JP2003143626A - Monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitor that can effectively be used for automatic monitoring a digital transmitter (in general, a transmitter to be monitored) which power-amplifies an OFDM signal and transmits the amplified signal in the case of digital broadcasting by the OFDM signal. SOLUTION: The monitor is configured such that a signal (TS1) resulting from demodulating an input signal to the transmitter to be monitored is used for a reference signal, comparing a signal (TS2) resulting from demodulating an output signal of the transmitter to be monitored with the signal (TS1) resulting from a demodulating the reference input signal to the transmitter to be monitored in the unit of bits calculates a bit error rate (BER), and when the calculated bit error rate exceeds a predetermined value, the monitor outputs a warning signal of the transmitter to be monitored.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor device, and more particularly to an OFDM (Orthogonal Frequency Division)
The present invention relates to a monitor device that monitors the state of a monitored device when a digital signal such as a multiplexing signal is input to the monitored device, and necessary signal processing such as power amplification is performed on the monitored device and output.

[0002]

2. Description of the Related Art First, an automatic monitor of a television transmitter of an analog signal which is currently being performed will be described. Figure 8
The system of the automatic monitor of the television transmitter of the analog signal currently performed is shown. In FIG. 8, the working transmitter 1
When the AM detection and the synchronization signal detector 102 detects that the output of 01 is below a predetermined level in spite of the presence of the synchronization signal, it is determined that the working transmitter 101 has an abnormality, and the transmission antenna The transmitter that supplies power to 103 is switched to the standby transmitter 105 by the switch 104. On the other hand, the output of the standby transmitter 105 is also checked by the AM detection and synchronization signal detector 106 for the level and the presence or absence of the synchronization signal.

Since the conventional automatic monitor is applied to analog broadcasting, as described above, the transmitter output signal is supplied to the AM detection and synchronization signal detector 102, and the detector outputs the transmitter output signal. The purpose as a monitor has been achieved as long as it can be confirmed that the output has dropped below a predetermined level despite the presence of a synchronization signal.

[0004]

However, when broadcasting is performed by using a digital wave such as an OFDM signal, the level of the output signal of the transmitter and the presence / absence of a synchronization signal are simply used as in the case of analog broadcasting. It is not possible to switch between the active and standby transmitters by detecting only the detected output.

An object of the present invention is to effectively monitor a digital transmitter (generally, a monitored device) used for automatic monitoring of a digital transmitter that power-amplifies and transmits the OFDM signal when performing digital broadcasting by using the OFDM signal. To provide a device.

[0006]

In order to achieve the above-mentioned object, the monitor device of the present invention has a B
Based on the fact that there is a so-called Cliff Effect phenomenon in which ER (Bit Error Rate) cannot be received at all when it exceeds a certain value, the input of the monitored device and the output of the monitored device are By comparing, the BER is calculated from the comparison result, and the operating state of the monitored device is monitored.

That is, the monitor device of the present invention is a monitor device for monitoring the state of a monitored device, wherein an input signal to the monitored device is demodulated, and the output from the monitored device is based on the demodulated signal. A signal obtained by demodulating the signals is compared bit by bit to calculate a bit error rate, and when the calculated bit error rate exceeds a predetermined value, an alarm signal and / or a bit error rate indicating signal about the bit error rate. It is characterized in that it is configured to output.

Further, the monitor device of the present invention is constructed such that, when the level of the output signal of the monitored device falls below a predetermined value, the monitor device outputs a signal notifying that the level has dropped. , Is provided with a logical product circuit for taking a logical product of the signal output by the configuration and the alarm signal for the bit error rate.

In the monitoring device of the present invention, a signal obtained by demodulating an input signal to the monitored device and a signal obtained by demodulating an output signal from the monitored device are the input signal to the monitored device and the monitored device. It is characterized in that it is a signal demodulated after adding common noise to the output signal from the device.

Further, the monitor device of the present invention is a monitor device for monitoring the state of a monitored device, wherein an output signal from the monitored device is demodulated to perform error correction, and the error-corrected signal is used as a reference. A signal obtained by demodulating an output signal from the monitored device is compared bit by bit to calculate a bit error rate, and when the calculated bit error rate exceeds a predetermined value, an alarm signal for the bit error rate and And / or is configured to output a bit error rate indicating signal.

