JPH1127189A - Fmam tuner having diversity function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain FM receiving performance approximate to that of a 2-input/2-system by using an FMAM tuner of a 2-input/1-system having a diversity function. SOLUTION: In regard to this FMAM tuner having a diversity function, an AM receiving circuit 3 is connected to a sub-antenna 2 via a 1/100 divider 5 when an FM receiving circuit 4 is connected to a main antenna 1. The circuit 3 detects a FM broadcast received by the antenna 1 and also divides the FM broadcast radio waves received by the sub-antenna 2 via the divider 5 to reduce the FM broadcast down to an AM broadcast signal band. Furthermore, the 1/100 frequency signal of the circuit 4 is detected by the circuit 3. Then an antenna switching control part 7 compares the receiving state of the circuit 4 with that of the circuit 3 and then instructs an antenna switching circuit 6 to perform the connection of antennas when the receiving state of the circuit 3 is better than that of the circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FMAM tuner having a two-input one-system diversity function.

[0002]

2. Description of the Related Art Generally, an FM tuner mounted on a moving body such as a vehicle and receiving an FM broadcast has a main antenna and a sub-antenna attached to the moving body, and whichever has a better reception condition of the FM broadcasting radio wave. It has a diversity function of detecting and outputting an FM broadcast using an FM broadcast signal received by an antenna. Such diversity functions include a two-input two-system method and a two-input one-system method.

[0003] Diversity function of the two-input two-system system,
One FM receiving circuit is individually connected to each of the main antenna and the sub-antenna, and the receiving state of the broadcast wave of both antennas is monitored, and the FM receiving circuit connected to the antenna having the better receiving state is monitored. In this method, the detected signal is reproduced as a final FM broadcast.

On the other hand, the diversity function of the two-input one-system system includes a main antenna, a sub-antenna, and one FM receiving circuit. This is a method in which a reception signal of the antenna in a better state is input to an FM reception circuit and detected.

[0005]

In the case of a conventional two-input two-system diversity FM tuner, there is a problem that the receiving performance is high, but the cost is increased because two FM receiving circuits are required. On the other hand, in the case of a two-input one-system diversity FM tuner, the cost is low. However, when the sensitivity of the currently receiving antenna changes, the reception state of the other antenna is not known, and therefore, depending on the radio wave condition, Switching frequently occurs, and there is a problem that the receiving performance is inferior to the case of the dual system.

[0006] The present invention has been made in view of such a conventional problem.
By paying attention to the fact that most also have an M tuner function, by monitoring the FM broadcast reception state of a paused antenna using an AM reception circuit that is paused when receiving FM broadcast, As in the case of the two-input system, the reception states of the FM broadcast radio waves of both antennas are always compared, and the reception signal of the antenna having the better reception state is FM
With a diversity function that can detect and reproduce, it is less expensive than an FMAM tuner with a two-input two-system diversity function and has better reception performance than an FMAM tuner with a two-input one-system diversity function. It is intended to provide an FMAM tuner.

[0007]

An FMAM tuner with a diversity function according to the present invention is connected to a main antenna, a sub-antenna, and the main antenna.
An AM receiving circuit for detecting an M broadcast receiving signal, an FM receiving circuit connected to the main antenna or the sub antenna for detecting the FM broadcast receiving signal, and an AM receiving circuit connected to the main antenna or the sub antenna for receiving the FM broadcast receiving signal;
A 1 / N divider (N is a predetermined numerical value) for dividing the frequency into a frequency of a frequency band, and connecting one of the main antenna and the sub antenna to the FM receiving circuit; And the other one
And an antenna switching circuit connected to the N / N frequency divider. When the FM broadcast is received, the output of the 1 / N frequency divider is connected to the AM receiving circuit, and the AM reception frequency is set to 1 / N of the FM tuning frequency. An AM receiving circuit control unit for tuning a circuit; and an electric field intensity of a tuning frequency signal of the AM receiving circuit is set to the FM level.
An antenna switching control unit for causing the antenna switching circuit to perform a connection switching operation when the electric field intensity of the tuning frequency signal of the receiving circuit is higher than the electric field intensity.

