CN201127070Y

CN201127070Y - Digital television receiver

Info

Publication number: CN201127070Y
Application number: CNU2007201711010U
Authority: CN
Inventors: 潘建兵; 王峰
Original assignee: Shenzhen Coship Electronics Co Ltd
Current assignee: Shenzhen Coship Electronics Co Ltd
Priority date: 2007-11-26
Filing date: 2007-11-26
Publication date: 2008-10-01
Anticipated expiration: 2017-11-26

Abstract

The utility model discloses a digital television receiver, comprising a tuner (high frequency head) and a controller, a radio frequency amplifier which comprises a pi shaped attenuator and a controllable attenuating circuit of a PIN diode, and forms a feedback control circuit with the tuner and the controller, with input terminal thereof connected to the output terminal of the radio frequency amplifier. When it is detected that AGC value of the tuner is smaller than or equal to the first threshold, the controllable attenuating circuit is opened by control. When it is detected that AGC value of the tuner is bigger than or equal to the second threshold, the controllable attenuating circuit is shut by control, and the input signal level is converted into a level capable to be received by the tuner. The utility model expands level range of received signal of the tuner, enhances receiving sensitivity of the digital television receiver, increases dynamic applicability of the signal level, has advantages of simple circuit construction, low implementing cost.

Description

A kind of digital television receiver

Technical field

The utility model relates to the Digital Television reception technique, especially relates to the digital television receiver of a kind of dynamically adapting network level, expansion tuner (tuner) signal incoming level scope.

Background technology

Multifunctional application and the focus that is digitized into to current cable television network, and become the important channel that cable television network enlarges service and increases income.For this reason, (HybirdFiber-Coaxial on basis HFC), has increased transmission broadband business and digital television business to the hybrid network that combines at optical fiber and coaxial cable.

At present, hfc plant front end downstream signal is made up of anolog TV signals, digital television signal and downlink data signal, and transmission the time need take into account various downstream signals mutually; Simultaneously, add the influence of factors such as load in the real network, transmission range, the signal level in the hfc plant is also not really stable: in the near place of distance trunk amplifier, signal level can be very high, and in the place away from trunk amplifier, signal level can be very low.If consider the long-distance transmissions of signal again, then signal transfer quality can further descend.

As shown in Figure 1, existing digital television receiver 130 is connected with hfc plant 110 by coaxial cable 120.The digital program information that radio and television local side equipment sends, the modulation back transfers to digital television receiver by hfc plant, is converted to the analog signal that television set 140 can receive and play by digital television receiver.Therefore, can the tuner in the digital television receiver (being called tuner again) adapt to complicated network environment, is to realize the stable prerequisite guarantee of television set rating.

For making the dynamic applicable network level of digital television receiver, improve receiving sensitivity, existing solution normally increases amplifier or attenuator at the receiving terminal of digital television receiver and guarantees that signal level in the network is within the scope of the tuner incoming level of digital television receiver.There is following defective in this solution:

1, owing to pair amplifier or attenuator are not controlled in real time, when the burst of network signal level strengthens or weakens, the receiving terminal of digital television receiver can not dynamically be adjusted voluntarily, cause digital television receiver to the requirement of network level than higher, applicability is relatively poor;

2, because the level range of input signal still is limited by the scope of the tuner incoming level of digital television receiver, so this scheme can not expand the scope of the tuner received signal level of digital television receiver.

The utility model content

Technical problem to be solved of the present utility model is, proposes a kind of digital television receiver of spread signal incoming level, and it is the variation of applied input signal level dynamically, strengthens the applicability to signal level.

For addressing the above problem, the utility model discloses a kind of digital television receiver, comprises controller and the tuner (tuner) that is connected with described controller; Radio frequency amplifier; Controlled attenuator circuit, its input connects the output of described radio frequency amplifier, and forms feedback control loop with described tuner and described controller; When the automatic gain control value that detects described tuner when described controller was less than or equal to first threshold, described controlled attenuator circuit was opened in control; The automatic gain control value that detects described tuner when described controller is during more than or equal to second threshold value, and described controlled attenuator circuit is closed in control, and incoming signal level is converted to the level that described tuner can receive.

