JP2001124809A - Method of measuring quartz oscillator with load capacity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring method capable of accurately measuring characteristics with a network analyzer even if a stray capacitance is present in a measuring jig for a quartz oscillator with load capacity. SOLUTION: The quartz oscillator with load capacity is measured in such a way that (1) the solution expression of a mathematical expression obtained by the cascade connection of a measurement system to four terminal nets, α=Vr/Va=(K1+K2Zx+K3Zc+K4ZxZc) is used; (2) a quartz oscillator part and a load capacity part are short-circuited and measurement is conducted to obtain K1; (3) a known amount of resistance is loaded to the quartz oscillator part, the load capacity part is short-circuited, and measurement is conducted to obtain K2; (4) the quartz oscillator part is short-circuited, a known amount of capacity is loaded to the load capacity part, and measurement is conducted to obtain K3; (5) a known amount of resistance is loaded to the quartz oscillator part, capacity is loaded to the load capacity part, and measurement is conducted to obtain K4; (6) a quartz oscillator to be measured is loaded to the quartz oscillator part, capacity is loaded to the load capacity part, and measurement is conducted to obtain α; and (7) the measured value is substituted for the mathematical expression to obtain impedance Zx of the quartz oscillator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network analyzer (hereinafter referred to as "DUT") for measuring various impedances and the like even if a stray capacitance exists in a measuring jig of the crystal unit with a load capacitance. ) Relates to a measurement method capable of performing measurement with extremely high accuracy.

[0002]

2. Description of the Related Art First, a crystal resonator will be described in some detail. FIG. 4 shows an electrical equivalent circuit near the main resonance frequency of the crystal unit 41. Here, Co is the sum of the capacitance between the electrodes and the stray capacitance between the terminals and the like, and is generally called a parallel capacitance. L1 and C1 are equivalent constants of the crystal resonator as an electromechanical vibration system. R1 is an equivalent constant representing the loss of vibration. Therefore, the resonance frequency of the crystal resonator is fo = 1 / 2π√ (L1 · C1), and the anti-resonance frequency is represented by fa = fo (1+ (C1 / 2Co)). Therefore, when a characteristic test of a single water supply vibrator is performed by using a network analyzer, measured data can be obtained relatively accurately.

By the way, most users who use the crystal unit 41 as an oscillator element use a crystal unit and a load capacitor connected in series, such as a Colpitts oscillator. FIG. 5A shows a configuration diagram in which a crystal unit 41 and a load capacitor 42 are connected in series. Therefore, accurate measurement data in which a crystal oscillator and a load capacitor are connected in series is desired for both the manufacturer and the user in the specification or in actual use. As a solution to this, there is a concept that a device in which a crystal unit 41 and a load capacitor 42 are connected in series is regarded as one component.

[0004] In theory, the crystal oscillator 41 has a load capacitance 4
Even if 2 are connected in series, the electrical equivalent circuit can be displayed as in FIG. However, FIG.
As shown in FIG. That is, the equivalent constant of the equivalent circuit taking into account the load capacitance 42 is converted into the equivalent constant of FIG.
1 is converted to L'1, C1 is converted to C'1, and R is converted to R'1. Although this conversion formula is publicly known and omitted, the oscillation frequency at this time is increased by Δf. That is, assuming that the difference from the oscillation frequency fo of a single unit is Δf, the following equation is approximately obtained. Δf / fo = C1 / (2 (Co + CL)). Here, CL is the capacitance value of the load capacitance 42.

FIG. 6 shows a measurement configuration diagram of a DUT 40 in which a load capacitance 42 is connected in series to a quartz oscillator 41. Here, the network analyzer (NA) 50 will be described briefly. A network analyzer is a measuring instrument that analyzes transmission characteristics and reflection characteristics of a linear network using sine waves.

