JPH0823490A - Receiving device - Google Patents

Abstract

PURPOSE:To improve reception sensitivity and to realize a stable reception operation even in a weak electric field by providing a means for adding a signal obtained by delaying an amplified reception signal with a signal which is not delayed and outputting them in the poststage of a tuner. CONSTITUTION:A television radio wave received in an antenna 11 is inputted to the tuner 12, and a designated channel is selected in accordance with a tuning signal from a tuning control circuit 13. Then, the wave is converted into an intermediate frequency and it is inputted to an adaptive filter circuit 14. The circuit 14 inputs a video intermediate frequency signal to a gain variable unit through the adder and the gain variable unit amplifies the intermediate frequency signal while a gain is varied in accordance with an IFAGC signal transmitted from an intermediate frequency circuit 16, the delay element of the signal is delayed, it is added with an input intermediate frequency signal in the adder, and the signals are outputted to an addition filter 15. The output signal causes a speaker 20 to emit sound through the IF circuit 16 and an amplifier circuit 19. On the other hand, the output signal of the circuit 16 is inputted to a segment drive circuit 24 through a chroma circuit 17 and an A/D converter 23 and it drives a color LCD panel 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving device which is applied to, for example, a portable liquid crystal television set or the like and improves receiving sensitivity.

[0002]

2. Description of the Related Art In a liquid crystal television set or the like which places importance on portability and is supposed to be used in an outdoor moving state, there have been few attempts to improve the receiving sensitivity, and the antenna characteristic is improved. It was limited to using GaAs elements on the tuner front. For example, it is difficult to reduce the voltage by a method using a GaAs element, and the drain current is reduced by AG due to the change in the electric field, so that S
A problem such as a significant deterioration in the / N ratio occurred, and it did not reach a sufficient level. As described above, the conventional television receiving device has a problem that the receiving performance is insufficient because the fundamental improvement is not made particularly in the reception in the weak electric field.

[0003]

As described above, there is no liquid crystal television set having a circuit for greatly improving the receiving sensitivity in a weak electric field, and it depends on the performance of an antenna or the like such as a diversity system. Met.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a television receiving device capable of improving receiving sensitivity and realizing stable receiving operation even in a weak electric field. It is in.

[0005]

That is, according to the present invention, in the latter stage of the tuner, an amplifying means for amplifying a signal selected by reception with a gain according to a receiving level, and a delay for delaying the received signal amplified by this amplifying means. Means and addition means for adding the received signal delayed by the delay means and the undelayed received signal and outputting to the next stage.

[0006]

With the above-mentioned structure, the receiving signal can be narrowed by simply connecting a simple circuit to the conventional receiving circuit, the receiving sensitivity can be sufficiently improved, and stable receiving operation can be realized even in a weak electric field. Can be made.

[0007]

【Example】

[First Embodiment] A first embodiment in which the present invention is applied to a liquid crystal television device will be described below with reference to the drawings.

FIG. 1 shows the entire circuit configuration, and the television radio wave received by the antenna 11 is supplied to the tuner 12. The tuner 12 selects a designated channel (frequency) according to the tuning signal from the tuning control circuit 13 and converts it into an intermediate frequency signal. The intermediate frequency signal output from the tuner 12 is sent to the adaptive filter circuit 14.

The structure of the adaptive filter circuit 14, which will be described later in detail, narrows the band of the obtained intermediate frequency signal to improve the receiving sensitivity, and then the SAW (surface acoustic wave) filter.
After the band characteristic and the delay time characteristic are adjusted via 15, the signal is sent to an intermediate frequency circuit (shown as “IF circuit” in the figure) 16.

The intermediate frequency circuit 16 includes an intermediate frequency amplifier circuit, an AGC circuit, a video detection circuit, a video amplifier circuit, and an AFT.
It is composed of a detection circuit, an audio detection circuit, an audio FM detection circuit, etc., and an intermediate frequency signal sent through the SAW filter 15 is amplified by an intermediate frequency amplification circuit under the control of the AGC circuit, and then, The IFAGC signal whose video is detected by the video detection circuit to form a composite video signal and which is sent to the chroma circuit 17 and the sync separation circuit 18 and whose voltage drops as the reception level of the intermediate frequency signal obtained by the AGC circuit rises is described above. It is sent to the adaptive filter circuit 14.

The intermediate frequency circuit 16 sends to the tuning control circuit 13 an AFT signal whose voltage changes in an S-shape according to the tuning state obtained by the AFT detection circuit, and also outputs from the intermediate frequency amplifier circuit. The amplified intermediate frequency signal is subjected to voice detection to obtain a voice intermediate frequency signal, which is FM demodulated and sent to the voice amplifier circuit 19 as a voice signal in the audible frequency band. The voice amplifier circuit 19 voice-amplifies the voice signal from the intermediate frequency circuit 16 with a specific amplification factor, and the speaker 20 drives the speaker 20 by the obtained signal to emit a sound.

