JP2000333214A - Single channel spectrum analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a single channel spectrum analyzer for searching radio wave interference where miniaturization, light weight, low cost, saved power consumption and simplified operability are attained and radio wave interference can surely and easily be searched. SOLUTION: A tuner pack 11 of this single channel spectrum analyzer limits a frequency band of an RF input signal at VHF and UHF bands to the bandwidth equivalent to a bandwidth of one channel of a television broadcast wave and selects the channel, converts the RF input signal whose bandwidth is equivalent to the bandwidth of one channel of the selected television broadcast wave into a 1st IF signal of the same bandwidth by using a local oscillation frequency signal of an upper side heterodyne system, a BVCO/DBM block 21 converts the 1st IF signal into a 2nd IF signal with a sweep signal having the local oscillation frequency of the upper side heterodyne system whose bandwidth is equivalent to the bandwidth of the one television channel, a 2nd IF block 3 limits the bandwidth of the 2nd IF signal, a log detection block 4 detects a signal obtained by the 2nd IF block 3 and a CRT display device 6 displays the signal obtained by the log detection block 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double-conversion spectrum analyzer, and more particularly to a single-channel spectrum analyzer for radio interference detection that can reliably and easily detect radio interference.

[Summary of the Invention] [0002] The present invention relates to a radio wave disturbance (hereinafter referred to as a booster oscillation disturbance) caused by abnormal oscillation of a home amplifier occurring in a television broadcast wave band (VHF, UHF) in a general reception environment, a power company, BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-channel spectrum analyzer for detecting radio interference used to detect an interference source such as a pulse interference due to spark discharge generated from a insulator of a power line pillar of a railway company.

Conventionally, a spectrum analyzer used for detecting an interference source is heavy, about 5 kg, even if it is a portable type. For this reason, it is inconvenient for a detector to detect radio interference while carrying a spectrum analyzer. Further, the price of a spectrum analyzer is usually as high as about 500,000 yen or more, and it is extremely difficult to own the spectrum analyzer at a general electronics store or the like.

[0004] Therefore, the present invention provides a compact and lightweight device.
Reducing the main functions of the spectrum analyzer to the minimum necessary functions that can detect radio interference in order to reduce costs, save power, and simplify operability. What to do.

[0005]

2. Description of the Related Art A conventional spectrum analyzer is a device mainly used for measuring a radio wave frequency and a power level (intensity) at the frequency. Its main function is to measure a frequency range from several kHz to several kHz. Display and measure GHz frequency, display frequency range according to application,
And several resolution bandwidths can be selected.

[0006] A conventional sweep type spectrum analyzer of this kind in the related art uses a first type in order to suppress image disturbance.
In the IF converter, the input frequency is converted into a frequency band (2 to 4 GHz) higher than the input frequency,
A low-pass filter is inserted in the input section so that no signal exceeding the measurement band is applied.

[0007] An example of this relationship is as follows. When the input frequency range is 10 kHz to 2 GHz and the local oscillation frequency is 2.52141 to 4.52140 GHz, the intermediate frequency signal (fIF) has an input frequency of 10 kHz.
Hz, fIF = 2.52141−0.00001 = 2.521
4 GHz When the input frequency is 2 GHz, fIF = 4.52140-2.0000 = 2.5214
GHz, and by varying the local oscillation frequency, a constant intermediate frequency can be obtained, and the intermediate frequency is out of the band of the measurement frequency, so that the measurement is not affected.

[0008] As described above, the center frequency and the display frequency bandwidth are set to the first type so that several types can be used depending on the application.
The frequency of the first local oscillator supplied to the IF converter is varied. In addition, the usual spectrum analyzer,
The first local oscillation frequency is changed over a wide band (for example, about 1 GHz).
(Voltage Controlled Oscillator) needs to hold the characteristic of "control voltage for control vs. oscillation frequency" linearly.

However, it is difficult for a normal VCO to linearly compensate for characteristics in a wide frequency band of about 1 GHz, and an expensive and special oscillator (for example, a YIG oscillator) is required. For this reason, in the case of a spectrum analyzer, a special oscillator is usually used for the first IF converter. Further, the first local oscillation frequency is also linked to the center frequency to be measured, and by changing this, the center frequency displayed on the CRT can be changed.

