JP2006074257A - High frequency bandpass filter and cable connector unit with built-in filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a narrow-band high frequency bandpass filter for applying superior characteristics on frequency dependency of signal intensity in a bandpass flat region in consideration of coordination with frequency characteristics of a peripheral circuit. <P>SOLUTION: The bandpass filter is mainly composed of a bandpass filter main unit 7M(including a slope formation inductive coupling unit 83), and auxiliary resonance circuits 90A, 90B. In the slope formation inductive coupling unit 83, a first induction coupling distribution constant line unit 82A between a signal input terminal 84 and a first main LC type parallel resonance circuit 14A in a first line LM1, and a second induction coupling distribution constant line unit 82B between a signal output terminal 86 and a second main LC type parallel resonance circuit 14B in a second line LM2, are put opposite in parallel at prescribed intervals. In the bandpass characteristics of a bandpass filter 7, this structure has a function for applying a gradient to a flat frequency characteristic region between each resonance trap electrodes on the low frequency edge side and the high frequency edge side, so that the intensity of the passing signal increases or decreases continuously according to the frequency. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is configured using a high-frequency bandpass filter for filtering interference waves mixed in a broadcast reception wave, and the high-frequency bandpass filter, and is inserted into a cable of a broadcast receiver in the middle. The present invention relates to a filter built-in type cable connector unit.

JP-A-9-51241

  In a receiver such as a television broadcast, a received signal from an antenna is input to a receiving circuit via a signal cable such as a coaxial cable. As a well-known problem, there are cases where interference is superimposed on a received signal due to various factors such as noise and radio wave interference, resulting in reception failure. Since such interference waves vary in degree and frequency band depending on the area where the receiver is installed and the surrounding environment, it is possible to solve the problem by providing a high-frequency filter in the receiver that allows the desired wave to pass and blocks the interference wave. Many. Patent Document 1 discloses an LC type band eliminate filter built in a cable connector unit as an example of such a high frequency filter. The band-eliminate filter selectively removes the interference wave by adjusting its cutoff band to the frequency band of the interference wave. Naturally, the pass band of the band-pass filter is adjusted to the frequency band of the desired wave. It is also possible to pass the desired wave selectively.

  Conventionally, the flatness of the frequency characteristics of the passband has been emphasized as the pass characteristic of the bandpass filter, but when considering the signal characteristics of the entire circuit in which the filter is incorporated, the flat filter pass characteristic is always suitable. Unlimited situations are also emerging. In particular, if the signal characteristics of the circuit surrounding the filter show a relatively strong frequency dependence in the passband of the bandpass filter, no matter how flat the pass characteristic is on the bandpass filter side, the frequency dependence of the peripheral circuit part The influence of the characteristics appears greatly, and it may occur that good signal frequency characteristics cannot be realized as a whole communication device.

  An object of the present invention is to provide a high-frequency bandpass capable of additionally providing a characteristic that is advantageous in coordinating with a frequency characteristic of a peripheral circuit in the frequency dependence of the signal strength in a flat region of the passband. An object of the present invention is to provide a filter and a filter built-in type cable connector unit using the filter.

Means and actions / effects for solving the problems

In order to solve the above problems, the high-frequency bandpass filter of the present invention is:
The signal input terminal and the signal output terminal are connected, and the signal main path divided into the first path on the signal input terminal side and the second path on the signal output terminal side is branched from the first path of the signal main path. The first main LC type parallel resonance circuit provided in such a manner as to short-circuit the first path and ground, and a branch from the second path of the signal main path, and short-circuiting the first path and ground A bandpass filter main part having a second main LC type parallel resonant circuit provided and exhibiting a bandpass characteristic of a predetermined center frequency;
An auxiliary resonance circuit that forms a resonance trap pole on each of the low-frequency end side and the high-frequency end side of the passband formed by the main part of the bandpass filter;
A first distributed constant line for inductive coupling provided between the signal input terminal and the first main LC type parallel resonance circuit in the first path, and a signal output terminal and the second main LC type parallel resonance in the second path. In parallel with the second inductive coupling distributed constant line section provided between the circuit and the circuit at predetermined intervals, the bandpass characteristics of the bandpass filter can be reduced between the low frequency end side and the high frequency end side. And a slope-forming inductive coupling portion that imparts a slope in which the passing signal intensity continuously increases or decreases depending on the frequency in a flat frequency characteristic region sandwiched between the resonance trap electrodes. To do.

