WO2005004341A1

WO2005004341A1 - Digital signal reception device

Info

Publication number: WO2005004341A1
Application number: PCT/JP2004/009294
Authority: WO
Inventors: Masami Takigawa; Hiroaki Ozeki; Hideki Ouchi; Akira Ito
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2003-07-07
Filing date: 2004-06-24
Publication date: 2005-01-13
Also published as: JP2005033247A; CN100411311C; CN1698276A

Abstract

A digital signal reception device includes: a tuner (1) having a terminal (1a) and an RFAGC amplifier; a filter (2); an IFAGC amplifier (3) for amplifying the signal which has passed through the filter (2); a mixer (4) for converting the signal amplified by the IFAGC amplifier (3) to a signal of lower frequency; a local oscillator (5); a demodulator (6); a level detector (7) for detecting the level of an output signal from the mixer (4); a gain controller (9) which receives the signal from the level detector (7) and controls the gain of the RFAGC amplifier and the gain of the IFAGC amplifier (3) independently from each other; and a microcomputer (10) which receives the signal from the level detector (7) and outputs channel selection data of the target channel to the tuner (1) by a channel selection instruction issued from a host system (11) and a signal of the reproduction transmission hierarchy. Thus, it is possible to stably receive a digital broadcast signal.

Description

Specification

Digital signal receiver Technical field

The present invention relates to a digital signal receiver for receiving a digitally modulated broadcast signal. Background art

In recent years, digitalization of television broadcasting has been progressing. This digitized broadcast signal is multiplexed with broadcast signals modulated by various modulation methods. Thus, a plurality of programs can be transmitted on one channel.

As a receiver for receiving the digitized broadcast signal, there is a receiver called a single tuner. This single tuner has one local oscillator, which is used to convert a high-frequency signal (hereinafter, referred to as an RF signal) as the broadcast signal into an intermediate frequency signal (hereinafter, referred to as an IF signal). I have. The advantage of a single tuner is that, unlike a double tuner having two local oscillators, no phase noise leaks from the two local oscillators occurs, and therefore, the bit error rate of the received signal does not deteriorate. That is, the reception interference due to the phase noise does not occur.

On the other hand, in a broadcast signal, a broadcast signal (adjacent channel signal) having an intensity equal to or higher than the received signal level appears relatively close to the frequency. As a result, the interference characteristics (cross-modulation characteristics) from adjacent channel signals were not stable, and as a result, there was a problem that it was difficult to receive digital broadcast signals stably. Disclosure of the invention

The digital signal receiver of the present invention controls the gain of the RFAGC amplifier and the gain of the IFAGC amplifier independently while receiving the signal from the level detector. A gain controller; and a microcomputer that receives a signal from the level detector and outputs a channel selection data of a target channel to a tuner in response to a channel selection command and a reproduction transmission layer signal output from a host system. Therefore, it is possible to move the adjacent interference characteristic curve of the received signal to the optimum area in view of the received electric field strength value, and as a result, it is possible to receive the digital broadcast signal stably. Brief Description of Drawings

FIG. 1 is a block diagram of a digital signal receiver according to Embodiment 1 of the present invention.

Figure 2 shows the relationship between input electric field strength and AGC gain attenuation.

3A and 3B are diagrams showing the relationship between input electric field strength and AGC gain attenuation.

Fig. 4 is a graph showing the relationship between the input electric field strength and the AGC gain attenuation showing the adjacent interference characteristics of the tuner.

FIG. 5 is a block diagram showing a configuration of a digital signal receiver according to Embodiment 2 of the present invention.

FIG. 6 is a diagram showing an example of a delay point set value according to a modulation method, showing a relationship between an input electric field strength and an AGC gain attenuation.

FIG. 7 is a correlation diagram between the moving speed and the Dobler frequency.

FIG. 8 is a diagram showing an example of a delay point set value according to a reception channel frequency, showing a relationship between an input electric field strength and an AGC gain attenuation. BEST MODE FOR CARRYING OUT THE INVENTION

The digital signal receiver of the present invention has a terminal for inputting a received signal, and an RFAGC amplifier for amplifying the received signal input from the terminal, and receives a target channel from the received signal amplified by the RFAGC amplifier. A tuner that selects a signal and converts it to an intermediate frequency signal, a filter that selectively passes the intermediate frequency signal, an IFAGC amplifier that amplifies the signal that has passed through this filter, and an IF AGC amplifier Signal with a frequency lower than the frequency of the signal A local oscillator that generates a local oscillation frequency signal input to the mixer, a demodulator that digitally demodulates an output signal output from the mixer and outputs the demodulated signal to a host system, and detects a level of the output signal. A level detector that receives a signal from the level detector, a gain controller that independently controls the gains of the RFAGC amplifier and the IFAGC amplifier, and a signal that is input from the level detector. A microcomputer for outputting a channel selection command of a target channel to the tuner in response to a channel selection command output from the host system and a signal of a reproduction transmission layer. The characteristic force can be moved to the optimum region in view of the received electric field strength value, and as a result, the digital broadcast signal can be stabilized. Can be received.

