KR0142101B1 - Video tape recorder player device - Google Patents

Abstract

None.

Description

Video signal recorder / player

1 is a block diagram of a conventional video tape recorder / player device.

2 is a block diagram of a video tape recorder / player embodying the present invention.

3 is a flow chart for test and selection operations in the realization of the present invention.

4 is a schematic diagram of the frequency spectrum for signals appearing in the UHF television channel range.

4A shows a dual sideband output of a modulator.

* Explanation of symbols for main parts of the drawings

LO: Local Oscillator VDA: Voltage Controlled Amplifier

CFS: Channel Frequency Selector

The present invention relates to the formation of video signals from recorded information (with or without audio signals), and also to the transmission of these video / audio signals to a television receiver for transmission of video / audio signals to an information channel provided on a suitable transmission medium. And an information channel having a predetermined bandwidth relative to the frequency of the carrier signal.

In the case of home video tape recorder / player devices, the information channel is commonly known as a playback channel, the recorder portion being selectively tuned to any one of a plurality of UHF television channels, Television transmissions delivered to the channel can be received and recorded on tape.

UHF television channel allocation for the IV and V bands in the UK has 44 channels of 21 to 34 and 39 to 68, with carrier frequencies for adjacent channels at 8 MHz intervals. A description of the channel assignment is disclosed in IBA Technical Report 10, May 1978 and is not described in the specification of the present invention. In the European continent, extended frequency allocation is used for the band.

The playback channel used in home video tape recorder / player devices is a particular one of these 44 UHF television channels that are not conceptually assigned to terrestrial broadcast television stations. Therefore, depending on where the device is located, interference often appears for the playback channel from the broadcast channel transmitting the television transmission. There are many video tape recorder / player devices that manually adjust the frequency of the carrier signal defining the playback channel to shift the channel relative to the interfering broadcast channel.

However, this is not always successful in reducing interference. Interference from broadcast channels is known to be particularly severe in some European regions where television transmissions from various different transmitters are received.

Japanese application Nos. 53-81786 and 59-263429 provide a video tape recorder that is tested to detect the presence or absence of a television transmission and use an empty channel known as a playback channel for the video tape recorder. Known in Thus, as described below in the specification, a relatively simple method of selecting a playback channel is limited in overcoming the inter-channel interference of the various transmit / receive requirements added to current home video tape recorder / player devices.

It is an object of the present invention to provide a video tape recorder / player device in which the problem of interchannel interference is alleviated in a more advantageous manner.

Using a channel testing and selection process in accordance with the present invention, a video signal recorder / player device that identifies an empty UHF television channel for use as a playback channel for the device, determines the signal level present in the UHF television channel to which the device is tuned. And means for selecting to use as a playback channel for the device a channel having a signal level less than a first predetermined level, wherein the first predetermined level is characterized in that A signal level of a immediately adjacent lower channel is smaller than a second predetermined level and greater than a first predetermined level, and this second predetermined level indicates using the adjacent channel as a broadcast channel.

By testing the actual signal level of the channel rather than just testing for an empty channel identified as no broadcast television transmission, the entire frequency spectrum is examined for the channel range, and the selection of the channel to be used as the playback channel is made from that channel range. Because of this investigation, the present invention has significant advantages over the prior art in two respects. Firstly, it is possible to prevent the use of any channel with an unacceptable high interference signal as a reproduction channel, and simplifies rejection of channels including broadcast television transmission. For example, such an interference signal is an aerial data signal. Secondly, there is an advantage that any channel is rejected from being used as a playback channel when the immediately adjacent subchannel includes broadcast television transmission. As a result of the latter channel rejection, when received at the aerial input of the video signal recorder / player device, the interference of such broadcast television transmissions is prevented by a modulated carrier signal transmitted to the playback channel of the device. This interference is, when normally implemented for economic benefit, a dual with an upper sideband where the modulator output signal from the videotape recorder / player device occupies the playback channel and a lower sideband (undesired) that occupies the nearest subchannel. Occurs when sideband signal.

In terms of its effectiveness when applying the present invention to a video tape recorder / player device, the signal level is a measure of the control voltage already formed within the device as a measure of the input signal strength to provide automatic gain control of the input amplifier stage. Determined by measuring the size.

By use of the invention, the selectable playback channel has little interference from any broadcast channel and the channel itself does not cause interference with respect to reception from the broadcast channel.

In carrying out the invention, the test means is arranged to determine whether the signal level is in the full range of the UHF television channel to which the apparatus can be tuned or only in a small range of channels with an empty channel available as a playback channel. The small range of channels is not allocated for use as a broadcast channel that supports the local location in which the device is used. In the latter case, the testing does not need to cover a large range of signal levels.

