JPH05188100A - Spectrum analyzer - Google Patents

Abstract

PURPOSE:To obtain information close to the information obtained in the case of displaying without storing detection output. CONSTITUTION:Fixed cycle pulses are generated from a saw-tooth-wave control part 15, and a saw-tooth-wave signal raised one step by the pulse is generated from a generator 16. The oscillation frequency of a local oscillator 13 is controlled by this saw-tooth-wave signal, so that the frequency of input signals taken in by a frequency converter 11 is swept, and the output of a frequency converter 12 is detected. The pulses from the saw-tooth-wave control part 15 are also supplied to a plural pulse generator 26. During one cycle of each one of these pulses, twenty pulses are generated at equal intervals. With each pulse, the detection output is converted into a digital signal in an AD converter 21. These digital signals are temporarily stored in a time axis memory 27, and two levels are stored in a frame memory 22, in the order of high frequency in the generation level every frequency sweeping step by a control processing part 14. The stored content of the frame memory 22 is then displayed on a display 19, in the display mode of continuous lines and dotted lines, for instance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention changes a receivable frequency stepwise, receives an input signal at each step, detects the received signal, and converts the detected output into a digital signal to obtain the signal. It is related to the spectrum analyzer.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional spectrum analyzer of this type. The input signal from the input terminal 11 is supplied to the frequency converter 12, and is converted into an intermediate frequency signal by the local signal from the local signal oscillator 13. When the start command, the sweep speed, and the like are given from the central processing unit 14 to the sawtooth wave control unit 15, the sawtooth wave control unit 15 generates pulses at pulse intervals according to the sweep speed to generate a sawtooth wave signal generator. 1
Supply to 6. Each time a pulse is input, the sawtooth wave signal generator 16 cumulatively adds and outputs a constant voltage, and a staircase sawtooth wave signal is output. The oscillation frequency of the local signal oscillator 13 is controlled by this sawtooth wave signal. Therefore, the frequency of the input signal of the input terminal 11 taken into the intermediate frequency amplifier 17 as the output of the frequency converter 12 is changed stepwise.

The output of the intermediate frequency amplifier 17 is detected by a detector 18, and the detected output is indicated by a display 19 as shown by a dotted line.
Is supplied as a vertical deflection signal, and the sawtooth signal generator 16 supplies the sawtooth signal to the display 19 as a horizontal deflection signal. In this way, the frequency component (spectrum) of the input signal is displayed on the display device 19. Even if the input signal fluctuates or is cut off, the output of the detector 18 is changed to AD every time one pulse is input to the sawtooth wave signal generator 16 so that the frequency components of the input signal up to that point can be displayed.
The converter 21 converts it into a digital signal, writes the digital signal in the frame memory 22, and reads the frame memory 22 in synchronization with the sawtooth wave signal. The DA converter 23 converts the read digital signal into an analog signal. And is supplied to the display device 19.

[0004]

When the output of the detector 18 is supplied to the display unit 19 without being converted into a digital signal, if the input signal fluctuates instantaneously, a display corresponding to this is displayed. Appears in container 19. For example, as shown in FIG. 3A, a bright portion 24 that is wide in the vertical direction and wholly shining in response to a change in the input signal, and a wide shining portion 24, and a portion 25 where particularly strong brightness appears, appear. It can be seen that in the portion 24, the input signal level fluctuates relatively fast and relatively large, and in the portion 25, the luminance becomes strong because the input signal level fluctuates relatively slowly. It is called that the moire appears when the shade display appears. When moire appears in this way, the state of noise can be intuitively known in the display example of FIG. 3A.

However, when the detected output is converted into a digital signal and is captured in the frame memory 22 and then displayed,
1 for frequency sweep step, ie frequency resolution
Only one data is displayed. Therefore, for the input signal corresponding to the display of FIG. 3A, the display becomes as shown in FIG. 3B, for example, and one frequency step (frequency resolution unit)
In regard to the above, the luminance at one point appears with the same luminance, and it is not possible to know the change state of the input signal (noise) at that one frequency step.

[0006]

According to the present invention, a signal is captured a plurality of times at each frequency step in the sweep of the input frequency, and the signal level is obtained according to the frequency of the signal level obtained at each frequency step. Display is performed.

[0007]

FIG. 1 shows an embodiment of the present invention, in which parts corresponding to those in FIG. 2 are designated by the same reference numerals. In this embodiment, every time a pulse is supplied from the sawtooth wave controller 15 to the sawtooth wave signal generator 16, the pulse is supplied to the multiple pulse generator 26, and the multiple pulse generator 26 outputs one pulse. For each input, a plurality of pulses, for example, 10 to 20 pulses are generated at equal intervals during the one pulse period, the pulses are supplied to the AD converter 21, and the detector 18 is supplied for each pulse. The output of is converted into a digital signal.

This digital signal is taken in by the time base memory 27, and the central processing unit 14 reads the digital signal stored in the time base memory 27 by the central processing unit 14 in one step of the frequency sweep, and performs one frequency sweep. In a step, if the level is the same, a predetermined value, for example, three or more, that is, if the occurrence frequency is a predetermined value or more, each value is stored as data for the frequency step of the frame memory 22. Therefore, if there are two data that are more than a certain number of times, the two points indicating the two levels are
It appears as luminance for the corresponding frequency of the display 19.

For example, as shown in FIG. 1B, when the input signal is changing to the level L ₁ or L ₂ in the step of the frequency f _a in the frequency sweep,
Although only appear any level L ₁ or L ₂ in the frequency f _a in the conventional, two points of the level L ₁ and L ₂ at the frequency f _a in this embodiment is displayed. Actually, the bright spot display of the level L _{1 and} the bright spot display of the level L ₂ are performed in a time division manner. Therefore, for example, when the level of the input signal changes to a solid line and a dotted line as shown in FIG. 1B, conventionally, only the solid line level or the dotted line level is displayed at each frequency step, but in this embodiment, , Both the solid line waveform and the dotted line waveform are displayed, and information similar to the information obtained by the conventional moire can be obtained.

As described above, a signal is captured a plurality of times in one frequency step, a plurality of, for example, two pieces of data are displayed in the descending order of the occurrence level frequency, and the plurality of displayed data have higher brightness as the frequency is higher. By doing so, it is possible to get closer to the conventional moire. The display is not limited to the case where a plurality of predetermined numbers are displayed in descending order of frequency, but all of the frequencies having a predetermined value or more may be displayed. Further, instead of the frame memory 22, a video memory having a memory cell corresponding to each pixel of the screen of the display 19 is provided, and each memory cell is
It is also possible that the central processing unit 14 stores the data corresponding to the display data, and that the display unit 19 performs horizontal and vertical scanning, and the video memory is read and displayed in synchronization with the scanning.

[0011]

As described above, according to the present invention, a signal is captured a plurality of times at each frequency step, and a plurality of signals having a high occurrence level are displayed so that the signal is captured. However, it is possible to obtain information close to the information obtained by the moire appearing in the conventional device which does not store the signal.

[Brief description of drawings]

FIG. 1A is a block diagram showing an embodiment of the present invention, and B is a diagram for explaining a display example thereof.

FIG. 2 is a block diagram showing a conventional spectrum analyzer.

FIG. 3 is a diagram showing a display example in a conventional spectrum analyzer.

Claims (1)

[Claims] 1. A spectrum analyzer in which a receivable frequency is changed stepwise, an input signal is received at each step, the received signal is detected, and the detected output is converted into a digital signal and taken in. A spectrum analyzer comprising: means for capturing a signal a plurality of times at each frequency step; and means for displaying at each frequency step according to the frequency of the obtained signal.