JP2588987B2 - Television diversity method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television diversity method, and more particularly to a television diversity method capable of reducing switching noise generated when switching antennas for television diversity.

<Prior Art> A television diversity apparatus is provided with a plurality of television antennas, sequentially switches the antennas during a beam vertical retrace period, checks the received electric field strength, and selects the antenna having the largest received electric field strength.

FIG. 3 is a block diagram of such a television diversity device, wherein 1a, 1b, 1c, 1d are first to fourth television antennas, 2 is an antenna switching circuit for switching antennas at high speed, 3 is a high-frequency amplifier circuit, 4 is a frequency conversion circuit for converting to an intermediate frequency signal, and 5 is a video intermediate frequency amplifying circuit, which generates a video / audio intermediate frequency signal. Reference numeral 6 denotes a video detection circuit which receives a video / audio intermediate frequency signal and outputs a video signal VDS, and 7 denotes an audio receiving circuit which receives a video / audio intermediate frequency signal and outputs an audio signal SDS. It has a 4.5MHz detection circuit that outputs a frequency signal, an audio intermediate frequency amplification circuit, an FM detection circuit, and a low frequency amplification circuit. Reference numeral 8 denotes a television diversity circuit, which sequentially switches the antennas from the first to fourth antennas at a frequency of 2 · Fh (Fh is a horizontal synchronization frequency) during the vertical flyback period of the beam, and receives the electric field strength of each antenna ( Check the video signal level) and select the antenna with the highest received electric field strength.

FIG. 4 is a waveform diagram for explaining the operation of the television diversity circuit 8, where VDS is a video signal, NSC is a horizontal synchronizing signal, VSC is a vertical synchronizing signal, CL is an internal clock signal having a frequency of 2 · Fh, and AST is 4 One antenna switching pulse, LCT, is a latch timing pulse for selecting the antenna having the maximum received electric field strength. The vertical retrace period of the video signal VDS includes six wide equivalent pulse trains EP1 and EP2 at a frequency of 2 · Fh, six incision pulse trains CP narrow at a frequency of 2 · Fh, and a horizontal synchronization signal HRP. I have.

The four antenna switching pulses AST are the second equivalent pulse train E
The VDS is synchronized with the first four pulses of P2, and the video signals of the four equivalent pulse portions received by the first to fourth antennas 1a to 1d by the antenna switching are input to the television diversity circuit 8 of the VDS. Latch timing of antenna of maximum level by antenna switching circuit 2
Television waves are received by the selected antenna by the LCT during the next one scanning period.

<Problems to be Solved by the Invention> In television diversity, antenna switching is performed during the vertical retrace period as described above. Therefore, there is no effect on the video signal. However, it adversely affects the audio signal and causes switching noise. This is because the audio signal is a continuous signal, which is also present during the vertical flyback period, and the audio signal loses (discontinuous portion) due to antenna switching, which becomes switching noise.

In view of the above, an object of the present invention is to provide a television diversity method that can reduce the occurrence of switching noise.

Another object of the present invention is to stop switching to the antenna input terminal when there is an antenna input terminal to which no antenna is connected or an antenna input terminal having a low reception electric field strength, thereby reducing the number of times of switching. It is an object of the present invention to provide a television diversity method capable of reducing the antenna switching noise.

<Means for Solving the Problems> According to the present invention, there is provided a means for monitoring whether or not an antenna input whose received electric field intensity is equal to or less than a predetermined value with respect to a maximum received electric field intensity is provided. Among the remaining antenna input terminals excluding the antenna input terminal for each line period, the antenna input terminal with the highest received electric field strength is obtained,
Means for receiving television radio waves by an antenna connected to the antenna input terminal, including the removed antenna input terminal for every N vertical retrace periods, to determine the antenna input terminal having the largest received electric field strength, It is configured by means for receiving a television wave by an antenna connected to the antenna input terminal.

<Operation> It is determined whether there is an antenna input terminal whose reception electric field strength is equal to or less than a predetermined value with respect to the maximum reception electric field strength, and if there is, the remaining antenna input excluding the antenna input terminal for each vertical retrace period. Among the terminals, the antenna input terminal having the highest received electric field strength is obtained, the television signal is received by the antenna connected to the antenna input terminal, and the antenna input terminal including the antenna input terminal excluded at every N vertical retrace periods is included. Then, an antenna input terminal having the maximum received electric field strength is obtained, and a television wave is received by an antenna connected to the antenna input terminal.

