KR20010102104A - Speeding up search tuning in television receivers - Google Patents

Abstract

A method of performing search tuning of a television signal in a television band including an analog television signal and a digital television signal is disclosed. First, an analog channel search is performed to determine all analog channels receivable within the television band. Next, a digital channel search is performed that skips the analog channels determined in the analog channel search. Digital channel search necessarily uses much fewer frequency steps than analog channel search, thus saving a significant amount of time by not searching for already determined analog channels.

Description

Speeding up search tuning in television receivers

With very few exceptions, television receivers for current analog television signals can automatically scan source signals in the frequency domain of useful channels stored in memory for later recall. Although various frequency allocation schemes exist for cable networks, the reality is that the result of exceptions and departures requires a search algorithm capable of searching for channels of any frequency in the band. Searching through all television reception bands needs to be accomplished within a reasonable amount of time (typically one minute) to avoid consumer complaints. Fast tuning is realized by scanning bands that take relatively many frequency steps at once. This is possible in that demodulators used in common analog television systems have a relatively large tolerance for, for example, 1000 kHz mistuning. Even if the tuning is not accurate, the demodulator can lock to the signal and provide feedback on frequency error to the host microcontroller that can improve the tuning of the tuner to the correct frequency.

DE 197 28 765 A1 outputs tuning data sequentially and outputs the tuning data when a signal from an automatic channel setting is input, thereby storing the channels with the signal for the wireless television, thereby allowing the television channel with the cable television signal to A method of performing automatic channel storage and selection is disclosed.

A typical seek tuning system works as follows. The system first determines if the last channel has been made. If the last channel has been done, the system ends the procedure. If the last channel has not been made, the system selects the next channel number. The channel number is stored in the television receiver along with the nominal frequency of the channel. As shown in Fig. 1A, each channel has a bandwidth of, for example, 6 MHz. To search for a received television signal, the system scans the bandwidth of the channel with, for example, 1000 kHz subband frequency steps starting at the first channel subband frequency step, which is the lowest frequency within the channel bandwidth around the nominal frequency of the particular channel. do. The system then attempts to acquire the next television signal. The system then determines whether the next television signal has been obtained. Once the next television signal has been obtained, the system stores channel frequency data. After storage of the channel frequency data, the system returns to the first step to determine if this channel is the last channel number. If the television signal has not been acquired, the system determines whether it is the last channel subband frequency step within the bandwidth of the particular channel. If not the last channel subband frequency step, the system selects the next channel subband frequency step and then returns to the next television signal step in order to attempt to acquire a television signal. If this is the last channel subband frequency step within the bandwidth of the particular channel, the system returns to the first step to determine if it is the last channel number.

With the introduction of several new digital television transmission signals for cable broadcasting and over-the-air broadcasting, there is an increasing demand for television receivers capable of receiving analog television signals and digital television signals. The signal applied to such a television receiver may now include a mixed signal of general analog RF signals as well as digital television (DTV) RF signals, which may be 64/256 QAM, 8/16 VSB. However, a demodulator for a DTV signal must be within, for example, 50-150 kHz of the received DTV signal so that the oscillator frequency of the demodulator can lock to the received DTV signal and provide feedback information regarding the actual carrier frequency. in need. Accordingly, seek tuning requires scanning the band in steps much smaller than the steps used when scanning analog television channels (e.g., 125 kHz, see FIG. 1 (b)), so that the seek tuning time is Greatly increased.

The present invention relates to the tuning of television receivers connected to a cable subscriber network, and more particularly to a tuning procedure known as "search tuning."

Fig. 1A is a diagram showing a television channel showing an analog channel subband frequency step of 1000 kHz, and Fig. 1B is a diagram showing a television channel showing a digital channel subband frequency step of 125 kHz.

2 is a schematic block diagram of a television receiver capable of receiving analog television signals and digital television signals.

It is an object of the present invention to minimize the amount of time required for search tuning for all available television signals in a network carrying a mixed signal of analog television signals and digital television signals.

To this end, the present invention provides search tuning as defined by the independent claims of the claims. The dependent claims provide advantageous embodiments.