  A π-type filter in which a capacitor is provided on a signal input / output main path and two main LC type parallel resonant circuits are suspended at both ends thereof exhibits characteristics as a bandpass filter. However, if the π-type filter is used as it is, the pass band becomes broad, and a pass characteristic with good selectivity cannot be realized. In this case, it is possible to realize pass characteristics with good selectivity by providing auxiliary resonance circuits that form resonance trap poles on the low-frequency end side and the high-frequency end side of the pass band.

  In the π-type filter having the above-described configuration, the present inventors use a circuit in which the capacitor is replaced with an inductive coupling unit in which the distributed constant line unit is opposed in parallel as a main part of the band-pass filter. The present invention finds that a flat frequency characteristic region sandwiched between the resonance trap poles on the side and the high frequency end side can be given a gradient in which the passing signal intensity continuously increases or decreases depending on the frequency. It came to complete. With a simple configuration of a parallel facing structure of distributed constant line portions, a gradient frequency characteristic can be reliably and inexpensively imparted to the flat frequency characteristic region of the bandpass filter. For example, if the peripheral circuit to which the bandpass filter is connected has an undesired gradient in terms of frequency characteristics in the passband of the filter, this can be suppressed by using the gradient characteristic assigned to the flat frequency characteristic region of the filter. For example, the frequency characteristics can be easily coordinated with peripheral circuits.

The sign (orientation) of the gradient formed in the passband can be easily set by the phase relationship of the signals passing through the first inductive coupling distributed constant line portion and the second inductive coupling distributed constant line portion. In this case, the first main LC type parallel resonant circuit and the second main LC type from the signal input terminal and the signal output terminal of the first distributed constant line part for inductive coupling and the second distributed constant line part for inductive coupling, respectively. The direction toward the ground of the parallel resonant circuit is defined as the forward direction.
(For positive slope)
In the inductive coupling portion for forming the gradient, the first inductive coupling distributed constant line portion and the second inductive coupling distributed constant line portion face each other so that the forward directions are opposite to each other, thereby obtaining a flat frequency characteristic region. Further, it is possible to give a positive gradient in which the passing signal intensity continuously increases as the frequency increases.
(For negative slope)
In the inductive coupling part for forming the gradient, the first inductive coupling distributed constant line part and the second inductive coupling distributed constant line part are opposed to each other so that the forward directions coincide with each other. In addition, a negative gradient in which the passing signal intensity continuously decreases as the frequency increases can be provided.

  In particular, when the signal input terminal and the signal output terminal are scheduled to be connected to a signal cable having a negative frequency characteristic in which the passing signal intensity continuously decreases as the frequency increases, inductive coupling for gradient formation is planned. The negative frequency characteristic of the signal cable can be at least partially offset by the positive slope characteristic formed by the section. That is, when a signal cable (especially a shielded cable such as a coaxial cable) exists as a peripheral circuit of a bandpass filter, the signal cable has a higher signal radiation loss and a lower shielding effect as the frequency becomes higher. Indicates negative frequency dependence. However, if the frequency characteristics of the bandpass filter are set to the positive slope characteristics as described above, the frequency dependency on the signal cable side can be canceled, and the frequency characteristics of the entire circuit comprising the bandpass filter and the signal cable are flatter. Frequency characteristics can be realized.

  Next, the inductances included in the first main LC type parallel resonant circuit and the second main LC type parallel resonant circuit can both be constituted by dielectric resonators. Thereby, the Q value of the parallel resonant circuit can be further increased, and the frequency selection characteristic (or trap attenuation effect) of the filter can be further improved. In this case, on the signal input terminal side and the signal output terminal side, the impedance for making the input / output impedance of the bandpass filter close to the input impedance of each resonance circuit including the dielectric resonator is provided on the first path and the second path. An adjustment part can be provided. In the parallel resonance circuit, the dielectric resonator included therein has a very large Q value and high impedance. Therefore, in order to bring the impedance of the input and output closer to the impedance on the parallel resonant circuit side, the provision of the impedance adjusting unit as described above is effective in suppressing reflection loss due to impedance mismatch and improving the gain of the filter. Convenient. The impedance adjustment unit can use an inductor or a capacitor in which circuit constants are determined so as to exhibit high impedance in a desired frequency band.

