JPH06140814A - Microwave circuit - Google Patents

Abstract

PURPOSE:To prevent abnormal oscillation at a low temperature in the microwave circuit using an IC for microwave. CONSTITUTION:A chip capacitor 12 is inserted between the output terminal of a band filter 10 and the high frequency signal input terminal 1 of an IC 11 for microwave. The chip capacitor 12 reduces the reflection of the band filter 10 at a frequency for easily generating the abnormal oscillation with the loss component, and the abnormal oscillation can be prevented from occuring even when the gain is increased at the low temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LNB (Lo) for frequency conversion (down conversion) of a received signal which is connected to an antenna for receiving a signal from a communication satellite or a broadcasting satellite.
w Noise Block down converter
ter) and other microwave circuits.

[0002]

2. Description of the Related Art LNB for satellite broadcasting is the first market in which microwave circuits are used. As a conventional LNB circuit, as shown in the block diagram of FIG.
A high-frequency amplifier circuit 1 for amplifying a high-frequency signal (RF signal) from, a band-pass filter 2, a mixer circuit 3, a local oscillator 4, an intermediate frequency amplifier circuit 5, a power supply circuit 6, and an output section 7. , GaAs FET is used for high frequency circuits
A discrete circuit system using microwave active elements such as (gallium arsenide field effect transistor) was adopted.

However, in recent years, there has been an increasing interest in making microwave circuits into ICs for the purpose of downsizing circuits and improving reliability. Such a microwave IC has a MMIC (MonolIthc) because each circuit is formed on a GaAs substrate.
Microwave Integrated Cir
It is called a cut). In the case of IC integration, there is also a method of IC integration of all LNB microwave circuits, but considering the performance and cost aspects, the circuit part in which a high frequency amplifier circuit is added to the circuit part surrounded by the broken line frame A in FIG. It is practical to be integrated into an IC and is being sold by semiconductor manufacturers. FIG. 5 shows a microwave IC 1 including the MMIC.
1 shows an example of the configuration, and the microwave IC 11 includes a high frequency amplifier circuit 1 ', a mixer circuit 3', a local oscillator 4 ', and an intermediate frequency amplifier circuit 5'.

[0004]

By the way, since the LNB is premised on being used outdoors, it is necessary that the temperature is within the range of -30 ° C to + 50 ° C. However, in general, when a high-frequency amplifier circuit is composed of GaAs FETs or HEMTs, the gain increases at low temperatures and abnormal oscillation tends to occur easily. Also in the microwave IC 11 including the MMIC, the high frequency amplifier circuit 1 '
Is based on GaAs FET, and is no exception.

The present invention has been made in view of the above problems, and an object thereof is to prevent abnormal oscillation at a low temperature in a microwave circuit using a microwave IC. It is to provide a microwave circuit capable of.

[0006]

In order to achieve the above object, the invention as set forth in claim 1 is a micro-integration of a high-frequency amplifier circuit, a local oscillator circuit, a mixer circuit, and an intermediate-frequency amplifier circuit. In the microwave circuit, the wave IC, the input section of the microwave IC, and the output section of a bandpass filter having the signal frequency band of the high frequency amplifier circuit of the microwave IC as a pass band are connected to each other. An impedance element is inserted between the output section of the filter and the input section of the microwave IC.

A capacitor is used as the impedance element in the second aspect, a resistor is used as the impedance element in the third aspect, and an inductance element is used as the impedance element in the fourth aspect.

[0008]

According to the structure of the present invention, the loss of the impedance element makes it possible to reduce the reflection of the filter at the frequency at which abnormal oscillation is likely to occur. Therefore, abnormal oscillation occurs even if the gain increases at low temperature. Can be prevented. Especially when the oscillation is likely to occur at a frequency lower than the high frequency signal frequency band, it is effective to use a capacitor as an impedance element. Conversely, when the oscillation is likely to occur at a frequency higher than the high frequency signal frequency band, the inductance element is used as the impedance element. It is effective when used as. Furthermore, when a resistor is used, it is effective at all frequencies.

