JP3068508U - Measuring jig for crystal resonator with load capacity - Google Patents

Abstract

(57) [Summary] PROBLEM TO BE SOLVED: To provide a measurement jig for a crystal resonator with a load capacitance, which accurately measures various characteristics such as impedance of the crystal resonator with a load capacitance by a network analyzer. SOLUTION: A measurement signal is inputted from an OUT terminal of a network analyzer, and either one of an input terminal of a DUT or a point O which is a connection point between a crystal unit of the DUT and a load capacitance is selected and connected. A switch and a second switch for selecting either a measurement signal from the network analyzer or a measurement signal at point O which is a connection point between the crystal unit of the DUT and the load capacitance, and outputting the selected signal to the Rch terminal of the network analyzer; An output terminal for outputting an output signal from an output terminal of the DUT to a measurement terminal of the network analyzer.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 This invention relates to a measuring jig that can measure various impedances and the like of a crystal unit with a load capacitance (hereinafter referred to as “DUT”) with high accuracy using a network analyzer.

[0002]

[Prior art]

 2. Description of the Related Art Conventionally, impedance measurement of a quartz oscillator or the like is generally performed using an existing network analyzer. A network analyzer is a measuring instrument that analyzes the transmission and reflection characteristics of a linear network using sine waves. The main configuration is, for example, an OUT terminal that oscillates and outputs a sweep frequency or a predetermined constant frequency with a synthesizer, and an input terminal for a plurality of high-frequency signals. The signals are converted from analog to digital, and the resulting digital signals are processed as required by an MPU (Micro Processor Unit), and the resulting frequency and impedance characteristics are displayed on a display or printed out. Or

A plurality of input terminals of the network analyzer include, for example, R (Reference) ch (channel), Ach and Bch. Rch is an input terminal serving as a reference signal of a measurement signal in DUT (device under test) measurement, and Ach and Bch are terminals for inputting a signal output from the DUT. In the network analyzer, various analyzes are performed by calculating data of an input signal from Ach or data of an input signal from Bch based on data of a signal input to Rch. In this specification, description will be made with Ach.

[0004] In the test of the crystal resonator, the test is generally performed using the above-mentioned general-purpose network analyzer, but the present invention is not limited to this. There is also a dedicated measuring instrument that eliminates 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.

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, etc., and is generally called a parallel capacitance. L1 and C1 are equivalent constants of the quartz oscillator as an electromechanical oscillation 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 antiresonance frequency is represented by fa = fo (1+ (C1 / 2Co)). Therefore, if a characteristic test of a single crystal unit is performed using a network analyzer, measurement 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 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 in a specification document or in actual use by both manufacturers and users is desired. As a solution, there is an idea that a crystal resonator 41 and a load capacitor 42 connected in series are regarded as one component.

[0007] In theory, even if a load capacitance 42 is connected in series to the crystal unit 41, an electrical equivalent circuit can be displayed in the same manner as in FIG. However, as shown in FIG. 5B, the equivalent constant differs. That is, the equivalent constant of the equivalent circuit including the load capacitance 42 is converted into the equivalent constant of FIG. 5B by calculation, and Co is C'o, L1 is L'1, and C1 is C'1. In addition, R has been 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, C L is the capacitance value of the load capacitance 42.

FIG. 6 shows a conventional measurement configuration diagram of a DUT 40 in which a load capacitance 42 is connected in series to a crystal unit 41. First, the network analyzer (NA) 50 will be described. The front surface of the network analyzer 50 includes, for example, a switch group 51 for setting measurement parameters, a display unit 52, and input / output terminals such as an OUT terminal 54, an Rch terminal 56, and an Ach terminal 58.

Main components of the internal configuration of the network analyzer 50 are the same as those described above, but include a measurement signal oscillator, a plurality of so-called digital voltmeters for inputting received signals, and calculation of measured values of the digital voltmeters. And a control unit for controlling the whole. Therefore, the OUT terminal 54 of the network analyzer 50 shown in FIG. 6 is connected to an analog signal source 55 such as a synthesizer and outputs a measurement signal. The input terminals Rch terminal 56 and Ach terminal 58 are connected to a so-called digital voltmeter 57 or digital voltmeter 59 for obtaining an amplitude level and a phase by a digital value by an analog / digital converter.

As shown in FIG. 6, a conventional means for measuring a DUT 40 outputs a measurement signal from an OUT terminal 54 of a network analyzer 50, and outputs a measurement signal from an input terminal 43 of a DUT case 39 on which the DUT 40 is mounted and a network terminal. This signal is supplied to the Rch terminal 56 of the analyzer 50. The output signal of the DUT 40 is provided from the output terminal 44 of the DUT case 39 to the Ach terminal 58 of the network analyzer 50.