Next, the filter built-in type cable connector unit of the present invention includes:
A filter housing formed with a first connector part and a second connector part for connecting a signal cable of the device;
The high-frequency bandpass filter of the present invention is mounted, and has a circuit board accommodated in the filter housing so that the signal input terminal and the signal output terminal are electrically connected to the first connector part and the second connector part, respectively.
At least a part of the capacitance of the capacitors included in the first main LC type parallel resonant circuit and the second main LC type parallel resonant circuit is constituted by a trimmer capacitor, and the capacitance adjusting unit of the trimmer capacitor has a target signal. It is a variable tuning unit for tuning the pass band of the band pass filter to the frequency.

  According to the above configuration, since the capacitance included in the two main LC type parallel resonant circuits is variably configured as a trimmer capacitor, for example, the pass band of the filter can be easily tuned with respect to the frequency of the disturbing wave.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a plan view and left and right side views showing an external appearance of a filter built-in type cable connector unit (hereinafter also simply referred to as “connector unit”) 1 according to an embodiment of the present invention. FIG. FIG. The connector unit 1 includes a filter housing 13 in which a first connector portion 11 and a second connector portion 12 for connecting the signal cables 6 of the devices are formed, and is accommodated in the filter housing 13. A circuit board 70 on which the band-pass filter circuit 7 to be inserted between the second connector part 12 is mounted and a variable tuning part 71 (trimmer capacitor 15: FIG. 4) incorporated in the band-pass filter 7 on the circuit board 70. (Described later in the circuit diagram).

  FIG. 3 shows a circuit configuration example of the bandpass filter 7. This circuit is for UHF television broadcast reception (the UHF band frequency range is 470 MHz to 770 MHz for U13Ch to U62Ch), and the bandpass filter main part 7M (including the gradient forming inductive coupling part 83) The auxiliary resonance circuits 90A and 90B are configured as the main parts. The bandpass filter main part 7M connects the signal input terminal 84 and the signal output terminal 86, and is divided into a first path LM1 on the signal input terminal 84 side and a second path LM2 on the signal output terminal 86 side. A first main LC-type parallel resonance circuit 14A that is branched from the first path LM1 of the signal main path and the first path LM1 and the ground, and a second path of the signal main path It has a second main LC type parallel resonant circuit 14B which is branched from LM2 and short-circuited between the first path LM1 and the ground, and exhibits a band pass characteristic of a predetermined center frequency. is there. The auxiliary resonance circuits 90A and 90B form resonance trap poles on the low frequency end side and the high frequency end side of the pass band formed by the bandpass filter main portion 7M. Note that a choke coil (not shown) for cutting unnecessary frequency components may be provided as appropriate between the signal input terminal 84 and the signal output terminal 86 in parallel with the signal main path.

  The gradient forming inductive coupling portion 83 includes a first inductive coupling distributed constant line portion 82A provided between the signal input terminal 84 and the first main LC type parallel resonant circuit 14A in the first path LM1, and a second In the path LM2, a second inductive coupling distributed constant line portion 82B provided between the signal output terminal 86 and the second main LC type parallel resonant circuit 14B is opposed in parallel at a predetermined interval. . With this structure, in the band-pass characteristics of the band-pass filter 7, the pass signal intensity is continuously increased according to the frequency in the flat frequency characteristic region sandwiched between the resonance trap electrodes on the low frequency end side and the high frequency end side. Serves to provide an increasing or decreasing gradient. In the circuit configuration of FIG. 3, the inductive coupling portion 83 for forming gradients causes the first inductive coupling distributed constant line portion 82 </ b> A and the second inductive coupling distributed constant line portion 82 </ b> B to have their forward directions opposite to each other. And a positive gradient in which the passing signal intensity continuously increases as the frequency increases is given to the flat frequency characteristic region. However, depending on the purpose, as shown in FIG. 7, the first inductive coupling distributed constant line portion 82A and the second inductive coupling distributed constant line portion 82B are opposed to each other so that the forward directions thereof coincide with each other. Thus, it is also possible to give a negative gradient in which the passing signal intensity continuously decreases as the frequency increases in the flat frequency characteristic region. In the following, the case where a positive gradient is applied will be described as a representative.

