JPH05299939A - Dual lnb - Google Patents

Abstract

PURPOSE:To provide the dual LNB reducing a leakage level of a local oscillation signal when no bias is applied to one high frequency amplifier circuit. CONSTITUTION:The LNB is provided with two high frequency amplifier circuits amplifying outputs of two coaxial waveguide converters 1a, 1b respectively. Any of the high frequency amplifier circuits is operated by giving a bias alternatively to the high frequency amplifier circuit. A printed circuit board 14 with a circuit section mounted thereon is contained in a case A. A separator 16 made of a conductive material to separate each section of the printed circuit board 14 is provided in the case A. An electric wire 20 whose one terminal connects to a bias supply point 19b of the high frequency amplifier circuit and whose other point is kept open is arranged in a section surrounded by an inner circumferential face and the separator 16 in the case A. The electric wire 20 has an insulation sheath and circumscribed in the inner circumferential face of the section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dual LNB which is used for satellite broadcasting and satellite communication and which can perform frequency conversion on reception signals of two types of radio waves and selectively output one reception signal. It is a thing.

[0002]

2. Description of the Related Art Conventionally, in satellite broadcasting and satellite communication, in order to effectively utilize frequencies, communication methods of transmitting different information by using radio waves of different polarization for radio waves of the same frequency have been used. For example, circularly polarized wave transmits different information between right-handed polarized wave and left-handed polarized wave, and linear polarized wave transmits different information between horizontal polarized wave and vertical polarized wave. Therefore, a dual LNB is used to separate the two types of polarized waves.

Dual LNB (Low Noise Block-down c
The received signal of each polarization received by the antenna is input to the onverter). The dual LNB performs frequency conversion so as to lower the frequency of the received signal, and alternatively outputs the frequency-converted received signal of each polarization. Specifically, for example, it has a configuration as shown in FIG. That is, a pair of coaxial waveguide converters 1a and 1b having different waveguides 2a and 2b for transmitting the respective polarized waves received by the antenna.
The received signals for the respective polarized waves output from the coaxial waveguide converters 1a and 1b are input to the high frequency amplifier circuits 4a and 4b via the terminals 3a and 3b, respectively, and are amplified. The received signals of both polarizations amplified by the high frequency amplification circuits 4a and 4b are amplified by the high frequency amplification circuit 6 through the combiner 5,
After the image band frequency is removed by the bandpass filter 7, the mixer 8 mixes the image with the local oscillation signal from the local oscillation circuit 9 to perform frequency conversion. That is, the mixer 8 and the local oscillation circuit 9 constitute frequency conversion means. The received signal after the frequency conversion is amplified by the intermediate frequency amplifier circuit 10 and output. Here, the high-frequency amplifier circuits 4a and 4b are selectively supplied with a bias through the selection circuit 11, and only one of them operates so that only one of the two types of received signals of polarized waves passes through the combiner 5. It is supposed to do. That is, one polarized wave is selected by the selection circuit 11.

By the way, in the circuit provided with this kind of frequency conversion means, it is inevitable that a part of the local oscillation signal from the local oscillation circuit 9 leaks to the input side and the output side. Considering the influence on the outside, it is desirable to reduce such leakage power as much as possible, and in particular, the leakage signal to the input side is radiated into the air via the antenna, so it is necessary to sufficiently suppress it.

This type of dual LNB uses a microstrip line, and it is known that the local oscillation signal leaks to the input side through the microstrip line and also to the input side by propagating in space. ing. Therefore, a local oscillator signal propagating in the space is suppressed by dividing the space into a plurality of spaces by providing a metal separator between the high frequency amplifier circuit 6, the bandpass filter 7, the mixer 8, and the local oscillator circuit 9. It is the current situation.

[0006]

By the way, one of the high-frequency amplifier circuits 4a and 4b operates as an alternative, and the other is not operated without power supply. It is generally known that the high-frequency amplifier circuits 4a and 4b have opposite signal transfer characteristics when operating and when not operating. Regarding the signal transmitted in the reverse direction from the output side to the input side, the signal is transmitted to the input side in the non-operating state as compared with the signal in the non-operating state, although the reflection is large and the signal is hardly transmitted to the input side. It will increase. Therefore, in the dual LNB that selects one of the above-mentioned two types of polarized waves, there arises a problem that the local oscillation signal leaks to the antenna through the inoperative high-frequency amplifier circuits 4a and 4b.

In order to avoid such a problem, it has been considered to provide a radio wave absorber or the like in the vicinity of the transmission line, but there arises a problem that the transmission characteristic of the high frequency signal is deteriorated. It is also considered that a filter is provided on the coaxial waveguide converters 1a and 1b or a circuit board to prevent the local oscillation signal from being transmitted in the opposite direction. For example, as shown in FIG. 4, in the coaxial waveguide converters 1a and 1b continuously provided in the peripheral portion of the case A, the coaxial waveguides 12a and 12b are inserted into the waveguides 2a and 2b. Adjusting screw 13a,
13b is inserted into the waveguide 2 of the adjusting screws 13a and 13b.
It is considered that the amount of insertion into a and 2b can be adjusted. In this configuration, the adjusting screws 13a and 13b function as so-called trap frequency adjusters and can adjust the center frequency of the local notch filter formed by the coaxial waveguide converters 1a and 1b. However, since the center frequency of the stop band and the like change greatly even if the insertion amount of the adjusting screws 13a and 13b slightly changes, high accuracy is required for adjusting the adjusting screws 13a and 13b, which makes the adjustment difficult. ..

