JP3086502B2 - Radio receiver and tuner circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiver of an electronic tuning system, and more particularly to a radio receiver including a tuner circuit formed as an integrated circuit (IC).

[0002]

2. Description of the Related Art Electronically tuned radio receivers are known in the prior art. This radio receiver sets a frequency division ratio corresponding to a tuning frequency in a programmable divider constituting a PLL, applies a tuning control signal obtained from the PLL to a local oscillation circuit, and adjusts a local oscillation frequency. Determine and select a station.

FIG. 5 shows an example of the configuration of an electronic tuning type radio receiver. The radio receiver shown in this figure includes a tuner IC 1, a microcomputer 2, and a PLL (Phase
Locked Loop) 3 and a display unit 4 are provided. The tuner IC 1 is formed by forming a tuner circuit on a single integrated circuit substrate except for a part that cannot be made into an IC, such as an antenna and an FM front end, and receives AM and FM waves to select a channel.
The microcomputer 2 supplies a band switching signal BAND SW in response to a user instruction from a button (not shown) or the like, and switches the reception band of the tuner IC 1 between the AM band and the FM band. Further, the microcomputer 2 supplies a forced monaural signal to the tuner IC 1 in the case of AM reception or the like, and a multiplex circuit (hereinafter, referred to as a multiplex circuit) built in the tuner IC 1.
MPX) to perform monaural reception.

The tuner IC 1 has a display output terminal 5. This terminal is a terminal used for directly connecting and driving an LED or the like in a manual tuning system generally used in the past. In the electronic tuning type, the display output terminal 5 is used as an output terminal of a signal necessary for the operation of the microcomputer, and requires two display output terminals 5.
That is, a tuning display signal (hereinafter, referred to as SD) indicating that the signal has been tuned to the AM or FM wave, and a stereo display signal (hereinafter, referred to as "SD") indicating that the signal is received at a level at which stereo reproduction is possible during FM reception. , ST), two display output terminals 5 are required.

[0005] The microcomputer 2 monitors SD and ST, and controls the oscillation frequency of the PLL 3 and the display of the display unit 4 according to the results. That is, the microcomputer 2 controls the PLL 3 so as to obtain at least SD, and controls the local oscillation frequency of the tuner circuit. In addition, microcomputer 2
Turns on the display lamp 6 provided on the display unit 4 depending on whether or not ST has been obtained.

[0006] The microcomputer 2 includes, in addition to the above-described control operations, associated functions (for example, a cassette tape recorder).
It is often used for control of data.

As described above, the conventional electronically tunable tuner I
In the radio receiver using C, control of the PLL 3 and stereo display could be performed by monitoring SD and ST and performing control based on the results.

[0008]

However, in a conventional radio receiver in which an electronic tuning type tuner is integrated into an IC, two display output terminals are required, which is a problem that leads to an increase in the scale of the apparatus. . Generally, when an electronic device such as a radio receiver is designed and manufactured in the form of an IC, the number of IC terminals is significantly related to the circuit size and the price. Specifically, as the number of terminals of the IC increases by one, the wiring of the substrate connecting the IC and other members becomes complicated, and
The area of the D electrode is reduced, and the line width of the wiring is reduced. Also,
Since the number of terminals of the IC is standardized to a certain number of terminals, even if the number of necessary terminals is one, if the number does not match, it may be necessary to increase the number of terminals. Further, in the radio receiver shown in FIG. 5, in addition to such general problems, the problem of the efficiency of use of the I / O port of the microcomputer 2 and the number of interconnections between the tuner IC 1 and the microcomputer 2 increase. There is also a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to reduce the number of terminals of a tuner IC.

[0010]

In order to achieve the above object, a radio receiver according to the present invention includes a tuner circuit and a control means which are integrated into an IC. Tuner IC is SD
And ST, a means for outputting AM or FM-SD from the common terminal when a forced monaural signal is supplied and a FM signal can be reproduced in stereo when tuned to an AM or FM wave. There is provided a means for outputting ST from the common terminal when the signal is received at the level and the forced monaural signal is not supplied. Further, the control means supplies a forced monaural signal to the tuner IC, and when SD is output from the tuner IC in a state where the forced monaural signal is supplied, the SD is set to AM-SD based on the band switch setting. Discriminate whether it is FM-SD, if the discrimination result is AM-SD, make the tuner IC execute the AM receiving operation, and if the discrimination result is FM-SD, cut off the forced monaural signal; It is determined whether or not ST is output from the tuner IC in a state where the forced monaural signal is cut off, and a display is displayed on the display unit in accordance with the result of the determination to cause the tuner IC to execute the FM reception operation.