When an FM broadcast signal is frequency-divided into an AM broadcast signal band and received by an AM receiving circuit, it is necessary to determine the electric field strength information of the tuning frequency signal and the magnitude of the AM component noise component such as multipath. it can. Therefore, in the FMAM tuner with the diversity function according to the first aspect of the present invention, when the FM receiving circuit is connected to the main antenna,
An AM receiving circuit is connected to the sub-antenna via a 1 / N frequency divider. Then, the FM receiving circuit detects the FM broadcast radio wave received by the main antenna, and at the same time, the FM broadcast radio wave received by the sub antenna is divided by a 1 / N divider into 1 / N.
By dividing by N, the frequency is reduced to the AM broadcast signal band, and the AM receiving circuit control unit tunes the AM receiving circuit to 1 / N frequency of the tuning frequency of the FM receiving circuit.
The M broadcast circuit receives FM broadcast radio waves of the same frequency as the FM broadcast circuit.

The antenna switching controller compares the electric field strength of the tuning frequency signal of the FM receiving circuit with the electric field strength of the tuning frequency signal of the AM receiving circuit, and finds that the electric field strength of the radio wave received by the AM receiving circuit is stronger. For example, FM on the sub antenna side
It is determined that the reception condition of the broadcast wave has been improved, and the antenna switching circuit switches the main antenna to the AM receiving circuit side and the sub-antenna to the FM receiving circuit side and connects them by the antenna switching circuit.

Thus, in an FMAM tuner having only one FM receiving circuit, while constantly monitoring the receiving state of the FM broadcast radio wave of the two antennas, the receiving signal of the antenna having the better receiving state is monitored. To receive FM broadcast signals.

According to a second aspect of the present invention, there is provided the FMAM tuner with the diversity function according to the first aspect, further comprising:
A first noise extraction circuit that extracts a noise component of a detection signal of the M reception circuit; and a second noise extraction circuit that extracts a noise component of a detection signal of the AM reception circuit, wherein the antenna switching control unit includes: Electric field strength of a tuning frequency signal of the FM receiving circuit, electric field strength of a tuning frequency signal of the AM receiving circuit, a noise component extracted by the first noise extraction circuit, and a noise component extracted by the second noise extraction circuit The necessity of the connection switching operation of the antenna switching circuit is determined by the combination of the above.

The F with diversity function according to the second aspect of the present invention.
The MAM tuner considers the strength of the noise as well as the strength of the FM broadcast wave received by the main antenna and sub-antenna, and detects the FM broadcast signal using the received signal of the antenna with the better reception condition to improve the reception performance. Let it.

[0013]

According to the first aspect of the present invention, there is provided an FMAM tuner having only one FM receiving circuit.
It is possible to detect and reproduce the FM broadcast signal using the reception signal of the antenna having the better reception state while always monitoring the reception state of the FM broadcast wave of the two antennas.
An FMAM tuner with a diversity function having better reception performance than an FMAM tuner with a diversity function of a two-input one-system method can be produced at a lower cost than an FMAM tuner with a diversity function of a system type.

According to the second aspect of the present invention, the strength of the FM broadcast radio wave of the main antenna and the sub antenna and the magnitude of the noise are taken into consideration, and the FM broadcast signal is received by using the received signal of the antenna with the better reception condition. Can be detected and reproduced, so that the receiving performance is further improved.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a circuit configuration of an embodiment of an FMAM tuner with a diversity function according to the present invention. FM with diversity function of this embodiment
The AM tuner is connected to the main antenna 1 and the main antenna 1 of the same specification, which are attached to the right place of the vehicle, for example, the right and left rear windshields, the left and right pillars of the roof, the left and right pillars, etc. An AM receiving circuit 3 for detecting a received signal;
Alternatively, the FM receiving circuit 4 is switched to and connected to either the sub-antenna 2 and detects the FM broadcast receiving signal, and is connected to the main antenna 1 or the sub-antenna 2 so as to convert the FM broadcasting receiving signal to a frequency signal in the AM frequency band. 1/100 frequency divider 5 for frequency division by 1/100, and either one of main antenna 1 and sub antenna 2
An antenna switching circuit 6 is connected to the M receiving circuit 4 and connects the other of the main antenna 1 and the sub antenna 2 to the 1/100 frequency divider 5.

