JPH03222581A - Ghost elimination system - Google Patents

Abstract

PURPOSE:To attain ghost countermeasure effective to a satellite station or the like by providing a UHF television repeater and a ghost elimination device connecting to the repeater and eliminating a ghost wave based on a reception waveform of a ghost elimination reference signal. CONSTITUTION:The ghost elimination system is provided with a repeater 2, in which a UHF television signal is received and converted into an intermediate frequency signal, which is subject to equalizing processing and the result is converted into a UHF television signal of a prescribed channel again, and a ghost elimination device 3 connecting to the repeater 2 and eliminating a ghost wave superimposed on a desired wave based on the reception waveform of a ghost elimination reference signal. Then a ghost wave superimposed on the UHF television signal is eliminated by the ghost elimination circuit 3 placed between a band pass filter 8 and an equalizer 9. Thus, a UHF television signal relayed by an existing satellite station is supplied to a reception user without ghost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a ghost removal system suitable for television radio relay stations, CATV stations, television public listening equipment, and the like.

[Prior art] Satellite stations that relay television waves sent from a central broadcasting station to remote locations are usually installed on mountain tops with good visibility, but these stations are not affected much by weather conditions. This is also to eliminate as much as possible the effects of ghosts caused by radio waves reflecting off obstacles such as buildings and steel towers. However, the pace of urbanization has been remarkable in recent years, and even in local cities where no sources of ghost interference were once found, the number of areas where buildings that cause ghost interference to satellite stations are becoming conspicuous is rapidly increasing. Satellite stations, which relay radio waves for a fee to those who wish to receive them, are forced to decide whether to move their radio towers to find a location with better reception conditions in order to avoid complaints from viewers. Issues have also been raised.

[Problem to be solved by the invention] The above-mentioned conventional radio wave relay station is concerned with the ghost problem, which is becoming more serious year by year with the progress of urbanization. Although it is possible to temporarily avoid the effects of ghosts by taking countermeasures such as doing so, it is only a matter of time before we are plagued by ghosts again, so countermeasures against ghosts by relocating radio towers are a drastic solution. I was faced with a problem that could not be achieved. In other words, if you choose a permanent ghost countermeasure, you should change your mindset and think about how to remove the ghosts that have occurred, rather than focusing on eliminating the cause of the ghosts themselves. There was a need to recognize the value of thinking about how to construct a removal system.

However, conventional ghost removal systems do not support television signals that are transmitted by superimposing a ghost removal reference signal on the television signal that starts with EDTV broadcasting, and simply differentiate the leading edge of the vertical synchronization signal. This generates a reference pulse, and from this reference pulse 27.32μ
Since this method extracts information on the delay time, amplitude, and phase of the ghost wave superimposed on the desired wave from the step-like ghost pulses existing between This method had problems such as not being able to see much difference in effectiveness compared to methods that increase directivity.

In addition to these radio wave relay stations, for example, when installing public antennas in large-scale housing complexes such as buildings and condominiums, or relay stations that send clear images to a large number of viewers, such as CATV stations. However, the introduction of a ghost removal system was avoided due to the accuracy of ghost removal and cost constraints.

[Means for Solving the Problems] The present invention solves the above problems, and includes a method of receiving a UHF television signal on which a ghost removal reference signal is superimposed during a vertical retrace period, and converting it into a constant intermediate frequency signal. a relay device that performs equalization processing and converts it back into a UHF television signal of a predetermined channel and transmits it; and a ghost removal device that is connected to this relay device and removes ghost waves based on the received waveform of the ghost removal reference signal. The device is characterized by comprising a tuner circuit that tunes and tunes a VHF television signal on which a ghost removal reference signal is superimposed during the vertical retrace period, and a tuner circuit that acts on the tuning output of this tuner circuit to remove the ghost. A ghost removal device that removes ghost waves based on the received waveform of a reference signal, and an RF that converts the video signal from which ghost waves have been removed by this ghost removal device into a VHF television signal of the same channel as the selected channel and outputs it. The present invention is characterized by comprising a modulator, and further includes a ghost removal reference signal superimposed on the vertical blanking period. The present invention is characterized in that it includes an RF modulator that converts the video signal from which ghost waves have been removed by the ghost removal device into a UHF television signal and outputs the signal.

