CN107370971A - Signal receiving end of digital television and signal processing method thereof - Google Patents

Abstract

The invention provides a signal receiving end of a digital television, comprising: an analog-to-digital converter for converting an input signal from an analog format to a digital format, the input signal including a target signal and an interference signal; a digital gain control circuit coupled to the adc for adjusting an amplitude of the target signal according to a gain value; a detection module, coupled to the digital gain control circuit, for detecting a variation of the gain value to generate a detection value; and a control unit coupled to the digital gain control circuit for determining a gain setting parameter according to the detection value; wherein the digital gain control circuit further updates the gain value according to the gain value setting parameter.

Description

Signal Receiver of Digital TV and Its Signal Processing Method

technical field

The present invention relates to a digital automatic gain control (DAGC), in particular to a digital automatic gain control for adaptively adjusting a gain step value.

Background technique

When a target signal is transmitted on a certain channel, it sometimes suffers from the influence of adjacent channels, and this kind of influence is called adjacent channel interference (ACI). For example, before the signal enters the analog-to-digital converter (analog-to-digital converter, ADC), it usually goes through the automatic gain control (autogain control, AGC) to adjust the amplitude (that is, the energy level) to avoid excessive signal amplitude The analog-to-digital converter is saturated, or the amplitude is too small to cause insufficient data. When the amplitude of the adjacent frequency signal of a target signal is too much larger than the target signal, the automatic gain control circuit will adjust the target signal and its adjacent frequency signal with a smaller gain value, so that the amplitude of the target signal may be controlled by the automatic gain control The circuit adjustment is too small; in this case, after the analog-to-digital converter, the target signal must be adjusted by the digital automatic gain control to reach the appropriate amplitude for subsequent circuit processing. In the known method, the digital automatic gain control circuit adjusts the gain value with a fixed step size; the disadvantage of this method is that the gain value cannot be adjusted in real time as the adjacent channel interference changes. In an environment where the adjacent frequency interference sometimes changes drastically (fast and large) and sometimes slowly (slow or small), the digital automatic gain control circuit cannot adjust the amplitude of the target signal in real time according to the current environment, which affects the circuit. operational efficiency.

Contents of the invention

In view of the deficiencies in the prior art, an object of the present invention is to provide a digital TV signal receiving end and its signal processing method, so as to adaptively adjust the gain value according to the adjacent channel interference.

The present invention proposes a signal receiving end of a digital television, comprising: an analog-to-digital converter for converting an input signal from an analog format to a digital format, and the input signal includes a target signal and an interference signal; a digital gain control A circuit, coupled to the analog-to-digital converter, used to adjust an amplitude of the target signal according to a gain value; a detection module, coupled to the digital gain control circuit, used to detect a variation of the gain value to generate a detection value; and a control unit coupled to the digital gain control circuit for determining a gain setting parameter according to the detected value; wherein the digital gain control circuit further updates the gain value according to the gain setting parameter.

The present invention also proposes a signal processing method for a digital television receiver, comprising: converting an input signal from an analog format to a digital format, the input signal including a target signal and an interference signal; adjusting a gain value of the target signal amplitude; detecting a variation of the gain value to generate a detection value; determining a gain setting parameter according to the detection value; and updating the gain value according to the gain setting parameter.

The digital TV signal receiving end and its signal processing method of the present invention can adaptively adjust the gain value according to the adjacent channel interference, so that the TV system can be adaptively adjusted with the change degree of the adjacent channel interference, so as to improve the overall performance. Compared with the known technology, the gain value of the present invention can reflect the change degree of adjacent channel interference, that is, the system will consider the current channel environment for signal processing.

Description of drawings

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is the functional block diagram of the signal receiving terminal of digital television of the present invention;

Fig. 2 is the flow chart of an embodiment of the signal processing method of the digital TV receiver of the present invention; And

Fig. 3 is a relationship diagram between the step value u and the detection value var in the present invention.

Explanation of component numbers in the figure:

100 Digital TV signal receiving end

110 automatic gain control circuit

120 Analog to Digital Converters

130 filters

140 digital automatic gain control circuit

150 interference detection module

160 control circuit

Steps from S210 to S260

detailed description

The description content of the present invention includes the signal receiving end of the digital TV and its signal processing method. Under the premise that the implementation is possible, those skilled in the art can select equivalent elements or steps according to the description content of this manual to realize the present invention. The invention, that is, the implementation of the present invention is not limited to the embodiments described below.

