CN101325669A - Method for blind scanning digital television broadcast receiving system by using frequency spectrum analysis - Google Patents

Abstract

A method for using spectral analysis as a Blind scan (Blind Search) for a digital television broadcast receiving system, comprising the steps of: firstly, receiving a television broadcast signal presented by a time domain signal, converting the television broadcast signal from the time domain signal into a frequency domain signal, and analyzing the frequency spectrum pattern characteristic of the frequency domain signal to quickly judge whether the received television broadcast signal is effective or not and distinguish whether the television broadcast signal is a digital television signal or an analog television signal; if the signal is a digital television signal, the bandwidth parameter of the system modulation signal can be directly estimated according to the spectrum pattern characteristic. Therefore, the type of the received television broadcast signal can be quickly identified and respectively processed to accelerate the blind scanning speed.

Description

Utilizing Spectrum Analysis as a Blind Scanning Method for Digital TV Broadcasting Receiving System

technical field

The invention relates to a method for blind scanning of a digital television broadcasting receiving system, in particular to a method for using frequency spectrum analysis as a blind scanning method for a digital television broadcasting receiving system.

Background technique

As wireless TV has started to enter the digital age, the broadcast program signal has entered the stage of synchronous transmission of analog and digital from analog signal. This is another major change after the TV colorization since the TV broadcasting went through half a century.

With the advent of the digital age, television broadcasting is gradually converting from traditional analog systems to digital systems. Since the analog system is often affected by terrain and surface features, there will be poor reception or signal fluctuations. The digital video broadcasting system can overcome such interference and provide programs with higher picture quality and better sound quality. At the same time, the use of frequency spectrum can be more efficient, for example, more programs can be transmitted on the same frequency bandwidth as analog TV. More importantly, digital video broadcasting can also provide various value-added services derived from data broadcasting (Data Broadcasting).

Television broadcast media mainly include: cable, satellite, microwave, terrestrial and other methods. In terms of digital TV terrestrial broadcasting standards, it mainly includes ATSC (Advanced Television Systems Committee) in the United States, DVB-T (Digital Video Broadcasting-Terrestrial) in Europe, and ISDB-T (Integrated Services Digital Broadcasting-Terrestrial) in Japan. In addition, for the current terrestrial TV broadcasting system, there are two different standard TV signals, analog and digital, so in the digital TV receiver, there will be a so-called blind search (Blind Search) function, which is a selective The initialization setting function can be provided by hardware or software, and is mainly used for scanning digital programs. When the user uses a digital TV receiver to receive digital TV programs for the first time, or when the user does not know the program frequency (Frequency) and When modulating the parameters of the signal, use this function to find out all the frequency points and programs that can be received at present. The function and method of blind scanning of conventional technology have following two kinds at present: one is to preset the program data announced locally in the digital television receiver, and when blind scanning, just be used for reconfirming that the preset program can be normally received ; The other is true blind scan, because we do not know any program frequency and signal modulation parameter information of the receiving location in advance, including whether the TV signal of a certain frequency is an analog signal or a digital signal, we must first assume that the receiving location The signal is a digital signal, and then use the software to input the parameter combination to the demodulator (Demodulator), and then check its status. After the timeout, try another set of parameters. After trying all the parameters, give up the search at last to enter Search for the next frequency point. When encountering an analog TV signal, if it cannot be identified quickly, the demodulator must try a variety of modulation parameter combinations, as many as hundreds, so too long blind scan time will be wasted. And when receiving a digital signal, if the quality of the received signal is poor, a lot of time will be wasted.

Contents of the invention

In view of this, the technical problem to be solved by the present invention is to provide a method for using spectrum analysis as a blind scan of a digital TV broadcast receiving system, which uses spectrum characteristics to judge whether the received terrestrial TV broadcast signal is a valid signal, and quickly The regional distinction belongs to digital TV terrestrial broadcasting system or analog TV terrestrial broadcasting system.

