JPS6089179A - Switching device of television antenna - Google Patents

Abstract

PURPOSE:To decrease a noise in a sound signal by avoiding the sampling of a reception signal in a direction directing a minimum input level until the directing direction of a maximum input level in plural television antennas is changed. CONSTITUTION:Antennas 1-4 are switched sequentially by a signal S1 from a control circuit 11 during the vertical blanking period, the signal S1 closes switches SW1-SW4 of a sample and hold circuit 12 at the same time so as to hold a detected output of the reception signal and its voltage is inputted to a minimum level antenna detection circuit 13 and a maximum level antenna detection circuit 14 in an on-vechile television receiver. The circuits 13, 14 output detection signals Sa, Sb of minimum and maximum level respectively, they are latched, the signal Sa is inputted to an excluding circuit 9 and the signal Sb is inputted to the circuit 11 and a change detection circuit 18. The antenna is sampled during the next vertical blanking period and the circuit 11 opens the SW corresponding to the antenna detecting the signal Sa in the SW1-SW4 by the signal Sd of the circuit 19 while the antenna detecting the signal Sb is unchanged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a television antenna switching device that is effective for use in a vehicle-mounted television antenna mounted on a mobile object such as an automobile.

BACKGROUND TECHNOLOGY AND PROBLEMS Conventionally, in-vehicle TV reception systems have been used to switch between multiple antennas, each with different directivity, and select the antenna with the best radio wave condition, or to change the directivity of 11 antennas. There are known switching methods. As a system using a plurality of antennas, an antenna switching device shown in FIG. 1 is conventionally known.

In FIG. 1, four antennas (I l (21t3
1 (41 indicates the directivity 1, 2, 3, . . . shown in FIG. 2, respectively).
It has 4. These antennas (11121+3
+ i4) is subjected to 711th sampling for each antenna by the switching circuit (5) during a predetermined H period (H: horizontal scanning period) in the vertical blanking period. This sampling is performed at the timing shown in FIG. 6 by the switching signal S1 applied from the control circuit U. This switching circuit (5) is connected to the antenna (11 to
In step (4), one of the signals to be received is selected. The signal obtained from the switching circuit (5) is tuned by the tuner (6), converted to an intermediate frequency signal, and then sent to the detection circuit (
7) is detected. This detection output is supplied to the image receiving circuit (8), as well as to the synchronous separation circuit (9) and the maximum level antenna detection circuit 0ω. The above detection circuit (1
0) is a synchronization separation circuit (9) which detects the detection output corresponding to the received signal of each antenna (11 to (4)) sequentially obtained by the above-mentioned sampling during the predetermined H period.
The antenna is detected based on the synchronization signal applied from the antenna, and the antenna from which the maximum level is obtained among the detected detection output levels is detected. Based on this detection, the control circuit (Iυ
applies a switching signal s1 to the switching circuit (5) for selecting the antenna that provides the maximum level of detection output. As a result, the switching circuit (5) selects the antenna that provides the maximum level until the next sampling is performed. When the next predetermined H period comes, the control circuit (5) forms a switching signal s1 for sampling again based on the synchronization signal and applies it to the switching circuit (5).

Note that the above sampling is normally performed for each even or odd field.

According to the above, since the antenna with the strongest electric field strength is always selected during the video period of the received signal, it is possible to always perform good reception. Further, since the above sampling is performed during the vertical blanking period, the influence of sampling does not appear on the screen. However, in the case of audio signals, during the sampling period, lightning, sampling from weak antennas with different intensity, and noisy signals are momentarily mixed in, which appears as buzz noise. Sometimes.

OBJECTS OF THE INVENTION The present invention provides an antenna switching device for selecting the pointing direction of an antenna used in a vehicle-mounted television, etc., which reduces noise in audio signals.

Summary of the Invention The present invention is characterized in that the received signal in the directional direction in which the minimum input level is obtained is not sampled during a period until the directional direction in which the maximum input level is obtained changes. This makes it possible to reduce the aforementioned audio noise in this type of antenna switching device.

Embodiment FIG. 4 shows an embodiment of the present invention. Parts corresponding to those in FIG. As in the case of FIG. 1, it is assumed that each of the antennas has directivity 1 to 4 shown in FIG. 2.

In FIG. 4, the detection output of the detection circuit (7) is added to the image receiving circuit (8) and the synchronous separation circuit (9).
11 is added to the sample and hold circuit (12). This sample hold circuit (121 is a switch SW1 to SW5W)
4sXiv1° to 5W14, diodes D1 to D4, capacitors 01 to 04, etc., as shown in the figure. The switches SW and SW4 are connected to the antenna (II).
~(4) Corresponding to that, the switching is performed in synchronization with the switching operation of the switching circuit (5) by the switching signal S1 from the control circuit (1υ). The level of each sampled detection output is determined by the diode D.

~1)4 to capacitors 01 to C4. The switches 5w11 to 5W14 are closed for a predetermined period of time by a switching signal S2 from the control circuit U immediately before the next sampling, thereby discharging the capacitors 01 to C4.

The detection output levels held in the capacitors 01 to C4 corresponding to the antennas m to (4) are applied to the minimum level antenna detection circuit 03) and the maximum level antenna detection circuit. The detection circuit 03) detects the antenna with the minimum input level and outputs a detection signal 8a indicating the antenna. This detection signal Sa is applied to the latch circuit (1
It is latched at 51. Further, the detection circuit (14) detects the antenna with the maximum input level and outputs a detection signal sb indicating the antenna. This detection signal sb is the latch circuit 0
6) is latched.

