JPH0797729B2 - Planar antenna - Google Patents

Description

TECHNICAL FIELD The present invention relates to a planar antenna for receiving satellite broadcasting.

BACKGROUND ART Generally, as shown in FIG. 4, a receiving system for receiving a satellite broadcast includes a plane antenna 3 including a plane antenna body 1 and a down converter 2, a tuner 4, and a television receiver 5. Has been done. Here, the state of the received image reproduced by the television receiver 5 is greatly influenced by the input signal level-to-noise ratio (C / N) input to the tuner 4, and as shown in FIG. When the signal level-to-noise ratio (C / N) falls below 9 dB (threshold level), the overall SN ratio deteriorates sharply and the image becomes extremely bad. This relationship is derived by C / N = G / T + EIRP-51.5 [dB]. Where EIRP
Is a numerical value (reception electric field strength) represented by the product of the transmission power of the broadcasting satellite and the gain of the transmission antenna in the direction of the reception point, and the antenna performance index G / T is , G is the gain of the planar antenna body 1, Ta
/ l is the antenna noise of the antenna itself, (1-1 / l) 290
Is noise of the power supply line output from the power supply line, and (NF-1) × 290 is converter noise generated by the down converter 2.

As is clear from the above relational expression, if the input signal level to noise ratio (C / N) input to the tuner 4 is to be increased, the antenna gain G is increased or each noise (antenna noise, feed line It can be seen that it is better to reduce the noise (converter noise). However, antenna noise (Ta / l)
Is almost determined by the type of antenna (parabolic type, array type, etc.) and the feed line noise ((1-1 / l) × 290) is determined by the material used, so to obtain a satisfactory received image It is necessary to increase the antenna reception area by increasing the antenna reception area, or decrease the noise figure NF of the down converter 2 to reduce the converter noise.

For example, if the input signal level-to-noise ratio C / N = 14 dB is required to obtain a satisfactory received image, the noise figure N
If either F or antenna gain G is determined, the other is also determined. Here, as shown in FIG. 6 (however, the relationship between the diameter D of the parabolic antenna and the antenna gain G), the antenna gain G becomes larger (in the case of a planar antenna, the number of arrays is increased to increase the antenna number G). However, if the receiving area of the antenna becomes large, the antenna body becomes large and the weight becomes large, and the installation work of the antenna becomes troublesome, which causes inconvenience for general household use. . Therefore, it is desirable that the receiving area of the antenna be as small as possible, and it is required to lower the noise figure NF of the down converter 2 accordingly.

By the way, the down converter 2 is composed of a plurality of active circuits, but as shown in FIG.
_{When 19} C ₂ ... Cn are connected in series, the noise figure NF of the entire device is NF = F ₁ + (F ₂ -1) / G ₁ + (F ₃ -1) / G ₁ G ₂ ＋ …… (Fn
-1) / G ₁ G ₂ … Gn, and the NF of the entire device is greatly influenced by the NF of the active circuit (front end low-noise amplifier) C ₁ of the first stage, and the loss to the active circuit C _{1 of the} first stage is smaller. NF of the whole device becomes small. Therefore, the same input signal level to noise ratio C /
To obtain N, the active circuit C in the first stage with a low noise figure NF
It turns out that it is desirable to use ₁ with low loss. However, in the conventional example, as shown in FIG. 8, the planar antenna body 1 and the down converter 2 are connected via the connector 2a, and the down converter 2 is an active circuit at the first stage. Since the use condition that the amplifying device of the low noise amplifier (eg, GaAs FET, HEMT, etc.) operates with the minimum noise figure NF has not been realized, it is satisfactory when the flat antenna main body 1 having a small receiving area is used. There is a problem that the reception performance for obtaining a possible reception image cannot be obtained.

That is, the characteristic impedance of the connector 2a is generally 50
Since the output impedance of the planar antenna body 1 and the input impedance of the down converter 2 are both 50 Ω so that no reflection loss occurs at the connector connection part, the amplification used for the low noise amplifier of the down converter 2 The noise figure characteristic (NF characteristic) of the device (GaAs FET) is as shown in Fig. 9, and the best point (NF = 1.2dB) is not in the vicinity of 50Ω (center part), but at a considerably shifted position (approximately 20 + j20Ω). It has become. Therefore, in the conventional example, an impedance matching circuit that performs impedance matching is added to the signal input section at the front end of the down converter 2, but a loss due to the impedance matching circuit occurs in addition to the loss due to the connector 2a. There was a problem that the noise figure (NF) deteriorates and the reception performance deteriorates. For example, even when using a low noise amplifying device with a noise figure NF of about 1.2 dB at around 12 GHz, the noise figure NF of the down converter 2 substantially deteriorates to more than 1.6 dB, which causes a problem in high-definition TVs. When trying to obtain a high quality received image, sufficient receiving performance cannot be obtained, so that there is a problem that the receiving area of the planar antenna body 1 must be increased to increase the antenna gain G. there were.