In order to solve the above problems, according to a solution proposed by the present invention, a method for using spectrum analysis as a blind scan of a digital television broadcasting receiving system is provided. The steps include: first receiving a signal presented in the form of a Time Domain signal The terrestrial television broadcast signal, and convert the time domain signal into a frequency domain (Frequency Domain) signal, and the frequency domain signal forms a spectrum pattern; and confirm that the received broadcast signal is a valid signal. Next, it is judged whether the spectrum pattern satisfies the graphic feature of a left-right sideband symmetry and a flat bandwidth. If the spectrum pattern contains the above-mentioned graphic feature, it means that the terrestrial TV broadcast signal is a digital TV signal, and then demodulates and records the The terrestrial TV broadcast signal is a program frequency point, and the bandwidth of the digital TV signal can be estimated at the same time, so as to save the time required for back-end demodulation and other operations. In addition, when the spectrum pattern does not contain the graphic features of symmetrical left and right sidebands and flat bandwidth, it means that the terrestrial TV broadcast signal is an analog TV signal, and then give up the search at this frequency point and enter the next frequency point search to continue receiving other terrestrial TV broadcast signals.

In order to solve the above problems, according to another solution proposed by the present invention, a method for using spectrum analysis as a blind scan of a digital television broadcasting receiving system is provided. broadcast signal, and convert the time domain signal into a frequency domain signal, and the frequency domain signal will form a frequency spectrum pattern; and confirm that the received broadcast signal is a valid signal. Then, it is judged whether the frequency spectrum pattern includes a graphic feature with a fixed frequency spectrum position and contains an image carrier or a sound carrier. If the frequency spectrum pattern includes the above-mentioned graphic feature, it means that the terrestrial TV broadcast signal is an analog TV signal, The search for the terrestrial television broadcast signal is then abandoned. And if the spectrum pattern does not include the fixed spectrum position and does not contain the image carrier and the sound carrier graphic feature, it means that the terrestrial television broadcast signal is a digital television signal, and then demodulates and records the terrestrial television broadcast signal as a program frequency.

The above overview, the following detailed description and accompanying drawings are all for further explaining the ways, means and effects of the present invention to achieve the intended purpose. Other purposes and advantages of the present invention will be described in the subsequent description and drawings.

Description of drawings

Fig. 1 is the spectrum analysis diagram of the present invention about an analog television signal;

Fig. 2 is the frequency spectrum analysis figure about a digital television signal of the present invention;

Fig. 3 is a flowchart of an embodiment of a method for using spectrum analysis as a blind scan method for a digital television broadcast receiving system according to the present invention; and

FIG. 4 is a flow chart of another embodiment of the method for using spectrum analysis as a blind scan method for a digital TV broadcast receiving system according to the present invention.

Explanation of schematic symbols

Picture carrier (Picture carrier)a

Audio carrier b

Detailed ways

Please refer to FIG. 1 and FIG. 2 at the same time, which are spectrum analysis diagrams respectively used to describe an analog TV signal and a digital TV signal according to the present invention. What is explained earlier here is that the present invention uses the DVB-T (Digital Video Broadcasting-Terrestrial) of European regulations as the preferred implementation description of the following digital TV terrestrial broadcasting standards, and the PAL (Phase Alternating Line) of European regulations and the U.S. The standard NTSC (National Television System Committee) is used as a description of the preferred implementation of the following analog TV terrestrial broadcasting standards.

Among them, to distinguish the graphic features of the digital spectrum and the analog spectrum, the most important thing is to judge whether the spectrum is symmetrical. From the analog TV spectrum in Figure 1, it can be seen that the irregular pattern in the shadow is its real graphic distribution, and the range starting from its highest peak includes two parts, which are 4MHz and Frequency extending to the right X-axis. Extending to 1.25MHz of the X-axis Frequency on the left, and the dotted line extending to 4MHz on the left indicates that if the graph distribution is left-right symmetrical, the shadow on the left should extend to the farthest point of the dotted line, but this is not the case, so we can see that the simulation The TV spectrum is characterized by left-right asymmetry. Next, referring to Figure 2, starting from the X-axis Frequency 0MHz, it can be seen that the bandwidth on the left and right sides (about Frequency (-4)HMz ~ 4HMz) is evenly distributed, and looking further away from the two sides, it can also be seen that the inclination The angles are also the same, so it can be seen with certainty that the digital TV spectrum is a graphic feature of left-right symmetry.

Other judgments include that the bandwidth of the digital TV spectrum (about Frequency (-4) HMz ~ 4HMz), in addition to being left-right symmetrical, it presents a flat bell-shaped distribution, not a hill-shaped distribution like the analog TV spectrum. bell-shaped distribution. Furthermore, the relative positions of the video carrier and the audio carrier in the analog TV spectrum are fixed, and the analog TV spectrum will contain a high-energy picture carrier (Picture carrier) a and audio carrier (Audio carrier) b, and the digital TV spectrum will be none.

