美国CTS振荡器选型列表

美国CTS振荡器选型列表，美国CTS公司是一家超级专业化的元器件供应商，主要向广泛应用市场提供极其具有价值的产品线为主，经过长期的沉淀，如今的CTS已有极大的突破，尤其在制作高质量的OSC晶振产品更是将其的实力展示一览无遗，凭借着自身对于元器件行业的热爱，源源不断创造价值的同时，也行业开创大量创新型的产品，这是产品使得CTS公司的发展进行新的阶段，也使得其名气暴涨，也为其的发展打下极好的基础。

Clocks for North American synchronized networks are categorized into four basic “stratum” levels (i.e., stratum 1, 2, 3 and 4), where stratum 1 clocks are the most accurate and stratum 4 clocks are the least accurate. In addition to these four basic levels, there are two enhanced stratum classifications (i.e., stratum 3E and 4E), a level for Transit Node Clocks (TNCs) that falls between the stratum 2 and 3 levels, and another level for SONET Minimum Clocks (SMCs) that falls between the stratum 3 and 4 levels. All of these levels (which are described further below) have been standardized and their basic performance parameters are defined in ANSI T1.101. In general, the performance parameters for the various levels have been established to assure that synchronization can be transmitted through the network from the most accurate clocks, through intermediate clocks, to the least accurate clocks.

北美同步网络的时钟被分类为四个基本的“阶层”级别（即。层1、2、3和4），其中层1时钟最准确，层4时钟最少精确的除了这四个基本层次之外，还有两个增强的地层分类（即3E和4E），位于层2和层3级别之间的传输节点时钟（跨国公司）的级别，以及另一个位于层3和4级别之间的SONET最小时钟（SMC）的级别。所有这些级别（将在下文中进一步描述）已经被标准化，并且它们的基本性能参数是定义见ANSI T1.101。一般来说，已经确定了各个级别的性能参数为了确保同步可以从最准确的时钟通过网络传输中间时钟到最不精确的时钟。
Stratum 2, 3E and 3 clocks form the major distributive part of service provider synchronization networks. These clocks are generally deployed in NEs (Network Elements) in pairs (i.e., as independent, redundant units, each of which consists of an oscillator and the functions for controlling that oscillator).

层2、3E和3时钟形成了服务提供商同步网络的主要分布部分。这些时钟通常成对地部署在网元（网元）中（即，作为独立的、冗余的每个单元由一个晶体振荡器和用于控制该振荡器的功能组成）。
In general, the stratum 3E level was defined to be compatible with previously existing stratum 3 clocks (i.e., it has the same pull-in/hold-in requirements as stratum 3). However, the stratum 3E requirements on filtering of wander and holdover are significantly tighter than those for stratum 3. GR-436-CORE recommends that stratum 3E clocks be the minimum clocks used for Building Integrated Timing Supply (BITS) applications. In addition, it is recommended that stratum 3E or higher quality clocks not be used in NEs other than a BITS (e.g., it is recommended that transport NEs use stratum 3 or lower quality clocks).

一般来说，层3E级别被定义为与先前存在的层3时钟兼容（即具有与地层3相同的拉入/保持要求）。然而，地层3E对过滤的要求漂移和滞留明显比地层3的那些更紧密。GR-436-CORE建议第3E层时钟是用于楼宇集成定时供应（BITS）应用的最小时钟。在里面此外，建议在BITS以外的网元中不要使用第3E层或更高质量的时钟或石英晶体振荡器（例如，建议传输网元使用第3层或更低质量的时钟）。
The accuracy of a clock is a measure of its ability to generate, in the absence of any reference, a frequency as close as possible to the nominal frequency. Frequency accuracy is expressed and defined quantitatively in terms of maximum fractional frequency offset, as discussed in Section 3.2. Table 4-1, 4-4, 4-7 lists the freerun accuracy values for the various clock stratum levels (Stratum 2, 3E, 3).

时钟的准确性是衡量其在没有任何参考的情况下产生频率的能力尽可能接近标称频率。频率精度在最大分数频率偏移项，如第3.2节所述。表4-1、4-4、4-7列出了各种时钟阶层级别（阶层2、3E、3）的自由运行精度值。
Free-run accuracy represents the maximum long-term (20 years) deviation limit from the nominal frequency with no outside frequency reference (Free Run Mode).

自由运行精度表示与标称频率的最大长期（20年）偏差限制没有外部频率参考（自由运行模式）。

Accuracy is used in this document to indicate the degree to which the frequency of a clock may deviate from its ideal or desired value. Accuracy is usually used to specify the frequency deviation of a clock in the free-run mode. (See Section 3.6 for a discussion of modes.) Accuracy is defined such that the magnitude of the fractional frequency offset of a clock does not exceed the specified number, where: fractional frequency offset = (f-fd)/fd f = actual frequency output of a clock fd = ideal or desired frequency.
本文件中使用精度来指示时钟频率可能偏离的程度其理想值或期望值。精度通常用于指定自由运行中时钟的频率偏差模式（有关模式的讨论，请参见第3.6节。）定义精度时时钟的分数频率偏移不超过指定的数字，其中：

分数频率偏移=（f-fd）/fd
f=时钟的实际频率输出
fd=理想或期望的频率。

Drift is a measure of how a clock’s frequency accuracy (or offset) changes with time. Drift is typically used (along with an initial holdover accuracy or offset limitation and possibly a temperature-related factor) to limit the frequency offset of a clock in the holdover mode.

漂移是衡量时钟频率精度（或偏移）如何随时间变化的指标。通常使用漂移（连同初始保持精度或偏移限制以及可能的温度相关因素）保持模式中时钟的频率偏移.

