JPH0633085U - Spectrum analyzer - Google Patents

Abstract

(57) [Abstract] [Purpose] Analysis can be performed on irregularly short inputs such as burst waves, and swept in a wide band and at high speed. Real-time spectrum analysis can be performed for a wide frequency band. It is to provide a spectrum analyzer that can perform. A mixed down signal is divided into m frequency bands (Δf) and input to N A / D converters 19, 20 and 21 operating in parallel to perform simultaneous processing. Local oscillator
The oscillation frequencies of 6,26 are swept stepwise with a frequency width of N · Δf.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a spectrum analyzer that performs frequency spectrum analysis, and particularly to a wideband and high-speed spectrum analyzer that enables real-time spectrum analysis of not only continuous waves but also burst waves.

[0002]

[Prior art]

 A conventional spectrum analyzer mixes an input signal with a local oscillation signal to convert it into a low frequency signal, and a variable bandwidth bandpass filter (analog filter that determines frequency resolution) converts the input signal into a predetermined frequency band. After the signal is selected, it is logarithmically compressed by the Log amplifier, the signal level is detected by the detector, and the frequency is analyzed.

[0003]

[Problems to be solved by the device]

 In the conventional spectrum analyzer described above, when the input signal is a continuous wave, there is no restriction on the time required for the analysis because the signal is continuously supplied, and if the frequency of the local oscillation signal is swept linearly. , The signal level of each frequency component of the input signal can be sequentially detected. However, if the input signal is a signal such as a burst wave that is suddenly input in a short period of time (and the waveform changes with no periodicity with respect to time), it may occur during the sweep of the local oscillation signal. The input may be interrupted, and in such a case, there is a problem that all frequency components cannot be analyzed.

The present invention has been made based on such a consideration, and its purpose is to perform analysis on an irregularly short input such as a burst wave, and further, to perform wideband and high-speed analysis ( The objective is to provide a spectrum analyzer that is capable of high-speed sweeping and that can perform real-time spectrum analysis over a wide frequency band.

[0005]

[Means for Solving the Problems] The outline of a typical one of the present invention is as follows. In other words, it is a digital spectrum analyzer using N (natural number of 2 or more) A / D converters, and the mixed down signal is in m frequency bands (the frequency width of each band is Δf). It is divided into two parts and input to N A / D converters operating in parallel to execute simultaneous processing. The sampling frequency of each A / D converter is 2 · Δf or more, and has a real-time processing function within the band of Δf. The oscillation frequency of the local oscillator for performing the low frequency conversion of the input signal is stepwise swept with a frequency width of N · Δf.

[0006]

[Action]

 Since the step sweep width can be set to N · Δf, it is possible to perform high-speed sweep over a wide frequency band. Further, since N A / D converters operate simultaneously and each performs real-time analysis on the signal in the Δf band, high speed and high resolution can be achieved.

[0007]

【Example】

 Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. In this embodiment, in order to obtain a wide frequency band, it is divided into two frequency ranges by the switches 3 and 10 and has an internal configuration having a circuit for each, and the upper circuit is for the low frequency range and the lower circuit is for the lower frequency range. The side circuit is for high frequency range. Further, three A / D converters 19, 20, 21 are provided so that they can be operated in parallel.

The input signal to be measured is level-adjusted by the attenuator 1 and passes through the limiter 2 for protection against excessive input. In the case of the low frequency range, after passing through the LPF 4, the variable frequency oscillator (local oscillator) 6 and the mixer 5 once mix up (convert to a high frequency) and separate so as not to overlap the original signal. After that, only the required pass band is selected by the BPF 7 (for example, only the right side of the left and right difference signals centering on the local oscillation frequency is selected). Next, mixing is performed by the fixed frequency oscillator 8 and the mixer 9 (conversion to low frequency). In the case of a high frequency range, only a predetermined pass band is selected by a pre-tuning BPF (band pass variable band pass filter) 24, and mixing down is performed by a variable frequency oscillator 26 and a mixer 25. The low-frequency converted signal is further mixed down by the fixed frequency oscillator 13 and the mixer 14 after passing through the BPF 11 and the amplifier 12.