  The inductances included in the first main LC type parallel resonant circuit 14A and the second main LC type parallel resonant circuit 14B are both dielectric resonators 17A and 17B (in this embodiment, the resonance frequency is about 880 MHz, the Q at no load). The value is about 1500). Impedance adjusting units 80A and 80B are provided on the input side and the output side of the main path LM, respectively. The impedance adjusters 80A and 80B serve to suppress the reflection loss due to impedance mismatch by bringing the input and output impedances (for example, about 50Ω) of the filter closer to the impedance of the parallel resonant circuits 14A and 14B.

  The impedance adjuster includes inductors 181A and 181B whose circuit constants are determined so that the input / output impedance (50Ω) matches the first main LC parallel resonant circuit 14A and the second main LC parallel resonant circuit 14B, Capacitors 180A and 180B can be used (in the present embodiment, both are combined, but each can be used alone). In addition, although the distributed constant line portion can be adopted as the impedance adjusting portion, it is desirable to use a lumped constant circuit element such as an inductor or a capacitor in view of making the circuit board 70 compact. In the present embodiment, the inductors 181A and 181B use winding coils (inductors) 181A and 181B of about several turns (3 to 15 turns: inductance is 30 to 150 nH) as the impedance adjusters 80A and 80B, Capacitors 180A and 180B use chip capacitors having a capacitance of 1000 pF (playing a role of cutting off direct current and allowing high-frequency signals to pass).

  Capacitances of capacitors included in the first LC type parallel resonant circuit 14A and the second LC type parallel resonant circuit 14B are constituted by trimmer capacitors 15A and 15B (capacitance adjustment range 1.0 pF to 10 pF in this embodiment). ing. The capacitance adjusting units of the trimmer capacitors 15A and 15B are a variable tuning unit 71 for tuning the pass band of the bandpass filter to a target signal frequency.

  The auxiliary resonant circuit has a first main LC type parallel resonant circuit 14A between the first path LM1 and the second path LM2 and the ground on the opposite side of the slope forming inductive coupling portion 83 from each other. And first and second inductors 91A and 91B (inductance: 20 to 50 nH) and capacitors 93A and 93B (capacitance: 0.5 pF) respectively connected in parallel to the second main LC type parallel resonant circuit 14B. It is composed of two auxiliary LC series resonance circuits 90A and 90B. Impedance adjusting units 80A and 80B are arranged between the branch point of the auxiliary LC series resonant circuit and the branch point of the main LC parallel resonant circuit in each of the first path LM1 and the second path LM2. Thereby, steeper and deep trap poles can be formed at both ends of the band pass characteristic formed by the main part 7M of the band pass filter, the filter selectivity can be improved, and the narrow band pass characteristic can be easily realized. In the present embodiment, auxiliary capacitors 92A and 92B that are coupled in parallel resonance with the inductor 91 are provided in order to further increase the steepness of the trap pole.

  FIG. 4 shows an example of component layout of the circuit board 70. The upper part shows the layout on the front surface side, and the lower part shows the layout on the back surface side. The trimmer capacitors 15A and 15B of the first main LC type parallel resonance circuit 16 and the second main LC type parallel resonance circuit 17 are mounted on the back side of the circuit board 70 together with the winding coils 80A and 80B forming the impedance adjustment unit. Has been. On the other hand, the dielectric resonators 17A and 17B of the first main LC type parallel resonant circuit 16 and the second main LC type parallel resonant circuit 17 are mounted on the surface side of the circuit board 70.

  In the above circuit configuration using the dielectric resonators 17A and 17B, the dielectric resonators 17A and 14A of the first main LC type parallel resonant circuit 14A and the second main LC type parallel resonant circuit 14B mounted on the circuit board 70 are provided. The leading ends of the lead wires 82A and 82B of 17B are connected to the first route LM1 and the second route LM2 on the circuit board 70. The lead wires 82A and 82B are used as the first inductive coupling distributed constant line portion 82A and the second inductive coupling distributed constant line portion 82B. With this configuration, the gradient forming inductive coupling portion 83 can be formed in such a manner that the lead portions of the dielectric resonators 17A and 17B are used in combination with the distributed constant line portions 82A and 82B for inductive coupling. Since it is not necessary to dare to form a printed wiring portion or the like for the inductive coupling portion 83 on the circuit board 70, the board configuration can be simplified. Further, as shown as “main part” in FIG. 4, the lead wires 82A and 82B forming the distributed constant line portion for inductive coupling are arranged so as to float from both the main surfaces of the substrate, whereby the lead wires 82A on the main surface of the circuit board 70 are arranged. , 82B can be routed to a position directly below the terminal board 82B, and a limited board area can be effectively utilized.