Further, the digital signal receiver of the present invention further includes a modulation state detector. This allows the modulation state detector to perform gain control according to the modulation scheme of the received signal, so that stable reception can be performed regardless of the modulation scheme.

Hereinafter, a digital signal receiver according to the present invention will be described with reference to the drawings according to embodiments.

(Embodiment 1)

An embodiment will be described with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the digital signal receiver according to the first embodiment.

The microcomputer 10 sets channel selection data to the tuner 1 in response to a channel selection command from the host system 11. The tuner 1 is provided with a terminal 1a for inputting a received signal, and a received signal input from an antenna (not shown) or the like is supplied with an RFAGC amplifier (not shown) built into the tuner 1 via this terminal. ) Is entered. The target channel of the received signal is selected by the tuner 1, passed through the filter 2, the IFAGC amplifier 3, and the mixer 4, input to the demodulator 6, digitally demodulated by the demodulator 6, and the demodulated signal is output. The data is output to the host system 11 as reproduction data. Note that a local oscillator 5 is connected to the mixer 4, and an IF signal amplified by the IFAGC amplifier 3 and a constant frequency signal output from the local oscillator 5 Are mixed in the mixer 4. The level detector 7 detects the level of the signal input to the demodulator 6 and inputs the detected data to the gain controller 9 and the microcomputer 10. With this microcomputer 10, the gain controller 9 keeps the gain of the IFAGC amplifier 3 constant, and sets the operation start point (hereinafter, referred to as a delay point) of the gain control of the RF AGC amplifier. As a result, the gain distribution of the RFAGC amplifier and the IFAGC amplifier 3 is determined. That is, the gain of the RF AGC amplifier is controlled by the AGC loop via the level detector 7 and the gain controller 9 so as to keep the input level to the demodulator 6 constant. This will be further described with reference to FIG. Figure 2 shows the relationship between input electric field strength and AGC gain attenuation when the delay point is -70 dBm and the received signal electric field strength is 50 dBm. The IFAGC gain attenuation amount becomes a constant value at the delay point (-70 dBm), and the AGC loop acts by applying the RF AGC gain attenuation to the high electric field strength side by the delay point.

Here, for example, as shown in FIG. 3 (a), when the delay point is set to the direction of the weaker electric field, the IFAGC gain increases (that is, the IFAGC gain attenuation decreases) and the RFAGC gain decreases (that is, the RFAGC gain decreases). , R FAGC gain attenuation increases). Conversely, as shown in Fig. 3 (b), when the delay point is set in the direction of the stronger electric field, the gain distribution becomes smaller, and the gain becomes larger. The range in which this delay point can be set is determined when building a receiver system. The upper limit in the strong electric field direction is determined by the IFAGC gain attenuation. When selecting the target channel, the delay point is set to the upper limit in the direction of the strong electric field, and the channel is selected. This delay point is set so that the gain of the RFAGC amplifier in the preceding stage is larger than the gain of the IFAGC amplifier in the subsequent stage, and is a receiver characteristic that is advantageous for noise (C / N) interference. Do.

The microcomputer 10 can detect the received electric field strength (RFAGC gain attenuation and IFAGC gain attenuation) by reading the level signal detected by the level detector 7. Fig. 4 is a diagram showing the relationship between the input electric field strength and the amount of AGC gain attenuation and the adjacent interference characteristics of the tuner. As shown in Fig. 4, the received electric field strength When the deviation from the peak of the improvement curve (A in Fig. 4) of the characteristic curve (B in Fig. 4), the adjacent disturbance is displaced by moving the delay point in the direction of the weak electric field so that the adjacent disturbance characteristic force of tuner 1 is shifted. It can be adjusted to a region where the interference characteristics are improved. In other words, the received electric field strength was moved from B in Fig. 4 to C in Fig. 4 by shifting the adjacent disturbance characteristic force, and the improved peak point of the adjacent disturbance characteristic curve after the movement (D in Fig. 4). ). As described above, the present invention can adaptively adjust the received electric field strength to the region where the adjacent interference characteristics are improved, and as a result, can stably receive digital terrestrial broadcasting.

(Embodiment 2)

Next, Embodiment 2 will be described with reference to FIG.

FIG. 5 is a block diagram of a digital signal receiver in which a modulation state detector 8 for detecting a modulation scheme for each transmission layer is provided in the block diagram of FIG. 1 and an output of the modulation state detector 8 is input to the microcomputer 10. It is a block diagram. In a digital terrestrial broadcast channel, a plurality of transmission layers are modulated by different modulation schemes. The layers are separated by the host system 11, and a certain layer is selected and reproduced. If the modulation method is different, the required CZN (carrier Z noise ratio) will be different, so the required CZN level will increase as the modulation scheme becomes more multi-valued in the order of QPSK, 16 QAM, and 64 QAM. If the delay point is set in the direction of the stronger electric field, the receiver will be in an advantageous condition for CZN noise characteristics. It is necessary for the receiver to obtain reception characteristics that satisfy the required CZN according to the modulation method. Therefore, the delay point set value for obtaining the required CZN changes according to the modulation method. Fig. 6 shows a specific example. Fig. 6 shows an example of the delay point set value according to the modulation method in a diagram showing the relationship between the input electric field strength and the AGC gain attenuation. As shown in Fig. 6, the delay point set value for obtaining the required C / N in the order of the QPSK method, 16 QAM method, and 64 QAM method is the set value toward the strong electric field direction. In this way, by adopting a configuration in which the delay point setting is switched so that the required CZN can be obtained according to the modulation method, it is possible to enhance the characteristic with respect to the adjacent interference characteristic. (Embodiment 3)

Next, the third embodiment will be described with reference to FIGS.

