JPH03270402A - Receiver - Google Patents

Abstract

PURPOSE:To suppress multipath fading by controlling the vertical movement of an antenna based on a detection signal corresponding to a multipath state. CONSTITUTION:An FM intermediate frequency(IF) signal, to which multipath fading generated in mobile reception is loaded, is taken out from the output of a front end 2 and the level of the IF signal is fixed by an AGC amplifier 6. An amplitude component 22 of this signal is taken out by an AM detector 7 and a fluctuated part 21 is detected by a band pass filter(BPF) 8. Since this fluctuated part is enlarged when multipath fading is large at such a time, this fluctuated part is detected by a multipath detector 10. This detected signal is sent to a controller 12 and an antenna 1 is vertically moved by driving a motor 13 in a certain direction so that the fluctuated part of the signal detected by the multipath detector 10 can be reduced. Thus, the multipath fading is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a receiving device that receives radio waves using an antenna.

[Summary of the Invention] The present invention detects a multipath state from an output signal of an antenna using a detector, and based on the detection signal from this detector,
Multipath is suppressed by controlling the antenna drive source to move the antenna up and down.

[Prior Art] In FM reception using a single antenna that does not use a single diper system, during mobile reception, indirect waves arrive at the antenna from various directions due to reflection and diffraction in addition to direct waves.

[Problems to be Solved by the Invention] These radio waves are simultaneously received by an antenna and combined, resulting in interference, multipath fading, and deterioration of communication quality. This situation changes from moment to moment as you move.

On the other hand, since the height of the antenna usually remains fixed, changes in the reception state due to movement (occurrence of multipath fading) directly affect the reception state of the antenna.

An object of the present invention is to provide a receiving device that improves against multipath fading.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides an antenna drive source that moves the antenna up and down, and a multipath drive source that detects a multipath state based on the output signal from the antenna. It is characterized in that it includes a path detector and a control circuit that controls the antenna drive source based on a detection signal from this detector.

[Operation] In the present invention, based on the detection signal according to the multipath state,
Since the vertical movement of the antenna is controlled, multipath fading can be suppressed.

[Example code] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of a receiving device according to the present invention, where l is a receiving antenna, 2 is a front end, and 3 is a receiving antenna.
is an FM intermediate frequency (IF) amplifier, 4 is a multiplexer, 5 is a speaker, 6 is an AGC amplifier, 7 is an AM detector,
8 is band pass filter (BPF) + 9 is comparator, 1
0 is a multipath detector, 11 is a switch, 12 is a controller, and 13 is a motor.

In such a configuration, the front end 2 converts the radio waves received by the receiving antenna 1 into an IP signal and transmits them to the FMIF
The signal passes through an amplifier 3, is converted into an audio signal by a multiplexer 4, and is output as audio from a speaker 5.

By the way, in mobile reception, multipath fading occurs as described above. The IF multiplied signal subjected to multipath fading is extracted from the output of the front end 2, and the IF signal level is made constant by the AGC amplifier 6. As shown in FIG. 2, the AM detector 7 extracts the amplitude component 22 of this signal, and the BPF 8 detects its fluctuation component 21. The greater the multipath fading, the greater this variation. This variation is detected by the multipath detector 10. This detected signal is sent to the controller 1.
2, the motor 13 is driven in a direction in which the fluctuation component of the signal detected by the multipath detector 10 becomes smaller, and the antenna 1 is moved up and down.

FIG. 3 shows how the reception condition changes when the height of the antenna 1 changes.

When a direct wave and a reflected wave U are incident on the antenna 1 as shown in the figure, in case (a), the received signal is threatened by both the reflected wave U and the direct wave. , multipath fading occurs. On the other hand, if the height of the antenna 1 is changed as shown in (b) under the same radio wave condition, the reflected wave U will not be received, and therefore no interference due to the reflected wave U will occur.

In this way, by changing the height of the antenna 1, the receiving conditions of direct waves and reflected waves change, and multipath fading can be reduced.

On the other hand, in weak electric field areas, when the antenna l is lowered, signal reception itself may become impossible before multipath fading occurs. In case this happens,
A comparator 9 compares the reception level VS with the reference voltage VS.

