Communications assembly and antenna assembly with a switched tuning line

An antenna radiator assembly (201) and radio communications assembly (200) comprising a circuit board (210) supporting electrical conductors (225), one of the electrical conductors (225) being coupled to a feed point (130), and the circuit board (210) having a ground plane (140) formed from at least one conductive sheet. There is a tuning plate (132), a parasitic tuning line (150), a switching unit (160) selectively electrically coupling the tuning plate (132) to the tuning line (150). There is also an antenna radiator element (107) spaced from the circuit board (210) and coupled to the feed point (130), and when viewed in plan view there is an overlapping area where an overlapping surface area of the antenna radiator element (107) overlaps an overlapping surface area of the circuit board (210) thereby forming a sandwiched dielectric region therebetween, the sandwiched dielectric region providing capacitive coupling of the tuning plate (132) and the antenna radiator element (107); and a ground connector (131) inductively coupling the antenna radiator element (107) to the ground plane (140), wherein the tuning plate (132) is disposed in the overlapping surface area of the circuit board (210).

FIELD OF THE INVENTION

This invention relates to an antenna assembly and radio communications assembly including an antenna assembly. The invention is particularly useful for, but not necessarily limited to, multi-band wireless communication devices with internal antennas.

BACKGROUND ART OF THE INVENTION

Wireless communication devices often require multi-band antennas for transmitting and receiving radio communication signals often called Radio Frequency (RF) signals. For example, network operators provide services on a GSM system in a 900 MHz frequency band typically used in Asia also use a DCS system in a 1800 MHz frequency band typically used in Europe. Accordingly, GSM wireless communication devices, such as cellular radio telephones, should have dual band antennas to be able to effectively communicate at least at both of these frequencies. Also, in certain countries service providers operate on 850 MHz or 1900 MHz frequency bands. Accordingly, GSM wireless communication devices, such as cellular radio telephones, should have multi band antennas to be able to effectively communicate on more than one of these frequency bands.

Current consumer requirements are for compact wireless communication devices that typically have an internal antenna instead of an antenna stub that is visible to the user. Small cellular telephones now require a miniaturized antenna comprising an antenna radiator structure coupled to a ground plane, the ground planes being typically formed on or in a circuit board of the telephone. Further, the antenna radiator structure is installed inside the phone where congested conductive and “lossy” components are placed nearby. The antenna must therefore preferably be able to cover multiple frequency bands to, for instance, accommodate the 850 Mhz, 900 MHz, 1800 Mhz, 1900 Mhz bands whilst being compact.

Internal antenna radiator structures, such as a Planar Inverted F Antenna (PIFA) or Planar Inverted L Antenna (PILA), that use a radiator element in the form of a micro-strip internal patch antenna, are considered advantageous in several ways because of their compact lightweight structure, which is relatively easy to fabricate and produce with precise printed circuit techniques capable of integration on printed circuit boards.

Internal antenna radiator elements (patch antennas) are typically spaced from circuit board and when viewed in plan view at least most of a surface area of the antenna radiator element overlaps a surface of the circuit board forming a sandwiched region. This sandwich region is filled with one or more dielectric mediums including air and the mount (typically made of plastics) for the radiator element. The antenna's characteristics and performance may be affected by ground planes and signal lines on or in the circuit board that also overlap the antenna radiator element. Also, most known internal patch antennas tend to have a narrow bandwidth, unless their radiator element is sufficiently spaced from the ground plane. One solution to reduce the affects of ground planes, signal lines and also improve the antenna's bandwidth characteristics is to space the antenna radiator element further away from the circuit board. However, this would inevitably result in a thicker device that may not be acceptable for portable communications devices that are tending to become smaller due to consumer requirements. Accordingly, a need exists for relatively compact internal antenna radiator assembly or structure.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided an antenna radiator assembly. The antenna radiator assembly has a circuit board formed with electrical conductors thereon, at least one of the electrical conductors being coupled to a feed point, the circuit board having a ground plane formed from at least one conductive sheet. A tuning plate formed from part of the conductive sheet and there is a parasitic tuning line and a switching unit selectively electrically coupling the tuning plate to the tuning line. There is at least one antenna radiator element spaced from the circuit board and coupled to the feed point, and when viewed in plan view there is an overlapping area where an overlapping surface area of the antenna radiator element overlaps an overlapping surface area of the circuit board thereby forming a sandwiched dielectric region therebetween, the sandwiched dielectric region providing capacitive coupling of the tuning plate and the antenna radiator element. A ground connector inductively couples the antenna radiator element to the ground plane, wherein the tuning plate is disposed in the overlapping surface area of the circuit board.