Testing of the signal level, and subsequent selection and setting of the playback channel, is performed only at the time of setting-up of the device at a particular local location. In other words, testing of the signal level, and subsequent selection and setting of the reproduction channel are performed periodically at the set time interval. In this case, it is possible to change the channel used as the reproduction channel. This change can be initiated by the viewer when interference occurs in a playback channel that was previously free of interference. Another embodiment is to allow signal level testing and subsequent channel selection and setup to be performed each time a playback channel is taken to be used. Appropriate control means are provided for the control of these various operations. Of course, the television receiver to which the device is connected needs to be retuned to a new playback channel.

The test means and selection means may be realized as a microcontroller and associated memory, a channel frequency selector, a tuner comprising a local oscillator, and a signal level detector, the microcontroller being programmed according to a signal level test and selection algorithm, which The algorithm is initialized when the channel frequency selector is required to set the tuner to the carrier signal frequency of each channel to be tested. The signal level detector is operable to recall the signal level in the associated channel, and the microcontroller assigns a tested channel as a playback channel in response to the signal values received from the signal level detector.

In the case of a video tape recorder / player device, a microcontroller and associated memory, a channel frequency selector, and a tuner with a local oscillator are already provided in the device for normal operation. The only additional means required for the selection means and the test means are a signal level detector and additional software for the test and selection algorithm.

The setting means for setting the carrier signal for the reproduction channel to a frequency defining a channel selected as the reproduction channel is a digital-to-analog analogue which sets a voltage controlled oscillator for generating a carrier signal for the device under operation of the microcontroller to operate at the required frequency. It is a converter. The algorithm includes programming a microcontroller for this control function.

The invention will be understood in more detail by way of example of the accompanying drawings.

Referring to the drawings, the conventional video tape recorder / player apparatus represented by the block diagram of FIG. 1 has an antenna input terminal AE for receiving a television signal broadcast on a UHF television channel. The input terminal AE is connected to the video output terminal VD through the combiner COMB for connection to the input terminal of the television receiver TV. The input terminal AE is connected to the input of a voltage-controlled amplifier VCA and the output of this VCA is connected to the input of a tuner TUN with a local oscillator LO. The channel frequency selector CFS can set the tuner TUN to several UHF television channels under the control of the microcontroller MIC. The output of the tuner TUN is connected to the input of the intermediate frequency stage IF.

The feedback connection from the intermediate frequency stage IF to the amplifying VCA is provided for the automatic gain control of the amplifier by the feedback voltage FV. The output of the intermediate frequency stage IF is connected to an input of a demodulator DEM for retrieving audio and video baseband signals contained in the received television signal.

Thus, these signals are passed to the tape recorder / player element R / P for recording on the tape.

The video tape player / recorder device also has a modulator MOD and a voltage controlled oscillator VCO. The oscillator VCO is preset to generate a carrier signal CS that defines a playback channel for the device. The reproduction channel is apparently one of the UHF television channels 30 to 40 and can be preset within this range as indicated by the resistance element RES. In reproduction from the recorded tape, the mixed video baseband signal CVBS and the audio signal AS are applied from the element R / P to the modulator MOD, which uses these signals to modulate the carrier signal CS.

The resulting modulated signal is applied to video output terminal VD via the combiner COMB. The signal CVBS contains the original video baseband signal along with the synchronization signal for the television receiver. The device R / P can be used to directly supply a demodulator output signal to the modulator MOD without recording and playback.

The channel selection and recording and reproducing operations of the element R / P are controlled by the microcontroller MIC in accordance with a control signal from a user interface (not shown). In the video tape recorder / player apparatus according to the invention of the block diagram of FIG. 2, the elements are described with the same reference numerals as in FIG. The apparatus of FIG. 2 further comprises additional software for the digital-to-analog converter DTA, the analog-to-digital converter ATD, and the microcontroller MIC in place of the resistive element RES of FIG.

The converter ATD is connected to receive the feedback voltage FV from the intermediate frequency stage IF and converts this voltage into a digital value VDV input to the microcontroller MIC.

Because of the presence of automatic gain control provided for the feedback connection from the frequency stage IF to the amplifier VCA, the magnitude of the feedback voltage FV is an accurate measure of the received signal level in the UHF television channel on which the tuner TUN is set.

The converter DTA operates under the control of a microcontroller MIC to set the voltage-controlled oscillator VCO to generate a carrier signal with a frequency defining any one of the UHF television channels to which the device can be tuned as a playback channel. It is possible. The converters ATD and DTA are PFC 8591 (Philips) type integrated circuits controlled by a microcontroller MIC via a 2-wire bidirectional I²C bus.

