JPS6046567B2 - Resonant coil for UHF tuner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a resonant coil used in a tuning circuit of a UHF tuner.

Recently, tuners in television receivers have shifted from mechanical tuners to electronic tuners that use varactor diodes, etc., and along with this, the manufacturing method has also changed from three-dimensional wiring to flat wiring using printed circuit boards. came.

In addition, assembly automation can reduce work man-hours, such as automatically inserting circuit elements, automatically placing circuit elements on the conductor side of the board using chip elements, or forming capacitors and resistors using thick film printing technology. efforts are being made to significantly reduce this. However, the elements whose assembly can be automated are resistors,
Most circuit elements, such as capacitors, diodes, and transistors, have standardized shapes, and inductance elements, which vary in shape depending on the circuit, are difficult to assemble automatically, and are often attached to printed circuit boards by hand. This is the actual situation. Therefore, in order to reduce the number of man-hours required for manufacturing the saw layer, it is necessary to reduce the number of circuit elements such as inductance elements that must be assembled manually. Including these problems, the UI that is the subject of the present invention
(Conventional problems with F tuners will be explained in detail using Figures 1 and 2. Figure 1 is a circuit diagram of the tuning circuit section used in the conventional UlIF' tuner, and Figure 2 is its assembly diagram. 1 and 2, circuit elements showing the same content are given the same reference numerals. In both cases, the DC circuit is omitted. 1 is the resonant coil, and 2 is the variation in inductance of the resonant coil 1. 3 is a varactor diode for changing the resonance frequency, 4 is a capacitor for tracking correction,
Reference numeral 5 denotes an adjustment trimmer capacitor composed of a varactor diode 3 and a capacitor 4 for absorbing variations in tuning capacitance, and these circuit elements constitute a 1/4 input type resonant circuit 6.

Also, 7 and 9 are signal input/output terminals, and in an actual tuner, a signal source such as an antenna is connected to terminal 7.
A load such as an amplifier element such as a transistor or a mixer element is connected to the terminal 9. 8 is an input coupling coil for transmitting the signal input from the terminal 7 to the resonant circuit 6 by inductive coupling with the resonant coil 1; 10 is also for extracting the signal from the resonant circuit 6 and outputting it to the terminal 9; This is an output coupling coil.

In this way, the tuning circuit is usually assembled in the form shown in FIG. 11 is the printed circuit board, 12 is the copper foil of the board (
Pattern run, de), 13 is a palm. The diode 3 and capacitor 4 in FIG. 1 are mounted on the back side of the substrate 11 on the copper foil 12 side. The diode 3 usually has a standardized shape, and if a chip type capacitor 4 is used, the shape can also be standardized, allowing surface mounting. Naturally, standardized elements can be installed automatically. Although not shown in Figure 1, chip-type bias resistors and bypass capacitors are used, and flat-package types are used for transistors, etc., and these are also automatically mounted on the back side of the board. Ru. However, it is difficult to standardize inductance elements such as the resonant coil 1, adjustment coil 2, input coupling coil 8, and output coupling coil 10 because the constants differ for each tuned circuit. Automatic assembly is difficult due to its U-shaped three-dimensional structure.Automatic assembly of the trimmer capacitor 5 is also difficult for the same reason.Therefore, as shown in Fig. 2, the printed circuit board An assembly method is used in which the substrate is manually inserted into board holes 11a, 11b, etc. from the front side of 11, and soldered to pattern lands on the back side.