[Object of the Invention] The present invention has been made in view of the above points, and an object of the present invention is to enable an amplification device of a low noise amplifier to operate in a state where the noise figure is minimum, and to provide a planar antenna body. It is an object of the present invention to provide a planar antenna which can obtain a sufficient receiving performance even when the receiving area is reduced, and has a simple structure and a low cost.

DISCLOSURE OF THE INVENTION (Structure) The present invention relates to a suspended tri-plate in which a ground conductor plate, a power supply circuit board on which a power supply circuit pattern is formed, and a radiation circuit board on which a radiation circuit pattern is formed are laminated at appropriate intervals. -Type planar antenna body is formed, and the low noise amplifier circuit is inserted in the gap between the grounding conductor plate and the feed circuit board in parallel with both boards to mount the feed circuit board on the crocodile board. By connecting the signal input terminal of the device to the feeding point of the power supply circuit and connecting the ground terminal of the amplification device to the ground conductor plate through the through hole provided in the board, the amplification factor of the low noise amplifier is reduced. It can be operated in the minimum state, and it is possible to obtain sufficient reception performance even when the reception area of the flat antenna main body is reduced, Growth is what simple and cost to provide a cheap plane antenna.

(Embodiment) FIGS. 1 to 3 show an embodiment of the present invention, which is a low noise amplifier forming a front end of a planar antenna body 1 and a down converter 2 for amplifying an antenna output and converting it to a low frequency. As shown in FIG. 1, the planar antenna body 1 includes a ground conductor plate 10 and
A power supply circuit board 11 on which a power supply circuit pattern is formed, and a radiation circuit board 12 on which a radiation circuit pattern is formed are appropriately spaced by 13a,
Stacked with 13b to form a suspended triplate type. In addition, the feeding circuit board 11 and the radiation circuit board 12
The conductors 11a and 12a of the circuit pattern on the insulating substrate 11
It is formed on b and 12b, and is formed by covering insulating sheets 11c and 12c on conductors 11a and 12a. Further, in the gap 13a between the ground conductor plate 10 and the power feeding circuit plate 11, a substrate 16 on which a low noise amplifier circuit is mounted is interposed in parallel with both plates 10 and 11, and an amplification device for the low noise amplifier ( For example, a feed circuit board 11 of a substrate 16 having a predetermined dielectric substrate 16a and an insulating plate 16b for adjusting the thickness is provided on the alligator. The gate terminal 15g of the amplifying device 15 is connected to the feeding point of the feeding circuit, and the source terminal 15s, which is the ground terminal of the amplifying device 15, is connected to the ground conductor plate 10 through the through hole 18 provided in the substrate 16. There is. Here, in the embodiment, the gate terminal 15g of the amplification device 15 connected to the feeding point of the feeding circuit is electrostatically inductively coupled to the conductor 11a at the feeding point of the feeding circuit via the coupling conductor 17. The insulating sheet 11 at the feeding point of the feeding circuit board 11
The gate terminal 15g may be connected to the conductor 11a exposed by peeling off c by soldering. Further, a negative bias voltage is applied to the gate terminal 15g of the amplification device 15 via the gate bias supply line 19a, and a positive bias voltage is applied to the drain terminal 15d via the drain bias supply line 19b. Both bias voltages are set so that the amplification device 15 operates at the lowest value of the noise figure NF. Furthermore, an amplification device consisting of GaAs FET 15
Since the input impedance at the point where the noise figure NF of is operating at the lowest is around (20 + j20) Ω, design the power supply circuit pattern so that the output impedance at the power supply circuit's power supply point becomes the above input impedance in advance. The impedance matching pattern is formed according to the above) to perform impedance matching. The output line 19c is connected to the output connector, and the down converter 2 is connected to the output connector.
Are connected. In this case, it goes without saying that the low noise amplifier at the front end of the down converter 2 can be omitted.

Further, in the embodiment, the connection conductor 20 that connects the source terminal 15s of the amplification device 15 and the ground conductor plate 10 through the through hole 18 is provided by projecting by narrowing down the ground conductor plate 10, and the connection conductor 20 The source terminal 15s is connected to the tip by soldering. The tip of the connecting conductor 20 is formed to be substantially flush with the upper surface of the substrate, so that the source terminal 15s can be easily connected. A tap pin or a screw may be provided upright on the ground conductor plate 10 as the connecting conductor 20. In the figure, 21 is a feedthrough capacitor for supplying a bias voltage.