[0010] The first IF signal is frequency-converted by the second IF converter, the third IF converter, and the fourth IF converter, and finally converted into a several MHz band. The converted intermediate frequency is determined by a LC (coil and capacitor) or crystal narrow-band filter to determine a resolution filter (a normal spectrum alanizer has several types of filters with different bandwidths). High signal output.

After passing through the resolution filter, the gain of the reference level is adjusted by the gain adjusting amplifier, and the logarithmic amplifier sets the logarithmic / linear amplification of the ordinate scale coefficient. Thereafter, the signal is detected and passed through a video low-pass filter to remove a random noise component included in the measurement signal, and an accurate signal level is sent to a CRT (Y axis).

On the other hand, the television broadcast wave band (VHF, U
Radio interference (hereinafter referred to as booster oscillation interference) occurs due to abnormal oscillation of the home amplifier used in HF), or radio interference (pulse interference) caused by spark discharge from a power line pillar of a power company or railway company. It often happens. For example, oscillation failures caused by boosters processed by NHK, commercial broadcasters, radio communication control bureaus, etc. nationwide are as follows:
10 years from the fiscal year to 1996, the annual average is about 4
800 cases have occurred, and no significant change has been seen in recent years. (Source: Central Council for Prevention of Interference).

When a conventional spectrum analyzer of this type is used for detecting a radio interference in order to detect such an interference source of the radio interference, an input terminal of the spectrum analyzer is connected to an antenna. And
The disturbing wave arriving at the antenna from the disturbing source is input to a spectrum analyzer, and the disturbing wave is displayed on the screen by the spectrum analyzer. Then, the maximum direction of arrival of the jamming radio wave is detected at several points, and the source of the jamming radio wave is specified from the intersection of the maximum directions of arrival.

[0014]

However, in a conventional spectrum analyzer, the circuit configuration is complicated and expensive even with only the first to fourth IF converters, and the display frequency bandwidth is variable. For this reason, it was necessary to select a resolution filter and a video low-pass filter according to the sweep time. For this reason, the entire circuit configuration becomes complicated and expensive.

In order to detect radio interference using a conventional spectrum analyzer, it is necessary to have advanced knowledge of radio waves and accurate understanding of the functions of the spectrum analyzer. For this reason, it was difficult for a general electric appliance store, a power company, or the like who is not familiar with radio wave detection to own a spectrum analyzer for radio wave detection.

Further, since the conventional spectrum analyzer is not a device manufactured for detecting radio interference, there are many functions that are not necessary for radio interference detection, and the operation is rather complicated when performing radio interference detection. Was.

Further, most of the conventional spectrum analyzers are very expensive and multifunctional, so that the power consumption is large. For this reason, when radio wave interference detection is carried out for a long time while carrying the spectrum analyzer, the operation is limited to about two hours continuously even if the attached battery pack is used.

Further, when detecting a radio interference while carrying the spectrum analyzer, if the intensity of the interfering wave is very weak, the noise level generated from inside the spectrum analyzer (hereinafter referred to as internal noise level) cannot be ignored. In other words, because the interference wave is buried in the noise,
A weak interference wave cannot be measured on the screen of the spectrum analyzer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a single channel for electromagnetic interference detection capable of reliably and easily detecting an electromagnetic interference while reducing the size, weight, cost, power consumption, and simplicity of operation. An object of the present invention is to provide a spectrum analyzer.

[0020]

The present invention has the following arrangement in order to solve the above-mentioned problems. The single-channel spectrum analyzer according to the first aspect of the present invention comprises: a tuning unit for limiting a high-frequency input signal in the VHF and UHF bands to a bandwidth equivalent to one channel of a television broadcast wave; First intermediate frequency converting means for converting the high-frequency input signal corresponding to the bandwidth of one channel of the television broadcast wave into a first intermediate frequency signal of the same bandwidth by a local oscillation frequency signal of an upper heterodyne system; A second intermediate frequency converting means for converting the one intermediate frequency signal into a second intermediate frequency signal by a sweep signal of a local oscillation frequency of an upper heterodyne system having a sweep width equivalent to the bandwidth of one television channel; Band limiting means for limiting the bandwidth of the signal obtained by the frequency conversion means, and detecting means for detecting the signal obtained by the band limiting means. Means, characterized in that it comprises a display means for displaying the signal obtained by the detecting means.