The front of the network analyzer 50 is
For example, a switch group 51 for setting measurement parameters and a display unit 52
OUT terminal 54, Rch terminal 56, Ach terminal 58, B
There are input / output terminals such as ch. Rch is an input terminal serving as a reference signal of a measurement signal in DUT (device under test) measurement. Ach and Bch are terminals for inputting signals output from the DUT. The network analyzer performs various analyzes by calculating the data of the input signal of Ach or the input signal of Bch based on the data of the signal input to Rch. In this specification, A
Explain in ch.

The main components of the internal configuration of the network analyzer are an analog signal source for generating a measurement signal, a plurality of so-called digital voltmeters for inputting and measuring a received signal, and a digital voltage generator (not shown). A calculating unit for calculating the measured value of the meter to obtain the impedance of the DUT,
It is a control unit for controlling the whole. Therefore, as shown in FIG. 6, an OUT terminal 54 which is an output terminal of the network analyzer 50 is connected to an analog signal source 55 such as a synthesizer and outputs a measurement signal. The Rch terminal 56 and the Ach terminal 58, which are input terminals, are connected to a so-called digital voltmeter 57, a digital voltmeter 59, or the like, which obtains an amplitude level by a digital value using an analog / digital converter.

As shown in FIG. 6, the means for measuring the DUT 40 includes an OUT terminal 5 of a network analyzer 50.
DUT that outputs a measurement signal from DUT 4 and has DUT 40 mounted
The signal is supplied to the input terminal 43 of the case 39 and the Rch terminal 56 of the network analyzer 50. The output signal of the DUT 40 is supplied from the output terminal 44 of the DUT case 39 to the Ach terminal 58 of the network analyzer 50.

The measurement signals input to the Rch terminal 56 and the Ach terminal 58 measure the voltage value and the phase value of each amplitude level, and the arithmetic unit uses the data to determine the amplitude level difference and position of the two. By calculating the phase difference, the impedance, the resonance frequency fo, the anti-resonance frequency fa, and the like of the DUT 40 are obtained.

In the test of the quartz oscillator, the test is generally performed using the above-mentioned general-purpose network analyzer, but the present invention is not limited to the general-purpose network analyzer. There are also dedicated measuring instruments that eliminate unnecessary parts with similar specifications. In this specification, those having the same basic operation, including these similar measuring instruments, are included in the network analyzer.

By the way, when measuring the DUT 40 of the crystal resonator with the load capacitance, as shown in FIG. 3A, an error occurs in the measurement result due to the admittance of the stray capacitance Y present in the jig such as the DUT case 39. Has occurred. Further, as shown in FIG. 3 (B), the even when such can change the variable capacitor diode 42 ₂ continuously capacitance value by changing the bias voltage used as the load capacitance, due to the resistance Z like for bias voltage application Admittance causes errors in the measurement results.

In order to compensate for these errors, the present applicant has filed Japanese Patent Application No. 5-27086 (Japanese Patent Application Laid-Open No. Hei 7-104017).
A "method of measuring load capacity characteristics considering residual capacity" has been disclosed. The gist of this application is to measure (a) the αs value when the DUT section is short-circuited and the load capacitance section is short-circuited, for the ratio α = V / v between the output voltage and the input voltage at the time of resonance,
(B) A predetermined known amount is loaded into the DUT unit, and the αL value when the load capacitance unit is short-circuited is measured. (C) DUT
Section is short-circuited, and the αs ′ value when a predetermined known amount is loaded to the load capacitance section is measured.

The impedance Zo when the crystal oscillator is opened by calculation, the impedance Zs when the crystal oscillator is short-circuited, and the impedance ZL when the crystal oscillator is loaded with a certain known amount.
Is obtained, and the solution between the actual measurement value and the arithmetic expression is obtained to determine the residual capacity. Further, the true resonance frequency at the time of the load capacity is obtained by correcting the residual capacity.

[0014]

SUMMARY OF THE INVENTION This Japanese Patent Application No. 5-273 is disclosed.
The technology of the measurement method at the time of filing of the application 086 has provided a significant improvement over previous measurement methods. However, as described above, this measuring method actually measures three measured values of the αs value, the αL value, and the αs ′ value, while calculating Z
O, Zs, and ZL are obtained, and the solution between them is obtained to obtain the residual capacity. Therefore, this measurement method
Since it is an actual measurement value of only points, it is a means for obtaining a high-level approximation value.