The Rch terminal 56 and the Ach terminal 58 of the network analyzer 50 receive the input measurement signals, respectively, and measure the voltage value and phase value of each amplitude level. The arithmetic unit obtains the amplitude level difference and the phase difference based on this data, and obtains the impedance of the DUT 40, the resonance frequency fo, the anti-resonance frequency fa, and the like.

[0012]

[Problems to be solved by the invention]

 In conventional measuring means, the load capacity used for measurement is measured in advance to determine the capacity value. The measurement was performed based on that value, but the load capacity value changed with temperature or with time, and accurate measurement could not be performed due to the influence.

As described above, the conventional DUT measuring means applies the measurement signal from the network analyzer 50 to the Rch terminal and the crystal oscillator 41 side of the DUT 40, and applies the output signal from the load capacitance 42 side to the Ach terminal. Thus, it is a means for processing and measuring the signal of the Rch terminal and the signal data of the Ach terminal.

An object of the present invention is to perform a characteristic test of a crystal resonator with a load capacitance so that an impedance value of only a load capacitance and an impedance value of a crystal resonator with a load capacitance can be individually measured. Provide a measuring instrument for a crystal unit with a load capacitance that can measure the data at that point even if an error occurs due to a change in the load capacitance value due to temperature, etc., without the need to separately measure the load capacitance as described above. Things.

[0015]

[Means for Solving the Problems]

 In order to achieve the above object, the present invention provides a DUT case of the conventional DUT measuring means, and sets a connection point between the crystal unit 41 and the load capacitor 42 as an O point, and switches the first switch. A measurement signal from the network analyzer 50 can be applied to the point O, and a measurement signal at the point O can be measured by the network analyzer 50 by switching the second switch. A measurement jig was used.

Thus, accurate measurement data can be obtained for both the DUT 40 and the load capacitance 42. In the measurement, either the measurement of the DUT 40 or the measurement of the load capacitance 42 may be performed first. Here, the measurement of the load capacitance 42 will be described first.

In order to measure the load capacitance 42, a measurement signal from the OUT terminal 54 of the network analyzer 50 is applied to a point O of a connection point between the crystal unit 41 and the load capacitance 42 by switching a first switch. . The measurement signal at the point O is supplied to the Rch terminal, which is the reference signal input terminal of the network analyzer 50, by switching the second switch. On the other hand, the output signal of the load capacitor 42 is supplied to the Ach terminal, which is the measurement signal input terminal of the network analyzer 50. In a network analyzer having a BCH terminal, a Bch terminal may be used, but here, the Ach terminal is used as a general description. The network analyzer 50 calculates the data of these two signals to obtain the correct load capacitance value.

Next, characteristics of the DUT 40 are measured. The measurement signal from the OUT terminal 54 of the network analyzer 50 is supplied to the input terminal side of the DUT 40, that is, the crystal oscillator 41 by switching the first switch. The second switch is also switched to apply the measurement signal from the OUT terminal 54 of the network analyzer 50 to the Rch terminal. The output signal of the DUT 40 is provided to the Ach terminal. The network analyzer 50 calculates the data of the DUT 40 by calculating the data of both signals.

By the means described above, the correct impedance value of the load capacitor 42 and the correct impedance value of the DUT 40 can be obtained. Next, the configuration of the present invention will be described.

The first device is a basic device. In other words, this is a measurement jig that measures the characteristics of a crystal resonator with a load capacitor, which is a DUT, using a network analyzer. The measurement signal is input from the OUT terminal of the network analyzer, and the input terminal of the DUT or The first switch that selects and connects one of the O points that is the connection point between the DUT crystal unit and the load capacitance, and the connection between the measurement signal from the network analyzer or the DUT crystal unit and the load capacitance A second switch that selects one of the measurement signals at point O and outputs it to the Rch terminal of the network analyzer, and an output terminal that outputs the output signal from the output terminal of the DUT to the measurement terminal of the network analyzer This is a measuring jig for a crystal resonator with a load capacitance, comprising:

The second invention is to add an electronic circuit so as to be more appropriate when extracting a measurement signal applied to a point O which is a connection point between the crystal unit of the DUT and the load capacitance and a measurement signal at the point O. It was done. That is, in the jig of the first invention, a circuit in which a capacitor and a resistor are connected in series between the first switch and the O point of the DUT is inserted between the first switch and the O point of the DUT. This is a measurement jig with a buffer amplifier inserted between it and the switch.