In the case of the tuning circuit of the U8 tuner, a distributed constant line is used for the resonant inductance, so inductive coupling is suitable for coupling the circuit, and therefore there are many inductance elements, making automatic assembly difficult. One tuning circuit has as many as five elements, including the trimmer capacitor, that are difficult to assemble automatically, and the entire UIIF tuner has only 1/1/2 of the total number of circuit elements.
3, and reducing the number of these parts is UH
Reducing man-hours in F tuners has become an important issue.
Another drawback is that inductance adjustment or coupling adjustment is often inconvenient. For example, the inductance of the resonant coil 1 is adjusted by changing the distance between it and the adjustment resonant coil 2, and the degree of input/output coupling is adjusted by changing the distance between the resonant coil 1 and the coupled resonant coils 8 and 10. However, the arrangement of the coils affects each other, making adjustment difficult. To explain using the example shown in FIG. 2, since the output coupling coil 10 is located between the resonance coil 1 and the adjustment coil 2, the output coupling coil 10 becomes an obstacle, making it difficult to bring the adjustment coil 2 sufficiently close to the resonance coil 1. Therefore, there arises a drawback that the variable range of inductance adjustment of the resonant coil 1 cannot be made sufficiently large. On the other hand, if the positions of the coils 10 and 2 are exchanged, problems arise such as insufficient coupling adjustment between the resonant coil 1 and the coupling coil 10. As explained above, the conventional [
In the tuning circuit of a JHF tuner, there are many circuit elements that must be assembled manually, making it difficult to automate the assembly.Furthermore, due to the arrangement of the circuit elements, inductance adjustment or coupling adjustment is difficult, which increases the amount of adjustment man-hours. It had drawbacks such as being large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a resonant coil for a UHF tuner that alleviates the above-mentioned drawbacks of the prior art, allows easy assembly automation, and is easy to adjust.

In the present invention, the resonant coil is constituted by a pair of coils connected in parallel, and no adjustment coil is used.

This pair of resonant coils is integrally formed of a metal plate with electrodes for the trimmer capacitor and the like. Further, the inductance is adjusted by tilting at least one of the pair of resonant coils to change the degree of coupling between the two. Next, a detailed explanation of the present invention will be given using specific examples.

One embodiment of the present invention will be explained using FIGS. 3, 4, and 5. FIG. 3 is a circuit diagram of a tuning circuit of a UHF tuner to which the present invention is applied, FIG. 4 is a structure of a resonant coil according to the present invention, and FIG. 5 is a perspective view for explaining its assembly structure. The difference in FIG. 3 from the conventional tuning circuit shown in FIG. 1 is the structure of the resonant coil and the method of connecting the tuning coil. That is, in place of the conventional resonant coil 1, in the present invention, a resonant coil is constituted by two U-shaped resonant coils 14 and 15 whose both ends are integrally connected, and the conventional adjustment coil 2 is omitted.

Adjustment of the resonant inductance at this time is done by resonating coil 1.
This can be achieved by keeping the elements 4 and 15 inductively coupled to each other and changing the coupling coefficient M. Specifically, the inductance can be adjusted by changing the distance between the two resonant coils 14 and 15. By adopting such a circuit configuration, it becomes possible to integrally mold the resonant coils 14 and 15, and further the trimmer capacitor 5 as shown in FIG. 4. A slit 16 separates the resonant coils 14 and 15. 5b is an electrode to have the same effect as a trimmer capacitor, which is connected to the end of the resonant coil 15 by a rod-shaped connecting part 5a, and assembled as shown in FIG. By adjusting the capacitance value, the capacitance value can be changed.

Reference numeral 17 denotes a plate-shaped connection electrode to be inserted into a printed circuit board, and a melon 17a is formed so as to be stably fixed to the circuit board.

With the structure shown in FIG. 4, a metal plate such as a copper plate can be formed into a saw body by punching. Therefore, in the conventional circuit shown in FIG. 2, there were five manually inserted parts, but in the present invention, the number is reduced to three because the resonant coils 14, 15 and trimmer capacitor 5 can be treated as one part. The resonance inductance is adjusted by tilting the resonance coil 15. When the resonant coil 15 is tilted, the degree of coupling with the resonant coil 14 changes, allowing adjustment.

At this time, it is possible to avoid the problem that the output coupling coil 10 or the input coupling coil 8 becomes an obstacle as in the conventional example. This is because, as shown in FIG. 5, if the input/output coils 8 and 10 are formed to have the same size as the resonant coil 14, even if the resonant coil 15 is tilted, the coupling coil 8 or 10 Contact with can be avoided. In addition, since the resonant coils 14 and 15 of the present invention are suitable for manufacturing by punching a metal plate, they have high dimensional accuracy, and as shown in FIG. Since it is possible to create a resonant inductance, it also has advantages such as small variations in resonant inductance and improved accuracy.