FIG. 1 is a functional block diagram of a signal receiving end of a digital television of the present invention. The signal receiving end 100 of digital television is for example the television receiving end of terrestrial digital multimedia broadcasting (Digital Terrestrial Multimedia Broadcast, DTMB), and the signal receiving end 100 of digital television may comprise automatic gain control circuit 110, analog-to-digital converter 120, filter 130 , a digital automatic gain control circuit 140 , an interference detection module 150 and a control circuit 160 . The automatic gain control circuit 110 is used to receive the analog input signal S(t) (t is a time parameter of continuous time) and adjust the amplitude of the input signal S(t), and the analog-to-digital converter 120 is used to convert the input signal S after the amplitude adjustment '(t) is converted into an input signal S(n) in digital format (n is a time parameter of discrete time), wherein the input signal S(n) at least includes the target signal x(n) carrying video and audio data in the digital television system. The filter 130 is used to filter out the adjacent frequency interference in the input signal S(n) to leave the target signal x(n), more specifically, the filter 130 is actually a band-pass filter, which is used to filter out the input In another embodiment, the filter 130 can also be a low-pass filter or a high-pass filter. The digital automatic gain control circuit 140 is used to readjust the amplitude of the target signal x(n) (in the digital domain, it represents the range of binary values distributed by the target signal x(n)), so that the subsequent stage circuit (such as the demodulation circuit etc., not shown in the figure) to process the adjusted target signal x'(n) with better amplitude.

The digital automatic gain control circuit 140 adjusts the amplitude of the target signal by multiplying the target signal x(n) by a gain value w. In one embodiment, the gain value w used by the digital automatic gain control circuit 140 can be obtained based on the following algorithm:

x'(n)=w(n) x(n) (1)

w(n+1)=w(n)+u·e(n)·x(n) (2)

e(n)=y(n)-x'(n) (3)

Among them, u is the step value, setting parameters for a gain value; e(n) is the difference between the adjusted target signal (w(n) x(n)) and the ideal value y(n), according to the equation (1)～(3), when the difference e(n) after the nth adjustment is larger, or the adjusted target signal amplitude is larger, the gain value w of the (n+1)th time will also be larger . However, the aforementioned equations (1)-(3) are just an example, and the present invention is not limited thereto. As long as the above-mentioned goal that the greater the difference is, or the greater the signal amplitude is, the next gain value w will be greater, it falls within the scope of the present invention. Please note that the signal in this embodiment is a real number (real), so formula (2) is used to calculate the gain value w. If the signal is a complex number (complex), formula (2) needs to be modified into formula (4):

w(n+1)=w(n)+u e(n) x(n) ^* (4)

In addition, since the adjacent channel interference may change sharply and sometimes slowly, the gain value w should have a faster adjustment speed when the adjacent channel interference changes sharply, and it should remain stable when the adjacent channel interference changes slowly. In this way, the digital automatic gain The control circuit 140 will not be too late to adjust the amplitude of the adjusted target signal x'(n) to the ideal value when the adjacent channel interference changes rapidly, or cause the adjusted target signal x'(n) to be adjusted when the adjacent channel interference changes slowly. The amplitude fluctuation of n) is too large to make the adjusted signal more unstable.

To achieve the aforementioned purpose, the digital TV signal receiving end 100 further includes an interference detection module 150 for detecting adjacent channel interference, which is coupled to the digital automatic gain control circuit 140 and generates a detection value var according to the change of the gain value w. As mentioned above, since the automatic gain control circuit 110 will reduce the amplitude of the input signal S(t) to avoid saturation of the analog-to-digital converter 120 when large adjacent frequency interference exists, at this time, the digital automatic gain of the subsequent stage The control circuit 140 must relatively increase the target signal x(n) with a relatively large gain value w; on the contrary, when the adjacent channel interference is small, the gain value w used by the digital automatic gain control circuit 140 is also relatively small . That is to say, the gain value w is positively correlated with the magnitude of the adjacent-channel interference, so the change degree of the adjacent-channel interference can be known by analyzing the gain value w. In one embodiment, the interference detection module 150 calculates a variance of the gain value w to obtain a detected value var of adjacent channel interference. After having the information about the adjacent channel interference, this information can be used to adjust the gain value w of the digital automatic gain control circuit 140, so the digital automatic gain control circuit 140 can adjust the gain value w more immediately to reflect the adjacent frequency in the channel. frequency interference.