The third invention specifies that a bias circuit for a variable capacitor diode is added when the load capacitance is a variable capacitor diode. In other words, when the load capacitance is a variable capacitor diode in the measurement jig of the crystal resonator with load capacitance according to the first invention or the second invention, when the load capacitance is a variable capacitor diode, the bias terminal for applying a bias voltage and the variable capacitor diode are connected to the variable capacitor diode. This is a measurement jig provided with a bias circuit that varies a load capacitance value by applying a predetermined bias voltage.

[0023]

[Embodiment of the invention]

 An embodiment of the invention will be described based on an example with reference to the drawings. FIG. 1 is a block diagram of one embodiment of the present invention, FIG. 2 is a block diagram of another embodiment, and FIG. 3 is a block diagram of another embodiment. First, FIG. 1 will be described.

The upper half of FIG. 1 is a network analyzer 50, and the lower half is a measurement jig 10 of a crystal unit with a load capacitance. The input and output terminals of the measurement jig 10 of the crystal unit with the load capacitance are given the same names as the input and output terminals of the network analyzer 50 so as not to make a wrong connection. That is, 11 is an input terminal of the OUT signal, 12 is an output terminal of Rch, and 13 is an output terminal of Ach.

The measurement signal input to the input terminal 11 of the OUT signal is branched and supplied to the first switch 15 and the second switch 16. The first switch 15 is a switching relay for selecting and connecting a measurement signal input from the network analyzer 50 to an input terminal of the DUT 40 or an O point which is a connection point between the crystal unit 41 of the DUT 40 and the load capacitance 42. It is. The second switch 16 selects either the measurement signal from the network analyzer 50 or the measurement signal at the point O, which is the connection point between the crystal unit 41 of the DUT 40 and the load capacitance 42, and selects the Rch terminal 56 of the network analyzer 50. This is a switching relay that outputs to. An output signal from the output terminal of the DUT 40 is output to an Ach terminal, which is a measurement terminal of the network analyzer 50.

The circuit from the first switch 15 to the point O is inserted in a series circuit of a capacitor 18 and a resistor 19. The capacitor 18 is a DC blocking capacitor and has a value of about μF. The resistor 19 adjusts the potential at the point O and has a value of about 10 KΩ. If the load capacitance 42 is a normal capacitor, the capacitor 18 and the resistor 19 need not be provided. A buffer amplifier 17 is inserted between the point O and the second switch. This is for extracting the signal level at the point O without deteriorating the signal level. However, this is not necessary if the load capacitance 42 is a normal capacitor.

[0027] Figure 2 is a load capacitance, in which had use one of the variable capacitor diode 42 _2. It is required and the bias voltage terminal 20 and a bias circuit for applying a reverse voltage to the variable capacitor diode 42 ₂ in this case. The bias circuit includes, for example, a resistor 21, a resistor 19, and a resistor 22. In this case, a DC blocking capacitor 18 is required.

[0028] Figure 3 is a load capacitance, in which had use two variable capacitor diode 42 _3. Bias voltage terminal 20 and a bias circuit for applying a reverse voltage to the variable capacitor diode 42 ₃ in this case is necessary. The bias circuit includes, for example, a resistor 21, a resistor 22, and a resistor 23. Also in this case, the DC blocking capacitor 18 is required.

Next, measurement of the load capacity 42 will be described with reference to FIG. The first switch 15 is connected to the point O, which is the connection point between the crystal unit 41 and the load capacitor 42, and the second switch is also connected to the point O. Therefore, the OUT signal of the network analyzer 50 is applied to the load capacitance 42 via the first switch 15, and the signal at the point O is supplied to the R ch of the network analyzer 50 via the buffer amplifier 17 and the second switch 16. Data is obtained as a signal of a reference level and phase that is input.

On the other hand, the output signal that has passed through the load capacitance 42 is input to Ach of the network analyzer 50, and data is obtained as a measurement signal. Then, the load capacitance value is obtained from the data of the level and phase of both. When this is expressed by a four-terminal network equation, Equations 1 and 2 are obtained.

[0031]

(Equation 1)

[0032]

(Equation 2)

Equation 1 is an equation of cascade connection of a four-terminal network when the voltage at point O is V, the current is I, the voltage at Ach terminal 58 is Va, and the current is Ia. Here, Zc is the impedance of the load capacitance 42, and A1, B1, C1, and D1 are four-terminal constants of the transmission path from the load capacitance 42 to the Ach terminal 58.

Equation 2 is a four-terminal network equation where the voltage at point O is V, the current is I, the voltage at the Rch terminal 56 is Vr, and the current is Ir. Here, A2, B2, C2, and D2 are four-terminal constants of the transmission line from the point O to the Rch terminal 56. Since V and I in Equations 1 and 2 are equal, the equation becomes Equation 3.