Such integrated circuits, together with additional software for the microcontroller MIC, are the only additional means required for the realization of the present invention.

To select one of the UHF television channels as the playback channel, the microcontroller MIC may be operable to supply a continuous digital channel tuning command signal tcs to the channel frequency selector CFS according to the signal level test and selection algorithm. In response to the command signal, supplies to the tuner TUN a continuous tuning voltage tv which in turn tunes the local oscillator LO at the carrier frequency for each UHF television channel. When each UHF television channel is tuned, the feedback voltage FV is converted by the analog-to-digital converter ATD into the appropriate digital value VDV, which is input to the microcontroller MIC. The digital value VDV in the microcontroller is used to select one of the tested UHF television channels as the playback channel. The digital command signal Ptcs informing the selected channel is generated by the microcontroller MIC and converted to the tuning voltage Ptv by the digital-to-analog converter DTA, which converts the voltage controlled generator VCO to the carrier frequency of the selected channel.

In implementing the invention, the programming of the microcontroller MIC ensures that the test, selection, and setup sequence is executed only at the time of setup of the device at a particular regional location, the sequence is executed periodically, each time a playback channel is used. . The selection of a UHF television channel to be used as a playback channel may include testing of all UHF television channels or just testing a small range of channels.

Instead of using the feedback voltage FV, the determination of the signal level in the UHF television channel may include the actual signal received on each channel. This requires a signal level detector, which receives the received signal and responds to generate an analog voltage that indicates the signal level. This analog voltage is digitized and applied to the microcontroller MIC in the same manner as the feedback voltage FV.

Consider the flowchart shown in FIG. 3 and the UHF channel frequency spectrum shown in FIG. The legend of the various elements in the flow chart represents the following algorithm for playback channel selection in the UHF channel range 30-40.

F1 (INT): Enter an algorithm to determine the playback channel for the initialization or setup of the device at one location.

F2 (SEL PB): Enters an algorithm to select a playback channel each time the device is used.

F3 (W / T): Inputs to the algorithm under weight / timer control for periodic resolution of the playback channel.

F4 (STRT): This step represents the beginning of the algorithm.

F5 (SE / tv → CH36): Sets the local oscillator tuning voltage tv so that channel 36 is tuned.

F6 (VDV > VR1?): Determines whether the generated signal level VDV is larger than the first reference value VR1.

F7 (VDV> VR2?): This step starts when VDV> VR1. Reference to the channel frequency spectrum shown in FIG. 4 indicates that this case is considered since the interfering signal IS is present on channel 36.

However, if it is VDVVR2, the flow goes from step F7 to step F8.

F8 (TC = CH40?): This step determines if the channel to be tested is the last channel in the range. If it is the last channel, step F9 is started; if it is not the last channel, step F10 is started.

F9 (SE / tv → CH30): This step sets the tuning voltage tv such that channel 30 is tuned and reenters step F6.

F10 (SE / tv → tv + 1): This step increases the tuning voltage tv so that the next channel 37 is tuned and reenters step F6.

F11 (SE / Ptv → SC): This step is entered from step F6 because it is VDVVR1 for channel 37. This step sets the tuning voltage Ptv to tune the oscillator VCO to channel 37 as a channel.

F12 (EXT): The algorithm exits the algorithm after selection of the playback channel.

F13 (SE / tv → tv + 1): This step begins when VDV> VR2 in step F7 and indicates that the channel to be tested includes the desired television transmission to increase the tuning voltage tv so that the next channel is tuned. .

F14 (CH = 40?): This step enters from F13 and determines whether the next channel on which the tuning voltage tv is maintained is channel 40 or not. If channel 40, step F15 is started; if not, channel F16 is started.

F15 (SE / tv → CH30): This step sets the tuning voltage tv such that channel 30 is tuned and reenters step F6.

F16 (VDV > VR2?): This step determines whether the tested (next) channel contains the desired television transmission. If VDV > VR2, the process returns to step F13 to increase the channel number and repeat the loop formed by steps F13 to F16.

If VDV> VR2, step F17 is started.

F17 (SE / tv → tv + 1): This step also increments the channel number and skips so that the immediately adjacent subchannel contains an empty channel except that it contains the desired television transmission.

The channel frequency spectrum diagram shown in FIG. 4 covers eleven consecutive UHF channels 30-40 in the frequency space of 8 MHz at 542 MHz to 630 MHz.

Channels 30, 34 and 40 become the desired channel WC since they contain the desired television transmission TT with a signal level greater than VR2. Channels 32 and 36 are unwanted channels UWC because they contain an interfering signal 1S having a signal level greater than VR1.

