JP2012225856A - Measurement target characteristics measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measurement target characteristic measuring apparatus having a surface acoustic wave sensor, with improved measurement sensitivity and accuracy while keeping appropriate oscillation.SOLUTION: A measurement target characteristic measuring apparatus comprises: a synthesizer 2 that outputs a first output signal S1 having a specified frequency based on a reference frequency from an oscillator 21; a surface acoustic wave sensor 3 that receives the first output signal S1 and outputs a second output signal S2 according to characteristics of a measurement target; a first phase comparator 4 that detects a phase difference between the first output signal S1 and the second output signal S2; a first loop filter 5 that controls the reference frequency of the synthesizer 2 based on the phase difference detected by the first phase comparator 4; and a frequency counter 6 that detects the frequency change of the first output signal S1 outputted from the synthesizer 2.

Description

  The present invention relates to an object characteristic measuring apparatus that includes a surface acoustic wave (SAW) sensor and measures characteristics such as viscosity and conductivity of a liquid.

  Conventionally, this type of DUT characteristic measuring device detects the phase difference between the reference wave (transmitted signal) from the oscillation circuit and the reflected wave (received signal) that has passed through or passed through the surface acoustic wave sensor. (See, for example, Patent Document 1). That is, as shown in FIG. 3, the transmission signal from the oscillation circuit 101 is transmitted to the surface acoustic wave sensor 103 and the phase comparator 104 via the distributor 102, and the transmission signal transmitted to the surface acoustic wave sensor 103 is transmitted. Is transmitted to the phase comparator 104 as a received signal by passing through the surface acoustic wave sensor 103. The phase comparator 104 compares the phases of the transmission signal and the reception signal, converts the phase difference into a voltage, and outputs the voltage.

  In addition, a method is known in which a solution is dropped directly on a resonator in an oscillator and a change in frequency is used as a measurement parameter. That is, as shown in FIG. 4, an oscillation circuit 112 is incorporated in the surface acoustic wave sensor 111, a solution is dropped directly into the oscillation circuit 112, and a frequency change before and after the dropping is measured by a frequency counter 113.

JP 2008-204234 A

  By the way, in the apparatus which detects a phase difference as mentioned above, since the resolution of a phase comparator (phase detector) is generally about 0.5 °, there is a problem that measurement sensitivity and accuracy are low. That is, when the 180 ° movement change is converted to 1.8 V and the voltage measurement resolution is about 5 mV, the measurement resolution of the phase comparator is as small as 2777 ppm, and there is a limit in measurement sensitivity and accuracy.

  Further, in the method in which the solution is directly dropped into the oscillator, when a highly viscous solution is dropped, the oscillation intensity may decrease and oscillation may stop. In addition, since the oscillation frequency fluctuates due to temperature change, it is necessary to separate the change of the solution itself and the temperature characteristic change. For this purpose, an oscillator for REF (for comparison and reference) must be provided.

  Furthermore, in order to increase measurement sensitivity and accuracy, a transversal surface acoustic wave sensor is used, in which a comb-shaped electrode for input and a comb-shaped electrode for output are arranged at a predetermined interval on a piezoelectric substrate. Although it is conceivable to lengthen the frequency, a plurality of frequencies satisfying the oscillation condition are generated, leading to abnormal oscillation.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an object characteristic measuring apparatus capable of improving measurement sensitivity and accuracy while ensuring proper oscillation.

  In order to achieve the above object, an invention according to claim 1 is directed to a synthesizer that outputs a first output signal having a predetermined frequency based on a reference frequency from an oscillator, and to receive the first output signal. A surface acoustic wave sensor that outputs a second output signal according to the characteristics of the measurement object, the first output signal, and the second output signal are received, and the first output signal and the second output are received. Phase comparison means for detecting a phase difference from a signal, control means for controlling a reference frequency of the synthesizer based on the phase difference detected by the phase comparison means, and the first output outputted from the synthesizer A device for measuring characteristics of an object to be measured, comprising: frequency change detection means for detecting a frequency change of a signal.