The sync separation circuit 18 separates the horizontal and vertical sync signals contained in the composite video signal into a composite sync signal C.
-SYNC is output to the tuning control circuit 13, and the horizontal synchronization signal H-SYNC and the vertical synchronization signal V-SYNC are output to the timing control circuit 21, respectively.

The tuning control circuit 13 includes a key input section.
Data for tuning setting from 22, VHF and UHF
Key input such as selection of received broadcast or tuning up / down instruction is given. The tuning control circuit 13 creates a tuning signal having a voltage value corresponding to a designated channel based on the operation of the tuning up / down key in the key input unit 22 and outputs the tuning signal to the tuner 12.

The timing control circuit 21 outputs a timing pulse φ based on the horizontal sync signal H-SYNC and the vertical sync signal V-SYNC sent from the sync separation circuit 18.
s is created and output to the A / D conversion circuit 23.

The chroma circuit 17 performs chroma processing on the composite video signal supplied from the intermediate frequency circuit 16 to produce R, G,
A chroma signal composed of the three primary colors B is obtained, and the obtained chroma signal is output to the A / D conversion circuit 23.

The A / D conversion circuit 23 converts the chroma signal output from the chroma circuit 17 into the sampling pulse φs.
Sampling is performed in synchronism with the above, and converted into digital video data of 3 to 4 bits per pixel, and the segment drive circuit 24
Output to.

Further, the timing control circuit 21 creates a timing signal for display control based on the horizontal sync signal H-SYNC and the vertical sync signal V-SYNC provided from the sync separation circuit 18, and the segment drive circuit 24 and The operation of the common drive circuit 25 is controlled.

The common drive circuit 25 generates a scanning signal in accordance with the timing signal from the timing control circuit 21 and sequentially scans and drives the common electrodes of the color LCD panel 26. On the other hand, the segment drive circuit 24 sequentially reads the 3- to 4-bit video data supplied from the A / D conversion circuit 23 according to the timing signal from the timing control circuit 21, and after reading the video data for one line. Create a gradation signal according to the image data, and color LCD panel
Display driving of 26 segment electrodes.

Next, the structure of the adaptive filter circuit 14 will be described with reference to FIG. In the figure, the video intermediate frequency signal sent from the filter circuit 14 is output to the SAW filter 15 via the adder 31 and also to the gain varying device 32.

The gain variable device 32 is composed of the intermediate frequency circuit 16 described above.
The intermediate frequency signal is amplified while varying the gain according to the IFAGC signal transmitted from the amplifier. The amplified intermediate frequency signal is transmitted to the delay element 33.

The delay element 33 delays the intermediate frequency signal sent with a preset delay characteristic (time) and supplies it to the adder 31. In the adder 31, the delayed intermediate frequency signal is delayed. The signal and the undelayed intermediate frequency signal from tuner 12 are added and the sum is output as described above.

In this way, by adding the delayed intermediate frequency signal and the undelayed intermediate frequency signal,
The S / N ratio of the intermediate frequency signal, which is the sum thereof, can be improved and the band can be narrowed.

The operation of the adaptive filter circuit 14 having the above structure will be described below. As described above, the IFAGC signal input from the intermediate frequency circuit 16 to the gain changer 32 in the adaptive filter circuit 14 is in a strong electric field of the present device, the intermediate frequency signal reception level is high, and the reception state is good. On the contrary, the reception level of the intermediate frequency signal is low under a weak electric field, and is high if the reception state is bad.

The gain variator 32 controls the gain increase / decrease in proportion to the level of the IFAGC signal, and amplifies the intermediate frequency signal sent from the adder 31. Is increased or decreased to control the S / N ratio of the intermediate frequency signal and the degree of band narrowing.

FIG. 3 shows changes in the frequency characteristics of the intermediate frequency signal according to the magnitude of the electric field strength. In the figure, fs is the frequency of the audio intermediate frequency signal (54.25 MHz), and fc is the frequency of the color subcarrier. (55.17 MHz), fv represents the frequency (58.75 MHz) of the video intermediate frequency signal.

FIG. 3 (1) shows that this device is under a strong electric field, and therefore the level of the IFAGC signal is low, and the gain variator 32 is
Shows the frequency characteristic I of the intermediate frequency signal output to the SAW filter 15 when the signal does not substantially amplify the intermediate frequency signal. In this case, since it is not necessary to improve the reception sensitivity, the obtained intermediate frequency signal has almost the original frequency characteristic, and the reception processing is executed as it is by the circuit below the SAW filter 15. .

