KR100260130B1 - Method for discriminating input signal of digital satellite broadcasting receiver - Google Patents

Abstract

PURPOSE: A method for determining an input signal of a digital satellite broadcasting receiver is to determine a repeater having enough signals by comparing an AGC(automatic gain control) level with an AGC reference value. CONSTITUTION: An AGC level of a selected repeater is read out and compared with an AGC reference value. In case where the AGC level is greater than the AGC reference value, A carrier restoration and a carrier lock operation is performed to check whether or not there is a signal. In case where the ACG level is smaller than the AGC reference value, an average value of the AGC level is calculated and the AGC reference value is reset according to the calculated average value. In obtaining the AGC reference value, a virtual repeater is selected and an AGC level is detected according to the selected virtual repeater. The detected ACG level is added to a predetermined constant to set the added value as the AGC reference value.

Description

Input signal discrimination method of digital satellite broadcasting receiver {METHOD FOR DISCRIMINATING INPUT SIGNAL OF DIGITAL SATELLITE BROADCASTING RECEIVER}

The present invention relates to a digital satellite broadcasting receiver, and in particular, when comparing the AGC level with the AGC reference value, the AGC level is compared with the AGC reference value by adaptively calculating and comparing the AGC reference value according to the electric field strength. An input signal discrimination method of a digital satellite broadcasting receiver capable of discriminating a signal repeater.

FIG. 1 is a block diagram of a conventional digital satellite broadcasting receiver. As shown therein, an LNB unit 110 converts a satellite broadcasting signal received from a satellite antenna 100 into a high frequency of 1 GHz band, and amplifies and outputs low noise. (LNB: Low Noise Blockdown Converter); A high frequency amplifier 120 for amplifying and outputting the output signal of the LNB 110; A tuning unit 130 for selecting a corresponding repeater from an output signal of the high frequency amplification unit 120 according to a line international language signal; An intermediate frequency amplifier 140 for amplifying the tuned intermediate frequency signal; A down-converter unit 150 for down-converting the output signal of the intermediate frequency amplifier unit 140 to a quadrature phase shift keying (QPSK) demodulated baseband signal (I, Q); An analog / digital converter (160) for sampling-converting the uncontrolled baseband signals (I, Q) of the down converter unit (150) into a digital signal; A carrier recovery unit 170 configured to grab a carrier of the currently selected repeater signal by inputting the quantized digital signal output from the analog / digital conversion unit 160; An error correction unit 180 for error correcting the output signal of the carrier recovery unit 170 and outputting a stream in a decoded packet unit; An AGC detector 190 that detects a gain level value of the selected repeater signal by inputting the output of the analog / digital converter 160; A clock recovery unit 200 for detecting an error level of I and Q signals which are output signals of the analog / digital conversion unit 160; A first loop filter unit 210 converting the AGC level of the AGC detector 190 into a direct current and applying it to the high frequency amplifier 120 and the intermediate frequency amplifier 140; A second loop filter unit 220 converting the output of the clock recovery unit into a DC voltage; A clock is generated according to the output signal of the second loop filter unit 220 and applied to the analog / digital conversion unit 160, the carrier recovery unit 170, the AGC detector 190, and the clock recovery unit 200. A clock oscillator 230; It is composed of a microprocessor 240 for the overall control of each unit.

The operation of the conventional apparatus configured as described above will be described with reference to FIGS. 2 and 3.

First, the LNB 110 converts the satellite broadcasting signal of 12 GHz band input through the satellite antenna 100 into a high frequency signal of 1 GHz band, amplifies and outputs low noise.

Then, the high frequency amplification unit 120 amplifies and outputs the output signal of the LNB unit 110, and at this time, the tuning unit 130 according to the control signal of the microprocessor 240 in the corresponding high frequency amplification signal repeater Select.

2 shows variation of AGC level (A, B) according to the input electric field, and the repeater uses an even repeater. Here, the solid line waveform indicates a repeater with a signal, and the dotted line waveform indicates a repeater without a signal.

To find a repeater with a signal, first, the microprocessor 240 sends PLL data corresponding to the tuned repeater to the station 130 through the I2C bus.

Then, the selector 130 selects the corresponding repeater, and the signal of the selected repeater is amplified by the intermediate frequency amplifier 140 and is a QPSK demodulated baseband signal through I and Q through the down converter 150. The down converter is applied to the analog / digital converter 160.

