JPH1127074A - High frequency filter circuit and rf module using the filter circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency filter circuit most suitable to an input filter circuit to surely secure its connection with high reliability or to satisfactorily eliminate the connection by using the high frequency filter circuit of the fixed input frequency provided on a printed circuit board to prescribe the pattern width, the least inter-line distance, the inter-adjacent coil distance or a grounded conductive pattern prepared between the coils of the printed circuit board. SOLUTION: A high frequency filter circuit of the fixed input frequency is provided on a printed circuit board 11. The dielectric constant of the board 11 is set higher than 2 and lower than 5 and uses a pattern coil 12 having its pattern width w1 larger than 0.2 mm and smaller than 1.2 mm and its inter- line distance d1 larger than 0.2 mm and smaller than 0.4 mm respectively. Thus, the variance of etching accuracy of the coil 12 can be absorbed during its production as long as the width w1 is kept larger than 0.2 mm and smaller than 1.2 mm. Then the floating capacitance of the coil 12 can be sufficiently reduced together with the dielectric constant of the board 11 as long as the distance d1 is kept larger than 0.2 mm and smaller than 0.4 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency filter circuit, and more particularly to a circuit using a pattern coil formed on a printed circuit board. Further, the present invention relates to an RF module using such a high-frequency filter circuit, and particularly to an RF module used for a cordless phone or the like.

[0002]

2. Description of the Related Art In a cordless phone or the like, a high frequency filter circuit is generally provided in an input circuit portion of an RF module. The feature of the input of such an RF module is that the input frequency is fixed, and the frequency is about 250 to 380 M for Japan and 9 for Europe.
This is a relatively high frequency of about 00M. An example of a conventionally used filter is shown below. The filter circuit is formed on a dielectric substrate such as Teflon or glass epoxy, and a strip line connects each electronic element. A ground electrode having a through hole is formed, and two chip capacitors and an insertion coil are disposed at an intermediate portion between the ground electrode and the two chip capacitors by a strip line.

[0003] Such a filter is called a high-pass filter, and the cutoff frequency fc is proportional to the reciprocal of the square root of the product of the capacitance C1 of the capacitor and the inductance L1 of the inductor. However, in the final manufacturing process, these assemblies are not always performed accurately, so that the adjustment must be performed. The open / close state of the air-core coil is adjusted by using a rod or the like for the air-core coil, and the characteristics of the chip capacitor vary. The filter is adjusted to the characteristics suitable for the high-frequency device while taking into account the above factors.

[0004] Here, a printed wiring board on which such an electronic circuit is formed will be briefly described. The basis for constructing the electronic circuit is to fix the components and at the same time, to mutually connect the components. These are substrates for making connections, and according to those defined in JIS and the like,
In order to connect the components based on the circuit design, a conductor pattern is formed by printing a wiring on the surface of the insulating substrate or on the surface and inside the insulating substrate. Conventionally, a conductor is formed on the surface of a printed wiring board made of glass epoxy or the like by printing or vapor deposition, and the conductor is appropriately patterned to form a desired wiring. Then, after a desired wiring is formed, a surface-mounted component or an insertion component is appropriately arranged to form an electronic circuit that finally functions.

On the other hand, in recent years, a conductor pattern, for example, a capacitor, a strip line, a printed resistor, or the like has been formed directly on a printed circuit board by applying this printed circuit board manufacturing technique. In particular, in recent years, a print coil may be directly formed on a printed wiring board using the same steps as those described above. On the other hand, regarding the RF module, the filter provided at the input part of the RF module is connected to the double tuning circuit and the mixing circuit via the double tuning circuit and the transistor in the conventional product, and then to the IF processing circuit. A signal has been introduced. This is as shown in FIG. 7, and is specifically configured with a circuit diagram as shown in FIG.