According to another aspect of the present invention there is provided a radio communications assembly. The radio communications assembly has a circuit board formed with electrical conductors thereon, at least one of the electrical conductors being coupled to a feed point, the circuit board having a ground plane formed from at least one conductive sheet. There is a tuning plate formed from part of the conductive sheet and there is also a parasitic tuning line and a switching unit selectively electrically coupling the tuning plate to the tuning line. There is also a transceiver coupled to at least one antenna radiator element via a radio frequency amplifier, the at least one antenna radiator element being spaced from the circuit board and coupled to the feed point, and when viewed in plan view there is an overlapping area where an overlapping surface area of the antenna radiator element overlaps an overlapping surface area of the circuit board thereby forming a sandwiched dielectric region therebetween, the sandwiched dielectric region providing capacitive coupling of the tuning plate and the antenna radiator element. A ground connector inductively coupling the antenna radiator element to the ground plane, wherein the tuning plate is disposed in the overlapping surface area of the circuit board.

DETAILED DESCRIPTION

With reference toFIG. 1, there is illustrated a radio communications device in the form of a radio telephone100comprising radio frequency communications circuitry102coupled to be in communication with a processor103. An input interface in the form of a screen105and a keypad106are also coupled to be in communication with the processor103. As will be apparent to a person skilled in the art the screen105can be a touch screen thereby eliminating the need for the keypad106.

The processor103includes an encoder/decoder111with an associated Read Only Memory (ROM)112storing data for encoding and decoding voice or other signals that may be transmitted or received by the radio telephone100. The processor103also includes a micro-processor113coupled, by a common data and address bus117, to the radio frequency communications circuitry102, encoder/decoder111, a character Read Only Memory (ROM)114, a Random Access Memory (RAM)104, static programmable memory116and a removable SIM module118. The static programmable memory116and SIM module118each can store, amongst other things, selected incoming text messages and a telephone book database.

The micro-processor113has ports for coupling to the keypad106, the screen105and an alert module115that typically contains a speaker, vibrator motor and associated drivers. The character Read only memory114stores code for decoding or encoding text messages that may be received by the communication circuitry102, input at the keypad106. In this embodiment the character Read Only Memory114also stores operating code (OC) for micro-processor113. As will be apparent to a person skilled in the art the radio telephone100also has a speaker and microphone and other components (not shown).

The radio frequency communications circuitry102is has a transceiver108coupled to both a radio frequency amplifier109and a combined modulator/demodulator110. There is also illustrated a radio frequency radiator element107that is directly coupled to the radio frequency amplifier109by a feed point130. Thus, the feed point130provides for electrically coupling a radio frequency antenna radiator element107to the radio frequency communications circuitry102. A ground connector131provides for inductively coupling the radio frequency radiator element107to a ground plane140and a there is also an overlapping tuning plate132inductively coupled to the ground plane140. In addition, there is a switching unit160coupled to the processor103by bus117, the switching unit160has switching terminals coupled to the overlapping tuning plate132and a parasitic tuning line150by respective connectors161,162.

Referring toFIG. 2there is illustrated a first preferred embodiment of a radio communications assembly200including an antenna radiator assembly201forming part of the radio telephone100. The radio communications assembly200comprises a circuit board210supporting the radio frequency amplifier109, the transceiver108, processor103switching unit160and a conductive plate or sheet (shown in phantom due to it being sandwiched in circuit board210) providing part of the ground plane140. There are also other typical components/modules (not shown for clarity) and other conductive plates may be provided and combined forming the ground plane140that are mounted to or electrically coupled the circuit board210. The radio frequency radiator element107is mounted to a dielectric mount230(typically formed from a thermoplastics material) that spaces the radio frequency antenna radiator element107from the circuit board210. The radio frequency antenna radiator element107is coupled to the transceiver108unit through: a) the feed point130, in the form of a spring loaded feed point pin (shown in phantom) that contacts an underside of the radio frequency antenna radiator element107through an aperture in the dielectric mount230; b) the radio frequency amplifier109; and c) electric conductors or runners225coupled to a feed point130(most runners on circuit board210are not shown).

