1、r I a In I w l- a - EIA 532-3 90 W 3234b00 0072873 8 = APPROVED: November 12, 1990 EIA STANDARD Standard Methods dor Measurement of the Equivalent Electrical Parameters of Quartz Crystal Units, 1 kHz to 1 GHz EIA-512-6 (Addendum No. 1 to EIA-512) DECEMBER 1990 ELECTRONIC INDUSTRIES ASSOCIATION ENGIN
2、EERING DEPARTMENT EIA 512-1 90 3234b00 0072872 T W D b NOTICE EIA Engineering Standards and Publications are designed to serve the public interest through eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products, and assisting th
3、e purchaser in selecting and obtaining with minimum delay the proper product for his particular need. Existence of such Standards and Publications shall not in any respect preclude any member or nonmember of EL4 from manufacturing or selling products not conforming to such Standards and Publications
4、, nor shall the existence of such Standards and Publications preclude their voluntary use by those other than EIA members, whether the standard is to be used either domestically or internationally. Recommended Standards and Publications are adopted by EL4 without regard to whether their adoption may
5、 involve patents on articles, materials, or processes. By such action, ETA does not assume any liability to any patent owner, nor does it assume any obligation whatever to parties adopting the Recommended Standard or Publication. This EIA Standard is considered to have International Standardization
6、implication, but the International Electrotechnical Commission activity has not progressed to the point where a valid comparison between the EIA Standard and the IEC document can be made. This Standard does not purport to address all safety problems associated with its use or all applicable regulato
7、ry requirements. It is the responsibility of the user of this Standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations before its use. (From Standards Proposal No. 2200 formulated under the cognizance of the EIA P-11 Committee on Quar
8、tz Crystals.) COPYRIGHT 1991 Published by ELECTRONIC INDUSTRIES ASSOCIATION Engineering Department 2001 Pennsylvania Ave. N.W., Washington, D.C. 20006 PRICE: Please refer to the current Catalog of EIA even users who buy “complete“ measurement systems, which include equipment, fixtures, and software,
9、 must still be aware of how to make accurate measurements and how to verify system performance. This guide will provide the needed information to do so, EIA-512 is complete in describing scattering parameter (S-parameter) theory, error correction techniques and in deriving the quartz crystal electri
10、cal parameter equations. For that reason, no attempt is made to review or summarize the standard. Instead, only information that adds to the understanding and use of the standard is included in the guide. Some material from the IECs Technical Committee No. 49 document, “A Guide To The Measurement of
11、 Equivalent Parameters Of Quartz Crystal Units“ was used in preparing this guide. EIA 512-1 90 W 3234600 0072875 5 M EIA-5 12 - 1 Page 2 2.0 OVERVIEW OF MEASUREMENT METHODS 2.1 EQUIVALENT NETWORKS A proper equivalent circuit should represent the entire crystal unit as seen from the reference plane a
12、t the test fixture. It should include all the effects of leads, mountings and enclosure. It should also include crystal parameter dependency on frequency, drive level, and temperature. The effects of any mechanically or electrically coupled modes should be taken into account. Except for any nonlinea
13、r amplitude behavior, a quartz crystal unit can be quite accurate1 represented by the equivalent circuit in Figure 2.1 A description of each circuit element I ollows: cPl The electrical surrounding ground planes. capacitance between each connecting pin and the The electrical capacitance between the
14、pins. The equivalent resistances of the mounting structure. The electrical capacitance between the two electrodes. The electrical capacitances between the electrodes and the surrounding ground planes. The resistance between the electrodes. cPP Rpl, Rp2 Ce Ce19Ce2 RS I The equivalent electrical param
15、eters of the design mode of resonance. R,N, L,N, C1,N The equivalent electrical parameters of other modes of resonance. here so that the user is aware that complete characterization of a quartz crystal requires careful interpretation of measurements. The frequency and quality of the unit under test
16、should be taken into account. Fortunately, this degree of sophistication is seldom needed. The circuit is reproduced For most applications the following conditions are valid: a) Within a couple of percent frequency range of the mode of interest, there are no effects of interfering modes. Stated anot
17、her way, R1, L1, C1 are constant over the frequency range of interest. b) $1 =RPl2+ ($1)/ and Xp2=Rp22+ are each much less than XI = R12+ (wL1- l/wCl) 3 2 1/2 -EIA 512-1 90 3234600 0072876 7 W (This condition should be checked for frequencies above 300 MHz.) c) R, Xi The following terms can be combi
