JP4854589B2 - Polarized bandpass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To offer a polarity type band pass filter which can effectively prevent receiving disturbance from adjacent channel waves under an overcrowded frequency usage condition by a simple and low cost construction. <P>SOLUTION: A main circuit A is prepared, which is provided with a main parallel resonant unit in which a first dielectric resonator CV2 and a main resonant capacitor VC2 are connected in parallel resonant coupling on a signal transmission path 86, and forms a second attenuation pole; and a main series resonance unit which has a series resonant coupling element C2 which comprises a capacitor or an inductor which carries out series resonance with the main parallel resonant circuit. Moreover, a trap circuit B is prepared in which a second dielectric resonator CV1 of an inductor and a resonant capacitor VC1 for a trap are connected as parallel resonant coupling in a form of branching from the signal transmission path 86 to the ground, and which forms a first attenuation pole in a position where it overlaps with a series resonant pass-through peak of the main series resonant unit. Furthermore, a base attenuation amount adjustment circuit C is prepared which has capacitors for attenuation adjustment C3, C4, and adjusts a base attenuation amount of a blocking area adjacent in a low area side and a high area side of the pass band. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a polarized bandpass filter.

JP 2006-67522 A

  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. Such interference waves have different degrees and frequency bands depending on the area where the receiver is installed and the surrounding environment, and therefore, a filter that covers a necessary band is often externally attached to the receiver.

  In recent years, the form of radio broadcasting has become very diversified, and the tendency to increase the number of channels has been remarkable, so countermeasures against interference and interference have become more urgent. For example, in the case of the UHF band for terrestrial broadcasting, in addition to the setting of an analog broadcasting channel, terrestrial digital broadcasting has recently started in the same UHF band. Terrestrial digital broadcasting is planned to completely replace the existing analog terrestrial broadcasting in the future, but analog / digital simultaneous broadcasting will be performed until 2011 in consideration of the spread of receivers. ing. Therefore, the frequency usage situation of the UHF band is greatly overcrowded, and the problem of reception failure due to the adjacent channel wave and the same channel wave has become serious. Unlike harmonic interference waves and the like, these appear very close to the reception frequency of the desired wave, and therefore, it is necessary to narrow the band of the filter used for the removal (Patent Document 1).

  In the case of simulcasting in the UHF band as described above, the frequency usage situation becomes overcrowded, so that reception failures due to adjacent channel waves and the same channel wave are more likely to occur. For example, in digital television regional broadcasting of low power transmission When receiving a weak and medium electric field, the deterioration of the reception quality becomes a big problem. Digital broadcasting differs from analog broadcasting in that when the reception level falls to a certain threshold level, image quality deterioration due to block noise or the like occurs very sharply. Therefore, in low-power transmission broadcasting, reception C / N for guaranteeing image quality The ratio margin is inevitably reduced. In particular, when regional broadcast channels with low power transmission are sandwiched between high-power transmission wide-area digital broadcast channels and analog broadcast channels, these wide-area digital broadcast channels and high-level analog broadcasts Under the influence of non-linear distortion caused by the high received power of the channel group, the video quality deterioration of the regional broadcast channel is particularly likely to occur.

  The problem of the present invention is that it is possible to effectively prevent reception interference due to adjacent channel waves in an overcrowded frequency usage situation with a simple and inexpensive configuration, and in particular, it eliminates the gap in the frequency band of the high power transmission broadcast group. Even when low-power transmission broadcasts such as regional broadcast channels are made, the effects of nonlinear distortion from these high-power transmission broadcast groups can be effectively avoided, and the signals of these high-power transmission broadcast groups are excessively transmitted. It is an object of the present invention to provide a polarized bandpass filter that can greatly improve the reception quality of a low-power transmission broadcast without attenuation.

Means for Solving the Problems and Effects of the Invention

The present invention relates to a polarized bandpass filter having a low-frequency side first attenuation pole and a high-frequency side second attenuation pole at both ends of the passband.
A signal transmission line in which one end is an input unit and the other end is an output unit;
A main dielectric resonator that forms an inductor on the signal transmission line and a main resonance capacitor are coupled in parallel resonance to generate a parallel resonance attenuation peak for forming a second attenuation pole, and the main parallel resonance circuit A main circuit having a series resonance coupling element having a series resonance coupling element including a capacitor or an inductor that is coupled in series resonance with the main resonance section having a series resonance passing peak at a position corresponding to the first attenuation pole;
A parallel resonance part for traps, which is provided in a form branched from the signal transmission line to the ground side, and in which a dielectric resonator for traps forming an inductor and a parallel resonance coupling capacitor are coupled in parallel resonance, and series resonance with the parallel resonance part for traps A trap circuit having a series resonant coupling element including a capacitor or an inductor to be coupled, and generating a series resonant attenuation peak for forming a first attenuation pole at a position adjacent to the series resonant passing peak of the main series resonant unit;
A base attenuation adjustment circuit having an attenuation adjustment capacitor provided so as to branch from the signal transmission path to the ground side, and adjusting the base attenuation of the stop band adjacent to the low band side or the high band side of the pass band It is characterized by comprising.