  The magnitude of the frequency characteristic gradient formed in the flat frequency characteristic region of the band-pass filter 7 by the gradient forming inductive coupling unit 83 is determined by the first inductive coupling distributed constant line unit 82A and the second inductive coupling distributed constant line. It can be easily adjusted by the facing interval σ with the portion 82B or the facing section length LS. In particular, the facing interval σ has a larger influence on the gradient change than the facing section length LS, and therefore can be used as a main adjustment factor of the gradient. On the other hand, the change of the opposing section length LS can be effectively used for fine adjustment of the gradient.

  The lead wires 82A and 82B of the dielectric resonators 17A and 17B are lead wires 82A and 82B having a diameter larger than the Cu foil thickness forming the printed wiring portions LM1 and LM2 on the circuit board 70. Since the printed wiring portions LM1 and LM2 are in contact with a dielectric made of a polymer material or the like forming a substrate, the Q is relatively small (for example, around 50), but the lead wires 82A and 82B are arranged in the air, so the Q is large. <For example, 1000 or more>. As a result, the Q and inductance of the distributed constant line used for the inductive coupling portion 83 for forming the gradient can be increased. Rather than forming the inductive coupling portion using the printed wiring portion, the gradient to the inductive coupling effect and thus the pass characteristic is obtained. The imparting effect can be achieved much more significantly. The thickness of the lead wires 82A and 82B is selected in the range of 0.3 mm to 1 mm, for example.

  In the present embodiment, the dielectric resonators 17A and 17B of the first main LC type parallel resonant circuit 14A and the second main LC type parallel resonant circuit 14B are opposed to each other at the end surfaces on the side from which the lead wires 82A and 82B are drawn. In this way, the circuit board 70 is mounted on the circuit board 70, and the lead wires 82A and 82B are arranged opposite to each other on the circuit board 70 so that the forward directions are opposite to each other. Thereby, in order to realize a positive gradient characteristic, a layout in which the lead wires 82A and 82B are arranged in a positional relationship in which the forward directions are reversed from each other can be easily obtained.

  FIG. 6 shows an example of measurement of pass characteristics of the bandpass filter 7 having the circuit configuration of FIG. However, in the inductive coupling portion 83 for forming the gradient, the diameter of each lead wire forming the first inductive coupling distributed constant line portion 82A and the second inductive coupling distributed constant line portion 82B is about 0.5 mm, The opposing interval σ is set to an average value of about 3 mm, and the opposing section length LS is set to about 10 mm. The center frequency of the pass band is about 730 MHz (note that the trapping pole on the lower side is out of the scale and is not shown).

The bandpass filter 7 has a passband center frequency f ₀ determined in the UHF band, and the signal input terminal 84 and the signal output terminal 86 are connected to each other as a signal cable by the first connector 11 and the second connector 12. Coaxial cables 6 (see FIG. 1) are connected to each other. Since the coaxial cable 6 has a higher signal radiation loss and a lower shielding effect as the frequency becomes higher, the transmission signal strength has a negative frequency dependency as shown by a broken line in FIG. However, if the frequency characteristic of the bandpass filter 7 is a positive gradient characteristic as indicated by a one-dot chain line due to the action of the gradient forming inductive coupling portion 83, the frequency dependency on the coaxial cable 6 side indicated by the broken line is reduced. Cancellation is possible, and a flatter frequency characteristic can be realized as shown by a solid line when viewed in the entire circuit including the bandpass filter 7 and the coaxial cable 6. In addition, with positive frequency characteristics, moderate attenuation can be applied to the signal on the low frequency side of the pass band. For example, two adjacent channels (for example, adjacent channels of terrestrial digital and terrestrial analog) It is also possible to realize a function for limiting the passing output of the low frequency side.