It is an object of the present invention to perform a characteristic test of a crystal unit having a load capacitance, and to measure various characteristics of the crystal unit with extremely high precision by actually measuring five points even if a stray capacitance exists in a measuring jig. It provides a possible measurement method. Furthermore, even if the load capacitance value at the time of measurement and the load capacitance value to be standardized are different, a measurement method capable of converting the load capacitance value to be normalized into various characteristics of the DUT based on a known load capacitance value is provided. It is. Furthermore, the applicant has filed a separate application for a utility model registration application on the same day as a “measurement jig for a crystal unit with a load capacitance”.
Provides a method of measuring a crystal unit with a load capacitor that can accurately measure only the load capacitance value at any time, and that can change the load capacitance value due to temperature etc. and measure the data at that point with extremely high accuracy. Is what you do.

[0016]

In order to achieve the above-mentioned object, the present invention provides a solution of a mathematical expression in which the configuration of a measuring system is cascade-connected with a four-terminal network, α = Vr / Va = (K1 + K2Zx + K3Zc).
+ K4ZxZc) (Equation 8) to obtain five unknown coefficients,
An accurate value is obtained based on the actually measured values of the K1, K2, K3, K4, and α values. Therefore, an accurate value of the impedance Zx of the crystal resonator can be obtained by calculation. These detailed descriptions will be described in the section of the embodiment of the invention.

In the conventional measuring means, the capacitance value is obtained by measuring the load capacity used for the measurement in advance. Although the measurement was performed based on the value, the load capacity value changed with temperature or with time, and accurate measurement could not be performed due to the influence.

Further, using a “measuring jig for a quartz oscillator with a load capacitance” filed by the present applicant on the same day as a utility model registration,
If the impedance Zcf of only the load capacitance is measured at any time by switching the switch, the above-described measurement of the crystal resonator with the load capacitance can be performed with a value close to the truth and with high accuracy. Next, the configuration of the present invention will be described.

The first invention is a basic invention. That is,
A measurement method for measuring various characteristics of a crystal resonator with a load capacitance as a DUT with a network analyzer,
The answer to the equation in which the measurement system is cascaded in a four-terminal network, α = Vr
/ Va = (K1 + K2Zx + K3Zc + K4ZxZc) (Equation 8)
And the crystal unit is shorted to Zx = 0,
The load capacitance section is short-circuited to set Zc = 0, actual measurement is performed to obtain K1, a predetermined known amount of resistance is loaded to the crystal unit, and Zx = ZL is set. Is measured and calculated to obtain K2, the crystal unit is short-circuited to set Zx = 0, a load of a predetermined known amount is loaded to the load capacity unit, and Zc is set to Zcf. Then, a certain known amount of resistance is loaded into the crystal unit and Zx = ZL, and a certain known amount of capacitance is loaded into the load capacitance unit and Zc = Zcf.
Load the crystal unit to be measured in the crystal unit and load Zx
= Zx, a load of a predetermined known amount is loaded into the load capacity section, Zc = Zcf, and α is obtained by actual measurement, and the K1, K2, K3, K4, and α values obtained by actual measurement are obtained. Is substituted into the above (Equation 8) to calculate the impedance Zx of the crystal resonator to calculate the crystal resonator with the load capacitance.

The second invention is a method for measuring and calculating a standardized crystal unit having a load capacitance. In other words, this is a method of measuring a crystal resonator with a load capacitance by adding a normalized load capacitance Zct to the impedance Zx of the crystal resonator obtained in the first invention to obtain a normalized crystal resonator with a load capacitance.