From the above, it will be apparent that the antenna radio assembly201includes the a circuit board210with the electrical conductors225and feed point130, the tuning plate132, parasitic tuning line150, switching unit160antenna radiator element and ground connector131. Also, the radio frequency antenna radiator element107is spaced from the circuit board210and radio frequency antenna radiator element107is directly and inductively coupled to the ground plane140by the ground connector131in the form of a coupling strap and a conductive trace in the circuit board210(the trace is not shown). Accordingly, as will be apparent to a person skilled in the art, the antenna radiator assembly200as shown forms a Planar Inverted F Antenna structure (PIFA).

Referring toFIG. 3there is illustrated another perspective view of the radio communications assembly200including the antenna radiator assembly201, in this illustration the dielectric mount230and the radiator element are removed for illustrative purposes so not to obscure the illustration of the tuning plate132.

The switching unit160, controlled directly or indirectly by processor103, provides for electively electrically coupling the tuning plate132to the tuning line150by the terminals of the switching unit160that are coupled to the overlapping tuning plate132and a parasitic tuning line150by the respective connectors161,162. As illustrated, the tuning plate132is formed from part of the conductive sheet that forms the ground plane140and the tuning line150extends from a location near an edge of the tuning plate132. More specifically, in this embodiment the tuning line150is formed from part of the conductive sheet that forms the ground plane140and comprises at a first elongate finger322coupled to a second elongate finger324, wherein the second first elongate finger324is at a right angle to the first elongate finger322. Also, the tuning plate132has a surface area designated by a width W and Length L.

Referring toFIG. 4there is a plan view of part of the radio communications assembly200including the antenna radiator assembly201illustrating the spatial relationship of the radiator element107, the tuning plate132and tuning line150. In this plan view, the antenna radiator element107is spaced from the circuit board (seeFIG. 2) and when viewed in plan view there is an overlapping area where an overlapping surface area of the antenna radiator element107overlaps an overlapping surface area of the circuit board405thereby forming a sandwiched dielectric region therebetween. This sandwiched dielectric region providing capacitive coupling of: the overlapping tuning plate132with the antenna radiator element107; and the tuning line150with the antenna radiator element107. Furthermore, as shown, both the tuning plate132and tuning line150are disposed in the overlapping surface area400of the circuit board140. More precisely, in this embodiment all of the antenna radiator element107overlaps an overlapping surface area400of the circuit board140and as can be seen fromFIGS. 2 and 3, the first elongate finger322and second elongate finger324and tuning plate310are parallel to the antenna radiator element107, also the tuning plate310and tuning line320are coplanar. Also,FIGS. 2 to 4show the first elongate finger322is along an edge420of the overlapping surface area of the circuit board140and the second elongate finger324extends from the first elongate finger322into the overlapping surface area400of the circuit board140.

Referring toFIG. 5there is a plan view of part of a radio communications assembly500including part of an antenna radiator assembly501illustrating a second embodiment of the tuning plate505and tuning line520with a radiator element removed and the assembly500typically forms a PIFA. In this embodiment, the dielectric mount230and the radiator element are removed for illustrative purposes so not to obscure the illustration of the tuning plate505. The switching unit160provides for selectively electrically coupling the tuning plate505to the tuning line520by the terminals of the switching unit160that are directly mounted and coupled to the overlapping tuning plate132and a parasitic tuning line150without the need for runners or connectors161,162. As illustrated, the tuning plate505and tuning line510being formed from part of the conductive sheet that forms the ground plane140and the tuning line520extends from a location adjacent an edge of the ground plane140. More specifically, the tuning line520comprises a first elongate finger522coupled to a second elongate finger524, wherein the second first elongate finger524is at a right angle to the first elongate finger522. Also, the tuning plate510has a surface area designated by a width W and Length L.

Although not specifically illustrated in this plan view, the antenna radiator element107is spaced from said circuit board and so there is an overlapping surface area (indicated by box540) where an overlapping surface area of the antenna radiator element107overlaps an overlapping surface area of the circuit board thereby forming a sandwiched dielectric region therebetween. This sandwiched dielectric region providing capacitive coupling of the overlapping tuning resonator505and the antenna radiator element. Furthermore, as shown, the tuning plate505and tuning line520are both disposed in the overlapping surface area540of the circuit board140. More precisely, in this embodiment all of the antenna radiator element107typically overlaps an overlapping surface area540of the circuit board140and when the antenna radiator element107is coupled to the assembly, the first elongate finger522and second elongate finger524and tuning plate510are parallel to the antenna radiator element107, also the tuning plate505and tuning line520are coplanar. Also, as shown, the first elongate finger522is along an edge of the overlapping surface area of the circuit board140and the second elongate finger524extends from the first elongate finger522into the overlapping surface area of the circuit board140.