<Embodiment> Fig. 1 is a block diagram of a television diversity apparatus according to the present invention, wherein 10a to 10d are first to fourth television antennas, 11a to 11d are antenna input terminals to which antennas are connected, and 12 Is an antenna switching circuit for switching antennas at high speed, 13 is a high frequency amplifier circuit, 14 is a frequency conversion circuit for converting to an intermediate frequency signal, and 15 is a video intermediate frequency amplifier circuit, which generates a video / audio intermediate frequency signal. Reference numeral 16 denotes a video detection circuit which receives a video / audio intermediate frequency signal and outputs a video signal VDS, and 17 denotes an audio receiving circuit which receives a video / audio intermediate frequency signal and outputs an audio signal SDS. It has a 4.5MHz detection circuit that outputs a frequency signal, an audio intermediate frequency amplification circuit, an FM detection circuit, and a low frequency amplification circuit. 18 is a television diversity circuit,
When there is an antenna input terminal whose reception electric field strength is equal to or less than a predetermined value with respect to the maximum reception electric field strength, the antenna input terminal is skipped in the vertical retrace period, and the remaining antenna input terminals are sequentially selected to select the antenna input terminal. The reception electric field strength is checked, and the antenna having the highest reception electric field strength is caused to receive the television wave.

In the television diversity circuit 18, 18a is a video amplification circuit, 18b is a PLL circuit that generates a clock signal CL having a frequency of 2 · Fh from a video signal VDS, 18c is a control unit of a microcomputer configuration, and 18d to 18g are reception electric fields of each antenna. A sampling and holding circuit for sampling and holding the intensity, in other words, the reception level of the video signal, and the first, second,
The reception levels of the third and fourth antennas 10a to 10d are stored.

Hereinafter, the operation of the television diversity circuit 18 will be described with reference to the flowchart of FIG. In the following, i is the number of times of the diversity processing (the number of vertical blanking periods) performed in the vertical blanking period, and Fj (j = 1, 2, 3, 4)
Is a flag (initial value is "0") provided for each of the antenna input terminals 11a to 11d. When the received electric field intensity at a predetermined antenna input terminal becomes lower than a predetermined value compared to the maximum received electric field intensity, the input of the antenna becomes The flag of the terminal is set to "1" and becomes "0" when it is not less than a predetermined value compared to the maximum received electric field strength.

Now, the video signal VDS received by the current antenna is input to the video amplification circuit 18a of the diversity circuit 18, and after being video-amplified, the PLL circuit 18b and each sampling hold circuit
The clock CL having a frequency of 2 · Fh is output from the PLL circuit 18b.

In this state, when the vertical blanking period is reached, the control unit 18
c is set to i + 1 → i (the initial value of i is 0) (step 101), and the received electric field strength of each antenna is obtained by antenna switching (step 102). That is, the control unit 18c
The antenna input terminal whose flag Fj is “0” is identified, and the flag Fj is synchronized with the pulse of the equivalent pulse train EP2 (see FIG. 4).
Codes indicating “0” antenna input terminals are sequentially input to the antenna switching circuit 12.

Note that each code is output only once. If the received electric field strengths of the four antennas 10a to 10d are all large, four codes indicating the antenna input terminals 11a to 11d are sequentially output and one code is output. If the reception electric field strength of the antenna is small, codes indicating three antenna input terminals excluding the input terminals of the antenna are output. If the reception electric field strengths of the two antennas are small, two codes excluding these antenna input terminals are output. A code indicating the input terminal is output, and the code is output in the same manner.

When the code is input, the antenna switching circuit 12 selects a high-frequency signal from the antenna input terminal indicated by the code and outputs it to the next-stage high-frequency amplification circuit 15, and thereafter the high-frequency signal is subjected to high-frequency amplification, frequency conversion, and intermediate-frequency amplification. Is subjected to video detection to become a video signal.

Therefore, the high-frequency signal (in other words, the equivalent pulse portion of the video signal VDS) received by the antenna connected to the antenna input terminal indicated by the code is switched at the frequency of 2 · Fh and is sequentially switched to the video amplification circuit of the television diversity device 18. Entered at 18a.

The control unit 18c outputs the code of the antenna input terminal to the antenna switching circuit 12, and at the same time, inputs the sampling and holding signal SHi to the sampling and holding circuit corresponding to the antenna input terminal to sample and hold the level of the video signal VDS. As a result, when the first code indicates the antenna input terminal 11a to which the first antenna 10a is connected, the reception level of the video signal (equivalent pulse) received by the first antenna 10a is changed to the first sampling and holding circuit 18d. Is stored. Thereafter, similarly, the reception level of the video signal (equivalent pulse) received by the antenna connected to the antenna input terminal indicated by the code is stored in a predetermined sampling and holding circuit.

... Step 102 When the reception levels of the antennas connected to all the antenna input terminals for which the flag Fj is “0” are stored in each sampling and holding circuit, the control unit 18c uses the hold value to set the maximum reception level (maximum reception level). An antenna input terminal of the electric field strength Ml is obtained, a code indicating the antenna input terminal is output to the antenna switching circuit 12, and the antenna switching circuit 12 receives the code by the antenna connected to the antenna input terminal indicated by the code. To select the next high-frequency signal
13, and the television signal is received by the antenna for one operation period thereafter (step 103).