According to the third invention, in order to measure with higher accuracy,
This is a method of measuring using a “measurement jig for a crystal unit with a load capacitance” filed by the applicant on the same day as a utility model registration application. That is, in the first invention or the second invention, when measuring the crystal resonator with the load capacitance with the network analyzer, the measurement signal is switched by a switch and the measurement jig which can measure the impedance Zcf of only the load capacitance of the load capacitance portion at any time. This is a method for measuring a quartz resonator with a load capacitance to be measured.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings. FIG. 1 is a block diagram showing a method for measuring a crystal unit with a load capacitance according to the present invention. FIG. 2 is a diagram showing a method for measuring a crystal unit with a load capacitance according to the present invention using a "Digital jig for a crystal unit with a load capacitance". FIG. 4 shows a configuration diagram suitable for measurement. First, FIG. 1 will be described.

The admittance Y of the stray capacitance exists between the crystal resonator with the load capacitance and the DUT housed in the DUT case 39 and the ground. FIG. 1 is a block diagram showing a method of measuring the DUT. A so-called digital voltmeter 57 composed of an analog signal source 55 for generating a measurement signal and an analog / digital converter
And 59 are configured inside the network analyzer.

The measurement signal (voltage V, current I) generated by the analog signal source 55 has two branches. One measurement signal is transmitted to the DUT case 3 via the measurement signal transmission path 21.
9 is applied to the quartz oscillator 41. DUT case 39
Inside the crystal oscillator 41, the stray capacitance Y, and the load capacitance 4
2 are connected in cascade. The output signal from the DUT is
The voltage Va and the current Ia of the measurement signal are supplied to the digital voltmeter 59 of Ach of the network analyzer via the transmission path 22 of the measurement signal. When this is expressed by the mathematical expression of the cascade connection of the four-terminal network, it becomes (Equation 1) of Expression 1.

[0025]

(Equation 1)

In equation (1), A1, B1, C1, D
1 is a four-terminal constant of the transmission path 21 of the measurement signal, Zx is the impedance of the crystal oscillator, Y is the admittance of the stray capacitance, Zc is the impedance of the load capacitance, and A2, B2, C2, D2 Is the transmission path 22 of the measurement signal.
Terminal constant.

The other measurement signal from the analog signal source 55 is supplied via the measurement signal transmission line 20 to the voltage V of the measurement signal.
The r and the current Ir are supplied as reference signals to the digital voltmeter 57 of Rch of the network analyzer. If this is expressed by the mathematical expression of the cascade connection of the four-terminal network, it becomes (Equation 2) of Expression 2. Here, A3, B3, C3, and D3 are the transmission paths 20 of the measurement signal.
Is a four-terminal constant.

[0028]

(Equation 2)

V and I in Equations 1 and 2 are equal. Further, assuming that the input impedance of the digital voltmeters 57 and 59 of the network analyzer is infinite,
Ia in Equation 1 and Ir in Equation 2 are infinitesimally zero. Therefore, when the calculation is performed using Expressions 1 and 2, Expression 3 of Expression 3 is obtained.

[0030]

(Equation 3)

Next, assuming that the coefficients are K1 (Equation 4), K2 (Equation 5), K3 (Equation 6), and K4 (Equation 7) as shown in Expression 4, Vr and Va are the answer equations to be obtained. Α = Vr
/ Va is as shown in Equation 8 of Equation 5.

[0032]

(Equation 4)

[0033]

(Equation 5)

The coefficients K1 and K of (Equation 8) shown in Expression 5
2, K3, K4, and α value are obtained by actual measurement, and Equation 5 is a solution equation from Equations 1 (Equation 1) and 2 (Equation 2) of the theoretical equation.
The numerical value of (Equation 8) is determined. Therefore, if the impedance Zc of the load capacitance 42 is known, an accurate impedance Zx of the crystal resonator can be obtained by a calculation based on the actually measured value.

The coefficients of this equation (8), K1, K2, K3,
A measuring method for actually measuring K4 and α value will be described. First, K
Find 1 When the crystal unit is short-circuited, Z
x becomes 0, and Zc also becomes 0 when the load capacitance section is short-circuited. As for the method of short-circuiting, the jig may be replaced with a short-circuiting jig, or a switch may be provided to short-circuit. When Zx = 0 and Zc = 0, (Equation 8)
Is β, β = Vr / Va = K1 and K1 = β
(Equation 9) is obtained by actual measurement.