18、ned: EIA- 5 12 - 1 Page 3 e) Co = Ce + Cpp This results in the simplified equivalent circuit of Figure 2.2a for a two-port, three terminal quartz crystal. For a one-port measurement, the stray capacitances are combined with Co and the equivalent circuit can be represented as shown in Figure 2.2b. Th
19、is circuit representation is also used for glass enclosed quartz crystals regardless of whether the two-port or one-port method is used. Since the stray capacitances will differ in each case, the values of Co will not be the same. (Fs) (the series resonance frequency of the series arm) is relatively
20、 independent of Co and any stray capacitance, it should be used to correlate EIA-512 one-port and two-port d measurements. When selecting crystals to correlate other measurement systems, select those units that do not show motional parameter dependency on small variations in drive level. Also select
21、 units that exhibit a good circle fit in the admittance plane. A good fit guarantees that there are no interfering modes of vibration over the frequency range used for the measurement. Units that are not “well behaved“ cannot be represented by the simplified equivaIent network. They can still be mea
22、sured using EIA-512 but attempts to correlate these measurements with other test systems will yield erroneous results. 2.2 CLASSIFICATION OF MEASUREMENT SYSEMS In the general case the quartz crystal unit must be treated as a three terminal network the third terminal being in the typical case a metal
23、 enclosure, which should be grounded. Three types of connection of the crystal unit are possible : -One-port (two-terminal) in which one of the pins (leads) is grounded while the enclosure is floating; -One-port (two-terminal) in which one of the pins (leads) is grounded and the enclosure is also gr
24、ounded; a -Two-port (three-terminal connection in which only the enclosure is grounded. EIA 512-1 90 3234b00 0072877 9 EIA-512-1 Page 4 The true values of the motional arms of the quartz crystal unit equivalent circuit (for the main resonance : series resonance frequency Fs, motional resistance R1 a
25、nd motional capacitance C1 or inductance L1) are practically independent of the type of connection. The type of connection strongly influences the distributed (static) capacitances. The influence of distributed capacitance is different in various measuring methods and different applications, so it i
26、s important to specify the crystal pin connection to be used. In the general case, the characterization of quartz crystal units requires many measurements made at different frequencies near series resonance, and it is rather complex to form an estimate of the equivalent circuit parameters that will
27、best approximate the electrical behavior of the unit. Fortunately, in most cases only a few of the crystal equivalent parameters need be determined, particularly in the production environment. The most important are two parameters: series resonance frequency Fs, and motional resistance R1; in a larg
28、e number of cases, these may be approximated measurement of zero-phase frequency fr and zero-phase insertion resistance Rr. These latter two parameters may be measured with limited accuracy by simple and fast single frequency methods. From the point of view of general principle the most important me
29、asuring methods may be classified as follows: Q A. Oscillator methods (also called active methods) in which the frequency of oscillation of special oscillator circuits, into which the crystal unit to be measured is connected, is measured and assumed to be the zero-phase frequency of the crystal unit
30、. B. Transmission methods in which the crystal unit parameters determined indirectly from measurements of the transfer function of the network formed by connecting the crystal unit (enclosure grounded) into a resistive network. Transmission methods may be divided into four subgroups: 1. Extremum tra
31、nsmission methods (ETM) in which is used only information about the magnitude of the transfer function. The crystal unit frequency is identified as that at which the extremum (maximum) output voltage occurs. 2. Phase transmission methods (PTM) in which we use information about the transfer function
32、phase. The crystal unit frequency is identified as that at which the output voltage phase is the same as that obtained during preliminary calibration) in the ideal case the output voltage is in phase with the input voltage) . In these methods amplitude information is not needed to establish frequenc
33、y of the unit, but must be obtained if the insertion resistance is to be calculated. Measuring sets using - or T- transmission networks are the most important examples of equipment used for ETM or FTM. 3. Vector transmission methods (VTM) in which information about both the amplitude and phase of th
