JPH0583151A - Am radio receiver - Google Patents

Abstract

PURPOSE:To stably receive a desired signal at all times. CONSTITUTION:The receiver is featured as the configuration of back-to-back in which cathodes of varactor diodes D4a, D4b, D5a, D5b, D6a, D6b being components of an antenna tuning circuit 4, a high frequency tuning circuit 5 and a local oscillation circuit 6 are connected together and a tuning voltage is applied to cathode connecting points, and frequency of occurrence of a nonlinear distortion due to a disturbing high frequency signal is reduced and crosstalk is decreased. Thus, the AM radio receiver is realized, in which a desired signal is always received stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic tuning type AM radio receiver for vehicles, homes, portables and the like.

[0002]

2. Description of the Related Art In recent years, electronically tuned AM radio receivers have been widely used in the market regardless of whether they are mounted in vehicles, homes, or portables, and can always receive desired radio waves stably. It has been demanded.

An electronic tuning type AM radio receiver generally uses a variable capacitance method as a tuning method, and a variable capacitance diode is used as a variable capacitance element.

FIG. 4 shows the configuration of a tuning circuit section of a conventional AM radio receiver. In FIG. 4, 1 is an antenna, 2
Is an amplifier, 3 is a frequency mixer, 4 is an antenna tuning circuit,
Reference numeral 5 is a high frequency tuning circuit, 6 is a local oscillation circuit, 7 is a tuning voltage control power supply circuit, and 8 is an intermediate frequency signal output terminal. The antenna tuning circuit 4, the high frequency tuning circuit 5, and the local oscillation circuit 6 are respectively tuning coils L4, L5, L6, tuning capacitors C4, C5, C6, and variable capacitance diodes D4, D.
5, D6. The local oscillator circuit 6 also includes a padding capacitor Cp for tracking error correction. A tuning voltage for controlling the tuning capacitance value is applied to the variable capacitance diodes D4, D5, D6 from the tuning voltage control power supply circuit 7 through resistors R4, R5, R6.

Next, the operation of the above conventional example will be described.
The radio receiver applies a control voltage to the variable capacitance diodes D4, D5 and D6 so as to tune to the frequency to be received, and the high frequency desired signal input from the antenna 1 is the antenna tuning circuit 4 and the high frequency tuning circuit. It is input to the frequency mixer 3 through 5. A local oscillation signal generated by the local oscillation circuit 6 is input to the frequency mixer 3, mixed with a high frequency signal to generate an intermediate frequency signal, and output to the intermediate frequency signal output terminal 8. Thus, even in the conventional AM radio receiver, if it is tuned to the signal to be received, it can be tuned and received at an arbitrary reception frequency.

[0006]

However, in the above-mentioned conventional AM receiver, each tuning circuit has a tuning variable capacitance diode.
Since only one signal is used, when an interfering high frequency signal having a relatively large electric field strength is input to each tuning circuit in addition to the desired high frequency signal to be received, the interfering high frequency signal is changed to a variable capacitance diode. Instability that causes interference such as causing non-linear distortion when passing through, or causing excessive side voltage to be superimposed on the tuning voltage to change the tuning capacity, that is, changing the tuning frequency and distorting the desired signal. There was a problem with receiving.

The present invention solves such a conventional problem, and is an excellent A that can always stably receive a desired signal.
It is intended to provide an M radio receiver.

[0008]

In order to achieve the above object, the present invention has an even number of cathodes connected to each other as variable capacitance means of at least a tuning circuit closest to an antenna among a plurality of tuning circuits. One or more sets of variable capacitance diodes are used, and a tuning voltage is applied to the cathode of each variable capacitance diode to tune to the reception frequency.

[0009]

The present invention has the above-described structure, and by supplying a tuning voltage to the commonly connected cathode section, it is possible to tune and receive at an arbitrary frequency. Even if an interfering high frequency signal having a relatively high electrolytic strength other than the desired high frequency signal to be received is input to each tuning circuit, an even number of variable capacitance diodes are connected to the tuning circuit. Since there are multiple sets, the frequency of non-linear distortion that occurs when an interfering high-frequency signal passes through a variable capacitance diode can be halved, and an excessive AC voltage is superimposed on the tuning voltage, resulting in a tuning capacitance. Of the desired signal caused by the change of the tuning frequency and the tuning frequency are canceled by the even number of variable capacitance diodes, so that the interference phenomenon is small and the desired high frequency signal can always be received.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of one embodiment of the present invention. In FIG. 1, the same reference numerals as those in FIG. 4 denote the same parts as those in FIG. In the embodiment shown in FIG. 1, the variable-capacitance diodes constituting the antenna tuning circuit 4, the high-frequency tuning circuit 5, and the local oscillation circuit 6 are respectively back-to-back type variable-capacitance diodes D4a and D4.
4b, D5a, D5b, D6a, D6b.