Further, the tuner circuit of the present invention has
An IC tuner circuit including an M receiving unit and an AM receiving unit, a first circuit to which ST and a forced monaural signal are applied, a second circuit to which FM and AM-SD are applied, and a load. And an output terminal of an IC to which the output terminals of the first and second circuits are connected in common to the output terminal. During an application period of a forced monaural signal, the output signal of the second circuit is connected to the output terminal. An output signal is generated at the output terminal, and an output signal of the first circuit is generated at the output terminal during a period in which the forced monaural signal is not applied.

Further, the tuner circuit according to the present invention is characterized in that a signal having a polarity opposite to that of a forced monaural signal is applied to the second circuit as a prohibition signal.

[0013]

In the radio receiver of the present invention, first, a forced monaural signal is supplied from the control means to the tuner IC. When tuning to an AM or FM wave in a state where a forced monaural signal is supplied, the tuner IC sends an AM or FM signal.
M-SD is output from the common terminal. When SD is output from the tuner IC, the control means determines in response to this whether the SD is AM-SD or FM-SD. In the former case, AM reception is performed. In the latter case, the operation shifts to an operation for further shifting to stereo reception.

In this operation, first, the forced monaural signal is cut off. If stereo reception is possible in this state, ST is output from the tuner IC via the shared terminal.
The control unit controls the display unit according to whether or not ST is output, and shifts to an FM reception operation.

As described above, in the present invention, SD and S
T is output from a single shared terminal. Whether the output from the common terminal is SD or ST is determined by whether or not a forced monaural signal is generated.
Whether it is D or FM-SD is determined by the setting of the band switch. Thus, a single terminal is shared without any trouble.

In the tuner circuit of the present invention, during the period when the forced monaural signal is applied to the first circuit, the second
The output signal of the circuit is generated at the output terminal of the IC. Also,
During the period in which the voltage is not applied, the output signal of the first circuit is I
It occurs at the C output terminal.

Further, in the present invention, a forbidden signal having a polarity opposite to that of the forced monaural signal is applied to the second circuit.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. The same components as those in the conventional example shown in FIG.

FIG. 1 shows the configuration of a radio receiver according to one embodiment of the present invention. In the radio receiver shown in this figure, the tuner IC 1
Is one display output terminal 5, and the AM-SD, FM-SD, and ST are output to the microcomputer 2 at different timings from this one display output terminal. The feature of the present invention is that the control of the PLL 3 and the control of the display unit 4 can be performed without any trouble while using the single display output terminal 5 as described above. The point is that the connection between them is simplified and the I / O port of the microcomputer 2 can be used efficiently. Hereinafter, this feature will be described with reference to FIGS.

FIG. 2 shows a tuner IC 1 of this embodiment.
Is shown in detail. However, for simplicity of illustration, the microcomputer 2 and the PLL 3 are an integrated microcomputer / PLL 7
And the display unit 4 is omitted.

In FIG. 2, the configuration for receiving the FM wave is as follows.
Antenna ANT, FM front end (hereinafter referred to as FM-F
E) 8, FM intermediate frequency circuit (hereinafter, FM-IF) 9,
MPX10. That is, the FM signal received by the antenna ANT is applied to the FM-FE 8, amplified, and then converted into an intermediate frequency signal (IF signal). The IF signal is applied to the FM-IF 9, which demodulates the signal and converts it to an audio signal. The audio signal is M
The signal is separated into an L channel and an R channel by the PX 10 and output to a circuit (not shown) at a subsequent stage.

In the circuit shown in FIG.
The configuration for receiving the M wave is the antenna ANT, the AM receiving unit 11
And MPX10. A signal received by the antenna ANT is applied to the AM receiving unit 11, converted into an audio signal, and output to a subsequent circuit via the MPX.

