I^{2}Q^{2})is also analyzed for false lock effects. The theory also applies to the case of NRZ data symbols with the main result being strong false lock points also occur at VCO frequency offsets ofnR_{s}/2 (n = l, 2, 3, ldot)but at different levels than the Manchester data. The results of these analyses lead to schemes capable of detecting false lock.     

PSK optical homodyne detection using external cavity laser diodesin Costas loop

5-Gb/s optical PSK (phase-shift keying) homodyne detection experiments are discussed. In these experiments, the optical carrier is recovered by a Costas optical phase-locked loop using a multielectrode local oscillator (DFB) laser diode at 1.55 μm with a flat FM response. Although the beat linewidth of 80 kHz is broad compared to the loops in other phase-locked loop (PLL) experiments, phase locking with Costas loop is confirmed at 5 Gb/s by increasing the loop natural frequency. The receiver sensitivity is -42.2 dBm or 93 photon/bit for a 2⁷-1 pseudorandom bit sequence (PRBS) in front of a 90° hydride     

Costas环单片集成电路

介绍了多功能单片集成Ｃｏｓｔａｓ环ＫＤ８２的电路、版图和工艺设计方法。     

A CMOS rectifier-integrator for amplitude detection in hard diskservo loops

In this paper a CMOS alternative amplitude detection system is presented. It is designed as an alternative for the, bipolar, amplitude detection in hard disk servo systems. The amplitude is detected by converting the input voltage to a current, rectifying the current, and integrating it on a capacitor. For this a new OTA topology and a rectifier cell are designed. This circuitry is expanded with a very linear current mirror and an automatic offset compensation system to cope with technology spread. The measured accuracy of the amplitude detector is 0.2% (9 b). This makes the circuit suitable for implementation in state-of-the art hard disk systems with very high track densities and very short access times. Because the circuit is realized in standard CMOS it is a further step toward CMOS only hard disk electronics. Because the circuit operates from a single 3 V power supply and has limited power consumption it can be used in battery powered systems     

False-Lock Performance Improvement in Costas Loops

A technique is described to reduce the probability of false-lock in Costas loops. This is where a frequency offset arises at a multiple of half the incoming data rate due to finite bandwidth of the arm filters. A modification is described to process components of this offset so as to augment the feedback control voltage. The performance is analyzed and it is shown how certain false-lock positions may be avoided.     

Constructions and properties of Costas arrays

A Costas array is an n × n array of dots and blanks with exactly one dot in each row and column, and with distinct vector differences between all pairs of dots. As a frequency-hop pattern for radar or sonar, a Costas array has an optimum ambiguity function, since any translation of the array parallel to the coordinate axes produces at most one out-of-phase coincidence. We conjecture that n × n Costas arrays exist for every positive integer n. Using various constructions due to L. Welch, A. Lempel, and the authors, Costas arrays are shown to exist when n = p - 1, n = q - 2, n = q - 3, and sometimes when n = q - 4 and n = q - 5, where p is a prime number, and q is any power of a prime number. All known Costas array constructions are listed for 271 values of n up to 360. The first eight gaps in this table occur at n = 32, 33, 43, 48, 49, 53, 54, 63. (The examples for n = 19 and n = 31 were obtained by augmenting Welch's construction.) Let C(n) denote the total number of n × n Costas arrays. Costas calculated C(n) for n ≤ 12. Recently, John Robbins found C(13) = 12828. We exhibit all the arrays for n ≤ 8. From Welch's construction, C(n) ≥ 2n for infinitely many n. Some Costas arrays can be sheared into "honeycomb arrays." All known honeycomb arrays are exhibited, corresponding to n = 1, 3, 7, 9, 15, 21, 27, 45. Ten unsolved problems are listed.     

结合Costas阵列的电子现金模块

文章基于Costas阵列寻找困难而判定容易的事实,结合Costas阵列构造一个电子现金支付模块,从而提高了整个系统的安全性能。     

Counterexample of truncated Costas optical orthogonal codes

The following results are proven in this paper: 1) neither periodic autonor cross-correlation of the truncated Costas optical orthogonal code (TC OOC) is upper bounded by 1; 2) TC OOC is a class of (ω(2p-3), ω,2,2) optical orthogonal codes     

Improving Frequency Acquisition of a Costas Loop

A Costas loop for tracking a BPSK signal does not acquire when the initial frequency error is comparable to the loop bandwidth. This paper describes methods for deriving control proportional to frequency error so as to improve the frequency acquisition capability by an AFC augmentation. A composite AFC/Costas loop is realized by combining the individual loops. Pull-in from a frequency error much greater than the Costas loop bandwidth is now feasible. The increase in phase error due to the AFC capability is evaluated by a linearized analysis. If the bandwidth of the AFC portion is sufficiently narrow, the degradation is negligible. Improved frequency acquisition can also be realized by a simple modification of the Costas loop to remove the low-pass filter on the quadrature phase detector channel, with negligible degradation to phase tracking.     

