1、石英晶体振荡器中英文翻译一、石英晶体振荡器的基本原理1、石英晶体振荡器的结构 石英晶体振荡器是利用石英晶体（二氧化硅的结晶体）的压电效应制成的一种谐振器件，它的基本构成大致是：从一块石英晶体上按一定方位角切下薄片（简称为晶片，它可以是正方形、矩形或圆形等），在它的两个对应面上涂敷银层作为电极，在每个电极上各焊一根引线接到管脚 上，再加上封装外壳就构成了石英晶体谐振器，简称为石英晶体或晶体、晶振。其产品一般用金属外壳封装，也有用玻璃壳、陶瓷或塑料封装的。2、压电效应若在石英晶体的两个电极上加一电场，晶片就会产生机械变形。反之，若在晶片的两侧施加机械压力，则在晶片相应的方向上将产生电场，这种物理现
2、象称为压电效应。如果在晶片的两极上加交变电压，晶片就会产生机械振动，同时晶片的机械振动又会产生交变电场。在一般情况下，晶片机械振动的振幅和交变电场的振幅非常微小，但当外加交变电压的频率为某一特定值时，振幅明显加大，比其他频率下的振幅大得多，这种现象称为压电谐振，它与LC回路的谐振现象十分相似。它的谐振频率与晶片的切割方式、几何形状、尺寸等有关。3、符号和等效电路当晶体不振动时，可把它看成一个平板电容器称为静电电容C，它的大小与晶片的几何尺寸、电极面积有关，一般约几个PF到几十PF。当晶体振荡时，机械振动的惯性可用电感L来等效。一般L的值为几十mH 到几百mH。晶片的弹性可用电容C来等效，C的值
3、很小，一般只有0.00020.1pF。晶片振动时因摩擦而造成的损耗用R来等效，它的数值约为100。由于晶片的等效电感很大，而C很小，R也小，因此回路的品质因数Q很大，可达100010000。加上晶片本身的谐振频率基本上只与晶片的切割方式、几何形状、尺寸有关，而且可以做得精确，因此利用石英谐振器组成的振荡电路可获得很高的频率稳定度。4、谐振频率从石英晶体谐振器的等效电路可知，它有两个谐振频率，即（1）当L、C、R支路发生串联谐振时，它的等效阻抗最小（等于R）。串联揩振频率用fs表示，石英晶体对于串联揩振频率fs呈纯阻性，（2）当频率高于fs时L、C、R支路呈感性，可与电容C。发生并联谐振，其并联
4、频率用fd表示。根据石英晶体的等效电路，可定性画出它的电抗频率特性曲线。可见当频率低于串联谐振频率fs或者频率高于并联揩振频率fd时，石英晶体呈容性。仅在fsffd极窄的范围内，石英晶体呈感性。二、石英晶体振荡器类型特点石英晶体振荡器是由品质因素极高的石英晶体振子（即谐振器和振荡电路组成。晶体的品质、切割取向、晶体振子的结构及电路形式等，共同决定振荡器的性能。国际电工委员会（IEC）将石英晶体振荡器分为4类：普通晶体振荡（SPXO），电压控制式晶体振荡器（VCXO），温度补偿式晶体振荡（TCXO），恒温控制式晶体振荡（OCXO）。目前发展中的还有数字补偿式晶体损振荡（DCXO）等。普通晶体振荡
5、器（SPXO）可产生10(-5)10(-4)量级的频率精度，标准频率1100MHZ，频率稳定度是100ppm。SPXO没有采用任何温度频率补偿措施，价格低廉，通常用作微处理器的时钟器件。封装尺寸范围从21146mm及53.21.5mm。电压控制式晶体振荡器（VCXO）的精度是10(-6)10(-5)量级，频率范围130MHz。低容差振荡器的频率稳定度是50ppm。通常用于锁相环路。封装尺寸14103mm。温度补偿式晶体振荡器（TCXO）采用温度敏感器件进行温度频率补偿，频率精度达到10(-7)10(-6)量级，频率范围160MHz，频率稳定度为12.5ppm，封装尺寸从303015mm至11.