Now, assume that the antenna with the maximum input level is the antenna (11) with the directivity 1 in Figure 2, and the antenna with the minimum input level is the antenna (31) with the directivity 6 in Figure 2.Latch circuit (Antenna obtained from 161 (1
The detection signal sb indicating 1 is applied to the change detection circuit 08) and to the control circuit 0υ. Control circuit (11)
In response to the above detection signal sb, after the sampling is completed, a switching signal S1 for selecting the antenna (11) is applied to the switching circuit (5). Sa is added to exclusion circuit four.

While the switching circuit (5) is selecting the antenna (1), the switching circuit (5) is turned on again to perform the next sampling.
) and switches SW1 to SW4 are switched,
At this time, the sampling of the received signal of the antenna 13) with the minimum input level and the sampling of the detection output corresponding to this antenna (31) are not performed. That is,
In the switching circuit (5), the antenna (3) is not selected and only the received signal of the antenna (11+21 (41) is sampled.
), the switch SW3 is never closed, and only the switches 8W4.5Vv2 and SW4 are closed in sequence. As a result of this sampling, if the antenna (11) maintains the maximum input level, the antenna (3) with the minimum input level will be the same in the next sampling as described above.
) are excluded from Sunblink. In this way, as long as the antenna (1) with the maximum input level does not change, the antenna (31) with the minimum input level is excluded from the sampling target. This exclusion operation is based on the signal Sd from the exclusion circuit. It will be carried out.

As a result of sampling after antenna (1) continues to be the antenna with the maximum input level, antenna (1)
When the detection circuit detects that ; is no longer the antenna with the maximum input level, the content of the detection signal sb changes,
This change is detected by the change detection circuit (18
) is detected. This detection signal 8c is added to the rejection circuit θ9), and the rejection circuit ((wings are antennas (3)
) is applied to the control circuit Uυ.

In response to this, the control circuit aυ selects four antennas (1) to (4) in the next sampling period, and
It outputs a switching signal S for closing the switches SW, ~sw4. As a result, four sampling data are obtained, and these sampling data are applied to the detection circuit (+3) a41. As a result, antenna (2), for example, is detected as the antenna with the maximum input level, and antenna (4), for example, is detected as the antenna with the minimum input level.
) are detected, and a detection signal 5a1sb is obtained, respectively.
1 Ru. The control circuit H controls the antenna (2) at the maximum input level until the next sampling is performed according to the detection signal sb.
A switching signal S1 for selecting is output. At the same time, the exclusion circuit (101) applies a signal Sd to the control circuit U based on the detection signal Sa to exclude the antenna (4) from being sampled during the next sampling period.

In the next sampling period, antennas other than antenna (4) (It(21+31) are selected) until the ratio signal sb changes.

As described above, in this embodiment, if the period until the antenna with the maximum input level changes to another antenna (the period during which the detection signal sb is constant) is called the stable period, then in this stable period, , the antenna with the lowest input level is excluded from the sampling pair. Therefore, during the stable period, a noisy audio signal is not mixed in from the antenna with the minimum input level, and the noise of the audio signal can be reduced as a whole.

In addition, in this embodiment, the iron with which the detection signal sb has changed,
All antennas are sampled once, and the antenna with the minimum input level is determined from the four sampled data obtained at this time, and this antenna is excluded from the next sampling. After sampling several times, the antenna with the minimum input level may be determined and this 11 may be eliminated. In addition, this embodiment is a case in which four antennas (11 to (4)) each having different directivity are selected as shown in FIG. For example, the present invention can be applied to the case where the directivity that provides the maximum input level is selected by sequentially switching the compatibility as shown in FIG. It can be applied when switching the orientation direction of the number of bubbles related to a TV antenna and selecting the orientation direction that provides a fan-sized input level.Also, it can be applied to select the orientation direction that provides the maximum input level and the orientation that provides the minimum input level. The directions are opposite to each other (the relationship between 1 and 6 in Figure 2 and the relationship between 2 and 4)
(relationship), it is not necessarily necessary to provide the minimum input level antenna detection circuit. Car tlil with seed antenna switching device? It is possible to reduce audio noise from television, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a diagram showing antenna directivity, FIG. 6 is a timing chart showing the principle of antenna switching operation, and FIG. 4 is a diagram showing the 'A' of the present invention.
A block diagram showing an example of Jai.・・・・・・Switching circuit un・・・・・・・・・・・・・・・・・・Control circuit (I2・・・・・・・・・・・・・・・Sample hold circuit 03)・・・・・・・・・・・・・・・
・The thickest antenna detection circuit (141...
・・・・・・・・・−・Minimum level antenna detection circuit (181・・・・・・・・・・・・・・・Change detection circuit 0)・・・・・・・・・It is a selection circuit. Agent Masaru Ueya Yoshio Tsunekako Toshiki Sugiura

Claims (1)

[Claims] By sampling the received signals obtained from multiple pointing directions of the TV antenna 110 times during the vertical blanking period, the pointing direction where the maximum input level can be obtained is detected, and based on this detection, until the next sampling is performed. In the television antenna switching device, the directional direction that provides the maximum input level is selected during the period in which the directional direction that provides the minimum input level is selected during the period when the directional direction that provides the maximum input level does not change. 1. A television antenna switching device characterized in that a reception signal from a television antenna is excluded from sampling targets.