[0006]

In a conventional high-frequency filter circuit, the coil must be adjusted during the manufacturing process, which requires many man-hours and is not appropriate. Also, the components must be provided with a coil or the like separately from the printed circuit board, which increases the number of components and causes an increase in cost. In some cases, coupling is required in the high-frequency filter circuit portion of the input circuit. If such coupling is required, the coil must be designed to optimize the arrangement of the coils. There were cases where the arrangement direction was restricted.

[0007]

According to the present invention, there is provided a high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, wherein the printed circuit board has a dielectric constant of 2 or more and 5 or more. Less than, line width 0.2mm
Provided is a high-frequency filter circuit using a pattern coil having a length of not less than 1.2 mm and a line gap of not less than 0.2 mm and not more than 0.4 mm. Further, it is a high frequency filter circuit having a fixed input frequency formed on a printed circuit board, wherein the printed circuit board has a dielectric constant of 4.3 or more and 4.9 or less and a line width of 0.2 mm or more and 1.2 mm or less. A pattern coil having a line gap of 0.2 mm or more and 0.4 mm or less is arranged adjacently, and a minimum line gap between adjacently arranged coils connected in series with a capacitor is 0.1 mm or more and 0.3 mm or less. A high frequency filter circuit is provided.

A high frequency filter circuit having a fixed input frequency formed on the printed circuit board, wherein the printed circuit board has a dielectric constant of 4.3 or more and 4.9 or less,
A pattern coil having a line width of 0.2 mm or more and 1.2 mm or less and a line gap of 0.2 mm or more and 0.4 mm or less is arranged adjacently,
Provided is a high-frequency filter circuit in which a minimum distance between coils is 0.3 mm or more and 1.6 mm or less, and a grounded conductive pattern is arranged between both coils. A high-frequency filter circuit having a fixed input frequency of 240 MHz to 390 MHz formed on a printed circuit board, wherein the printed circuit board has a dielectric constant of 4.3 to 4.9 and a line width of 0.2 mm. More than 1.2mm or less, 0.2m between lines
A pattern coil of m or more and 0.4 mm or less is arranged adjacently, and a minimum distance between the coils is 0.3 mm or more and 1.6 mm or less.
The following provides a high-frequency filter circuit in which a grounded conductive pattern is arranged between both coils.

[0009] Further, the 2
A high frequency filter circuit having a fixed input frequency of 40 MHz or more and 390 MHz or less, wherein the printed circuit board has a dielectric constant of 4.5 or more and 4.8 or less, a line width of 0.2 mm or more and 1.2 mm or less, and a line gap of 0.1 mm or less. A high-frequency wave in which a pattern coil of 2 mm or more and 0.4 mm or less is arranged adjacently, a minimum distance between the coils is 0.3 mm or more and 1.6 mm or less, and a grounded conductive pattern is arranged between both coils. Provide a filter circuit. An RF module for a cordless phone using a high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, having a line width of 0.2 m
m to 1.2 mm, line spacing 0.2 mm to 0.4 mm
An RF module using the following pattern coil is provided.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. The invention according to claim 1 is a high-frequency filter circuit having a fixed input frequency formed on a printed circuit board as described above, wherein the printed circuit board has a dielectric constant of 2 to 5 and a line width of 0.2 mm. This is a high-frequency filter circuit using a pattern coil having a length of not less than 1.2 mm and a line gap of not less than 0.2 mm and not more than 0.4 mm. When such a high-frequency filter circuit is used, the adjustment of the coil, which was conventionally required, is not required, and the variation in the filter characteristics is within a certain range due to the variation in the etching accuracy in the printed circuit manufacturing process. Therefore, a highly reliable high frequency filter circuit can be realized. Here, the permittivity, the line width, and the line interval are specified because a high-frequency filter circuit with high reliability can be realized in such a range.

