Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
1999-11-03
2001-08-28
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000, C343S878000, C343S906000
Reexamination Certificate
active
06281844
ABSTRACT:
FIELD OF THE INVENTION
The invention generally relates to situations, where the ground plane of an electrical component and the ground plane of an electrical circuit module, which form an electrical device, are to be connected. In particular, the invention relates to the problem, how the ground plane of an electrical component, e.g. a microstrip patch antenna, a filter, or a power amplifier, can be connected to a grounding plane of a circuit board, e.g. a printed circuit board or a multilayer circuit board. More specifically, the invention addresses the problem, how the grounding planes can be connected, while an extremely efficient utilization of the board area as well as good mounting properties, e.g. a good reflow solderbility with little remaining stresses, can be achieved.
U.S. Pat. No. 5,517,612 describes that a dielectric resonator block can be connected to a mounting substrate using solder bumps.
Here, the input and output electrodes are to be connected to conductor patterns on the mounting substrate. Patent Abstracts of Japan, Volume 95, No. 10, Nov. 8, 1995 and JP 07 183 330 A relate to a method for connecting semiconductor devices to a wiring board. Here, grounding electrode pads are formed on the entire surface of the semiconductor device containing circuit pattern regions other than the electrode pads for signal transmission lines.
DE 195 20 700 A1 shows that a chip contact area is exposed from an epoxy housing and is connected to a conductor structure via a plurality of solder contact bumps.
U.S. Pat. No. 5,635,942 relates to a microstrip antenna where the grounding plane is soldered to a circuit pattern which is provided on the printed circuit board.
EP O 588 465 11 relates to a ceramic dielectric for antennas. A configuration is shown which is very similar to what will be described as prior art in
FIG. 3
of the present application.
U.S. Pat. No. 5,410,449 discloses the usage of a solder layer and platforms in order to connect the heat sink to the substrate. On the surface of the substrate a conductor pad forms an electrically conductive path.
Patent Abstracts of Japan, Vol. 98, No. 9, Jul. 31, 1988 and JP 10 093 474 A relate to an antenna multicoupler. A plurality of bumps are provided at the rear side of a multilayer substrate of an antenna multilayer to maintain a fixed interval from a grounded surface of a mounted substrate.
Although the invention considers any device comprising an electrical component and an electrical circuit module interconnected at their ground planes, the invention particularly relates to the interconnection of such units in GPS (GPS=Global Positioning System) modules and/or mobile telephones with such GPS functionalities. For example, if a microstrip patch antenna is used as part of a GPS (Global Positioning System) receiver incorporated in a mobile telephone, space constraints are very severe and any available space on the circuit board of the mobile telephone should be used as efficiently as possible.
BACKGROUND OF THE INVENTION
FIG. 1
shows a device DEV comprising an electrical circuit module MO and at least one electrical component CO. The electrical circuit module MO comprises a base
1
and a metallized ground plane
2
which is for example made of aluminium or copper. The electrical component CO also comprises a base
3
and a metallized ground plane
4
. The two ground planes
2
,
4
are to be brought into contact with each other, as indicated with the arrow in FIG.
1
. If for example the electrical component is a patch antenna, the ground plane
2
should normally have a size 3-times of the size of the ground plane
4
of the electrical component CO to achieve an effective grounding. The portion
5
can comprise other circuit components
6
which are interconnected via a conductor pattern
7
.
It should be noted that the electrical component CO can in principle be any component which requires the connection to a ground plane as for example provided by the electrical circuit module MO. Such grounding problems often occur in high frequency circuits, for example when the electrical circuit module is a high frequency circuit. An example for the electrical component CO is a micro-strip patch antenna, in particular a ceramic patch antenna.
FIG. 3
shows the principle structure of such a ceramic patch antenna as generally known in the art and described in “CAD of micro-strip antennas for wireless applications” by Robert A. Sainati, Artech House, INC., 1996, ISBN 0-89006-562-4, pages 1-5, 18, 19 and 50, 51.
FIG. 3
a
shows a cross sectional view of such a ceramic patch antenna,
FIG. 3
b
is a bottom view and
FIG. 3
c
is a perspective view. Ordinary patch antennas consist of rectangular or round slices of a ceramic material
3
with a preferrably high dielectric constant ∈
r
. Furthermore, a conducting layer pattern
11
is provided on the upper surface and a ground plane
4
is provided on the lower surface. Typically, the conducting layer pattern
11
is rectangluar or squared in shape or consists of a pattern of single stripes depending on the desired radiation pattern.
In order to feed energy to the conducting layer
11
, the ground plane
4
has an opening
13
through which a feeding pin
12
extends. The feeding pin
12
can be soldered to the conducting layer pattern
11
. Therefore, when the component CO is constituted by such a ceramic patch antenna as is shown in
FIG. 3
, when mounting the component CO to the electrical circuit module MO, also the circuit module MO (cf. FIG.
1
), i.e. the circuit board, has a corresponding opening in its ground plane
2
in order to avoid a short circuit. Energy is then fed to the feeding pin from a lower layer of the multilayer board MO.
In a mobile telephone such a ceramic patch antenna is for example used as part of a GPS receiver. Therefore, when mounting such a component CO onto the electrical circuit module MO, the available space must be used as efficiently as possible and furthermore, from a manufacturing point of view, an easy mounting technique should be used. Generally, the antenna characteristic is mainly determined by the mechanical dimensions of the conducting layer
11
and the substrate
3
as well as the substrate properties.
Regarding the efficient use of the available space, substrates
3
with a high dielectric constant ∈
r
lead to reductions in size, because the effective wavelength &lgr;
e
diminishes according to the equation &lgr;
e
=&lgr;
O
/{square root over (∈
r
+L )} (&lgr;
0
=free space wavelength, {square root over (∈
r
+L )}=shortage factor). Thus, with increasing dielectric constant ∈
r
, the effective wavelength &lgr;
e
decreases. For decreasing values of &lgr;
e
, the area of the conducting layer
11
can in general be reduced. On the other hand, for a proper operation, a ceramic patch antenna requires a ground plane
2
in the module
110
which should be around 3-times larger than the ceramic substrate
3
.
As shown in
FIG. 2
, typically the circuit module MO is constituted by a multilayer board (here a 6 layer board) where conductor patterns
5
1
,
5
2
,
5
3
may be provided on several levels, possibly with intermediate insulation layers
10
1
,
10
2
. In such multilayer board configurations, generally through-holes
8
as well as blind-holes
9
1
,
9
2
are used. The through-holes
8
may connect all conductor patterns of all levels by means of a metallization which is applied to the inside walls of the hole
8
. On the other hand, blind holes
9
only connect two or more layers without extending through all layers. It is clear from
FIG. 2
that in the conventional configuration, there is no possibility to use the large area (called the restricted area in
FIG. 2
) directly underneath the ceramic patch antenna for through-holes or routing purposes for signals not having a ground potential, since all signals would invariably be short-circuited to the ground plane
4
of the electrical component CO, if the through-hole would be placed in the restricted area (the inside metallization i
Bäuerlein Frank
Kodim Walter
Burns Doane Swecker & Mathis L.L.P.
Telefonaktiebolaget LM Ericsson (publ)
Tran Thuy Vinh
Wong Don
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