Switching between the FM reception operation and the AM reception operation is performed by the microcomputer / PLL7. The microcomputer / PLL 7 generates a signal (BAND SW) and controls the band switch 12 in response to a command issued by the user by operating a tuning button (not shown) or the like. Band switch 1
2 is connected to the FM-IF 9 and the AM receiving unit,
FM when BAND SW indicates FM station
If the IF 9 operates and the content indicates an AM station, A
The M receiving unit 11 operates. Therefore, the FM-IF 9 and the AM receiving unit 11 select a station indicated by the BAND SW, and supply an audio signal relating to this station to the MPX 10. Further, the FM-FE 8 and the AM receiving unit 11
From the microcomputer / PLL7 to the VCO-FM
And a control signal represented by VCO-AM, whereby the local oscillation frequency is changed and the frequency conversion operation is performed.

Further, the FM-IF 9 and the AM receiver 11
Output SD. The SD output by the former is F
It is called M-SD, and the SD output by the latter is called AM-SD. SD is a signal indicating that the signal has been tuned to the AM or FM wave. If this signal is obtained, the user can generally listen to the FM or AM broadcast satisfactorily. The MPX 10 also includes an ST generator 13 and a switch 14 connected thereto, and the microcomputer / PLL 7 controls the switch 14 with a forced monaural signal to prohibit / cancel the generation of ST.

The SD output from the FM-IF 9 or the AM receiver 11 and the ST output from the ST generator 13 are as follows:
The data is taken into the SD / ST terminal common unit 15. SD / ST
As shown in FIG. 3, the terminal sharing unit has two transistors 16 and 17, and these transistors 16 and 17 are connected in parallel to the display output terminal 5. The number of display output terminals 5 is one, and is one of the terminals of the tuner IC 1 that is an IC. The display output terminal 5 is connected to a power supply via a resistor 18 and to the microcomputer / PLL7. The display output terminal 5 is a terminal that outputs FM-ST, FM-SD, and ST at different timings. The forced monaural signal ("L") and ST are applied to AND gate 19,
The output of AND gate 19 is connected to the base of transistor 16. The FM-SD is applied to the AND gate 20 together with the inverted signal of the forced monaural signal, and the output signal of the AND gate 20 is output to the NOR gate 2 together with the AM-SD.
1 and the output signal of the NOR gate 21 is applied to the base of the transistor 17.

In FIG. 2, the tuner IC 1
Does not include FM-FE8, but this may be included.

FIG. 4 shows a microcomputer / controller in this embodiment.
The flowchart of the PLL 7 is shown.

First, the microcomputer / PLL 7 supplies the forced monaural signal to the tuner IC 1 and controls the switch 14 to set the tuner IC 1 to the forced monaural mode. In this state, the output of the AND gate 19 becomes “L”, and the ST output from the transistor 16 of the SD / ST terminal shared unit 15 is prohibited. In this state, F
When the M-IF 9 or the AM receiver 11 tunes to the station, the transistor 17 is turned on, and the FM-SD or the AM-S
D is issued, the display output terminal 5 becomes "H", and is transmitted to the microcomputer / PLL 7 as a signal indicating the tuning state (see Table 1).

[0029]

[Table 1]

The microcomputer / PLL 7 monitors the output of the display output terminal 5 (102), determines whether or not it is "H" (103), and repeats the SD detection operation until it becomes "H".

As a result of this operation, when the output polarity of the display output terminal 5 becomes "H" and a state in which it can be considered that the terminal is tuned to the station, the microcomputer / PLL 7 sets the BAND SW to FM.
Is determined (104). That is, it is determined whether the user has selected FM reception. As a result, when AM reception is selected instead of FM, the microcomputer / PLL 7
The M receiving operation is started (105). Unlike this, F
If it is determined that M reception has been selected, the microcomputer / PLL 7 turns off the forced monaural signal and sets the tuner IC 1 to the stereo mode (106).

When the forced monaural signal is turned off, as shown in Table 1, the SD / ST terminal common unit 15 is operable according to the ST output. In this case, when ST occurs, the output of the display output terminal 5 becomes "L". The microcomputer / PLL 7 determines whether the output polarity of the display output terminal 5 is "L" (107), and displays either a stereo display (108) or a stereo off display (109) according to the result. The program is executed by the unit 4. After this, the microcomputer /
The PLL 7 starts FM reception by the tuner IC 1 (110). Thus, according to the present embodiment, a plurality of signals, that is, AM-
SD, FM-SD, and ST can be output. This is because the determination regarding SD and the determination regarding ST are performed at different timings, and the transistors 16 and 17 are provided so that one display output terminal 5 can be shared. As a result, the tuner IC 1 and the microcomputer / P
The connection with LL7 will be simplified and the microcomputer /
The I / O port of the PLL 7 also requires only one pin. further,
The effect that the design of the board used for connecting the both becomes easier can be obtained. These advantages are further:
This leads to a reduction in circuit scale and a reduction in circuit cost, and a small, inexpensive, radio-friendly radio receiver such as a car stereo can be obtained.