Here, the permittivity is a condition for stray capacitance to be within a desired range depending on a line width and a line interval to be specified later, and these are actually used for a glass epoxy printed circuit board or the like. It can be realized by using. Next, the purpose of defining the line width and the line interval of the coil is that the characteristics of the high-frequency filter circuit can be kept within a certain range even by the variation tolerance during the manufacturing process of the printed circuit board. With respect to this, the effects of the present invention were confirmed by conducting experiments as shown in Table 1.
Specifically, the inductance was measured on a prototype board in which the pattern width of the spiral pattern of the high-frequency coil was intentionally changed, and the inductance was determined by polynomial approximation based on the measurement result.

[Table 1]

The variation of the pattern width is minus 0.2 mm.
In the range of 変 動 0.2 mm, the distance is changed in steps of 0.1 mm, and the amount of change in the central inductance is 0.07H.
Was substituted into δW for the polynomial approximation, and the variation in inductance was determined. As a result, the variation δL of the inductance is ± 0.32 nH, and ± 2.7% in 100 fraction display.
As a result, sufficient characteristics as a high frequency filter circuit of a high frequency circuit used for an RF module or the like can be secured. FIG. 9 shows this in a graph. Pattern width is minus 0.2mm ~
As the value is changed in the range of 0.2 mm, the amount of change in the inductance is reduced almost in proportion from 1.8 nH to about −2.0 H.

Such a coil is as shown in FIG. 1. Specifically, the coil can have a margin within the range described in claim 1. When the permittivity of the printed circuit board 11 is 2 or less or 5 or more, it was impossible to design a high-frequency filter circuit having desired characteristics within the specifications of the pattern coil 12. Further, the line width w1 is set to a line width of 0.2 mm or more and 1.2
The reason for setting the pattern coil 12 to be equal to or less than mm is that if the thickness is within this range, variations in etching accuracy during the manufacturing process can be absorbed. Further, the line spacing d1 is set to 0.2 mm or more and 0.4 mm or less because the printed circuit board 1 described above is used.
This is because the stray capacitance could be sufficiently reduced in this range in combination with the dielectric constant of 1.

Next, the second aspect of the present invention will be described. The invention according to claim 2 is a high frequency filter circuit having a fixed input frequency formed on a printed circuit board as described above, wherein the printed circuit board has a dielectric constant of 4.3 or more and 4.9 or less. As shown in FIG.
A pattern coil 22 having a line length d2 of not less than 2 mm and not more than 1.2 mm and a line distance d2 of not less than 0.2 mm and not more than 0.4 mm is arranged adjacent to each other. But 0.3 mm or more and 1.6 m
m is provided. The present invention relates to a case where a similar pattern coil 22 is arranged particularly adjacent to the pattern coils described in claim 1, and a high-frequency filter circuit for electromagnetic coupling between the two coils 22, 22 is provided. The invention relates to the invention of

Here, it is appropriate that the dielectric constant is 4.3 or more and 4.9 or less. In particular, the same pattern coil as that of the first aspect of the present invention, which is arranged adjacently, has the highest value. The minimum minimum line gap dm2 is 0.3 mm or more.
It is specified to be 6 mm or less. Here, the reason why the length is defined to be 0.3 mm or more and 1.6 mm or less is that optimum coupling is performed in this range.
If it is smaller than 0.1 mm, it is not possible to form a sufficiently stable high-reliability high-frequency filter circuit due to the tolerance of etching accuracy when forming a pattern coil on a printed circuit board. Also minimum line distance dm
This is because when 2 is large, it is not possible to secure sufficient coupling. For example, such a high-frequency filter circuit is as shown in FIG. 2, in which both coils 22, 22 are connected in series by a capacitor 23 for coupling.

Next, the third aspect of the present invention will be described. The invention according to claim 3 is a high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, wherein the printed circuit board has a dielectric constant of 4.3 or more and 4.9 or less and a line width of 0.2 mm. Not less than 1.2 mm, line spacing 0.2
A pattern coil of not less than 0.4 mm and not more than 0.4 mm is arranged adjacently, and a minimum distance between the coils is not less than 0.3 mm and not more than 1.6 m.
m, and a high-frequency filter circuit in which a conductive pattern grounded between both coils is provided. This is specifically applied to a circuit as shown in FIG. 10, and is a pattern wiring of a coil when coupling between adjacent coils is not required.