According to the single-channel spectrum analyzer of the first aspect of the present invention, the channel selection means comprises VHF and UH
When the high-frequency input signal in the F band is selected and limited to a bandwidth corresponding to one channel of the television broadcast wave, the first intermediate frequency conversion means controls the bandwidth of the one channel of the television broadcast wave selected by the channel selection means. A corresponding high-frequency input signal is converted into a first intermediate frequency signal having the same bandwidth by an upper heterodyne local oscillation frequency signal, and the second intermediate frequency converting means converts the first intermediate frequency signal into a band of one television channel. A second intermediate frequency signal is converted by a sweep signal of the local oscillation frequency of the upper heterodyne system having a sweep width equivalent to the width, and the band limiting unit limits the bandwidth of the signal obtained by the second intermediate frequency converting unit; The detecting means detects the signal obtained by the band limiting means, and the display means displays the signal obtained by the detecting means.

That is, the measurement frequency is set to the VHF or UHF band, and the display frequency bandwidth is limited to the bandwidth of one channel of the television broadcast wave by the channel selection function of the channel selection means. Is limited to single-channel display, greatly simplifying the circuit configuration, miniaturizing, lowering cost, saving power, simplifying operability, and ensuring reliable and easy radio interference detection. it can. In addition, since the reception band is narrow, the internal noise intensity can be kept low.

According to a second aspect of the present invention, in the single channel spectrum analyzer according to the first aspect, the first
The center frequency of the intermediate frequency signal is 44 MHz, and the frequency of the second intermediate frequency signal is 10.7 MHz. According to the single channel spectrum analyzer of the second aspect of the present invention, since the center frequency of the first intermediate frequency signal is 44 MHz and the frequency of the second intermediate frequency signal is 10.7 MHz, image interference with a simpler configuration is achieved. Components and the like can be suppressed.

[0024]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a single-channel spectrum analyzer for detecting radio interference according to the present invention. FIG. 1 is a schematic block diagram of a single-channel spectrum analyzer for detecting radio interference.

When the spectrum analyzer is used for radio interference detection, accurate measurement (absolute value display) is not required, but it is sufficient that measurement for radio interference detection (relative value display) can be performed. For this reason, for example, it is not necessary to display the entire band of television and BS broadcasts on the screen of the spectrum analyzer, and if any one channel band affected by interference can be displayed, it can be used for detecting an interference source. .

Therefore, in the single-channel spectrum analyzer for detecting radio interference according to the embodiment, an inexpensive first IF converter is used in place of the special oscillator of the conventional spectrum analyzer and the first to fourth IF converters. It is characterized by using a tuner pack for television.

As shown in FIG. 1, the spectrum analyzer includes a tuner block 1, a VCO / DBM block 2, a second IF block 3, a log detection block 4, a sawtooth generation block 5, a CRT display 6, a power supply 7 It is comprised including.

(A) Tuner block The tuner block 1 converts a RF input signal input from the RF input terminal IN into a first IF signal having a first IF frequency in a 44 MHz band, and the tuner pack 11 receives the signal. Tuning voltage generating circuit 12 for setting a desired receiving frequency, tuner pack 1
A first IF filter 13 for limiting a pass band of a first IF frequency of a first IF signal output from the first IF signal, and a first IF
First IF for amplifying the first IF signal from filter 13
It comprises an amplifier 14.

The tuner pack 11 uses a tuner pack of a commercially available television of an upper heterodyne system, and converts an RF input signal into a first IF signal (center frequency: 44 MHz).
z, a bandwidth of 8 MHz), and outputs a first IF signal of a band corresponding to an arbitrary television channel.

The frequency of the RF input signal converted into the first IF signal is determined by the setting of the band changeover switch 15 provided on the tuner pack 11 and the voltage applied to the tuner pack 11 from the tuning voltage generation circuit 12. The tuning voltage is arbitrarily adjusted in a range of 0 V to 24 V by manually rotating a knob (not shown).

The band changeover switch 15 includes a low-band terminal VL for VHF and a high-band terminal V for VHF.
The band is switched by selecting any one of the terminals U for the H and UHF bands and applying +12 V to the selected terminal. The tuner pack 11 adjusts the VHF and UH from 50 MHz to 800 MHz by adjusting the band changeover switch 15 and the tuning voltage.
The reception frequency between the F bands can be converted into the first IF signal, and this frequency range is the usable frequency band of the device.