  In the polarized bandpass filter of the present invention, it is the main circuit that determines the basic shape of the passband, and a series of capacitors or inductors is connected to the main parallel resonance part in which the dielectric resonator having a large Q value is incorporated. It has a structure in which the main series resonance part having the resonance coupling element is directly connected. Its pass characteristics gradually increase from the first base level, which is either the high-frequency stopband or the low-frequency stopband, toward the local maximum derived from the series resonance point to form a series resonance pass peak. The series resonance passing peak decreases by sharply decreasing toward the parallel resonance point level forming the second attenuation pole, and returning to the second base level forming the other of the high frequency side or the low frequency side. Form a parallel resonance attenuation peak paired with. Then, by adding a trap circuit that generates a series resonance attenuation peak at a position adjacent to the series resonance passing peak, a narrow and deep first attenuation pole peculiar to the trap circuit having a steep attenuation characteristic on both sides of the pole is formed. .

  When the band of the selected desired channel for low power transmission is adjusted to the pass band as described above, the attenuation peak forming this first attenuation pole is adjacent to the signal of the selected desired channel on the first attenuation pole side. It is possible to pass through a signal of a high power transmission channel that is pinpointed out. In the present invention, a base attenuation adjustment circuit for adjusting the base attenuation of the stop band adjacent to the low band side and the high band side of the pass band (that is, the first or second base level) is provided. Thus, the signal passing level of the high power transmission channel can be optimized. As a result, even when a low-power transmission broadcast is made through a gap in the frequency band of the high-power transmission broadcast group, the adjacent high-power transmission broadcast does not significantly affect the received signal level of the low-power transmission broadcast. The signal level of the group can be attenuated appropriately. As a result, it is possible to effectively avoid the influence of non-linear distortion on the received signal of the low-power transmission broadcast, and greatly reduce the reception quality of the low-power transmission broadcast without excessively attenuating the signals of the high-power transmission broadcast group. It can be improved. That is, it is possible to effectively prevent a reception failure due to an adjacent channel wave in an overcrowded frequency usage situation while having a simple and inexpensive configuration.

  The base attenuation adjustment circuit can be configured as a high / low band π-type filter circuit having a pair of attenuation adjustment capacitors provided so as to branch to the ground side on the front side and the rear side of the main circuit. Such a high-low-pass π-type filter circuit can independently and easily adjust the base attenuation amount of each of the low-frequency and high-frequency stop bands according to the capacitance setting value of the attenuation adjustment capacitor.

  Which of the first attenuation pole derived from the series resonance attenuation peak of the trap circuit and the second attenuation pole derived from the parallel resonance attenuation peak of the main circuit is the high-frequency attenuation pole, and which is the low-frequency attenuation pole? This can be freely changed according to which one of the capacitor and the inductor is selected as each series resonance coupling element of the main circuit and the trap circuit. Specifically, when each series resonance coupling element of the main circuit and the trap circuit is configured by a capacitor, the first attenuation pole becomes a low-frequency attenuation pole, and the second attenuation pole becomes a high-frequency attenuation pole. Further, when each series resonance coupling element of the main circuit and the trap circuit is configured by an inductor, the first attenuation pole becomes a high-frequency attenuation pole, and the second attenuation pole becomes a low-frequency attenuation pole.

  That is, when each series resonant coupling element of the main circuit and the trap circuit is configured by a capacitor, the first attenuation pole based on the main circuit is located on the high frequency side based on the main parallel resonance circuit, and the attenuation peak of the first attenuation pole is The width is formed to be narrower than the attenuation peak width of the second attenuation pole. If there is a desired frequency band to be blocked (or suppressed) immediately adjacent to the low frequency side of the desired frequency band, the first attenuation pole with a narrow peak width suitable for the separation of the adjacent frequency band is the low frequency side. It can be said that the series resonant coupling element is preferably composed of a capacitor as shown in FIG. The attenuation peak width can be quantified by the peak half-value width when the pass curve of the stop band adjacent to the attenuation peak is regarded as a baseline. If a dump resistor is inserted in parallel with the series resonant coupling element, the attenuation depth of the first attenuation pole can be reduced according to the value of the dump resistor.

  In particular, the signal of the large power transmission broadcast group adjacent to the low band side of the pass band, the broadcast reception quality is sufficiently secured, and the adverse effect on the signal of the low power transmission broadcast that should pass through the pass band is sufficiently reduced, To moderately attenuate, adjust the base attenuation adjustment circuit so that the base attenuation of the stopband adjacent to the high band side of the passband is larger than the base attenuation of the stopband adjacent to the low band side. It is desirable to keep it. For example, when the above-described high / low-band π-type filter circuit is used as the base attenuation adjustment circuit, the base attenuation in the low-band stop band is determined by the capacitance setting value of the capacitor for attenuation adjustment on the front stage side (input side) of the main circuit. The amount of attenuation can be adjusted, and the base attenuation of the high-frequency stop band can be adjusted by the capacitance setting value of the capacitor for attenuation adjustment on the rear stage (output side) (in this case, the larger the capacitance setting value, The base attenuation also increases.)

  As an application in which the above aspect is particularly suitable, a current terrestrial digital television broadcast using the UHF band in Japan can be exemplified. Specifically, a terrestrial digital television regional broadcast channel having a transmission power level lower than that of the wide-area broadcast channel sequence may be set adjacent to the high frequency side of the terrestrial digital television wide-area broadcast channel sequence. The higher power side of the terrestrial digital television regional broadcast channel has a transmission power level higher than that of the terrestrial digital television regional broadcast channel, with a wider frequency band between channels than the terrestrial digital television wide-area broadcast channel series side. A terrestrial analog broadcast channel series having a large is set. In this case, the polarized bandpass filter of the present invention sets its passband to match the frequency band of the terrestrial digital TV regional broadcast channel, and the low-frequency stopband is the terrestrial digital TV wideband broadcast channel series. By setting the high side stopband to match the terrestrial analog broadcast channel sequence frequency band, the terrestrial digital TV broadcast signals received from the terrestrial digital television regional broadcast channel can be received. It is possible to effectively suppress the influence of nonlinear distortion caused by the high reception power of the television wide-area broadcast channel sequence and the terrestrial analog broadcast channel sequence, and the video quality of the regional broadcast channel can be improved.

