JPH0432833Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an on-vehicle receiver.

Conventionally, there has been a device of this type as shown in FIG.

In the figure, 1 and 2 are receiving antennas installed on the vehicle body separated by a predetermined distance, 3 is a switch circuit for switching between receiving antennas 1 and 2, 4 is a receiver, and 5 is a level detector for determining the received electric field strength. 6 is an average value circuit for averaging the level detection output, 7 is a level comparator for comparing the average value with the level detection output, and 8 is the output that is fed back to the switch circuit 3 to be connected to the antenna. A toggle flip-flop to control switching.

Now, by switch circuit 3, receiving antenna 1
Assume that the receiver 4 is connected to the receiver 4.

The output of the level detector 5, which is proportional to the input electric field strength, directly becomes one input of the level comparator 7, and is averaged by the averaging circuit 6 and becomes the other input of the level comparator 7.

Therefore, when the received electric field strength decreases due to the movement of the vehicle, the toggle flip-flop 8 is activated by the output signal from the level comparator 7, and the switch circuit 3 is switched to the receiving antenna 2 on the opposite side.

However, in conventional devices configured in this manner, the receiving antenna does not switch unless the input electric field drops suddenly.

In other words, when the electric field changes slowly, such as when the vehicle is moving at low speed, the receiver's automatic gain control (AGC) may work and level detection may not be performed as desired, or noise components may increase in low input electric fields. The drawback was that it could not detect the drop in the electric field.

Additionally, if you try to switch over a wide input electric field band, the level comparator's resolution of the input electric field will drop, so switching will not occur unless there is a large change in the electric field, and conversely, increasing the resolution will narrow the corresponding electric field range. There were flaws.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved in-vehicle receiving device that overcomes the drawbacks of the conventional devices and can always select the receiving antenna with the stronger input electric field.

Hereinafter, the present invention will be specifically explained with reference to the drawings.

FIG. 2 is a block diagram of an on-vehicle receiver according to an embodiment of the present invention.

What is important in the figure is the level detector 25
A switch circuit 26 is provided between the switch circuit 26 and the level comparator 28, a resistor R and a capacitor C are inserted, and a gate circuit 31 for controlling the switch circuit 23 is provided. A timing pulse generator 30 for control is provided.

Next, the operation of the receiving device of the present invention will be explained.

Assume now that the receiving antenna 1 is connected to the receiver 24 by the switch circuit 23.

Level detection from the receiver 24 is performed by level detector 2.
5, a signal commensurate with the input electric field is obtained,
The switch circuit 26 is normally on the b side. The two inputs of the level comparator 28 are normally at the same potential.

Here, the switch circuit 23 is switched to the receiving antenna 2 side by the pulse generated from the timing pulse generator 30 via the gate circuit 31 only for the time period (large) during which this pulse is generated (see Fig. 3). ).

After a momentary delay, a pulse generated from the timing pulse generator 30 causes the switch circuit 26 to change the time.
Switches from b to a only during t ₂ .

That is, at a certain timing, the switch circuit 23
switches to the antenna on the opposite side from the currently connected antenna, and the switch circuit 26 instantaneously switches from b to a, so the level comparator 28 receives the previous antenna input and the antenna input on the opposite side without any time delay. join.

At this time, if the antenna input on the opposite side is larger, the level comparator 28 inverts and obtains an output.
This output inverts the toggle flip-flop 29 and, via the gate circuit 31, switches the switch circuit 23 to the receiving antenna on the opposite side at a certain timing from the timing pulse generator 30.

FIG. 3 shows a timing chart of the above operation.

In the figure, the receiving antenna is switched from 1 to 2 (input is receiving antenna 2 > same antenna 1),
In this case, the receiving antenna is not switched from 2 to 1.

It should be noted that means other than the above-mentioned embodiments may be used as the input electric field drop detection means.

Furthermore, if the receiver is a television receiver, the timing pulse generator should preferably be a timing system using horizontal and vertical synchronization pulses in order to prevent effects on the screen and to ensure accurate level detection.

As explained above, in this invention, only the input of the currently selected antenna on the opposite side is sampled at regular intervals and the inputs of both antennas are compared, so the antenna with the larger input is always selected. Optimal reception is possible regardless of the range and distribution of the input electric field or the vehicle speed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional receiving device, FIG. 2 is a block diagram of a vehicle-mounted receiving device according to an embodiment of the present invention, and FIG. 3 is a timing chart for explaining the operation of the device shown in FIG.・It is a chat. 1, 2...Receiving antenna, 23...Switch circuit, 26...Switch circuit, 28...Level comparator, 30...Timing pulse generator, 31...
gate circuit.

Claims (1)

[Scope of Claim for Utility Model Registration] A plurality of receiving antennas installed on the vehicle body separated by a predetermined interval, a first switch circuit that switches between the receiving antennas and selects one of them, and a switching circuit that is switched by the first switch circuit. a receiver that receives a signal from the receiving antenna, a level detector that outputs a signal at a level proportional to the input electric field strength of the received signal from the receiver, and a plurality of outputs from the level detector. A second switch circuit that branches and outputs, an averaging circuit that averages the output from the second switch circuit, and each output from the second switch circuit via the averaging circuit is compared. a comparison circuit; and a timing signal generation circuit that supplies first and second switching timing signals to the first and second switch circuits, respectively, and controls switching of each switch circuit; The first switching timing signal controls the first switch circuit to switch from the selected one receiving antenna to another receiving antenna for a predetermined period of time, and the second switching timing signal controls the first switching circuit to switch from the selected receiving antenna to another receiving antenna for a predetermined period of time. 1
occurs a predetermined time after the switching timing signal is generated, and causes the comparison circuit to switch the second switch circuit without any time delay with respect to the output of the averaging circuit before the switching of the second switch circuit. The second switch circuit is controlled to switch so that the output of the subsequent averaging circuit is inputted, and the first
1. An on-vehicle receiver, characterized in that one of the plurality of receiving antennas is connected to the receiver by switching a switch circuit.