JPH0611651Y2 - Radio receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Use The present invention relates to an AM and FM radio receiver having an automatic sweep function.

(B) Conventional technology Conventionally, in a radio receiver, for example, in Japanese Utility Model No. 62-
As shown in Japanese Patent No. 30351, an IF for AM and FM
(Intermediate frequency) An integrated circuit or the like is used.
This is because the integration has advantages in terms of design, man-hours, and cost. In view of such merits, recently, the IF output buffer circuit for comparing the output level of the IF output buffer circuit, the signal meter circuit, and the reference level of the signal meter circuit for obtaining a stop signal for further stopping the automatic sweep and the IF output buffer circuit are Attempts have been made to integrate comparators that control and define stop sensitivity.

By the way, in order to reduce the number of circuits and the number of terminals in this integration as much as possible, the IF output buffer circuit, the signal meter circuit, and the comparator are commonly used for AM and FM. The reference voltage terminal of this comparator is A
It was decided to connect a reference circuit common to M and FM.

(C) Problems to be solved by the invention Therefore, depending on the region, there is a preferable stop sensitivity of automatic sweep for AM and FM, respectively.
It was not possible to determine the stop sensitivity unique to M and FM.

(D) Means for Solving the Problems The radio receiver of the present invention has an A
Switching means is provided for connecting the respective reference circuits for M and FM and for switching and selecting one of the reference circuits according to the selecting means.

(E) Action The present invention is configured as described above, and AM, FM
The reference circuits for AM and FM are switched and selected in accordance with the selection.

(F) Embodiment An embodiment of the present invention will be described with reference to the drawings. (1) is an antenna, (2) is an FM antenna tuning circuit that inputs the signal of the antenna, (3) is an RF (high frequency) circuit for FM that amplifies the signal from the tuning circuit at high frequency, (4), (5 ) Is the antenna
An RF circuit for AM that amplifies the signal from (1) at a high frequency. (6) is an integrated circuit in which the following circuits are integrated. It

(7) is a mixing circuit for FM, which mixes the pin and the input signal from the pin.

(8) is an IF (intermediate frequency) circuit for FM, which is the mixed circuit
The IF signal from (7) is amplified and FM detected. (9)
Is an FM noise scan cellar circuit, the IF circuit (8)
Input the detection signal from. (10) is an MPX circuit, which separates the signal from the noise canceller circuit (9) into R and L signals and outputs them from a pin. (11) is a mixed circuit, I
An AM circuit having an F circuit supplies a detection signal to the noise canceller circuit (9). Note that this noise canceller circuit (9) becomes inoperative during AM, and the AM circuit (11)
The detection signal of is given to the MPX circuit (10) as it is,
Then, it is output from the pin. This is because the FM output terminal and the AM output terminal are commonly used. (12) is an IF output buffer circuit for inputting the IF signals of the FM IF circuit (8) and AM circuit (11), and (13) is a signal meter circuit, which is used for the FM IF circuit (8) and AM. The IF signal of the circuit (11) is rectified to detect the DC component. (14) is a comparator, which compares the output voltage of the signal meter circuit (13) with the pin voltage, and if the output voltage of the signal meter circuit (13) is higher than the pin voltage, the IF output buffer circuit (12)
Is operated to output the AM and FM IF signals from the pin.

Reference numeral (15) is a local oscillation circuit composed of a PLL, which outputs oscillation signals corresponding to FM and AM to the pins of the integrated circuit (6). Reference numeral (16) is an FM reference circuit including resistors (17) and (18) connected in series, and (19) is an AM reference circuit including resistors (20) and (21) connected in series. These FM, AM
The reference circuits (16) and (19) for use are respectively connected to the pins of the integrated circuit (6). (22), (23) are the reference circuits
(16), (19) resistance (18), sensitivity switching transistor connected in parallel to (21), (24), (25) is the respective reference circuit (16),
A band switching transistor connected in series to (19). (26) is a sensitivity switching key, and (27) is a band switching key. (28) is a control circuit composed of a microcomputer,
The frequency division ratio of the local oscillator circuit (15) is controlled to perform automatic sweeping, and the IF signal from the pin of the integrated circuit (6) is counted, and a predetermined frequency (for example, FM is 10.7 MH).
z and AM count 450 KHz), the automatic sweep is stopped. In addition, this control circuit (28)
When AM is selected by (27), the transistor (25) is turned on and the transistor (24) is turned off to select the AM reference circuit (19). When FM is selected, the transistor (2) is selected.
5) is turned off and the transistor (24) is turned on to select the reference circuit (16) for FM. Then, the transistors (22), (23) are turned on or off based on the sensitivity switching key (26), and the stop sensitivity is switched in the automatic sweep at the time of AM and FM.

Thus, in selecting AM or FM, the reference circuits (16) and (19) for AM and FM are switched and selected, and the resistors (17) and (18) of these reference circuits (16) and (19) are selected. ), (20) and (21) can be adjusted to obtain the automatic sweep stop sensitivity unique to AM and FM. Further, the sensitivity is switched by switching the resistances of the reference circuits (16) and (19) without providing an attenuation circuit in the RF circuit, so that noise generation can be prevented.

(G) Effect of the invention Since the invention is configured as described above, AM,
The AM and FM reference circuits are switched and selected according to the selection of FM, and the stop sensitivity of automatic sweep unique to AM and FM can be determined, and the preferable stop sensitivity for AM and FM in each region is obtained. be able to.

[Brief description of drawings]

The drawing is a block diagram of the radio receiver of the present invention. (6) …… Integrated circuit, (16), (19) …… Reference circuit, (24), (2
5) ... transistor, (27) ... band select key, (28) ...
... control circuit.

Claims (1)

[Scope of utility model registration request] 1. An integrated circuit having at least a circuit for outputting a predetermined signal by comparing a level of a level meter signal of AM and FM with a reference level of a reference voltage terminal common to AM and FM, and a PLL. A control circuit for controlling the configured local oscillation circuit to perform automatic sweep and stopping the automatic sweep based on a predetermined signal from the integrated circuit;
And a selection means for selecting the FM, a switching circuit for connecting one of the reference circuits for AM and FM to the reference voltage terminal and for switching and selecting one of the reference circuits according to the selection means. A radio receiver comprising means.