Next, the operation of the above embodiment will be described. Similar to the conventional example, the AM radio receiver adjusts the tuning voltage from the tuning voltage control power supply circuit 7 via the resistors R4, R5 and R6 so as to tune to the frequency to be received. -Do D4a, D4b, D
In addition to 5a, D5b, D6a and D6b, it is possible to tune to any reception frequency.

Further, even if an interfering high frequency signal having a relatively high electric field strength is input to each tuning circuit in addition to the desired high frequency signal to be received, a back-to-circuit in which a cathode is commonly connected to each tuning circuit. Variable capacitance diode D with Back system configuration
Since 4a, D4b, D5a, D5b, D6a, D6b are connected, the frequency of non-linear distortion can be halved when the disturbing high frequency signal passes through the variable capacitance diode, and the tuning voltage becomes excessive. The distortion of the desired signal that occurs when the tuning capacitance changes and the tuning frequency changes when a large AC voltage is superimposed is the Back-To-
The two variable capacitance diodes connected in the Back system cancel each other out. Therefore, the interference phenomenon is small and the desired high frequency signal can always be stably received.

FIG. 2 shows the configuration of another embodiment of the present invention. In FIG. 2, the same reference numerals as those in FIG. 4 denote the same parts as those in FIG. The antenna tuning circuit 4 of this embodiment includes a tuning coil L4, a tuning capacitor C4 and a Ba.
ck-To-Back type variable capacity diode D4a, D4b,
It is configured using D4c and D4d.

In this embodiment, only the variable capacitance diode used for the antenna tuning circuit 4 uses the Back-To-Back system configuration, and the other high frequency tuning circuit 5 and the local oscillator circuit 6 use the conventional system as they are. There is. The variable-capacitance diodes D4a, D4b, D4c, and D4d of the antenna tuning circuit 4 employ two variable-capacitance diodes in series and in parallel, and are supplied from the tuning voltage control power supply circuit 7. Due to the tuning voltage, the total capacitance value of the variable capacitance diode for each of the antenna tuning circuit 4, the high frequency tuning circuit 5, and the local oscillation circuit 6 becomes the same value so that the tracking error in the reception band is not affected. It has become.

In the embodiment of FIG. 2 as well, similar to the configuration of FIG. 4, the tuning voltage control power supply circuit 7 controls the tuning capacitance value via the resistors R4, R5 and R6 so as to tune to the frequency to be received. Variable tuning diode D
In addition to 4a, D4b, D4c, D4d, D5 and D6, it is possible to tune to any reception frequency. Further, even if an interfering high frequency signal having a relatively high electric field strength is input to each tuning circuit in addition to the desired high frequency signal to be received, a variable capacitance diode D4a, to which a cathode is commonly connected to the antenna tuning circuit, D4b, D4c and D4d are Ba
Since it is connected to the ck-To-Back system configuration, it is possible to halve the frequency of non-linear distortion that occurs when the interfering high-frequency signal passes through the variable capacitance diode.
Distortion of the desired signal caused by superimposing an excessive AC voltage on the tuning voltage, changing the tuning capacitance and changing the tuning frequency,
This cannot occur because the antenna tuning circuit 4 cancels each other by two variable capacitance diodes each in series and parallel.

Further, an interference high frequency signal is also applied to the high frequency tuning circuit 5, but since the antenna tuning circuit 4 has a high frequency band selectivity, the level of the interference high frequency signal is attenuated when passing through the antenna tuning circuit 4, so that the high frequency is high. Even if the variable capacitance diode of the tuning circuit 5 has the same configuration as the conventional configuration, nonlinear distortion occurs when passing through the variable capacitance diode, and an excessive AC voltage is superimposed on the tuning voltage to change the tuning capacitance. There is an effect that a desired high frequency signal can be always received stably with little interference phenomenon without adding such a large disturbing high frequency signal.

FIG. 3 shows the configuration of still another embodiment. FIG. 3 shows an embodiment of an AM radio receiver of non-antenna type. In FIG. 3, the same reference numerals as those in FIG. 4 denote the same parts as those in FIG. In FIG. 3, 9 is an antenna amplifier, 10 is a high frequency amplifier, 11 is a first high frequency tuning circuit, and 12 is a second high frequency tuning circuit, which are tuning coils L11, L12, tuning capacitors C11, C12, variable capacitance diode D11a, and It is composed of D11b, D11c, D11d and D12. In the embodiment shown in FIG. 3, only the antenna tuning circuit is of non-tuning type, and the AM radio receiver is tuned to the frequency to be received as in the conventional example of FIG. To resistance R1
The tuning voltage for controlling the tuning capacitance value via 1, R12, R6 is a variable capacitance diode D11a, D11b, D11c, D11.
In addition to d, D12 and D6, it is possible to tune to any reception frequency. Even if a disturbing high frequency signal having a relatively high electric field strength is input to each tuning circuit in addition to the desired high frequency signal to be received, the first high frequency tuning circuit 11
A variable capacitance diode D11 with a cathode connected in common
Since a, D11b, D11c, and D11d are connected by the back-to-back method, it is possible to halve the frequency of non-linear distortion that occurs when an interfering high-frequency signal passes through the variable capacitance diode. It is the antenna tuning circuit 4 that an excessive AC voltage is superimposed on the tuning voltage to change the tuning capacitance, that is, the tuning frequency changes to distort the desired signal.
This cannot occur because the two variable capacitance diodes in each of the series and parallel cancel each other.

