JP2001230629A - Gps sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a GPS sensor which has a structure suitable for miniaturization and cost reduction. SOLUTION: This GPS sensor is provided with a GPS antenna 11, preamplifier circuit 12c, analog circuit 12a, digital circuit 12b for processing digital signals provided from the analog circuit 12a and interface connector 16 to be used for outputting a signal provided from the digital circuit 12b or the like, and the ground for the GPS antenna 11, the ground for the preamplifier circuit 12c and the ground for the analog circuit 12a are connected, to shield cases 13 and 14 for electromagnetically shielding the digital circuit 12b or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS sensor that measures a current position by receiving radio waves from a satellite, and more particularly, to an integrated structure that can reduce the size of a device.

[0002]

2. Description of the Related Art GPS is an abbreviation of Global Position Satellite or Global Positioning System, and refers to a system for measuring a position on the earth based on radio signals received from a plurality of satellites. Such a GPS has been rapidly spreading in recent years as an in-vehicle or portable terminal, and its size and cost have been demanded.

FIG. 17 shows a configuration of a conventional GPS sensor. The GPS sensor 40 includes a GPS antenna 41 for receiving radio waves, a receiver main body 42, an interface cable 43, a backup battery 44, and the like.

The GPS antenna 41 has a built-in preamplifier circuit, which amplifies a high-frequency signal obtained by the GPS antenna. In addition, the GPS antenna 41
Are fixed on a metal ground plane 45.
The ground plane 45 has a function of efficiently receiving a radio wave from a satellite, and its effect increases as the surface area increases.

[0005] The high-frequency signal amplified by the preamplifier circuit of the GPS antenna 41 is input to the receiver main body 42 via the antenna cable 46. The receiver main body 42 includes an analog circuit for processing a high-frequency signal and a digital circuit for processing a digital signal output from an A / D converter of the analog circuit, and these are covered by a shield case. In particular, the shield case has a function of preventing high-frequency digital noise generated in a digital circuit from being radiated into the air and adversely affecting the GPS antenna 41 and the like.

[0006] The signal finally output from the digital circuit of the receiver main body 42 is an interface cable 43.
Output to an external device through The interface cable 43 includes a line for supplying a control signal from an external device to the receiver main body 42 and a power supply line.
Further, a memory backup battery 44 of a digital circuit of the receiver main body 42 is connected to the receiver main body 42 separately from the interface cable 43.

FIG. 18 is a block diagram showing the ground (earth) connection of the conventional GPS sensor as described above.
As shown in FIG. 18, the analog circuit and the digital circuit of the receiver main body 42 are covered with a shield case.
On the other hand, the ground plane 45 of the GPS antenna 41 and the ground of the preamplifier circuit are commonly connected.

[0008]

The following problems have been encountered in integrating and miniaturizing a GPS sensor having the above-described GPS antenna, receiver body, and backup battery as main components. .

That is, when the GPS antenna approaches the receiver main body, high-frequency digital noise generated from the digital circuit of the receiver main body goes around to the analog circuit and the GPS antenna, and the S / N ratio deteriorates. In order to avoid this and secure a sufficient S / N ratio, for example, a ground plane of a GPS antenna, a printed circuit board for an analog circuit, a printed circuit board for a digital circuit, a shield case for an analog circuit, and a shield case for a digital circuit are required. It has to be provided separately, and it has been difficult to avoid an increase in cost. As described above, the larger the ground plane of the GPS antenna is, the more the characteristics such as gain are improved.
The overall structure of the PS sensor becomes large, which is against the demand for miniaturization.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a GPS sensor having a structure suitable for miniaturization and cost reduction.

[0011]

A GPS sensor according to the present invention comprises: a GPS antenna for receiving a radio wave for position detection;
A preamplifier circuit for amplifying a high-frequency signal obtained from the GPS antenna, an analog circuit for processing a signal obtained from the preamplifier circuit, a digital circuit for processing a digital signal obtained from the analog circuit, and the digital circuit A GPS sensor having an interface connector used for outputting a signal obtained from
At least a shield case for electromagnetically shielding the digital circuit from the outside is provided, and the ground of the GPS antenna, the ground of the preamplifier circuit, and the ground of the analog circuit are connected to the shield case. .

