JPS59183379A - Method and apparatus for measuring spectral purity - Google Patents

Abstract

PURPOSE:To enable purity measurement at a high speed with high accuracy, by adjusting the frequency and level of a reference signal from FM linear detection output due to both of oscillator output and the reference signal while ascertaining the normality of an oscillator output measuring system by said reference signal. CONSTITUTION:The outputs of an oscillator 7' and a reference signal generator 2 are applied to level meters 6, 7 through FM linear detectors 4, 5 of which the local frequencies are controlled by the control part 8 of respective measuring systems. In this case, the generator 2 is controlled through the control part 8 so as to make the outputs of the meters 6, 7 same and the frequency and level of a reference signal become equal to oscillation signal frequency and the level thereof. Subsequently, when the measuring systems are changed over through a switch 3, the normality of the detector 4 is ascertained by the reference signal and, at the same time, the oscillation output spectral purity is measured by the meter 7. By this mechanism, the measurement of the spectral purities of the outputs of a large amount of oscillators is easily and certainly performed at a high speed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for measuring the spectral purity of high frequency oscillators, such as voltage controlled oscillators.

2. Description of the Related Art Conventionally, an FM linear detection method has been known as a method for measuring the spectral purity of high-frequency oscillators used in radio equipment and the like. This FMji line detection method uses an FM linear detector and a level meter, and although the measurement sensitivity is inferior to other measurement methods, such as the FD method, it is possible to measure unsynchronized free-running oscillators. It was widely known as a method for measuring spectral purity because it was relatively easy to construct.

However, measurements such as setting the input level to the mixer of the FMik line detector and tuning the frequency required a skilled measuring person, and its application was limited to the laboratory level.

However, in recent years, advances in wireless equipment have led to the emergence of wireless equipment with frequencies of several hundred channels per unit, and there is an increasing need to ensure the spectral purity of conventional wireless equipment. In particular, it has become essential to measure the voltage-controlled oscillator, which largely determines the spectral purity performance, on a manufacturing calibration line in large quantities to ensure its spectral purity. In order to ensure measurement accuracy, this method required highly skilled measurers and a lot of time, so there was a need for a method and device that could measure a large number of oscillators in a shorter time without compromising measurement accuracy. .

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned FM linear detection method, to make it possible to measure a large number of generators with high accuracy in a short time, and to be suitable for automatic measurement that can be easily introduced into a manufacturing stacking line. An object of the present invention is to provide a method and apparatus for measuring spectral purity.

According to the present invention, an FM demodulation cover is obtained by tuning to the measurement frequency of the excavator under test, and an FM demodulation output is obtained by tuning the same measurement frequency as the oscillator to the standard signal, so that each demodulation output is equal. Control the t adjustment of the standard signal as follows, and check the linearity of the FM demodulation output using the standard signal,
Furthermore, a method for measuring spectral purity is obtained, which is characterized in that the connection between the oscillator and the standard signal is switched, and the spectral purity is calculated from the demodulated output of the oscillator. According to the present invention, the oscillator under test is connected to the input of the first 14
A linear detector and a demodulator of the FM linear detector; a first level meter and a standard signal generator connected to the input; a second FM linear detector and a demodulated output of the second FM linear detector; The second level meter that has been installed, a control unit that obtains an instruction output from each level meter, and a switching unit that switches the connection of the oscillator and standard signal generator to the respective FM linear detectors. A two-spectral purity measuring device is obtained.

The figure is a configuration diagram showing an embodiment of the present invention.

An oscillator which is a device under test is connected to an input of an FM linear detector 4 by a switching section 3. F by the control unit 8
The local frequency of the M linear detector 4 is controlled and tuned to the frequency of the oscillator 1. The demodulated output' obtained from the 12M linear detector 4 is measured by a level meter 6, and the measurement result is input to the control section 8. The control unit 8 can convert the obtained measurement results to obtain the spectral purity of the oscillator 1.

In the present invention, a standard signal generator 2 is further added to the measurement system described above.
It is connected to the input of the M linear detector 5 by a switch 3. FM
The linear detector 5 is set by the controller 8 to the same local frequency as the FM linear detector. Similarly, the output of the rear leg of the FM @ line detector is measured by the level meter 7, and the measurement result is input to the control section 8.

Here, the output level and frequency of the standard signal generator 2 are set by the control unit 8 so that the measured values of the level meter 6 and the level meter 7 are equal. Here, this standard signal generator 2 has a level Δ oscillation d frequency equivalent to that of the oscillator 1. Here, move the current level and frequency back and forth to confirm that the level make 7 changes linearly.

This confirms that the mixer of the measurement system is not overloaded and ensures that the measurement system is operating normally. In other words, the normal operation of the measurement system is also guaranteed for the measurement system measuring the oscillator measured by the equivalent FM linear detector 4 and level meter 6.

This makes it possible to measure the oscillator 1 up to the measurement capability limit of this measurement system without knowing whether the oscillator 1 is mounted or not.

Furthermore, when the measurement system of the present invention is used, the control section 8 applies appropriate modulation to the standard signal generator 2, making it possible to calibrate the measurement section consisting of an FM linear detector and a level meter. Since the measurement system is calibrated immediately before measurement, highly accurate measurements are also possible from this point of view.

In addition, the demodulator of the FM linear detector requires time after the signal is applied until a stable signal is output, which causes an increase in measurement time, but in this measurement system, the oscillator measurement This allows you to perform measurements on the standard signal generator side while performing measurements on the oscillator side after confirming that the measurements on the standard signal generator side are the true values, which eliminates unnecessary waiting time. This is advantageous in terms of shortening the I111 time, making it suitable for introduction into manufacturing inspection lines.

As described above, according to the present invention, it is now possible to introduce spectral purity measurement using the FM linear detection method, which has conventionally been carried out in laboratories, into the manufacturing inspection line. It becomes possible to measure.

[Brief explanation of drawings]

The figure is a configuration diagram showing an embodiment of the present invention. In the figure, 1 is an optical pump, 2 is a standard signal generator, 3 is a switching section, 4 and 5 are FM linear detectors, 6 and 7 are level meters, and 8 is a control section.

Claims (2)

[Claims] (1) The first oscillator is tuned to the measurement frequency of the oscillator under test.
FM demodulation output is obtained, and the same measurement frequency as the oscillator is tuned to the standard signal to obtain a second FM demodulation output,
j: - Confirm the linearity of the first FM demodulated output by controlling the modulation degree of the standard signal so that the first and second demodulated outputs are equal (ζ) A method for measuring spectral purity, comprising replacing the connection between the oscillator and the standard signal and converting the spectral purity from the demodulated output of the oscillator. (2) a standard signal generator, a switching device that alternately switches the output of the oscillator under test and the output of the standard signal generator, and a first and second signal generator connected to their respective inputs by the switching device;
an FM linear detector, a first level meter connected to the demodulated output of the first FM linear detector, and a first level meter connected to the demodulated output of the first FM linear detector;
A spectral purity measuring device comprising: a second level meter connected to a demodulated output of an M linear detector; and a control section that obtains instruction outputs from the first and second level meters.