JPH0747009Y2 - Interfering wave removal filter - Google Patents

Description

[Detailed Description of the Invention] (Industrial field of application) The present invention is intended to eliminate interference waves for removing interference waves from a strong electric field in a radio frequency band to a receiving device, particularly a television receiver, a satellite broadcasting receiver and the like. It is related to the filter for.

(Summary of the Invention) This invention relates to a filter for removing interference of a radio wave in a strong electric field region of a radio frequency band to a television or other radio receiving equipment. When the receiving feeder of the equipment to be disturbed is a coaxial cable. ,
In a form in which the filter is inserted in the coaxial cable, the coaxial cable is wound around a toroidal core to form a coil, and capacitors are provided at both ends of the coil, in particular, capacitors added in parallel between the outer conductors of the coaxial cables. .

By doing so, it is possible to efficiently remove this type of interfering wave generated as a so-called common mode with a filter having a relatively simple structure.

(Prior Art) In television reception in a strong electric field area near a radio frequency band radio station, an induced voltage is generated in a television reception feeder, which deteriorates the television image quality and generally appears as beat fringes. Since the induced interference wave occurs as so-called common mode interference between the outer conductor of the receiving feeder (usually a coaxial cable) and the ground, it is necessary to remove it.

Conventionally, as a method of removing the interfering waves induced in a strong electric field area such as near a radio broadcasting station, insert a lumped constant filter into the antenna terminal Insert a high frequency transformer into the antenna terminal Insert a noise filter into the power line Was taken.

Among them, the lumped constant filter has a large insertion loss, deteriorates the SWR (standing wave ratio), and has a problem that it is not effective against common mode interference. On the other hand, there are many problems that satellite interference reception interference filters are not currently on the market.

Further, the insertion of the high frequency transformer is effective for the common mode interference, but has the same drawback as the lumped constant filter for the other mode interference. Further, this type of removing means has a drawback that it cannot pass through when the power supply voltage is superposed on the feeder.

Further, the power supply noise filter has no effect on the interfering wave mixed from the antenna terminal.

(Problems to be solved by the invention) As described above, filters, transformers, etc. have been conventionally used to remove interference waves in the radio frequency band for television reception, etc. There wasn't.

Most of the disturbances in the strong electric field area that are currently attracting attention are so-called common-mode disturbances that are generated by the voltage induced between the outer conductor of the coaxial cable and the ground entering the equipment.

The conventionally used filter for removal has a configuration for removing normal mode interference, and since the ground side of the input / output terminals is common, it is not effective against common mode interference.

Further, the high-frequency transformer for removing the interference wave is effective against common-mode interference, but has a drawback that it cannot pass the power supply voltage.

Therefore, an object of the present invention is to provide a filter for removing an interference wave capable of passing a power supply voltage by efficiently removing an interference wave from a radio frequency band strong electric field to a receiving device such as a television signal with a relatively simple structure. It is what

(Means for Solving the Problem) In order to achieve this object, the interference wave removing filter of the present invention receives a received signal from a strong electric field of a radio frequency band through a first coaxial cable of a receiving antenna. A filter for removing an interfering wave inserted in the middle of the first coaxial cable to remove an interfering wave into the device, wherein the second coaxial cable is wound around a toroidal core, It is characterized in that a capacitor is added in parallel between respective outer conductors at both ends of the second coaxial cable which is a connection point with the first coaxial cable.

(Operation) According to the configuration of the filter of the present invention, it is possible to pass the power supply voltage by using the receiving coaxial cable itself as a coil, and use a material having a high magnetic permeability, such as ferrite, for the toroidal core. As a result, the number of turns of the coil can be reduced and the insertion loss with respect to the desired wave can be reduced.

In addition, since the outer conductor and the inner conductor function as notch filters for the interfering waves, the effect of removing them is great.

In addition, since a trimmer capacitor is connected in parallel to the used capacitor to make it a variable capacitance, it is possible to manufacture a filter for removing interference waves that is effective against interference waves of any frequency in the radio frequency band, and at a It can also be expected to be cheaper.