[0009]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 shows a wiring configuration of an embodiment used in an LNB connected to an antenna for receiving satellite broadcasting, in which a high frequency signal input from the antenna is amplified by a low noise high frequency amplifier circuit (not shown) configured by HEMT or the like. After that, the microwave IC is passed through a bandpass filter 10 having a high frequency signal band as a pass band.
11 is input. Reference numeral 14 denotes an input section of the bandpass filter 10.

The microwave IC 11 is called MMIC, and is composed of a high frequency amplifier circuit 1 ', a mixer circuit 3', a local oscillator 4'and an intermediate frequency amplifier circuit 5'as shown in FIG. In addition to the signal input terminal, the terminal connected to the external dielectric resonator 13, the intermediate frequency output terminal, and the positive and negative bias terminals, a grounding terminal connected to the ground pattern 15 is provided. A portion of the dielectric substrate 16 on which the dielectric resonator 13 and the microwave IC 11 are mounted is housed in a metal cavity (not shown).

The bandpass filter 10 has a direct current cut.
Therefore, the RF input terminal of the microwave IC 11 is directly
It does not have to be a flow blocking type, and the band filter 10
Power section and high frequency signal input terminal of the microwave IC 11
Is usually connected directly with a microstrip line
is there. However, in such a normal configuration, as described above,
Abnormality of microwave IC 11 when operating at low temperature
Oscillation occurs. The cause of this abnormal oscillation is the high frequency signal
S-parameter of the bandpass filter 10 connected to the input terminal
(S shown in FIG.₁₁, S _{twenty two}, S_{twenty one}, S₁₂However, for input / output
Since there is no tropism, S₁₁= S_{twenty two}, S_{twenty one}= S₁₂) Frequency characteristics
Is the point shown in FIG. That is, the target high-frequency signal
Inserted in the band (11.2 GHz to 12 GHz) RF
Input loss is small and matching is good, but outside the band
Shows the characteristic that almost no reflection is obtained without matching.
Because.

Especially when operated at -30 ° C., abnormal oscillation of a frequency lower than the high frequency signal can be confirmed. Therefore, in the configuration of the embodiment, the lower the frequency is, the higher the impedance is, and the chip capacitor 12 (0.5 to several pF) is used as the bandpass filter 1 as an impedance element exhibiting a high pass characteristic.
It is inserted between the output unit of 0 and the high frequency signal input terminal of the microwave IC 11.

Thus, in this embodiment, the reflection of the bandpass filter 10 at the frequency of the abnormal oscillation can be reduced by the loss of the chip capacitor 12, and as a result, the abnormal oscillation at a low temperature can be prevented. You can do it. Further, since there is no loss in the high frequency signal frequency band RF, the total gain is hardly affected and the NF (noise figure) is hardly deteriorated.

If the frequency of occurrence of abnormal oscillation differs in frequency, a chip resistor or an inductance element may be used instead of the chip capacitor 12. In the case of a chip resistor, assuming that there is only a real number component as the impedance, the loss is the resistance component at all frequencies, and it is possible to support all frequencies. A value of about several Ω is suitable.
In addition, since the inductance element has a low-pass characteristic, it is effective when oscillation easily occurs at a frequency higher than the high frequency signal frequency band RF.

[0015]

According to the invention of claim 1, a high-frequency amplifier circuit,
A microwave IC in which a local oscillator circuit, a mixer circuit, and an intermediate frequency amplifier circuit are integrated, and this microwave IC
A microwave circuit in which an input part of C and an output part of a bandpass filter having a signal frequency band of a high frequency amplifier circuit of a microwave IC as a pass band are connected to each other, wherein the output part of the bandpass filter and the microwave Since the impedance element is inserted between the input part of the IC for use, the loss of the impedance element can reduce the reflection of the filter at the frequency where abnormal oscillation easily occurs, and therefore the gain increases at low temperature. Also, it is possible to prevent abnormal oscillation from occurring, and further, there is an effect that the cost for the configuration as a countermeasure is small and the cost increase is small.