Next, K2 is obtained. When a predetermined known amount of resistance R is loaded into the crystal unit and Zx = ZL, and the load capacitance unit is short-circuited and Zc = 0, (Equation 8) becomes γ, and γ = Vr / Va = β + K2ZL. K2 = (γ
−β) / ZL (Equation 10) is obtained by actual measurement and calculation.

Next, K3 is obtained. Assuming that the crystal unit is short-circuited and Zx = 0, and a load of a predetermined known amount is loaded into the load capacitance unit and Zc = Zcf, (Equation 8) becomes δ, and δ = Vr / Va = β + K3Zcf. K3 =
(Δ-β) / Zcf (Equation 11) is obtained by actual measurement and calculation.

Next, K4 is obtained. Assuming that a certain known amount of resistance R is loaded into the crystal unit and Zx = ZL, and a certain known amount of capacitance is loaded into the load capacitance unit and Zc = Zcf, (Equation 8) becomes ε and ε = Vr / Va = γ + δ−β
+ K4ZL Zcf, and K4 = (ε−γ−δ + β) /
ZL Zcf (Equation 12) is obtained by actual measurement and calculation.

When K1, K2, K3, and K4 of the measurement system are actually measured and obtained by calculation, the coefficient of (Expression 8) of the measurement system is determined. Thereafter, the impedance Zx of the crystal unit to be continuously measured can be obtained. In other words, if the crystal unit to be measured is loaded into the crystal unit and Zx = Zx, and a predetermined known amount of capacitance is loaded into the load capacitance unit and Zc = Zcf, (Equation 8) is α and α is = Vr / Va = K1 + K
2Zx + K3Zcf + K4ZxZcf (Expression 8) is obtained by actual measurement.

By transforming (Equation 8), Zx = (α−K1
−K3Zcf) / (K2 + K4Zcf) (Equation 13) When K1, K2, K3, K4, and α obtained by actual measurement are substituted, the impedance Zx of the crystal resonator to be measured is obtained by the actual measurement value. Here, Zcf is the impedance value of a fixed known amount of load capacitance. This is the first invention.

Further, in the specifications and catalogs, the DUT
Is often displayed as a normalized value Zct of the load capacitance value, for example, 10 pF or the like. If the load capacitance of a certain known amount used in the actual measurement is, for example, 10.5 pF, the load capacitance Zct is calculated by adding the load capacitance Zct to the impedance Zx of the crystal oscillator obtained above. It can be a crystal oscillator.

In a mathematical expression, Zx + Zct = (α-K
1 + K2Zct-K3Zcf + K4ZcfZct) / (K2 + K
4Zcf) (Expression 14) Since the coefficients and values of this equation are known by actual measurement, they can be immediately obtained by calculation.
This is the second invention.

Further, when the measurement was performed using the “measurement jig for a crystal unit with a load capacitance” shown in the configuration diagram of FIG. Since the impedance Zc of the DUT 42 can be accurately measured at any time, the DUT can be measured with extremely high accuracy even when the capacitance value changes due to a temperature change or a time change.

The point of the measurement jig of FIG. 2 is that the measurement of the DUT and the measurement of only the load capacity of the DUT can be performed independently. That is, when only the load capacitance is measured, the measurement signal from the OUT terminal 54 of the network analyzer 50 is switched by the first switch 15 to the point O which is the connection point between the crystal unit 41 of the DUT 40 and the load capacitance 42. A measurement signal is supplied, and the signal at the point O is switched by the second switch 16 to the Rch terminal 56 of the network analyzer 50.
And the output signal from the load capacity 42
The load capacitance 42 is given to the Ach terminal 58 of the analyzer 50.
This is a measuring jig 10 for a crystal unit with a load capacitance, which also has a function of accurately measuring the impedance Zc only at any time. Therefore, by using this measuring jig, all the values of the solution equation (Equation 8) obtained from Equations 1 and 2 of the theoretical equation can be obtained by actual measurement, and D
UT can be measured. This is the third invention.

