JPH03179825A - Adjusting method for fm receiver - Google Patents

Abstract

PURPOSE:To adjust a detector circuit and an intermediate frequency filter section to an optimum point by supplying an output signal of a front end circuit to the detector circuit through a passing circuit of an intermediate frequency filter section at the adjustment. CONSTITUTION:Switching means 5, 6 bypassing an intermediate frequency filter section 2b are provided on an FM receiver 2, a measuring high frequency signal at the adjustment of the FM receiver 2 is applied to the input side and the output signal of the FM receiver is fed to a distortion meter 3. Then a detector circuit 2d is adjusted so as to bypass the intermediate frequency filter section 2b and then the intermediate frequency filter section 2b is adjusted. Then the output signal of the front end circuit 2a is fed to the detector circuit 2d without being fed to the intermediate frequency filter section 2b at the adjustment of the detector circuit 2d. Thus, the adjustment of the center frequency of the detector circuit 2d itself and the correction of the linearity are best implemented and the intermediate frequency filter section 2b and the entire receiver are adjusted to the optimum point.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for adjusting an FM receiver.

[Conventional technology]

Generally, when manufacturing an FM receiver, when readjusting it, or when parts are replaced due to failure, etc., adjustments are made to the center frequency of the detection circuit and intermediate frequency filter section of the FM receiver, correction of linearity, etc. There is.

Conventionally, methods shown in FIGS. 3 and 4 have been used to adjust the detection circuit and intermediate frequency filter section of this FM receiver. That is, in FIG. 3, the high frequency signal R for measurement
The high-frequency signal RF for measurement from the high-frequency signal generator (1) that generates F is supplied to the input side of the front-end circuit (2a) constituting the FM receiver (2). Supplying the output signal to a distortion meter (3) via an intermediate frequency filter section (2b) consisting of an intermediate frequency filter and an intermediate frequency amplifier, a limiter circuit (2c), a detection circuit (2d) and an FM multiplexer (2e), While looking at this distortion meter (3), check the detection circuit (2d) including the characteristics of the front end (2a) and intermediate frequency filter section (2b).
The center frequency was adjusted and the linearity was corrected.

In addition, in Fig. 4, when adjusting the detection circuit (2d), the intermediate frequency signal IF from the intermediate frequency signal generator (4) that generates the intermediate frequency signal IF of 10.7 M) fz for measurement is injected. Supply it from the input end of the limiter circuit (2c) through the pin for
After adjusting the center frequency and correcting the linearity of 2d), the high frequency signal from the high frequency signal generator (1) is supplied from the input side of the front end circuit (2a) in the same way as the method shown in Figure 3, and the intermediate The frequency filter section (2b) and the entire receiver were being adjusted.

[Problem to be solved by the invention]

However, in the method shown in Fig. 3, the best point is not the best point of the detection circuit (2d) itself, but the best point including the intermediate frequency filter section (2b).
), the detection circuit (2
d) itself is not at the best point, making it difficult to make adjustments to obtain the best point for this intermediate frequency filter section (2b).

In addition, the method shown in Fig. 4 can obtain the best point of the detection circuit (2d) itself, but there are two types of signal generators for measurement: a high frequency signal generator (1) and an intermediate frequency signal generator (4). In addition, there is an inconvenience in that it requires adjustment man-hours to change the signal injection method, and furthermore, when adjusting by supplying a high-frequency signal from a high-frequency signal generator (), it is necessary to adjust the intermediate frequency signal for measurement. If the injection pin remains provided, the stray capacitance due to the injection pin increases, and the injection pin acts as an antenna, making accurate adjustment impossible.

In view of these points, the present invention is designed to enable adjustment of the best point of the detection circuit (2d) itself with a simple configuration and to reduce the number of adjustment steps.

[Means to solve the problem]

The method of adjusting the FM receiver of the present invention is as shown in FIG. 1, for example.
The FM receiver (2) is provided with switch means (5) and (6) for bypassing the intermediate frequency filter section (2b), and the high frequency signal for measurement is transmitted to the FM receiver (2) during adjustment of the FM receiver (2). At the same time, the output signal of this FM receiver is supplied to the distortion meter (3), and the detection circuit (2d) is adjusted by first bypassing this intermediate frequency filter section (2b). After that, the intermediate frequency filter section (2b) is adjusted.