Further, the monitor device of the present invention is characterized in that the signal obtained by demodulating the output signal from the monitored device is a Viterbi decoded signal and the error correction is an RS error correction.

Further, the monitor device of the present invention comprises means for switching the output signal of the monitored device to the input signal of the monitored device, and is obtained for the input signal of the monitored device switched by the switching means. With the comparison result,
By comparing the comparison result obtained for the output signal of the monitored device switched by the switching unit, the equivalent C / N deterioration amount generated in the monitored device is monitored. It is a feature.

The monitor device of the present invention is the monitor device according to claim 4 or 5, wherein the output signal of the monitored device is replaced with the input signal of the monitored device and the comparison result obtained by using the monitor device. By comparing the comparison result obtained by using the monitor device according to claim 4 or 5 as it is, the equivalent C / N deterioration amount generated in the monitored device is monitored. It is a feature.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments of the invention with reference to the accompanying drawings. In addition,
In the following, when performing digital broadcasting using an OFDM signal, it is determined whether or not there is an abnormality in the intermediate frequency (IF) amplification unit or power amplification unit of the transmitter, and if it is determined that there is abnormality, switching from the active unit to the standby unit is performed. An automatic monitoring device that sounds an alarm will be described as an embodiment of the present invention. Therefore, in the following embodiments, the monitored device by the monitoring device of the present invention is the above-mentioned intermediate frequency (IF) amplifying section and power amplifying section, which are generally supplied with a digital signal and required signal processing. Any output may be used as long as it is subjected to the output.

FIG. 1 shows a first embodiment of the monitor device of the present invention. The present embodiment is a case where the monitor device of the present invention is configured as a monitor device that determines the state of an intermediate frequency (IF) amplification unit (monitored device) of a digital broadcast transmitter. In FIG. 1, reference numeral 1 is a terrestrial digital broadcast receiver, and 2
Is a BER (bit error rate) calculator, 3 is a delay circuit, 4 is a terrestrial digital broadcast receiver, 5 is a relay, and 6 is BE.
The R display section.

The operation will be described. An output signal (IF signal) of a monitored device (not shown) is supplied as a measurement signal to the terrestrial digital broadcast reception unit 1 to be demodulated, and TS1 (Transport Stream 1) which is a baseband bit stream.
The signal is taken out and applied to one input terminal of the BER calculation unit 2. In addition, the input signal (IF signal) of the monitored device is used as a reference signal through a delay circuit 3 which gives a time delay corresponding to the signal processing time of the monitored device, and after delaying the signal, it is supplied to the terrestrial digital broadcast receiving unit 4. It is demodulated and TS2 (Transport Stream) is a baseband bit stream.
2) The signal is taken out and applied to the other input terminal of the BER calculator 2.

The BER calculator 2 compares the two applied TS signals bit by bit. Then, the BER of the TS1 signal is calculated with reference to the bits of the TS2 signal supplied from the terrestrial digital broadcast receiving unit 4. When the BER exceeds a predetermined value as a result of the measurement, a control signal for switching the monitored device from the active device to the standby device is output, and the relay 5 is operated to sound an alarm. Further, the BER value detected by the BER calculation unit 2 is displayed on the BER display unit 6. The BER calculation unit 2
Is configured to include an error counter. The delay circuit 3
Is a memory that gives a fixed delay in advance so that the two signals input to the BER calculation unit 2 match on a bit-by-bit basis. With such a configuration, it is possible to always grasp the deterioration state of the monitored device.

FIG. 2 shows a second embodiment of the monitor device of the present invention. The present embodiment is also a case where the monitor device of the present invention is configured as a monitor device that determines the state of the IF amplification unit (monitored device) of a digital broadcast transmitter. However, the output signal (IF signal) of the monitored device is a signal. By also monitoring the level, the deterioration state of the monitored device can be grasped more reliably than in the case of FIG.

In the present embodiment (second embodiment), in addition to the configuration shown in the first embodiment (FIG. 1), the signal level of the output signal (IF signal) of the monitored device is also monitored. In addition, when the output signal of the monitored device is detected and the value is below a predetermined value, a detection smoothing unit 7 that outputs a control signal, and an output of this detection smoothing unit 7 and an output of the BER comparison unit 2 A that forms the control signal by taking the logical product of
And an ND circuit 8. The circuit configuration other than the detection smoothing unit 7 and the AND circuit 8 is exactly the same as that in the case of FIG. 1, so refer to the description of FIG.