Applications for receiving digital terrestrial broadcasting while moving are expected to further expand in the future. When receiving while moving, peculiar fading interference occurs. The amount of this fading interference is generally represented by the Doppler frequency. The higher the Doppler frequency, the greater the degree of interference.

Here, assuming that the moving speed is Vs (km /), the receiving channel frequency is Fch (MHz), and the Doppler frequency is Fdopp (Hz), Equation 1 holds.

(Fch χ 10 ⁶ ) x (Vs 10 ³ )

Fdopp = (Equation 1)

299.792 x 106 x 3600

Here, the denominator of Equation 1 is the speed of light per hour (mZh).

Equation 1 shows that the Doppler frequency Fd0pp increases as the receiving channel frequency Fch increases and the moving speed Vs increases. In other words, it can be seen that the influence of fusing interference increases. Figure 7 shows this relationship. Equivalent materials are also published in the Radio Industry Association's document “Standard No. ARIB STD-B29 (standard name: terrestrial digital audio transmission system)”. The disturbing wave due to fading impairs the desired wave with the phase and amplitude components, which is equivalent to disturbing as noise. Therefore, setting the delay point in the direction of the strong electric field as a receiver characteristic provides an advantageous state against fading interference. When assuming mobile reception, the Doppler frequency Fd opp generated when the moving speed Vs is assumed to be, for example, 100 kmZhr. This indicates that the set value of the delay point for satisfying the required Doppler frequency Fd0pp changes according to the reception channel frequency Fch.

Here, Fig. 8 shows an example of the delay point setting value according to the reception channel frequency. You. As shown in FIG. 8, the setting value of the delay point for obtaining the required Doppler frequency F dop as the frequency changes from the low frequency to the high frequency becomes the setting value in the direction of the strong electric field. By setting the delay point according to the reception frequency in this way, it is possible to increase the characteristics of adjacent frequencies when receiving a channel at each frequency. In this embodiment, the receiver front end such as a tuner and a demodulation unit has been described as an example. However, the present invention is not limited to this, and includes a set top box including a data reproduction unit and a display unit, a television system, It can be applied to mobile reception systems and in-vehicle systems.

-Industrial applicability

As described above, according to the present invention, it is possible to move the adjacent interference characteristic curve of a received signal to an optimal region in view of the received field strength value, and as a result, it is possible to receive a digital broadcast signal stably. A digital signal receiver can be provided.

Claims

The scope of the claims

1. a digital signal receiver,

A terminal for inputting a received signal, and an RFAGC amplifier for amplifying the received signal input from the terminal, selecting a received signal of a target channel from the received signal amplified by the RFAGC amplifier and converting the signal to an intermediate frequency signal A tuner to convert,

A filter for selectively passing the intermediate frequency signal;

An I FAGC amplifier for amplifying the signal passed through the filter;

A mixer for converting the signal amplified by the IFAGC amplifier into a signal having a frequency lower than the frequency of the signal;

A local oscillator that generates a local oscillation frequency signal to be input to the mixer; a demodulator that digitally demodulates an output signal output from the mixer and outputs the signal to a host system;

A level detector for detecting the level of the output signal;

A gain controller that receives a signal from the level detector and independently controls gains of the R FAGC amplifier and the I FAGC amplifier, and receives a signal from the level detector, and the host A microcomputer for outputting channel selection data of a target channel to the tuner in accordance with a channel selection command signal output from the system and a reproduction transmission layer signal;

With receiver.

2. In the gain control via the gain controller,

At the operation start point for starting the gain control of the RFAGC amplifier, the I FAG

Control the gain of the C amplifier to be constant, and

Arbitrarily set the operation start point to start the gain control of the RFAGC amplifier The digital signal receiver according to claim 1, wherein:

3. The microcomputer according to claim 1, wherein, when a target channel is selected in the gain control via the gain controller, the operation start point for starting the gain control of the RFAGC amplifier is a constant value. Digital signal receiver.

4. The digital signal receiver according to claim 1, wherein the microcomputer performs control according to a level signal detected by the level detector in gain control via the gain controller.

5. With respect to an output signal output from the mixer and passing through the demodulator, a modulation state detector for detecting a modulation scheme for each transmission layer is further provided.

The digital signal receiver according to claim 1, wherein a signal from the modulation state detector is input to the microcomputer.

6. The digital signal receiver according to claim 5, wherein the microcomputer sets an operation start point of gain control of the RFAGC amplifier in accordance with an output signal from the modulation state detector.

7. The digital signal receiver according to claim 5, wherein the microcomputer sets an operation start point of gain control of the RFAGC amplifier according to a frequency of a target channel.