数字锁相技术在光纤衰减检测中的应用

光纤衰减是光纤传输性能测试的基本参量。本文通过对光纤衰减测试原理的分析,利用数字锁相技术,通过以计算机为核心,高精度的AD转换、配以DSP技术的数字信号处理,实现了长距离光纤衰减的检测,并通过测试结果比对表明测试系统切实可行。     

数字Costas锁相环的设计与仿真

接收机本地载波跟踪与恢复是基于软件无线电原理进行数字信号相干解调的前提,本文从Costas锁相环原理出发,提出了数字域实现载波跟踪与恢复的设计方法,给出了详细的设计,并根据理论分析进行了系统仿真。     

Costas序列在多用户雷达系统中的应用研究

讨论了跳频码的构造与性能,着重介绍了Costas序列的结构,用Costas序列设计跳频码能获得理想的自模糊和较好的互模糊性能.建立了跳频扩频信号的数学模型,给出了子脉冲正交的条件.论述了Costas序列的自(互)相关特性,给出了置换序列互相关函数的实用性质及模糊函数的求取算法,并进行了性能仿真,研究了Costas序列互模糊函数的特性,阐述了多用户系统中减小用户间相互干扰的方法.     

基于FPGA的Costas环设计

本文首先研究了 Costas 环的结构和原理,然后,利用 FPGA 设计了环路中的各个模块,并对设计所需的参数进行了细致的推导,最后,结合一个实际工程给出了仿真结果,仿真结果证明本文设计的 Costas 环跟踪速度快、频率误差小,能够满足实际需求。     

数字Costas锁相环的设计与仿真

接收机本地载波跟踪与恢复是基于软件无线电原理进行数字信号相干解调的前提,本文从Costas锁相环原理出发,提出了数字域实现载波跟踪与恢复的设计方法,给出了详细的设计,并根据理论分析进行了系统仿真。     

数字Costas锁相环的改进及应用

介绍了Costas锁相环的基本原理,然后提出了一种适合电视信号色度副载波恢复的改进数字Costas锁相环的基本原理.并且详细介绍了其积分清零器、相位检测器、数字环路滤波器、NCO等各个基本部件的设计,最后在Matlab上给出了该算法的仿真结果并且做了分析.     

A remark on the definition of Costas arrays

A weaker definition of Costas arrays is shown to be equivalent to the standard one. A Costas array is a diagram whose corresponding frequency-hopping pattern has good range-doppler ambiguity properties. Our result implies that even when we demand ostensibly less restrictive ambiguities in the doppler direction, the resulting waveform becomes a Costas waveform.     

时序电路的自锁与自解锁

本文讨论了在不考虑冗余状态设计时序电路时，可能会导致“自锁”现象，并提出了设计自解锁功能异步时序电路应当遵循的一种规范化方法。     

Ambiguity function of interpulse Costas FH radar signal

A new radar waveform utilizing Costas sequences and interpulse Frequency Hopping (FH) technique is developed, which is a good high range resolution radar signal. The interpulse Costas FH coherent pulse train is introduced and the system block diagram using the interpulse Costas FH waveform is given. In the paper, ambiguity function is employed to study interpulse Costas FH radar. The mathematical expression of the ambiguity function for this waveform is derived. The advantages of the waveform are interpreted by computer simulation.     

基于科斯塔斯环法的载波提取的设计

介绍了平方变换法相干解调原理,从工程角度完善了载波提取的电路结构,消除了频移载波的误锁问题.提出用科斯塔斯环法来实现从2DPSK信号中提取相干载波,解决了提取的载波信号存在180度的相位含糊问题,为通信系统提高抗噪性能提供了条件.当载波频率很高时,工作频率较低的科斯塔斯环易于实现.并用Simulink设计出科斯塔斯环法提取载波的仿真电路图和进行相应的仿真实验.     

Golomb Costas序列的结构及其在OFDM系统中的应用

研究了用循环移位法获得的Golomb Costas序列族的特性,建立了含有一个间隙行和一个间隙列的Golomb Costas序列的结构理论,深入研究了含有一个间隙行和一个间隙列的Golomb Costas序列的代数结构、构造方法和自（互）相关特性,并证明了相关的定理。探索了用含有一个间隙行和一个间隙列的Golomb Costas序列设计OFDM 系统中跳频图样的方法,举例说明了如何设计跳频码和怎样将跳频码分配给 OFDM 系统中的用户。用含有一个间隙行和一个间隙列的Golomb Costas序列设计跳频码能获得理想的自相关特性,并且当无线通信系统中多普勒频移受限时能获得极佳的互相关性能。