  As described above, digital broadcasting has a characteristic that the video quality deteriorates sharply at a certain threshold as the C / N ratio of the received signal deteriorates, and the reception level extends over a wide band while ensuring the video quality. It is necessary to attenuate it flatly. In other words, only the digital wide-area broadcast channel that is adjacent to the terrestrial digital television regional broadcast channel on the digital side (that is, at a low frequency side) (at a narrower interval than analog broadcast) is sharply attenuated, and further to the low-frequency side. In order to ensure a flat reception level that does not hinder viewing, continuous digital wide-area broadcast channels have a first attenuation pole located in the frequency band of the channel adjacent to the low frequency side of the terrestrial digital TV regional broadcast channel. It is desirable. On the other hand, in analog broadcasting, the effect of video quality degradation due to a decrease in the received signal level is much more gradual than digital broadcasting, and from the viewpoint of giving priority to the attenuation of the channel adjacent to the high frequency side of the desired passage channel. It is desirable to adjust the position of each attenuation pole so that the second attenuation pole (broader) is located in the frequency band of the adjacent channel closest to the high frequency side of the terrestrial digital TV regional broadcasting channel. . In this case, the attenuation depth of the first attenuation pole is preferably set to be smaller than the attenuation depth of the second attenuation pole from the viewpoint of minimizing the amount of attenuation presented to the reception signal of the adjacent wide area digital broadcast. .

  Moreover, it is preferable that the attenuation level of the low-frequency stop band is 12 dB or more and 18 dB or less. If the attenuation level of the low-frequency stop band is less than 12 dB, the effect of reducing the influence of nonlinear distortion from the terrestrial digital television wide-area broadcast channel sequence is insufficient, and if it exceeds 18 dB, the received signal level of the wide-area broadcast channel is insufficient. The video quality of the channel cannot be ensured. The attenuation level of the high-frequency stop band is 1 dB or more larger than the attenuation level of the low-frequency stop band in the range of 16 dB to 20 dB so that the influence of nonlinear distortion due to the analog broadcast channel radio wave can be sufficiently reduced. It is desirable to set it. On the other hand, it is desirable that the pass loss in the pass band is 5 dB or less in order to ensure the received video quality of the terrestrial digital television regional broadcast channel.

  On the other hand, when each series resonant coupling element of the main circuit and the trap circuit is configured by an inductor, the first attenuation pole based on the main circuit is located on the high frequency side with respect to the second attenuation pole based on the main parallel resonance circuit, and The attenuation peak width of one attenuation pole is formed to be narrower than the attenuation peak width of the second attenuation pole. If there is a desired frequency band to be blocked (or suppressed) immediately adjacent to the high frequency side of the desired frequency band, the first attenuation pole with a narrow peak width suitable for separation of the adjacent frequency band is the high frequency side. It can be said that it is preferable that the series resonant coupling element is composed of an inductor as shown in FIG.

  In order to reduce the attenuation depth of the second attenuation pole, it is desirable to provide a dump resistor so as to be inserted in parallel with the main circuit on the signal transmission path.

  Next, in the present invention, the high-band end side or the low-band end side of the pass band is arranged in series with the main resonance capacitor and in parallel with the dielectric resonator in the main parallel column resonance unit. A distributed constant line portion for steepening the pass characteristic can be provided. Thereby, a pass band having sharper pass characteristics can be formed.

  The base attenuation adjustment circuit can be configured to have a distributed constant line portion connected in series with an attenuation adjustment capacitor. By connecting such distributed constant lines in parallel to the main circuit, the slope between the series resonance point and the parallel resonance point shown in FIG. 3 can be made steeper.

  In this case, as the dielectric resonator incorporated in the main parallel resonant circuit, a dielectric housing whose surface is covered with a metal coating layer that is conductively connected to the input side of the signal transmission path can be used. In addition, a dielectric resonator having a metal coating layer creates a predetermined gap between the mounting surface of the substrate on which the components of the polarized bandpass filter are mounted and covered with the ground conductor foil. The metal cover layer can be conductively connected to the ground conductor foil through the attenuation adjusting capacitor. Thus, the distributed constant line portion can be formed by the metal coating layer and the ground conductor foil, and the pass characteristics of the band-pass filter can be further steepened.

  A plurality of main circuits can be cascade-connected on the signal transmission path. By cascading the main parallel resonant circuits, the end shape of the passband can be made steeper.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a circuit configuration example of a polarized bandpass filter of the present invention. FIG. 2 shows typical measurement examples of the transmission characteristics (upper) and reflection characteristics (lower) on different frequency scales. This polarized bandpass filter 1 is for UHF television broadcast reception, and has a first attenuation pole PP and a second attenuation pole SP at both ends of the passband PB as shown in FIG. As shown in FIG. 1, the circuit includes a signal transmission path 86 having one end serving as an input unit PT1 and the other end serving as PT2, a main circuit A, a trap circuit B, and a base attenuation adjustment circuit C.