When the reception level vI falls below the reference voltage Vs, the output of the comparator 9 turns off the switch 11, and the output of the multipath detector 10 is not sent to the controller 12.

In this state, the output of the comparator 9 is sent to the controller 12, and the controller 12 controls the height of the antenna 1 so that the reception level V■ becomes equal to or higher than the reference voltage Vs.

The controller 12 receives signals supplied from the comparator 9 or the multipath detector 10 and drives the motor 13, specifically as shown in FIG. 4.

(1) In the case of VX>Vs If the IF output VI input to the comparator 9 is greater than the reference voltage VS, the output V of the comparator 9 as shown in FIG.
, becomes O, and at this time, the switch 11 is in the on state.

On the other hand, when the multipath detector 10 detects a multipath, it outputs a control voltage vM and supplies it to the controller 12 via the switch 11. The controller 12 receives this control voltage vM and drives the motor 13.

Move the antenna up and down in the direction that reduces multipath.

(2) When VI≦Vs If the IF output v■ input to the comparator 9 is smaller than the reference voltage Vs, that is, if the received radio wave is a weak electric field,
As shown in FIG. 4(b), the output Vo of the comparator 9 is Vo
=VH (high level).

This signal turns the switch 11 off.

In other words, the output vM of the detector 10 is not transmitted to the controller 12 regardless of whether the multipath detector 10 detects a multipath.

At this time, the only signal that enters the controller 12 is the output ■H from the comparator 9, and this signal drives the motor 13 and turns the antenna so that the weak electric field state is eliminated (VI>VS). raise.

FIG. 5 shows the configuration of the main parts of another embodiment of the receiving apparatus according to the present invention, in which the switch 11 shown in the drawing is omitted and the switching operation is performed by the controller 12.

FIG. 6 shows an operation flowchart of the controller 12 of FIG.

The operation of the controller 12 will be explained with reference to the flowchart in FIG.

First, it is determined whether the output VO of the comparator 9 is 0 (step 31). Otherwise.

That is, in a weak electric field, Vo =v. In this case, the signal VM from the multipath detector 10 is cut off, and the motor 13 is not controlled by this signal (step 32
). Next, a control signal based on Vo =v is output from the controller 12 to drive the motor 13 (step 33).

At this time, the motor is driven only in the upward direction of the antenna.

From then on, until the weak electric field is eliminated, that is, v■>Vs
Repeat this operation until .

If v,>Vs, that is, if the output ■o of the comparator 9 becomes O, the output vM of the multipath detector 10 is determined (step 34).

If VM = ○, there is no multipath, and the control signal to the motor 10 is O, so the motor stops at that position (Step 35), and the height of the antenna is determined (
Step 36).

If vM=o, a control signal corresponding to VM is sent to the motor to drive the motor (step 37).

At this time, the motor is driven in both upward and downward directions. This operation is repeated thereafter.

[Effects of the Invention] As described above, according to the present invention, it is possible to significantly improve multipath fading.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of a receiving device according to the present invention, Fig. 2 is a waveform diagram explaining the first operation, and Fig. 3 shows changes in reception status when the height of the antenna changes. 4 is a diagram for explaining the driving situation of the motor, FIG. 5 is a configuration diagram of the main part of another embodiment of the receiving device according to the present invention, and FIG.
The figure is a flowchart showing the operation of FIG. 1......Receiving antenna, 9...
...Comparator, 10...Multipath detector, 11...Switch, 12...
...Controller, 13...Motor.

Claims (2)

[Claims] (1) An antenna that receives radio waves, an antenna drive source that moves the antenna up and down, a multipath detector that detects a multipath state based on the output signal from the antenna, and a multipath detector that detects a multipath state based on the output signal from the antenna. and a control circuit that controls the antenna drive source based on the detection signal. (2) A field strength detection means for detecting the received electric field strength based on the output signal from the antenna is provided, and the antenna is moved up and down according to the strength or weakness of the received electric field strength detected by the detection means. 2. The receiving device according to claim 1, wherein the antenna driving source is controlled in such a manner that the antenna driving source is controlled as follows.