By the way, once FM tuning is performed,
If the received signal becomes weak electric field due to multipath or the like, ST is lost and FM-SD is also lost. In such a case, if the configuration is such that FM-SD is simply applied to the NOR gate 21, the transistor 17 is turned on and an erroneous operation of generating an ST display signal occurs even though there is no ST. However, if the inverted signal of the forced monaural signal is applied to the AND gate 20 together with the FM-SD as shown in FIG.
Can be forcibly turned off, and the malfunction can be prevented.

Although the microcomputer and the PLL are shown integrally in FIG. 2, the present invention may have a configuration in which both are separate. Further, in FIG. 3, the SD / ST terminal shared unit 15 includes two transistors 16 and 17, but other types of switching elements may be used instead of the transistors. That is, any means may be used as long as SD and ST are fetched and switched in parallel and output.

[0035]

As described above, according to the present invention,
Since SD and ST can be output from a single common terminal,
The number of terminals of the tuner IC can be reduced, so that simplification of wiring, efficient use of I / O ports of control means such as a microcomputer, and reduction in circuit scale and cost can be realized.

According to the third aspect, malfunction can be prevented when the received signal becomes weak electric field due to multipath or the like and ST and FM-SD disappear.

[Brief description of the drawings]

FIG. 1 is a configuration of a radio receiver according to an embodiment of the present invention;
FIG. 2 is a block diagram particularly showing a configuration near the tuner IC.

FIG. 2 is a block diagram showing a detailed circuit configuration of the embodiment.

FIG. 3 is a circuit diagram showing a configuration of an SD / ST terminal common unit in this embodiment.

FIG. 4 is a flowchart showing the operation of the microcomputer / PLL in this embodiment.

FIG. 5 is a block diagram showing a configuration of a radio receiver according to a conventional example, particularly a configuration near a tuner IC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tuner IC 2 Microcomputer 3 PLL 4 Display part 5 Display output terminal 6 Display lamp 7 Microcomputer / PLL 15 SD / ST terminal common part 16, 17 Transistor

Claims (3)

(57) [Claims] 1. A common terminal for outputting a channel selection display signal and a stereo display signal, which is tuned to an AM or FM wave and is supplied with an AM or FM signal when a forced monaural signal is supplied.
An IC having means for outputting a tuning display signal from a common terminal and means for outputting a stereo display signal from the common terminal when FM waves are received at a stereo reproducible level and no forced monaural signal is supplied. When a forced monaural signal is supplied to the tuner circuit and a tuner IC, and a tuner display signal is output from the tuner IC in a state where the forced monaural signal is supplied, the tuning display is performed based on the band switch setting. It is determined whether the signal is an AM tuning display signal or an FM tuning display signal. If the determination result indicates that the signal is an AM tuning display signal, the tuner IC performs an AM receiving operation. If the signal is a station display signal, the forced monaural signal is cut off, and the stereo display signal is output from the tuner IC.
Control means for judging whether or not the signal is output from the microcomputer in a state in which the forced monaural signal is cut off, and causing the display unit to display according to the result of the judgment, and causing the tuner IC to execute the FM reception operation. A radio receiver, characterized in that: 2. An integrated tuner circuit including an FM receiving section and an AM receiving section, a first circuit to which a stereo display signal and a forced monaural signal are applied, and an FM and AM tuning display signal. And an output terminal of an IC to which a load is connected. The output terminals of the first and second circuits are commonly connected to the output terminal, and during the application period of the forced monaural signal, Generating an output signal of the second circuit at the output terminal, and generating an output signal of the first circuit at the output terminal during a period in which a forced monaural signal is not applied. Tuner circuit. 3. The tuner circuit according to claim 2, wherein a signal having a polarity opposite to that of the forced monaural signal is applied to said second circuit as a prohibition signal.