1 Effect] This invention receives a UHF television signal on which a ghost removal reference signal is superimposed during the vertical blanking period, converts it into a constant intermediate frequency signal, performs equalization processing, and converts it back into a UHF television signal of a predetermined channel. When converted and transmitted, ghost waves are removed based on the received waveform of the ghost removal reference signal, thereby providing an effective ghost countermeasure for satellite stations and the like. In addition, the present invention tunes and selects a VHF television signal on which a ghost removal reference signal is superimposed during the vertical retrace period, removes ghost waves based on the received waveform of the ghost removal reference signal, and then tunes the VHF television signal to the same channel as the selected channel. By outputting the channel's VHF television signal instead, effective ghost countermeasures are provided for CATV stations and the like where the receiving channel and retransmission channel are the same.

Furthermore, the present invention operates on a VHF television signal in which a ghost removal reference signal is superimposed on a vertical retrace period,
By removing ghost waves for a specific channel and converting the ghost wave-removed video signal into a UHF television signal and outputting it, ghost countermeasures suitable for public listening systems in buildings and condominiums, etc. are provided.

[Embodiments] Examples of the present invention will be described below with reference to FIGS. 1 to 6. FIG. 1 is a circuit diagram showing an embodiment of the ghost removal system of the present invention, FIG. 2 is a circuit diagram of the ghost removal device shown in FIG. 1, and FIG. 3 is a signal of the ghost removal reference signal. FIG.

The ghost removal system 1 shown in FIG. 1 is applied to a local satellite station, and receives a UHF television signal, converts it to a constant intermediate frequency signal, performs equalization processing, and then returns it to the UHF television signal of a predetermined channel. It consists of a relay device Hz that converts into a television signal and transmits it, and a ghost removal device 3 that is connected to this relay device 2 and removes a ghost wave superimposed on the desired wave based on the received waveform of the ghost removal reference signal. .

The relay device 2 shown in the embodiment is a 19th channel UHF
Radio waves (carrier frequency 507.25 MHz) are first passed through a UHFHF filter 5 from the receiving antenna 4, and then mixed with a second local oscillation signal of 525 MHz sent from the first local oscillation circuit 7 in the frequency conversion circuit 6,
．． It is converted into a first intermediate frequency signal of 75 MHz. The first intermediate frequency signal is supplied to an equalizer 9 via a bandpass filter 8 having a passband of 19 MHz and a ghost removal device 3. The first intermediate frequency signal whose amplitude and phase distortion have been corrected in the equalizer 9 is mixed with the first local oscillation signal of 567 MHz sent from the second local oscillation circuit 11 in the subsequent frequency conversion circuit 10, and is mixed with the first local oscillation signal of 549.25 MHz. That is, the second
UHF output filter 1 as 5-channel UHF radio wave
2.

The ghost removal device 3 cancels the ghost wave superimposed on the desired wave based on the transmission path characteristics estimated from the received waveform of the ghost removal reference signal (C, CR multiplied signal) superimposed and transmitted on the television signal. The ghost removal reference signal was introduced as a countermeasure against reception interference caused by ghosts, which is one of the pillars of Clear Vision (EDTV), and broadcast stations across the country are already using Clear Vision broadcasting with OCR signals superimposed. Specifically, the OCR signal is shown in Figure 3 (A
) is superimposed as a 5inX/X bar waveform shown in
The pedestal waveform shown in FIG. 2B is superimposed on the 2, 4, and 5.7 fields during the vertical retrace period, and is transmitted, following an 8-field sequence in which 8 fields complete one cycle. Also, the rising edge of this GCR signal is 4.2MH
It is a waveform that integrates the pulse response of a filter that has a flat amplitude characteristic up to z, and by utilizing the 45 μs ghost removal ability, it is possible to improve a ghost image with a subjective rating of 3- to a rating of 4. It is said.

By the way, the overall transmission path characteristics D(jω) of the transmitting system and receiving system including from the central television broadcasting station to the relay device 2 are as follows:
ω). However, D 1 (jω) represents the characteristics of the intra-office transmission system, D 2 (jω) represents the characteristics of the spatial transmission system, and D 3 (jω) represents the characteristics of the reception system within the relay device 2. In these systems, if it is determined that the received output when transmitting a signal 5inX/X having a frequency characteristic of R(jω) is G(jω), then D(jω
)=G(jω)/R(jω), the overall transmission path characteristics of the transmitting system and receiving system can be identified. Furthermore, the ghost removal device 1 has an overall transmission path characteristic of 1.
Since a filter characteristic H(jω) that returns to By doing so, ideal ghost removal is possible.