FIG. 2 shows an example of a schematic circuit configuration diagram of a tuner pack. Tuner pack 11 shown in FIG.
Is an electronic tuning tuner that receives VHF and UHF band frequencies by varying a tuning voltage applied to a variable capacitance diode (not shown). This electronic tuning tuner includes an antenna (ANT) tuning circuit 11.
1, FET 112, RF tuning circuit 113, local oscillator 1
14, a mixer 115, and an IF tuning circuit 116.

The ANT tuning circuit 111 includes a first
A first variable capacitance diode having a coil and a first variable capacitance diode, wherein a capacitance of the first variable capacitance diode changes according to a tuning voltage applied to the first variable capacitance diode via a resistor R1; 8MHz RF input signal with tuning frequency determined by the capacitance of
Receive in bandwidth.

The FET 112 amplifies the RF input signal from the ANT tuning circuit 111 input to the first gate G1 and outputs the amplified signal from the drain D to the RF tuning circuit 113. FET
An AGC voltage is input from an AGC (automatic gain control) terminal 17 to the second gate G2 of 112, and the gain of the FET 112 changes according to the value of the AGC voltage.

The RF tuning circuit 113 has a second coil and a second variable capacitance diode (not shown).
And the capacitance of the second variable capacitance diode changes according to the tuning voltage applied to the second variable capacitance diode via the resistor R2.
An RF input signal having a tuning frequency determined by the coil and the capacitance of the second variable capacitance diode is received with an 8 MHz bandwidth.

The local oscillator 114 has a third coil and a third variable capacitance diode (not shown), and the capacitance of the third variable capacitance diode is changed according to the tuning voltage applied to the third variable capacitance diode via the resistor R3. It changes and oscillates a local oscillation signal having an oscillation frequency determined by the capacitance of the third coil and the third variable capacitance diode. In the case of the upper heterodyne system, this oscillation frequency is a frequency higher by a first IF frequency than the reception frequency of the RF input signal.

The mixer 115 mixes the RF input signal from the RF tuning circuit 113 and the local oscillation signal from the local oscillator 114 to generate various signals. IF tuning circuit 11
6 extracts the first IF signal having the first IF frequency from various signals output from the mixer 115.

As shown in FIG. 3, the first IF filter 13 is a 50 MHz low-pass filter 131, 40 to 4
It is composed of an 8 MHz band pass filter 132 and a 44 MHz notch filter 133, and performs band processing with a bandwidth of 8 MHz in a 44 MHz band. 1st IF filter 1
The insertion loss of No. 3 is about 20 dB.

The 50 MHz low-pass filter 131 is
The cut-off frequency is 50 MHz, and a frequency of 50 MHz or less is passed, and the image frequency at the time of frequency conversion of the first IF signal to the second IF signal is removed. The image frequency is (VCO2
(2 oscillation frequency + second IF frequency).

40-48 MHz bandpass filter 1
32 passes only the first IF frequency (display frequency band) of 40 to 48 MHz and removes frequency components other than the display frequency band. 44MHz notch filter 133
When the tuner pack 11 converts the RF input signal into the first IF signal, the frequency characteristic deviation of about 6 dB is corrected to be flat within the 8 MHz bandwidth.

The first IF amplifier 14 (for example, model name: UP
C1656C) is the first signal from the first IF filter 13.
The IF signal is amplified by about 20 dB to an appropriate input level of a DBM (Double Balanced Mixer) 21.

The tuner pack 11 has an AGC terminal 17
The AGC terminal 17 is connected to a variable resistor (volume) 16 to which +12 V is applied.
The variable resistor 16 can change the resistance value manually, and the changed voltage is applied to the FET via the AGC terminal 17.
By being applied to the second gate G2 of 112, the FET1
Twelve gains are adjusted.

For this reason, the DC voltage applied to the AGC terminal 17 of the tuner pack 11 is adjusted by the variable resistor 16 so that the reference input level can be varied according to the level of the interference wave when detecting the radio wave interference. The gain of the tuner pack 11 can be adjusted. For example, when the level of the interference wave is weak, the DC voltage applied to the AGC terminal 17 is reduced to increase the gain of the FET 112, thereby increasing the reference input level.

The total maximum gain of the tuner block 1 is, for example, +36 dB in the low band of VHF, VH
+ 41dB in the high band of F, + 36d in the UHF band
B, and the maximum output of the second IF frequency band is 110 dB.
μ.

Such a television (VHF, UH
F) The use of the tuner pack 11 in the band not only greatly simplifies the device, but also makes it possible to reduce the size, cost, and weight.