3 (2) and 3 (3), the SAW in the case where the present apparatus is under a moderate electric field, therefore the level of the IFAGC signal is high and the gain variator 32 sufficiently amplifies the intermediate frequency signal. 3 shows frequency characteristics II and III of the intermediate frequency signal output to the filter 15. In these cases, the obtained intermediate frequency signal has a considerably narrow band as compared with the original frequency characteristic I, and the characteristic position of the narrow band can be changed by arbitrarily setting the delay characteristic (time) of the delay element 33. can do.

By thus improving the S / N ratio of the intermediate frequency signal and narrowing the band, high-sensitivity reception becomes possible. Since the bandwidth also decreases in accordance with the electric field, weak electric fields can be obtained. In that case, stable reception can be realized although the resolution of the image is deteriorated.

Next, FIG. 4 illustrates another configuration of the adaptive filter circuit 14 shown in FIG. Here, in the adaptive filter circuit 14 ', in addition to the delay element 33, a delay element 34 having a delay time different from that of the delay element 33 is connected in parallel.

By properly setting the delay times of the delay element 33 and the delay element 34, as shown by the characteristic IV in FIG. 5, the signals at the frequency point positions of fs, fc and fv in the intermediate frequency signal are received. As a result, the voice sensitivity is improved, and at the same time, a rough image and a certain amount of image information such as character information can be obtained even in a weak electric field.

In the first embodiment, the IFAGC signal is sent from the intermediate frequency circuit 16 to the adaptive filter circuit 14 as a signal indicating the reception level. However, the present invention is not limited to this. Other signals may be used as long as they are changing signals.

Although the first embodiment has been described as being applied to a liquid crystal television device, a receiving device such as an FM radio or an AM radio, a wireless communication device including a transceiver, or the like which is used in a mobile state while being carried. Of course, it can be easily applied to the receiving circuit in the transmitting / receiving device.

[Second Embodiment] Next, a second embodiment in which the present invention is applied to a liquid crystal television device will be described with reference to the drawings.

FIG. 6 shows the entire circuit configuration, which is basically the same as that shown in FIG. 1, so that the same portions are denoted by the same reference numerals and the description thereof will be omitted. Then, the intermediate frequency signal output from the tuner 12 is sent to the adaptive filter circuit 41.

The structure of the adaptive filter circuit 41 will be described later in detail, but a band limitation is appropriately applied to the obtained intermediate frequency signal to improve the receiving sensitivity and then the SAW filter.
The IFAGC which outputs to the IF circuit 15 and whose voltage drops as the reception level of the IF signal from the IF circuit 16 rises.
A signal is input and a horizontal sync signal H-SYNC is input from the sync separation circuit 18.

Next, the structure of the adaptive filter circuit 41 will be described with reference to FIG. In the figure, the adaptive filter circuit 41
Are two band limiting filters 41a and 41b and a switch circuit 41.
and c.

The video intermediate frequency signal sent from the tuner 12 is supplied to both the band limiting filters 41a and 41b. These band limiting filters 41a and 41b have different band limiting characteristics as shown in the figure. For example, the band limiting filter 41a is the frequency of the video intermediate frequency signal fv (5
8.75 MHz) to a band of about 2 MHz on the particularly low side, and the band is limited in the central portion, around 57.75 MHz, and the band limiting filter 41b similarly uses the frequency of the video intermediate frequency signal fv (58.75 MHz). ), About 2 MHz lower than 56.75 MHz. The outputs of these band limiting filters 41a and 41b are both supplied to the switch circuit 41c.

The switch circuit 41c includes the intermediate frequency circuit 16
When the level of the IFAGC signal input from the device is higher than a predetermined threshold value and the device is used under a weak electric field, it is synchronized with the horizontal sync signal H-SYNC from the sync separation circuit 18 for 1H (horizontal scanning period). (About 1/15750 [sec])), the band-limited intermediate frequency signals output from the band-limited filters 41a and 41b are alternately switched, and the SAW filter at the next stage is switched.
This is output to 15. The level of the IFAGC signal input from the intermediate frequency circuit 16 is lower than a predetermined threshold,
Although not shown in the figure, the switch circuit 41c does not show the intermediate frequency signal from the tuner 12 as it is without using the band limiting filters 41a and 41b when the device is used under a strong electric field or when the tuning operation is performed.
Supply to 15.