[Effect]

According to the present invention, when adjusting the detection circuit (2d), the output signal of the front end circuit (2a) is supplied to the detection circuit (2d) without passing through the intermediate frequency filter section (2b). The center frequency adjustment and linearity correction of the circuit (2d) itself can be adjusted to the best point, and the intermediate frequency filter section (2b) and the entire receiver can be adjusted to the best point. Furthermore, since the high frequency signal generator (, 1) is used as the signal generator without changing the injection point, the number of adjustment steps is reduced.

〔Example〕

An embodiment of the method for adjusting an FM receiver according to the present invention will be described below with reference to FIGS. 1 and 2.

In FIGS. 1 and 2, parts corresponding to those in FIG. 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

In Fig. 1, the output side of the front end circuit (2a) of the FM receiver (2) is connected to the movable contact (
5a), one fixed contact (5b) of this changeover switch (5) is connected to the input side of the intermediate frequency filter section (2b), and the output side of this intermediate frequency filter section (2b) is connected to the changeover switch (5b). Connect to one fixed contact (6b) of 6),
In addition, the other fixed contact (5c) of the changeover switch (5) is connected to the other fixed contact (6c>) of the changeover switch (6) via the pass circuit (7), and the movable contact ( 6a> is connected to the input side of the short ivy, and the rest is configured in the same manner as a conventional FM receiver.

The specific configuration of the changeover switches (5) (6) and the pass circuit (7) is shown in FIG.
The output side of a) is connected to the gate of a field effect transistor (7a) constituting the pass circuit (7), and the gate of this field effect transistor (7a) is grounded via a resistor (7b). The source of the transistor (7a) is grounded, and the drain of this field effect transistor (7a) is connected to a power terminal B to which a positive DC voltage is supplied via a resistor (7c), and this drain is connected to an intermediate frequency filter. The output side of this intermediate frequency filter section (2b) is connected to the input side of the intermediate frequency filter section (2b).
d) and connect this base to the connection switch (7).
e) and ground this base through a resistor (7r
) and a capacitor (7g) to ground through a series circuit,
The connection point of this resistor (7f) and capacitor (7g) is connected to the power supply terminal B via the resistor (7i), and the connection point of this resistor (7f) and capacitor (7g) is connected to the resistor (7j). ) to ground through this transistor (7
Connect the collector of d) to the power supply terminal B, ground the emitter of this transistor (7d) via a resistor (7k), and connect this industrial ivy to the input terminal (2ci) of the limiter circuit (2c). , and connect the connection point of the resistor (7f) and capacitor (7g) to np via the resistor (71).
Connect to the base of an n-type transistor (7m), ground the emitter of this transistor (7m), connect the collector of this transistor (7m) to power supply terminal B via a resistor (7n), and connect this collector to Connect to the anodes of diodes (5d) and (6d) that constitute the switch, connect the cathode of this diode (5d) to the output side of the front end circuit (2a), and connect the cathode of the diode (6d) to the limiter circuit. Connect to the input terminal (2ci) of (2C).

In this Figure 2, when the connection switch (7e) is open, the voltage determined by the resistors (71) and (7j) is supplied to the base of the transistor (7m), so this transistor (7m) It becomes conductive and the diode (5d)
and (6d) are reverse biased.
d) and (6d) are both non-conductive, and the output signal of the front end circuit (2a) is transferred to the field effect transistor (7a).
), intermediate frequency filter section (2b) and transistor (7
d) to the limiter circuit (2c), and when this connection switch (7e) is closed, the voltage supplied to the base of this transistor (7m) becomes approximately ground potential, and this transistor (7m) becomes non-active. At this time, forward bias is supplied to the diodes (5d) and (6d), and the diodes (5d) and (6d) become conductive. Therefore, the output signal of this front end circuit (2a) has an intermediate frequency. The limiter circuit (2
c).

Since this example is configured as described above, when manufacturing this FM receiver, when readjusting it, when replacing parts due to failure, etc., the detection circuit (2d) of this FM receiver (2)
When adjusting the intermediate frequency filter section (2b), etc., the high frequency signal for measurement from the high frequency signal generator (1) as shown in FIG. The output signal of the multiplexer (2e) is supplied to the input side of the front end circuit (2a), and the output signal of the multiplexer (2e) is supplied to the distortion meter (3).