[0035]

(Equation 3)

Assuming that the input impedance of the network analyzer 50 is infinite, Ir and Ia are infinitely small 0 in the mathematical expression of Expression 3, and are represented by Expression 4. Equation 5 is obtained from Equation 4 and the impedance Zc of the load capacitance 42 becomes Equation 6.

[0037]

(Equation 4)

[0038]

(Equation 5)

[0039]

(Equation 6)

By calculating the unknown variables A2 / C1 and A1 / C1 of Equation 6 using the reference impedance, the impedance Zc of the load capacitance 42 can be calculated.

Next, measurement of the DUT 40 of the crystal unit with the load capacitance will be described. The first switch 15 is connected to the crystal unit 41 side of the DUT 40, and the second switch is connected to the OUT terminal side. Accurate measurement can be made by the “Measurement method of crystal resonator with load capacitance” filed on the same day.

The block diagram shown in Figures 2 and 3, as the load capacitance 42, a case of using the variable capacitor diode 42 ₂ or variable capacitor diode 42 _3. With such a configuration of the measuring jig, the load capacitance value of the variable capacitor diode can be independently measured as described above. By measuring the load capacitance value while continuously changing the bias voltage, the characteristics of the crystal oscillator 41 at an arbitrary load capacitance value can be measured, so that a great advantage is obtained.

[0043]

[Effect of the invention]

 As described above in detail, according to the present invention, it is possible to perform both the measurement of the crystal unit with the load capacitance and the measurement of only the load capacitance 42. Therefore, accurate measurement can be performed even when the load capacitance value is unknown, and a great advantage is obtained. Since the load capacity 42 can be measured at any time, even if the load capacity value changes due to a temperature change or a time change, the load capacity can be accurately measured in an actual state.

Further, when a variable capacitor diode is used as the load capacitance, it is possible to control the bias voltage and set the load capacitance value to an arbitrary capacitance value for measurement. Therefore, the technical effect of the present invention is large in practical use.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment in which a DUT is measured by a network analyzer using the measurement jig of the crystal resonator with a load capacitance according to the present invention.

FIG. 2 is another embodiment of the measuring jig of the quartz resonator with a load capacitance according to the present invention.

FIG. 3 is another embodiment of the measuring jig of the quartz resonator with a load capacitance according to the present invention.

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 capacitance measured in the present invention and an electrical equivalent circuit diagram thereof.

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

[Explanation of symbols]

Reference Signs List 10 Jig for measuring crystal unit with load capacitance 11 OUT signal input terminal 15 First switch 16 Second switch 17 Buffer amplifier 18 Capacitor 19 Resistance 20 Bias (Bias) voltage input terminal 21, 22, 23 Resistance 39 DUT case 40, 40 ₂ , 40 ₃ DUT (Device Under Test) 41 Crystal Resonator 42 Load Capacitance 42 ₂ , 42 ₃ Variable Capacitor Diode 50 Network Analyzer (NA) 51 Switch Group for Setting Measurement Parameters 52 Display Unit 54 OUT Terminal (Output) 55) Analog signal source 56 Rch terminal 57 Digital voltmeter 58 Ach terminal 59 Digital voltmeter

Claims (3)

[Utility model registration claims] 1. A measurement jig for measuring various characteristics of a crystal resonator with a load capacitance as a DUT by a network analyzer, wherein a measurement signal from an OUT terminal of the network analyzer is input to the input terminal of the DUT or the DUT. The first switch, which selects and connects one of the points O, which is the connection point between the crystal unit and the load capacitance, and the measurement signal from the OUT terminal of the network analyzer, or the connection between the crystal unit of the DUT and the load capacitance A second switch that selects one of the signals at the point O, which is a connection point, and outputs it to the Rch terminal of the network analyzer, and outputs an output signal from the output terminal on the load capacity side of the DUT to the Ach measurement terminal of the network analyzer A measurement jig for a crystal unit with a load capacitance, comprising: 2. A circuit in which a capacitor and a resistor are connected in series is inserted into a connection line between a first switch and a point O of a DUT,
2. The measuring jig for a crystal unit with a load capacitor according to claim 1, wherein a buffer amplifier is inserted into a connection line between the point O of the DUT and the second switch. 3. When the load capacitance is a variable capacitor diode, a bias terminal for applying a bias voltage and a bias circuit for applying a predetermined bias voltage to the variable capacitor diode to vary the load capacitance value are provided. 3. The measuring jig for a crystal unit with a load capacitor according to claim 1, wherein