Communications: radio wave antennas – Antennas – With radio cabinet
Reexamination Certificate
2003-08-12
2004-11-16
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With radio cabinet
C343S7000MS, C343S850000
Reexamination Certificate
active
06819293
ABSTRACT:
The invention relates to an apparatus with a radio communication function, comprising a carrier having a first and an opposite, second side and provided with a ground conductor, at which first side an antenna device is present, which antenna device comprises a substrate having a first and an opposite, second side and an antenna present at the first side of the substrate and having an input impedance, the apparatus further comprising means for tuning said input impedance.
The invention also relates to an antenna device.
The invention further relates to a carrier having a first and an opposite, second side and provided with a ground conductor.
The invention also to a method of tuning an antenna of an apparatus with a radio communication function, which apparatus comprises a carrier with a ground conductor and an antenna device comprising a substrate and the antenna, which method comprises the steps of measuring an input impedance and adapting the input impedance.
Such an apparatus, such an antenna device and such a method are known from WO-A 00/03453. The known antenna is of the PIFA type and substantially consists of a metal strip. The metal strip of the known antenna device is provided with ground terminal and an input terminal. Between said terminal a matching bridge is present. Tuning of the antenna is performed by measuring or estimating the input impedance associated with the antenna and subsequently matching the input impedance through adjustment of the length of the matching bridge. Tuning of the antenna is necessary for each specific application, i.e. each apparatus with its own design.
It is a disadvantage of the known antenna device that it must be modified for each application. This precludes the use of standardized antenna devices.
It is therefore a first object of the invention to provide an apparatus of the kind mentioned in the opening paragraph of which the antenna can be tuned without significant modification of the antenna device.
It is a second object of the invention to provide an antenna device of the kind mentioned in the opening paragraph which can be used in various applications without any further substantial modifications.
It is a third object of the invention to provide a carrier that can be used in the apparatus of the invention.
It is a fourth object of the invention to provide a method of the kind mentioned in the opening paragraph, by which the antenna can be tuned without significant modification of the antenna device.
The first object is achieved in that said means comprise a first and a second matching bridge that comprise a reactive component and a switch, and that are connected between the antenna and the ground conductor. In the present invention, the input impedance is adjusted by switching at least one of the switches on or off. Due to the inclusion of the switch in each of the matching bridges, the matching of the input impedance is converted from an analogue into a digital operation. Although the number of matching bridges can be relatively small, the resulting tuning is sufficiently good. Furthermore, the inclusion of the switch in each of the matching bridges allows the provision of the switch in a different location than the reactive component. In particular the switch is provided in a location, where it is well accessible after the antenna device has been placed on the carrier, for instance a printed circuit board. Such location are, for example, an outer surface of the printed circuit board and an outer surface of the antenna device.
If the reactive components are capacitors, the matching bridges are connected in parallel. The matching bridges with capacitors can be attached to the antenna in any location, but preferably are attached to one end of the antenna, whereas a ground terminal connecting the antenna to ground is present at another end of the antenna. If the antenna is of the patch or PIFA type, the capacitors preferably comprise a dielectric material with a relatively high dielectric constant. Capacitors with a dielectric constant of about 80 relative to vacuum and with a good temperature stability of the capacitance are commercially available. If the reactive components are inductors, they are preferably connected in series, whereas the switches of the matching bridges are connected in parallel.
In a preferred embodiment, the reactive components of the first and second matching bridges are capacitors, and the matching bridges are connected in parallel. This has the advantage that the input impedance can be tuned over a relatively broad range. If, for example, a first, a second and a third matching bridge are present and—as is preferable—the reactive components each have a different value, the input impedance can be adjusted to eight different values.
In a further preferred embodiment, a resonant circuit is connected between the antenna and the ground conductor. It has been observed that the presence of a resonant circuit provides a greater bandwidth. An advantage of this is that less tuning is necessary. Another advantage is that the combined presence of a greater bandwidth and the matching bridges allows the matching bridges to be used for fine-tuning. The reactive components may be chosen accordingly. A further advantage is that due to the connection of the resonant circuit the behavior of the antenna is modified so as to provide a dual band operation without the need for switching. Such is known from the non-prepublished application with number GB0013156.5 (PHGB000065).
The matching bridges may be present at the carrier, from where they are connected to one point on the antenna. Alternatively, the matching bridges may be present at the antenna device and are connected to the ground conductor through a single connection to the printed circuit board. Furthermore, an extension of the ground conductor may be present in the antenna device, for example in the substrate. It is preferable however that a first module contact pad forming part of the first matching bridge and a second module contact pad forming part of the second matching bridge are present at the second side of the substrate; and that a first board contact pad forming part of the first matching bridge and a second board contact pad forming part of the second matching bridge are present at the first side of the carrier. In this embodiment, connections to the ground conductor at the carrier are individualized. An advantage of this embodiment is that a standardized antenna device can be used for many applications. Said contact pads are preferably part of Ball Grid Arrays or Land Grid Arrays, so that a board contact pad and a complementary module contact pad are connected without an additional manufacturing step.
Any component with which the matching bridge can be disconnected or connected at least once may be used a switch. Electrically driven switches such as micro-electromechanical switches, actuators and transistors may be used. The switches may also be embodied so as to be remotely controlled, for example in response to a radio wave receiving state. In this embodiment, the remote, controlling part of the switch is easily accessible, whereas the actual switching part is provided anywhere in- or outside the antenna device. Furthermore, the switch may be embodied as a track, for example a track of which the conductivity can be changed with laser radiation. This track may contain a material having an amorphous and a crystalline state, such as the material aluminum-germanium.
In an advantageous embodiment, the switch substantially consists of a conductive track that can be cut through mechanically, optically or—as a fuse—electrically. Such a switch may be integrated in the pattern of conductive tracks at an outer surface of the carrier. Dimensions of the conductive track acting as a switch will depend on the application and the way of disconnecting. In an alternative embodiment, the switch consists of a pair of component pads at the carrier. By placing an SMD-component with a minimal resistance onto said component pads, a matching bridge is electrically connected to
Koninklijke Philips Electronics , N.V.
Phan Tho
Waxler Aaron
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