JPS6221454B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna device, and more particularly to an FM antenna device effective against multipath interference of FM broadcast waves and an antenna device for AM/FM multiband reception.

FM receivers receive a lot of multi-pulse noise due to the so-called multi-path interference peculiar to FM broadcast waves. This phenomenon is particularly noticeable in vehicle-mounted receivers, so as a countermeasure against multipath interference, a plurality of basic antenna elements are combined to have different directivity of the antennas, and these are switched as appropriate.

Additionally, antennas are generally approximately 1/1/2 of the signal wavelength.
4, the mechanical dimensions of the FM receiving antenna are inevitably large. As mentioned above, in a receiving system using a plurality of antennas, the size of the antenna becomes an obstacle. Especially in FM receiving antennas for cars,
Downsizing is highly desired. In view of these demands, in order to miniaturize the antenna and enable good reception over the entire desired reception band, a tuning circuit using a variable reactance element is added to the outside of the antenna, and tuning is performed along with the tuning operation of the receiver. A device has been proposed that selectively tunes to one of the desired frequency signals.

Furthermore, it is common for multi-band receivers to be able to receive the AM band in addition to the FM band, and for this reason, the AM and FM antennas are
It also becomes necessary to select according to the FM band switching operation, and a switching circuit is required. Furthermore, in order to directly amplify the antenna output at the output end and improve the S/N ratio, an amplifying element is often incorporated into the antenna to form an active antenna. It is also conceivable to add an AGC function to control the degree of amplification of this amplification element according to the received signal level to prevent saturation of the amplification element.

Additionally, a switching circuit is required to switch between multiple FM antenna elements, and a noise detection circuit that detects noise caused by multipath interference and generates a switching control signal is also required to control this switching circuit. be.

If all these circuits are added to the receiver side in order to satisfy each of these functions, the receiver body will need to be modified, which is not preferable. Furthermore, since the connecting cable between the antenna and the receiver becomes long, the reactance caused by this cable cannot be ignored, and good tuning may not be achieved over the entire predetermined reception band. Therefore, it is necessary to downsize the antenna element. There are limits to what can be done. Also, RF which is the antenna output
The signal suffers loss due to the transmission cable, and the S/
This causes deterioration of N.

Therefore, an object of the present invention is to provide an antenna that can satisfy each of the above-mentioned functions while minimizing necessary modifications to conventional receivers (only installation of a tuning voltage supply terminal of the receiver and installation of a detection output terminal of the receiver). The purpose is to provide equipment.

Another object of the present invention is to provide an antenna device that can suppress multipath interference.

Another object of the present invention is to provide an antenna device for multi-band reception.

The present invention will be explained below with reference to the drawings.

The figure is a schematic block diagram showing an embodiment of the present invention, in which numeral 1 indicates the main body of the antenna device, and numeral 2 indicates the main body of the receiver. First, as an antenna element
At least two small whip or loop antennas 11 and 12 for FM band reception are provided, and are arranged adjacently so that their directivities are different from each other, and in addition, for example, a whip antenna 13 for AM band reception is provided. It is being The outputs of the FM antennas 11 and 12 are respectively applied to a variable tuning circuit 14 having a variable reactance element attached to its output end.If the antenna is a whip antenna, the tuning circuit exhibits capacitive reactance in the FM band. Reference numeral 14 indicates an inductive reactance, which is controlled by applying a tuning voltage from the receiver main body 2 so that both reactances cancel each other out to produce tuned resonance over the entire FM band. Since a loop antenna exhibits inductive reactance in the FM band, the tuning circuit 14 has capacitive reactance.

These tuning outputs are applied to the antenna switching circuit 15 together with the output of the AM band antenna 13,
One of these outputs will be selected by the band switching signal and FM antenna switching signal from the receiver 2. This switching circuit 15 is preferably configured to have an amplification function using active elements. Furthermore, an AGC function is added to prevent the amplification element from saturating, and this AGC voltage is also supplied from the receiver body 2.