(B) VCO / DBM block The VCO / DBM block 2 is composed of a DBM 21 for frequency-converting a 44 MHz band first IF signal from the tuner block 1 into a 10.7 MHz second IF signal, and a VCO 22 as a local oscillator. Be composed.

The VCO 22 converts the first IF signal (40 to 48 MHz) to 10.7 MHz by the upper heterodyne method.
In order to convert the frequency to the second IF signal (second IF frequency), the second IF signal is 10.7 M higher than the second IF frequency.
A local oscillation signal of 50.7 to 58.7 MHz, which is a frequency higher by Hz, is generated by the oscillator.

DBM21 (for example, type name: MCL SB
L-1) mixes the first IF signal from the tuner block 1 with the local oscillation signal from the VCO 22,
The frequency of the signal is converted to a second IF signal of 10.7 MHz. The conversion loss of DBM 21 is about 6 dB.

The frequency to be converted is determined by the oscillation frequency of the VCO 22. The VCO 22 changes the oscillation frequency from 50.7 MHz to 58 by the sawtooth wave from the sawtooth generation block 5 input to the oscillation frequency control terminal 23. .7M
Hz to 8 MHz, and the DBM 21
The frequency in the 8 MHz band between 40 MHz and 48 MHz of the IF signal is converted into a 10.7 MHz second IF signal synchronized with the sawtooth wave. The sawtooth wave output from the sawtooth wave generation block 5 is applied to the X-axis of the CRT display 6.

(C) Second IF Block The second IF block 3 is a second IF filter 31 for extracting a second IF frequency component of 10.7 MHz from the signal from the VCO / DBM block 2, and a second IF signal from the second IF filter 31. IF amplifier 3 for amplifying
2.

The second IF filter 31 determines the resolution of the frequency displayed on the CRT display device 6, and the interference wave is close to the television video carrier frequency (fv) or the audio carrier frequency (fa). A narrow band ceramic filter having high sharpness and low insertion loss (for example, model name: SFE10.7
MTE, 3 dB bandwidth 68 kHz), and two stages of this narrow band ceramic filter are inserted. The second IF amplifier 32 amplifies to the appropriate input level of the logarithmic detection log amplifier IC 41 at the next stage. The total gain of the second IF block 3 is about +44 dB.

(D) Log detection block The log detection block 4 is a block from the second IF block 3.
Logarithmic compression and detection of the second IF signal of 0.7 MHz, a sequential detection log amplifier IC 41 for outputting a DC voltage corresponding to the input signal strength, a video low-pass filter 42 for limiting the signal band of the second IF signal after log detection, And a level shift / gain adjustment circuit 43 for adjusting the output signal of the video low-pass filter 42 to an appropriate amplitude on the Y-axis of the CRT display 6.

The sequential detection log amplifier IC 41 has an integrated circuit (IC) with a maximum input of 125 dBμV (75Ω termination value) and a log compression linear operation range of 91 dB.
(For example, AD8307AN). However, in this circuit, the available input range is from 45 dBμV to 120 dB due to the influence of random noise included in the input signal and the limitation of the maximum output of the second IF block 3 in the preceding stage.
75 dB up to BμV is a linear operation range.

The second IF signal that has been successively log-detected is CR
Band 1 for improving display waveform clarity of T display device 6
After removing the AC wave component by the 0 kHz video low-pass filter 42, the level shift / gain adjustment circuit 43
When the input signal is increased by 10 dB, the output signal becomes 0.
The signal amplified to the amplitude which increases by 5V is amplified by the CRT.
It is input to the Y axis of the display device 6.

By providing such a log detection block 4, it is possible to faithfully amplify the interference wave level on the display screen and display it on the display screen regardless of the level of the interference wave level. That is, in using the device, it is possible to secure a display range corresponding to a wide range of input so that a weak interference wave can be measured.

(E) Saw Wave Generation Block As shown in FIG. 4, the saw wave generation block 5 generates a saw wave, and outputs the saw wave to the X axis of the CRT display device 6 and the VCO 2.
Sawtooth oscillation circuit 5 applied to the oscillation frequency control terminal 23 of FIG.
1. Blanking voltage (Z-axis) generating circuit 52 for generating a blanking voltage for erasing the display of the CRT display device 6 during the falling period of the sawtooth wave, and sawtooth wave amplitude adjusting circuit for adjusting the amplitude of the sawtooth wave 53.

