JPH07115568A - On-vehicle television receiver - Google Patents

Abstract

PURPOSE:To improve the picture quality of the on-vehicle television receiver. CONSTITUTION:The television receiver consists of a diversity control section 1 and a ghost canceller section 2. The ghost canceller section 2 is provided with a control block 14 extracts a signal for a non-signal portion (10H-13H) period in a vertical blanking period of a video signal and adds the signals synchronizingly, a CPU 17, a RAM 18 and a DSP 20 calculating a tap coefficient based on the signal of synchronization addition and a reference signal of a ROM 18, and a transversal filter 16 receiving a tap coefficient calculated by the CPU 17 and eliminating transmission distortion of the video signal inputted at that time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a vehicle-mounted television device.

[0002]

2. Description of the Related Art In recent years, television devices have become widespread in moving bodies such as automobiles, and television programs can now be viewed even in automobiles. However, in a running car,
Since the reception state changes rapidly, the image quality of the image displayed on the television device is more difficult to write than the home television device, and improvement of the image quality is desired.

Therefore, in recent years, a diversity apparatus, which has a plurality of antennas and an antenna selection circuit and selects the antenna with the best reception state, is often used for a vehicle-mounted television apparatus.

However, when a plurality of antennas for this diversity device are provided in an automobile or the like, it is practically difficult to combine an ideal unidirectional antenna because the design of the automobile is taken into consideration. Even if it does, a ghost will appear on the screen of the television device.

On the other hand, a ghost removing device for digitally processing a video signal to remove a ghost has already been used for a home television device. In the case of this ghost removing device, the ghost removing process currently requires about several seconds to several tens of seconds.

However, in a moving automobile, etc.,
Since the ghost state changes instantaneously, for example, on a field-by-field basis, it cannot be used as a vehicle-mounted device in a ghost removing device having a long ghost processing time.

[0007]

As described above, in the conventional vehicle-mounted television device, it is desired to use the ghost eliminating device which has the effect of eliminating the transmission distortion contained in the video signal, but it is usually used in the home. However, the ghost elimination process takes time in the case of the one used in the television set for use in a vehicle, and there is a problem that it cannot be used in a vehicle.

The present invention has been made in order to solve such a problem, and it is possible to perform ghost removal processing in real time and remove ghosts even while moving, and as a result, it is possible to display a high quality image on a vehicle-mounted television. It is intended to provide a John device.

[0009]

In order to achieve the above-mentioned object, the present invention comprises an extracting means for extracting a signal of a non-signal part in a vertical blanking period of a video signal from a predetermined television signal receiving part, Storage means for storing a reference signal having no transmission distortion as a reference for the signal of the non-signal portion, and a predetermined signal based on the signal of the non-signal portion extracted by the extracting means and the reference signal of the storage means Is performed to calculate a tap coefficient that cancels transmission distortion of the video signal, and the tap coefficient calculated by the tap coefficient calculating means is written, and the television signal is calculated based on the tap coefficient. And a filtering unit that removes transmission distortion of the video signal from the receiving unit.

In addition, in this on-vehicle television device, the predetermined television signal receiving section includes a television tuner for detecting a television signal sequentially received from a plurality of antennas.
Ghost amount detection means for detecting the ghost amount in the equivalent pulse section in the vertical blanking period of each video signal output from this television tuner, and each ghost amount sequentially detected by this ghost amount detection means are compared. The selection means for selecting the antenna that has received the television signal with the smallest number of the above, and the means for outputting the video signal from the antenna selected by this selection means.

Further, this on-vehicle television device is
It is provided with a means for synchronously adding signals of a plurality of sections of the signalless portion in the vertical blanking period within one field of the video signal extracted by the extracting means.

[0012]

According to the present invention, the ghost amount of the video signal obtained from the plurality of antennas is sequentially compared by the television signal receiving section, and the antenna having the smallest ghost is switched.
The signal of the non-signal portion in the vertical blanking period of the video signal from the antenna is extracted by the extracting means. Then, the reference signal having no transmission distortion of the storage means is read by the tap coefficient calculation means, and a tap coefficient that cancels the transmission distortion of the video signal is calculated from the reference signal and the signal of the non-signal part, and the filtering means is provided. Written.