保持稳定表示在所有频率参考（保持模式）。在大多数情况下，此处列出的值都是复合值，还有更多详细的标准显示在引用的部分或文档中。
Holdover frequency stability is a measure of a clock’s performance while in the holdover mode of operation (which is defined as below in Section 3.5), and is expressed and defined quantitatively in terms of maximum fractional frequency offset and (in some cases) drift. Table 4-1, 4-4, 4-7 lists the composite holdover stability values that are applicable for the various clock stratum levels. These values and the holdover stability requirements contained in this section apply while a stratum 2, 3E or 3 clock1 is operating in the holdover mode, but had been locked to a stratum 1 quality signal for a time period sufficient to establish the clock’s holdover value.

保持贴片有源晶振频率稳定性是衡量时钟在保持工作模式下性能的指标（其定义见下文第3.5节），并根据最大值进行定量表达和定义分数频率偏移和（在某些情况下）漂移。表4-1、4-4、4-7列出了复合材料保持稳定性适用于各种时钟阶层级别的值。这些值和保持稳定性当地层2、3E或3时钟1在保留区运行时，本节中包含的要求适用模式，但在足以建立时钟保留价值。美国CTS振荡器选型列表.
The holdover mode is the operating condition of a clock that has lost its references and is using data previously acquired (when it was operating in the normal mode) to control its output signal. In general, the stored data or “holdover value” used by a clock in the holdover mode is an average value obtained over some period of time (in order to reduce the effects of any short-term variations that might occur in the reference frequency during normal operations).

保留模式是指时钟失去参考并正在使用数据的工作条件先前获取的（当其在正常模式下操作时）以控制其输出信号。一般来说时钟在保持模式下使用的存储数据或“保持值”是在某些时间上获得的平均值一段时间（以减少参考中可能出现的任何短期变化的影响正常操作期间的频率）。

Free-run mode - The free-run mode of a clock is its operating condition when the output signal is totally internally controlled, with no influence of a present or previous reference. The free-run mode is the normal mode for a stratum 1 clock. Under certain unusual conditions, a network synchronization coordinator may choose to operate a clock of any other stratum level in the free-run mode without the alarms usually associated with that mode.

自由运行模式-时钟的自由运行模式是当输出信号完全内部控制，不受当前或以前引用的影响。自由运行模式是正常的第1层时钟的模式。在某些异常情况下，网络同步协调器可能选择在没有警报的自由运行模式下操作任何其他层次级别的时钟与该模式相关联。
Pull-in range is a measure of the maximum input frequency deviation from the nominal clock rate that can be overcome by a clock to pull itself into synchronization with a reference signal. This requirement applies with the clock free-run frequency at the extremes of its accuracy limits.

引入范围是对标称时钟速率的最大输入频率偏差的测量被时钟克服以使其自身与参考信号同步。此要求适用于时钟自由运行频率处于其精度极限的极限。

Wander is defined in ANSI T1.101 as the long-term variations of a digital signal’s significant instants from their ideal positions in time. Long-term variations are those that are of low frequency (e.g., less than 10 Hz). Wander is usually specified and measured in terms of Maximum Time Interval Error (MTIE) and Time Deviation (TDEV).

在ANSI T1.101中，Wander被定义为数字信号的重要瞬间与其理想的位置。长期变化是指低频（例如，小于10Hz）的变化。Wander通常根据最大时间间隔误差（MTIE）和时间来指定和测量偏差（TDEV）。
TIE is defined as the variation in the time delay of a given signal relative to an ideal timing signal over a particular time period. This time period is referred to as the observation time, S. Phase-time errors that are small, relative to those that cause a slip, are frequently expressed as TIE and may be measured in units of nanoseconds (ns), microseconds (µs) or UI. Figure 3-1 shows an example of TIE and also of MTIE, both of which are functions of the observation time S.

TIE定义为给定信号相对于理想定时信号的时间延迟在特定时间段。该时间段被称为观测时间S小的，相对于那些导致打滑的，通常用TIE表示，可以用单位纳秒（ns）、微秒（µs）或UI。图3-1显示了TIE和MTIE的一个示例，两者都是它们是观测时间S的函数。

MTIE找到给定时间窗口内信号的时间延迟的峰间变化（观察时间），如图3-1所示。因此，它特别适用于指定瞬态、边界最大漂移和控制频率偏移。有关MTIE的更多信息，请参阅ANSI中的附录CT1.101。

TDEV[或δx（τ）]以时间单位（例如，纳秒）表示，是时间方差的平方根（TVAR），其数学定义见第3.12节。给定积分时间的TDEV本质上是通过带通滤波器测量的定时信号的相位噪声的均方根能量的计算滤波器的特性由积分时间决定。因此，TDEV对于指定相位噪声的频谱内容。这对于漂移转移要求是必要的指定时钟必须执行的过滤量。它也有助于漂移生成要求限制在各种频率下产生的漂移，从而可以通过下游时钟进行滤波，以及可以控制网络漂移累积。有关TDEV的更多信息，请参阅资料性文档ANSI T1.101的附录D。
在评估TDEV结果时，重要的是要认识到TDEV是一个统计参数，因此具有必须考虑的有限信心。一般来说，当根据在较长测量周期内收集的数据计算（即测量的置信度随着测量周期与积分时间的比率的增加而提高）。然而关系是一个正在研究的问题。在制定任何额外的指导方针之前，一种方法是仅将TDEV结果用于积分时间，该积分时间是总测试时间的某个特定部分。对于例如，实验室测试产品是否符合适用的漂移生成要求可能决定只使用集成时间，最多为总测试时间的十分之一。因此，为了测量集成时间高达10000秒，需要100000秒的数据。