GPS receiver sharing an antenna ground plane with an EMI shield

• US 6,522,291 B1
• Filed: 11/21/2000
• Issued: 02/18/2003
• Est. Priority Date: 12/10/1999
• Status: Expired due to Term

• Current Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Asahi Matsushita Electric Works Ltd. (Panasonic Holdings Corporation)
• Inventors: Yamamoto, Koji, Yamamoto, Katsuya, Naoi, Yuichiro, Oka, Hideki, Nishimoto, Hiroki, Noguchi, Takahide
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/716,451
• Time in Patent Office: 819 Days
• Field of Search: 342/357.06, 701/213, 343/700.MS
• US Class Current: 342/357.64
• CPC Class Codes: G01S 19/36 relating to the receiver frond end
• CPC Class Codes: H01Q 1/526 Electromagnetic shields
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• CPC Class Codes: H01Q 9/0407 Substantially flat resonant element parallel to ground plane, e.g. patch antenna dipole H01Q9/285; monopole H01Q9/40

Abstract

A compact GPS receiver includes a GPS antenna composed of a patch and a ground plane to receive high frequency satellite signals, an analog circuit which processes the high frequency satellite signals into a digital signal, a digital circuit which processes the digital signal to compute positional coordinates of the GPS antenna, and an interface connector which outputs the positional coordinates to an external device. A substrate is provided to support the GPS antenna, the analog circuit, the digital circuit, and the interface connector. An EMI (electromagnetic interference) shield is provided to shield at least the digital circuit to block a noise developing at the digital circuit from interfering with the GPS antenna. The GPS antenna is mounted on the EMI shield to share the ground plane with the EMI shield, while keeping the patch insulated electrically from the EMI shield. Thus, the GPS receiver can be made compact by making the use of the EMI shield also as the ground plane of the antenna, while assuring to block the noise from interfering with the antenna and affording sufficient antenna gain with the increased ground plane.

Claims

1. A GPS receiver comprising:

a GPS antenna receiving high frequency satellite signals, said antenna comprising a patch and a ground plane;

an analog circuit attached to a substrate that receives the high frequency satellite signal from the GPS antenna and processes said high frequency satellite signals into a digital signal;

a digital circuit attached to the substrate that receives the digital signal from the analog circuit and processes said digital signal to compute positional coordinates of said GPS antenna;

an interface connector attached to the substrate that receives the positional coordinates and outputs said positional coordinates to an external device; and

an EMI (electromagnetic interference) shield which surrounds said substrate as well as at least said digital circuit on said substrate to block a noise developing at said digital circuit from interfering with said GPS antenna,

said GPS antenna being directly mounted on said electromagnetic interference shield so as to define said ground plane only by said electromagnetic interface shield, said patch being electrically insulated from said electromagnetic interference shield.

2. The GPS receiver as set forth in claim 1, wherein

said substrate comprises a single double-sided circuit board having a top mount surface and a bottom mount surface, said digital circuit being formed by a plurality of components which are mounted partly on said top mount surface and partly on said bottom surface,

said EMI shield is composed of a top cover fitted over said top mount surface and a bottom cover fitted over said bottom mount surface, said top cover and said bottom cover being cooperative to surround the components forming said digital circuit.

3. The GPS receiver as set forth in claim 1, wherein

said interface connector comprises a universal serial bus (USB) connector, and said digital circuit includes a universal serial bus (USB) controller for said USB connector.

4. The GPS receiver as set forth in claim 2, wherein

said top cover and said bottom cover are cooperative to surround the components forming said analog circuit.

5. The GPS receiver as set forth in claim 1, wherein

said interface connector is surrounded by a connector shield which has a top end portion projecting above a top plane of said EMI shield, said top end portion being electrically connected to said top plane so as to have an electrical potential substantially equal to the top plane of said EMI shield.

6. The GPS receiver as set forth in claim 5, wherein

said EMI shield is formed with a lug which projects above the top plane of said EMI shield and comes into surface contact with the top end portion of said connector shield.

7. The GPS receiver as set forth in claim 1, wherein

said substrate includes a ground conductor for said analog circuit and said digital circuit, and said EMI shield has a periphery which is electrically connected to said ground conductor at points spaced by a distance of one-fourth (¼

) of a wavelength of said satellite signal or less.

8. The GPS receiver as set forth in claim 2, wherein

said circuit board has a ground conductor embedded between said top mount surface and said bottom mount surface, said ground conductor being electrically connected to a plurality of pads provided at a circumference of said circuit board,

said EMI shield having a periphery corresponding to the circumference of said circuit board and having a plurality of anchors which are arranged around the periphery and bonded to said pads of the circuit board, respectively and

said anchors being spaced from each other by a distance of one-fourth (¼

) of a wavelength of said GPS signal or less.

9. The GPS receiver as set forth in claim 1, wherein

said EMI shield has a top plane which is configured into a regular polygon having four sides or more,

said patch being mounted on said top plane at a location offset from the center of said regular polygon.

10. The GPS receiver as set forth in claim 9, wherein

a radome is provided to cover said GPS antenna, said EMI shield, said analog circuit, and said digital circuit, said radome having a bottom surface which is spaced from said patch by a distance longer than a critical distance below which a substantial loss in antenna gain appears.

11. The GPS receiver as set forth in claim 1, wherein

said EMI shield is formed with a positioning structure for accurately positioning said patch on the top plane of said EMI shield.

12. The GPS receiver as set forth in claim 1, wherein

said patch is electrically connected to said analog circuit through a feed cable, and said EMI shield is formed with a retainer for retaining said feed cable in a fixed position.

13. The GPS receiver as set forth in claim 1, wherein

said digital circuit includes a memory storing data with regard to the computation of said positional coordinates, said data being backed up by a battery, said battery being mounted on said EMI shield with a negative electrode of said battery being electrically connected directly to said EMI shield.

14. The GPS receiver as set forth in claim 1, wherein

said patch is mounted on said EMI shield at a location immediately upward of said analog circuit on said substrate and is connected to said analog circuit by means of a feed pin depending from said patch.

15. A GPS receiver comprising:

a GPS antenna receiving high frequency satellite signals, said antenna comprising a patch and a ground plane;

an analog circuit attached to a substrate that receives the high frequency satellite signal from the GPS antenna and processes said high frequency satellite signals into a digital signal;

a digital circuit attached to the substrate that receives the digital signal from the analog circuit and processes said digital signal to compute positional coordinates of said GPS antenna;

an interface connector attached to the substrate that receives the positional coordinates and outputs said positional coordinates to an external device;

an electromagnetic interference shield formed from a metal into a housing which surrounds said substrate as well as at least said digital circuit on said substrate to block a noise developing at said digital circuit from interfering with said GPS antenna,

said GPS antenna being directly supported on the electromagnetic interference shield so as to define said ground plane only by said electromagnetic interface shield, said patch being electrically insulated from said electromagnetic interference shield.