  According to the present invention, a first output signal having a predetermined frequency based on the reference frequency is output from the synthesizer, and in the surface acoustic wave sensor, the first output signal is a second output signal corresponding to the characteristics of the object to be measured. Is output as Next, the phase comparison means detects the phase difference between the first output signal and the second output signal, and the control means controls the reference frequency of the synthesizer based on this phase difference. As a result, the frequency of the first output signal output from the synthesizer changes, and this change is detected by the frequency change detecting means.

  According to a second aspect of the present invention, there is provided a burst conversion means for converting the first output signal transmitted to the surface acoustic wave sensor into a burst wave having a predetermined waveform in the device property measuring apparatus according to the first aspect. The control means measures only the main response signal component of the phase difference pulse detected by the phase comparison means, and holds the value of the main response signal component during a period when the main response signal component does not appear. Then, the reference frequency is controlled based on the main response signal component.

  According to the present invention, the first output signal is converted into a burst wave by the burst conversion means and transmitted to the surface acoustic wave sensor, and the second output signal output through the surface acoustic wave sensor is also converted into the burst wave ( Pulse signal) to the phase comparison means. Then, in the control means, only the main response signal component of the phase difference pulse from the phase comparison means is measured, and the value of the main response signal component is held during the period when the main response signal component does not appear, and the main response The reference frequency is controlled based on the signal component.

  According to the first aspect of the present invention, the first output signal output from the synthesizer based on the phase difference between the first output signal from the synthesizer and the second output signal that has passed through the surface acoustic wave sensor. This frequency is detected by the frequency change detecting means. That is, since the measurement result by the surface acoustic wave sensor is detected and output as a frequency change, the measurement resolution is high and the measurement sensitivity and accuracy can be increased. In addition, since the first output signal is oscillated and output from the synthesizer, proper oscillation can be ensured without causing oscillation stop or abnormal oscillation.

  According to the invention described in claim 2, even if the first output signal is converted into a burst wave in order to separate the direct wave (direct wave) and the desired wave (main response signal), in the control means, Control of the reference frequency based on the main response signal component is performed continuously and continuously. Therefore, it is possible to always output the first output signal having a predetermined frequency appropriately from the synthesizer.

1 is a configuration block diagram showing a device characteristic measuring apparatus according to Embodiment 1 of the present invention. It is a block diagram which shows the to-be-measured object characteristic measuring apparatus which concerns on Embodiment 2 of this invention. It is a block diagram showing a conventional device-to-be-measured device measuring apparatus having a surface acoustic wave sensor. It is a block diagram showing the configuration of another conventional device property measuring apparatus having a surface acoustic wave sensor.

  The present invention will be described below based on the illustrated embodiments.

(Embodiment 1)
FIG. 1 is a block diagram showing the configuration of an object characteristic measuring apparatus 1 according to this embodiment. This device property measuring apparatus 1 includes a surface acoustic wave sensor 3 and measures characteristics such as viscosity and conductivity of a liquid, and mainly includes a synthesizer 2, a surface acoustic wave sensor 3, and a first Phase comparator (phase comparison means) 4, first loop filter (control means) 5, and frequency counter (frequency change detection means) 6.

  The synthesizer 2 is a PLL (Phase Locked Loop) phase synthesizer that outputs a first output signal S1 having a predetermined frequency based on a reference frequency from a crystal oscillator (TCXO). Specifically, a reference frequency signal generated by the crystal oscillator 21 is input to a second phase comparator (PD) 22 and a signal generated by a voltage controlled oscillator (VCO: Voltage Controlled Oscillator) 23. Is frequency-divided and generated by the frequency divider 24 into an output frequency signal multiplied by a predetermined frequency, and input to the second phase comparator 22.

  Next, in the second phase comparator 22, the reference frequency signal from the crystal oscillator 21 and the output frequency signal from the frequency divider 24 are compared, and the phase of the output frequency signal advances from the phase of the reference frequency signal. If it is, the H signal (charging current discharge) is transmitted to the second loop filter 25. On the other hand, when the phase of the output frequency signal is delayed from the phase of the reference frequency signal, the L signal (discharge current suction) is transmitted to the second loop filter 25.

