JPH1098311A - Microwave equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce interferences by unwanted frequency components in LNB (low noise frequency converter) used for receiving the signal of satellite broadcasting, satellite communication or the like. SOLUTION: Wall parts (projecting parts 2a, 2b, etc.) formed by partially thickening the inner part of a shield case 2 are provided near a signal line pattern (50Ω pattern) 1a on the surface of a substrate 1, and a structural part which is similar to a waveguide formed near the 50Ω pattern 1a is provided with a width (w) and a height (h) and is made partially narrow. The waveguide is a kind of an HPF(high-pass filter) and improves a cut-off frequency at the time of reducing the width (w) and the height (h). Thereby a pass band as the waveguide is narrowed as a result and unwanted components are prevented from passing through. In addition, the width L of the projecting parts 2a and 2b is longer than at least one wavelength of a signal desired to be cut off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave device, and more particularly, to an LNB (low noise frequency converter) used for signal reception in satellite broadcasting or satellite communication, etc. Reducing interference.

[0002]

2. Description of the Related Art An LNB for receiving a satellite signal is attached to an antenna (parabola or the like), and converts the frequency (for example, 12 GHz band) of a microwave signal received by the antenna to a required intermediate frequency band (for example, 1 GHz band). This is converted into a signal. FIG. 2A shows the main functional blocks of the frequency conversion processing function of the LNB according to the processing flow, and is shown when viewed from the circuit pattern side (surface) of the microstrip line substrate of the LNB. FIG. In FIG. 1A, reference numeral 21 denotes a shield case,
It has a box shape with an open lower part. Reference numeral 22 denotes a microstrip line substrate having a signal line pattern and a ground pattern for forming a high-frequency circuit and a mixer circuit for frequency conversion, a ground pattern, and a circuit element on one side, and a ground conductor on one side on the back side. It is a thing. Although not shown, the ground conductor comes into surface contact with the inner bottom surface of a separately provided shield case (a box having an open top).

[0003] The shield case 21 is mounted such that the opening side of the case comes into contact with a ground pattern provided on the peripheral edge of the surface of the substrate 22. The ground pattern is connected to a ground conductor on the back surface of the substrate by a through hole. The RF input (for example, 12 GHz band) is connected to the required intermediate frequency (for example, 1 GHz).
(Hz band), it goes through various processes as shown in the figure. That is, a probe 23 that picks up an RF input, a matching unit 24 that mainly performs impedance matching based on the length and width of the pattern, an amplifier circuit 25 that amplifies a signal, a matching unit 26 that performs impedance matching in the same manner as described above, and unnecessary components. Trap circuit 27 for removal, coupling circuit 28, matching section 29 similar to the above, amplifier circuit 30 for signal amplification, matching section similar to the above
31, RF filter 32, mixer circuit 33 for frequency conversion, L
A PF 34; and an amplifier circuit 35 that amplifies the signal and outputs an intermediate frequency signal (IF).

[0004] The above-mentioned series of circuit parts are shielded by a shield case to prevent unnecessary radiation and interference from others. The series of circuit parts (23 to 35) are composed of circuit elements and signal line patterns (copper copper) on a board for connecting the circuit elements to each other. Ω). Therefore, hereinafter, the signal line pattern of the substrate 22 is referred to as “50Ω pattern 22a”. Now, when the signal line pattern is drawn in relation to the shield case 21 with the cross section aa in FIG.
(B). In FIG. 2B, FIG.
21a and 21b represent the opening sides of the shield case 21, 22a is the 50Ω pattern on the surface of the substrate 22, 22b and 22c are the ground patterns,
d is a ground conductor on the back surface of the substrate 22. Ground pattern 22b,
The ground conductor 22c and the ground conductor 22d are connected by through holes 31a and 31b. As shown in the figure, the 50Ω pattern 22a is inside the shield case 21 surrounded by the opening sides 21a and 21b.
This provides a kind of rectangular waveguide structure. This rectangular waveguide-like structure may be a factor of deteriorating the characteristics of the LNB in a conventional LNB as described later.