As shown in FIG. 2, the mixed down signal is divided into three frequency bands 0 to f1, f1 to f2, and f2 to f3 by LPF16, BPF17 and BPF18. The bandwidth of each is Δf. The divided signals are simultaneously A / D converted by the A / D converters 19, 20 and 21 operating in parallel. The sampling frequency of the A / D converters 19, 20 and 21 is set to 2 · Δf or more so as to satisfy the sampling theorem, and each A / D converter performs real-time processing on the Δf band. The signals from the A / D converters 19, 20 and 21 are digitally processed and displayed on the display 23. The control circuit 15 controls the switching of the switches 3 and 10 and the step sweep of the local oscillator.

Sweeping of the oscillation frequencies of the oscillators 6 and 26 is performed stepwise with a width of 3 · Δf, as shown by the solid line in FIG. In the figure, the dotted line shows the frequency band that the three A / D converters 19, 20, 21 are in charge of, and the parallel operation makes it possible to obtain a resolution equivalent to that obtained by step-sweep with a width of Δf. .

Each A / D converter can perform real-time (real-time) spectrum analysis on a signal within the width of Δf. Therefore, if the frequency band of the signal for which spectrum analysis is to be performed is within this width, step sweep of the local oscillator is not necessary, and step sweep only needs to be performed when exceeding this width, and high-speed analysis can be performed. Since high-speed analysis is possible in this way, it becomes possible to analyze sudden signals such as burst waves. Note that the number of A / D converters used is not limited to three, and may be two or more.

As a method of dividing the frequency band for a plurality of A / D converters, fixed frequency oscillators 31, 33, mixers 30, 33, and LPFs 34, 35 are used as shown in FIG. The mixing down technology that was used may be adopted. In this case, there is an advantage that it is not necessary to widen the band of the sample / hold circuit in the A / D converters 36 and 37.

[0013]

[Effect of device]

 As described above, according to the present invention, the frequency conversion by the step sweep of the local oscillator and the digital signal processing method using a plurality of A / D converters operating in parallel are adopted, so that the function of the conventional spectrum analyzer is improved. In addition to this, a high-speed, wideband real-time spectrum analysis function can be realized.

Further, by using digital signal processing, an analog filter having a variable bandwidth, which has been conventionally required, is unnecessary, and a narrow band can be obtained as compared with an analog filter, so that frequency resolution can be improved.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining how frequency bands are divided by filters 16, 17, and 18 in the embodiment of FIG.

FIG. 3 is a diagram showing an example (solid line) of step sweep of the local oscillation frequency in the embodiment of FIG. 1 and a band assigned to each A / D converter operated in parallel.

FIG. 4 is another example of a method of dividing a frequency band for a plurality of A / D converters (technology using mixing down).
FIG.

[Explanation of symbols]

1 Attenuator 2 Limiter 3,10 High frequency range / low frequency range selector switch 4 LPF 5,9,14,25 Mixer 6,26 Variable frequency oscillator (local oscillator) 7 BPF 8,13 Fixed frequency oscillator (local oscillator) 11 BPF 12 Amplifier 15 Control circuit 16 LPF 17,18 BPF 19,20,21 A / D converter 22 Digital signal processing 23 Display 24 Pretune BPF

Claims (1)

[Scope of utility model registration request] 1. A local oscillator (6, 26) and a mixer (5, 5).
25), a filter circuit (11), a frequency band division circuit (16,17,18) and a plurality of A / D converters (19,20,21) are provided, and an input signal is supplied to the local oscillator. Frequency conversion is performed by mixing with the local oscillation signal of (6, 26), the frequency-converted signal is passed through the filter circuit (11), and then the frequency band division circuit (16, 17, 18) determines the frequency. Of the frequency band, and each of the frequency-divided signals is input to each of the plurality of A / D converters operating in parallel and converted into a digital signal for frequency spectrum analysis. A spectrum analyzer characterized in that the oscillation frequency of the local oscillator (6, 26) is swept stepwise.