  This is the end of the description of the bandpass filter 7, and a supplementary description of details specific to the present embodiment will be given below. As shown in FIGS. 1 and 2, the filter housing 13 is formed with a main body portion 2 formed in a cylindrical shape having a first connector portion 11 at one end and an opening at the other end, and a second connector portion 12. And a lid portion 4 that detachably closes the opening of the main body portion 2. Both the main body 2 and the lid 4 are made of metal such as stainless steel. The circuit board 70 formed in a horizontally long shape is a normal printed wiring board, and one end in the longitudinal direction is fixed to the inner end surface of the lid portion 4, and the lid portion 4 is inserted while the circuit board 70 is inserted inside the main body portion 2. The main body 2 is attached. With this configuration, the circuit board 70 can be assembled very easily into the filter housing 13. In the present embodiment, the lid portion 4 is configured such that a male screw portion 43 formed on the outer peripheral surface of the lid portion main body 42 is screwed into a female screw portion 24 formed on the inner peripheral surface of the opening of the main body portion 2. In addition, a flange portion 41 having a diameter larger than the opening inner diameter of the main body 2 is integrated with the rear end side of the lid main body 42.

  As shown in FIG. 2, lead wires 84 and 86 forming a signal input portion and a signal output portion extend from each end portion in the longitudinal direction of the circuit board 70. The input / output lead wires 84 and 86 are drawn out to the first connector portion 11 and the second connector portion 12 through lead extraction through holes 2h and 4h formed on the main body portion 2 and the lid portion 4 side, respectively. ing. And, between the lead extraction through holes 2h, 4h, the gap between the conductor portion forming the lid portion 4 or the main body portion 2 and the lead wires 84, 86 is filled with the waterproof polymer material portions 54, 94. Yes. Thereby, the penetration | invasion of the water drop etc. in the filter housing 13 from a connector side can be prevented effectively.

  In the present embodiment, the second connector 12 has a cylindrical portion 49 protruding from the rear end surface of the lid portion 4 (a male screw portion 31 for screwing the cable fixing nut 5 is formed on the outer peripheral surface). The female connector has a built-in socket fitting 48 for holding the core wire end of the coaxial cable to be coupled. The socket fitting 48 is for holding the core wire of the inserted coaxial cable 6 in a conductive state, and is soldered to the lead wire 86 from the circuit board 70. Further, the first connector 11 is constituted by a cylindrical portion 56 protruding from the end surface on the opposite side of the main body portion 2, and a cable fixing nut 5 ′ having a female screw portion 52 is interposed via the sliding ring 23. A cylindrical portion 56 is rotatably fitted on the outer peripheral surface. Then, as shown in FIG. 1, the terminal bolt ring 6T (FIG. 1) attached to the end of the coaxial cable 6 is screwed into the female thread portion of the nut 5 'for connection.

  As shown in FIG. 2, the above-described lead wire 84 extends from the longitudinal end portion of the circuit board 70, and the lead wire is positioned at a position corresponding to the extending-side base end portion of the lead wire 84 of the circuit board 70. A shield conductor 89 surrounding the periphery of 84 is provided. The shield conductor 89 is electrically connected to the ground conductor foil formed on the circuit board 70. Thereby, the high-frequency grounding effect is further enhanced.

  In the present embodiment, the shield conductor 89 is formed such that a belt-shaped metal plate is bent into a U shape, and protrusions at both ends are inserted into the mounting holes of the circuit board 70 so as to be electrically connected to the ground conductor foil on the circuit board 70 side. The structure is fixed by soldering. The shield conductor 89 is in contact with the inner wall surface of the filter housing 13 and forms a part of the ground path. As shown in FIG. 8, if a part of the shield conductor 89 is a spring contact portion 89 a that is elastically deformed by contact with the inner surface of the filter housing 13 (here, the main body portion 2), the shield conductor 89 is formed inside the housing of the substrate 70. Even if deformation such as misalignment or torsion occurs, the spring contact portion 89a is biased toward the filter housing 13 by the elastic return force, so that contact for grounding can be made more reliable. In the present embodiment, a spring abutting portion 89 a that abuts against the inner surface of the bottom portion of the main body portion 2 and is elastically biased in the insertion axis direction of the substrate 70 is provided. Thus, when the lid portion 7 is screwed and attached to the main body portion 2, even if the screw stroke (determined by a positioning phase between an operation hole 21 and a capacity adjusting screw portion 71 described later) slightly varies, The variation can be absorbed by the elastic deformation of the contact portion 89a, and a good ground contact state can always be obtained. Here, with respect to the strip-shaped metal plate forming the shield conductor 89, a certain length of cut is made from the longitudinal edge of the metal plate along the edge on the rear side in the longitudinal direction of the substrate in the width direction. The above-described spring contact portion 89a is formed by bending the elongated tongue-shaped metal piece portion separated by the above in a direction away from the notch in the metal plate width direction. Further, the spring contact portions 89a are formed at both ends of the belt-shaped metal plate so that the shield conductor 89 can be stably spring-contacted with the filter housing 13. In order to use a part of the metal plate as it is as the spring contact portion 89a, the entire metal plate is made of a spring metal material, here phosphor bronze.