As a result, when the video signal (video signal containing transmission distortion) from the television signal receiving section passes through the filtering means for each field, the transmission distortion is canceled and the ghost is removed.

As a result, it becomes possible to display an image of high image quality in which the rolling phenomenon is reduced on the in-vehicle television device.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a vehicle-mounted television device according to an embodiment of the present invention. This on-vehicle television device includes a diversity control unit 1 and a ghost canceller unit 2.

A plurality of diversity control units 1, for example,
Four antennas 3 to 6, an antenna selector 7 for switching these antennas 3 to 6, and these antennas 3 to
A TV tuner 8 for detecting the TV signal received in 6.
An electric field strength detection circuit 9 for detecting an electric field strength from the detected video signal, a ghost detection circuit 10 for detecting a ghost level from the detected video signal, and diversity control for comparing the data of the both and judging the antenna selection. It is composed of a microcomputer 11 and a timing pulse generation circuit 12. In carrying out the present invention,
An on-vehicle television device does not necessarily need to include the diversity control unit 1, but in recent years, almost all diversity control units 1 have been installed in a vehicle-mounted television device.
Is added, the same applies to this embodiment.

On the other hand, the ghost canceller section 2 has an A / D
Converter 13, control block 14, D / A converter 15
And a transversal filter 16 and a CPU 17, a ROM 18, a RAM 19 and a DSP 20 as a tap coefficient calculator.

The control block 14 outputs the video signal input from the diversity control section 1 to a video display section (not shown) through the transversal filter 16. The control block 14 controls the phase of the video signal and C
It interfaces with the microcomputer bus used by the PU 17, the ROM 18, the RAM 19, the DSP 20, and the like. As shown in FIG. 2, the transversal filter 16 is an FIR type filter including a multiplier (×), an adder (+), a delay (T), etc., and a tap coefficient calculation is performed on the multiplier (×). The tap coefficient Cn calculated by the unit is written.

In this on-vehicle television device, the diversity control unit 1 receives a television signal by each of the four antennas 3 to 6, converts the best television signal into a video signal and sends it to the ghost canceller unit 2. .

First, the operation of the diversity controller 1 will be described.

The television signal received by each of the four antennas 3 to 6 is detected by the television tuner 8 and becomes a video signal. This video signal is a field strength detection circuit 9,
It is input to the ghost detection circuit 10, the timing pulse generation circuit 12, and the like. Then, the timing pulse generation circuit 12 sends a strobe signal STB to the diversity control microcomputer 11, and at this timing, the diversity control microcomputer 11 fetches the respective data from the electric field strength detection circuit 9 and the ghost detection circuit 10, and based on these conditions. Select the antenna.

In this case, the electric field strength detection circuit 9 detects the pedestal level (detection level) of the detection output within 1 / 2H of each pulse section of 7H to 9H (equivalent pulse 3H section) during the vertical blanking period of the video signal. Based on the level), the electric field strength level data for each antenna is detected. The equivalent pulse (7H to 9H) section in the odd field corresponds to 270H to 272H in the even field.

On the other hand, the ghost detection circuit 10 also detects ghost level data within 1 / 2H of each pulse section.

Hereinafter, referring to FIG. 3, the ghost detection circuit 1
The ghost detection operation at 0 will be described.

The ghost detecting circuit 10 detects the ghost level within the period of the vertical synchronizing pulses Va and Vb (1 / 2H of each pulse of the above-mentioned equivalent pulse 3H section).