The digital TV signal receiving end 100 further includes a control circuit 160 coupled to the digital automatic gain control circuit 140 and the interference detection module 150 for generating the step value u required by the digital automatic gain control circuit 140 according to the detection value var. The control circuit 160 is, for example, the central processing unit, microcontroller or microprocessor of the digital television system to which the signal receiving end 100 of the digital television belongs, and it calculates the step value u according to the following equation:

u=b[1-exp(-var')] (5)

var'=a×(var/N) ^r (6)

Wherein, the values a, b, N and r can be set according to the signal transmission environment and/or the requirements of the digital TV system. Then the control circuit 160 outputs the calculated step value u to the digital automatic gain control circuit 140, and the digital automatic gain control circuit 140 can obtain a gain value w that can reflect the degree of adjacent channel interference according to equation (2). The aforementioned equations (5) and (6) are just an example, and the present invention is not limited thereto. As long as it can dynamically provide a larger step value u when the detected value var of adjacent channel interference is large, and dynamically provide a smaller step value u when the detected value var of adjacent channel interference is small, it is within the scope of the present invention scope.

Please note that in one embodiment, the interference detection module 150 is implemented by hardware, which has the advantage of fast calculation; in different embodiments, the interference detection module 150 is implemented by software and/or firmware, which has the advantage of saving Advantages such as circuit area and parameters can be set flexibly. When implemented with software and/or firmware, the interference detection module 150 is stored in the system memory (not shown) of the digital television system in the form of program code (programcode), and the control circuit 160 reads the program code from the system memory and Execution; therefore, when the interference detection module 150 is implemented with software and/or firmware, it can be regarded as a functional module of the control circuit 160 for detecting adjacent frequency interference, and the control circuit 160 executes the set of program codes to realize the The function of the function module.

Please refer to FIG. 2 , which is a flow chart of an embodiment of the signal processing method of the digital TV receiving end of the present invention. In addition to the aforementioned digital TV signal receiving end 100, the present invention also correspondingly describes a signal processing method of the digital TV receiving end. This method is carried out by the signal receiving end 100 of the aforementioned digital television or its equivalent device, and comprises the following steps:

Step S210: Convert the input signal from analog format to digital format. Because of the limitations of the analog-to-digital converter, the input signal must be adjusted by the automatic gain control circuit before conversion to avoid saturation of the analog-to-digital converter; however, when the amplitude of the adjacent frequency interference in the input signal is too large, the digital TV system The amplitude of the target signal of concern (included in the input signal) may become too small after being adjusted by the automatic gain control circuit, which is not conducive to the operation of the subsequent circuit;

Step S220: Filter out the adjacent channel interference of the input signal to generate a target signal. This step can use a band-pass filter, low-pass filter or high-pass filter to filter out the adjacent frequency interference components in the input signal, leaving only the target signal;

Step S230: Adjust the amplitude of the target signal according to a gain value, so that the adjusted target signal has a more appropriate amplitude to facilitate subsequent circuit processing;

Step S240: Detect the adjacent channel interference of the input signal to generate a detection value. In order to make the step value reflect the change of the adjacent channel interference, this step first detects the adjacent channel interference and generates a detection value. As mentioned above, the gain value of the target signal adjusted in step S240 is positively correlated with the size of the adjacent channel interference. Therefore, in one embodiment, this step can be obtained by calculating the variation of the gain value to obtain the detection value, the detection value reflects the change degree of adjacent channel interference; and

Step S250: Determine a step value according to the detected value. After having the detection value that can reverse the change of adjacent frequency interference, the step value used in step S230 can be adjusted according to the detection value (for example, according to equations (5) and (6)), so that the gain value can be adjusted with Adjust accordingly for changes in adjacent channel interference. That is to say, the step value in equation (2) is adaptively and dynamically adjusted according to the adjacent channel interference, rather than a fixed value.

Step S260: Update the gain value according to the step value. The target signal whose amplitude is too small can be amplified by multiplying the gain value in the digital domain. In one embodiment, the gain value is shown in equations (1)-(3)).

The above steps S210-S260 will be repeatedly executed to process more input signals. Because the size of the gain value is substantially related to the adjacent frequency interference, the present invention can adjust the amplitude of the target signal more adaptively; that is to say, when the adjacent frequency interference changes sharply, the detection value generated in step S240 is also relatively large , and then a larger step value can be obtained in step S250, and the gain value updated in step S260 can quickly reflect the change of the actual transmission channel; on the contrary, when the adjacent channel interference changes slowly, the detection value generated in step S240 is relatively If the value is smaller, a smaller step value can be obtained in step S250, and the updated gain value in step S260 changes slowly and smoothly, so as to avoid too much calculation causing system instability or excessively increasing the system burden.