Since the DTV signals do not broadcast on the same channel / frequency as analog television signals, the television receiver does not need to search the entire television frequency band to determine the available DTV signals. By first performing an analog television signal search that can be done at a relatively high speed, the television receiver can eliminate channel frequency positions of the determined analog television signals. In this case, the television receiver only needs to search / scan at a channel frequency position not occupied by the analog television signal.

The present invention will now be described with reference to the accompanying drawings, taking into account the above and further objects and the advantages presented below.

2 shows a schematic block diagram of a television receiver capable of receiving analog television signals and digital television signals. The television signal is input to the television receiver via an antenna 30. While the antenna 30 is shown, it should be understood that the television signals may be provided by a CATV system or a combination of a standard television antenna and a phase antenna. The antenna 30 is connected to a tuner 32 that tunes to various television signals. An analog demodulator 34 is connected to the output of the tuner 32 and applies an output to one input of the switch 36. Digital demodulator 38 is also connected to the output of the tuner 32 and includes a phase locked loop with a tuning resolution of, for example, 62.5 kHz. After conversion in the D / A converter 40, the output of the digital demodulator 38 is applied to the second input of the switch 36. The output from the switch 36 is applied to the audio signal processor 42 to generate an audio signal for the loudspeakers 44 and 46. In addition, the output from switch 36 is applied to video signal processor 48 to generate a video signal for display 50.

Tuning of the tuner 32 is controlled by a microcontroller 52 that receives error signals from the analog and digital demodulators 34 and 38. Depending on whether the analog or digital television signal is being tuned, the microcontroller 52 controls the switching position of the switch 36. The microcontroller 52 also provides a control signal to the audio signal processor 42 for controlling the audio parameters of the reproduced audio signal and to the video signal processor 48 for controlling the visual parameters of the reproduced video signal. Is authorized. The microcontroller 52 is controlled by a user using a remote control transmitter 56 that transmits an infrared signal to a user controller 54 or an infrared receiver on the user controller 54.

A list of all television channels, as well as each nominal carrier frequency, is stored in the microcontroller 52. Various allocation schemes exist, but in practice, the actual carrier frequency of the television signal for a particular channel may vary within the channel bandwidth around the nominal carrier frequency. Therefore, the microcontroller 52 needs to perform search tuning to search for the actual carrier frequency of all available television channels.

The procedure for the television receiver to seek tune an analog television signal and a digital television signal can be described as follows. At the beginning of the procedure, the television receiver performs an analog channel search. This search may be the same as the search shown in FIG. 1. As mentioned above, the frequency step size for analog channel search is set to 1000 kHz, but it should be understood that this step size is arbitrary and may be set to other values, for example, in the range of 750-1250 kHz. After the analog channel search, the television receiver performs a digital channel search, after which the procedure is stopped.

The procedure by which the television receiver performs a digital channel search can be described as follows. After performing an analog channel search, the procedure determines if the current channel is the last channel in the television band. If it is the last channel, the procedure is stopped. If not the last channel, the television receiver proceeds to the next channel number and compares this channel number with the channel number of the television signal required for analog channel search. If the current channel number matches the stored analog channel number, the procedure returns to the first step. If not, the procedure sets the first channel subband frequency step for the current channel. The television receiver then attempts to obtain a digital signal. Once the digital signal is obtained, the television receiver stores the digital channel frequency data and returns to the first step. If not obtained, the procedure determines whether the current channel subband frequency step is the last step of the current channel. If not, the procedure proceeds to the next channel subband frequency step, which returns to the digital signal acquisition step. If the current channel subband frequency is the last frequency in the current channel, the procedure returns to the first step.

As mentioned above, the digital demodulator 38 has a tuning resolution of 62.5 kHz. Therefore, in order to ensure the search for the proper carrier frequency, the step size of the channel subband frequency is set to twice the tuning resolution, that is, 125 kHz.

In short, by performing a faster analog channel search first, the assigned analog channels can be removed from the digital channel search when the digital channel search is performed, and thus, by the digital channel search when scanning and searching the television band. The time involved is greatly reduced.