Next, the inductance adjustment method employed in the present invention will be explained in detail in order to clarify its practicality and optimal design. In the tuned circuit shown in FIG. 3, if the inductance values of the resonant coil 14 and the resonant coil 15 are Ll and L2, respectively, and the degree of coupling between the resonant coils 14 and 15 is M, then the parallel circuit of the resonant coils 14 and 15 The equivalent circuit of can be expressed as shown in FIG. Therefore, from FIG. 6, the total resonant inductance value Lt of the parallel circuit of the resonant coils 14 and 15 is expressed by equation (1). However, k is the degree of connectivity, α
is the square root of the ratio of L and L2 and is as follows.

Now assuming that b≧L1, from equation (1), the maximum value LtM and minimum value Ltm of Lt
If you ask for it, you will get it.

Therefore, the rate of change β of Lt can be expressed as in equation (5).

According to equation (5), β is maximum when α=1.
That is, at the time of resetting, the change in Lt becomes the largest and the inductance adjustment range becomes the largest. At this time, the inductance Lt becomes as follows from equation (1).

From equation (6), the relationship of the degree of coupling k (5Lt) is shown in Figure 7 by the broken line A.
Indicated by

The greater the degree of coupling k, the greater the inductance value.
The maximum value is 1, and the minimum value is MU. Therefore, theoretically, the variable range of inductance can be doubled and halved.
However, this is an ideal case, and the solid line B is the result of actually measuring the inductance change. The inductance value is almost the same for Ll and L2, about 20r1H, to construct a resonant circuit, and by changing the degree of coupling (interval) between L and L, the equivalent inductance value was determined from the change in the resonance frequency. It is something. In the case of actual measurement, the degree of coupling k
The maximum value of is 0. Although it was difficult to obtain a degree of coupling of 1, it was confirmed that a sufficient variation range suitable for practical use could be obtained. The reason why the degree of coupling k deviates from the theoretical value in the vicinity of 0 to 0.1 is considered to be as follows. In Fig. 5, the resonant coil 15 weakens the coupling.
This is a case in which it is placed sideways and away from the resonant coil 14. At that time, the resonant coil 15 gradually approaches the chassis 13 as it is laid down. Therefore, the characteristic impedance of the resonant coil 15 decreases, and the equivalent inductance decreases. In theory, it is assumed that the inductance of both coils 14 and 15 does not change, but in reality, the inductance changes depending on the distance to the ground such as a chassis, so the change in inductance becomes larger than the theoretical value. Therefore, by utilizing such a phenomenon, it is also possible to increase the rate of change in inductance. As explained above based on theory and actual measurements, the adjustment method adopted in the present invention can obtain a sufficient variation range for practical use, and in order to increase the variation range, it is necessary to make the inductance values of the two coils almost the same. was confirmed to be good.

Also, of course, it is not necessary to make the inductance values of the two coils the same, but as long as the necessary variable range can be secured, L1! There is nothing wrong with setting the values to different values.

In addition, in this embodiment, as shown in FIG. 4, the slit 16 is inserted over almost the entire resonant coil, but it is not necessarily necessary to insert the slit over the entire resonant coil 14'' as shown in FIG.
A common leg portion 18 of 15″ is provided, and the slit 16 has a common leg portion 18 of 15″.
It is also possible to have a structure that is not provided in the.

That is, the essential structure of the resonant coil of the present invention is that the legs 18 and 20 and the connecting part 2 that connects the legs 18 and 20.
1 into a belt-like U-shape, and a continuous slit 16'' is provided in either one of the leg portions 18, 20 and the communication portion 21.
Furthermore, connection electrodes 17 are provided at the ends of the legs 18 and 20 to lock the resonance coil to the substrate 11.
is provided.

Further, in the embodiment, the trimmer capacitor is also integrally molded, but there is no harm in treating it as a separate piece. Next, other embodiments will be described.

In FIG. 9, the slit 16 of the previous embodiment is slightly modified so that the resonant coil 14 will not be deformed when the resonant coil 15 is adjusted.