In this case, when adjusting the center frequency and correcting the linearity of the detection circuit (2d), move the movable contacts (5a) and (6a) of the changeover switches (5) and (6), respectively, to the other fixed contact. (5c) and (6C), and the output signal of the front end circuit (2a) is connected to the intermediate frequency filter section (2a).
b) is supplied to the detection circuit (2d) via the bus circuit (7) and limiter circuit (2C) without going through the distortion meter (
3), adjust the center frequency of this detection circuit (2d) and correct the linearity of the detection characteristics. In this case, since the signal supplied to the detection circuit (2d) does not pass through the intermediate frequency filter section (2b), it can be adjusted and corrected to the best point of the detection circuit (2d) itself.

Next, when adjusting the intermediate frequency filter section (2b), use the movable contacts (5a) of the changeover switches (5) and (6).
and (6a) to one of the fixed contacts (5b) and (6b), and while watching the distortion meter (3), insert the intermediate frequency filter section (
Perform the adjustment in 2b). In this case, the detection circuit (2d) is adjusted to the best point, so this intermediate frequency filter section (2d)
It can be adjusted to the best point of b). In addition, in this case of adjustment, since the changeover switches (5) and (6) are simply changed over, the number of adjustment steps is small and good adjustment can be made in a short time. Further, in this example, there is no need to provide a pin for injecting an intermediate frequency signal for measurement, so there is no influence of the stray capacity of this bottle.

In addition, in this example, when used as an FM receiver (2), the movable contacts (5a) of the changeover switches (5) and (6)
and (6a) to one fixed contact (5b) and (6b), respectively.
) of course.

In addition, in the example in Fig. 1, two changeover switches (5) and (6) are provided, but instead of these, changeover switches (5) or (6) are provided.
The output side of the intermediate frequency filter section (2b) is connected to the input side of the limiter circuit (2c), and the other fixed contact (5c) of the changeover switch (5) is connected to the input side of the limiter circuit (2C). or connect the output side of the front end circuit (2a) to the intermediate frequency filter section (2b).
This front end circuit (2) is connected to the input side of the
Switch the output side of a) to the other fixed contact of the switch (6) (
6c). Furthermore, instead of the changeover switch (5) or (6), the changeover switch (5) or (6) has a movable contact (5a) or (6a), one fixed contact (5b) or (6b), and the other fixed contact. A land for electrical connection is provided in the part corresponding to (5C) or (6C), and only during adjustment, connect the land corresponding to contact (5a) or (6a) and (5C) or (6C) with solder, etc. In other cases, contact (5a) or (6a) and (5b> or (
6b) may of course be connected. Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, when adjusting the detection circuit (2d), the output signal of the front end circuit (2a) is transferred to the intermediate frequency filter section (2d).
Since the power is supplied to this detection circuit (2d) through the path circuit (7) in b), it is possible to adjust the center frequency and correct the linearity of this detection circuit (2d) itself to the best point, and then to the pass circuit. When adjusting the intermediate frequency filter section (2b) with (7) inactive, use this detection circuit (2d).
is adjusted to the best point, so there is an advantage that this intermediate frequency filter section (2b) can also be adjusted to the best point. In addition, to adjust the detection circuit (2d) and intermediate frequency filter section (2b), only the high frequency signal generator (1) is required as a signal generator, simply by switching the switches (5) and (6) of the pass circuit (7). This has the advantage of requiring less adjustment man-hours and allowing adjustment to the best point in a short time.

[Brief explanation of drawings]

Fig. 1 shows the constituent countries for explaining one embodiment of the FM receiver adjustment method of the present invention, Fig. 2 shows a connection section showing a specific example of the main part of Fig. 1, and Figs. 3 and 4 respectively. These are constituent countries showing examples of adjustment of conventional FM receivers. (1) is a measurement high frequency signal generator, (2) is an FM receiver, (2a) is a front end circuit, (2b) is an intermediate frequency filter section, (2d) is a detection circuit, and (3) is a distortion meter. ,(
5) and (6) are changeover switches, and (7) is a pass circuit.

Claims (1)

[Claims] The FM receiver is provided with a switch means for bypassing the intermediate frequency filter section, and when adjusting the FM receiver, a high frequency signal for measurement is transmitted to the FM receiver.
The output signal of the FM receiver is supplied to the input side of the M receiver, and the output signal of the FM receiver is also supplied to the distortion meter, and the detection circuit is first adjusted so as to bypass the intermediate frequency filter section, and then the intermediate frequency A method for adjusting an FM receiver, characterized in that a filter section is adjusted.