According to the above-described structure, high-frequency digital noise generated from a digital circuit is effectively absorbed, it is difficult to get around the GPS antenna, and deterioration of the S / N ratio can be suppressed. It is also preferable that the interface connector has a shield, and the shield of the interface connector and one terminal of a backup battery of the digital circuit are further connected to the shield case. There is no problem if the analog circuit and the digital circuit are formed on a common substrate and the interface connector is directly mounted on the common substrate to reduce the size and cost of the device.

Further, it is preferable that the GPS antenna is disposed on a shield case, and the shield case also serves as a ground plane of the GPS antenna. Thus, a large ground plane area can be secured without separately providing a ground plane, which can contribute to miniaturization of the device.

Further, it is preferable that a backup battery is disposed on the shield case, and one terminal of the backup battery is directly connected to the shield case. This can contribute to simplification of wiring, and furthermore, downsizing and cost reduction of the device.

In one embodiment, the shield case is provided so as to cover at least the front and back of a portion of the common substrate on which the digital circuit is formed. For example, a first shield case that covers the front side of the common substrate and a second shield case that covers the back side are provided, and at least one of the first and second shield cases has a portion where a digital circuit is formed and an analog circuit is formed. It is configured to cover both parts. Then, the GP covering the analog circuit of the shield case
When the S antenna is arranged, the connection line between the preamplifier of the GPS antenna and the analog circuit is shortened, which is advantageous in terms of noise resistance.

It is preferable that the end of the shield case is connected so as to make surface contact with the shield of the interface connector, so that the connection between the shield case covering the digital circuit and the like and the shield of the interface connector can be made easily and reliably. Things.

The GPS antenna has a GPS
It is preferable to provide a positioning member for the antenna.
As a result, it is possible to prevent a reduction in noise resistance due to a shift in the mounting position of the GPS antenna.

When the positioning member also functions as a fixing member for the GPS antenna, the mounting and fixing of the GPS antenna becomes easy.

In the case where the antenna cable for connecting the GPS antenna and the circuit is provided, if the positioning member for the antenna cable is provided, it is possible to prevent the noise resistance performance from being changed depending on the routing position of the antenna cable. .

The shield case is 1/4 of the GPS signal wavelength.
It is preferable to connect to the board on which the circuit is mounted at a plurality of locations at the following intervals. This makes it possible to suppress noise leakage from the gap between the substrate and the shield case.

When the interface connector is a USB, the noise from the USB controller can be suppressed by disposing the USB controller together with the digital circuit in the shield case.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 2 and 3 are a perspective view and an exploded view of a GPS sensor according to an embodiment of the present invention. The GPS sensor 10 of the embodiment includes a GPS antenna 11 for receiving radio waves, a printed circuit board 12, an upper shield case 13, a lower shield case 14, a backup battery 15, an interface connector 16, and an interface cable 17.

The high frequency signal obtained by the GPS antenna 11 is input to the analog circuit 12a of the printed circuit board 12 via the power supply pin 11a. In this embodiment, a preamplifier circuit is included in the analog circuit 12a. Also, GP
The S antenna 11 is directly attached to the upper shield case 13,
The upper shield case 13 also serves as a ground plane of the GPS antenna 11.

The printed circuit board 12 includes an analog circuit 12a for processing a high-frequency signal and a digital circuit 12b for processing a digital signal output from an A / D converter of the analog circuit. The upper (front) surface of the printed circuit board 12 is covered with an upper shield case 13, and the lower (back) surface is covered with a lower shield case 14. These shield cases 13 and 14 have a function of preventing high frequency digital noise generated in a digital circuit from being radiated into the air and adversely affecting the GPS antenna 11 and the like.

Therefore, the shield cases 13 and 14 need to cover at least the digital circuit 12b of the printed circuit board 12. In this embodiment, the lower shield case 14 covers only the digital circuit 12b, and the upper shield case 13 covers both the analog circuit 12a and the digital circuit 12b. The GPS antenna 1 is located above the analog circuit 12a of the upper shield case 13.
1, the GPS antenna 11 and the analog circuit 12
The configuration is such that the connection to a is made with the shortest path and good workability by the feed pin 11a of the GPS antenna 11. The upper shield case 13 and the lower shield case 1
Reference numeral 4 is connected to a common potential via a conductive pattern on the printed circuit board 12.