With reference to the above, it can be found that there is a great distinction between the digital TV spectrum and the analog TV spectrum, so Figure 3 and Figure 4 disclosed by the present invention can be used as a blind system for a digital TV broadcasting receiving system based on the above-mentioned spectrum difference. Scan (Blind Search) method.

Please refer to FIG. 3 , which is a flowchart of an embodiment of a method for using spectrum analysis as a blind scan of a digital television broadcast receiving system according to the present invention, including: first, at the current frequency point, detect whether there is a time domain (Time Domain ) signal type presented terrestrial television broadcast signal input (S301), if the detection result is yes, then receive, and convert the time domain signal into a frequency domain (Frequency Domain) signal (S303), wherein the frequency domain The signal will form an analog as shown in Figure 1 or a digital spectrum pattern as shown in Figure 2, and the conversion method is a fast Fourier transform operation method, and the fast Fourier transform operation method can be used, for example, by a demodulator of a digital television receiver The Fourier transform operation unit or software program in the computer provides operation processing to convert the time-domain signal into a frequency-domain signal. In addition, the spectrum pattern displays the quality and strength information of the frequency-domain signal to further judge the received ground Whether the television broadcast signal is an effective signal can also be judged, for example, by the locking state of the automatic gain control (AGC) circuit on the hardware; Search (S302).

Next, if the frequency domain signal is an effective signal, it is judged whether the spectrum pattern contains a left-right symmetrical graphic feature with a flat bandwidth (S305). If the spectrum pattern contains the above-mentioned graphic feature, it means that the terrestrial television broadcast signal is Digital TV signal (as shown in Figure 2) (S307), then demodulate and record the terrestrial TV broadcast signal as a program frequency point (S309), and at the same time estimate the bandwidth of the digital TV signal according to the spectrum pattern It is one of the 6MHz, 7MHz or 8MHz systems, which can be used for related processes such as back-end demodulation to save time.

In addition, if the judgment result of the step (S305) is negative, that is, when the spectral pattern does not include the left-right symmetrical and flat-bandwidth graphical feature, it means that the terrestrial television broadcast signal is an analog television signal (S311) or other Interference, and then abandon the terrestrial TV broadcast signal as a program frequency point (S313). And after steps (S302), (S309) and (S313), then switch to the next frequency point (S314), and return to (S301) to continue to execute the blind scan method to detect whether there is Input for terrestrial television broadcast signals. By repeating the above steps, all terrestrial TV broadcast signals can be judged, and digital TV signals can be quickly distinguished, demodulated and recorded as program frequency points.

Please refer to FIG. 4 , which is a flow chart of another method embodiment of using spectrum analysis as a blind scan method of a digital TV broadcast receiving system according to the present invention, including: first, at the current frequency point, detect whether there is a time-domain signal pattern Presented terrestrial television broadcast signal input (S401), if the detection result is yes, then receive, and convert the time-domain signal into a frequency-domain signal (S403), wherein the frequency-domain signal will form an analog as shown in Figure 1 Or the digital frequency spectrum pattern of Fig. 2, and its conversion method is the computing method of a fast Fourier transform, and the computing method of this fast Fourier transform can for example be by the Fourier transform computing unit or software in the demodulator of digital television receiver The program provides arithmetic processing to convert the time-domain signal into the frequency-domain signal. In addition, the spectrum pattern shows the quality and strength of the frequency-domain signal to further determine whether the received terrestrial TV broadcast signal is a valid signal. In addition, the determination can also be made, for example, through the locking state of the automatic gain control (AGC) circuit on the hardware; and if the detection result of the step (S401) is negative, the search for the current frequency point is ended (S402). Next, it is judged whether a spectrum position contained in the spectrum pattern is fixed and contains a graphic feature of an image carrier or a sound carrier (S405), if the judgment result is yes, it means that the terrestrial TV broadcast signal is an analog TV signal (S407), and then give up the terrestrial TV broadcast signal as a program frequency point (S409).

On the contrary, if the judgment result of step (S405) is negative, that is, when the spectrum pattern does not include the fixed frequency spectrum position and does not contain the graphic features of the image carrier and the sound carrier, it means that the terrestrial TV broadcast signal is a digital TV signal (S411), and then demodulate and record the terrestrial TV broadcast signal as a program frequency point (S413). And after steps (S402), (S409) and (S413), then switch to the next frequency point (S414), and return to (S401) to continue to execute the blind scan method to detect whether there is Input for terrestrial television broadcast signals.