The FMAM tuner with the diversity function further connects the frequency-divided frequency signal output of the 1/100 frequency divider 5 to the AM receiving circuit 3 at the time of FM broadcast reception.
The AM receiving circuit 3 is tuned to a frequency of 1/100 of the tuning frequency, and a signal receiving state of the AM receiving circuit 3 and a signal receiving state of the FM receiving circuit 4 described later are compared. When the reception signal becomes better than the reception state of the FM reception circuit 4, the antenna switching control unit 7 that causes the antenna switching circuit 6 to perform a connection switching operation, and the detection signals of the AM reception circuit 3 and the FM reception circuit 4 are extracted. Noise extraction circuits 8 and 9 for extracting noise components are provided. The antenna switching control circuit 7 includes an AM receiving circuit 3
And the electric field strength information of each tuning frequency signal from the FM receiving circuit 4.

Next, the F with the diversity function having the above configuration
The operation of the MAM tuner will be described. When an AM broadcast signal is received, the AM receiving circuit 3 is directly connected to the main antenna 1, tunes and detects the AM broadcast received signal, and reproduces broadcast audio.

At the time of FM broadcast reception, the circuit connection is as shown in FIG. The antenna switching control circuit 7 normally sets the antenna switching circuit 6 to the state shown in FIG. 1, the reception signal of the main antenna 1 is input to the FM reception circuit 4, and the reception signal of the sub antenna 2 is divided by a 1/100 frequency divider. 5 is input. Further, it is set to the AM receiving circuit 3 so as to tune to a frequency that is 1/100 of the tuning frequency of the FM receiving circuit 4.

Thus, the signal of the tuning frequency set in the FM receiving circuit 4 is detected from the FM broadcast receiving signals received by the main antenna 1, and the FM broadcasting sound is reproduced.

In parallel with the receiving operation of the FM broadcast, the detection signal from the FM receiving circuit 4 is output to the noise extracting circuit 9.
The noise component is extracted from the detection signal by the noise extraction circuit 9 and output to the antenna switching control circuit 7. At the same time, in the AM receiving circuit 3, since the tuning frequency is set to 1/100 of the FM tuning frequency, the signal is received by the sub-antenna 2 and the 1/100 frequency divider 5
From the FM broadcast reception signal divided by 1/100
A frequency signal of 1/100 of the M tuning frequency is detected, and the detected signal is output to a noise extraction circuit 8, where a noise component is extracted, and an antenna switching circuit 7
Is input to The antenna switching control circuit 7 includes:
In addition to the noise component signals from the noise extraction circuits 8 and 9, the magnitude of the detection signal is also input from each of the AM reception circuit 3 and the FM reception circuit 4.

In the antenna switching control circuit 7, these A
The M noise component and the FM noise component are compared, and the AM electric field intensity and the FM electric field intensity are compared to judge whether or not the state of the FM broadcast radio wave of the main antenna 1 and the sub antenna 2 is good. If it is determined that the reception state is better, an antenna switching command is output to the antenna switching circuit 6, and the antenna switching circuit 6 receives the command and connects the main antenna 1 with the main antenna 1 so that the connection is reversed. The connection relationship between the sub-antenna 2, the AM receiving circuit 3, and the FM receiving circuit 4 is switched.

[0022]

[Table 1] Thereby, for example, when the FM broadcast reception signal of the main antenna 1 is input to the FM reception circuit 4 and the FM broadcast is received, and the FM broadcast reception state of the sub antenna 2 becomes better, the antenna switching circuit 6 Performs an antenna switching operation to connect the sub-antenna 2 to the FM receiving circuit 4 and switch the connection so that the main antenna 1 is connected to the AM receiving circuit 3. Conversely, the FM broadcast reception signal of the sub-antenna 2 is
If the FM broadcast reception state of the main antenna 1 becomes better during FM broadcast reception by inputting to the M receiving circuit 4, the antenna switching circuit 6 connects the main antenna 1 to the FM receiving circuit 4, The connection is switched so that the antenna 2 is connected to the AM receiving circuit 3.