[0045]

As described above in detail, according to the present invention, the solution equation (Equation 8) of Equation 5 obtained from Equation 1 (Equation 1) of Equation 1 and Equation 2 (Equation 2) of Equation 2 can be obtained. Since all values can be obtained by actual measurement, the DUT can be measured with extremely high accuracy.

Therefore, when the DUT is measured by the method for measuring a crystal resonator with a load capacitance according to the present invention, anyone can always obtain the same data. This eliminates the problem that the correlation between the measurement data measured by the company cannot be obtained by each person as in the related art. The present invention has a great technical effect upon implementation.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a method for measuring a crystal resonator with a load capacitance according to the present invention.

FIG. 2 shows a measurement method of the present invention performed by a network analyzer using a measurement jig of a crystal unit with a load capacitance using a DUT.
FIG. 3 is an embodiment of a configuration diagram suitable for measuring the temperature.

FIG. 3 is a circuit diagram in consideration of admittance Y in a DUT case 39 of a crystal resonator with a load capacitor.

FIG. 4 is an electrical equivalent circuit diagram of the crystal unit.

FIG. 5 is a configuration diagram of a crystal resonator with a load capacitor measured in the present invention, and an electrical equivalent circuit diagram thereof.

6 is a measurement configuration diagram of a DUT 40 in which a load capacitance 42 is connected in series to a crystal unit 41. FIG.

[Description of Signs] 10 Measurement jig of crystal resonator with load capacitance 11 Input terminal of OUT signal 15 First switch 16 Second switch 17 Buffer amplifier 20, 21, 22 Transmission path of measurement signal 39 DUT case 40 DUT (DUT) 41) Crystal oscillator 42 Load capacitance 42 ₂ Variable capacitor diode (Load capacitance) 50 Network analyzer (NA) 51 Switch for setting measurement parameters 52 Display unit 54 OUT terminal (Output terminal) 55 Analog signal source 56 Rch Terminal 57 Digital voltmeter 58 Ach terminal 59 Digital voltmeter

Claims (3)

[Claims] 1. A measuring method for measuring various characteristics of a crystal resonator with a load capacitance as a DUT by a network analyzer, wherein a solution equation of an equation in which a measuring system is cascaded to a four-terminal network, α = Vr
/ Va = (K1 + K2Zx + K3Zc + K4ZxZc) (Equation 8)
And (a) short-circuiting the crystal unit to set Zx = 0, short-circuiting the load capacitance unit to set Zc = 0, and measuring K1 by actual measurement. , Zx = ZL, the load capacity section is set as Zc = 0, the actual measurement and calculation are performed, and K2 is obtained. (C) The crystal oscillator section is short-circuited to Zx = 0, and the load capacity section Is loaded with a certain known amount of capacitance (capacitor) and Zc = Zcf
K3 is obtained by actual measurement and calculation, and (d) a predetermined known amount of resistance is loaded into the crystal unit to set Zx = ZL, and a fixed known amount of capacitance is loaded into the load capacitance unit and Zc = Zcf is determined by actual measurement and calculation to obtain K4. (E) The crystal unit to be measured is loaded on the crystal unit and Zx = Zx. Zcf, actual measurement to obtain α, (f) K1 obtained by actual measurement
A method for measuring a crystal unit with a load capacitance, characterized in that the value, K2 value, K3 value, K4 value, and α value are substituted into the above (Equation 8) and operated to obtain the impedance Zx of the crystal unit. 2. A crystal unit with a load capacitance, wherein a standardized load capacitance Zct is added to the impedance Zx of the crystal unit determined in claim 1 to obtain a normalized crystal unit with a load capacitance. How to measure a crystal unit. 3. When measuring a crystal resonator with a load capacitance by a network analyzer, the measurement signal is switched by a switch to change the impedance Zcf of only the load capacitance of the load capacitance portion.
3. The method for measuring a crystal unit with a load capacitance according to claim 1 or 2, wherein the measurement is performed by a measuring jig capable of measuring at any time.