More excellent, described controlled attenuator circuit comprises ∏ type attenuator and the PIN diode that is connected in parallel, described controller be by control described PIN diode by or conducting control the unlatching of described controlled attenuator circuit or close.

More excellent, described controlled attenuator circuit is integrated controllable attenuator.

More excellent, described first threshold is the automatic gain control minimum gain value of described tuner.

More excellent, the automatic gain control maxgain value that described second threshold value is described tuner.

Compared with prior art, the utlity model has following beneficial effect:

The utility model is the controlled attenuator circuit that is combined into by ∏ type attenuator and PIN diode parallel connection, form feedback control loop with controller and tuner, detect automatic gain control (AGC) value of tuner by controller, on this basis, send control signal control PIN diode by or conducting realize controlling the unlatching of described controlled attenuator circuit or closing, within this level range that level conversion to tuner of input signal can be received.Therefore, the utility model has expanded the level range of tuner received signal, allows signal level to fluctuate in a big way at one, has not only improved the receiving sensitivity of digital television receiver, has also strengthened the dynamic applicability to signal level; It is simple that the utility model also has a circuit structure, realizes lower-cost advantage.

Description of drawings

Fig. 1 is the schematic diagram that existing digital television receiver is connected with hfc plant by coaxial cable.

Fig. 2 is the structural representation of a preferred embodiment of the utility model.

Embodiment

Core concept of the present utility model is, consider that (tuner) tuner in the digital television receiver has certain limitation to the level range of the radiofrequency signal of input, so pass through radio frequency amplifier, controlled attenuator circuit and tuner combination, detect the automatic gain of tuner by controller and control the height that (AGC) value is judged the input radio frequency signal level, on this basis, sending control signal realizes controlling the unlatching of described controlled attenuator circuit or closing, within this level range that level conversion to tuner of input signal can be received, thereby reached the scope of expansion tuner received signal level, and improved the receiving sensitivity of digital television receiver, also strengthened dynamic applicability to signal level.

Please refer to shown in Figure 2ly, is the structural representation of a preferred embodiment of the utility model.Digital television receiver of the present utility model comprises: controller 210; The tuner that is connected with described controller 210 (is called tuner again, Tuner) 220; Radio frequency amplifier 230; Input connects the controlled attenuator circuit 240 of radio frequency amplifier 230 outputs, and this controlled attenuator circuit 240 forms feedback control loop with described tuner 220 and described controller 210.The radiofrequency signal of input is amplified through described radio frequency amplifier 230, enters described controlled attenuator circuit 240 again and carries out reaching the input of described tuner 220 again after the attenuation processing.

Wherein, described radio frequency amplifier 230 is selected the device that noise factor is low, gain flatness is good for use.Low-noise factor can guarantee the signal to noise ratio after radiofrequency signal is amplified, and gain flatness can guarantee the consistency of performance in the bandwidth well.

Described controlled attenuator circuit 240 comprises attenuator 241 and the PIN diode 242 that is connected in parallel, and by a general input/output port port of described controller 210 (General-Purpose I/O port, GPIO) the output control signal is controlled described controlled attenuator circuit 240.In the present embodiment, for the consideration of attenuator functional performance, the preferred ∏ type attenuator 241 that adopts can certainly adopt the attenuator of other types to substitute, such as T type attenuator in the described controlled attenuator circuit 240.And the attenuation multiple of described ∏ type attenuator 241 can be set according to the actual requirements.

Described PIN diode 242 is connected between described radio frequency amplifier 230 and the described tuner 220; Impedance is very little when the 242 energising conductings of described PIN diode, and radiofrequency signal reaches described tuner 220 by described PIN diode 242; When described PIN diode 242 by the time impedance very big, radiofrequency signal reaches described tuner 220 by described ∏ type attenuator 241.