Fig. 3 is a diagram of the relationship between the step value u and the detection value var in the present invention. Because the circuit often approximates the value to the power of 2 in order to reduce the complexity, the vertical axis in the figure is approximated to the power of 2 with the step value u, and the negative value of the power of 2 presented. It can be seen from the figure that when the adjacent frequency interference is small (for example, the detection value var is between 10 and 15), the corresponding step value u is between 2 ^-9 and 2 ^-8 ; and when the adjacent frequency interference is large (For example, the detection value var is between 45 and 55), and the corresponding step value u is between 2 ⁻³ and 2 ⁻² . The dotted line in the figure indicates the corresponding relationship without approximation for comparison.

Since those skilled in the art can understand the implementation details and changes of the method invention in FIG. 2 through the description of the device invention in FIG. 1, although the embodiments of the present invention are as described above, these embodiments are not intended to To limit the present invention, those skilled in the art can make changes to the technical features of the present invention according to the explicit or implicit content of the present invention. All such changes may belong to the scope of patent protection sought by the present invention. In other words, this The scope of patent protection for an invention shall be defined by the claims in this specification.

Claims (15)

1. A signal receiving end of a digital television, comprising: An analog-to-digital converter for converting an input signal from an analog format to a digital format, the input signal including a target signal and an interference signal; a digital gain control circuit, coupled to the analog-to-digital converter, for adjusting an amplitude of the target signal according to a gain value; a detection module, coupled to the digital gain control circuit, used to detect a variation of the gain value to generate a detection value; and A control unit, coupled to the digital gain control circuit, is used to determine a gain value setting parameter according to the detected value; wherein The digital gain control circuit further updates the gain value according to the gain value setting parameter. 2. The signal receiving terminal of digital television as claimed in claim 1, further comprising: A filter, coupled between the analog-to-digital converter and the digital gain control circuit, is used to filter out the interference signal to generate the target signal. 3. The signal receiving terminal of digital television as claimed in claim 2, wherein the interference signal is an adjacent frequency interference signal of the target signal, and the filter is one of a band-pass filter or a low-pass filter one. 4. The signal receiving end of a digital television as claimed in claim 1, wherein the detection value is related to the change degree of the interference signal. 5. The signal receiving terminal of digital TV as claimed in claim 1, wherein the detection module is a functional module of the control unit, which is composed of a set of program codes, and the control unit executes the set of program codes to Generate the detection value. 6. The signal receiving end of a digital television as claimed in claim 1, wherein the digital gain control circuit further updates the gain value according to the amplitude. 7. The signal receiving end of a digital TV according to claim 1, wherein the digital gain control circuit further updates the gain value according to a difference between the adjusted target signal and an ideal value. 8. A signal processing method for a digital television receiver, comprising: converting an input signal from an analog format to a digital format, the input signal including a target signal and an interference signal; adjusting an amplitude of the target signal according to a gain value; Detecting a variation of the gain value to generate a detection value; determining a gain value setting parameter according to the detection value; and The gain value is updated according to the gain value setting parameter. 9. The signal processing method of the digital television receiver as claimed in claim 8, further comprising: The input signal is filtered to remove the interference signal to generate the target signal. 10. The signal processing method of the digital TV receiver according to claim 8, wherein the detection value is related to the variation degree of the interference signal. 11. The signal processing method of the digital television receiver as claimed in claim 8, wherein the step of determining the gain value setting parameter according to the detected value comprises: When the detected value is larger, determine the gain value setting parameter with a larger absolute value; and When the detection value is smaller, the gain value setting parameter with a smaller absolute value is determined. 12. The signal processing method of the digital television receiver as claimed in claim 8, further comprising: The gain value is updated according to the amplitude. 13. The signal processing method of the digital TV receiving end as claimed in claim 12, wherein the step of updating the gain value according to the amplitude comprises: When the amplitude is larger, determining the gain value with a larger absolute value; and When the amplitude is small, the gain value with a small absolute value is determined. 14. The signal processing method of the digital television receiver as claimed in claim 8, further comprising: The gain value is updated according to a difference between the adjusted target signal and an ideal value. 15. The signal processing method of the digital TV receiving end as claimed in claim 14, wherein the step of updating the gain value according to the difference between the adjusted target signal and the ideal value comprises: When the difference is larger, determining the gain value with a larger absolute value; and When the difference is smaller, the gain value with a smaller absolute value is determined.