6、49.63.9mm。通常用于手持电话、蜂窝电话、双向无线通信设备等。恒温控制式晶体振荡器（OCXO）将晶体和振荡电路置于恒温箱中，以消除环境温度变化对频率的影响。OCXO频率精度是10(-10)至10(-8)量级，对某些特殊应用甚至达到更高。频率稳定度在四种类型振荡器中最高。三、石英晶体振荡器的主要参数晶振的主要参数有标称频率，负载电容、频率精度、频率稳定度等。不同的晶振标称频率不同，标称频率大都标明在晶振外壳上。如常用普通晶振标称频率有：48kHz、500 kHz、503.5 kHz、1MHz40.50 MHz等，对于特殊要求的晶振频率可达到1000 MHz以上，也有的没有标称频率，如CRB
7、、ZTB、Ja等系列。负载电容是指晶振的两条引线连接IC块内部及外部所有有效电容之和，可看作晶振片在电路中串接电容。负载频率不同决定振荡器的振荡频率不同。标称频率相同的晶振，负载电容不一定相同。因为石英晶体振荡器有两个谐振频率，一个是串联揩振晶振的低负载电容晶振：另一个为并联揩振晶振的高负载电容晶振。所以，标称频率相同的晶振互换时还必须要求负载电容一至，不能冒然互换，否则会造成电器工作不正常。频率精度和频率稳定度：由于普通晶振的性能基本都能达到一般电器的要求，对于高档设备还需要有一定的频率精度和频率稳定度。频率精度从10(-4)量级到10(-10)量级不等。稳定度从1到100ppm不等。这要根
8、据具体的设备需要而选择合适的晶振，如通信网络，无线数据传输等系统就需要更高要求的石英晶体振荡器。因此，晶振的参数决定了晶振的品质和性能。在实际应用中要根据具体要求选择适当的晶振，因不同性能的晶振其价格不同，要求越高价格也越贵，一般选择只要满足要求即可。四、石英晶体振荡器的发展趋势1、小型化、薄片化和片式化：为满足移动电话为代表的便携式产品轻、薄、短小的要求，石英晶体振荡器的封装由传统的裸金属外壳覆塑料金属向陶瓷封装转变。例如TCXO这类器件的体积缩小了30100倍。采用SMD封装的TCXO厚度不足2mm，目前53mm尺寸的器件已经上市。2、高精度与高稳定度，目前无补偿式晶体振荡器总精度也能达到
9、25ppm，VCXO的频率稳定度在107范围内一般可达20100ppm，而OCXO在同一温度范围内频率稳定度一般为0.00015ppm，VCXO控制在25ppm以下。3、低噪声，高频化，在GPS通信系统中是不允许频率颤抖的，相位噪声是表征振荡器频率颤抖的一个重要参数。目前OCXO主流产品的相位噪声性能有很大改善。除VCXO外，其它类型的晶体振荡器最高输出频率不超过200MHz。例如用于GSM等移动电话的UCV4系列压控振荡器，其频率为6501700 MHz，电源电压2.23.3V，工作电流810mA。4、低功能，快速启动，低电压工作，低电平驱动和低电流消耗已成为一个趋势。电源电压一般为3.3V
10、。目前许多TCXO和VCXO产品，电流损耗不超过2 mA。石英晶体振荡器的快速启动技术也取得突破性进展。例如日本精工生产的VG2320SC型VCXO，在0.1ppm规定值范围条件下，频率稳定时间小于4ms。日本东京陶瓷公司生产的SMD TCXO，在振荡启动4ms后则可达到额定值的90%。OAK公司的1025 MHz的OCXO产品，在预热5分钟后，则能达到0.01 ppm的稳定度。五、石英晶体振荡器的应用1、石英钟走时准、耗电省、经久耐用为其最大优点。不论是老式石英钟或是新式多功能石英钟都是以石英晶体振荡器为核心电路，其频率精度决定了电子钟表的走时精度。从石英晶体振荡器原理的示意图中，其中V1和
11、V2构成CMOS反相器石英晶体Q与振荡电容C1及微调电容C2构成振荡系统，这里石英晶体相当于电感。振荡系统的元件参数确定了振频率。一般Q、C1及C2均为外接元件。另外R1为反馈电阻，R2为振荡的稳定电阻，它们都集成在电路内部。故无法通过改变C1或C2的数值来调整走时精度。但此时我们仍可用加接一只电容C有方法，来改变振荡系统参数，以调整走时精度。根据电子钟表走时的快慢，调整电容有两种接法：若走时偏快，则可在石英晶体两端并接电容C，如图4所示。此时系统总电容加大，振荡频率变低，走时减慢。若走时偏慢，则可在晶体支路中串接电容C。如图5所示。此时系统的总电容减小，振荡频率变高，走时增快。只要经过耐心的
12、反复试验，就可以调整走时精度。因此，晶振可用于时钟信号发生器。2、随着电视技术的发展，近来彩电多采用500kHz或503 kHz的晶体振荡器作为行、场电路的振荡源，经1/3的分频得到 15625Hz的行频，其稳定性和可靠性大为提高。面且晶振价格便宜，更换容易。3、在通信系统产品中，石英晶体振荡器的价值得到了更广泛的体现，同时也得到了更快的发展。许多高性能的石英晶振主要应用于通信网络、无线数据传输、高速数字数据传输等。One, the basic principle of quartz crystal oscillator1, the structure of quartz crystal os
13、cillatorQuartz crystal oscillator is using quartz crystal (silica crystals) of the piezoelectric effect a resonant components made, it is the basic constitute roughly from a quartz crystal, by certain azimuth cut chips (referred to as the chips, it can be a square and rectangular or circular etc), i
14、n its two corresponding surface coated with silver layer in each electrode as electrode, the welding a root fuses received tube feet, plus encapsulation enclosure they form a quartz crystal resonator, known as quartz crystals or crystals, crystal vibration. Its products are with metal shell packagin
15、g, useful also glass shell, ceramic or plastic packaging.2, piezoelectric effectIf the two electrodes in quartz crystal add an electric field, chip can produce mechanical deformation. Conversely, if the chip on both sides of the mechanical pressure, is the direction of the chip will produce correspo
16、nding electric field, and the physical phenomenon known as piezoelectric effect. If the extremes of the chip add alternating voltage, chip can produce mechanical vibration, meanwhile the chips mechanical vibration and produces alternating electric fields. Normally, wafer mechanical vibration amplitu
17、de and the amplitude of alternating electric field is very small, but when the frequency of alternating voltage plus for a particular value, amplitude obviously increase, the amplitude frequency than other much, this phenomenon is called piezoelectric resonant with LC circuit, it is very similar to
18、the resonance phenomenon. Its resonance frequency and the chips way to cut, geometric shapes, sizes and so on.Three, symbols and equivalent circuitWhen the crystals can not vibration view it as a plate capacitor called electrostatic capacitive C, its size and the chips dimensions, electrode area, us
19、ually around several PF related to dozens of the ruling zanu-pf. When crystal oscillates, mechanical vibration inertial usable inductance L to equivalent. General L value for decades mH to hundreds of mH. The chips elastic usable capacitance C, C is equivalent to the value of the small, usually only
