JPS60140934A - Diversity receiver - Google Patents

Abstract

PURPOSE:To select an antenna having a larger reception output level at all times even at a weak electric field by controlling a switch in response to the comparison output. CONSTITUTION:In using a hybrid transistor transformer circuit as an example of a phase difference synthesizer 9, the reception strength of antennas 1, 2 is taken as A, B and the strengths C, D appearing at an output of the synthesizer 9 are expressed as C=(B+A)...(1) and D=(A-B)...(2). An instantaneous mean value to be compared is an instantaneous mean value of Equation (1) or (2), then if the output of the antenna having better sensitivity is decreased due to fading at a weak electric field, the antenna is switched to the other antenna with lower sensitivity, and since the reference level is not the moving means value of the fading output with the low sensitivity as in case of a conventional receiver, but the moving mean value of the signal expressed in Equation (1), then the instantaneous means value of the antenna with lower sensitivity is decreased less than the said moving mean value the moving mean value and the antenna is made possible to be switched to the antenna with better sensitivity. Moreover, even if the reception strength of each antenna is not detected at all times, the antenna having the larger reception strength is selected.

Description

[Detailed Description of the Invention] Technical Field This invention relates to a diversity receiver, and particularly to a vehicle-mounted FM receiver.
The present invention relates to a diversity receiver suitable for use in a receiver.

Headlighting technology As schematically shown in FIG. 1, the conventional diversity reception system supplies the reception outputs of two diversity reception antennas 1 and 2 to an antenna switching circuit 3, and selects the antennas selected by the switching circuit 3. The received signal is input to one receiving section 4. For example, a signal meter output from the receiving section 4 is derived, and an instantaneous average value and a moving average value of this meter output are obtained by average value circuits 5 and 6, respectively. The levels of both average values are compared by a level comparator 7, and the switching state of the switch 3 is controlled by the comparison output. Note that 8 indicates a signal meter circuit.

Here, compared to the time constant for integration of the instantaneous average value circuit 5, that of the moving average value circuit 6 is set to be much larger.

In this configuration, if antenna 1 is currently selected and the received signal of antenna 1 suddenly drops due to the Lehle fading phenomenon, and the instantaneous average level falls below the moving average level, comparator 7 detects this. A control signal is generated so that the switch 3 selects the reception output of the antenna 2.

Here, in the case of in-vehicle use, there is one antenna on the outside of the car,
In cases where the sensitivities of both antennas are different, such as when other antennas are installed inside the antenna 11, there is a drawback that the antenna may be fixed to the inner antenna with lower sensitivity in a weak electric field area. .

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned drawbacks of conventional devices, and its purpose is to always select the antenna with the higher received output level even in a weak electric field. The purpose of the present invention is to provide a diversity receiver.

The diversity receiver according to the present invention includes a plurality of receiving antennas, a combining means for performing phase difference synthesis of each receiving output of the antennas, and outputting the sum and difference components of these receiving outputs, and an output of the combining means. The switching device is provided with a switching device that selectively derives the output, and a comparison means that compares the levels of the moving average value and the instantaneous average value of the output of the switching device, and the switching device is controlled according to the comparison output. It is characterized by

IL Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a circuit diagram of an embodiment of the present invention, and parts equivalent to those in FIG. 1 are designated by the same reference numerals. In the figure, the received outputs A and B of the antenna 1.2 are respectively supplied to a phase difference combiner 9, and the two outputs C and D of this combiner 9 are the sum and difference of both inputs A and B. Composite outputs are respectively derived. This combined output C1D is the two-man power of the switch 3, and the other circuit configurations are the same as the example shown in FIG.

When a hybrid transformer circuit as shown in FIG. 3 is used as an example of the phase difference synthesizer 9, the antennas 1.2
Let A and B be the received intensities of , the intensities C and D appearing at the output of the combiner 9 are as follows.

C=(B-1-A) ・・・・・・(1)D=(B
-A) ...... (2) When A and B show Lehle fading, C and D similarly show Lehle fading, and their moving average values are both equal. Therefore, for the output level of the moving average value circuit 6, the moving average value of equation (1) (that is, also equation (2)) becomes the comparison reference level of the comparator 7, regardless of the switching state of the switch 3.

The instantaneous average value to be compared is the instantaneous average value of addition equation (1) or equation (2). Therefore, if the output of the antenna with higher sensitivity in a weak electric field decreases due to fading, the other sensitivity However, the reference level is not the moving average value of the fading output of the less sensitive antenna as in the past, but the moving average value of the signal in equation (1). The instantaneous average value becomes lower than this moving average value, making it possible to switch to an antenna with better sensitivity.

In this embodiment, the number of antennas is two, but it may be three or more. Further, as an example of the phase difference synthesizer 9, the third
It is not limited to what is shown in the figure.

-1 5- As described above, according to the present invention, even if all diversity antennas do not have the same characteristics, and even if the reception strength of each antenna is not always detected, the antenna with the greater reception strength can be selected. Since the signals are switched, it is possible to perform low-cost and reliable diversity reception.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional diversity receiver, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a circuit diagram of the phase difference synthesizer shown in FIG. Explanation of symbols of main parts 1.2... Antenna 3... Switcher 5... Instantaneous average value circuit 6... Moving average value circuit 7... ... Comparator 9 ... Phase difference synthesizer 6-

Claims (1)

[Claims] A plurality of receiving antennas, a combining means for performing phase difference synthesis of each received output of the antennas and outputting a sum and a difference component of these received outputs, and a switch for selectively deriving the output of the combining means. and a comparison means for comparing the levels of a moving average value and an instantaneous average value of the output of the switching device, and controlling the switching device according to the comparison output. Machine.