The sawtooth oscillating circuit 51 includes a charging circuit 151 for charging a capacitor with a constant current, a timer IC 152, and a discharging circuit 153 for discharging the electric charge stored in the capacitor by the timer IC 152 approximately every 100 ms.
, And a sawtooth wave having good linearity of rising is generated. The blanking voltage generation circuit 52 outputs a voltage of +5 V to the CRT display device 6 only during the falling period of the sawtooth wave in conjunction with the timing signal from the timer IC 152.

The sawtooth amplitude adjustment circuit 53 adjusts the amplitude (about 2 to 10 V) of the sawtooth wave applied to the oscillation frequency control terminal 23 of the VCO 22 so that the oscillation frequency of the VCO 22 becomes 50.7 MHz to 58.7 MHz. At the same time, the gain is adjusted so that the amplitude of the sawtooth wave applied to the X-axis of the CRT display device 6 becomes eight divisions on the screen. The cycle of the sawtooth oscillation circuit 51 can be changed from 80 ms to 300 ms from outside so that the display on the screen can be stably displayed in accordance with the generation cycle of the jamming radio wave.

(F) CRT display device The CRT display device 6 is a display device using a horizontal (X-axis) and vertical (Y-axis) drive system. A circuit 60 is provided, for example, a 3.5-inch CR manufactured by Meguro Denso Co., Ltd.
A T / CRT driving horizontal / vertical amplifier circuit is used.

The CRT display device 6 has a Z-axis (blanking voltage input) for temporarily erasing the display. The display has been erased.

(G) Power supply device The power supply device 7 has ten single-cell batteries, and includes a tuner block 1, a VCO / DBM block 2, a second IF block 3, and a three-terminal stabilized power supply IC and a switching power supply. Voltage (+ 12V, + 30V, -12V) required for each of the log detection block 4 and the sawtooth generation block 5
Has been supplied. For example, by using 10 alkaline AA batteries, the device can be operated continuously for about 6 hours.

The tuner pack 11 uses a PLL (Phase Locked) for local oscillation frequency control for channel selection.
Loop) Built-in frequency synthesizer IC. A one-chip microcomputer (one-chip microcomputer) interlocking the Samir switch 10 with channel setting serial data for setting the frequency division ratio of the PLL circuit using a Samir switch 10 for specifying a measurement channel for channel selection.
8 to the tuner pack 11.

Since the characteristic of the tuning voltage versus the first local oscillation frequency is not necessarily linear, the tuner pack 11 changes the current analog tuning to digital tuning to set the center frequency more quickly and accurately. can do.

A control voltage is generated by the one-chip microcomputer 8 and the D / A converter 9 so that the X-axis sawtooth voltage of the CRT display device 6 and the oscillation frequency of the VCO become linear. Improves accuracy. Thereby, the operability is improved, and the stability of the device can be increased.

Next, a method of detecting an interference source of an interference radio wave using the single-channel spectrum analyzer for radio wave interference detection according to the embodiment configured as described above will be described.

(A) First, the case where a dedicated measuring vehicle is owned (for example, NHK, Telecommunications Control Bureau, etc.) will be described. The measuring vehicle is equipped with a telescopic pole for installing a receiving antenna, and the telescopic pole has a telescopic variable range of 2.5 m to 10 m above ground.

The interfering radio wave received by the directional receiving antenna is input to a spectrum analyzer for radio wave interference detection installed in the measurement vehicle, and the interfering radio wave is displayed on the screen of the CRT display device 6. The maximum direction of arrival of the jammer is detected at several points, and the source of the jammer is identified from the intersection of the maximum directions of arrival.

Here, a specific example of the booster oscillation fault investigation will be described with reference to the flowchart of FIG. 5 and the drawing of FIG. Interference of a mesh pattern or a Kikusui pattern may occur continuously only in a specific channel. This is often caused by abnormal oscillation of the home booster. Here, as shown in FIG. 6, it is assumed that the disturbance source is at point P, and the disturbance source is detected at each of points A, B, and C. SA is a spectrum analyzer.

First, it is assumed that a beat symptom has occurred in, for example, 2ch (channel) due to the interference of booster oscillation (step S11). Next, a directional receiving antenna and a spectrum analyzer are connected by a 75Ω coaxial cable. Then, in the obstacle area (for example, point A) of the interference wave caused by the booster oscillation, the reception antenna is extended from the measurement vehicle to receive the interference wave (step S13). Then, the received interference wave is input to the spectrum analyzer in the vehicle, and the center frequency is set to the 2ch band, the display frequency bandwidth, the resolution bandwidth, and the reference input level are set to such an extent that the interference wave can be easily identified (step S15).