Digital circuit 12b of printed circuit board 12
Is output to an external device through an interface cable 17 connected to the interface connector 16. The interface cable 17 is a shielded cable including a control signal line and a power supply line, and the shield is connected to a shield 16 a of the interface connector 16. As the interface cable 17, for example, a USB standard cable is used.

The shield 16a of the interface connector 16 is a box-shaped metal case having an open surface on which the interface cable 17 is inserted and a surface in contact with the printed circuit board 12. If the shield 16 a of the interface connector 16 is mounted on the printed board 12, the main body of the interface connector 16 is also fixed to the printed board 12.

As can be seen from FIGS. 2 and 3, one end of the upper shield case 13 (the interface connector 16)
Side) is extended, and the extended portion is pressed against the upper surface of the shield 16a of the interface connector 16 during assembly.
As a result, the electrical connection between the shield case (upper shield case 13) of the printed circuit board 12 and the shield 16a of the interface connector 16 is easily and reliably performed by surface contact.

A backup battery 15 is arranged on the upper shield case 13. This backup battery 15 is connected to the digital circuit 12 b of the printed circuit board 12.
For memory backup. As can be seen from FIGS. 2 and 3, a button battery is used as the backup battery 15, and its negative electrode is directly mounted on the upper shield case 13. The upper shield case 13 is connected to the negative side of the memory backup power supply line of the digital circuit 12b via the conductive pattern of the printed circuit board 12.

The positive electrode of the backup battery 15 is connected to the positive side of the memory backup power supply line of the digital circuit 12b provided on the printed circuit board 12 via the positive terminal 15a and the lead wire 15b. In this way, the workability is improved and the cost is reduced for the connection of the backup power supply.

FIG. 1 is a block diagram showing the ground (earth) connection of the GPS having the above structure. In this drawing, the preamplifier circuit 12c is drawn independently of the analog circuit 12a, but as described above, the analog circuit 12a in FIG. 3 includes a preamplifier circuit. The circuits 12a and 12c and the digital circuit 12b are covered by shield cases 13 and 14, and the shield cases
It can be seen that the ground of the S antenna 11, the ground of the preamplifier circuit 12c, the ground of the analog circuit 12a, the shield of the interface connector 16, and one terminal (negative electrode side) of the backup battery 15 are connected.

By the way, the GPS to the shield case 13
Although the antenna 11 is fixed to the antenna 11, if the fixing position of the GPS antenna 11 shifts, the GPS antenna 11 is susceptible to high-frequency noise. Therefore, as shown in FIG. It is preferable that the positioning projection 21 is formed, and the position of the GPS antenna 11 on the shield case 13 is defined by the positioning projection 21. Instead of the protrusion 21, a concave portion 22 into which the GPS antenna 11 fits may be provided as shown in FIG.

Also, as shown in FIGS.
By providing the spring 21 with elasticity or by providing an engagement projection 23 on the inner wall of the projection 21 or the recess 22, the projection 21 or the recess 2 can be formed.
2 may also be responsible for fixing the GPS antenna 11. As shown in FIG. 9, an engagement recess 25 in which the protrusion 21 or the engagement protrusion 23 engages on the side surface of the GPS antenna 11.
Is provided, the GPS antenna 11 can be fixed more reliably.

Also, when the GPS antenna 11 and the circuit side are connected using the antenna cable 26, since the routing of the antenna cable 26 affects the noise resistance, as shown in FIG. 10 or FIG. It is preferable to provide a positioning member 27 for positioning and fixing the antenna cable 26. Although the case where the GPS antenna 11 is attached to the shield case 13 which also serves as a ground plane has been described, the above-described positioning and fixing structure is also effective when a separate ground plane (earth plate) is provided.