  In the main circuit A, as shown in FIG. 3, the main dielectric resonator CV1 and the main resonance capacitor VC2 forming an inductor on the signal transmission line 86 are coupled in parallel resonance to form a second attenuation pole SP (FIG. 17). And a capacitor (series resonance coupling element) C2 coupled in series resonance with the main parallel resonance circuit, and corresponding to the first attenuation pole PP (FIG. 2). And a main series resonance part having a series resonance pass peak at a position (more precisely, a position shifted to a higher frequency range of 1 to 4 MHz than the first attenuation pole PP). The position of the second attenuation pole SP can be variably set according to the capacitance of the main resonance capacitor VC2 formed of a trimmer capacitor.

  Further, as shown in FIG. 4, the trap circuit B is provided so as to branch from the signal transmission path 86 to the ground side, and the parallel dielectric coupling capacitor C1 and the parallel resonant coupling capacitor VC1 that form the inductor are connected in parallel. And a capacitor C1 that forms a series resonance coupling element that is in series resonance coupling with the trap parallel resonance portion, and a position adjacent to the series resonance passing peak of the main series resonance portion (more precisely, A series resonance attenuation peak for forming the first attenuation pole PP (FIG. 2) is generated at a position shifted to a lower frequency range of 1 to 4 MHz than the series resonance point of the main series resonance unit. The position of the first attenuation pole PP can be variably set according to the capacitance of the parallel resonant coupling capacitor VC1 configured by a trimmer capacitor. A dump resistor R2 for reducing the attenuation depth of the second attenuation pole SP is provided so as to be inserted in parallel with the main circuit A on the signal transmission path 86.

  The base attenuation adjustment circuit C is for adjusting the base attenuation of the stop bands LEB and HEB adjacent to the low band side and the high band side of the pass band PB. As shown in FIG. Attenuation adjustment capacitors C3 and C4 are provided so as to branch from 86 to the ground side. The base attenuation adjustment circuit C is a high / low-pass π-type filter circuit having a pair of attenuation adjustment capacitors C3 and C4 provided so as to branch to the ground side on the front side and the rear side of the main circuit A, respectively. .

  As shown in FIG. 7, the polarized bandpass filter 1 is configured as a filter built-in type cable connector unit that is used by being mounted on an indoor cable for television reception. A substrate 70 on which each component is mounted is assembled, and the outside thereof is covered with a cylindrical cover 2. The basic configuration of the cable connector unit is known from Patent Document 1 and the like, and detailed description thereof is omitted. Like the other circuit diagrams of the present invention, the circuit diagram of FIG. 1 is a simulation software for evaluating filter characteristics described later (a high-frequency / microwave EDA tool manufactured by MEL, Inc .: S-NAP / Pro). The circuit constants of each component are shown in FIG. 1 as input set values for performing simulation.

  For capacitors (C: C1, C2, VC1, VC2,..., VC is a variable capacitor (in this case, a trimmer capacitor)), the capacitance value is expressed in unit F and the Q value (target frequency). F is a unit Hz) (for example, “1p” indicates that the capacitance value is 1 pF). As for the resistance (R: R1,...), The value of the direct current electric resistance is shown in the unit Ω. With respect to the dielectric resonator (CV: CV1, CV2), the value of the resonance frequency fs is in units of Hz (for example, “575 MEG” indicates that the resonance frequency fs is 575 MHz). , Together with the Q value. Er is a relative dielectric constant. Further, d is the cross-sectional side length of the dielectric resonator having a square cross section (unit: mm), and a is the inner diameter of the cylindrical cavity of the dielectric resonator (unit mm). Although not shown in FIG. 1, the inductance value of the inductors (L: L1, L2) is in units of H, and the distributed constant line portions (MSL, MSL1, MSL2) are of line length (L: La, Lb) is expressed in units of mm, and the characteristic impedance Z (: Za, Zb,...) Is expressed in units of Ω. A is the line attenuation (unit: dB / m).

  In the polarized bandpass filter 1 according to the present invention, the basic shape of the passband PB is determined by the main circuit A and the trap circuit B, and the main parallel resonance section in which the dielectric resonator having a large Q value is incorporated. The main series resonance part having the series resonance coupling element C2 made of a capacitor or an inductor is directly connected. As shown in FIG. 3 (simulation: pass characteristic (thick line), reflection characteristic (thin line)), the same applies hereinafter), the pass characteristic is the first that forms either the high-frequency stop band HEB or the low-frequency stop band HEB. After gradually increasing from the base level toward the local maximum derived from the series resonance point to form a series resonance passing peak, it rapidly decreases toward the parallel resonance point level forming the second attenuation pole SP, By gradually returning toward the second base level that is the other of the side and the low band side, a parallel resonance attenuation peak that is paired with the series resonance passing peak is formed. Then, by adding the trap circuit B of FIG. 4 that generates a series resonance attenuation peak at a position adjacent to the series resonance pass peak, as shown in FIG. 5 (simulation), both sides have steep attenuation characteristics. A narrow and deep first attenuation pole PP peculiar to the trap circuit B is formed. When the band of the selected desired channel for low power transmission is adjusted to the pass band PB as described above, the attenuation peak forming the first attenuation pole PP indicates the signal of the selected desired channel as the first attenuation pole PP. The signal can be passed while being pinpointed from the signal of the large power transmission channel adjacent to the side.