  Further, as shown in FIG. 2, a board holding slot part 86 for holding and holding one end part of the circuit board 70 is formed on the inner end face of the lid part 4, and a ground conductor covering each main surface of the circuit board 70 is formed. The foil is electrically connected to the main body portion 2 through the substrate holding slot portion 86 and the lid portion 4. The board holding slot portion 86 is composed of a pair of metal rib portions protruding from the end face of the lid portion 4, and the end portion of the circuit board 70 is inserted into a groove-like space formed between the rib portions. The circuit board 70 is held by caulking so that the distance between the rib portions is reduced. By the caulking, the ground conductor foils on the front and back of the substrate 70 are in firm contact with the metal rib portion, and the grounding effect of the circuit through the filter housing 13 can be enhanced. In addition, since the end portion of the circuit board 70 on the non-supporting side becomes a vibration release end, even when an impact is applied from the outside, the circuit board 70 can be absorbed by the board vibration and hardly cause breakage or disconnection. Specifically, as shown in FIG. 1, the main body 2 has a shield conductor of the coaxial cable 6 in a state in which the coaxial cable 6 forming the signal cable is connected to the first connector portion 11 and the second connector portion 12. It is supposed to conduct to the part 6s.

  In the embodiment described above, all the high-frequency bandpass filters are incorporated in the cable connector unit with a built-in filter. However, the usage mode of the high-frequency bandpass filter of the present invention is not limited to this. For example, a shape incorporated in a box-type case (a panel in which input / output coaxial connectors are arranged) or a band-pass filter built in a communication device can be used.

The top view which shows an example of an external appearance structure of the filter built-in type cable connector unit of this invention. FIG. 2 is a front sectional view showing an internal structure of the connector unit of FIG. 1. The circuit diagram which shows the 1st example of a filter circuit. Explanatory drawing which shows an example of the board | substrate mounting form of a filter circuit. The schematic diagram which shows an example of an effect | action of the band pass filter of this invention. The graph which shows an example of the pass characteristic of the band pass filter by the circuit of FIG. The circuit diagram which shows the 2nd example of a filter circuit.

Explanation of symbols

1 Built-in cable connector unit 6 Signal cable (coaxial cable)
7 Band pass filter circuit 7M Main part of band pass filter LM1, LM2 Main route (first route / second route)
14A, B Main LC type parallel resonant circuit 15A, B Trimmer capacitor (variable tuning part)
17A, B Dielectric resonator 70 Circuit board 71 Tuning operation part 82A, B Lead wire (first and second distributed constant lines for inductive coupling)
83 Inductive coupling for slope formation 84 Signal input terminal (lead wire)
86 Signal output terminal (lead wire)
90A, 90B Auxiliary resonance circuit

Claims (10)

