JP3102657B2 - Spectrum analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrum analyzer, and more particularly to a spectrum analyzer capable of simultaneously measuring an input signal waveform and its average value in a zero span mode.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional spectrum analyzer.
This will be described with reference to FIG. The RF signal input to the input terminal 1 is adjusted to an appropriate level by the variable attenuator 2, input to the mixer 3, and frequency-mixed with the output of the sweep oscillator 4. The output of the mixer 3 is input to a BPF (band-pass filter) 6, a beat frequency signal (intermediate frequency signal) of both inputs is selected, input to a step amplifier 7, and amplified to an appropriate level to be detected by a detector. 8 and envelope-detected. The output of the detector 8 is input to the A / D converter 10,
A / D conversion is performed. The output of the A / D converter is the image memory 1
1 and the display data for one screen is written.
The display data read from the image memory 11 is displayed on the display 14 through the display control circuit 13. The sawtooth ramp voltage is supplied from the ramp signal generator 5 to the sweep oscillator 4 and to the display 14 through the display control circuit 13. Each part is controlled by the control circuit 12. The setting data required for the measurement is input to the control circuit 12 from a keyboard 15 provided on the front panel, for example. The control circuit 12 is provided with a CPU (Central Processing Unit).

[0003]

SUMMARY OF THE INVENTION Conventional spectrum
The analyzer has a zero-span mode (a mode in which the frequency of the swept oscillator is fixed and it operates as a tuned receiver)
Has no function of measuring the average value of the input signal waveform. Therefore, in the present invention, in the zero span mode, it is possible to display (measure) the average value together with the input signal waveform to improve the cost performance.

[0004]

[Means for Solving the Problems]

(1) An input signal is input to a mixer, mixed with an output of a sweep oscillator, an intermediate frequency signal of the mixer output is detected by a detector, and the detected output is input to an A / D converter, and the A / D converter
The invention according to claim 1, wherein the output of the D converter is written in an image memory, the data in the image memory is read out and displayed on a display, and each part is controlled by a control circuit. , A part of the output of the detector is input to the additional A / D converter through the low-pass filter, and the output from the additional A / D converter is equivalent to one screen written in the image memory. Write the data corresponding to the data to the additional memory. CPU (Central Processing Unit) built in the control circuit
By calculating the average value of the data of the additional memory,
The calculated value or a DC waveform corresponding to the calculated value is displayed on the display together with the data for the one screen in the image memory.

(2) In the invention of claim 2, in the above (1), instead of providing the additional A / D converter, the A
The / D converters are alternately switched by switch means for use.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to FIGS.
In the embodiment of FIG. 1 corresponding to claim 1, a low-pass filter 21, an additional A / D converter 22, an additional memory 23, and a memory means 24 are added to the conventional spectrum analyzer.

In the zero-span mode, a part of the output of the detector 8 is smoothed by the low-pass filter 21 and input to the additional A / D converter 22. The reason for smoothing by the low-pass filter 21 is to reduce a sampling error in the next additional A / D converter. (Sampling errors are more likely to occur in narrower peak waveforms.) On the other hand, part of the output of the detector 8 is directly A
/ D is input to the transducer 10, one screen of data output from the A / D converter 10 (corresponding to W ₁ in FIG. 2) is written into the image memory 11. One screen of data output from the additional A / D converter 22 (equivalent to W ₂ in FIG. 2,
Corresponding to W ₁ in FIG. 2) is written into the additional memory 23.

[0008] internal CPU in the control circuit 12 reads out the one screen of data of the additional memory 23, calculates the average value thereof (corresponding to W ₃ and AV in FIG. 2), the memory and the calculation value Means 24, and the calculated value (A in FIG. 2)
V) and its calculated value and the corresponding DC waveform (W _{3 in} FIG. 2)
Of the image memory 11 together with data for one screen (input waveform data W ₁ in FIG. 2).
To be displayed. AV in FIG. 2 indicates average value data (numerical values). The data (waveform data smoothed by the low-pass filter 21) written in the additional memory 23 itself is not displayed.

[0009] When calculating the average value of the input waveform,
It is well known that the same result can be obtained by integrating an input waveform with a low-pass filter and calculating an average value from the integrated waveform. By the way, the A / D converter is generally expensive, so that the additional A / D converter 22 is not provided and switches 25 and 26 interlocked with the input and output terminals of the A / D converter 10 as shown in FIG. And the input end of the A / D converter 10 is alternately switched between the conventional path in which the low-pass filter 21 is not inserted and the output end of the low-pass filter 21, and at the same time, the A / D converter The output terminal 10 may be alternately switched between the input terminal of the image memory 11 and the input terminal of the additional memory 23, and the input signal waveform and its average value may be measured alternately. However, in this case, the displayed input waveform and the average value (or the average waveform) are shifted by one sweep time.

The control circuit 12 serves as the memory means 24.
Alternatively, a built-in memory or register can be used.

[0011]

As described above, according to the present invention, the low-pass filter 21 and the additional A /
By adding the D converter 22 (or the switches 25 and 26), the additional memory 23 and the memory means 24, it is possible to measure the average value together with the input signal waveform in the zero span mode. Therefore, the cost performance of the apparatus can be greatly improved, and the usability is extremely improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a display example of an input signal waveform displayed on a display 14 of FIG. 1 and an average value thereof.

FIG. 3 is a block diagram showing an embodiment of the invention of claim 2;

FIG. 4 is a block diagram of a conventional spectrum analyzer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-1564 (JP, A) JP-A-1-167678 (JP, A) JP-A-60-144669 (JP, A) JP-A-58-58 39962 (JP, A) Japanese Utility Model 60-6045367 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 23/173 G01R 13/20

Claims (2)

(57) [Claims] An input signal is input to a mixer, mixed with an output of a sweep oscillator, an intermediate frequency signal of the mixer output is detected by a detector, and the detected output is input to an A / D converter,
The output of the A / D converter can be written to an image memory, the data in the image memory can be read out and displayed on a display, and the spectrum analyzer in which each unit is controlled by a control circuit, A part of the output of the filter is input to the additional A / D converter through the low-pass filter, and the output of the additional A / D converter corresponds to the data for one screen written in the image memory. The data is written into the additional memory, and the CPU (Central Processing Unit) built in the control circuit calculates the average value of the data in the additional memory, and calculates the calculated value or the DC waveform corresponding to the calculated value in the image A spectrum analyzer displaying the data of one screen in a memory together with the data on the display. 2. A spectrum analyzer according to claim 1, wherein said A / D converter is alternately used by switching means instead of providing said additional A / D converter.