As shown in the figure, when a video signal containing ghost pulses Ga and Gb of about 6 dB each for positive and negative is inputted to the ghost detection circuit 10, the ghost detection circuit 10 firstly outputs the video signal Sa. Is differentiated at the rising and falling timings of each pulse to generate a differential wave Sb. This differential wave Sb is compared with the comparison voltage (broken line) and becomes the comparator output Sc according to this level. By superimposing the 1 / 2Hd pulse Sd that masks the vertical synchronizing pulses Va and Vb on the comparator output Sc, the ghost count signal Se having only the ghost component can be obtained. In addition, this ghost count signal Se
In this case, when one ghost pulse Ga, Gb is generated, two square waves are obtained. Therefore, by multiplying this by a digital counter (not shown), it becomes digitized ghost count data.

The diversity operation by the diversity control microcomputer 11 will be described below with reference to the flowchart of FIG.

The diversity control microcomputer 11 first reads the above-mentioned data one by one every 1 / 2H based on the strobe signal STB from the timing pulse generation circuit 12. At this time, when the diversity control microcomputer 11 receives the V head pulse from the timing pulse generation circuit 12 (step 501), the internal counter is reset to 0.
After clearing (step 502), an antenna switching signal is sent to the antenna selector 7 to switch to the next antenna (step 503). Subsequently, the diversity control microcomputer 11 receives the ghost reading clock from the timing pulse generating circuit 12 and reads the ghost count data (step 504). Then, the diversity control microcomputer 11 uses the timing pulse generation circuit 12
A detection level reading clock is received from the detection level data and the detection level data digitized by the A / D clock sent to the electric field strength detection circuit 9 is read (step 50).
Five ). The diversity control microcomputer 11 increments the internal counter (step 506) to perform this operation.
Repeat 4 times (step 507) for all antennas 3 ~
After reading the data of 6, the internal counter is reset to 0 (step 508). Subsequently, the diversity control microcomputer 11 arbitrarily selects two antenna numbers (step 509), compares the data with each other (step 510), increments the internal counter (step 511), and combines different antenna numbers. Data comparison three times (step 512). As a result, the diversity control microcomputer 11 determines the optimum antenna from the four antennas, sends an antenna switching signal to the antenna selector 7, and switches the antenna (step 513). afterwards,
The V head pulse is in a waiting state. As a result, the operation from reading each data of four antennas to switching to the optimum antenna is completed within 1 / 2H period.

When the diversity control microcomputer 11 switches the antenna, the data of the current antenna is compared with the data of the next selected antenna, and if there is no difference of a certain value or more, the current antenna is held. You can also

That is, the diversity control microcomputer 1
In Fig. 1, as shown in Fig. 6, the antenna with the least ghost is compared and selected from the four antennas within the signalless section 4H (7H to 10H) of the vertical blanking period, and the optimum antenna is 1 field. Hold for a period. Then, the television signal in the best reception state received by this antenna is input to the television tuner 8, and the video signal with the least transmission distortion is output to the ghost canceller unit 2.

The operation of the ghost canceller unit 2 will be described below with reference to FIGS.

First, the video signal is processed by the A / D 13, as shown in FIG. 7, in the signalless portion {10H to 13H (273H to 27H.
6H)} 4H period is the predetermined sampling frequency 4fsc (4
Double subcarriers) are sampled and digitized (hereinafter referred to as a digital video signal). This digital video signal is branched and output to the control block 14 and the transversal filter 16.

As shown in FIG. 8, the control block 14 firstly outputs the non-signal portion {10H to 13H (27
3H to 276H)} The signal of the first 1H (10H) period in the unused period is read (step 901) and the internal counter is set to 0 (step 902).

Then, the signal of the next signalless portion 1H (11H) is read (step 903) and the first signalless portion 1H (11H) is read.
H) is synchronously added (step 904) and the internal counter is incremented (step 905). Then, this synchronous addition is repeated for the remaining non-signal portion 2H (12H, 13H) (step 906).

By this synchronous addition for the 4H period, as shown in FIG. 9, the S / N of the signal of the no-signal portion is improved, and this signal is the tap coefficient calculation portion (CPU 17, RAM 18, RO).
M19 and DSP 20).

Next, the operation of the tap coefficient calculator will be described.