Accordingly, the analog / digital conversion unit 160 samples the input uncontrolled baseband signals I and Q and converts them into digital signals.

In the above description, the high frequency amplifier 120, the tuner 130, the intermediate frequency amplifier 140, and the down converter 150 are also referred to as a digital tuner unit 300.

At this time, the carrier recovery unit 170 receives the carrier of the currently selected repeater signal by inputting the quantized digital signal of the analog / digital conversion unit 160, and the error correction unit 180 is the carrier recovery unit 170 Error-corrected output signal to output a stream of decoded packet units.

The AGC level is detected while the output signal of the analog / digital converter 160 passes through the AGC detector 190. The detected AGC level is applied to the microprocessor 240 via the bus.

Accordingly, the microprocessor 240 compares the input AGC level with a preset AGC reference value and controls accordingly. The AGC reference value is generally set experimentally appropriate.

As a result of the comparison, if the AGC level is smaller than the AGC reference value, that is, it is determined that there is no signal like a dotted line in the A waveform of Fig. 2, and the next repeater is selected.

However, if the AGC level is greater than the AGC reference value as a result of the comparison, it is checked whether or not the clock is locked. If the clock is not turned, it is determined as a no signal and goes to the repeater selection step again to select the next repeater.

However, if the clock is locked, the carrier recovery unit 170 detects error levels of the output signals I and Q of the analog / digital conversion unit 160 and transmits the error levels to the microprocessor 240.

When the carrier recovery is performed as described above, the microprocessor 240 determines whether the carrier lock has been performed. If the carrier lock has not been performed, go to the repeater selection step and select the next repeater, and when the carrier lock has been completed, it is determined that there is a complete signal. do.

In the above description, the carrier recovery unit 170, the AGC detection unit 190, and the clock recovery unit 200 are collectively referred to as a QPSK recovery unit 400.

In addition, the clock lock check step may be omitted, and the carrier recovery step may be immediately performed.

At this time, when the signal passing through the LNB 110 is to use an amplifier (booster) while passing through the cable or the gain of the digital tuner 300 is quite large, or the electric field strength of the signal input to the receiver is large, FIG. 2. At B, the overall AGC level becomes larger than the AGC reference value.

As described above, in the conventional apparatus, when the signal passing through the L / N part is used by the amplifier (booster) through the cable or the gain of the tuner is very large, or when the electric field strength of the signal input to the receiver is large, the overall AGC level is increased. The AGC reference value is larger than the AGC reference value. In this case, even if there is no signal, there is a problem in that the overall search time and the operation are long because the presence or absence of the signal is determined only through the clock lock step or the carrier lock step.

An object of the present invention is to digitally determine the repeater with a sufficient signal simply by comparing the AGC level with the AGC reference value by calculating the AGC reference value variably according to the input field in order to solve this conventional problem The present invention provides a method for discriminating an input signal of a satellite broadcasting receiver.

1 is a block diagram of a conventional digital satellite broadcasting receiver.

2 is a view showing AGC level variation according to an input electric field.

3 is a flowchart illustrating an input signal discrimination operation of a conventional digital satellite broadcasting receiver.

4 is a flowchart illustrating an input signal discrimination operation of the digital satellite broadcasting receiver of the present invention.

5 is a view showing a variation of the AGC reference value according to the input field in the present invention.

6 is a diagram showing an average AGC level according to the number of signaled repeaters.

***** Description of the symbols for the main parts of the drawings *****

100: satellite antenna 110: El N Vibu

120: high frequency amplifier 130: station

140: intermediate frequency amplifier 150: down converter

160: analog / digital conversion unit 170: carrier recovery unit

180: error correction 190: AGC detector

200: clock recovery unit 210: first loop filter unit

220: second loop filter unit 230: clock oscillation unit

240 microprocessor

In order to achieve the object of the present invention, an input signal discrimination method of a digital satellite broadcasting receiver includes: a first step of selecting a repeater and reading an AGC level according thereto and comparing it with an AGC reference value; A second step of determining whether a signal is present through a carrier recovery and carrier lock process if the AGC level is greater than the AGC reference value as a result of the comparison of the above steps; If the AGC level is less than the AGC reference value as a result of the determination in the first step, a third step of calculating the average value of the AGC level and resetting the AGC reference value accordingly is performed.

Hereinafter, with reference to the accompanying drawings, the operation and effect of the present invention will be described in detail.

First, the device configuration is the same as the conventional configuration shown in FIG. Therefore, the process of judging the presence or absence of an input signal will be described.