A signal main path is connected to the signal input terminal and the signal output terminal, and is divided into a first path on the signal input terminal side and a second path on the signal output terminal side, and branches from the first path of the signal main path And a first main LC parallel resonant circuit provided in such a manner as to short-circuit the first path and the ground, a branch from the second path of the signal main path, and the first path and the ground A second main LC type parallel resonant circuit provided in a short-circuited manner, and a main part of a bandpass filter showing a bandpass characteristic of a predetermined center frequency;
An auxiliary resonance circuit for forming a resonance trap pole on each of a low frequency end side and a high frequency end side of a pass band formed by the main part of the band pass filter;
A first distributed constant line section for inductive coupling provided between the signal input terminal and the first main LC type parallel resonant circuit in the first path; and the signal output terminal and the first in the second path. By making the second inductive coupling distributed constant line portion provided between the two main LC parallel resonant circuits face each other in parallel at a predetermined interval, the low-frequency characteristics of the bandpass filter can be reduced. A gradient forming inductive coupling unit that gives a flat frequency characteristic region sandwiched between the resonance trap poles on the end side and the high frequency end side to a gradient in which the passing signal intensity continuously increases or decreases according to the frequency; ,
A high-frequency band-pass filter characterized by comprising: The gradient forming inductive coupling unit adjusts the magnitude of the gradient according to a facing interval or a section length of the first inductive coupling distributed constant line unit and the second inductive coupling distributed constant line unit. The high-frequency band-pass filter according to claim 1. The first main LC type parallel resonant circuit and the second main distributed constant line section for the first inductive coupling and the second distributed constant line section for the inductive coupling from the signal input terminal and the signal output terminal, respectively. With the direction toward the ground of the LC parallel resonant circuit as the forward direction, the inductive coupling unit for forming a gradient includes the first distributed constant line unit for inductive coupling and the second distributed constant line unit for inductive coupling. 2. The positive frequency gradient in which the pass signal intensity continuously increases with an increase in frequency is imparted to the flat frequency characteristic region by facing the forward directions so as to be opposite to each other. Item 3. A high-frequency bandpass filter according to Item 2. The signal input terminal and the signal output terminal are planned to be connected to a signal cable having a negative frequency characteristic in which the passing signal intensity continuously decreases as the frequency increases. 4. The high-frequency band-pass filter according to claim 3, wherein the positive frequency characteristic to be formed at least partially cancels the negative frequency characteristic of the signal cable. The first main LC type parallel resonant circuit and the second main distributed constant line section for the first inductive coupling and the second distributed constant line section for the inductive coupling from the signal input terminal and the signal output terminal, respectively. With the direction toward the ground of the LC parallel resonant circuit as the forward direction, the inductive coupling unit for forming a gradient includes the first distributed constant line unit for inductive coupling and the second distributed constant line unit for inductive coupling. The negative frequency gradient in which the passing signal intensity continuously decreases as the frequency increases is imparted to the flat frequency characteristic region by facing each other so that the forward directions coincide with each other. 2. A high-frequency bandpass filter according to 2. The inductances included in the first main LC type parallel resonant circuit and the second main LC type parallel resonant circuit are both configured by dielectric resonators,
In the signal input terminal side and the signal output terminal side, the input and output impedances of the band pass filter are made close to the input impedance of each resonance circuit including the dielectric resonator in the first path and the second path. The high-frequency band-pass filter according to claim 1, wherein an impedance adjusting unit is provided. Lead ends of the dielectric resonators of the first main LC type parallel resonant circuit and the second main LC type parallel resonant circuit mounted on the circuit board are connected to the first path on the circuit board and the The high-frequency bandpass filter according to claim 6, wherein the lead wire is connected to the second path and the lead wires are used as the first inductive coupling distributed constant line portion and the second inductive coupling distributed constant line portion. The dielectric resonators of the first main LC type parallel resonant circuit and the second main LC type parallel resonant circuit have the requirements according to claim 3, and end faces on the side from which the lead wires are drawn face each other. The high-frequency band-pass filter according to claim 7, wherein the lead wires are mounted on the circuit board so that the forward directions are opposite to each other on the circuit board. The auxiliary resonant circuit includes the first main LC type parallel resonance between the first path and the second path and the ground on the opposite side of the slope forming inductive coupling portion. A first auxiliary LC parallel resonance circuit connected in parallel to the circuit and the second main LC type parallel resonance circuit, wherein the impedance adjustment unit includes the first path and the second 9. The high-frequency bandpass filter according to claim 7, wherein each of the paths is disposed between a branch point of the auxiliary LC parallel resonant circuit and a branch point of the main LC parallel resonant circuit. A filter housing formed with a first connector part and a second connector part for connecting a signal cable of the device;
The high-frequency bandpass filter according to any one of claims 1 to 9 is mounted so that the signal input terminal and the signal output terminal are electrically connected to the first connector part and the second connector part, respectively. A circuit board housed in the filter housing,
At least a part of the capacitance of the capacitors included in the first main LC type parallel resonant circuit and the second main LC type parallel resonant circuit is constituted by a trimmer capacitor, and the capacitance adjusting unit of the trimmer capacitor has the purpose A cable connector unit with a built-in filter, characterized by being a variable tuning unit for tuning the pass band of the bandpass filter to a signal frequency to be transmitted.

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