JPS6233407Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an FM/AM receiver capable of receiving both FM stereo broadcast and AM stereo broadcast, and particularly relates to a stereo display means.

FM stereo broadcasting started in 1960, and FM
Stereo receivers are also becoming more popular. On the other hand, AM stereo broadcasting is not currently being implemented, but experiments have been conducted in the past and it is considered to be promising in the future.

Therefore, FM/AM receivers that can receive AM stereo broadcasts as well as FM stereo broadcasts are being developed.

There are many points to consider when developing this FM/AM receiver, but one is how to simplify the circuit configuration and reduce costs, and the other is how to make the stereo display easier to see. That's it.

This idea was made in view of the above points,
An object of the present invention is to provide an FM/AM receiver that can reduce costs by displaying stereo signals when receiving FM stereo broadcasts and when receiving AM stereo broadcasts using a single display, and also makes the stereo display simple and easy to see. .

An embodiment of this invention will be explained below with reference to the drawings, but before that, we will explain how it works when receiving FM stereo broadcasts and how it works when receiving AM stereo broadcasts.
The principle of stereo display when receiving stereo broadcasts will be explained.

The FM stereo signal is amplitude-modulated by the main channel signal, which is the sum of left and right signals, and the difference signal.
It consists of a sub-channel signal which is a 38KHz DSB wave and a 19KHz pilot signal for generating the 38KHz carrier necessary to demodulate this sub-channel signal. Therefore, when receiving FM stereo broadcasting, the pilot signal is detected and stereo display is performed. On the other hand, in the Magnabox system, the AM stereo signal is frequency-modulated on the carrier by an identification tone (hereinafter referred to as ID tone), further phase-modulated by the left and right difference signal, and once passed through a limiter circuit. It is created by amplitude modulating the sum signal. Therefore, when receiving AM stereo broadcasts, the carrier is set to PM.
Stereo display is performed by detecting the ID tone obtained when the wave is detected.

FIG. 1 is a block diagram showing an embodiment of the FM/AM receiver of this invention. In this figure, 1 is
FM front end, 2 connected to its output
FM intermediate frequency amplifier, 3 is a limiter circuit connected to its output, 4 is an FM detector connected to its output, 5 is a stereo demodulator connected to its output, and these constitute an FM receiving section. Ru.
Further, 6 is an AM front end, 7 is an AM intermediate frequency amplifier connected to its output, 8 is an AM detector connected to its output, and 9 is a PM detector similarly connected to the output of the AM intermediate frequency amplifier 7. 10 is an ID tone detector connected to its output, 11 is an ID tone detector connected to its output.
This is a matrix circuit connected to the outputs of the AM detector 8, PM detector 9, and ID tone detector 10, and these constitute an AM receiving section. Then, the output of the matrix circuit 11 of the AM receiving section and
The output of the stereo demodulator 5 of the FM receiving section is switched by switches 12 and 13 and sent to output terminals 14 and 15.
It is now being supplied to Further, 16 is a stereo display device. This stereo display 16 includes a stereo demodulator 5 when receiving FM stereo broadcasting.
A pilot signal detection output is supplied from the ID tone detector 10, and an ID tone detection output is supplied from the ID tone detector 10 when receiving AM stereo broadcasting. Furthermore, Vcc from a power supply (not shown) is supplied only to the FM receiving section when receiving FM broadcasting, and only to the AM receiving section when receiving AM broadcasting.

In the FM/AM receiver configured as described above, the FM receiving section passes the output of the intermediate frequency amplifier 2 through the limiter circuit 3, performs FM detection with the FM detector 4, and further performs FM detection with the stereo demodulator 5. Since it is demodulated as a left signal, it is possible to receive FM stereo broadcasts. Further, the AM receiving section performs AM detection on the output of the intermediate frequency amplifier 7 using an AM detector 8 to demodulate a sum signal, simultaneously performs PM detection on the same output using a PM detector 9 to demodulate a difference signal, and furthermore, demodulates the sum signal. The ID tone obtained at the same time is detected by the ID tone detector 10, and the detected output is used as a control signal to demodulate the right and left signals from the sum signal and difference signal in the matrix circuit 11, so that AM stereo broadcasting can be received. . Of course, it goes without saying that the FM receiving section and the AM receiving section can also receive normal monaural broadcasts.

Now, when receiving an FM stereo broadcast, Vcc is not supplied to the AM receiving section, and only the detected output of the pilot signal from the stereo demodulator 5 is supplied to the stereo display 16. Further, when receiving an FM stereo broadcast, Vcc is not supplied to the FM receiving section, and only the ID tone detection output from the ID tone detector 10 is supplied to the stereo display 16. Therefore, the above
In the FM/AM receiver, using the pilot signal detection output and the ID tone detection output as signal sources, stereo display is performed on a single stereo display 16 both when receiving an FM stereo broadcast and when receiving an AM stereo broadcast.

FIG. 2 is a specific circuit diagram of the stereo display 16. In this figure, 17 is an NPN transistor whose base is connected to a pilot signal detection output input terminal 19 via a resistor 18. 20 is another
It is an NPN transistor whose base is connected to the ID tone detection output input terminal 22 via a resistor 21. The emitters of these transistors 17 and 20 are grounded. On the other hand, the collectors of transistors 17 and 20 are commonly connected. The collectors of the commonly connected transistors 17 and 20 and the +Vcc terminal 2
3, a light emitting diode 24 and a resistor 25 are connected in series.

In the stereo display device 16 configured in this manner, when the pilot signal detection output is supplied to the input terminal 19, the transistor 17 is turned on.
When the transistor 17 is turned on, a current flows through the transistor 17 to the light emitting diode 24, and the light emitting diode 24 emits light. On the other hand, when the ID tone detection output is supplied to the input terminal 22,
Transistor 20 turns on. transistor 20
When turned on, current flows to the light emitting diode 24 via this transistor 20, and the light emitting diode 24 emits light. Therefore, according to this stereo display device 16, by the light emission of one light emitting diode 24, a stereo display when receiving an FM stereo broadcast and a stereo display when receiving an AM stereo broadcast can be performed.

As mentioned above, in the FM/AM receiver of this invention, the stereo display when receiving FM stereo broadcasting and when receiving AM stereo broadcasting is performed on one display, so it is possible to reduce the cost and the stereo display is simple. This makes it easier to see.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of an FM/AM receiver according to this invention, and FIG. 2 is a specific circuit diagram showing a stereo display of the receiver. 1...FM front end, 2...FM intermediate frequency amplifier, 3...limiter circuit, 4...FM detector, 5...stereo demodulator, 6...AM front end, 7...AM intermediate frequency amplifier, 8...AM
Detector, 9...PM detector, 10...ID tone detector, 11...matrix circuit, 16...stereo display.

Claims (1)

[Scope of claim for utility model registration] An FM receiver capable of receiving FM stereo broadcasts,
An AM receiver that can receive AM stereo broadcasts, and an FM receiver that can receive AM stereo broadcasts.
A pilot signal detection output is supplied from the FM receiving section when receiving stereo broadcasting, and an identification tone detection output is supplied from the AM receiving section when receiving AM stereo broadcasting, and a single stereo display device is provided for stereo display. will be done
In an FM/AM receiver, the collectors of a pair of transistors whose emitters are grounded are connected in common, and a light emitting diode constituting the stereo display is connected between the commonly connected collectors and the power supply, and the base of one transistor is connected. configured to supply a pilot signal detection output from the FM receiver and an identification tone detection output from the AM receiver to the base of the other transistor,
Stereo display is now available when receiving FM stereo broadcasts and when receiving AM stereo broadcasts.
FM/AM receiver.