The tap coefficient calculation formula of the transversal filter 16 in the frequency domain is H (jω) = R (j
ω) / G (jω).

Therefore, first, in the tap coefficient calculation section, the input non-signal section is subjected to Fourier transform (FFT) (step 907). Then, the waveform of the non-signal portion becomes G (jω) (spectrum waveform) as shown in FIG.

Next, since the reference signal without transmission distortion (data of the non-signal portion for 1H period) is stored in the ROM 18 in advance, the CPU 117 reads this reference signal from the ROM 18 and performs Fourier transform (FFT). Then, as shown in FIG.
As shown in, R (jω) (reference spectrum waveform) is obtained.

Since the obtained two waveforms such as R (jω) and G (jω) are both complex numbers, the CPU 117
Perform complex division on each other (step 908), and as a result of this complex division, H (jω) is obtained as shown in FIG.

Further, the CPU 117 performs an inverse Fourier transform (IFT) on this H (jω) (step 909).
), As shown in FIG. 13, a waveform h (t) which is the basis of the tap coefficient Cn is obtained. Note that the tap coefficient Cn of the transversal filter 16 during the video period (22H and later)
Since noise appears on the screen when is rewritten, the tap coefficient Cn must be obtained at least during the vertical blanking period. Then, the tap coefficient waveform h (t) is converted into the original data such as a signalless portion and written in the RAM 19 (step 910), and the calculation process of the tap coefficient Cn is completed.

In this way, the tap coefficient calculation unit
The tap coefficient Cn that cancels the transmission distortion included in the no-signal portion is calculated at high speed.

Next, the control block 14 takes out the tap coefficient Cn from the RAM 19 and writes it in the multiplier (×) of the transversal filter 16. Then, when the non-signal portion including the transmission distortion from the TV tuner 8 is input to the transversal filter 16, the transmission distortion that is a ghost component is transmitted through the multiplier (×), the delay (T) and the adder (+). Only the video signal is removed, and the video signal in which the transmission distortion is reduced or erased according to the number of synchronously added fields is output to the D / A 15. In the D / A 15, the video signal whose transmission distortion is reduced or erased is D / A converted and output to a video display unit (not shown).

As described above, according to this embodiment, the antenna having the smallest ghost amount is switched from the plurality of antennas, and the non-signal portion in the vertical blanking period of the video signal obtained from the antennas is synchronously added. By performing ghost cancellation on the basis of the generated signal and the reference signal, it is possible to display a high-quality image in which the rolling phenomenon is reduced or erased on the in-vehicle television device. In addition,
When the ghost canceller unit 2 operates, ghosts are removed in real time from a running vehicle.
The image quality improving effect is remarkable in an automobile in which the image quality is extremely deteriorated.

Further, since the signals of a plurality of sections of the non-signal portion of the video signal are synchronously added, it is possible to improve the S / N of the signal of the non-signal portion including transmission distortion, and tap with this signal. As a result of calculating the coefficient, the ghost can be further reduced.

As a result, even a vehicle-mounted television device can perform ghost removal processing in real time.
A high-quality image can be displayed on the screen of the vehicle-mounted television device.

It should be noted that in the present embodiment, independent tap coefficient calculation units (CPU 17, ROM 18, RAM 19, DSP).
20) etc., the tap coefficient Cn of the transversal filter 16 is calculated at high speed. However, since such high-speed processing is costly, a low-speed processor that is cheap in terms of cost is practically used. It is also possible to do it. In this case, it takes about 1 field of calculation time, so 1V using field memory etc.
A delay circuit is needed. In addition, although the FIR type is used for the transversal filter in the present embodiment, the FIR type used in a normal home ghost canceller is used.
A + IIR type configuration may be used. In that case, first, the coefficient of the FIR filter is obtained in the same manner as described above, and the coefficient of the IIR filter is obtained using the signal passed through the FIR filter, which requires a slightly longer calculation time than the FIR type alone.