FIG. 12 shows another example. Resin case 27
1 / of the GPS signal wavelength (1575.42 MHz) from the opening edge of the shield case 13 of the GPS sensor
By projecting a plurality of projections 13a at intervals of 4 wavelengths or less,
The protrusion 13a is connected to the printed circuit board 12 on which the circuits 12a, 12b, 12c are mounted. This connection can be made by soldering. When noise components corresponding to １ ／ wavelength and ４ wavelength of the GPS signal wavelength among the noise components generated in the circuit mounted on the printed circuit board 12 wrap around the GPS antenna 11, the S / N ratio rapidly deteriorates. However, if the projections 13a of the shield case 13 are connected to the printed circuit board 12 at intervals of 1/4 wavelength or less, noise will not come out of the shield case 13 through the gap between the shield case 13 and the printed circuit board 12. As a result, almost no deterioration of characteristics due to noise of the GPS sensor can be prevented. In the figure, a USB controller 12d for the interface connector 16 formed as a USB is formed as a part of the digital circuit 12b.

FIG. 13 shows the connection between the shield part of the shielded interface connector 16 and the shield case 13 by contacting or soldering the protruding pieces 13b raised from the shield case 13 to both side surfaces of the interface connector 16. Shows what was done. The connection to the side surface of the interface connector 16 contributes not only to an improvement in noise resistance but also to a reduction in the thickness of the GPS sensor.

When the GPS sensor is formed in a disk shape,
As shown in FIG. 14, when the printed circuit board 12 and the shield case 13 (and the shield case 14 if the shield case 14 is provided) are formed in an octagonal shape, the occupation ratio in the disk-shaped resin case is high, and thus the size is reduced. You can get what you can.

At this time, if the length of each side of the octagon is set to be equal to or less than １ ／ of the GPS signal wavelength λ, resonance occurs due to high frequency noise generated from the receiving circuit, and harmonics thereof are generated. The situation where the radio wave becomes the reception frequency of the GPS antenna and the reception sensitivity is deteriorated does not occur.

Also in this case, as shown in FIG. 15, it is more preferable that the protruding portions 13a protrude from the shield case 13 at an interval of λ / 4 or less and are connected to the printed circuit board 12, so that it is more preferable. When the printed circuit board 12 is multilayer and has a ground layer as an inner layer, each protrusion 1
3a may be connected to the ground layer.

In the case having the shield case 14, as shown in FIG.
At the side, projections 14a are provided at an interval of λ / 4 or less. These projections 13a, 14a are connected to the printed circuit board 12 to sandwich the ground layer, and the projections 14a are connected to the shield case 13 (and / or the projections). 13a is the seal cover 1
If it is engaged and connected in 4), more reliable shielding can be performed.

The present invention is not limited to the above embodiment,
It can be implemented in various forms.

[0042]

As described above, the GPS of the present invention
According to the sensor, the shield case that covers the digital circuit and the like is commonly connected to the ground of the GPS antenna 11, the ground of the preamplifier circuit, and the ground of the analog circuit. The generated high-frequency digital noise is effectively absorbed by the shield case, so that it is difficult for the analog circuit and the GPS antenna to go around, and the S / N
Deterioration of the ratio can be suppressed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a ground connection according to an example of an embodiment of the present invention.

FIG. 2 is a perspective view of the same.

FIG. 3 is an exploded perspective view of the same.

FIGS. 4A and 4B are perspective views of a GPS antenna mounting portion, respectively.

FIG. 5 is a perspective view of another example of a GPS antenna attachment portion.

FIGS. 6A and 6B show still another example of the GPS antenna mounting portion, wherein FIG. 6A is a perspective view and FIG. 6B is a cross-sectional view.

FIGS. 7A and 7B show another example of a GPS antenna attachment portion, wherein FIG. 7A is a perspective view and FIG. 7B is a cross-sectional view.

FIGS. 8A and 8B show still another example of the GPS antenna attachment portion, wherein FIG. 8A is a perspective view and FIG. 8B is a cross-sectional view.

9A and 9B show another example of a GPS antenna attachment portion, wherein FIG. 9A is a perspective view and FIG. 9B is a cross-sectional view.

FIG. 10 is an explanatory diagram showing a mounting portion of an antenna cable.

FIG. 11 is an explanatory view showing another example of the mounting portion of the antenna cable.

12A and 12B show another example of the GPS sensor, in which FIG. 12A is a cross-sectional view, and FIG. 12B is a perspective view of a shield case and a printed board.