As described above, in the FMAM tuner with the diversity function according to the embodiment of the present invention, although it is a two-input one-system system, it is currently used by using an AM receiving circuit provided for AM broadcast reception. The receiving state of the FM broadcast signal by the antenna that is not being monitored is always monitored, and the FM broadcast signal can be received by switching to the antenna having the better radio wave receiving state with good responsiveness in response to the change in the radio wave state of the FM broadcast. The receiving performance is remarkably improved as compared with the conventional two-input one-system type FM tuner with the diversity function.

Moreover, in the case of the present invention, the frequency divider 5, the noise extraction circuits 8 and 9 are added in hardware without adding the FM reception circuit, and the antenna switching control circuit 7 is added.
It is necessary to incorporate the tuning frequency command logic for the AM receiving circuit 3 together with the antenna switching determination logic incorporated in the FM receiving circuit 1.
The cost is lower than the addition of the two, and the addition of the determination logic to the antenna switching control circuit 7 can be achieved by using a microcomputer chip having these determination functions newly added. The cost increase is smaller than in the case of

In the above embodiment, the FM broadcast reception signal is divided into 1/100 by the 1/100 frequency divider 5 and
Although the frequency is reduced to the broadcast signal band and tuning and detection are performed by the AM receiving circuit, the frequency division ratio is not particularly limited as long as the frequency of the FM broadcast received signal can be reduced to the frequency band of the AM broadcast signal.

In the above embodiment, the noise extracting circuits 8 and 9 for extracting noise components from the respective detection outputs of the AM receiving circuit 3 and the FM receiving circuit 4 are provided. Means that the antenna switching determination circuit 7
The antenna switching determination can be performed on the antenna side having the stronger electric field strength only by comparing the strength of the electric field strength at the tuning frequency between the receiving circuit 3 and the FM receiving circuit 4.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of one embodiment of the present invention.

[Description of Signs] 1 Main antenna 2 Sub antenna 3 AM receiving circuit 4 FM receiving circuit 5 1/100 frequency divider 6 Antenna switching circuit 7 Antenna switching control circuit 8 Noise extraction circuit 9 Noise extraction circuit

Claims (2)

[Claims] A main antenna and a sub-antenna; an AM receiving circuit connected to the main antenna for detecting an AM broadcast reception signal;
An FM receiving circuit for detecting an M broadcast receiving signal, and an FM receiving circuit connected to the main antenna or the sub-antenna;
1 / divides M broadcast reception signal to AM frequency band frequency
An N frequency divider (N is a predetermined numerical value), one of the main antenna and the sub antenna is connected to the FM receiving circuit, and the other of the main antenna and the sub antenna is connected to the 1 / N An antenna switching circuit connected to a frequency divider; and an output of the 1 / N frequency divider when receiving an FM broadcast.
An AM receiving circuit control unit connected to a receiving circuit and tuning the AM receiving circuit to 1 / N of the FM tuning frequency; and
When the electric field strength of the tuning frequency signal of the M receiving circuit is stronger than
An FMAM with a diversity function, comprising: an antenna switching control unit for causing the antenna switching circuit to perform a connection switching operation.
Tuner. 2. The FMAM tuner according to claim 1, wherein the first noise extraction circuit extracts a noise component of a detection signal of the FM reception circuit, and a noise component of a detection signal of the AM reception circuit. Second to extract
Wherein the antenna switching control unit includes: an electric field strength of a tuning frequency signal of the FM receiving circuit; an electric field strength of a tuning frequency signal of the AM receiving circuit; and a noise extracted by the first noise extracting circuit. An FMAM tuner with a diversity function, wherein whether or not a connection switching operation is required in the antenna switching circuit is determined based on a combination of a component and a noise component extracted by the second noise extraction circuit.