JPS6029904B2 - spectrum analyzer - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a spectrum analyzer that receives signals in a wide frequency band while sweeping and displays the absolute level of the received signal on the frequency axis on the indicator. The present invention relates to a marker method in which the frequency of a received signal is measured using a variable marker displayed on the same indicator.

Figure 1 shows the basic system diagram of the spectrum analyzer.

The received signal is mixed with the swept local oscillator signal from the sweep local oscillator 2 by the mixer 1, converted to an intermediate frequency, amplified and detected by the detector 4, and displayed on the indicator 5. On the other hand, a marker serving as a means for measuring the frequency of the received signal is generated by the marker generating section 7, controlled by the manual marker controller 6, and displayed on the display of the indicating section 5 to be distinguished from the received signal. This marker is controlled by a manual marker controller 6 and its position on the display 5 is varied. Then, the frequency of the target received signal is determined by matching the marker with the received signal displayed on the indicator and reading the control signal of the movement marker controller 6 using the decoder 8. This is a marker method. It is a method of common knowledge. There are basically two types of marker methods: the "digital marker method" in which marker generation and control are performed digitally, and the "frequency marker method" in which a reference signal with a known frequency is used as the marker signal. and an overview of the operation. The basic system diagram of the digital marker method is the same as that shown in FIG. 1 above, and the timing chart of various signals is shown in FIG. 2.

First, the following marker processing is performed in the marker generating section 7 of FIG. In the sweep signal generating section 3 of FIG. 1, the sweep control signal shown in FIG. 2a is generated, and in synchronization with this, the marker shown in FIG. 2b is generated. Next, this marker is controlled by the manual marker controller 6 by an amount corresponding to the control amount (
After being delayed (generally digitally) and further inverted, the waveform shown in FIG. The frequency of this marker is determined by the degoder 8 reading the control signal of the manual marker controller. In this method, frequency measurement errors occur due to frequency nonlinearity and frequency fluctuations of the swept local oscillator signal. Even if the marker matches the received signal on the indicator, the received signal is shifted and displayed on the indicator by the frequency non-linearity and frequency fluctuation of the swept local signal, so the amount of shift corresponds to this amount. Frequency measurement errors occur. Generally, as a sweep signal generator, a voltage controlled oscillator (VTO) using a voltage control unit, a YIG oscillator using current control, etc. are used from the viewpoints of wide band, 4-inch size, light weight, and low cost. The linearity and frequency stability become worse as the frequency range and temperature range become wider. An example of frequency measurement error due to frequency nonlinearity is shown in FIG. The solid line in FIG. 3a shows a typical control voltage v versus oscillation frequency f characteristic curve of a voltage controlled oscillator (VTO), and the dashed line shows ideal linearity.

The waveform on the indicator at this time is shown in FIG. 3b. The marker in this case has its polarity reversed and is displayed below the received signal. As shown in this figure, even if the signal markers match, the correct position of the received signal is indicated by the broken line, and the difference between this actual situation and the broken line is the frequency measurement error. Next, a basic system diagram of the frequency marker method is shown in FIG. 4, and a timing chart of various signals is shown in FIG. 5.

The marker signal generating section 21 generates a single frequency signal with good frequency stability, which is controlled by the manual marker controller 22 and designated as a reference marker signal. This marker signal is transmitted by the switch 21 to the fifth signal generated by the marker trigger signal generator 31.
The marker trigger signal shown in Figure a is applied to the mixing section 25 only when it is "1". The sweep local oscillator 26 is controlled by a sweep control signal from the sweep signal generator 27 shown in FIG. Signals and markers shown in c.
The received waveform is obtained. This signal is separated into a signal and a marker by the signal/marker separation section 29 according to the previous marker trigger signal and displayed on the indicating section 3. An example of the output waveform of the signal/marker separator 29 is shown in FIG. 5d. An example of this is the separation of markers by polar reactions. In addition, 23 in the figure
24 is a decoder, 24 is a switch, and 31 is a marker trigger signal generator. In this method, if the frequency stability of the marker signal generation section is improved, the frequency measurement error caused by frequency nonlinearity and frequency fluctuation of the central station signal, which was a problem with the previous digital marker method, will not be a problem. . However, since the marker signal of the radio frequency (RF) signal is directly controlled, response time due to frequency switching (or variation) is a problem. Therefore, even if you try to quickly align the marker with the received signal, it will not be possible quickly and it will take time to measure the frequency. Frequency synthesizers are currently widely used as standard signal generators that generate high-frequency signals with high frequency stability over a wide frequency range, but they use phase locking (PLL)
Many of them use this method, and it takes time to synchronize. Therefore, in this method, the biggest practical problem is that it takes time to measure the frequency due to the response time due to frequency switching (or variable) of the marker signal generating section. In other words, in frequency measurement using the marker method of a spectrum analyzer, the digital marker method has a relatively quick measurement time but has a large amount of measurement error, while the frequency marker method has less measurement error but takes a long time to measure. Both methods have advantages and disadvantages.