Specifically, the pattern is formed as shown in FIG. 3. The feature of the present invention is that the minimum distance dm3 between the coils 32, 32 is not less than 0.3 mm and not more than 1.6 mm. In that a conductive pattern 34 that is grounded is disposed. As can be seen from FIG. 10, such a coil has a form in which adjacent coils are equivalently grounded. However, if a certain amount of stray capacitance occurs between both coils, the coils are not necessarily completely grounded. The two coils are connected, which is not appropriate. Therefore, in the case of such a high-frequency circuit, a so-called solid conductive pattern 34 is disposed on both sides, and the conductive pattern 34 is completely grounded to prevent the two coils 32, 32 from being coupled.

Therefore, the stray capacitance shown by the dotted line in FIG. 10 can be sufficiently eliminated. In addition,
Here, the minimum distance dm3 between the coils 32, 32 is 0.3 m
When the distance is set to 0.3 mm or less, the coupling cannot be sufficiently eliminated even if the grounded conductive pattern 34 is provided, and the distance between the coil wires of 1.6 mm or more is required. When d3 is present, it is excellent from the viewpoint of eliminating the coupling between the two coils 32, 32, but it is an unnecessary distance, and the coil 32 arranged in this way requires a printed circuit board 31. Area becomes too large,
This is because the result is contrary to the miniaturization of the device as a whole.

The fourth aspect of the present invention will be described. According to a fourth aspect of the present invention, there is provided a high-frequency filter circuit having a fixed input frequency of 240 MHz to 390 MHz formed on a printed circuit board as described above, wherein the printed circuit board has a dielectric constant of 4.3 to 4.9. And pattern coils having a line width of 0.2 mm or more and 1.2 mm or less and a line gap of 0.2 mm or more and 0.4 mm or less are arranged adjacently, and the minimum line gap between the coils is 0.3 mm or more and 1.6 mm. The following is a high-frequency filter circuit in which a grounded conductive pattern is arranged between both coils.

The difference from the third aspect of the present invention is that the input frequency is limited to the range from 240 MHz to 390 MHz. This frequency is the optimum frequency band for RF modules such as cordless phones currently used in Japan, and the present inventor has specifically completed this invention for this type of RF module. Therefore, the invention described in claims 1 to 3 is a high-frequency filter circuit that provides an optimum one particularly for a fixed input frequency in such a frequency band.

Next, the invention according to claim 5 will be described. The invention according to claim 5 is a high-frequency filter circuit having a fixed input frequency of 240 MHz to 390 MHz formed on a printed circuit board as described above, wherein the printed circuit board has a dielectric constant of 4.5 to 4.8. Or less, line width 0.2 mm or more and 1.2 mm or less, line gap 0.2 m
A pattern coil of m or more and 0.4 mm or less is arranged adjacently, and a minimum distance between the coils is 0.3 mm or more and 1.6 mm or less.
The following is to provide a high frequency filter circuit in which a grounded conductive pattern is arranged between both coils. The features of the present invention are generally the same as those of the fourth aspect, but the dielectric constant of the printed circuit board is 4.5 or more.
The feature is that it is limited to eight or less. The high-frequency filter circuit provided by such a configuration exhibits excellent characteristics when the dielectric constant of the printed circuit board is 4.5 or more and 4.8 or less as described above. This configuration is optimal for the dielectric constant of the printed circuit board of 5 or more and 4.8 or less.