The ghost removal device 3 shown in the embodiment has a proximity ghost removal circuit 15 and a normal ghost removal circuit 16 connected in series between the first stage AD converter 13 and the last stage DA converter 14.
Each circuit 13, 14. ．． The GCR signal extracted from between 1516 and 1516 is taken into the central processing unit 20 line by line via the buffer memories 17, 18, and 19, and the coefficients obtained through the arithmetic processing by the central processing unit 20 are sent to the proximity ghost removal circuit 15. is normally set in the ghost removal circuit 16. 21 and 22 are a clock generation circuit and a timing generation circuit. In this example, the calculation by the central processing unit 20 is performed through waveform comparison between the OCR signal taken in from the buffer memory 17, 18, and 19 and the undistorted OCR signal generated within the central processing unit 20, and the ghost The characteristics of the transmission path that generates the waves are specified in terms of delay time (τ), phase (φ), and level (DU ratio).

The above-mentioned coefficients are then determined based on the specified characteristics, and are used to remove the proximal ghost and the normal ghost.

Therefore, the ghost waves superimposed on the UHF television signal are removed by the ghost removal device 3 between the bandpass filter 8 and the isogenetic type 9, and this eliminates the ghost waves from the existing Ghost-free UHF television broadcasts can be provided to each receiving household from these satellite stations. In addition, the ghost removal device 3 itself follows the same operating principle as a ghost canceller commercially available for home use, and can achieve sufficient results with only a slight cost for the parts used. It is possible to counter ghosts at a much lower cost than the cost of relocating a radio relay tower.

In the above embodiment, the ghost removal system 1 in which the ghost removal device 3 is applied to an existing satellite station is taken as an example, but it can also be applied to a CATV transmission station that is a cable broadcast transmission station. In this case, since the radio wave incoming conditions differ from channel to channel, ghost removal must be performed for each channel. Therefore, in the ghost removal system 31 shown in FIG.
A ghost removal device 35 corresponding to the number of VHF channels is provided between the HF channel distributor 33 and the head end 34 located at the end of the trunk cable to wired subscribers. The ghost removal device 35 eliminates proximity ghosts between a tuner circuit 36 that tunes and selects a VHF television signal, and an RF modulator 37 that converts the selected channel output into a VHF television signal of the same channel as the selected channel. Ghost removal circuit 38 that also removes normal ghosts
It is constructed by interposing.

In the case of cable broadcasting, the reception channel and retransmission channel are the same, so in order to avoid co-channel interference, it is necessary to thoroughly manage the phase of the reception radio wave and retransmission radio wave. 3
A retransmission signal is generated using the synchronization signal separated in step 6, and synchronization between the reception channel and the retransmission channel is achieved. Regarding the audio signal, since the influence of ghosts is not a problem in the audible band, the audio intermediate frequency signal obtained by the tuner circuit 36 is sent as is to the RF modulator 37, where it is converted back to the signal in the RF signal band, and the The method is to mix it into the signal. For this reason, the RF modulator 37 only needs to perform frequency conversion, and unlike systems that convert audio signals into baseband signals or composite signals, the RF modulator 37 can be used for broadcasting such as monaural broadcasting, stereo broadcasting, or two-audio broadcasting. There is no need for complicated modulation processing depending on the format.

The ghost removal system 41 shown in FIG. 5 is applied to large-scale public listening systems such as buildings and condominiums, and is installed between a VHF channel splitter 43 connected to a splitter 42 and a channel mixer 44. , a number of series-connected circuits of ghost removers 45 and RF modulators 46 for V/U conversion corresponding to the number of VHF channels are provided. The ghost removal device 45 functions to remove ghosts based on the received waveform of the ghost removal reference signal superimposed on the vertical blanking period of the television signal.

VHF from which ghosts have been removed by ghost removal device 45
The television signal is converted into a predetermined UHF television signal by a dedicated RF modulator 46 for each channel according to the /U channel correspondence shown in FIG. 6, and mixed by a channel mixer 44. The ghost-free UHF television signal mixed in the channel mixer 44 is mixed in the U/V mixer 47 with the non-ghost-removed VHF television signal branched and supplied from the splitter 42, and is sent to a building or an apartment. will be sent to each receiving household within the country.