In summary, the present invention distinguishes whether the received terrestrial television broadcasting signal belongs to the digital television terrestrial broadcasting system or the analog television terrestrial broadcasting system by utilizing the difference in frequency spectrum characteristics, and does not need to perform parameter receiving attempts on each terrestrial television broadcasting signal every time. , and without waiting time-consuming times during receive attempts. In addition, since the demodulator of the digital TV receiver has a Fourier transform operation unit, it can easily convert the time-domain signal, that is, it can quickly judge whether there is a digital signal or not at the frequency point. The analog signal is used to improve the initialization execution efficiency of the digital TV.

However, the above descriptions are only detailed descriptions and drawings of specific embodiments of the present invention, and are not intended to limit the present invention. The entire scope of the present invention should be based on the scope of the patent application. Within the field of the invention, easily conceivable changes or modifications are covered by the patent scope defined by the present invention.

Claims (13)

1, a kind of method of blind scanning digital television broadcast receiving system is characterized in that, step comprises:

Receive a television broadcasting signal, wherein this television broadcasting signal is to present with time-domain signal;

Changing this television broadcasting signal is a frequency-region signal;

Whether the frequency spectrum pattern of analyzing this frequency-region signal comprises a left-right symmetric and the smooth graphic feature of bandwidth; And

When the frequency spectrum pattern of this frequency-region signal comprises the smooth graphic feature of this left-right symmetric and bandwidth, then be expressed as a digital television signal, and note down this television broadcasting signal.

2, the method for blind scanning digital television broadcast receiving system as claimed in claim 1 is characterized in that: described television broadcasting signal is a terrestrial television broadcast signal.

3, the method for blind scanning digital television broadcast receiving system as claimed in claim 1 is characterized in that: changing this time-domain signal is that (Fast FourierTransforms, operation method FFT) is carried out with a fast fourier transform for this frequency-region signal.

4, the method for blind scanning digital television broadcast receiving system as claimed in claim 3 is characterized in that: the operation method of described fast fourier transform is to provide calculation process by the fourier transform arithmetic element in the demodulator of digital television receiver.

5, the method for blind scanning digital television broadcast receiving system as claimed in claim 1 is characterized in that: but analyze the quality and the intensity of the frequency spectrum pattern picked up signal of this frequency-region signal.

6, the method for blind scanning digital television broadcast receiving system as claimed in claim 1 is characterized in that: the bandwidth that more can estimate this digital television signal according to the frequency spectrum pattern of this frequency-region signal.

7, the method for blind scanning digital television broadcast receiving system as claimed in claim 1, it is characterized in that: further comprise: when the frequency spectrum pattern of this frequency-region signal does not comprise the smooth graphic feature of this left-right symmetric and bandwidth, then be expressed as anolog TV signals, and abandon noting down this television broadcasting signal.

8, a kind of method of blind scanning digital television broadcast receiving system is characterized in that, step comprises:

Receive a television broadcasting signal, wherein this television broadcasting signal is to present with time-domain signal;

Changing this television broadcasting signal is a frequency-region signal;

Whether the frequency spectrum pattern of analyzing this frequency-region signal comprises the graphic feature that an image carrier or a sound carrier were fixed and included to a spectrum position; And

When the frequency spectrum pattern of this frequency-region signal does not comprise that this spectrum position is fixed and when not containing the graphic feature of this image carrier or this sound carrier, then is expressed as a digital television signal, and notes down this television broadcasting signal.

9, the method for blind scanning digital television broadcast receiving system as claimed in claim 8 is characterized in that: described television broadcasting signal is a terrestrial television broadcast signal.

10, the method for blind scanning digital television broadcast receiving system as claimed in claim 8 is characterized in that: changing this time-domain signal is that (FastFourier Transforms, operation method FFT) is carried out with a fast fourier transform for this frequency-region signal.

11, the method for blind scanning digital television broadcast receiving system as claimed in claim 10 is characterized in that: the operation method of described fast fourier transform is to provide calculation process by the fourier transform arithmetic element in the demodulator of digital television receiver.

12, the method for blind scanning digital television broadcast receiving system as claimed in claim 8 is characterized in that: but analyze the quality and the intensity of the frequency spectrum pattern picked up signal of this frequency-region signal.

13, the method for blind scanning digital television broadcast receiving system as claimed in claim 8, it is characterized in that: further comprise: when the frequency spectrum pattern of this frequency-region signal comprises this spectrum position and fixes and include the graphic feature of this image carrier or this sound carrier, then be expressed as anolog TV signals, and abandon noting down this television broadcasting signal.

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