JP3333102B2 - Automatic gain control device for digital receiver. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic gain control (AGC) device for a digital receiver, and more particularly to a code constellation of various multi-level modulations due to the addition of noise, resulting in an error in code identification determination. The present invention relates to a device that suppresses the occurrence of blemishes.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a conventional automatic gain control device for digital reception, and FIG. 4 is a diagram showing an example of a code arrangement of a 16QAM wave. For example, FIG.
As shown in (1), a modulated signal of 16 QAM (quadrature amplitude modulation) is received, and the received signal is band-limited by a high frequency unit (RF) 1 and input to a demodulator 3 via a variable gain amplifier 2. In the demodulator 3, the phase of the input signal is detected by 90 °.
Quadrature transformation is performed on two reference carriers having different phases to form an in-phase component I and a quadrature component Q. The decoder 4 identifies the amplitude of each of the orthogonally transformed signals, makes a code identification determination as to which of the 16 codes has been received, and decodes the data based on this determination. Power calculator 5
Calculates the power from the orthogonally transformed signal of the demodulator 3. The error calculator 6 compares the power obtained by the power calculator 5 with the reference power value and calculates the difference as a power error. Smoother 7
In the above, the power error of the error calculator 6 is smoothed, and based on the result, the amplification of the variable gain amplifier 2 is controlled so that the output is performed at a constant power. Here, the variable gain amplifier 2, the power calculator 5, the error calculator 6, and the smoothing device 7 constitute an automatic gain controller 8.

[0003]

FIG. 5 is a diagram showing an example of a code arrangement of a 16QAM wave when a received signal is affected by noise. As shown in the figure, when the received signal is affected by noise, the code position fluctuates in a certain area around the code position at the time of ideal reception without noise. Further, an actual receiver is provided with the automatic gain control device 8 in order to keep the power value of a received signal constant. As shown in FIG. 4, the automatic gain control device 8 is provided on the assumption that a signal is received in a code arrangement in an ideal state without noise.

FIG. 6 is a diagram showing an example of a code arrangement of a 16QAM wave when the automatic gain control device 8 operates, in which the received signal is affected by noise. When noise is added to the received signal, the power of the modulated signal is suppressed by the amount of the noise power by the automatic gain control device 8 as shown in the figure, and the code arrangement shrinks. For this reason, there is a problem in that a code of a certain event enters a position of a code of another event, thereby causing an error in code identification determination. In particular, in a multi-level modulation scheme having a high transmission capacity, an error occurs in discrimination determination of many codes under the influence of a little noise.

Accordingly, the present invention has been made in view of the above-described problems, and therefore, it is possible to prevent a code arrangement from being contracted by automatic gain control due to noise, to reduce errors in identification determination, and to achieve an automatic decoding of a digital receiver capable of performing correct decoding. It is an object to provide a gain control device.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to receive a multi-level modulated digital signal included in a burst at a fixed interval, and to compare a received power with a reference power value. In an automatic gain control device for digital reception that controls the amplification degree of a received signal using the difference as error power, a signal determiner that determines a no-signal state between bursts, and a determination result of the signal determination unit and the received power are input. A noise power detector that detects noise power during a no-signal state between bursts,
Adding a noise power obtained by the noise power detector to the reference power value to obtain a new reference power value and controlling a degree of amplification of a received signal by using a difference between the received power and the new reference power value as error power; And an adder. By this means, it is possible to prevent the code arrangement from being contracted due to the automatic gain control due to noise, to reduce errors in identification determination, and to perform correct decoding.

[0007] The noise power detector smoothes the detected noise power. By this means, instantaneous changes can be eliminated.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an example of an automatic gain control device for digital reception according to the present invention.
FIG. 3 is a diagram showing an example of transmitting one continuous digital modulated signal called a burst. As shown in FIG. 1, components different from those in FIG. 3 in the automatic gain control device 8 are a signal determiner 9, a noise power detector 10, and an adder 11. First, the signal determiner 9 determines a portion where the burst is transmitted and a portion where the burst is not transmitted based on the processing result of the demodulator 3. The noise power detector 10 receives the power calculated for the automatic gain control by the power calculator 5 and the processing result from the signal determiner 9, and no burst is transmitted among the powers calculated for the automatic gain control. The power of the part, ie the noise power of the noise part during the no-signal state between bursts, is detected. Then, this noise power is smoothed. This is to remove an instantaneous change. The calculator 11 adds the smoothed power of the noise portion to the above-described reference power value for automatic gain control to form a new reference power value.

The error calculator 6 calculates the above-described power error using the new reference power value. For this reason, the reference power value is increased by the power of the noise, and the signal power is evaluated to be smaller by the noise power than in the related art, and the code arrangement does not shrink as shown in FIG. That is, since the nature of noise is additive, individual addition of power values can be performed using this property as described above.

In the above example, 16QAM has been described. However, the present invention is not limited to this and can be applied to a digital receiver using various multi-level modulation codes.

[0011]

As described above, according to the present invention, the contraction of the code arrangement due to the automatic gain control due to the noise error is eliminated, the error due to the code identification judgment is reduced, and the reception quality is improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an automatic gain control device for a digital receiver according to the present invention.

FIG. 2 is a diagram illustrating an example of transmitting one continuous digital modulated signal called a burst.

FIG. 3 is a diagram illustrating a conventional automatic gain control device of a digital receiver.

FIG. 4 is a diagram illustrating an example of a code arrangement of a 16QAM wave.

FIG. 5 shows 16QAM when a received signal is affected by noise.
It is a figure which shows the example of a code arrangement | positioning of a wave.

FIG. 6 is a diagram showing an example of a 16QAM wave code arrangement when an automatic gain control device 8 operates, in which a received signal is affected by noise.

[Explanation of symbols]

 2 Variable gain amplifier 3 Demodulator 4 Decoder 5 Power calculator 6 Error calculator 7 Smoothing device 8 Automatic gain controller 9 Signal determiner 10 Noise power detector 11 Adder

Continuation of the front page (56) References JP-A-4-167629 (JP, A) JP-A-51-130267 (JP, A) JP-A-10-65750 (JP, A) JP-A-57-131152 (JP, A) JP-A-63-287235 (JP, A) JP-A-57-188163 (JP, A) JP-A-60-145713 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H04L 27/00-27/38

Claims (2)

(57) [Claims] 1. A digital receiver for receiving a digital signal included in a burst at a constant interval and modulated by multi-level modulation, and controlling the amplification of the received signal using the difference between the received power and a reference power value as error power. An automatic gain control device, comprising: a signal determiner for determining a no-signal state between bursts; and a noise power for detecting a noise power during a no-signal state between bursts by inputting the determination result of the signal determiner and the reception power. A detector, adding a noise power obtained by the noise power detector to the reference power value to obtain a new reference power value, and amplifying a received signal by using a difference between the received power and the new reference power value as error power. An automatic gain control device for digital reception, comprising an adder for controlling the degree. 2. The automatic gain control apparatus for digital reception according to claim 1, wherein said noise power detector smoothes the detected noise power.