[0005]

In the above-mentioned receiving LNB, various unnecessary signal components are input in addition to the original received signal wave. For example, a satellite communication antenna which also performs transmission and reception can be cited. In the case of this antenna, the transmission LN
B and the receiving LNB are provided close to each other. for that reason,
A transmission signal component from the transmission LNB having an output of several watts may be mixed into the reception LNB. In addition to this example, there is a possibility that various unnecessary signal components are input to the receiving LNB. The receiving LNB generally has a small level signal (−
(About 70 dBm) and converts it to an intermediate frequency signal of the required frequency, and its operation band is generally wide. Therefore, when an unnecessary component having a large power is input, the RF amplifier section is saturated and becomes non-linear, and various harmonic components other than the fundamental wave are generated.

Further, the unnecessary harmonic components may be transmitted through the above-mentioned waveguide portion without transmitting through the signal line pattern (50Ω pattern). In this case, characteristics such as the total gain of the LNB and NF (noise figure) are degraded by harmonic components and the like. If the harmonic component transmits only the signal line pattern, a method of inserting a trap circuit on the signal line pattern is effective, but it does not make sense to transmit the waveguide portion. . Therefore, there is a need for a method of reducing components transmitted through the waveguide portion as much as possible. Thereby, it is possible to prevent the LNB characteristics such as the total gain and NF (noise figure) from deteriorating. The present invention has been made in view of such a background, and when a signal of an unnecessary component is input to a receiving LNB, a microwave that reduces a component transmitted through a waveguide structure inside the LNB is used. It is intended to provide a device.

[0007]

According to the present invention, a signal line pattern and a ground pattern for forming a high-frequency circuit and a mixer circuit for converting a received signal frequency to a required frequency are provided on the front surface, and the ground is provided on the back surface. A microstrip line substrate provided with a conductor is attached to a ground pattern on a peripheral edge of a surface of the microstrip line substrate so that an opening side of a box-shaped shield case having an open lower part is in contact with the shield case. It is an object of the present invention to provide a microwave apparatus in which a wall having a required thickness is provided so as to cross in the lateral direction, and an opening space having a required height and a required width is provided substantially at the lower center of the wall.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As in the above-mentioned means, a wall is formed near the signal line pattern (50Ω pattern) on the surface of a substrate by forming the inside of a shield case to be partially thick.
The waveguide structure formed near the Ω pattern is narrowed. In this case, a ground pattern may be provided on the substrate surface on both sides of the 50Ω pattern and in contact with the wall portion, and connected to the ground conductor on the back surface through a through hole. The waveguide is a kind of H
In the case of a PF (high-pass filter) and a rectangular waveguide, the cut-off frequency increases when the width or height is reduced. Therefore, the width and height can be reduced by providing the above-described wall portion to partially narrow the rectangular waveguide structure, and the cutoff frequency of the waveguide increases. As a result, the pass band as the HPF is narrowed, and the passage of unnecessary components can be prevented.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a microwave device according to the present invention will be described with reference to the drawings. FIG. 1 is a main part configuration diagram of a microwave device (specifically, LNB) according to the present invention. FIG. 1A is a main part top view of a part of a signal line pattern part in FIG. (B) is a side view of a main part when b in FIG. (A) is a cross section. In FIG. 1, reference numeral 1 denotes a microstrip line substrate, and the surface thereof has a 50Ω pattern.
1a, required ground patterns 1b and 1c, circuit elements (not shown), and the like are provided, and a ground conductor 1d is provided on one surface on the back surface. Reference numeral 2 denotes a shield case, which corresponds to the shield case 21 in FIG. Note that L
Descriptions of terms such as the configuration of the NB and “50Ω pattern” are omitted because they are common to FIG.

The gist of the present invention is to partially narrow the rectangular waveguide structure formed by the shield case 2. Specifically, a wall of a required thickness is provided in a part of the shield case 2 so as to cross in the horizontal direction, and an opening having a required height h and a required width w is provided at a substantially lower center portion of the wall. A space is provided. When the wall is viewed from the upper part of the shield case, the wall has protrusions such as 2a and 2b in FIG. The width L of the projection is longer than at least one wavelength of the signal to be cut off. The longer the L, the greater the amount of attenuation. The bottom surfaces of the projections 2a and 2b are in contact with the substrate 1.