FIG. 3 shows a third embodiment of the monitor device of the present invention. The present embodiment is also a case where the monitor device of the present invention is configured as a monitor device for determining the state of the IF amplification section (monitored device) of the digital broadcast transmitter.
As shown in, the noise signals generated by the noise signal generating unit 9 are added to the outputs of the terrestrial digital broadcasting receiving unit 1 and the terrestrial digital broadcasting receiving unit 4 applied to the BER calculating unit 2 by the adders 10, 11 respectively. Therefore, each is added.

In the present embodiment (third embodiment), noise is added to both TS signals applied to the BER calculating section 2 to intentionally increase the number of errors, thereby shortening the BER measurement time.

In the first to third embodiments described above, the OFD supplied to the digital broadcast receiving units 1 and 4 is used.
The M signal assumes the IF band (37 MHz band), but R
Of course, the F band (UHF band) is also possible. For example, when the OFDM signal as the measurement signal is in the RF band and the OFDM signal as the reference signal is in the IF band, a down converter (D / C) is arranged on the input side of the terrestrial digital broadcast receiving unit 1 to perform the RF The band signal can be converted to an IF band signal and then supplied to the digital broadcast receiving unit 1, or any other suitable method can be used.

FIG. 4 shows a fourth embodiment of the monitor device of the present invention. In the present embodiment, as described above, the measurement signal (OFDM signal) is in the RF band, and the reference signal (OFDM signal) is
This is an embodiment in the case where the signal) is in the IF band, and in particular, is a case where the monitor device of the present invention is applied to a transmitter of digital broadcasting (hereinafter, simply referred to as a digital transmitter). In FIG. 4, 12 is a digital transmitter, 13 is an exciter, 14 is a power amplifier (P / A), 15 is a bandpass filter, 16
Is a down converter (D / C), and 17 is a monitor device of the present invention.

The operation will be described. In FIG. 4, an IF band OFDM signal is supplied to the digital transmitter 12. This signal is frequency-converted from the IF signal to the RF signal by the exciter 13, is amplified, and is sent to the power amplifier (P / A) 14 at the next stage to reach a predetermined power level.
The RF signal of the predetermined power level is passed through the band pass filter 15
Via a transmission antenna (not shown).

In the present embodiment (fourth embodiment), the monitored device is the digital transmitter 12, the input signal of which is the IF signal and the output signal of which is the RF signal. Therefore, the measurement signal (RF signal) is electromagnetically coupled to the power supply line from the digital transmitter 12 to the transmission antenna (not shown).
Is taken out, the taken out signal is converted into an IF signal by the down converter (D / C) 16, and this is supplied to the monitor device 17 of the present invention as a measurement signal. Here, as the monitor device 17 of the present invention, for example, the monitor device shown in FIG. 1 can be used.

FIG. 5 shows a fifth embodiment of the monitor device of the present invention. In this embodiment, in the monitor device of the present invention shown in the first to fourth embodiments described above, the transmitter of the transmitter can be used without using the reference signal (input signal of the transmitter) required in any of the monitor devices. It is made possible to monitor. The monitor device according to the fifth embodiment is configured so that the transmitter can be monitored based on a broadcast wave signal (on-air signal).

In FIG. 5, 18 is a digital broadcast receiving unit (RS decoding output), 19 is a digital broadcasting receiving unit (Viterbi decoding output), 20 is a BER calculation unit, 21 is an error counter, and 22 is a BER display unit. .

The operation will be described. In this embodiment, the RS (Reed Solomon) is provided in the digital broadcast receiving unit 18.
The decoded output after error correction can be brought into a state with almost no error (constant value) if the BER is about 2 × 10 ⁻⁴ or more. It can be regarded as an input signal of the monitoring device), while the Viterbi decoded output, which is a signal before RS error correction is performed, represents the state of the received measurement signal as it is. Similar to the above embodiments, the present invention is configured based on the fact that it can be used as a measurement signal supplied to the monitoring device of the present invention (that is, an output signal of a monitored device).