First, the total AGC register for adding the AGC level of each repeater and the count register for counting to increase by 1 for each repeater selection are initialized to zero.

The virtual repeater (# 0) is selected, and the frequency corresponding to the virtual repeater is generally included in the LNB amplification band, and the AGC level value is equal to that of the other repeater.

The virtual repeater selection method is selected in the same manner as the other repeater selection, in which the PEL data corresponding to the frequency is transmitted by the microprocessor 240 to the tuner 130 through the bus.

When the virtual repeater is selected as described above, the AGC detector 190 reads the AGC level and stores it in the register. At this time, as described above, the value of the register, that is, the AGC level has a non-numeric value regardless of the other repeater, regardless of the electric field strength.

The AGC reference value for comparison with the AGC level is set. An appropriate constant C1 is added to the detected AGC level value to set the AGC reference value.

This sets the AGC reference value between the signal repeater level and the signal repeater level.

And the actual repeater selection and AGC level detection operation is performed to compare the detected AGC level with the set AGC reference value.

As a result of the comparison, if the AGC level is smaller than the AGC reference value, the AGC level is added to the total AGC register, and the number is increased to the count register for determining whether all repeaters have been selected once by recognizing it every time the repeater is selected.

If the value of the count register is less than the total number of repeaters, it is determined that there is no signal and the repeater selection process is repeated.

However, if the value of the count register is greater than or equal to the total number of repeaters, all repeaters are selected once. Therefore, the AGC level average is calculated to set a more accurate AGC reference value.

The AGC level average is obtained by dividing the count value by the value of the total AGC register.

When the AGC level average is calculated in this manner, the appropriate constant C2 is subtracted from the AGC level average value, reset to the AGC reference value, and then fed back to the repeater selection step.

The reset AGC reference value is the same as that shown in Fig. 5, which is naturally a value between the signaled repeater and the signalless repeater, which becomes a more clear and accurate AGC reference value.

At this time, the constant C1 is set not to be greater than the level value of the repeater signaled at the AGC level of the virtual repeater.

And the average value is as shown in Figure 6, (6) when all the repeaters have a signal, (5) when there is a signal other than one repeater, (4) is a signal other than the repeater (3) is when there are signals except for 3 repeaters, (2) is when there are signals except for 4 repeaters, and (1) is when only one repeater has a signal. The AGC mean value is shown.

The constant C2 is necessary here to prevent the AGC reference value from being greater than the signaled repeater when all repeaters are signaled.

On the other hand, if the AGC level is greater than the AGC reference value, the same operation as in the prior art. In other words, it is checked whether the clock is locked, and if it is not, the signal is judged as no signal and the control unit selects the next repeater.

However, if the clock is locked, the carrier recovery unit 170 detects error levels of the outputs I and Q of the analog / digital conversion unit 160 and transmits the error levels to the microprocessor 240.

When the carrier recovery is performed as described above, the microprocessor 240 determines whether the carrier lock has been performed. If the carrier lock has not been performed, go to the repeater selection step and select the next repeater, and when the carrier lock has been completed, it is determined that there is a complete signal. do.

As described in detail above, the present invention selects a virtual repeater, adds a predetermined constant to the AGC level accordingly, and sets an initial AGC reference value so that an AGC reference value proportional to the electric field strength can be set to determine whether there is an accurate signal. If the AGC level is smaller than the AGC reference value, the AGC level is added to the total AGC register, the average value of the total AGC level is calculated and subtracted to a predetermined constant to reset the AGC reference value to reduce external noise or frequency interference. Overlapping the virtual repeater has an effect that can prevent the error in the AGC reference value setting.

Claims (2)

Selecting a repeater and reading an automatic gain control (AGC) level accordingly and comparing it to an automatic gain control reference value; A second step of determining whether there is a signal through a carrier recovery and a carrier lock process if the automatic gain control level is greater than the automatic gain control reference value as a result of the comparison of the steps; Digital satellite broadcasting comprising the third step of calculating the average value of the automatic gain control level if the automatic gain control level is less than the automatic gain control reference value as a result of the determination in the first step. Input signal discrimination method of receiver. The method of claim 1, wherein the automatic gain control reference value of the first step comprises: selecting a virtual repeater; Detecting an automatic gain control level according to the virtual repeater selected in the step; And a predetermined constant is added to the automatic gain control level detected in the step to set the automatic gain control reference value.

Images