  On the other hand, as shown in FIG. 1, the polarized bandpass filter 1 is provided with a base attenuation adjustment circuit C configured as a high and low band π filter circuit. As shown in FIG. 6 (simulation), by adding a high and low band π-type filter circuit, each of the low band side and high band side stop bands according to the capacitance setting values of the attenuation adjustment capacitors C3 and C4. The base attenuation of LEB and HEB can be adjusted independently and easily.

  Here, the series resonance coupling element of the main circuit and the trap circuit is configured by capacitors C2 and C1, and the first attenuation pole PP based on the main circuit A is lower than the second attenuation pole SP based on the main parallel resonance circuit. On the band side, the attenuation peak width is narrower than the attenuation peak width of the second attenuation pole SP. For example, for the signals of the large power transmission broadcast group adjacent to the low frequency side of the pass band PB, the broadcast reception quality is sufficiently secured, and the adverse effect on the signals of the low power transmission broadcast that should pass through the pass band PB is sufficiently reduced. Consider moderate attenuation. In this case, the base attenuation adjustment circuit C is adjusted so that the base attenuation of the stop band HEB adjacent to the high band side of the pass band PB is larger than the base attenuation of the stop band LEB adjacent to the low band side. The Specifically, in the base attenuation adjustment circuit C composed of a high and low-pass π-type filter circuit, the low-frequency side stop band LEB is determined by the capacitance setting value of the attenuation adjustment capacitor C3 on the front stage side (input side) of the main circuit A. Can be adjusted. Further, the base attenuation amount of the high-frequency stop band HEB can be adjusted by the capacitance setting value of the attenuation adjustment capacitor C4 on the downstream side (output side) (the larger the capacitance setting value, the larger the base attenuation amount). Become).

  In the circuit of FIG. 1, in order to reduce the attenuation depth of the second attenuation pole SP, a dump resistor R1 is inserted so as to be inserted in parallel with the main circuit A on the signal transmission path 86. In this case, as shown in FIG. 8, by moving the attenuation adjustment capacitor C3 on the front stage side of the base attenuation adjustment circuit C to the front stage side of the trap circuit, the pass characteristics and reflection characteristics of the filter can be further improved. Can do. In addition, the measurement example of the transmission characteristic and reflection characteristic in this case is shown together.

  Further, FIG. 9 is a circuit diagram of FIG. 8, in which the high frequency band of the passband PB is connected in series with the main resonant capacitor VC2 in the main parallel resonator and in parallel with the first dielectric resonator CV2. An example is shown in which a distributed constant line portion MSL2 for steepening the pass characteristic on the end side or the low band end side is provided. Thereby, the pass band PB having sharper pass characteristics can be formed. In FIG. 9, the transmission characteristic (thick line) and reflection characteristic (thin line) are compared with the case where the distributed constant line portion MSL2 is present (solid line) and the case where it is not the same (dashed line) at different frequency scales. Show.

  10 and 11 show examples of the formation of the distributed constant line portion MSL2 on the substrate 70. As shown in FIG. 11, the line pattern LP is formed on the first surface of the substrate 70, as shown in FIG. Thus, by forming the surface conductor MP2 at a corresponding position on the second surface of the substrate 70, the distributed constant line portion is formed as a microstrip line.

  For example, as shown in FIG. 12, a terrestrial digital television regional broadcast channel having a transmission power level lower than those of the wide-area broadcast channel sequence on the high frequency side of the terrestrial digital television wide-area broadcast channel sequence (here, U13 to U22ch). Consider a case where (U23ch) is set adjacently. The higher frequency side of the terrestrial digital TV regional broadcast channel is separated from the wider frequency band between channels than the terrestrial digital TV wide-area broadcast channel sequence side (here, U24ch is left empty) A terrestrial analog broadcast channel series (U25ch, U35ch) having a transmission power level larger than that of the terrestrial digital television regional broadcast channel is set.

  The polarized bandpass filter 1 of FIG. 1 (or FIG. 5) sets its passband PB to match the frequency band of the terrestrial digital television regional broadcast channel, and the low-band stopband LEB is terrestrial digital. It is set so as to coincide with the frequency band of the television wide-area broadcast channel sequence, and is set so that the high-side stop band HEB coincides with the terrestrial analog broadcast channel sequence frequency band. As a result, non-linearity caused by the high received power of the terrestrial digital television wide-area broadcast channel sequence (U13ch to U22ch) and the terrestrial analog broadcast channel sequence (U25ch, U35ch) with respect to the reception signal of the terrestrial digital television regional broadcast channel (U23ch). The effect of distortion can be effectively suppressed, and the video quality of the regional broadcast channel can be improved.

  FIG. 13 shows each circuit so that the first attenuation pole PP is positioned in the frequency band of the blocking channel (U22ch) adjacent to the low frequency side of the terrestrial digital television regional broadcasting channel (U23ch) in the circuit of FIG. This is an example in which constants are optimized. Digital broadcasting has a characteristic that the video quality sharply deteriorates at a certain threshold as the C / N ratio of the received signal deteriorates, and the reception level is flatly attenuated over a wide band while ensuring the video quality. There is a need. On the other hand, in analog broadcasting, the effect of video quality degradation due to a decrease in the received signal level is much more gradual than in digital broadcasting, and the attenuation of the channel adjacent to the high frequency side of the desired channel may be prioritized. Is possible. By performing the setting as shown in FIG. 13, only the adjacent digital wide-area broadcast channel (U22ch) is sharpened (at a narrower interval than analog broadcast) on the low-frequency side with respect to the terrestrial digital television regional broadcast channel (U23ch). It can be seen that the digital wide-area broadcast channels (U13ch to U21ch) that are attenuated and continue to the lower frequency side can ensure a flat reception level that does not hinder viewing. The attenuation level of the low-frequency stopband LEB is 12 dB or more and 18 dB or less, and the attenuation level of the high-frequency stopband HEB is within the range of 16 dB or more and 20 dB or less than the attenuation level of the low-frequency stopband LEB. It is set larger by 1 dB or more. Furthermore, the passage loss in the passband PB is set to 5 dB or less.