Further, in the present embodiment, the ghost detection is explained with points, but, for example, the traveling speed of the automobile becomes faster, and the higher the reception frequency is, the faster the electric field intensity changes. Therefore, at this time, S of the video signal is obtained by adding the waveforms of multiple fields using a waveform memory.
The tap coefficient may be calculated by improving / N.

[0050]

According to the on-vehicle television device of the present invention, the ghost amount is sequentially compared from the video signals obtained from the plurality of antennas, and the no-signal portion in the vertical blanking period of the video signal with the least ghost. Signal is extracted, and the ghost is removed in real time based on the signal of the no-signal portion and the reference signal, so that a high-quality image with reduced rolling phenomenon is displayed on the screen of the vehicle-mounted television device. It can be projected.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a vehicle-mounted television device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a transversal filter among blocks constituting the vehicle-mounted television device of FIG.

FIG. 3 is a diagram showing a ghost detection operation in the diversity control unit of FIG.

FIG. 4 is a timing chart of ghost level reading and detection level reading in the diversity control unit of FIG.

5 is a flowchart of a diversity operation in the diversity control unit of FIG.

FIG. 6 is a diagram showing an operation when a diversity control unit detects a ghost amount and selects an optimum antenna.

FIG. 7 is a diagram showing sampling of a non-signal portion in a vertical blanking period of a video signal.

FIG. 8 is a flowchart for synchronously adding sampled digital video signals to calculate and write a tap coefficient.

FIG. 9 is a diagram showing a waveform in a no-signal portion 1H period in which S / N is improved by synchronous addition.

10 is a diagram showing a waveform obtained by performing a Fourier transform on the waveform of the non-signal portion in FIG.

FIG. 11 is a diagram showing a waveform obtained by Fourier transforming a reference signal having no transmission distortion.

FIG. 12 is a diagram showing a waveform as a result of complex division of the waveforms of FIGS. 10 and 11.

13 is a diagram showing a waveform h (t) obtained by performing an inverse Fourier transform (IFT) on the waveform of FIG.

[Explanation of symbols]

1 ... Diversity control unit, 2 ... Ghost canceller,
3 to 6 ... Antenna, 7 ... Antenna selector, 8 ... TV tuner, 9 ... Electric field intensity detection circuit, 10 ... Ghost detection circuit, 11 ... Diversity control microcomputer, 12 ... Timing pulse generation circuit, 13 ... A / D converter, 14 ... Control block, 15 ... D / A converter, 16 ... Transversal filter, 17 ... CPU, 18 ... ROM, 19 ... R
AM, 20 ... DSP.

Claims (3)

[Claims] 1. Extraction means for extracting a signal of a no-signal part in a vertical blanking period of a video signal from a predetermined television signal receiving part, and no transmission distortion as a reference for the signal of the no-signal part. A storage unit that stores a reference signal, and a tap coefficient that cancels transmission distortion of a video signal by performing a predetermined calculation based on the signal of the non-signal portion extracted by the extraction unit and the reference signal of the storage unit. A tap coefficient calculating means for calculating the tap coefficient and a filtering means for writing the tap coefficient calculated by the tap coefficient calculating means and removing transmission distortion of the video signal from the television signal receiving section based on the tap coefficient. It is characterized by having. 2. The in-vehicle television device according to claim 1, wherein the predetermined television signal receiving section outputs a television tuner for detecting a television signal sequentially received from a plurality of antennas, and a television tuner. The ghost amount detecting means for detecting the ghost amount in the equivalent pulse section in each video signal vertical blanking period is compared with each ghost amount sequentially detected by the ghost amount detecting means to receive the television signal with the smallest ghost amount. An on-vehicle television set comprising: a selection unit that selects the selected antenna and a unit that outputs a video signal from the antenna selected by the selection unit. 3. The on-vehicle television set according to claim 1, wherein a means for synchronously adding signals in a plurality of sections of a signalless portion in a vertical blanking period within one field of the video signal extracted by the extracting means. A vehicle-mounted television device further comprising: