JPH0452414B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a resonator characteristic measurement and selection device that measures the resonant frequency and no-load Q characteristics of a resonator used in the VHF to UHF band using a simple method. be.

(Example of conventional configuration and its problems) Since the characteristics of resonators below the VHF band are lumped constant circuits, the resonant frequency no-load Q is almost always measured using a Q meter. However, as the frequency becomes higher, the Q-meter method cannot be applied because it has stray inductance and capacitance and must be treated as a distributed constant circuit. Therefore, conventionally, VHF
For measuring resonators with high Q above the frequency band, there is a method of actually measuring the resonance characteristics (curve) using a network tenalizer or a sweep oscillator and a high-precision detector, and then calculating the resonant frequency and no-load Q from that data. It was clear.

Although this method is the best method for obtaining accurate data, it has drawbacks such as expensive measuring equipment, time-consuming measurement, and inability to directly obtain correlation between no-load Q and measured values. However, there remained a cost problem in quickly measuring a large number of resonators.

Purpose of the invention The purpose of the present invention is to create a circuit as simple and inexpensive as possible.
It is an object of the present invention to provide a resonator characteristic measurement and selection device that quickly and accurately measures resonator characteristics in the VHF to UHF band.

Structure of the Invention The present invention achieves the above object and includes a positive feedback oscillator including at least a narrowband bandpass filter configured to be able to incorporate a resonator under test, a fixed phase shifter, and an amplifier. The present invention provides a resonator characteristic measuring and selecting device characterized in that the oscillation frequency of a positive feedback oscillator is measured by a frequency counter and the output level is measured by a wattmeter to measure the resonator characteristics of a resonator to be measured.

DESCRIPTION OF EMBODIMENTS The basic configuration of an embodiment of the present invention is shown in FIG. In FIG. 1, 101 is an amplifier, 102 is a one-stage narrowband bandpass filter constructed using a resonator under test, and 103 is a phase shifter. This entire loop forms a positive feedback oscillator. There is. Normally, a positive feedback oscillator is configured so that the output of the amplifier is fed back to the input so that the phase difference satisfies the condition of 360° × n (n = 0, ±1, ±2, ...). Since there are many oscillation points, the oscillation frequency is designed to uniquely determine the oscillation frequency by imparting frequency characteristics to the amplitude characteristics using a band-pass filter or the like. The present invention attempts to measure the resonator characteristics by utilizing the relationship between the bandpass filter used in this oscillator, the oscillation frequency, and the oscillation output level. FIG. 2 shows the structure and characteristics of a one-stage bandpass filter used in this embodiment. 201, 202 in a
are input and output terminals of the filter, 204 and 205 are coupling capacitors, and 203 is a resonator to be measured, which is a quarter wavelength coaxial type resonator in this example. This resonator 203 is configured to be easily connected and fixed to a circuit by crimping or the like in order to quickly measure a large number of resonators. Now, if we reduce the coupling capacitance of the filter to realize a narrow band filter, the amplitude and phase characteristics of the filter can be made to have large changes near the resonant frequency fr of the resonator 203, as shown in Figure 2b. Become. Since the frequency characteristics of the phase shifter 103 shown in FIG. 1 can usually be designed to be small, the resonance frequency fr and the oscillation frequency fo when configured as an oscillator almost match. This relationship is shown in Figure 3a. In addition, since the filter 102 has a narrow band as described above and has a large insertion loss, if it is configured as a positive feedback oscillator, the circuit can be designed in a region where the output of the amplifier is not saturated. Further, the insertion loss of the filter is inversely proportional to the no-load Q of the resonator 203 used when the coupling is the same, that is, the insertion loss is small when Q is large. Therefore, if a positive feedback oscillator is constructed using this filter, the oscillation output level and the no-load Q of the resonator can be in a relationship close to direct proportion as shown in FIG. 3b.

Since the oscillation frequency and output level of the oscillator can be easily measured, it is possible to measure the resonant frequency and no-load Q of the resonator by measuring the oscillator characteristics. This method is particularly useful in the process of selecting a large number of resonators in a short time.

FIG. 4 shows a specific configuration of an embodiment of the present invention.
This example is a device that uses a frequency counter and a power meter to select resonators at high speed. In the figure,
401 is a high frequency amplification stage, 402 is a narrow band pass filter incorporating the resonator 408 to be measured as a resonant element, 403 is a power divider (hybrid circuit), and 404 is a fixed phase shifter. High frequency amplification period 401-narrow band pass filter 402
A positive feedback oscillator is configured by the loop of - power divider 403 - fixed phase shifter 404. A part of the oscillation output passes through a power divider 403 and then another power divider 405, and its frequency is determined by a frequency counter 40.
At step 6, the output level is simultaneously monitored by a power meter 407, and the resonant frequency of the resonator and the no-load Q are measured. Resonators can be selected by adding means for determining that a resonator is a good product if the frequency and output level are within a certain range.

By the way, in the example of FIG. 4, the measurable frequency range is narrow, so if a wide band is to be achieved, the oscillation frequency band of the positive feedback oscillator must be widened.
This can be addressed by providing the phase shifter 404 with a function of switching the phase amount.

Further, in this example, a coaxial resonator is used as the resonator, but it goes without saying that this method can be applied to any structure of the resonator. Further, by employing means for fixing the resonator to the filter 402 by crimping or the like, rapid measurement becomes possible.

Effects of the Invention As described above, the present invention provides a narrowband bandpass filter configured to be able to incorporate a resonator to be measured;
A positive feedback oscillator including at least a fixed phase shifter and an amplifier is provided, and the oscillation frequency of the positive feedback oscillator is measured by a frequency counter and the output level is measured by a wattmeter to measure the resonator characteristics of the resonator to be measured. The present invention provides a resonator characteristic measurement and selection device that is characterized by It can be applied to high-speed sorting of containers, and its industrial value is extremely large.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a positive feedback oscillator which is the basic configuration of an embodiment of the present invention, Figure 2a is a configuration diagram of a narrowband filter used in the positive feedback oscillator, and Figure 2b is
3A and 3B are characteristic diagrams showing the correlation between the oscillator characteristics and the resonator characteristics, and FIG. 4 is a block diagram showing the specific configuration of an embodiment of the present invention. 401...Amplifier, 402...Narrowband bandpass filter, 403, 405...Power distribution, 40
4... Fixed phase shifter, 406... Frequency counter,
407...Power meter, 408...Resonator to be measured.

Claims (1)

[Claims] 1. A positive feedback oscillator including at least a narrowband bandpass filter configured to be able to incorporate a resonator under test, a fixed phase shifter, and an amplifier; A resonator characteristic measurement and selection device characterized in that the output level is measured with a wattmeter and the resonator characteristics of the resonator to be measured are measured.