  Subsequently, the second loop filter 25 integrates the current from the second phase comparator 22 and converts it into a voltage signal, and performs a smoothing process to generate a control voltage. The voltage controlled oscillator 23 oscillates and outputs a frequency signal corresponding to the control voltage from the second loop filter 25, that is, the first output signal S1. At the same time, the frequency signal from the voltage controlled oscillator 23 is input to the frequency divider 24 as described above.

  In this way, the control voltage is increased or decreased so that the phase of the first output signal S1 from the voltage controlled oscillator 23 matches the phase of the reference frequency signal from the crystal oscillator 21, and the oscillation from the voltage controlled oscillator 23 is performed. Adjust the frequency. As a result, the first output signal S1 from the voltage controlled oscillator 23 matches (closes to) the phase of the reference frequency signal, and has a frequency that is a multiple of the frequency division of the reference frequency signal. In addition, the output side of the first loop filter 5 is connected to the control voltage input terminal of the crystal oscillator 21 and, as will be described later, according to the control voltage from the first loop filter 5, The frequency of the reference signal (reference frequency) is changed.

  The surface acoustic wave sensor 3 is a sensor that receives the first output signal S1 from the synthesizer 2 via the distributor 7 and outputs a second output signal S2 corresponding to the characteristics of the object to be measured. That is, when the first output signal S1 is input to the surface acoustic wave sensor 3, the phase varies according to the characteristics of the object to be measured and is output as the second output signal S2.

  The first phase comparator 4 receives the first output signal S1 and the second output signal S2, and detects and outputs the phase difference between the first output signal S1 and the second output signal S2. It also has a charge pump function. That is, the first output signal S1 and the second output signal S2 are compared, and if the phase of the second output signal S2 is ahead of the phase of the first output signal S1, the H signal is 1 is transmitted to the first loop filter 5 (a predetermined charging current is discharged to the first loop filter 5). On the other hand, when the phase of the second output signal S2 is delayed from the phase of the first output signal S1, the L signal is transmitted to the first loop filter 5 (from the first loop filter 5 to a predetermined value). Inhale the discharge current.)

  The first loop filter 5 controls the reference frequency of the synthesizer 2 based on the phase difference detected by the first phase comparator 4. That is, it is connected to the control voltage input terminal of the crystal oscillator 21 of the synthesizer 2, integrates the current from the first phase comparator 4 and converts it into a voltage signal, and performs a smoothing process to generate a control voltage. Then, by inputting this control voltage to the control voltage input terminal of the crystal oscillator 21, the frequency of the reference signal from the crystal oscillator 21 changes according to the control voltage.

  The frequency counter 6 is a counter that detects and counts the frequency change amount of the first output signal S1 output from the synthesizer 2. That is, as described above, the reference frequency from the crystal oscillator 21 is changed based on the control voltage from the first loop filter 5, and the frequency of the first output signal S1 output from the synthesizer 2 is changed accordingly. Since this changes, this amount of change is detected. The detected amount of change corresponds to the phase difference detected by the first phase comparator 4, that is, the measurement result by the surface acoustic wave sensor 3.

  Next, the operation of the measured object property measuring apparatus 1 having such a configuration will be described. Here, it is assumed that the surface acoustic wave sensor 3 is placed in the environment of the object to be measured or is in contact with the object to be measured so that the characteristics of the object to be measured can be measured.

  First, in the synthesizer 2, the first output signal S 1 having a predetermined frequency based on the reference frequency that matches the phase of the reference frequency signal from the crystal oscillator 21 is obtained from the synthesizer 2 by the phase-locked loop processing as described above. Generated and output. The first output signal S1 is input to the surface acoustic wave sensor 3 and the first phase comparator 4 via the distributor 7, and is also input to the frequency counter 6 (the signal S1 at this time is changed). (Referred to as “signal S1-1”).