Referring toFIG. 6there is a plan view of part of a radio communications assembly600including part of an antenna radiator assembly601illustrating a third embodiment of the tuning plate505and tuning line520with a radiator element removed and the assembly600typically forms a PIFA. In this embodiment, the dielectric mount230and the radiator element are removed for illustrative purposes so not to obscure the illustration of the tuning plate605. The switching unit160provides for selectively electrically coupling the tuning plate605to the tuning line620by the terminals of the switching unit160one of which is directly mounted and coupled to the overlapping tuning plate132and another of which is coupled to the parasitic tuning line620by runner or connector162. As illustrated, the tuning plate605and tuning line620being formed from part of the conductive sheet that forms the ground plane140and the tuning line620extends from an a location adjacent an edge of the tuning plate605(however the tuning line620could extend from a location adjacent an edge of the ground plane140). In this embodiment, the tuning line620comprises at a meander. Also, the tuning plate605has a surface area designated by a width W and Length L.

Although not specifically illustrated in this plan view, the antenna radiator element107is spaced from said circuit board and so there is an overlapping surface area (indicated by box640) where an overlapping surface area of the antenna radiator element107overlaps an overlapping surface area of the circuit board thereby forming a sandwiched dielectric region therebetween. This sandwiched dielectric region providing capacitive coupling of the overlapping tuning plate605and the antenna radiator element. Furthermore, as shown, tuning plate605and tuning line620are disposed in the overlapping surface area640of the circuit board210. More precisely, in this embodiment all of the antenna radiator element107typically overlaps an overlapping surface area640of the circuit board. Furthermore, the tuning plate605and tuning line620are coplanar.

Referring toFIG. 7there is a perspective view of part of a radio communications assembly700including part of an antenna radiator assembly701illustrating a fourth embodiment of the tuning plate705and tuning line720with a radiator element removed and the assembly701typically forms a PIFA. In this embodiment, the dielectric mount230and the radiator element107are removed for illustrative purposes so not to obscure the illustration of the tuning plate705. The switching unit160provides for selectively electrically coupling the tuning plate705to the tuning line720, the tuning plate605being formed from part of the conductive sheet that forms the ground plane140. The tuning line720is mounted on the switching unit160and part of the tuning line720, when viewed in plan view, overlaps the overlaps the tuning plate605. As illustrated, the switching unit160and tuning line720are disposed in the overlapping surface area of the circuit board210, more specifically the tuning line720is mounted on an upper surface of the switching unit160, thus the tuning line720is directly over switching unit160. This provides for selectively electrically coupling the tuning plate705to the tuning line720, without the need for runners or connectors161,162, by the terminals of the switching unit160being directly mounted and coupled to the overlapping tuning plate705and a parasitic tuning line720.

Although not specifically illustrated in this plan view, the antenna radiator element107is spaced from said circuit board and so there is an overlapping surface area (indicated by box640) where an overlapping surface area of the antenna radiator element107overlaps an overlapping surface area of the circuit board thereby forming a sandwiched dielectric region therebetween. This sandwiched dielectric region providing capacitive coupling of the overlapping tuning plate605and the antenna radiator element. Furthermore, as shown, tuning plate605and tuning line620are disposed in the overlapping surface area640of the circuit board140. More precisely, in this embodiment all of the antenna radiator element107typically overlaps an overlapping surface area640of the circuit board. Furthermore, the tuning plate605and tuning line620are coplanar.

Advantageously, the present invention provides for compact, economic multi band internal antenna radiator assembly and a radio communications assembly capable of operating at multiple specified bands. In this regard, the configuration of the tuning resonator and its coupling and positioning with the antenna radiator element provides for a relatively small distance therebetween, and this can result in a thin a form factor. It should be noted that the tuning plate typically, in some embodiments, occupies less than 70% of the overlapping surface area of the circuit board. Also, as will be apparent to a person skilled in the art, in operation the tuning resonator is a quarter electrical wavelength resonator. In use, the present invention can operate at the 1900 MHz and 900 MHz bands and when the switching unit160electrically couples the tuning line150to the tuning plate132loading occurs and the frequency bands are modified (switched) to 1800 MHz and 850 MHz respectively.