(A) When viewed from the side as a cross section of FIG. 1B, as shown in FIG. 2B, the height from the substrate 1 to the top surface of the shield case 2 is lower than that of other portions. , The width is also smaller than the other portions. Convex part 2 in FIG.
Although not shown (FIG. B), a ground pattern may be provided on the substrate portion in contact with the bottom surfaces of a and 2b, and the ground pattern may be connected to the ground conductor 1d on the back surface of the substrate via a through hole. The opening side of the shield case 2 is in contact with the ground patterns 1b and 1c as in FIG. 2B, and is connected to the ground conductor 1d through the through holes 3a and 3b. As described above, the rectangular waveguide portion formed near the 50Ω pattern 1a has a height h and a width w.

In the case of a rectangular waveguide, the relationship between the height h, the width w, and the cutoff frequency fc can be expressed by an approximate expression as follows (Equation 1).

(Equation 1)

However, C1 and C2 are constants determined in the mode of the microwave. From the above formula, the cutoff frequency increases as the height h or the width w decreases. The waveguide is a kind of HPF (high-pass filter). Therefore, increasing the cutoff frequency improves the ability to eliminate unnecessary components on the low-pass side of the HPF. Therefore, the height h and the width w are determined so as to obtain desired cutoff frequency characteristics. As a result, the low-pass side component of the HPF that has conventionally been transmitted through the waveguide portion is blocked by the present invention, and the influence of the unnecessary component can be reduced. Further, the above-mentioned wall portion is provided before the mixer circuit 33.
It is desirable to provide for the 50Ω pattern 1a. This is because the mixer circuit 33 is a non-linear circuit, and unless it is eliminated before the mixer circuit, a large number of harmonics are generated, making it difficult to cope with it. In addition, the above-mentioned wall portion is provided with a plurality of 50Ω patterns 1a.
Is provided, the ability to remove unnecessary components can be improved.

[0014]

As described above, according to the present invention, in a microwave device such as an LNB for receiving satellite signals, a rectangular waveguide structure formed inside the LNB is partially narrowed. Since the internal configuration of the shield case of the LNB is changed from that of the conventional case, the cutoff frequency of the rectangular waveguide structure can be increased. As a result, unnecessary components that have conventionally been transmitted through the waveguide portion are blocked, and the overall gain as an LNB or N
Deterioration of characteristics such as F (noise figure) can be prevented. Particularly, when the transmitting LNB and the receiving LNB are provided close to each other as in the case of a satellite communication antenna for both transmitting and receiving, the present invention is applied to the case where the component mixed from the transmitting LNB to the receiving LNB is used. This is effective for preventing deterioration of characteristics on the LNB side.

[Brief description of the drawings]

1A and 1B are main part configuration diagrams of a microwave device according to the present invention, wherein FIG. 1A is a main part top view of a part of a signal line pattern part of FIG. B)
FIG. 2 is a side view of a main part of FIG.

FIG. 2 is a diagram for explaining a conventional microwave device;
FIG. 2A is a top view of a main part, and FIG. 2B is a side view of the main part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Microstrip board 1a 50Ω pattern 1b, 1c Grounding pattern 1d Grounding conductor 2 Shield case 2a, 2b Convex part 3a, 3b Through hole 21 Shield case 22 Microstrip board 22a 50Ω pattern 22b, 22c Grounding pattern 22d Grounding conductor 31a, 31b Through hole

Claims (5)

[Claims] 1. A microstrip line having a signal line pattern and a ground pattern for forming a high-frequency circuit and a mixer circuit for converting a received signal frequency to a required frequency on a front surface, and a ground conductor provided on a back surface. A box-shaped shield case having a lower part opened is attached to the ground pattern on the periphery of the surface of the substrate so that an opening side of the box-shaped shield case is in contact with the ground pattern. A microwave device comprising: a wall portion having an opening space having a required height and a required width substantially below the center of the wall portion. 2. The microwave device according to claim 1, wherein said wall portion is provided on a signal line pattern before said mixer circuit. 3. The microwave device according to claim 1, wherein the wall portion is provided on a plurality of signal line patterns. 4. A ground pattern is provided at a portion where the wall portion contacts the surface of the substrate, and the ground pattern is connected to the ground conductor through a through hole.
The described microwave device. 5. The microwave device according to claim 1, wherein a width and a height of the opening space are set to have a desired cutoff frequency.