The above-mentioned embodiments are illustrative rather than limiting of the present invention, and it should be noted that those skilled in the art will be able to design many other embodiments without departing from the scope of the claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The term "equipment" does not exclude the presence of components or steps other than those listed in the claims. Singular expressions of components do not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware with various distinct components, and by means of a suitably programmed computer. In the device claim enumerating various means, several of these means may be embodied by hardware of the same item. The simple fact that specific configurations are mentioned in different dependent claims does not mean that a combination of these configurations cannot be used to advantage.

Claims (10)

In the search tuning method of a television receiver for an analog signal and a digital signal, Receiving an input television signal comprising a plurality of analog television signals and a digital television signal; Obtaining all the analog television signals of the input television signal and obtaining assigned channel numbers of the obtained analog television signals; Obtaining all the digital television signals of the input television signal, and obtaining assigned channel numbers of the obtained digital television signals, Acquiring the digital television signals comprises skipping channel frequency positions of the obtained analog signals determined in acquiring the analog television signals. The method of claim 1, Acquiring the analog television signals comprises: Determining whether the current channel number is the last channel number and ending the routine if the current channel number is the last channel number; Selecting a next channel number; Selecting a first channel subband frequency step; Attempting to acquire a television signal within the channel subband frequency; Storing channel frequency data when a television signal is obtained, and returning to determining whether the current channel number is the last channel number; If the television signal is not obtained, determine whether the current channel subband frequency step is the last channel subband frequency step within the bandwidth of the current channel, and if the current channel subband frequency step is the last channel subband frequency step Returning to determining whether the channel number is the last channel number; If the current channel subband frequency step is not the last channel subband frequency step, selecting a next channel subband frequency step and then returning to attempting to acquire the television signal. Seek tuning method. The method of claim 2, And said channel subband frequency step falls within a frequency range of 750-1250 kHz. The method of claim 3, wherein And said channel subband frequency is 1000 kHz in step. The method of claim 1, Acquiring the digital television signals includes: Determining whether the current channel number is the last channel number and ending the routine if the current channel number is the last channel number; Selecting a next channel number; Comparing the current channel number with a stored analog channel number; If there is a match in the comparing step, returning to the determining step; Selecting a first digital channel subband frequency; Attempting to obtain a television signal within the digital channel subband frequency; Storing channel frequency data when a television signal is obtained, and returning to determining whether the current channel number is the last channel number; If a television signal is not obtained, determine if the current digital channel subband frequency is the last digital channel subband frequency within the bandwidth of the current channel, and if the current digital channel subband frequency is the last digital channel subband frequency, the current channel. Returning to determining whether the number is the last channel number; If the current digital channel subband frequency is not the last channel subband frequency, selecting the next digital channel subband frequency and then returning to attempting to acquire the television signal. How to tune. The method of claim 5, Wherein the step size of the digital channel subband frequency is twice the tuning resolution of the digital modulator of the television receiver. The method of claim 6, And said step size is 125 kHz. The method of claim 2, The digital channel search, Determining whether the current channel number is the last channel number and ending the routine if the current channel number is the last channel number; Selecting a next channel number; Comparing the current channel number with a stored analog channel number; If there is a match in the comparing step, returning to the determining step; Selecting a first digital channel subband frequency; Attempting to obtain a television signal within the digital channel subband frequency; Storing channel frequency data when a television signal is obtained, and returning to determining whether the current channel number is the last channel number; If the television signal is not obtained, determine if the current digital channel subband frequency is the last digital channel subband frequency within the bandwidth of the current channel; and if the current digital channel subband frequency is the last digital channel subband frequency, the current Returning to determining whether the channel number is the last channel number; If the current digital channel subband frequency is not the last channel subfrequency, selecting the next digital channel subband frequency and then returning to attempting to acquire the television signal. Way. A search and tuning apparatus for television receivers for analog signals and digital signals, Means for receiving an input television signal comprising a plurality of analog television signals and a digital television signal; Means for obtaining all the analog television signals of the input television signal and obtaining assigned channel numbers of the obtained analog television signals; Means for obtaining all the digital television signals of the input television signal, and obtaining assigned channel numbers of the obtained digital television signals, And the means for acquiring the digital television signal comprises means for skipping channel frequency positions of the obtained analog television signals determined by the means for acquiring the analog television signals. In a television receiver, A search tuning device as claimed in claim 9; A video signal processor coupled to the search tuning device; A television receiver having a display coupled to the video signal processor.