An object of the present invention is to solve the above problems, and to provide a dual LNB capable of reducing the leakage level of a local oscillation signal in a state where a bias is not supplied to one of the high frequency amplifier circuits. Is what you are trying to do.

[0009]

According to the invention of claim 1, in order to achieve the above object, two coaxial waveguide converters,
Two high frequency amplifier circuits for amplifying the received signals output from the respective coaxial waveguide converters, and a selection circuit for operating one of the high frequency amplifier circuits by selectively biasing the high frequency amplifier circuits. And a frequency conversion circuit that performs frequency conversion on the reception signal amplified by the high frequency amplification circuit, and both coaxial waveguide converters are arranged in the peripheral part of the case of a conductive material and selected as the high frequency amplification circuit. A circuit board on which a circuit and a frequency conversion circuit are mounted is arranged in a case, and a linear conductive member having one end connected to a bias supply point of a high frequency amplifier circuit and the other end opened is arranged in the case. -ing

According to a second aspect of the invention, a separator made of a conductive material that divides the space in the case on the circuit board is disposed in the case, and the conductive member is an electric wire having an insulating coating. In one compartment surrounded by the inner peripheral surface and the separator, the electric wire is arranged so as to be inscribed in the peripheral surface of the compartment. In the invention of claim 3, the conductive member is a conductive pattern formed on a dielectric substrate.

[0011]

In the dual LNB, the local oscillation signal from the frequency conversion circuit may leak through the two coaxial waveguide converters, and the leakage level changes depending on the supply state of the bias to the high frequency amplification circuit. The leakage level from the coaxial waveguide converter is higher in one side than the other due to structural factors. Further, the high-frequency amplifier circuit has a higher leakage level when the bias is not supplied than when the bias is supplied. Therefore, the leakage level becomes maximum when the bias is not supplied to the high-frequency amplifier circuit corresponding to the coaxial waveguide converter having the larger leakage level. It is considered that if the maximum value of the leakage level can be reduced, the adjustment accuracy can be reduced even when a local notch filter having an adjusting screw or the like is provided.

Therefore, in the structure of claim 1, the cleaning conductive member having one end connected to the bias supply point of the high frequency amplifier circuit and the other end opened is provided in the case, thereby biasing the high frequency amplifier circuit. That is, the high-frequency impedance is increased in the state where C is not supplied, and the local oscillation signal reduces the reverse flow rate to the coaxial waveguide converter.

The structures of claims 2 and 3 are preferred embodiments of the conductive member.

[0014]

(Embodiment 1) The circuit configuration of this embodiment is similar to that described in the prior art. That is, as shown in FIG. 3, the output of an antenna such as a planar antenna is
It is input to the high frequency amplifier circuits 4a and 4b via the coaxial waveguide converters 1a and 1b provided with a and 2b. The high frequency amplifier circuits 4a and 4b include GaAs field effect transistors and H
The EMT is used, and is configured in the form of gate input, drain output, and source ground. Coaxial waveguide converter 1a, 1
b has coaxial probes 12a and 12b inserted into the respective waveguides 2a and 2b corresponding to the respective polarized waves, and the coaxial probe 12a and 12b has a circuit board 14 on which a circuit unit is mounted.
(See FIG. 1).

The two coaxial waveguide converters 1a and 1b are continuously formed on the peripheral portion of the case A made of a conductive material. The coaxial probes 12a and 12b are arranged in a direction orthogonal to each other from the inside to the outside of the case A.
Further, a recess 15 for housing the circuit board 14 is opened on the surface opposite to the opening surface of the waveguides 2a and 2b. A separator 16 made of a conductive material is disposed in the recess 15 to divide the recess 15 into a plurality of sections. The separator 16 is
It prevents unwanted signal transmission on the circuit board 14. An output connector 17, which is an output terminal of the circuit section, is provided at a position different from the recess 15. Here, the high frequency amplifier circuits 4a and 4b are arranged in the broken line portions 18a and 18b in FIG.

With this shape, the leakage level from the coaxial waveguide converter 1b is higher than the leakage level from the coaxial waveguide converter 1a. Therefore, one end of the electric wire 20 having an insulating coating is connected to the positive bias supply point 19b (the negative side is the bias supply point 19a) connected to the output part of the high-frequency amplifier circuit 4b corresponding to the coaxial waveguide converter 1b. To do. The other end of the electric wire 20 is open, and is arranged in a compartment surrounded by the inner peripheral surface of the case A and the separator 16 so as to surround the negative bias supply point 19a. Further, the electric wire 20 is inscribed on the inner peripheral surface of this section.