In FIG. 5, a broadcast wave signal which is an input signal is supplied to a digital broadcast receiving section (RS decoding output) 18 and a digital broadcast receiving section (Viterbi decoding output) 19. TS2 and TS1 extracted from the digital broadcast receiving unit 18 and the digital broadcast receiving unit 19 are applied to the respective input terminals of the BER calculating unit 20. Since the digital broadcast receiver 19 does not have an error correction circuit, the signal on the comparison side has less delay than the signal on the reference side. Therefore, a delay circuit (memory) is inserted on the comparison side of the input of the calculation unit of the BER in order to match the time timing of both signals.

The BER calculating unit 20 is the same as the BER calculating unit 2 shown in FIGS. 1 to 3. In FIGS. 1 to 3, the error counter is built in the BER calculating unit 2. Is configured as shown in FIG.
Further, in FIG. 5, two systems of the digital broadcast receiving unit are prepared, but this is configured by one system up to the Viterbi decoding output and shared, and the output of the shared portion is branched into two, one of which is the reference side,
The other side may be the measurement side (RS error correction circuit input).
In FIG. 5, the comparison output obtained from the BER calculation unit 20 is supplied to the error counter 21 and the bit error is counted. In addition, the BER display unit 22 is displayed as B in FIG.
It corresponds to the ER display unit 6. Although Viterbi decoding is used for OFDM signal demodulation and RS error correction is performed for subsequent error correction in the present embodiment, the decoding method and the error correction are not limited to these, and other methods may be used. May be

FIG. 6 shows a sixth embodiment of the monitor device of the present invention. This embodiment is intended to monitor the equivalent deterioration of C / N of a monitored device by using the monitoring device of the fifth embodiment of the present invention shown in FIG.

That is, in FIG. 5, the input signal of the monitor device is a broadcast wave signal (on-air signal). On the other hand, in the present embodiment (sixth embodiment), the input signal and the output signal (on-air signal) of the monitored device 23 are switched by the changeover switch SW to have the same configuration as the monitor device of the present invention shown in FIG. By supplying the monitoring device 24 with the BER on the input side and then the BER on the output side, the monitored device 2 can be compared based on the comparison between the two.
Equivalent C / N degradation of 3 can be monitored.

FIG. 7 shows a seventh embodiment of the monitor device of the present invention. This embodiment is also intended to monitor the equivalent deterioration of C / N of the monitored device by using the monitoring device of the fifth embodiment of the present invention shown in FIG.

The difference between this embodiment and the above-described sixth embodiment is that in the sixth embodiment, the input signal and the output signal of the monitored device 23 are switched by the changeover switch SW and supplied to the monitor device 24. In contrast to this (see FIG. 6), in the present embodiment, the input signal and the output signal of the monitored device 23 are supplied to the dedicated monitor devices 25 and 26, respectively.

The respective bit error count outputs from the monitor devices 25 and 26 are sent to the personal computer 27, and the monitored device 23 is controlled by performing a subtraction process between the both bit error count outputs (for example, working and standby). A control signal for switching is generated and output, and an alarm is sounded. Further, the personal computer 27 displays the equivalent C / N deterioration of the monitored device 23 on the display device 28.

[0036]

According to the present invention, it is possible to monitor the presence / absence of an abnormality in a digital transmitter using an operating OFDM signal, and it can be used as an automatic monitor for switching to a standby transmitter when an abnormality occurs. In addition, since the BER of the transmitter output can always be monitored in the monitor device of the present invention, it is also possible to immediately determine what state the transmitter is in.

Here, the deterioration of the frequency characteristics of the transmitter, the increase of the intermodulation amount, the decrease of the output, the phase noise (local oscillator), etc. are all finally detected as the deterioration of the BER, so that the BER is reliably monitored. The monitoring device of the present invention, which is capable of doing so, is very effective for monitoring an OFDM signal.

Further, according to the present invention, it is possible to keep track of how much margin is ensured for the transmitter in operation with respect to the value of BER that causes the cliff effect. It is very effective in securing a good broadcasting service.

Incidentally, conventionally, in order to measure the BER,
It was necessary to send a reference signal having no bit error to the measuring device on a separate line, or to insert a reference signal with a known bit pattern into the signal, but in the present invention, the input signal to the monitored device is required. Alternatively, since the output signal (for example, broadcast wave) can be used as the reference signal, it is effective in simplifying and reducing the cost of the monitor device.