(Embodiment) The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram showing the basic constitution of the filter of the present invention, and the basic constitution is extremely simple as shown in FIG. That is, in a mode in which a received signal is fed from a receiving antenna of a radio frequency band strong electric field, for example, a receiving antenna of a television receiving apparatus through a coaxial cable, the input connector 4 and the output connector are provided in the middle of the coaxial cable. A toroidal core 1 made of a material having a high magnetic permeability such as ferrite is provided with a plug 5, a coil 2 of a coaxial cable wound a plurality of times around this core, and at both ends of the coil, between outer conductors at both ends thereof. The filter of the present invention is constructed by including a fixed capacitor 3 having a trimmer capacitor in parallel. However, the resonance circuit for the interfering wave is formed by the coil and the parallel capacitor to eliminate the common mode interference.

FIG. 2 shows a first embodiment in which the filter according to the present invention is applied to television reception, and FIG. 3 shows a second embodiment in which it is applied to satellite broadcast reception.

In the second illustrated configuration, the television receiving antenna 6
The feeder (coaxial cable) 7 from is connected to the input connector (eg FJ connector) 4 of the filter of the present invention, and the output connector 5
The filter according to the present invention is inserted between and. The filter is a toroidal core (T16-28-13) 1 and a coil (about 90μ) in which a coaxial cable (1.5C-QEV) is wound around the core 9 times.
H) 2 and a trimmer capacitor (50pF) on both ends of the coil.
max) in parallel with a fixed capacitor (220pF) 3. A feeder (coaxial cable) 8 is again led out from the output connector 5 of the filter, and this is connected to the antenna terminal 10 of the television receiver 9.

In this case, the target strong electric field radio station is a radio broadcasting station frequency of 1071 KHz and an output of 20 kW. "The stripes of the lick are mixed. This contamination can be removed by inserting the filter described above. In this case, the filter inserted between the television receiver 9 and the television receiving antenna 6 should be as close to the antenna terminal 10 of the television receiver 9 as possible.

Also, in the case of satellite broadcasting reception, the BS antenna 11, the BS converter 12, and the feeder (coaxial cable) 13 are connected to the input connector 4 of the filter of the present invention, and the same with the output connector 5 as shown in FIG. A filter for removing an interfering wave is inserted. The coaxial cable 14 is led out again from the output connector 5 of the filter, and this is the antenna terminal 16 of the BS tuner 15 for the television receiver 17.
Connected to. The feature of this second embodiment is that DC15V is transmitted from the BS tuner 15 to the BS converter 12 through the filter of the present invention.

The target interference wave of the interference wave elimination filter of the present invention has been described in this embodiment in the radio frequency band (for example, 1071 kHz), but the present invention is not limited to this, for example, about several tens of MH _2. The radio frequency band such as the short wave of is also included.

(Effects of the Invention) The following specific effects were confirmed by using the filter of the present invention as a countermeasure against interference waves as in the embodiments shown in FIGS. 2 and 3.

A good characteristic was obtained with an attenuation of the interference wave of about 35 dB and an insertion loss of about 0.5 to 2 dB for television and satellite broadcasting. In addition, the booster power supply voltage for television reception,
The power supply voltage for the satellite broadcasting reception antenna can also pass, and there was no problem in receiving both signals.

The received image quality was improved until no noticeable beat fringes were detected.

[Brief description of drawings]

FIG. 1 shows a basic block diagram of a filter for removing an interference wave according to the present invention, and FIGS. 2 and 3 show first and second embodiments applied to television reception and satellite broadcast reception, respectively. It is a figure. 1 ... Toroidal core, 2 ... Coaxial cable coil, 3 ... Capacitor, 4 ... Input plug, 5 ... Output plug, 6 ... Television receiving antenna 7,8 ... Coaxial cable feeder, 9 ... TV John receiver 10 …… Antenna terminal, 11 …… BS antenna 12 …… BS converter 13,14 …… Coaxial cable feeder 15 …… BS tuner, 16 …… Antenna terminal 17 …… TV receiver

Claims (1)

[Scope of utility model registration request] 1. A radio frequency band strong electric field is used to remove an interfering wave into a receiving device to which a received signal is fed via a first coaxial cable of a receiving antenna.
The interfering wave removing filter inserted in the middle of the coaxial cable, wherein the second coaxial cable is wound around a toroidal core, and the second coaxial cable becomes a connection point with the first coaxial cable. A filter for removing an interfering wave, which has a structure in which a capacitor is added in parallel between respective outer conductors at both ends of a coaxial cable.