The present invention is a frequency measurement method for a spectrum analyzer.
In the marker method, the problems of both the frequency measurement error in the digital marker method and the frequency measurement time in the frequency marker method are solved by combining the advantages of the two methods. The present invention provides a marker method that realizes accurate and high-speed frequency measurement. The present invention solves the problem of frequency measurement error and frequency measurement time in the marker method, which is one of the frequency measurement methods of spectrum analyzers, by using a reference frequency marker using a plurality of high frequency oscillators with high frequency stability as markers. By combining signal adoption, reception, and marker signal processing using a delay line after detection, improvements have been made to realize high-precision and high-speed frequency measurement with a simple equipment configuration. That is, according to the present invention, a high frequency marker signal is temporally switched with a received signal and inputted as an input signal, and after receiving and detecting this input signal, the marker signal and the received signal are separated and each A spectrum analyzer that displays on the same indicator includes at least one fixed frequency oscillator that has high frequency stability and generates a marker signal corresponding to a reference frequency, and an output of the fixed frequency oscillator. a delay means for delaying the received signal by a predetermined time; and a marker signal indicating the correct frequency of the received signal is displayed by interpolating the reference frequency using the delay time obtained from the delay means. You will get Muanalyzer. Next, an embodiment of the present invention will be described with reference to FIG.

Reference numeral 41 denotes a reference marker signal generating section, which is composed of a plurality of oscillators with high frequency stability, one oscillator corresponding to each receiving frequency band divided into a plurality of bands.

Generally, if the reception frequency range is divided into n bands, it will consist of n oscillators. 42 is a switch, 43 is a mixing section, 44 is a sweep local oscillation section, 45 is a sweep signal generation section, 46 is a detection section, 50
51 is an instruction section, 51 is a marker trigger signal generation section, 52 is a manual marker control section, and 53 is a decoder, which are the same as those shown in FIG. 4 above.

Reference numeral 47 denotes a signal/marker separation unit that temporally separates the signal and marker and outputs independent outputs.

48 delays the marker by an amount controlled by a marker delay section.

49 combines the signal and the delayed marker and outputs it.

Next, an outline of the operation will be described with reference to FIG.

The reference frequency marker signal selected in the reference marker signal generation section 1 by the received frequency band selection signal from the manual marker controller 52 is changed to the reference frequency marker signal generated by the marker trigger signal generation section 51 by the switch 42 in FIG. It is applied to the mixing section 43 only when the marker trigger signal shown is "1". The steps from this point up to the output of the detection section 46 are the same as the frequency marker method described earlier, and this received waveform is
Shown in Figure c. This signal is sent to the signal/marker separator 47,
It is temporally discriminated by the preceding marker trigger signal, and is separated into the received signal shown in FIG. 7d and the marker shown in FIG. 7e, and each is output independently. The marker is delayed by a predetermined amount in the marker delay unit 48 according to the control signal from the manual marker controller 52 as shown in FIG. The images are combined and displayed on the instruction section 50. In the figure, FIG. 7b shows the sweep control signal of the sweep signal generator 45, and FIG. 7g shows the signal/
The output waveform of the marker separation unit 47 is shown. Based on its control signal, the marker first generates a standard frequency marker signal that corresponds to the receiving frequency band and has good frequency stability but is rough in terms of frequency. After receiving and detecting this, it is separated from the receiving signal and placed in the delay section. The final marker is then delayed by the difference in frequency. In other words, it can be said to be a type of Okema method in which a coarse reference frequency marker is first generated, and after reception and detection, the difference between the coarse reference frequency marker and the fine frequency marker is interpolated in the delay section. According to this method, the frequency measurement errors caused by the frequency nonlinearity and frequency fluctuation of the swept local oscillator signal, which were problems with the digital marker method, can be solved by using multiple reference frequency marker signals with high frequency stability. The slow frequency measurement time due to the fast response time due to frequency switching (variable) of the high frequency marker signal, which was a problem with the frequency marker method, has been improved by switching and receiving the reference frequency marker oscillator. This is improved by signal processing of the marker after detection.

In other words, by combining the advantages of the digital marker method and the frequency marker method, the disadvantages of each marker method are improved. As explained above, according to the present invention, it is possible to obtain a spectrum analyzer that has no frequency measurement error and shortens frequency measurement time.

[Brief explanation of drawings]

Fig. 1 is a basic block diagram of the spectrum analyzer, Fig. 2 a to Fig. 2 are time charts of signals of each part in Fig. 1,
Figure 3a is a control voltage vs. oscillation frequency characteristic diagram of a typical voltage controlled oscillator, Figure 3b is a diagram displayed on the display when the oscillator shown in Figure 3a is used, and Figure 4 is a frequency marker. Block diagram of the spectrum analyzer according to the method, Figure 5 a~
FIG. 6 is a block diagram of the spectrum analyzer according to the present invention, and FIGS. 7 a to 7 g are time charts of signals of each part in FIG. 6. 1, 25, 43... Mixing section, 2, 26, 44...
...Sweep local oscillator, 3, 27, 45... Female signal generator, 4, 28, 46... Detector, 5, 3
0, 50... Instructor, 6, 22, 52... Manual marker controller, 7... Marker control generator, 8, 23, 53... Decoder ,21,41・
... Marker signal generation section, 24, 42 ... Switch,
29, 47...signal/marker separation section, 31, 51...
...Marker trigger signal generation section, 48...
- Marker delay section, 49... Signal/marker synthesis section. Figure 1 Tsutomu Z Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. A high frequency marker signal is temporally switched with the received signal and input as an input signal, and after receiving and detecting this input signal, the marker signal and the received signal are separated and each is displayed on the same indicator. at least one fixed frequency oscillator that has high frequency stability and generates a marker signal corresponding to a reference frequency, and a marker that is obtained by detecting the output of the fixed frequency oscillator and separating it from the received signal. and a delay means for delaying the signal for a predetermined period of time, the reference frequency is interpolated by the delay time obtained from the delay means, and a marker signal indicating the accurate frequency of the received signal is displayed. spectrum analyzer.