Since the capacitor is used as the impedance element, the present invention is effective when the oscillation is likely to occur at a frequency lower than the high frequency signal frequency band, and there is almost no decrease in gain particularly in the high frequency signal frequency band. NF
The effect is that there is almost no deterioration. When a resistor is used as in the invention of claim 3, it is effective at all frequencies, and when an inductance element is used as an impedance element as in the invention of claim 4, it is more effective than the high frequency signal frequency band. This is effective when oscillation is likely to occur at high frequencies.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing component mounting according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of S parameters of the band filter of the above.

FIG. 3 is a frequency characteristic diagram of the above bandpass filter.

FIG. 4 is a circuit block diagram of a conventional LNB.

FIG. 5 is a circuit block diagram of a microwave IC.

[Explanation of symbols]

 10 band filter 11 microwave IC 12 chip capacitor high frequency signal input terminal

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[Procedure amendment]

[Submission date] January 11, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

However, in recent years, there has been an increasing interest in making microwave circuits into ICs for the purpose of downsizing circuits and improving reliability. Such a microwave IC has a MMIC ( Monolithi
c Microwave Integrated Ci
rquit). When converting to IC, LNB
There is also a method of making all of the microwave circuits of FIG. 4 into ICs, but considering performance and cost, it is realistic to make a circuit in which a high frequency amplifier circuit is added to the circuit portion surrounded by the broken line frame A in FIG. Yes, it is being sold by semiconductor manufacturers. Fig. 5 is a microwave IC consisting of the MMIC
11 shows an example of the configuration of the microwave IC 11.
Is composed of a high frequency amplifier circuit 1 ', a mixer circuit 3', a local oscillator 4 ', and an intermediate frequency amplifier circuit 5'.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

By the way, the LNB is premised to be used outdoors, so that it is necessary that there is no abnormality in operation at a temperature of −30 ° C. to + 50 ° C. However, in general, GaAs FETs and HEMTs (Hi
gh Electron Mobility Tran
When a high frequency amplifier circuit is configured with a system, the gain increases at low temperatures and abnormal oscillation tends to occur easily. In the microwave IC 11 including the MMIC, the high-frequency amplifier circuit 1'is basically composed of GaAsFET, and is not an exception.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

The bandpass filter 10 has a direct current cut.
Therefore, the RF input terminal of the microwave IC 11 is directly
It does not have to be a flow blocking type, and the band filter 10
Power section and high frequency signal input terminal of the microwave IC 11
Is usually connected directly with a microstrip line
is there. However, in such a normal configuration, as described above,
Abnormality of microwave IC 11 when operating at low temperature
Oscillation occurs. The cause of this abnormal oscillation is the high frequency signal
S-parameter of the bandpass filter 10 connected to the input terminal
(S shown in FIG.₁₁, S _{twenty two}, S_{twenty one}, S₁₂However, for input / output
Since there is no tropism, S₁₁= S_{twenty two}, S_{twenty one}= S₁₂) Frequency characteristics
Is the point shown in FIG. That is, the target high-frequency signal
Band (11.7(GHz to 12 GHz) RF
Input loss is small and matching is good, but outside the band
Shows the characteristic that almost no reflection is obtained without matching.
Because.

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Claims (4)

[Claims] 1. A microwave IC in which a high-frequency amplifier circuit, a local oscillator circuit, a mixer circuit, and an intermediate-frequency amplifier circuit are integrated, an input section of the microwave IC, and a microwave IC. In a microwave circuit formed by connecting an output part of a bandpass filter having a signal frequency band of a high frequency amplifier circuit as a pass band, an impedance element is provided between the output part of the bandpass filter and the input part of the microwave IC. A microwave circuit characterized by inserting a. 2. The microwave circuit according to claim 1, wherein a capacitor is used as the impedance element. 3. The microwave circuit according to claim 1, wherein a resistance is used for the impedance element. 4. The microwave circuit according to claim 1, wherein an inductance element is used as the impedance element.