On the other hand, in the receiver body 2, AM and FM
Tuners 21 and 22 are provided, which receive a selected RF signal from the antenna switching circuit 15 on the antenna side and detect and demodulate it into an audio signal. Both tuners 21 and 22 are selectively selected by an AM/FM band switching circuit 23 constituted by a function switch, but in this example, the configuration is such that this is done by turning on/off the tuner power supply (+B). . This band switching circuit 23
From there, an antenna switching signal is applied to the antenna switching circuit 15 in order to switch the antenna in response to the AM/FM switching. Further, the AM and FM tuners 21 and 22 output an AGC voltage, which is used as an AGC control voltage to the amplification element in the antenna switching circuit 15. Furthermore, FM
In order to tune the antennas 11 and 12 during band reception in response to a tuning operation, a tuning voltage is applied from the FM tuner 22 to the tuning circuit 14 of the antenna device 1 in response to the operation, and a tuning voltage is applied to the tuning circuit 14 of the antenna device 1, which is a variable reactance element. A desired reactance value is obtained by controlling the capacitance value of the capacitive diode.

In order to switch between the FM antennas 11 and 12, a multipath noise detection circuit is provided on the antenna device side 1 to detect noise due to multipath interference. This circuit, for example, is an abbreviation included in the FM detection output in the FM tuner 22.
HPF16 detects noise components over 100KHz
and a noise amplifier 17 that amplifies this noise.
It comprises a noise detector 18 for detecting noise components, a shimmit trigger circuit 19 triggered by the output of this noise detection, and a flip-flop 20 that is set/reset by this shimmit output. This flip-flop output becomes a control signal for the antenna switching circuit 15, and
antennas 11 and 12 for each occurrence of multipath interference.
The RF signal is selectively switched to the RF signal to be sent to the FM tuner 22, and multipath noise is effectively suppressed.

As described above, according to the present invention, in the antenna device, the noise detection circuit is integrated with the antenna element.
Since the antenna switching circuit is built in, the modification on the receiver side requires installing a tuning voltage supply terminal for the tuning circuit of the antenna device, and a detection output terminal (ordinary receiver output may be used) for the multipath noise detection circuit. Just by providing this, it becomes possible to remove multipath noise without having to do much. and,
Since the tuning circuit of the FM antenna can also be configured integrally, there is no need for a connecting cable between the tuning circuit and the antenna, and this cable makes it possible to ignore the reactance component, resulting in miniaturization. Even if a plurality of FM antennas are provided to suppress multipath interference, the antenna device becomes small and suitable for use in a vehicle. In addition, the AM band antenna element is integrated with the FM antenna element in a small size, and the AM/
It also has the advantage of being able to receive both FM bands. By incorporating an amplification element into the antenna side and adding an amplification function, it becomes possible to send out an RF signal with a good S/N ratio to the tuner side.

[Brief explanation of the drawing]

The figure is a block diagram showing an embodiment of the present invention. Explanation of symbols of main parts, 11, 12...FM antenna, 13...AM antenna, 14...tuning circuit, 15...antenna switching circuit, 21...AM tuner, 22...FM tuner.

Claims (1)

[Claims] 1. A plurality of antenna elements, a selection means for selecting one of the reception outputs of the antenna elements, and a multipath noise component included in the detection output of the reception signal in the receiver and detecting the multipath noise component. a multipath noise detection circuit that generates a control signal for controlling the selection operation of the selection means according to a path noise component; and a tuning circuit that supplies a tuning voltage to and tunes a receiver connected to the antenna element. An antenna device comprising: the antenna element, the selection means, the multipath noise detection circuit, and the tuning circuit are integrally configured. 2. A first receiving antenna that receives one receiving band, a plurality of second receiving antennas that receive other receiving bands, and one of the outputs of the first and second receiving antennas is used as a band in the receiver. a first selection means that selects in response to a switching operation; a second selection means that selects one of the outputs of the second receiving antenna; and a multipath noise component included in the detected output of the received signal in the receiver. a multipath noise detection circuit that detects the multipath noise component and generates a control signal for controlling the selection operation of the second selection means according to the multipath noise component; and a multipath noise detection circuit that supplies a tuning voltage to a receiver connected to the antenna element. and a tuning circuit for tuning, and at least the second receiving antenna, the first and second selection means, the multipath noise detection circuit, and the tuning circuit are integrally configured.