Thread task automatic gain control (AGC) value of the described tuner 220 of monitoring is in real time arranged in described controller 210, can pass through I ²The C bus reads the AGC value of described tuner 220 in real time and judges: when the AGC value is less than or equal to first threshold A, the level of radiofrequency signal that promptly inputs to described tuner 220 is too high, then described controller 210 sends control command by a GPIO port, make described PIN diode 242 by, described controlled attenuator circuit 240 is opened in i.e. control, makes radiofrequency signal be undertaken reaching described tuner 220 again after the attenuation processing by described ∏ type attenuator 241; When AGC value during more than or equal to the second threshold value B, the level of radiofrequency signal that promptly inputs to described tuner 220 is low excessively, then described controller 210 sends control command by the GPIO port, make described PIN diode 242 conductings, described controlled attenuator circuit 240 is closed in i.e. control, make radiofrequency signal reach described tuner 220, realize the level of RF signals of input is converted to the level that described tuner 220 can receive with this by described PIN diode 242.

The value of the first threshold A and the second threshold value B is relevant with the span of the AGC value of described tuner 220: first threshold A trends towards the minimum gain value of AGC value as far as possible, such as, first threshold A value equals the AGC minimum gain value of described tuner 220; The second threshold value B trends towards the maxgain value of AGC value as far as possible, such as, the second threshold value B value equals the AGC maxgain value of described tuner 220.Like this, the level of radiofrequency signal can produce fluctuation in real network, the AGC value also can change repeatedly, when having avoided the value of the first threshold A and the second threshold value B to be close, near certain particular level, described controlled attenuator circuit 240 can open or cut out repeatedly, causes transport stream (TS) error rate height through tuner output, and the problem of mosaic appears in television image.

Certainly, described controlled attenuator circuit 240 also can adopt integrated controllable attenuator, but realizes that cost is higher relatively.

To sum up, the utility model is the controllable attenuation circuit that becomes with the PIN diode parallel combination by ∏ type attenuator, form feedback control loop with controller and tuner, detected automatic gain control (AGC) value of tuner by controller, on this basis, send control signal control PIN diode by or conducting realize controlling the unlatching of described controllable attenuation circuit or closing, within this level range that level conversion to tuner of input signal can be received. Therefore, the utility model has expanded the level range that tuner receives signal, allow signal level one in a big way in fluctuation, be particularly suitable for the collocation use with hfc plant; The utility model has not only improved the receiving sensitivity of digital television receiver, has also strengthened the dynamic applicability to signal level; And it is simple to have circuit structure, realizes lower-cost advantage.

Claims

1, a kind of digital television receiver comprises controller and the tuner that is connected with described controller, it is characterized in that, also comprises:

Radio frequency amplifier;

Controlled attenuator circuit, its input connects the output of described radio frequency amplifier, and forms feedback control loop with described tuner and described controller;

When the automatic gain control value that detects described tuner when described controller was less than or equal to first threshold, described controlled attenuator circuit was opened in control; The automatic gain control value that detects described tuner when described controller is during more than or equal to second threshold value, and described controlled attenuator circuit is closed in control, and incoming signal level is converted to the level that described tuner can receive.

2, digital television receiver according to claim 1, it is characterized in that, described controlled attenuator circuit comprises attenuator and the PIN diode that is connected in parallel, described controller be by control described PIN diode by or conducting control the unlatching of described controlled attenuator circuit or close.

3, digital television receiver according to claim 2 is characterized in that, described attenuator is a ∏ type attenuator.

4, digital television receiver according to claim 1 is characterized in that, described controlled attenuator circuit is integrated controllable attenuator.

According to any one described digital television receiver of claim 1 to 4, it is characterized in that 5, described first threshold is the automatic gain control minimum gain value of described tuner.

6, according to any one described digital television receiver of claim 1 to 4, it is characterized in that the automatic gain control maxgain value that described second threshold value is described tuner.

7, digital television receiver according to claim 5 is characterized in that, the automatic gain control maxgain value that described second threshold value is described tuner.