Channels 31 and 35 cannot be selected as a playback channel because immediately adjacent subchannels 30 or 34 become the desired channel WC and no signal exists. The remaining channels 33, 37, 38 and 39 become free channel FCs available for selection as a playback channel.

The algorithm indicated by the flowchart of FIG. 3 rejects channel 36 and selects channel 37 as the playback channel. If channels 36 to 39 have a signal interference level greater than VR1, channel 33 is finally selected as the playback channel.

Figure 4a shows the dual sideband output MOD O / P of the modulator. The desired upper sideband WB occupies the selected playback channel N and the unwanted lower sideband LSB occupies the immediately adjacent lower channel N-1. Since the present invention never allows the playback channel to be selected such that unwanted lower sidebands cause interference in the desired immediate adjacent subchannel, the video output terminal (VD) (FIG. 2) allows the television receiver TV to be used in the playback channel. The video tape recorder / to connect to a common bus B that is connected to other television receivers TV1 and TV2 to receive broadcast television transmissions on their respective channels simultaneously with receiving a modulated signal from the modulator MOD of the same channel. The player device can be configured.

A possible modification of the algorithm represented by the flowchart of FIG. 4 is to select as a playback channel a channel containing an interference signal having the lowest level, where the free channel FC does not have a signal level less than VR1. This can easily be realized by memorizing the signal level from several free channel FCs and selecting the lowest signal level after a number of test cycles.

From this specification, other modifications are made by those skilled in the art. Such modifications inherently include other features already known and may include other features that may be used in addition to or instead of those described above. Although the claims are represented by a particular combination of features in the present application, the disclosure of this patent application may also include any new feature or any combination of any of the above features, either generalized, implied, or explicitly described. And whether or not it relates to the same invention as claimed in the claims and whether or not to mitigate any technical problems the invention may achieve. Applicants will appreciate that new claims represent combinations of such features and / or such features during the present patent application.

Claims (9)

16. A video signal recorder / player apparatus for identifying an empty UHF television channel to be used as a playback channel for a device through a channel testing and selection process, the apparatus comprising: test means for determining a signal level present in a tuned UHF television channel; And selection means coupled to the test means to receive the determined signal level, wherein the selection means selects a UHF channel whose signal level is less than a first predetermined level to be used as a playback channel for the device. The first predetermined level represents a channel that is tolerantly free of interference, and the signal level in the immediately adjacent lower UHF channel is higher than the first predetermined level and less than the second predetermined level, wherein the second predetermined level is Characterized in that the adjacent channel is used as a broadcasting channel. A video signal recorder / player device. Further comprising control means for controlling signal level testing by the test means and subsequent selection and setting of a playback channel by the selection means to be executed only at the time of setting of the device at a specific regional location. Video signal recorder / player device. The video signal recorder / player apparatus according to claim 1, further comprising control means for controlling to periodically perform signal level testing by the test means and subsequent setting of a reproduction channel by the selection means. . The video signal according to claim 1, further comprising: control means for controlling the testing of the signal level by the test means and subsequent setting of the reproduction channel by the selection means to be executed every time the reproduction channel is used. Register / player device. 5. A test according to any one of the preceding claims, wherein said test means and selection means are realized as a microcontroller and associated memory, a channel frequency selector, a tuner comprising a local oscillator, and a signal level detector, wherein the microcontroller is a signal. Programmed according to a level test and selection algorithm, the algorithm is initialized when a channel frequency selector is required to set the tuner to the carrier signal frequency of each channel to be tested, and the signal level detector can detect the signal level in the associated channel. And the microcontroller assigns the tested channel as a playback channel in response to the signal values received from the signal level detection. 6. The apparatus of claim 5, wherein the apparatus is a video tape recorder / player apparatus and a tuner comprising the microcontroller and associated memory, the channel frequency selector, the local oscillator is already in the apparatus for normal record-recording and reproducing operation. A video signal recorder / player device, characterized in that provided. 7. The apparatus according to claim 6, wherein the setting means for setting a carrier signal for a reproduction channel to a frequency defining a channel selected as the reproduction channel is a digital-to-analog converter, which is controlled by the microcontroller. Set a voltage controlled oscillator that generates a carrier signal for the carrier at the required frequency, the algorithm comprising programming a microcontroller for such a control function. 6. The signal level of the tested channel is determined by measuring the magnitude of a control voltage already formed within the device as a measure of the input signal strength to provide automatic gain control of an input amplifier stage. Video tape tape recorder / player. 8. A signal level according to claim 6 or 7, wherein the signal level of the tested channel is determined by measuring the magnitude of a control voltage already formed in the device as a measure of the input signal strength to provide automatic gain control of an input amplifier stage. Video signal tape recorder / player.

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