[Brief description of drawings]

FIG. 1 shows a first embodiment of a monitor device of the present invention.

FIG. 2 shows a second embodiment of the monitor device of the present invention.

FIG. 3 shows a third embodiment of the monitor device of the present invention.

FIG. 4 shows a fourth embodiment of the monitor device of the present invention.

FIG. 5 shows a fifth embodiment of the monitor device of the present invention.

FIG. 6 shows a sixth embodiment of the monitor device of the present invention.

FIG. 7 shows a seventh embodiment of the monitor device of the present invention.

FIG. 8 shows a system of automatic monitoring of a television transmitter of an analog signal which is currently performed.

[Explanation of symbols]

1 Digital Terrestrial Broadcasting Receiver 2 BER calculator 3 delay circuit 4 Digital Terrestrial Broadcasting Receiver 5 relays 6 BER display 7 Detection smoothing section 8 AND circuit 9 Noise signal generator 10,11 adder 12 Digital transmitter 13 exciter 14 Power amplifier (P / A) 15 band pass filter 16 Down converter (D / C) 17 Monitor device of the present invention 18 Digital broadcasting receiver (RS decoding output) 19 Digital broadcasting receiver (Viterbi decoding output) 20 BER calculator 21 Error counter 22 BER display 23 Monitored equipment 24 Monitor device 25,26 Dedicated monitor device 27 PC 28 Display SW switch

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04L 1/00 H04L 1/00 AF term (reference) 5C061 BB09 BB13 CC01 5C087 AA02 AA03 AA24 AA25 BB03 BB11 BB18 BB32 BB62 BB74 DD08 DD20 EE14 FF01 FF02 FF04 FF17 FF19 FF20 FF22 GG02 GG08 GG09 GG19 GG23 GG31 GG66 GG67 GG70 GG71 5K014 AA01 BA08 BA11 FA09 GA02 HA05 HA10 5K022 DD01 DD31

Claims (7)

[Claims] 1. A monitor device for monitoring a state of a monitored device, wherein a signal obtained by demodulating an input signal to the monitored device and demodulating an output signal from the monitored device with the demodulated signal as a reference is used. The bit error rate is calculated by comparing in bit units, and when the calculated bit error rate exceeds a predetermined value, an alarm signal and / or a bit error rate indicating signal about the bit error rate is output. A monitor device characterized by the above. 2. The monitor device according to claim 1, wherein when the level of the output signal of the monitored device falls below a predetermined value, the monitor device outputs a signal notifying that the level has dropped. A monitor apparatus comprising: a logical product circuit configured to perform a logical product of a signal output by the structure and an alarm signal for the bit error rate. 3. The monitor device according to claim 1, wherein a signal obtained by demodulating an input signal to the monitored device and a signal obtained by demodulating an output signal from the monitored device are input to the monitored device. A monitor device which is a signal obtained by adding common noise to a signal and an output signal from the monitored device and then demodulating the signal. 4. A monitor device for monitoring the state of a monitored device, wherein an output signal from the monitored device is demodulated to perform error correction, and the error-corrected signal is used as a reference from the monitored device. A signal obtained by demodulating an output signal is compared bit by bit to calculate a bit error rate, and when the calculated bit error rate exceeds a predetermined value, an alarm signal and / or a bit error rate display about the bit error rate A monitor device configured to output a signal. 5. The monitor device according to claim 4, wherein the signal obtained by demodulating the output signal from the monitored device is a Viterbi decoded signal, and the error correction is RS error correction. 6. The monitor device according to claim 4, further comprising means for switching an output signal of the monitored device to an input signal of the monitored device, and the input of the monitored device switched by the switching means. By comparing the comparison result obtained for the signal and the comparison result obtained for the output signal of the monitored device switched by the switching means, equivalent C / N deterioration occurring in the monitored device A monitor device characterized in that the amount is monitored. 7. A comparison result obtained by using a monitor device in which the output signal of the monitored device in the monitor device according to claim 4 or 5 is replaced with an input signal of the monitored device, and the comparison result according to claim 4 or 5. A monitor device, wherein the equivalent C / N deterioration amount occurring in the monitored device is monitored by comparing with a comparison result obtained by using the monitor device described in 5 as it is.