  An experiment for confirming the effect when the polarized band-pass filter having the circuit configuration of FIG. 13 is applied to the reception of the terrestrial digital television regional broadcasting channel (U23ch) and its surroundings as described above is as follows. I did it. FIG. 14 is a block diagram of the system used for the experiment. First, radio waves of a terrestrial digital television wide-area broadcast channel (U13, 18-22ch) were received via a commercially available UHF antenna and input to a second mixer via a digital television head end and a first variable attenuator. Also, a simulated signal assuming a terrestrial digital television regional broadcast channel (U23ch) was generated by a digital television signal generator (LG3802) and input to the second mixer. Furthermore, a simulated signal assuming a terrestrial analog television broadcast channel (U25ch, U35ch) is input to the first mixer through the attenuator (15 dB) for the former and directly to the first mixer for the latter, and the mixed output is The signal was input to the second mixer via the second variable attenuator. The input signal level of each channel was set to each value shown in FIG.

  Then, the output of the second mixer is input to a digital signal analyzer (Anritus, MS8901A) via a home booster via a cable provided with the polarized bandpass filter of the present invention shown in FIG. The modulation error rate MER (modulation method is 64QAM (quadrature amplitude modulation)) and the reception C / N ratio of U21ch, U22ch (wide area broadcast channel, 74 dB) and U23ch (regional broadcast channel, 44 dB) were measured. For comparison, in place of the polarized bandpass filter of the present invention, a commercially available band-eliminated filter (BEF) and highpass filter (HPF) showing the pass / reflection characteristics shown in FIG. The same measurement was also performed when no was used. The results are shown in Table 1.

  First, looking at (1) where no filter is used, the modulation error rate and C / N ratio of the digital regional broadcast channel (U23ch) are more than 15 dB wider than the digital wideband broadcast channels U21ch and U22ch. I know that there is. This means that the influence of nonlinear distortion acting in a superimposed manner from a plurality of digital wide-area broadcast channels on the low frequency side is great in addition to the signal state of the regional broadcast channel. In general, the reception limit of a digital television in the C / N ratio is said to be 20.1 dB, whereas the C / N ratio of U23ch is greatly reduced to 14.9, which is very normal reception. It turns out to be difficult.

  On the other hand, when a filter is used, the C / N ratio of U23ch is certainly improved for (2) and (3) using a commercially available band-eliminated filter (BEF) and high-pass filter (HPF). However, it does not exceed the reception limit of 20.1 dB. On the other hand, in (2) using the filter of the present invention, it can be seen that the C / N ratio of U23ch greatly exceeds the reception limit and has been raised to a level at which it can be received without problems.

Hereinafter, various modifications of the polarized bandpass filter of the present invention will be described.
In FIG. 16, in the circuit of FIG. 13, each circuit constant is optimized so that the high-frequency side base attenuation amount approaches 1 dB with respect to the low-frequency side base attenuation amount (particularly, the attenuation adjustment capacitor C4 is set to zero). Example). Adjacent channels (U22ch, U24ch) on both sides of the passage channel (U23ch) can be blocked.

  In FIG. 17, a dump resistor R1 can be inserted in parallel with the trap resonance capacitor C1 in the trap circuit. As shown in FIG. 18, by connecting the dump resistor R1, the attenuation depth of the first attenuation pole PP can be reduced according to the resistance value.

  Further, as shown in FIG. 19, the series resonant coupling elements of the main circuit and the trap circuit can be configured by inductors L1 and L2. In this case, the first attenuation pole PP based on the main circuit has a shape in which the attenuation peak width is narrower than the attenuation peak width of the second attenuation pole SP on the higher frequency side than the second attenuation pole SP based on the main parallel resonance circuit. Formed with. Since the first attenuation pole PP having a narrow peak width suitable for the separation of the adjacent frequency band appears on the high frequency side, there is a desired frequency band to be blocked (or suppressed) adjacent to the high frequency side of the desired frequency band. It is suitable for the case.

  Next, in the circuit configuration of FIG. 20, on the signal transmission path 86, the first main circuit including the dielectric resonator CV3, the main resonance capacitor VC1, and the capacitor C1 forming a series resonance coupling element is also used. The capacitor CV2, the main resonance capacitor VC2, and the second main circuit including the capacitor C2 forming the series resonance coupling element are cascade-connected. The base attenuation adjustment circuit C includes three attenuation adjustment capacitors C11, C12, and C3. Of these, the attenuation adjustment capacitors C11 and C12 are provided with distributed constant line portions MSL3 and MSL4 that are respectively connected in series. It has been. The trap circuit includes a trap resonance capacitor C1, a trap dielectric resonator CV1, and a parallel resonance coupling capacitor C4. The inductor L1 in the subsequent stage of the second main circuit is an equivalent inductance derived from the lead wire length of the capacitor C2, and returns to the previous stage of the first main circuit from the subsequent stage of the inductor L1, so A parallel resistor R1 is provided for forming the attenuation inhibition zone HEB.

