JPH0539042U - AM radio receiver - Google Patents

Abstract

(57) [Abstract] [Purpose] When receiving a traffic information station of 1620 kHz, 81
It is to prevent the interference of the 0 kHz FEN station. [Structure] When a traffic information station of 1620 kHz is received, an H output is generated at the A port of the digital tuning system 8 and the transistor Q ₁ is turned on, so that the trap circuit 9 is connected. Therefore, the signal of 810 kHz is attenuated by the trap circuit 9. [Effect] Traffic information station of 1620kHz is weak, 810k
810kHz, even in a radio environment where the FEN station of Hz is strong
Can receive 1620kHz stably without interference.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an AM radio receiver having an improved PLL synthesizer type traffic information station reception function.

[0002]

[Prior Art]

 FIG. 4 shows the configuration of a tuner block of a conventional PLL synthesizer type AM radio receiver. In FIG. 4, 1 is an antenna, 2 is an antenna filter circuit, 3 is an RF amplifier, 4 is a mixing circuit, 5 is an IF amplifier, 6 is a low-pass filter (LPF), 7 is a local oscillator, and 8 is a microcomputer. Shows a digital tuning system.

[0003]

[Problems to be solved by the device]

 In the Tokyo metropolitan area, when an AM radio receiver is receiving a traffic information station with a frequency of 1620 kHz, an area where interference occurs due to interference with a high frequency signal of a specific broadcasting station, for example, FEN (810 kHz) Exists. Traffic information is generally received from a transmitting antenna installed on the road side. In the range where this antenna is installed, radio waves are strong and stable reception is possible. However, when it gets out of this antenna, the number of radio waves increases rapidly. In the case of the Tokyo metropolitan area, the frequency (810) of the specific broadcasting station is strong, so that a harmonic (810 × 2 kHz) of this frequency is reproduced and an interference phenomenon occurs.

This phenomenon will be described with reference to FIG. If a signal of 810 kHz from the specified broadcasting station comes in while receiving a signal of the traffic information station of 1620 kHz from the antenna 1, if an electronic tuner is used as the tuner block, the antenna filter unit 2 Since there is no tuning circuit, the 810 kHz signal is also amplified by the RF amplifier 3, and a double harmonic is generated from this signal by the mixing circuit 4, and an intermediate frequency is generated between this high frequency signal and the oscillation signal from the oscillator 7. Since an IF is created and a signal of 810 kHz is reproduced through the IF amplifier 5, it is difficult to avoid the occurrence of the interference phenomenon. The microcomputer 8 controls the RF amplifier 3 and the oscillator 7 via the LPF 6.

An object of the present invention is to provide an AM radio receiver that improves the reception quality by reducing the interference of the signal of another specific broadcasting station while receiving the signal of the traffic information station. .

[0006]

[Means for Solving the Problems]

 In order to achieve such an object, the present invention provides a detection means for detecting the reception of a signal of the frequency of the traffic information station, and the detection means when the reception of the signal of the frequency of the traffic information station is detected, Attenuating means for attenuating the signal of the reception frequency of the specific broadcasting station.

[0007]

[Action]

 The present invention attenuates the signal of the reception frequency of the specific broadcasting station when the reception of the signal of the frequency of the traffic information station is detected. The reception quality can be improved by reducing the interference of the signal of the station.

[0008]

【Example】

An embodiment of the present invention shown in the drawings will be described below. FIG. 1 shows an embodiment of an AM radio receiver according to the present invention. The same reference numerals as those in FIG. 4 represent the same or similar circuits. In this embodiment, a coil L ₂ and a capacitor C are provided in an antenna filter circuit 2. _The 810 kHz trap circuit 9 consisting of ₁ and the switching transistor Q ₁ are provided. L ₁ is a noise prevention coil. The transistor Q ₁ is driven by the H output of the A port of the digital tuning system 8 composed of a microcomputer when receiving the traffic information station of 1620 kHz. L ₂ and C ₁ of the trap circuit 9 have a value that resonates at 810 kHz, and the impedance at the time of series resonance becomes the minimum so that a signal at 810 kHz can be attenuated.