In the above configuration, it is assumed that the SAW filter 15 has a frequency characteristic with respect to an intermediate frequency signal as shown in FIG. Also in this figure, fs indicates the frequency of the audio intermediate frequency signal (54.25 MHz), fc indicates the frequency of the color subcarrier (55.17 MHz), and fv indicates the frequency of the video intermediate frequency signal (58.75 MHz).

However, in the adaptive filter circuit 41, which is the preceding stage of the SAW filter 15, the switch circuit 41c is operated by the band limiting filters 41a and 41b when used in a weak electric field according to the IFAGC signal from the intermediate frequency circuit 16 as described above. The band-limited intermediate frequency signal output by the switch is alternately switched every 1H by the horizontal sync signal H-SYNC from the sync separation circuit 18 and output to the SAW filter 15 of the next stage.

Therefore, these adaptive filter circuits 41, S
The frequency characteristic of the intermediate frequency signal that passes through the AW filter 15 and is supplied to the intermediate frequency circuit 16 is as shown in FIG. In the figure, a characteristic V indicated by a solid line between points A and B is selectively switched between the output of the band limiting filter 41a by the switch circuit 41c and a characteristic VI indicated by a broken line is selectively switched between the output of the band limiting filter 41b and output to the SAW filter 15. In this way, the signals in which the low-frequency component and the high-frequency component of the luminance signal region in the intermediate frequency signal are band-limited are alternately switched and output, so that the receiving sensitivity is improved while the gain is obtained. It is possible to minimize the deterioration of the resolution of the captured image.

The second embodiment shows an example in which the present invention is applied to a liquid crystal television device and a color LCD panel 26 is used as a display element, but the color LCD panel 26 is generally accumulated by driving an effective value. Since it is a display element that responds, even if image data is obtained from signals having different frequency characteristics of the intermediate frequency for each 1H and displayed, the image does not cause flicker, etc. large.

In the second embodiment, the IFAGC signal is sent from the intermediate frequency circuit 16 to the adaptive filter circuit 14 as a signal indicating the reception level. However, the present invention is not limited to this. Other signals may be used as long as they are changing signals.

It is also conceivable to use the vertical synchronizing signal V-SYNC instead of the horizontal synchronizing signal H-SYNC as the switching control signal given from the synchronizing separation circuit 18 to the switch circuit 41c.

[0045]

As described above, according to the present invention, the receiving signal can be narrowed in band by simply connecting a simple circuit to the conventional receiving circuit to sufficiently improve the receiving sensitivity and to stabilize even in a weak electric field. It is possible to provide a receiving device that can realize a receiving operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of the adaptive filter circuit of FIG.

FIG. 3 is a diagram for explaining the operation according to the embodiment.

FIG. 4 is a block diagram illustrating another configuration of the adaptive filter circuit of FIG.

FIG. 5 is a diagram for explaining an operation according to the embodiment with the configuration of FIG.

FIG. 6 is a block diagram showing a circuit configuration according to a second embodiment of the present invention.

7 is a block diagram showing a detailed configuration of the adaptive filter circuit of FIG.

FIG. 8 is a diagram for explaining the operation according to the embodiment.

FIG. 9 is a diagram for explaining the operation according to the embodiment.

[Explanation of symbols]

11 ... Antenna, 12 ... Tuner, 13 ... Tuning control circuit, 14, 14 ', 41 ... Adaptive filter circuit, 15 ... SAW filter, 16 ... Intermediate frequency (IF) circuit, 17 ... Chroma circuit, 18
… Synchronous separation circuit, 19… Voice amplification circuit, 20… Speaker, 21
... Timing control circuit, 22 ... Key input section, 23 ... A / D conversion circuit, 24 ... Segment drive circuit, 25 ... Common drive circuit, 26 ... Color LCD panel, 31 ... Adder, 32 ... Gain changer, 33 ... Delay element, 34 ... Delay element, 41a, 41b ... Band limiting filter, 41c ... Switch circuit.

Claims (3)

[Claims] 1. A variable amplifying means for amplifying a received signal with a gain according to its reception level, a delay means for delaying the received signal amplified by this variable amplifying means, and a delayed signal delayed by the delay means. A reception device comprising: an addition unit that adds a reception signal that is not added and outputs the addition signal to the next stage. 2. The delay means comprises a plurality of delay elements having different delay characteristics, and the received signals delayed by the plurality of delay elements are collectively supplied to the adding means. Receiver. 3. A plurality of filter means for applying band limitation of different characteristics to the received signal, a detection means for detecting a decrease in the received level of the received signal, and a decrease in the received level by the detecting means. At this time, the receiving device is provided with a switching means for selectively switching the band-limited reception signals output from the plurality of filter means at a specific cycle and outputting to the next stage.