  As shown in FIG. 21A, the dielectric resonator incorporated in the main parallel resonant circuit has a dielectric housing surface covered with a metal coating layer MF that is conductively connected to the input side of each signal transmission path 86. used. In addition, dielectric resonators CV2 and CV3 having a metal coating layer MF are mounted on the mounting surface of the substrate on which the components of the polarized bandpass filter 1 are mounted and covered with the ground conductor foil 90, and the mounting surface. It is mounted with a predetermined gap h between them. The metal coating layer MF is conductively connected to the ground conductor foil 90 via the attenuation adjustment capacitor C12. As a result, the distributed constant line portions MSL3 and MSL4 are formed by the metal coating layer MF and the ground conductor foil 90. FIG. 21B shows an equivalent circuit of the mounting circuit of FIG. 21A.

  FIG. 22 shows measurement examples of the transmission characteristic (upper) and the reflection characteristic (lower) on different frequency scales. It can be seen that the end shape of the passband PB can be made steeper by providing the two main circuits in cascade and providing the above-described fractional line portions MSL3 and MSL4. Note that the high-frequency base attenuation and the low-frequency base attenuation can be adjusted by the capacitance of the attenuation adjustment capacitor C12.

The figure which shows the circuit structural example of the polarized bandpass filter of this invention. The figure which shows the typical measurement example of the transmission characteristic (upper) and reflection characteristic (lower) in a different frequency scale. The simulation figure which shows the passage / reflection characteristic of a main circuit. The simulation figure which shows the passage / reflection characteristic of a trap circuit. The simulation figure which shows the passage / reflection characteristic at the time of combining a main circuit and a trap circuit. The simulation figure which shows the passage / reflection characteristic at the time of adding a base attenuation amount adjustment circuit further. The perspective view which shows the example at the time of comprising as a filter built-in type cable connector unit in an exploded state. An example of actual measurement of pass characteristics and reflection characteristics when the attenuation adjustment capacitor on the front stage side of the base attenuation adjustment circuit is moved to the front stage side of the trap circuit. The figure which shows the circuit at the time of providing the distributed constant line part MSL2 in the main series resonance part, and the simulation result of the passage / reflection characteristic. The board | substrate pattern figure (surface side) which shows the example of formation of a distributed constant track part. The pattern figure (back side) of the board | substrate which shows the example of formation of a distributed constant track part. The figure which shows an example of the channel allocation condition of terrestrial television broadcasting. Each circuit constant is optimized so that the first attenuation pole is located in the frequency band of the blocking channel (U22ch) adjacent to the low frequency side of the terrestrial digital television regional broadcasting channel (U23ch) in the circuit of FIG. The figure which shows an example. The block diagram of the system used for experiment. The characteristic view of the commercially available band elimination filter (BEF) and high pass filter (HPF) used for experiment. FIG. 14 is a diagram illustrating an example in which, in the circuit of FIG. 13, the high-frequency side base attenuation amount is approximated to a 1 dB difference with respect to the low-frequency side base attenuation amount by changing each circuit constant. The figure which shows the example which inserted the dump resistor in parallel with the coupling capacitor in the trap circuit. The actual measurement figure which shows the transmission / reflection characteristic. The figure which shows the example which comprised the series resonance coupling element of the main series resonance part with the inductor. The figure which shows the structural example which cascade-connected two main circuits. The perspective view which shows the component mounting state to the board | substrate of the circuit of FIG. The equivalent circuit schematic of FIG. 21A. FIG. 21 is an actual measurement diagram showing pass / reflection characteristics of the circuit of FIG. 20.

Explanation of symbols

1 Polarized Band Pass Filter 86 Signal Transmission Line A Main Circuit CV1 Main Dielectric Resonator VC2 Resonant Capacitor C2, L1 Series Resonant Coupling Element R2 Dump Resistor MSL2 Distributed Constant Line Section B Trap Circuit CV1 Trapping Dielectric Resonator C1 Trap Resonant capacitor VC1 Parallel resonant coupling capacitor L2 Series inductor R1 Dump resistor C Base attenuation adjustment circuit C3, C4 Attenuation adjustment capacitor MSL3, MSL4 Distributed constant line part PB Passband PP First attenuation pole SP Second attenuation pole

Claims (13)