FIG. 13 is a perspective view of a shield case and an interface connector according to the third embodiment.

FIG. 14 is a perspective view of a shield case and a printed circuit board in still another example of the GPS sensor.

FIGS. 15A and 15B show another example of the shield case, and FIGS.
Are perspective views, respectively.

16A and 16B show still another example of the shield case and the printed circuit board, wherein FIG. 16A is an exploded perspective view, and FIG. 16B is a side view.

FIG. 17 is a perspective view showing a configuration of a conventional GPS.

FIG. 18 is a block diagram showing ground connection of a conventional GPS.

[Explanation of symbols]

 Reference Signs List 10 GPS 11 GPS antenna 12 Printed circuit board 12a Analog circuit 12b Digital circuit 12c Preamplifier circuit 13 Upper shield case (first shield case) 14 Lower shield case (second shield case) 15 Backup battery 16 Interface connector

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuichiro Naoi 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor Koji Yamamoto 1048 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Works (72) 72) Inventor Hideki Oka 1048 Kadoma Kadoma, Kadoma City, Osaka Pref. (72) Inventor Yuki Nishimoto 1048 Kadoma Kadoma, Kadoma, Osaka Pref. Matsushita Electric Works F-term (reference) 5J021 AA01 AB06 CA06 FA17 FA24 FA26 HA03 HA04 JA08 5J062 BB01 CC07 DD11 GG02 5K016 AA06 AA07 BA00 BA01 BA06 CA01 DA02 EA08

Claims (14)

[Claims] A GPS antenna for receiving a radio wave for position detection; a preamplifier circuit for amplifying a high-frequency signal obtained from the GPS antenna; an analog circuit for processing a signal obtained from the preamplifier circuit; A digital circuit for processing a digital signal obtained from the circuit;
A GPS sensor provided with an interface connector used for outputting a signal obtained from the digital circuit, wherein a shield case for electromagnetically shielding at least the digital circuit from the outside is provided, and a ground of the GPS antenna; A GPS sensor, wherein a ground of a preamplifier circuit and a ground of the analog circuit are connected to the shield case. 2. The shield according to claim 1, wherein the interface connector has a shield, and the shield of the interface connector and one terminal of a backup battery of the digital circuit are further connected to a shield case. GPS sensor. 3. The GPS sensor according to claim 1, wherein the analog circuit and the digital circuit are formed on a common substrate. 4. The G according to claim 3, wherein the interface connector is directly mounted on the common board.
PS sensor. 5. The GPS sensor according to claim 1, wherein a GPS antenna is disposed on the shield case, and the shield case also serves as a ground plane of the GPS antenna. 6. The battery according to claim 1, wherein a backup battery of the digital circuit is disposed on the shield case, and one terminal of the backup battery is directly connected to the shield case. The GPS sensor as described. 7. The GPS according to claim 3, wherein the shield case is provided so as to cover at least the front and back of a portion of the common substrate on which the digital circuit is formed. Sensor. 8. The shield case includes a first shield case covering a front side of a common substrate and a second shield case covering a back side, and at least one of the first and second shield cases has the digital circuit formed thereon. The GP according to claim 7, wherein the GPS antenna covers both a portion where the analog circuit is formed and a portion where the analog circuit is formed in the shield case.
S sensor. 9. The GPS sensor according to claim 1, wherein an end of the shield case is connected so as to make surface contact with a shield of the interface connector. 10. A GPS antenna to which a GPS antenna is attached
The GPS sensor according to any one of claims 1 to 9, further comprising a positioning member for a PS antenna. 11. The G according to claim 10, wherein the positioning member also serves as a fixing member of the GPS antenna.
PS sensor. 12. The GPS sensor according to claim 1, further comprising an antenna cable positioning member for connecting the GPS antenna and a circuit. 13. The shield case has a GPS signal wavelength of 1.
The GPS sensor according to any one of claims 1 to 12, wherein the GPS sensor is connected to a substrate on which a circuit is mounted at a plurality of locations at an interval of / 4 or less. 14. The system according to claim 1, wherein the interface connector is a USB, and the USB controller is disposed in the shield case together with the digital circuit.
14. The GPS sensor according to any one of items 13 to 13.