Next, the overall image of these inventions will be described with reference to the drawings. The high-frequency filter circuit as described in claims 1 to 5 has a practical configuration as shown in FIG. 4, for example. This is illustrated in a block diagram as shown in FIG. As shown in FIG. 7, in the input filter circuit of the conventional RF module, the signal is mixed through two stages of the double tuning circuit as described above, and the signal is transmitted to the IF frequency, that is, the intermediate frequency processing circuit. The input signal is filtered by a band-pass filter using C-coupling and M-coupling in order to eliminate unnecessary frequencies input to the transistor. After input to the transistor, the image signal at the desired frequency plus 43.4 MHz is removed. A low-pass filter and a band elimination filter are provided for the purpose of eliminating and eliminating unnecessary frequencies input to the mixer, and thereafter the signal is sent to the intermediate frequency processing circuit by connecting to the mixer.

Here, for the band-pass filter using both C-coupling and M-coupling, the above-mentioned inventions of claims 1 and 2 are applied. The band-pass filter is output and input to the transistor, and the band-elimination is performed. The processing of the signal when the signal enters the nation filter is performed by the high frequency filter circuit according to the third aspect. Here, as described above, this band elimination filter is a filter having a configuration as shown in FIG. 10, but this filter is generally called a fifth-order elliptic function filter, and the desired frequency plus 43 A steep trap is realized in the .4 MHz portion, and a high-quality signal can be sent to the mixer. Such a fifth-order elliptic function filter is also called a Cauer filter, but the invention according to claim 3 of the present invention is extremely useful for realizing such a filter with high accuracy and high reliability.

FIG. 6 shows a more specific block diagram of the proposed filter. The signal from the input line passes through the filter, is input to the transistor, and further passes through the filter and is sent to the mixer circuit. The filter in which the input signal is processed first is the filter according to claim 1 or 2, wherein the signal that has passed through the transistor is processed again according to claim 3. It is. It should be noted that comparing this with the conventional one, the conventional one has a configuration as shown in FIG. 8, in which a coil which is an insertion type component is used when an input signal passes. 8 shows.

As described above, when the coil which is an insertion type component is used, the number of steps and the number of components are increased, resulting in a problem that the reliability and cost of the electronic device are reduced as a whole. Further, a fifth-order elliptic function filter will be additionally described. FIG. 11 shows a fifth-order elliptic function filter type filter according to the present invention, that is, an RF pass characteristic according to the third aspect of the present invention. As shown in the lower right part of the graph of FIG. 11, 43.4 MHz from the desired frequency.
It can be seen that a large trap is formed at z. Here, the desired frequency is a portion indicated by a black triangle in FIG.

Table 2 shows the measured values of the general electrical characteristics of the RF module configured as described above. 1
To 5 are of the same quality formed under the same conditions. The measurement items are individually measured for each of the five units from the transmission frequency deviation to the transmission output, the standard input sensitivity, etc., and the current consumption. From this table, it is clear that good characteristics can be realized as the characteristics of the RF module for cordless phones used in Japan.

[Table 2]

Next, the invention according to claim 6 will be described. The invention according to claim 6 is an RF module for a cordless phone using a high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, as described above, wherein the line width is 0.2 mm or more and 1.2 mm or less. , 0.2m between lines
This is an RF module using a pattern coil of not less than m and not more than 0.4 mm. As described above, the inventions described in claims 1 to 5 are most suitable for an RF module corresponding to a frequency allocated to a cordless phone for domestic use, and a pattern coil as described above is used for such an RF module. When applied, a highly reliable and stable RF module can be realized.

[0028]

As described above, by using the high-frequency filter circuit and the RF module according to the present invention, it is possible to realize a sufficiently stable pattern coil within the tolerance of the pattern coil of the high-frequency filter formed simultaneously on the printed circuit board. In addition, the specification described in the present invention stipulates the permittivity and pattern width of the printed circuit board, the minimum distance between lines, the distance between adjacent coils or the grounded conductive pattern disposed between the coils, thereby ensuring reliable and high reliability. To get a bond,
Alternatively, it is possible to realize an excellent property that a bond can be sufficiently eliminated. In addition, when the high-frequency filter circuit realized as described above is used for an RF module, it is possible to realize an optimum input filter circuit for an RF module particularly assigned to domestic frequencies.

