KR19980045409A - Gain Control Method Using Multiple Power Control Window - Google Patents

Abstract

The present invention relates to a gain control method using multiple power control windows, and more particularly, to a received signal gain control algorithm of a digital modulation / demodulation system. The purpose is to improve the performance degradation of the receiver or loss of carrier synchronization even in a receiving environment where the environment changes suddenly and frequently. A feature of the present invention is a gain control method for controlling power by implementing primary and secondary automatic gain control circuits in a receiver of a digital modulation / demodulation communication method, and schematically controlling a primary automatic gain control circuit close to the front end of a receiver. And performing power control by precisely controlling the secondary automatic gain control circuit.

Description

Gain Control Method Using Multiple Power Control Window

The present invention devised to solve the above problems is to improve the performance degradation of the receiver or loss of carrier synchronization even in a receiving environment in which the environment changes suddenly and frequently.

A feature of the present invention for achieving the above object is a gain control method for controlling power by implementing an automatic gain control circuit of primary and secondary in a digital modulation demodulation communication receiver, the primary close to the front-end of the receiving end And roughly controlling the automatic gain control circuit and precisely controlling the secondary automatic gain control circuit to control power.

That is, the present invention seeks to solve BER performance improvement and carrier sync.loss problem by reducing the number of first AGC control as much as possible.

1 is a block diagram of automatic gain control;

2A is an input / output conversion diagram of a primary AGC for a conventional gain control method;

2B is a view illustrating a change in output of a primary AGC according to a change in an input signal according to a conventional gain control method;

2c is a control flowchart of a primary AGC according to a conventional gain control method;

3A is an input / output conversion diagram of a primary AGC according to the present invention;

3b is a change diagram of the output of the primary AGC to the input signal change according to the present invention

3C is a control flow diagram of a primary AGC in accordance with the present invention.

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

1: primary AGC

2: DAC

3: microprocessor

4: linear function block

5: secondary AGC block

6: demodulator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gain control method using multiple power control windows, and more particularly, to a received signal gain control algorithm of a digital modulation and demodulation system.

In general, the conventional Automatic Gain Control (AGC) method simply measures the strength of a received signal and compares it with a reference power strength to obtain a value corresponding to the error when it is out of the tolerance range. Is simply controlled through the DAC (Digital to Analog Converter).

1 is a block diagram of automatic gain control. A block of automatic gain control will be described with reference to FIG. 1.

It is roughly controlled by the microprocessor 3 in the primary AGC 1 (course tuning). The received signal S1 is fine tuned by the secondary AGC block 5. The constant signal S6 that has passed through the secondary AGC block 5 restores the original signal by the next demodulator 6. At this time, the secondary AGC block 5 is constituted by AGC feedback and continuously controlled so that the output S6 becomes a set value (analog control). However, the primary AGC 1 keeps the input S5 of the secondary AGC block 5 roughly within the controllable range. The microprocessor 3 monitors the signal strength of the output signal S4 of the primary AGC 1 or the output signal S6 of the secondary AGC block 5 at regular intervals, and then in case of deviation from the allowable limit. To control. The control at this time has a problem that the secondary AGC block 5 cannot be traced because it is a stepped discontinuous voltage. That is, in case of the receiver of the digital modulation / demodulation method, if the AGC is controlled frequently because the environment changes suddenly and frequently, the strength of the demodulation input signal suddenly changes frequently, so that the signal recovery capability is considerably degraded or the carrier cannot be restored instantaneously. This loss of carrier is called carrier sync.loss.

2A is an input / output conversion diagram of a primary AGC according to a conventional gain control method, and FIG. 2B is an output change diagram of a primary AGC according to a change of an input signal according to an existing gain control method, and FIG. 2C is a conventional gain control method. A control flow diagram of a primary AGC according to the method. Referring to Figs. 2a to 2c, the conventional gain control method is as follows. In the AGC algorithm of FIG. 2C of the conventional receiver, when the primary AGC output is set near the boundary as shown in 12 or 13 in FIG. 2B, when the input signal changes as 11, 12 and 13 move to 14 and 15, respectively. . At this point, 14 and 15 are outside the primary AGC tolerance and the microprocessor regains control. In this case, the digital demodulator in the back stage suddenly changes the input signal level, so that the BER (Bit Error Rate) performance is degraded or the carrier is impossible to recover, i.e., carrier sync. Loss occurs. This occurs.

In the digital modulation and demodulation communication receiver, the AGC (normal primary AGC) near the front-end of the receiving end is roughly controlled by using a microprocessor in the power control method by implementing the AGC circuit of the primary secondary or higher. In the case of course tuning, and then fine tuning the AGC (usually the secondary AGC) that follows, the power of the primary AGC control simply detects the AGC output and falls within a certain range. It was only in tracking mode.