Next, the control unit 18c checks whether any of the antenna input terminals with the flag “0” whose reception electric field intensity is equal to or less than a predetermined value (a predetermined ratio or less) as compared with the maximum reception electric field intensity Ml (step S1). 104) If it exists, the count value nj (initial value is 0) corresponding to the antenna input terminal is counted up by 1 (step 105). Note that when the above diversity processing is performed N times (for example, N = 10), the antenna input terminal having a small reception electric field strength (the antenna input terminal where nj = 10) is received at the maximum reception every vertical retrace period. The antenna input terminal of the electric field strength is excluded from the object to be obtained, and the object is obtained every ten vertical retrace periods.

Next, it is checked whether i <9, and if "YES", i is incremented and the processing of step 102 and thereafter is repeated (steps 106 and 107).

However, if i ≧ 9, it is checked whether i = 9 (step 108), and if i = 9, i is incremented and i = 10
(Step 109).

And the next vertical flyback period (the tenth vertical flyback period)
, The codes of all antenna input terminals are sequentially generated in the antenna switching circuit regardless of the flag "0" and "1" to determine the received electric field strength (step 110), and thereafter the maximum received level (maximum received electric field strength) An antenna input terminal of Ml is obtained, and a code indicating the antenna input terminal is output to the antenna switching circuit 12. As a result, the antenna switching circuit 12 causes the antenna connected to the antenna input terminal indicated by the code to receive the television wave during the subsequent scanning period (step 111).

Next, the control unit 18c checks whether there is an antenna input terminal whose flag is “1” and whose reception electric field strength is not less than a predetermined value (not more than a predetermined ratio) compared with the maximum reception electric field strength Ml (step 112). ), If present, the flag of the antenna input terminal is returned to “0” (step 113). Thereafter, the processing of step 104 and thereafter is performed on the antenna input terminal whose flag is “0” (excluding those that have become “0” in step 113).

When the process after step 104 is performed and the process goes to step 108, "NO" is given because i = 10. Accordingly, the control unit checks whether the count value nj (j = 1, 2, 3, 4) is 10 (step 114), and if there is a count value of 10, the antenna input according to the count value is performed. The terminal flag is set to "1" (step 115), and finally, i is cleared to 0 (step 116) and the process returns to the beginning.

In the above description, the antenna input terminal having a small reception electric field strength is switched every N vertical retrace periods. However, the reception electric field strength of the antenna input terminal obtained every N times continues to be the maximum reception electric field strength. On the other hand, when the value is equal to or less than the predetermined value, the antenna input terminal may be switched every M (M> N) vertical blanking periods.

<Effects of the Invention> According to the present invention, the antenna is not connected,
Alternatively, when there is an antenna input terminal having a poor reception state and a small reception electric field strength, if switching to the antenna input terminal is stopped, the number of times of diversity switching in one vertical retrace period can be reduced, Thereby, antenna switching noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part of a television receiver including a television diversity apparatus according to the present invention, FIG. 2 is a flowchart for explaining the diversity processing of the present invention, and FIGS. It is explanatory drawing of a diversity operation. 10a to 10d television antennas 11a to 11d antenna input terminals 12 antenna switching circuit 18 television diversity circuit 18c control unit

Claims (2)

(57) [Claims] An antenna having a plurality of television antennas and sequentially switching antenna input terminals during a beam vertical retrace period to check a reception electric field strength, and using an antenna connected to the antenna input terminal having the maximum reception electric field strength In a television diversity method for receiving television signals, it is determined whether there is an antenna input terminal whose received electric field intensity is equal to or less than a predetermined value with respect to the maximum received electric field intensity. From among the remaining antenna input terminals excluding the terminal, the antenna input terminal having the highest received electric field strength is obtained, and the television signal is received by the antenna connected to the antenna input terminal. Including the removed antenna input terminal, find the antenna input terminal with the highest received electric field strength, and A television wave is received by the connected antenna. When the received electric field strength of the removed antenna input terminal is not less than a predetermined value with respect to the maximum received electric field strength, the antenna input terminal is moved to the maximum received electric field every vertical retrace period. A television diversity method characterized in that a strong antenna input terminal is determined. 2. If the reception electric field strength of the antenna input terminal obtained every N vertical retrace periods continues to be a predetermined value or less with respect to the maximum reception electric field strength, the antenna input terminal is switched M times (M The television diversity method according to claim 1, wherein the antenna input terminal having the maximum received electric field strength is not determined in the vertical flyback period of> N).