FIG. 2 shows a flow chart for the system 8 to generate an H output at the A port when the traffic information station (1620 kHz) receives 810 kHz interference. When the traffic information station of 1620 kHz is received, the system 8 controls the oscillation frequency of the local oscillator 7 to be 1620 kHz + 450 kHz = 2070 kHz.

The value 230 obtained by dividing the 2070 kHz by the channel space of 9 kHz is the N value that is the frequency division ratio. When the system 8 reaches the N value of 230 (step ST1), the LPF 6 and the local oscillator 7 are set at step ST2. When the PLL loop including the system 8 and the system 8 is locked to the N value, the step ST3 outputs the A port at the H output. As a result, the switching transistor Q ₁ is turned on, the trap circuit 9 is connected, and the signal of 810 kHz is attenuated. The trap circuit 9 may be provided on the output side of the RF amplifier 3.

Further, the above-described embodiment is based on the method of detecting the traffic information station of 1620 kHz by using the software of the microcomputer of the system 8, but next, only the hardware is used to detect the traffic information of 1620 kHz. Another embodiment of the present invention for detecting stations is shown in FIG.

In the figure, the same reference numerals as those in FIG. 1 denote the same or similar circuits, 9 denotes a mutual reset type touch switch device, and one of the input switches SW1 to SW8, for example, SW1 is turned on to input No.1. When an L level signal (ground) is applied to, the H output (ON) is generated only for the corresponding output No. 1 ', and all other outputs are L outputs (OFF). 1'is connected to the transistor Q ₁ and each input No. ₁ to No. 8 is connected to the system 8. Then, for example, the input switch SW1 is used as a traffic information switch, SW2 to SW6 are used as memory 1 channel to 5 channel switches respectively, SW7 is used as a seek switch, and SW8 is used as a band switch.

Now, when the traffic information switch SW1 is turned on, the output No. 1'becomes an H output, so the transistor Q ₁ is turned on and the trap circuit 9 is connected. Therefore, the 810 kHz signal is attenuated, and the 1620 kHz traffic information station can be clearly received. However, other switches SW2~SW7 are turned on, the output No.1 'is L output, the transistor Q ₁ is not turned on, since the trap circuit 9 does not work, the reception of the normal.

In the above-mentioned embodiment, the interference prevention between the traffic information station of 1620 kHz and the FEN station of 810 kHz has been described, but the present invention is not limited to this, and the frequency of double frequency is widely used. It is also effective as a measure to prevent interference of broadcast signals that are related to each other.

[0015]

[Effect of the device]

 As described above, according to the present invention, even if another specific broadcast is received at the time of receiving the traffic information, the quality of receiving the traffic information can be improved without being disturbed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the above embodiment.

FIG. 3 is a block diagram showing another embodiment of the present invention.

FIG. 4 is a block diagram of a conventional PLL synthesizer AM radio receiver.

[Explanation of symbols]

 2 antenna filter circuit 3 RF amplifier 4 mixing circuit 6 LPF 7 local oscillator 8 digital tuning system 9 trap circuit 10 mutual reset type touch switch device

Claims (3)

[Scope of utility model registration request] 1. An AM radio receiver of a PLL synthesizer system, which detects when a signal of a frequency of a traffic information station is received, and when the signal of the frequency of the traffic information station is detected by the detecting means Attenuating means for attenuating the signal of the reception frequency of the broadcasting station.
M radio receiver. 2. The detection means includes a microcomputer that outputs a signal for attenuation when the frequency ratio of the traffic information station substantially matches a frequency division ratio for receiving the frequency signal. The AM radio receiver according to 1. 3. The mutual reset type touch switch which outputs a signal for attenuation to a corresponding output terminal only when the traffic information station selection switch is operated. The AM radio receiver according to item 1.