20、 0.0002 0.1 pF. Chip vibration caused by friction with the loss of its equivalent, R value of roughly 100 . Because the chips equivalent inductance is very big, and C is small, R also small, so the quality factor Q loop is very big, can reach 1,000 to 10,000. Plus the resonance frequency of the chip
21、 itself only to basically chip cutting way, shape and dimension are concerned, and can do it accurate, so using quartz resonator can obtain the oscillating circuit of high frequency stability.4, resonant frequencyFrom quartz crystal resonator equivalent circuit of knowable, it has two resonant frequ
22、ency, namely (1) when L, C, R branch, it happened when the network (minimum equivalent impedance (equal to R). Series wipe frequency use fs says, quartz crystal for frequencies fs is wiped series of pure resistance sex, (2) when frequency than when the fs, R L, C with a sensuous, branch capacitance
23、C. Happen, the parallel resonant frequency with fd said. ParallelBased on the equivalent circuit quartz crystals, qualitative plot its frequency characteristic curve circuit reactance. Visible when frequency below series resonance frequency fs or frequency vibration frequencies than parallel wipe, q
24、uartz crystal fd a capacitive. Only in the fs f fd is extremely narrow range, quartz crystal is sensible.Second, quartz crystal oscillator typesQuartz crystal oscillator is high quality factors by quartz crystal oscillator are (namely resonators and oscillating circuit component. Crystal quality, cu
25、tting orientation, crystal structure of the vibrator and circuit form etc, jointly determine oscillator performance. The international electrotechnical commission (IEC) will be a quartz crystal oscillator is divided into four categories: ordinary crystal oscillation (cspxo), voltage control type cry
26、stal oscillators (VCXO), temperature compensation type crystal oscillation (TCXO), temperature control type crystal oscillation (OCXO). Currently developing and digital compensation type crystal loss oscillation (DCXO), etc.Ordinary crystal oscillators (cspxo) can produce 10 (-5) 10 (-4) middleweigh
27、t frequency accuracy, standard frequency 1-100MHZ, frequency stability is + 100ppm. Cspxo no use any temperature frequency compensation measures, the price is cheap, normally as a microprocessor clock device. Encapsulation size ranges from 21 x 14 x 6mm and 5 x 320 x 1.5 mm.Voltage control type crys
28、tal oscillators (VCXO) precision is 10 (6) 10 (-5) magnitude 1 30MHz frequency range. Low tolerance oscillator frequency stability is + 50ppm. Normally used for phase lock loop. Encapsulation size 14 x 10 x 3mm.Temperature compensating crystal oscillator TCXO) using temperature (temperature sensing
29、device, frequency compensate precision of 10 (frequency 7) 10 (6) middleweight and frequency range 1-60MHz, frequency stability for + 1 + 250 PPM, package sizes from 30 x 30 x 15mm to 11.4 x 960 x 0.39 mm. Normally used for holding the phone, cellular telephones, two-way wireless communication equip
30、ment, etc.Temperature control type crystal oscillators (OCXO) will crystals and oscillating circuit in a climate-controlled case, in order to eliminate environmental temperature change on frequencies. OCXO frequency 10 (accuracy is 10 (-) to 10 8) middleweight, for some special application even reac
31、h higher. Frequency stability in the four types oscillator highest.Third, the main parameters of quartz crystal oscillatorThe main parameters of crystals have a nominal frequency, load capacitance, frequency precision, frequency stability, etc. Different crystals nominal frequency is different, most
32、ly in nominal frequency indicate the crystals. Such as crystals used ordinary nominal frequency is: 503.5 kHz, 48kHz, 500 MHz kHz, 40.50 1MHz for special requirements, such as the crystal frequency can achieve 1000 MHz above, also some no nominal frequency, such as CRB, ZTB, Ja series etc. Load capacitance refers to connect the two leads crystals IC bloc