That is, by providing another slit 19 at the end of the slit 16, a part of the resonant coil 15 for adjustment is made thinner, so that when the resonant coil 15 is moved during adjustment, the stress is not easily transmitted to the resonant coil 14. By doing so, the resonant coil 15 can be moved with a relatively weak force, and the resonant coil 15 is bent at the slit 19, resulting in less deformation of the other parts of the resonant coil and the resonant coil 14, making it stable. The assembled state is maintained. Although the present invention has been described above using an embodiment of a 1/4-input type resonant circuit, it is obvious that it can also be applied to a 1/2-input type resonant circuit. It can be applied to any resonant circuits such as double-tuned circuits and local oscillation circuits, and has a wide range of applications.

In addition, although we have mainly described the effects of reducing the number of parts and facilitating adjustment, there are other advantages as well, such as the following. (
1) Since the resonant coil is configured by connecting two resonant coils in parallel, the loss (high frequency resistance) of the resonant coil is also smaller than when configured with one resonant coil, improving the Q of the resonant inductor.

(2) If the resonant coil is manufactured by punching, the dimensional accuracy will be improved, and the state in which the wires are wired on the board will be stable, so the accuracy of the inductance value will be improved.

(3) The reduction in the number of parts reduces the number of lands in the reprinted pattern, which increases the degree of freedom in pattern design and makes it less susceptible to the effects of stray capacitance and pattern inductors in the printed pattern, making optimal design easier.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a tuning circuit of a conventional UHF tuner, and FIG. 2 is an assembly diagram thereof. FIG. 3 is a circuit diagram showing an embodiment of a tuning circuit according to the present invention, FIG. 4 is a front view showing the structure of a resonant coil according to the present invention, and FIG. 5 is a perspective view showing an assembled view thereof. FIG. 6 shows an equivalent circuit of the inductance of the resonant coil according to the present invention.
FIG. 7 is a characteristic diagram showing the change in inductance using theoretical values and actually measured values. FIG. 8 is a front view showing the structure of another embodiment of the resonant coil according to the present invention, and FIG. 9 is an enlarged view showing an improvement of the electrode portion of the resonant coil according to the present invention.
5a... Connection part, 5b... Trimmer capacitor electrode, 14, 14'', 15, 15''... Resonance coil, 1
6,16″...Slit, 17...Connection electrode, 18
, 20... Leg portion, 21... Communication portion.

Claims (1)

[Scope of Claims] 1. The first and second leg parts are formed into a belt-like U-shape by first and second leg parts formed in a plate shape, and a plate-like communication part that connects the first and second leg parts, and a UHF in which a continuous slit is provided in at least one of the second leg parts and the communication part.
Resonant coil for tuner. 2 The belt-shaped U is formed by the first and second leg parts formed in a plate shape and the plate-shaped connecting part that connects the ends of the first and second leg parts.
A slit is formed in the shape of a letter, and a continuous slit is provided in the communication portion with at least one of the first and second legs, and a plate-shaped connection electrode is provided at the other end of the first and second legs. Resonant coil for UHF tuner equipped with. 3. The resonant coil for a UHF tuner according to claim 2, wherein the slit has an end portion bent outward in an L-shape. 4. The resonant coil for a UHF tuner according to claim 2, wherein the first and second leg portions, the communication portion, and the connection electrode are integrally formed of a metal plate. 5 A belt-shaped U is formed by the first and second leg parts formed in a plate shape and the plate-shaped connecting part connecting the ends of the first and second leg parts.
a resonant coil formed in a letter shape and provided with a continuous slit in a communication portion with at least one of the first and second legs; and at the other end of the first and second legs of the resonant coil. A plate-shaped connection electrode provided, and the first and second
UH having a plate-shaped electrode for a trimmer capacitor connected to one of the legs by a rod-shaped connection part.
Resonance coil for F tuner. 6. The resonant coil for a UHF tuner according to claim 5, wherein the slit has an end portion bent outward in an L-shape. 7. The resonant coil for a UHF tuner according to claim 5, wherein the resonant coil, the connection electrode, and the plate-shaped electrode for the trimmer capacitor are integrally formed of a metal plate.