34、e transfer function is needed. In contrast to the ETM and PTM, which are fundamentally single frequency measurements, VTM typically require measurements at several frequencies near resonance so that motional capacitance (or inductance) may also be determined. al 4. Scattering Darameter methods (SPM)
35、 in which all four of the two-port scattering parameters of the three-terminal crystal unit connection are determined, and fully corrected for linear errors in measuring system and fixtures, at several frequencies EIA 512-1 90 W 3234600 0072878 O W EIA-512-1 Page 5 near series resonance of the devic
36、e. Such measuring sets require the use of dual-directional couplers and vector detectors, such as those incorporated in network analyzers. C. Impedance (admittance) measuring methods in which one-port quartz crystal unit parameters are determined using the vector values of the crystal unit impedance
37、 (admittance) measured at several frequencies near resonance. The method of calculation is the same as for the SPM above, but the crystal is connected as a one-port (with one pin/lead grounded). Two subgroups of impedance measurement may be distinguished: 1. Direct immittance methods (DIM) in which
38、equipment is used which reads out directly impedance (or admittance values) (e.g., various bridges or vector immittance meters). 2. Reflection coefficient methods (RCM) in which the quartz crystal unit parameters are determined from the vector values of the reflection coefficient of the crystal unit
39、 connected to a system port of known impedance, at several frequencies. 2.3 AUTOMATED NETWORK ANALYZER METHODS Automatic two-port network analyzers have been developed for the general characterization of active and passive networks. These anaIyzers provide for the determination of the two-port scatt
40、ering parameters of the network under test, and provide for correction of the measured responses to take into account imperfections in the equipment by referring network parameters to the network analyzer .S-parameter instruments of this type are now available. For use as crystal measurement systems
41、, stable synthesized signal sources must be included in the system; some systems include such sources while others need to be modified for this use. Such systems provide for calibration at the measurement reference plane with coaxial impedance standards, and are capable of very accurate and reproduc
42、ible measurements. The use of the scattering parameter methods, originally developed for application to microwave systems, allows for the separation of the trans-immittance parameters from the effects of shunt elements, so test the C13 and C23 static capacitances may be separated from the transmissi
43、on characteristics, and determined separately. Also, the test fixture imperfections are to at least a first approximation removed from the measurement, as the “Calibration“ of the system is done at the measurement ports, and the error correction algorithms from the measurements the effects of the sy
44、stem up to the reference plane. These automatic network analyzer systems have proven to be the most satisfactory way of obtaining precise measurements of immittance over very wide frequency ranges. Either one-port reflection measurements or two-port transmission measurements may be made as desired.
45、For crystal unit measurements, the choice of one-port or two-port measurement is generally arbitrary, as the two yield essentially identical values for the motional parameters, differing only in the values of the static capacitances. As a guide, the following are general recommendations. L One-port
46、measurements - Low resistance crystals (RI 100 ohms); crystals for filter 7. Fr EIA 512-1 90 m 3234b00 O072879 2 m EIA-512-1 Page 6 use and some exacting oscillator applications; high frequency crystals (Fs 100 MHz) . 2.4 COMPARISON MEASUREMENT METHODS Test and measurement of crystal units in a prod
47、uction facility pose some unique problems. Generally, high through-put is required, and devices are checked against specified tolerances on a “go“ or “no-go“ basis. In most cases not all parameters are specified, and testing may be limited to include only those specified parameters together with any
48、 additional measurements needed to assess the general quality of the product. Obviously, all devices need to be tested against specified parameter value tolerances; quality assessment may be implemented on a sampling basis, especially if production quantities are large. The equipment used for produc
49、tion testing can be selected on the basis of device requirements; i.e. , if only frequency and resistance are specified, then relative1 simple oscillator or transmission test facilities are adequate. The degree of automation o ty the test equipment will depend upon the quantity of product involved. The advantage of higher capacitance and better reproducibility of data resulting from automated testing are usually sufficient justification in themselves. When some portion of the product will require measurement of L1 (Ci) values, and/or determination of load parameters, FI, RL, and