In this case, the tuning voltage is adjusted in the tuner block 1 to adjust the 2ch band (bandwidth 8M).
Hz), converts the 2ch band into a first IF signal,
In the CO / DBM block 2 and the second IF block 3, the first IF signal is converted to the second IF signal (bandwidth 68 kHz).
The log detection block 4 logarithmically compresses and detects the second IF signal, limits the signal band of the second IF signal after log detection, and outputs the result to the Y-axis of the CRT display device 6. Thereby, one channel band of 2ch is displayed on the screen.

Further, the maximum arrival direction of the interference wave level at the point where the receiving antenna is extended is checked (step S1).
7). For example, the maximum arrival direction of the interference wave level at the point A is the direction H1. And, according to the strength of the jammer,
The investigation point is moved in the maximum direction of arrival of the interference wave, and the operations from step S13 to step S17 are repeated several times (step S19).

For example, the measuring vehicle is moved to the point B, and the maximum arrival direction of the interference wave level at the point B is the direction H2. Further, the measuring vehicle is moved to the point C, and the point C
The maximum direction of arrival of the disturbance wave level at is H3.
Thereby, the intersection connecting the extended lines of the maximum arrival directions H1, H2, and H3 becomes the point P of the disturbance source (step S21).

As described above, by using the spectrum arranizer of the embodiment, it is possible to directly confirm the presence of an interference signal entering the band of the channel being received, and to easily detect the interference source. Can be.

(B) Next, a case where a dedicated measuring vehicle is not owned (for example, a general electric appliance store, a power company, etc.) will be described. In this case, a spectrum analyzer and a small receiving antenna having directivity are carried, and the interference source is specified while detecting the maximum direction of arrival of the interference wave. When carrying the spectrum analyzer, use the attached battery pack. Usually, the continuous operation time of the attached battery pack is about 2 hours.

According to the single-channel spectrum analyzer for radio wave detection configured as described above, an arbitrary one-channel band affected by interference can be displayed on the screen of the spectrum analyzer. Can be detected.

In the first IF converter, a television tuner pack 11 is used instead of the special oscillator of the conventional spectrum analyzer or the first to fourth IF converters, and the measurement frequencies are VHF and UH.
The display frequency bandwidth is limited to an arbitrary one-channel television bandwidth (8 MHz) by using the F band and the tuning function of the tuner pack 11. In other words, the function of the spectrum analyzer is limited to a single-channel display in the TV band for detecting radio interference, so the circuit configuration of the device itself can be greatly simplified, and the size, weight, and price can be reduced. it can. In this case, in the embodiment,
The circuit configuration can be reduced to about half or less of the conventional circuit configuration.

Further, by simplifying the circuit configuration, the number of operation knobs is reduced to less than half that of the conventional type, so that operability can be improved. Further, by simplifying the circuit configuration, the power consumption is greatly reduced, and is about one third of the conventional power consumption. Therefore, the continuous operation time has been reduced from about 2 hours to about 6 hours. Furthermore, by setting the receiving band to a narrow band of 8 MHz, the sensitivity of the interference wave measurement is greatly improved, the level can be improved by about 20 dBμ compared with the conventional type, and the internal noise level can be suppressed to about 0 dBμ (1 μV). it can.
The price has been reduced to less than half of the conventional price due to the greatly simplified circuit configuration.

Further, the conventional spectrum analyzer uses the first frequency band higher than the frequency of the RF input signal.
Although the IF frequency is set as the IF frequency, the present apparatus sets the frequency band (44 MHz band) lower than the frequency of the RF input signal to the first IF.
Frequency. The value of the first IF frequency does not necessarily need to be set in the 2 to 4 GHz band which is not affected by the image interference, and the image interference component can be suppressed by the ANT tuning circuit and the RF tuning circuit. Further, by inserting a 50 MHz low-pass filter 131 into the first IF output as a measure against the second IF image interference, the image interference component can be removed.