3A is an input / output conversion diagram of the primary AGC according to the present invention, and FIG. 3B is an output variation diagram of the primary AGC according to the change of the input signal according to the present invention, and FIG. 3C is a diagram of the primary AGC according to the present invention. Control flow chart. The gain control method using the multiple power control window according to the present invention will be described with reference to FIGS. 3A to 3C as follows.

FIG. 3A shows an AGC acquisition mode that allows the AGC output to fall within the allowable range of W2 at the beginning of AGC operation and a tracking mode that controls the AGC output to be within W3 during normal operation upon receipt after AGC acquisition. The operation thereof is shown in the flowchart of FIG. 3C.

In S11, the AGC 1 is initialized by the microprocessor 3 in the initial state of the receiver. In S12, the output error of the AGC 1 is measured. In S13, it is determined whether the AGC 1 output is within the power acquisition window W2. If the output of the AGC 1 is not within the power acquisition window W2 in S13, the AGC 1 is corrected in S14 and again performed from S12. In S13, the output of the AGC 1 is in the power acquisition window W2, and in S15, the output error of the AGC 1 is measured. In S16, it is determined whether the output of the AGC 1 is in the power acquisition window W2. If the output of the AGC 1 is not within the power acquisition window W2 in S16, the AGC 1 is corrected in S17 and the process is performed again from S15. If the output of the AGC 1 in the power acquisition window (W3) in S16, it performs again from S15.

In the initial state of the receiver, the AGC 1 is initialized by the microprocessor 3, and the secondary AGC 5 adjusts the signal strength so that the next demodulator input is constant. The microprocessor 3 monitors the primary AGC 1 output at regular intervals and controls the output of the primary AGC 1 to be within W2 or W3 depending on the AGC acquisition and tracking mode. S11 to S14 are AGC acquisition modes, and S15 to S17 are AGC tracking modes.

In contrast to the conventional algorithm of the primary AGC 1 using only the AGC tracking mode, the present invention introduces two or more control modes, an AGC acquisition mode and an AGC tracking mode.

It shows how to solve this problem even if the input level changes a lot. First, the output of the primary AGC 1 in the AGC acquisition mode is located at 22, 33 and the like in FIG. 3B.

That is, within W2. These are located in the very center of the control range. However, when the input signal strength increases or decreases with 21, 22 and 23 move to 24 and 25, respectively. However, the microprocessor 3 does not control the primary AGC 1 because they are all still in the primary AGC tracking mode of W3. And they are all controlled to the appropriate intensity in the secondary AGC block 5. That is, after acquiring the primary AGC 1, the receiver performance can be improved by reducing the number of times of controlling the primary AGC 1 by the microprocessor 3 during the receiver operation.

In the conventional digital modulation and demodulation method, the reception performance is very unstable due to a decrease in reception performance in an environment where the reception state is frequently changed. However, the present invention improves the communication quality by preventing the performance degradation of the receiver or loss of carrier synchronization even in such an environment. It has the effect.

Claims (5)

In the gain control method for controlling the power by implementing the first and second automatic gain control circuit in the digital modulation demodulation communication receiver, Performing coarse control of a primary automatic gain control circuit close to the front end of the receiving end; And Gain control method using a multiple power control window, characterized in that the step of precisely controlling the secondary automatic gain control circuit to control the power. The method of claim 1, Controlling the primary automatic gain control circuit, Initializing the primary automatic gain control circuit in an initial state of the receiver; Measuring an output error of the primary automatic gain control circuit to determine whether an output of the primary automatic gain control circuit is within a first power acquisition window; In the first power acquisition window determination step, the output of the first automatic gain control circuit is not within the first power acquisition window, and the first automatic gain control is corrected and the process is performed again from the first power acquisition window determination step. step; In the step of determining the first power acquisition window, the output of the first automatic gain control circuit is in the first power acquisition window, and the output error of the first automatic gain control circuit is measured by measuring the output error of the first automatic gain control circuit. Determining whether it is within the second power acquisition window; If the output of the first automatic gain control circuit is within a second power acquisition window in the second power acquisition window determination step, performing again from the second power acquisition window determination step; And If the output of the first automatic gain control circuit is not within a second power acquisition window in the second power acquisition window determination step, modifying the first automatic gain control and performing the second power acquisition window determination step again. Gain control method using a multi-power control window, characterized in that consisting of. The method of claim 2, The gain control method using the multiple power control window, characterized in that the first power acquisition window is wider than the second power acquisition difference. The method of claim 2, Gain control method using a multiple power control window, characterized in that for controlling the primary automatic gain control circuit to control the control range with at least two power gain window. The method according to claim 1 or 2, And controlling the primary automatic gain control circuit and the secondary automatic gain control circuit using a microprocessor.