  Next, the phase of the first output signal S1 input to the surface acoustic wave sensor 3 varies according to the characteristics of the object to be measured, and is output from the surface acoustic wave sensor 3 as the second output signal S2. 1 to the phase comparator 4. Subsequently, the first phase comparator 4 detects the phase difference between the first output signal S1 and the second output signal S2, and based on the phase difference, the H signal and the L signal as described above are detected. Input to the first loop filter 5.

  Then, in the first loop filter 5, the control voltage based on the phase difference is generated as described above, and is input to the control voltage input terminal of the crystal oscillator 21. As a result, the reference frequency from the crystal oscillator 21 changes according to the control voltage, and the frequency of the first output signal S1 output from the synthesizer 2 changes accordingly (the signal S1 at this time is changed to “signal S1− 2 ”).

  The first output signal S1-2 is input to the surface acoustic wave sensor 3 and the first phase comparator 4 and input to the frequency counter 6 in the same manner as described above. 1 frequency change of the output signal S1, that is, the frequency change amount from the signal S1-1 to the signal S1-2 is detected and counted. Then, by repeating such loop processing, the first output signal S1 converges to a predetermined frequency (the signal S1 at this time is referred to as “signal S1-3”). As a result, the final frequency change of the first output signal S1, that is, the frequency change from the signal S1-1 to the signal S1-3 is detected by the frequency counter 6, and the measurement result by the surface acoustic wave sensor 3 is the frequency change. It is obtained as a change.

  As described above, according to the measured object property measuring apparatus 1, since the measurement result by the surface acoustic wave sensor 3 is detected and output as a frequency change, the measurement resolution is high and the measurement sensitivity and accuracy can be improved. it can. That is, when a 180 ° phase change is converted to a 0.4 MHz frequency change and the frequency measurement resolution is 1 Hz, the measurement resolution is as large as 2.5 ppm, which is converted to voltage (measurement resolution is 2777 ppm). Compared to the above, it is possible to obtain a measurement sensitivity and accuracy of 1000 times or more.

  In addition, since the first output signal S1 is oscillated and outputted from the synthesizer 2, it is possible to ensure proper oscillation without causing oscillation stop or abnormal oscillation. That is, measurement sensitivity and accuracy can be improved while ensuring proper oscillation.

(Embodiment 2)
FIG. 2 is a configuration block diagram showing the device characteristic measuring apparatus 10 according to this embodiment. In this embodiment, the configuration is different from that of the first embodiment in that the direct wave and the desired wave of the output signal are separated, and the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be given. Is omitted.

  In this embodiment, a burst circuit (burst conversion means) 81, a timing generation circuit (burst conversion means) 82, and a sample hold circuit (control means) 83 are provided.

  The burst circuit 81 and the timing generation circuit 82 are circuits that convert the first output signal S1 transmitted to the surface acoustic wave sensor 3 into a burst wave having a predetermined waveform. That is, the burst circuit 81 is a pulse generation circuit disposed between the distributor 7 and the surface acoustic wave sensor 3, and the timing generation circuit 82 is a circuit that oscillates a predetermined periodic signal. Then, the burst circuit 81 converts the first output signal S1 from the synthesizer 2 (distributor 7) into a burst wave (pulse signal) based on the timing (periodic signal) from the timing generation circuit 82, and generates it. Thus, the signal is input to the surface acoustic wave sensor 3.

  The sample hold circuit 83 measures only the main response signal component of the phase difference pulse detected by the first phase comparator 4 and holds the value of the main response signal component during a period when the main response signal component does not appear. Thus, the reference frequency is controlled based on the main response signal component. Specifically, a first operational amplifier that receives an input signal to be sampled, a switch that passes an output signal of the first operational amplifier based on timing (periodic signal) from the timing generation circuit 82, and a first operational amplifier And a second operational amplifier that outputs a voltage based on the charge accumulated in the capacitor as a hold signal.