A polarized bandpass filter having a first attenuation pole and a second attenuation pole at both ends of the passband,
A signal transmission line in which one end is an input unit and the other end is an output unit;
A main dielectric resonator that forms an inductor on the signal transmission line and a main resonance capacitor are coupled in parallel resonance, and a main parallel resonance unit that generates a parallel resonance attenuation peak for forming the second attenuation pole, and the main parallel resonance unit a main circuit having a main series resonance portion having a series resonance passage peak at a position corresponding to the first attenuation pole and has a Capacity data or Ranaru series resonant coupling element resonant circuit and the series resonant coupling,
A trap parallel resonance part, which is provided so as to branch from the signal transmission line to the ground side, and in which a trap dielectric resonator forming an inductor and a parallel resonance coupling capacitor are coupled in parallel resonance, and the trap parallel resonance part in series and has a Capacity data or Ranaru series resonant coupling element resonant coupling, causing a series resonance damping peak for forming the first attenuation pole at a position adjacent to said series resonant passage peak of the main series resonance portion trap Circuit,
A base attenuation adjustment for adjusting the base attenuation of the stop band adjacent to the low band side and the high band side of the pass band, having an attenuation adjustment capacitor provided so as to branch from the signal transmission path to the ground side With circuit ,
The polarized band pass filter according to claim 1 , wherein a dump resistor is inserted in parallel with the series resonant coupling element in the trap circuit . A polarized bandpass filter having a first attenuation pole and a second attenuation pole at both ends of the passband,
A signal transmission line in which one end is an input unit and the other end is an output unit;
A main dielectric resonator that forms an inductor on the signal transmission line and a main resonance capacitor are coupled in parallel resonance, and a main parallel resonance unit that generates a parallel resonance attenuation peak for forming the second attenuation pole, and the main parallel resonance unit A main circuit having a series resonance coupling element including an inductor coupled in series resonance with the resonance circuit and having a main series resonance part having a series resonance passing peak at a position corresponding to the first attenuation pole;
A trap parallel resonance part, which is provided so as to branch from the signal transmission line to the ground side, and in which a trap dielectric resonator forming an inductor and a parallel resonance coupling capacitor are coupled in parallel resonance, and the trap parallel resonance part in series A trap circuit having a series resonant coupling element including a resonantly coupled inductor and generating a series resonant attenuation peak for forming the first attenuation pole at a position adjacent to the series resonant passing peak of the main series resonant unit; ,
A base attenuation adjustment for adjusting the base attenuation of the stop band adjacent to the low band side and the high band side of the pass band, having an attenuation adjustment capacitor provided so as to branch from the signal transmission path to the ground side With circuit,
The polarized band pass filter according to claim 1 , wherein a dump resistor is inserted in parallel with the series resonant coupling element in the trap circuit . 2. The base attenuation adjustment circuit is a high / low-pass π-type filter circuit having a pair of attenuation adjustment capacitors provided so as to branch to the ground side on the front side and the rear side of the main circuit, respectively. Alternatively, a polarized bandpass filter according to claim 2. The first attenuation pole based on the main circuit is configured such that the attenuation peak width is narrower than the attenuation peak width of the second attenuation pole on the lower side than the second attenuation pole based on the main parallel resonant circuit. The polarized bandpass filter according to claim 1, which is formed . 5. The base attenuation adjustment circuit adjusts the base attenuation of a stop band adjacent to the high band side of the pass band to be larger than the base attenuation of the stop band adjacent to the low band side. The described polarized bandpass filter. A terrestrial digital television regional broadcast channel having a transmission power level smaller than those of the wide-area broadcast channel series is set adjacent to the high frequency side of the terrestrial digital television wide-area broadcast channel sequence, A terrestrial analog broadcast channel sequence with a higher transmission power level than the terrestrial digital television regional broadcast channel is set on the high frequency side, with a wider frequency band between channels than the terrestrial digital television wide-area broadcast channel sequence side set. Being
The passband is set to coincide with the frequency band of the terrestrial digital television regional broadcast channel, the low band side stopband is set to coincide with the frequency band of the terrestrial digital television wideband broadcast channel series, The polarized bandpass filter according to any one of claims 1, 4, and 5, wherein a side stop band is set to coincide with the terrestrial analog broadcast channel sequence frequency band.   The first attenuation pole is located in a frequency band of a channel adjacent to the terrestrial digital television area broadcasting channel and adjacent to the low frequency side, and the second attenuation pole is also positioned in a frequency band of the channel adjacent to the high frequency side. The polarized bandpass filter according to claim 6, wherein the position of each attenuation pole is adjusted so that is positioned. Wherein the first attenuation pole based on prior Symbol main circuit located in the high frequency side relative to the second attenuation pole based on the main parallel resonant circuit, the attenuation attenuation peak width of the first attenuation pole of the second attenuation pole The polarized bandpass filter according to claim 2 , wherein the polarized bandpass filter is formed to be narrower than a peak width.   The dump resistor for reducing the attenuation depth of the second attenuation pole is provided so as to be inserted in parallel with the main circuit on the signal transmission line. The polarized bandpass filter according to item.   The pass characteristics on the high band end side or low band end side of the pass band are sharpened so that the main parallel resonance unit is in series with the main resonance capacitor and in parallel with the dielectric resonator. The polarized bandpass filter according to any one of claims 1 to 9, wherein a distributed constant line portion is provided. 3. The polarized bandpass filter according to claim 1, wherein the base attenuation adjustment circuit includes a distributed constant line portion connected in series with the attenuation adjustment capacitor. The dielectric resonator incorporated in the main parallel resonant circuit has a dielectric housing surface covered with a metal coating layer that is conductively connected to the input side of the signal transmission path,
The dielectric resonator having the metal coating layer is mounted on the mounting surface of the substrate on which the component parts of the polarized bandpass filter are mounted and covered with the ground conductor foil. And the metal coating layer is conductively connected to the ground conductor foil via the attenuation adjustment capacitor,
The polarized bandpass filter according to claim 11, wherein the metal coating layer and the ground conductor foil form the distributed constant line portion. A plurality of the main circuits are cascade-connected on the signal transmission path,
13. The polarized band-pass filter according to claim 12, wherein the base attenuation adjustment circuit includes a set of the attenuation adjustment capacitor and the distributed constant line section, each associated with each main parallel resonance circuit. .