Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2001-07-03
2002-12-17
Le, Hoanganh (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C343S846000
Reexamination Certificate
active
06496148
ABSTRACT:
The present invention relates generally to radio transmitters, in particular mobile telephones, and more particularly to antennas for inclusion in such transmitters and including a conductive layer.
BACKGROUND OF THE INVENTION
This kind of antenna includes a patch which is typically obtained by etching a metal layer. It is then called a microstrip patch antenna.
The microstrip technique is a planar technique that is used to make transmission lines for transmitting guided waves, possibly carrying signals, and antennas coupling such lines and radiated waves. It uses conductive patches and/or strips formed on the top surface of a thin dielectric substrate. A conductive layer extends over the bottom surface of the substrate and constitutes an earth layer of the line or the antenna. The patch is typically wider than the strip and its shape and dimensions are important characteristics of the antenna. The substrate is typically a plane rectangular sheet of constant thickness and the patch is also typically rectangular. This is not obligatory, however. In particular, it is known in the art that varying the thickness of the substrate can enlarge the bandwidth of this kind of antenna and that the patch can be various shapes, for example circular. The electric field lines extend between the strip or the patch and the earth layer through the substrate. A transmission line operating in the above manner is referred to hereinafter as a microstrip line.
The above technology differs from coplanar technologies that also use conductive elements on a thin substrate, and in particular the transmission line technology in which the electric field is established on the top surface of the substrate and symmetrically between a central conductive strip and two conductive lands on respective opposite sides of the strip, from which they are separated by respective slots. A transmission line operating in this manner is referred to hereinafter as a coplanar line. In an antenna using this technology, a patch is surrounded by a continuous conductive land from which it is separated by a slot.
In another coplanar technology, a transmission line is formed by a slot in a conductive layer and the electric field of the transmitted wave is established in the plane of that layer between the two edges of the slot.
Antennas using the above technologies typically (although not necessarily) constitute resonant structures in which standing waves are established that provide coupling with waves radiated in space.
Various resonant structures of the above kind can be made, for example using the microstrip technology, and each such structure can support one or more resonant modes, referred to for brevity hereinafter as “resonances”. Broadly speaking, each resonance can be defined as a standing wave formed by the superposition of two travelling waves propagating along the same path in opposite directions and resulting from alternating reflection at the two ends of the path of the same travelling wave, which is an electromagnetic wave propagating along that path in a line consisting of the earth layer, the substrate and the patch, for example. The path is imposed by the components of the antenna. It can be rectilinear or curved. It is referred to hereinafter as the “resonance path”. The resonant frequency is inversely proportional to the time taken by the travelling wave referred to above to travel this path.
In a first type of resonance, which is referred to as “half-wave” resonance, the length of the resonance path is typically substantially equal to one half-wavelength, i.e. to half the wavelength of the travelling wave referred to above. The antenna is then referred to as a ““half-wave” antenna. This type of resonance can be generally defined by the presence of an electrical current node at each of the two ends of a path of this kind, whose length can therefore also be equal to said half-wavelength multiplied by an integer other than one, and typically an odd number. The two ends of the path are located in regions in which the amplitude of the electrical field that is applied via the substrate, for example, is at a maximum; coupling with the radiated waves occurs at one or both ends of the path.
A second type of resonance that can be obtained using the same technology is referred to as “quarter-wave” resonance and differs from half-wave resonance firstly in that the resonance path typically has a length equal to one quarter-wavelength, i.e. one quarter of the wavelength defined above. To this end the resonant structure must include a short circuit at one end of the path, the term “short circuit” referring to a connection between the earth layer and the patch. The short circuit must have a sufficiently low impedance to impose the resonance. This type of resonance can be generally defined by the presence of an electric field node fixed by this kind of short circuit in the vicinity of an edge of the patch and by an electrical current node at the other end of the resonance path. The length of the resonance path can therefore be equal to an integer number of half-wavelengths added to said quarter-wavelength. Coupling with waves radiated in space occurs at an edge of the patch, in a region where the amplitude of the electric field is sufficiently high.
Other types of resonance can be established, each characterized by a distribution of the electric and magnetic fields that oscillate in an area of space including the antenna and its immediate vicinity. They depend in particular on the configuration of the patches, which can incorporate slots, possibly radiating slots. In the case of microstrip antennas, the resonances are also conditioned by the presence and location of any short circuits and by the electrical models representing the short circuits if the latter are imperfect, i.e. if they cannot be considered even approximately equivalent to perfect short circuits of zero impedance.
The presence of an imperfect short circuit in an antenna can cause a resonance having what is referred to as a virtual node, which occurs when the following conditions are met (in what follows, the antenna discussed above is referred to as the “first antenna”):
The distribution of fields in the first antenna is substantially identical to a distribution that can be induced in an identical area of the patch of a second antenna.
The second antenna is identical to the first antenna, within the limits of the area, except that the second antenna has no short circuit.
The patch of the second antenna extends not only over the area already mentioned, which then constitutes a principal area of the second antenna, but also over an additional area.
Finally, the field distribution in question in the principal area of the second antenna is accompanied by an electric or magnetic field node in the additional area.
In order to describe the resonance occurring in the first antenna, the node occurring in the second antenna can be considered to constitute a node for the resonance of the first antenna also. For an antenna such as the first antenna this kind of node is referred to hereinafter as a “virtual” node, because it is located in an area outside the patch of the antenna and in which there is therefore no electric or magnetic field enabling the presence of the node to be determined directly.
Although these “virtual nodes” are not conventionally taken into account in those terms when describing resonances, they are implied by the distinction that is sometimes made between the physical or geometrical length of the patch and its so-called “electrical” length. In the case of the two antennas considered above, the physical or geometrical length of the patch of the first antenna would be that of the patch, but the electrical length of the patch would in fact be the physical or geometrical length of the patch of the second antenna.
An antenna is typically coupled to a signal processor such as a transmitter by a connection system including a connection line which is external to the antenna and terminates in a coupling system integrated into the antenna for coupling the lin
Coupez Jean-Philippe
Kouam Charles Ngounou
Alcatel
Le Hoang-anh
LandOfFree
Antenna with a conductive layer and a two-band transmitter... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Antenna with a conductive layer and a two-band transmitter..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Antenna with a conductive layer and a two-band transmitter... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2954555