  The switch outputs the output signal of the first operational amplifier to the second operational amplifier when the periodic signal from the timing generation circuit 82 is at a high level, and also charges the capacitor according to the output signal of the first operational amplifier. To accumulate. In addition, when the periodic signal from the timing generation circuit 82 is at a low level, the switch does not output the output signal of the first operational amplifier to the second operational amplifier, and the voltage generated by the electric charge accumulated in the capacitor is output to the second operational amplifier. Output from.

  As described above, the sample hold circuit 83 outputs the output signal from the first phase comparator 4 when the periodic signal from the timing generation circuit 82 is at a high level (desired wave), and also according to the output signal. Charge is stored in the capacitor. On the other hand, when the periodic signal from the timing generation circuit 82 is at a low level (direct wave), a voltage based on the charge accumulated in the capacitor is output.

  According to the DUT characteristic measuring apparatus 10 having such a configuration, first, a first output signal S1 having a predetermined frequency based on the reference frequency is generated and output from the synthesizer 2, as in the first embodiment. The first output signal S1 is input to the first phase comparator 4 and the frequency counter 6 as it is, converted into a burst wave via the burst circuit 81, and input to the surface acoustic wave sensor 3. .

  Next, the second output signal S <b> 2 from the surface acoustic wave sensor 3 is input to the first phase comparator 4, and in the first phase comparator 4, the first output signal S <b> 1 and the second output signal S <b> 2. And the detection result is input to the sample hold circuit 83 as a pulse signal (phase difference pulse).

  Then, a control voltage based on the output signal from the first phase comparator 4 and the voltage due to the electric charge accumulated in the capacitor is input from the sample hold circuit 83 to the crystal oscillator 21 as described above. . As a result, the reference frequency from the crystal oscillator 21 and the frequency of the first output signal S1 output from the synthesizer 2 change, and the frequency change amount is detected by the frequency counter 6 as in the first embodiment.・ It is counted.

  As described above, according to this embodiment, in order to separate the direct wave (direct wave) and the desired wave (main response signal), even if the first output signal S1 is converted into a burst wave, A control voltage is continuously and continuously input from the hold circuit 83 to the crystal oscillator 21 to control the reference frequency. Therefore, the first output signal S1 having a predetermined frequency can be output from the synthesizer 2 always (continuously) properly.

  Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above embodiment, and even if there is a design change or the like without departing from the gist of the present invention, Included in the invention. For example, in the above embodiment, the H signal and the L signal are transmitted from the first phase comparator 4 to the first loop filter 5, but the detection signal is directly sent to the first loop filter 5. May be.

DESCRIPTION OF SYMBOLS 1,10 Device property measuring apparatus 2 Synthesizer 21 Crystal oscillator (oscillator)
22 second phase comparator 23 voltage controlled oscillator 24 frequency divider 25 second loop filter 3 surface acoustic wave sensor 4 first phase comparator (phase comparison means)
5 First loop filter (control means)
6 Frequency counter (frequency change detection means)
81 Burst circuit (burst conversion means)
82 Timing generation circuit (burst conversion means)
83 Sample hold circuit (control means)
S1 first output signal S2 second output signal

Claims (2)

A synthesizer that outputs a first output signal of a predetermined frequency based on a reference frequency from an oscillator;
A surface acoustic wave sensor that receives the first output signal and outputs a second output signal according to the characteristics of the device under test;
Phase comparison means for receiving the first output signal and the second output signal and detecting a phase difference between the first output signal and the second output signal;
Control means for controlling a reference frequency of the synthesizer based on the phase difference detected by the phase comparison means;
A frequency change detecting means for detecting a frequency change of the first output signal output from the synthesizer;
A device characteristic measuring apparatus comprising: Burst conversion means for converting the first output signal transmitted to the surface acoustic wave sensor into a burst wave of a predetermined waveform;
The control means measures only the main response signal component of the phase difference pulse detected by the phase comparison means, holds the value of the main response signal component during a period when the main response signal component does not appear, Controlling the reference frequency based on a main response signal component;
The device property measuring apparatus according to claim 1, wherein: