JPH0213973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diversity receiving device mounted on a vehicle and suitable for mobile reception.

Since a vehicle-mounted receiving device moves as the vehicle travels, it is susceptible to fading, which inconveniences the reception state. Therefore, in order to improve this problem, a diversity receiving device as shown in Fig. 1 is conventionally installed, which is equipped with multiple antennas, and selects the best antenna from among them to perform reception to prevent deterioration of the reception condition. It was hot.

In FIG. 1, 1a, 1b, 1c, and 1d are receiving antennas, 2 is a switch circuit for selecting one of the antennas 1a to 1d, 3 is a receiver, and 4 is an intermediate frequency output from the receiver 3. Level detector for detecting the level of antenna input, 5a, 5
b, 5c, 5d are antennas 1a, 1b, 1c, 1
Sample and hold circuits corresponding to d, respectively, 6
7 is a maximum value selection circuit that compares the outputs of the sample and hold circuits 5a to 5d and selects the antenna showing the maximum value, and 7 is a controller that controls the switch circuit 2, sample and hold circuits 5a to 5d, maximum value selection circuit 6, etc. It is.

In the above configuration, the controller 7 connects the antennas 1a to 1d to 1a, 1b, 1c, and
While sequentially switching to select in the order of 1d,
In synchronization with this, a signal is generated for causing the corresponding ones of sample holds 5a to 5d to sample and hold the output signal of the level detector 4 which level detects the signal from the receiver 3.

When all of the antennas 1a to 1d are selected and the signal level from each antenna is sampled and held, the controller 7 applies the held content to the maximum value selection circuit 6, and selects the antenna corresponding to the held content showing the maximum value. Select and memorize.
The selected antenna is then connected to the receiver 3 until the next selection operation timing. Such an antenna selection operation is performed instantaneously at predetermined fixed time intervals.

The conventional device is configured as described above, and the antenna selection operation is repeatedly performed at a predetermined constant period T. The period T is determined from the Rayleaf aging phenomenon due to multipath of radio waves, and the antenna selection operation is performed repeatedly at a predetermined constant period T. The distance is determined by the receiving frequency. Therefore, it is sufficient to install a plurality of antennas at predetermined intervals. However, since the fading period changes depending on the moving speed of the receiving device as shown in FIG. 2, there is a problem that as the vehicle speed increases, the period of the antenna selection operation cannot follow the fading period.

The present invention has been made in order to eliminate the problems of the conventional devices described above, and provides a diversity receiving device that can always perform the best reception by setting the optimal timing of antenna selection operation depending on the moving speed. The purpose is to

Hereinafter, embodiments of the present invention will be described based on the drawings, and the same parts as in the conventional example shown in FIG. In FIG. 3, the controller 7 receives, in addition to the output signal of the maximum value selection circuit 6, a clock signal from a clock generator 9 whose oscillation frequency is controlled by the vehicle speed sensor 8. This is different from the one in Figure 1, but the rest is the same.

In the above, the controller 7 normally causes the sample and hold circuits 5a to 5d to sample and hold the output of the level detector 4, and causes the maximum value selection circuit 6 to select the sample and hold value having the maximum value. Based on the result, the switch circuit 2 is operated to connect the maximum input antenna to the receiver 3 until the next comparison operation.

The vehicle speed sensor 8 is used to know the moving speed of the vehicle, and is obtained by extracting the voltage from the speedometer. Based on the output of this sensor 8, the clock frequency of the clock generator 9 is set high when the vehicle speed is high and low when the vehicle speed is low.

The controller 7 performs sample hold and maximum value selection based on the clock input from the clock generator 9, and controls the repetition timing of the comparison operation.
However, each time such as sample hold is not changed.

As described above, by shortening the repetition period of the antenna comparison operation at high vehicle speeds and lengthening it at low vehicle speeds, it changes in accordance with the fading pattern, and when the vehicle speed is zero and the vehicle is stationary, , this period is a predetermined fixed value.

In the above embodiment, the vehicle speed sensor 8 is provided as the control input of the clock generator 9, but by inputting the reception band and reception frequency information together with the vehicle speed, it is possible to prevent fading patterns depending on the moving speed. Even better effects can be obtained by considering not only the change (FIG. 3) but also the change due to frequency.

Further, the vehicle speed sensor does not necessarily have to rely on speedometer voltage detection, and may be obtained from any source as long as the speed can be detected.

As explained above, according to the present invention, the comparison of the output levels of a plurality of antennas and the repetitive synchronization of the selection operation based on the comparison are changed according to the moving speed, so that the fading period depending on the moving speed is Good mobile reception that can respond to and follow changes becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional device, FIG. 2 is a graph showing changes in electric field intensity due to movement, and FIG. 3 is a block diagram showing an embodiment of the present invention. 1a to 1d...Receiving antenna, 2...Switch circuit, 3...Receiver, 4...Level detector, 5a
~5d...Sample hold circuit, 6...Maximum value selection circuit, 7...Controller.

[Claims]

1. A diversity receiver that compares a moving average value and an instantaneous value of received electric field strength using a comparing means, and selectively selects one of the received outputs of a plurality of antennas according to the comparison result. , means is provided for forcibly applying a control signal to the input of the comparison means such that the instantaneous value of the received signal is larger than the moving average value for a predetermined time after the antenna switching command signal is generated. Features receiver.