In the case of this example, by adopting the UHF conversion method,
Users who own a television receiver with a UHF channel will have to re-preset the reception channel, but compared to a method in which reception and retransmission are performed on the same channel, there will be less interference due to direct wave interference in areas with strong electric fields. It has the advantage of not having to worry about reception problems such as ghosting, interference, or interference from the same channel, and is especially suitable for multiple households living in large cities with densely populated areas near broadcasting towers. suitable for

[Effects of the Invention] As explained above, the present invention receives a UHF television signal on which a ghost removal reference signal is superimposed during the vertical retrace period, converts it into a constant intermediate frequency signal, performs equalization processing, Since the ghost wave is removed based on the received waveform of the ghost removal reference signal when the signal is converted to a UHF television signal of a predetermined channel and transmitted again,
The ghost waves superimposed on the UHF television signal can be removed by a ghost removal circuit between the bandpass filter and the isolator, and although there was no ghost problem when it was first installed, the ghost wave became a problem due to the wave of urbanization. It is possible to supply UHF television broadcasts relayed by existing satellite stations with no ghosts to receiving households, and, especially for relay stations with paying receiving households, there is no need to relocate radio relay towers. Moreover, since it is sufficient to use a ghost canceling device with components that are comparable to commercially available ghost cancellers or have slightly higher-grade components, excellent effects such as high-quality radio wave relay can be achieved without incurring a cost burden. play.

In addition, the present invention tunes and selects a VHF television signal on which a ghost removal reference signal is superimposed during the vertical retrace period, removes ghost waves based on the received waveform of the ghost removal reference signal, and then tunes the VHF television signal to the same channel as the selected channel. Channel V
Since the configuration is configured to convert the signal to an HF television signal and output it, it is possible to provide effective ghost countermeasures for CATV stations, etc. where the reception channel and retransmission channel are the same, and by thorough synchronization management, the reception channel and retransmission channel can be As long as you eliminate co-channel interference that occurs between channels,
Since there are no ghost disturbances during the wired transmission process, C
It has excellent effects such as being able to send extremely high quality television signals to receiving households connected to ATV stations by wire.

Furthermore, the present invention operates on a VHF television signal in which a ghost removal reference signal is superimposed on a vertical retrace period,
Ghost waves are removed from a specific channel, and the video signal from which the ghost waves have been removed is converted to an LIHF television signal and output, so the reception channel of a television receiver with a UHF channel can be re-preset on the receiving side. However, compared to a method in which reception and retransmission are performed on the same channel, there is no need to worry about reception problems such as front ghosts or interference due to direct waves jumping in in areas with strong electric fields, or interference from the same channel. It has excellent effects, such as being suitable for public listening systems, etc., especially for buildings and condominiums in large cities where residences are densely populated near broadcasting towers.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the ghost removal system of the present invention, FIG. 2 is a circuit diagram of the ghost removal device shown in FIG. 1, and FIG. 3 is a signal of the ghost removal reference signal. A waveform diagram, FIG. 4 is a circuit configuration diagram showing another embodiment of the ghost removal system of the present invention, and FIGS. 5 and 6 are circuit configuration diagrams showing still other embodiments of the ghost removal system of the present invention. FIG. 3 is a diagram showing the relationship between reception channels and retransmission channels. 1.31,41. ,, Ghost removal system. 209. Relay device, 3.35, 45. , ,Ghost removal device.

Claims (3)

[Claims] (1) Receive a UHF television signal on which a ghost removal reference signal is superimposed during the vertical retrace period, convert it to a constant intermediate frequency signal, perform equalization processing, and re-enter the UHF television signal of the specified channel.
Ghost removal characterized by comprising a relay device that converts into an F television signal and transmits it, and a ghost removal device that is connected to the relay device and removes a ghost wave based on the received waveform of the ghost removal reference signal. system. (2) A tuner circuit that tunes and tunes a VHF television signal on which a ghost removal reference signal is superimposed during the vertical blanking period, and a tuner circuit that acts on the tuning output of this tuner circuit based on the received waveform of the ghost removal reference signal. It is characterized by comprising a ghost removal device that removes ghost waves, and an RF modulator that converts the video signal from which ghost waves have been removed by the ghost removal device into a VHF television signal of the same channel as the selected channel and outputs it. Ghost removal system. (3) A ghost removal device that acts on a VHF television signal on which a ghost removal reference signal is superimposed during the vertical retrace period and removes ghost waves for a specific channel, and a video signal from which ghost waves have been removed by this ghost removal device. , a ghost removal system comprising an RF modulator that converts the signal into a UHF television signal and outputs the signal.