Filtronic Lk Oy

Lk Products Oy

Suvi Tarvas

Jyrki Mikkola

Anne Isoh&auml;t&auml;l&auml;

Petteri Annamaa

Sauli Kivel&auml;

Kimmo Antila

Mari Panuma

Mari Paunuma

A multiband antenna applicable as an internal antenna in small mobile terminals especially. The antenna ( ) is a PIFA placed inside the housing of a mobile station with at least two operating bands. A first resonance falling into a lower operating band is produced by means of a radiating conductive pattern (B ) in planar element ( ). To improve the characteristics of the antenna in the upper operating band the planar element further comprises a slot ( ) which goes between the feed point (F) and the short-circuit point (S) of the antenna. The radiator provided by this slot can be considered a quarter-wave slot radiator or a half-wave loop radiator. The PIFA further may have another radiator, which resonates in the upper operation band. By means of said slot the upper operating band of an antenna can be widened or the radiation in the horizontal plane in the upper operating band can be made more effective.

Internal multiband antenna

The invention relates to a multiband antenna which finds utility particularly in mobile stations. The antenna structure includes a PIFA-type antenna positioned inside the covers of a mobile station, which antenna includes a slot radiator ( ). In the planar element there is a second slot ( ) so that, viewed from a feed point (F), two radiating conductive branches (B B ) of different lengths are formed. Each of the three radiators has a separate operating band of its own. The structure also includes a whip element ( ) movable with respect to the PIFA part. When the whip element is pulled out, its lower end is galvanically coupled with the shorter branch of the planar element, with its relatively narrow side branch (B ). The whip enhances the operation of the antenna especially in the lowest operating band. The influence of the pulled-out whip on the location of the uppermost operating band is compensated for by a third slot ( ) in the planar element. Matching for the whip element is provided by shaping the conductive patterns existing in the planar element in any case. The structure is relatively simple and economical to fabricate. A good three-band planar antenna can be provided without a whip element as well.

Multiband antenna

A double-action antenna structure includes, e.g. a PIFA-type antenna inside the casing of a mobile station, a coupling element and a moveable whip element. The coupling element is a relatively small conductive element between the radiating plane and ground plane of the PIFA, galvanically isolated from the radiating plane and ground plane. When the whip element is retracted, it has no significant coupling to the PIFA parts. When the whip element is extended, its lower end is galvanically connected to the coupling element so that a significant electromagnetic coupling is established between the whip element and the radiating plane of the PIFA. Thus the whip element is fed through the PIFA without being in galvanic contact with it. The coupling element further provides for the matching of the whip element. The internal and external antennas may be designed and optimized relatively independently of each other.

Double-action antenna

The invention relates to an antenna structure ( ) to be placed inside in particular small radio apparatus. A conventional PIFA-type structure is extended by arranging a structural part ( ) adding to the capacitance between the radiating plane ( ) and ground plane ( ) relatively close to the feed point (F) of the antenna. The structural component may be a projection extending from the radiating plane towards the ground plane or vice versa. An advantage of the invention is that it achieves a significant increase in the antenna bandwidth without increasing the size of the antenna. Another advantage of the invention is that the structure according to it is simple and the increase in the manufacturing costs is relatively low.

Planar antenna

The invention relates to double-action antenna structures. The structure comprises an antenna inside the covering of a mobile station, a switch (SW) and a whip, element ( ) movable in relation to the former two. The internal antenna comprises two elements the first of which ( ) is connected to the feed conductor ( ) of the whole antenna structure and the second to the signal ground ( ). When the whip element is retracted, the said switch galvanically interconnects the elements of the internal antenna. Thus only the internal antenna functions and the whip has no practical significance. When the whip element is extended, its lower end disconnects, by means of the switch, the elements of the internal antenna, and the whip element itself is connected in series with the first element. Thus, a radiating element is provided by the series connection ( ) of the whip and the first element, and the shorted element ( ) of the internal antenna has no practical significance. The first element further provides for the matching of the whip element. The antenna structure may have one or more operating bands. In the structure according to the invention the length of the whip element may be chosen relatively freely because the electrical length of the structure can always be made suitable by means of the internal antenna element connected in series with the whip element. No mechanical parts or components are needed for the matching of the whip element.

A planar antenna comprises a planar radiating element ( ) formed of a conductive area confined by a substantially continuous border line. The conductive area is split by a gap which divides the planar radiating element into a first branch and second branch such that both the first and the second branch have an outermost end. The gap has a head end on said substantially continuous border line and a tail end within the conductive area. At its head end ( ) the gap has a certain first direction and at another point ( ) a certain second direction which differs from the first direction by more than 90 degrees when the directions are defined along the gap from the head end towards the tail end. The outermost end of the second branch, confined by the gap, is located within the continuous border line, surrounded by the first branch.

Planar antenna with two resonating frequencies

The invention relates to dual mode antennas particularly suitable for mobile stations. The antenna structure comprises an antenna (,) of the PIFA type which is located within the covers of the mobile station, and a whip element (,) which is movable relating to the PIFA antenna. The PIFA can be a single band or a dual band antenna. When the whip element is extracted its lower end (,) forms a galvanic or capacitive coupling with the radiating element (,) of the PIFA. If the PIFA is a single band antenna the extracted whip element substantially changes the resonant frequency of the PIFA, so that the whip is left as the radiating element at the operating band. If the PIFA is a dual band antenna, then an extracted whip alone, or the whip and the planar element of the PIFA together, functions as the radiating element at one operating band, and at the other operating band the planar element of the PIFA operates as the radiating element. The feeding and the matching of the whip element is arranged by the PIFA without any separate additional components. With the aid of the invention the best properties of both the PIFA and the monopole antenna can be utilised. The structure is further reliable and it has relatively low costs.

Antenna structure

A PIFA structure has a first operating frequency and a second operating frequency. It comprises a planar radiating element (,) which is a conductive area confined by a substantially continuous border line divided by a non-conductive slot (,). The slot has a first end on said substantially continuous border line and a second end within the conductive area. The planar radiating element comprises a feedpoint (,) and ground contact (,) near the first end of the slot so that the electrical length of the conductive area divided by the slot, measured at the feedpoint, equals a quarter of the wavelength at the first operating frequency and the electrical length of the slot equals a quarter of the wavelength at the second operating frequency.

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Oulu, Finland

Suvi Tarvas