Further, by using the tuner pack 11, the displayable band is fixed at 8 MHz, but the required sweep time, resolution filter, and video low-pass filter performance can also be limited (for detecting radio interference). As a result, it is possible to greatly simplify the entire device, and reduce the size, weight, and cost. Since this device is a device that can be owned by a general electronics store or the like, it can be a small and lightweight device that is easy to operate, low in price, and suitable for portable research, even if its functions are greatly limited.

In the case of a conventional general spectrum analyzer, an expensive and special oscillator (for example, a YIG oscillator) is required. However, the double conversion method employed in the spectrum analyzer for detecting electromagnetic interference according to the embodiment is Since the center frequency to be displayed is determined by the tuning function of the tuner pack 11, the second local oscillation frequency is variable, and the variable range can be fixed to a narrow frequency bandwidth (8 MHz). Available and inexpensive. Also, if the first IF frequency is VH
For the F band, general-purpose products can be used. Although the display frequency bandwidth in this case is limited to 8 MHz, it can be used for detecting an interference source, and the cost merit is extremely large.

It should be noted that the present invention is not limited to the single-channel spectrum analyzer for detecting radio interference according to the embodiment, and that various modifications can be made without departing from the technical idea of the present invention. Of course.

[0082]

According to the single channel spectrum analyzer of the first aspect of the present invention, the measurement frequency is set to VHF, UH
Since the display frequency bandwidth is limited to a bandwidth equivalent to one channel of the television broadcast wave by the tuning function of the F band and the channel selection means, the display is limited to the single channel display of the television broadcast wave band. The configuration can be greatly simplified, downsizing, cost reduction, power saving, simplicity of operation can be achieved, and radio interference detection can be performed reliably and easily. In addition, since the reception band is narrow, the internal noise intensity can be kept low.

According to the single channel spectrum analyzer of the second aspect of the present invention, since the center frequency of the first intermediate frequency signal is 44 MHz and the frequency of the second intermediate frequency signal is 10.7 MHz, a simpler configuration can be achieved. Thus, image interference components and the like can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration block diagram of a single-channel spectrum analyzer for detecting radio interference according to an embodiment.

FIG. 2 is an example of a schematic circuit configuration diagram of a tuner pack.

FIG. 3 is a configuration block diagram of a first IF filter.

FIG. 4 is a configuration block diagram of a sawtooth wave generation block.

FIG. 5 is a flowchart illustrating a method of detecting an interference source of an interference radio wave using a single-channel spectrum analyzer for radio interference detection.

FIG. 6 is a diagram illustrating a method of detecting a maximum direction of arrival of an interference wave at several points to specify an interference source.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tuner block 2 VCO / DBM block 3 2nd IF block 4 Log detection block 5 Saw wave generation block 6 CRT display device 7 Power supply device 11 Tuner pack 12 Tuning voltage generation circuit 13 1st IF filter 14 1st IF amplifier 15 Band changeover switch 16 Variable Resistor 17 AGC terminal 21 DBM 22 VCO 31 Second IF filter 32 Second IF amplifier 41 Successive detection log amplifier IC 42 Video low-pass filter 43 Level shift / gain adjustment circuit

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masatoshi Furuyama 3-8 Kanemmachi-cho, Kushiro-shi, Hokkaido F-term in the Japan Broadcasting Corporation Kushiro Broadcasting Station 5C061 BB03 CC05 5K020 AA07 BB09 DD11 DD13 DD27 FF01 FF04 HH13 NN01 NN02

Claims (2)

[Claims] 1. A channel selecting means for selecting a channel by limiting a high frequency input signal in a VHF and UHF band to a bandwidth corresponding to one channel of a television broadcasting wave, and said television broadcasting wave selected by said channel selecting means. A first intermediate frequency converting means for converting a high frequency input signal corresponding to a bandwidth of one channel into a first intermediate frequency signal of the same bandwidth by a local oscillation frequency signal of an upper heterodyne system; A second intermediate frequency conversion means for converting into a second intermediate frequency signal by a sweep signal of a local oscillation frequency of an upper heterodyne system having a sweep width equivalent to the bandwidth of a television channel; and a second intermediate frequency conversion means. A band limiting means for limiting a signal bandwidth; a detecting means for detecting a signal obtained by the band limiting means; and a signal obtained by the detecting means. Single channel spectrum analyzer, characterized in that it comprises display means for the. 2. The single channel spectrum analyzer according to claim 1, wherein a center frequency of the first intermediate frequency signal is 44 MHz, and a frequency of the second intermediate frequency signal is 10.7 MHz.