Further, although the interference high frequency signal is also applied to the second high frequency tuning circuit 12, the level of the interference high frequency signal passes through the first high frequency tuning circuit 11 since the first high frequency tuning circuit 11 has a high frequency band selectivity. Therefore, even if the variable capacitance diode of the second high-frequency tuning circuit 12 has the conventional configuration, the nonlinear distortion occurs when passing through the variable capacitance diode and an excessive AC voltage is applied to the tuning voltage. The effect of being able to receive the desired high-frequency signal constantly with little interference phenomenon, without adding a large interfering high-frequency signal in which the tuning capacitance is changed due to the superposition of the signal.

As described above, according to the present invention, regardless of the antenna tuning type or non-tuning type, the back-to-type variable capacitance diode forming the tuning circuit closest to at least the antenna among the plurality of tuning circuits is provided. -By connecting to the Back method,
The above-mentioned unique effect is obtained.

[0020]

The present invention has the above-mentioned structure, and the variable capacitance diode of the tuning circuit closest to at least the antenna of the electronic tuning type AM radio receiver is a back-to-back type.
Since it is configured as a system, it is possible to tune to an arbitrary frequency by supplying a tuning voltage to the commonly connected cathode section.
Can be received. Even if an interfering high-frequency signal having a relatively high electrolytic strength other than the desired high-frequency signal to be received is input to each tuning circuit, an even number of variable capacitance diodes with a common cathode are connected to each tuning circuit. Since a plurality of interfering high-frequency signals are connected, the frequency of non-linear distortion that occurs when a disturbing high-frequency signal passes through the variable-capacitance diode can be halved, and an excessive AC voltage is superimposed on the tuning voltage. , And the distortion of the desired signal caused by a change in the tuning frequency cannot occur because they cancel each other out by the even number of variable capacitance diodes,
There is little interference phenomenon, and there is an effect that a desired high frequency signal can always be stably received.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a tuning circuit of an AM radio receiver according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram of a tuning circuit according to a second embodiment of the present invention.

FIG. 3 is an electric circuit diagram of a tuning circuit according to a third embodiment of the present invention.

FIG. 4 is an electric circuit diagram of a tuning circuit of a conventional AM radio receiver.

[Explanation of symbols]

 1 antenna 2 amplifier 3 frequency mixer 4 antenna tuning circuit 5 high frequency tuning circuit 6 local oscillation circuit 7 tuning voltage control power supply circuit 8 intermediate frequency signal output terminal 9 antenna amplifier 10 high frequency amplifier 11 first high frequency tuning circuit 12 second high frequency tuning circuit

Claims (4)

[Claims] 1. A variable capacitance means of a tuning circuit at least closest to an antenna among a plurality of tuning circuits, which is constituted by an even number of one or a plurality of sets of variable capacitance diodes in which cathodes are connected to each other, and each variable An AM radio receiver characterized in that a tuning voltage is applied to the cathode of a capacitance diode to tune to a reception frequency. 2. An antenna tuning circuit, a high-frequency tuning circuit, and a local oscillation circuit, each of which is composed of an even number of one or more sets of variable capacitance diodes having cathodes connected to each other as variable capacitance means, and each of the variable capacitances described above. An AM radio receiver characterized in that a tuning voltage is applied to the cathode of a diode to tune to a reception frequency. 3. An even number set or plural sets of variable capacitance diodes having an antenna tuning circuit, a high frequency tuning circuit, and a local oscillation circuit, wherein the cathode tuning circuits are connected to each other as variable capacitance means of the antenna tuning circuit. An AM radio receiver characterized in that a tuning voltage is applied to the cathode of each variable capacitance diode to tune to a reception frequency. 4. An antenna amplifier connected to the antenna,
A high-frequency amplifier circuit connected to the output terminal of the antenna amplifier, and the variable-capacitance means of the high-frequency amplifier circuit is configured by an even number of one or more sets of variable-capacitance diodes in which cathodes are connected to each other. An AM radio receiver characterized in that a tuning voltage is applied to the cathode of each variable capacitance diode to tune to a reception frequency.