Now, in the embodiment, since the gate terminal 15g, which is the signal input terminal of the amplification device 15 of the low noise amplifier for amplifying the antenna output, is directly connected to the feeding point of the feeding circuit without using the connector, Compared to the connected conventional example, loss is reduced, and an impedance matching circuit to match the characteristic impedance of the connector is not required.
Can be operated with a minimum noise figure NF. Therefore, even when the receiving area of the planar antenna body 1 is reduced, a good received image can be obtained, and the receiving performance can be improved. Further, the substrate 16 on which the low noise amplifier circuit is mounted is interposed between the ground conductor plate 10 and the power feeding circuit plate 11, and since the substrate 16 and the auxiliary ground conductor 17 can function as a spacer, they are grounded. Since the spacer provided to keep the gap 13a between the conductor plate 10 and the power supply circuit plate 11 constant can be omitted, the structure can be simplified and the cost can be reduced.

Further, in the embodiment, since the gate terminal 15g of the amplification device 15 and the conductor 11a at the feeding point of the feeding circuit pattern are connected by electrostatic induction coupling in a non-contact manner, soldering work becomes unnecessary and assembly is possible. As a conductor 11a that can be easily formed and forms a power supply circuit pattern of the power supply circuit board 11,
Insulating substrate 11 can be easily connected while using aluminum, which is cheaper than copper and vulnerable to corrosion.
Therefore, it is not necessary to use a heat resistant synthetic resin for b and the insulating sheet 11e. Furthermore, in the embodiment, the connection conductor 20 for connecting the source terminal 15s of the amplification device 15 and the ground conductor plate 10 through the through hole 18 is projectingly provided on the ground conductor plate 10, and the source terminal is provided at the tip of the connection conductor 20. Since 15s is connected, through hole processing can be easily performed. On the other hand, since the connecting conductor 20 functions as a positioning protrusion when the substrate 16 is mounted, the assembling work can be easily performed.

[Advantages of the Invention] As described above, according to the present invention, a grounded conductor plate, a feeding circuit board having a feeding circuit pattern formed thereon, and a radiation circuit board having a radiation circuit pattern formed thereon are stacked at appropriate intervals to create a suspended triad. Form a plate type planar antenna body,
In the gap between the grounding conductor plate and the power feeding circuit plate, a low noise amplifier circuit is inserted in parallel with both plates, and the signal input terminal of the amplification device of the low noise amplifier is connected to the power feeding circuit board. In addition to connecting to the feeding point, the grounding terminal of the amplification device is connected to the grounding conductor plate through the through hole provided on the base, and it is possible to operate the amplification device of the low noise amplifier in the state where the noise figure is minimum. Therefore, there is an effect that a sufficient receiving performance can be obtained even when the receiving area of the flat antenna main body is made small, and a flat antenna having a simple structure and low cost can be provided.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of an essential part of an embodiment of the present invention, FIG. 2 (a) is a sectional view of an essential part of the same, FIG. 2 (b) is an enlarged sectional view of an essential part of the same, and FIG. 4 is a schematic configuration diagram of the satellite broadcasting receiving system, FIGS. 5 to 7 are operation explanatory diagrams of the same, FIG. 8 is a schematic configuration diagram of a conventional example, and FIG. 9 is an operational explanation of the same. It is a figure. 1 is a plane antenna main body, 2 is a down converter, 3 is a plane antenna, 10 is a ground conductor plate, 11 is a feeding circuit plate, 12 is a radiation circuit plate, 13a and 13b are gaps, 15 is an amplifying device, and 15s is a ground terminal ( Source terminal), 15g is a signal input terminal (gate terminal), 16 is a substrate, 18 is a through hole, and 20 is a connecting conductor.

Claims (3)

[Claims] 1. A suspended triplate type planar antenna body is formed by laminating a grounding conductor plate, a feeding circuit plate having a feeding circuit pattern formed thereon, and a radiation circuit plate having a radiation circuit pattern formed thereon at an appropriate interval. Then, in the gap between the ground conductor plate and the power supply circuit board, a board on which the power supply circuit board is mounted with the low noise amplifier circuit is interposed in parallel with both the boards,
A planar antenna characterized in that a signal input terminal of an amplifying device of a low noise amplifier is connected to a feeding point of a feeding circuit, and a ground terminal of the amplifying device is connected to a ground conductor plate through a through hole provided on a substrate. 2. A power supply circuit board is formed by arranging a conductor of a power supply circuit pattern on an insulating substrate, and a signal input terminal of an amplification device is opposed to a conductor of a power supply point of the power supply circuit pattern through the insulating substrate. The planar antenna according to claim 1, wherein the planar antenna is electrostatically inductively coupled. 3. A patent characterized in that a connecting conductor for connecting a ground terminal of an amplifying device and a ground conductor plate through a through hole is projectingly provided on the ground conductor plate, and the ground terminal is connected to a tip of the connecting conductor. The planar antenna according to claim 1.