[Brief description of the drawings]

FIG. 1 is a front view of a pattern coil of the present invention.

FIG. 2 is a front view of an adjacent pattern coil of the present invention in which electromagnetic coupling is performed by a capacitor.

FIG. 3 is a front view of a pattern coil formed at a position separated by the pattern coil of the present invention.

FIG. 4 is a diagram showing an embodiment of a pattern coil in a high-frequency filter circuit.

FIG. 5 is a block diagram of the filter circuit of FIG. 4;

FIG. 6 is a circuit example of a fifth-order elliptic function filter of the present invention.

FIG. 7 is a block diagram of a conventional filter circuit.

FIG. 8 is a circuit example of a conventional filter.

FIG. 9 is a graph showing a relationship between a pattern width change amount and an inductance change amount.

FIG. 10 is an equivalent circuit diagram of the pattern coil of FIG. 3;

FIG. 11 is a graph showing characteristics of a fifth-order elliptic function filter.

[Explanation of symbols]

 11, 21, 31, 41 Printed circuit board 12, 22, 32, 42 Pattern coil 23 Capacitor 34 Conductive pattern d1, d2, d3 Between lines dm1, dm2, dm3, dm4, dm5 Minimum line width w1, w2, w3 Line width

Claims (6)

[Claims] 1. A high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, wherein the printed circuit board has a dielectric constant of 2 to 5 and a line width of 0.2 mm.
A high-frequency filter circuit using a pattern coil having a length of not less than 1.2 mm and a line gap of not less than 0.2 mm and not more than 0.4 mm. 2. A high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, wherein the printed circuit board has a dielectric constant of 4.3 to 4.9 and a line width of 0.2 mm to 1 mm. 0.2 mm or less and a pattern coil having a line spacing of 0.2 mm or more and 0.4 mm or less are arranged adjacently, and the minimum line gap between adjacently arranged coils connected in series with a capacitor is 0.1 mm or more and 0.1 mm or less. A high frequency filter circuit having a size of 3 mm or less. 3. A high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, wherein the printed circuit board has a dielectric constant of 4.3 or more and 4.9 or less, and a line width of 0.2 mm or more and 1 mm or less. 0.2 mm or less, a pattern coil having a line gap of 0.2 mm or more and 0.4 mm or less is arranged adjacently, a minimum line gap between the coils is 0.3 mm or more and 1.6 mm or less, and grounded between both coils. High frequency filter circuit with conductive patterns. 4. A 240M formed on a printed circuit board.
A high-frequency filter circuit having a fixed input frequency of not less than Hz and not more than 390 MHz, wherein the printed circuit board has a permittivity of not less than 4.3 and not more than 4.9 and a line width of not less than 0.2 mm and not more than 1.
A pattern coil of 2 mm or less and a line gap of 0.2 mm or more and 0.4 mm or less is arranged adjacently, and a minimum line gap between the coils is
A high-frequency filter circuit having a conductive pattern of 0.3 mm or more and 1.6 mm or less and grounded between both coils. 5. A 240M formed on a printed circuit board.
A high-frequency filter circuit having a fixed input frequency of not less than Hz and not more than 390 MHz, wherein the printed circuit board has a dielectric constant of not less than 4.5 and not more than 4.8, and a line width of not less than 0.2 mm and not more than 1.
A pattern coil of 2 mm or less and a line gap of 0.2 mm or more and 0.4 mm or less is arranged adjacently, and a minimum line gap between the coils is
A high-frequency filter circuit having a conductive pattern of 0.3 mm or more and 1.6 mm or less and grounded between both coils. 6. An RF module for a cordless telephone using a high-frequency filter circuit having a fixed input frequency formed on a printed circuit board, wherein the line width is 0.2 mm or more and 1.2 mm or less.
An RF module using a pattern coil with a length of 0.2 mm or less and a line gap of 0.2 mm or more and 0.4 mm or less.