According to the above configuration, the high frequency impedance in the state where the bias is not supplied to the high frequency amplifier circuit 4b becomes higher than that in the case where the electric wire 20 is not provided, and the reverse flow rate of the local oscillation signal can be reduced. That is, the leakage level when the high frequency amplifier circuit 4b is not operating can be reduced. (Embodiment 2) In this embodiment, as shown in FIG.
Instead, a circular conductive pattern 22 having a partially open portion is formed on the dielectric substrate 21, and the bias supply point of the high frequency amplifier circuit 4b is connected to one end of the cutout portion of the conductive pattern 22. The board 21 may be formed as a continuous body of the circuit board 14. Other configurations are similar to those of the first embodiment.

In the above configuration, the electric wire 20 and the conductive pattern 22 are connected to the high frequency amplifier circuit 4b, but it goes without saying that they may be connected to the bias supply point of the high frequency amplifier circuit 4a.

[0019]

As described above, according to the present invention, since the linear conductive member having one end connected to the bias supply point of the high frequency amplifier circuit and the other end opened is provided in the case, the high frequency amplifier circuit is provided. There is an advantage that the high-frequency impedance can be increased in the state where the bias is not supplied to the local oscillation signal and the reverse flow rate of the local oscillation signal to the coaxial waveguide converter can be reduced. Further, since only the linear conductive member is provided, the cost is hardly affected.

[Brief description of drawings]

FIG. 1 is a front view of a waveguide of Example 1 as viewed from a closed surface side.

FIG. 2 is a front view of a main part of the second embodiment.

FIG. 3 is a block circuit diagram showing a dual LNB according to the present invention.

FIG. 4 is a front view showing a conventional example.

[Explanation of symbols]

 1a coaxial waveguide converter 1b coaxial waveguide converter 2a waveguide 2b waveguide 4a high frequency amplification circuit 4b high frequency amplification circuit 8 mixer 9 local oscillation circuit 11 selection circuit 16 separator 19a bias supply point 19b bias supply point 20 Wire 21 Board 22 Conductive pattern A Case

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 1, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art Conventionally, in satellite broadcasting and satellite communication, in order to effectively use frequencies, a communication method is used in which radio waves of different polarizations are used to transmit different information for radio waves of the same frequency band . .. For example, circularly polarized wave transmits different information between right-handed polarized wave and left-handed polarized wave, and linear polarized wave transmits different information between horizontal polarized wave and vertical polarized wave. Therefore, a dual LNB is used to separate the two types of polarized waves.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Therefore, in the structure of claim 1, a linear conductive member having one end connected to the bias supply point of the high-frequency amplifier circuit and the other end opened is provided in the case, whereby the high-frequency amplifier circuit is connected. The high-frequency impedance in the state where the bias is not supplied is increased, and the local oscillation signal reduces the reverse flow rate to the coaxial waveguide converter.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

According to the above configuration, the high frequency impedance in the state where the bias is not supplied to the high frequency amplifier circuit 4b becomes higher than that in the case where the electric wire 20 is not provided, and the reverse flow rate of the local oscillation signal can be reduced. That is, the leakage level when the high frequency amplifier circuit 4b is not operating can be reduced. (Embodiment 2) In this embodiment, as shown in FIG.
Instead, a circular conductive pattern 22 having a partially open portion is formed on the dielectric substrate 21, and the bias supply point of the high frequency amplifier circuit 4b is connected to one end of the cutout portion of the conductive pattern 22. The board 21 may be formed as a continuous body of the circuit board 14. Other configurations are similar to those of the first embodiment.

Claims (3)

[Claims] 1. Two coaxial waveguide converters and two amplifiers for amplifying received signals output from the respective coaxial waveguide converters.
Individual high-frequency amplifier circuits, a selection circuit that operates one of the high-frequency amplifier circuits by selectively biasing the high-frequency amplifier circuits, and a frequency converter that performs frequency conversion on the reception signal amplified by the high-frequency amplifier circuits. And a coaxial circuit, the both coaxial waveguide converters are arranged around the circumference of a case made of a conductive material, and a circuit board on which a high frequency amplification circuit, a selection circuit and a frequency conversion circuit are mounted is arranged in the case. A dual LNB, wherein a linear conductive member, one end of which is connected to a bias supply point of a high frequency amplifier circuit and the other end of which is open, is disposed in a case. 2. A separator made of a conductive material that divides a space in the case on the circuit board is arranged in the case.
The conductive member is an electric wire having an insulating coating, and in one compartment surrounded by the inner peripheral surface of the case and the separator, the electric wire is arranged so as to be inscribed on the peripheral surface of the compartment. The dual LNB according to claim 1, characterized in that 3. The dual LNB according to claim 1, wherein the conductive member is a conductive pattern formed on a dielectric substrate.