Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
  • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
  • H01Q3/24—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
  • H01Q3/247—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching by switching different parts of a primary active element
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
  • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
  • H01Q1/242—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/06—Details
  • H01Q9/14—Length of element or elements adjustable
  • H01Q9/145—Length of element or elements adjustable by varying the electrical length

Definitions

• the present invention generally relates to the field of antennas and particularly to an antenna device for transmitting and receiving radio waves, to a radio communication device comprising said antenna device, and to a method for transmitting and receiving radio waves, respectively.
• the antenna When manufacturing a hand-portable telephone today the antenna is commonly adapted to the characteristics of this specific telephone and to be suited for a default use in a default environment. This means that the antenna can not later on be adapted to any specific condition under which a certain telephone is to be used or to suit a different hand-portable telephone. Thus, each model of a hand-portable telephone must be provided with a specifically designed antenna, which normally can not be optionally used in any other telephone model.
• the radiating properties of an antenna device for a small-sized structure depends heavily on the shape and size of the support structure such as a printed circuit board (PCB) of the device and of the telephone casing.
• All radiation properties such as resonance frequency, input impedance, bandwidth, radiation pattern, gain, polarization, and near-field pattern are a product of the antenna device itself and its interaction with the PCB and the telephone casing.
• all references to radiation properties made below are intended to be for the whole device in which the antenna is incorporated.
• the antenna device of the invention is applicable on a broad scale in various communication devices.
• Receiving antennas with diversity functionality, whereby adaptation to various radio wave environments is performed, are known through e.g. EP-A2-0, 852, 407 , GB-A-2, 332, 124 and JP-A- 10,145,130.
• Such diversity functionality systems may be used to suppress noise, and/or undesired signals such as delayed signals, which may cause inter-symbol interference, and co-channel interfering signals, and thus improve the signal quality in total, but requires a complex receiver circuitry structure, including multiple receiver chains, and a plurality of antenna input ports.
• WO 99/44307 discloses a communication apparatus with antenna-gain diversity.
• the apparatus comprises a first and a second antenna element, of which both or only one can be coupled to an antenna- signal node.
• the antenna element not coupled to the node is elec- trically coupled to signal ground.
• EP-A1-0, 546, 803 discloses a diversity antenna comprising a single antenna element.
• the antenna element is in the form of a quarter wave monopole, which can be fed alternately at one end or the other from a common RF feed source.
• US-Al-5, 541, 614 discloses an antenna system including a set of center-fed and segmented dipole antennas embedded on top of a frequency selective photonic bandgap crystal. Certain characteristics of the antenna system can be varied by connecting/disconnecting segments of the dipole arms to make them longer or shorter, for instance.
• an antenna structure is intended to include active elements connected to the transmission (feed) line(s) of the radio communication device circuitry, as well as elements that can be grounded or left disconnected, and hence operate as e.g. directors, reflectors, impedance matching elements, and the like.
• Fig. 1 displays schematically a block diagram of an antenna module for transmitting and receiving radio waves according to an embodiment of the present invention.
• Fig. 2 displays schematically receiving or transmitting antenna elements and a switching device for selectively connecting and disconnecting the receiving antenna elements as part of an antenna module according to the present invention.
• Fig. 3 displays schematically a receiving or transmitting antenna structure and a switching device for selectively grounding said receiving antenna structure at a variety of different points as part of an antenna device according to the present invention.
• Fig. 4 is a flow diagram of an example of a switch-and-stay algorithm for controlling a switching device of an inventive antenna device.
• Fig. 5 is a flow diagram of an alternative example of an algorithm for controlling a switching device of an inventive antenna device.
• Fig. 6 is a flow diagram of a further alternative example of an algorithm for controlling a switching device of an inventive antenna device.
• Fig. 7 displays schematically receiving or transmitting antenna elements and a switching device for selectively connecting and disconnecting the receiving antenna elements as part of an antenna module according to yet a further embodiment of the present invention.
• an antenna device or module 1 according to an embodiment of the present invention comprises separated transmitter (TX) 2 and receiver (RX) 3 RF sections.
• Antenna module 1 is the high frequency (HF) part of a radio communication device (not shown) for transmitting and receiving radio waves.
• antenna module 1 is preferably arranged to be electrically connected, via radio communications circuitry, to a digital or analogue signal processor of the radio communication device .
• Antenna module 1 is preferably arranged on a carrier (not shown) , which may be a flexible substrate, a MID (molded interconnection device) or a PCB.
• a carrier not shown
• Such an antenna module PCB may either be mounted, particularly releasably mounted, together with a PCB of the radio communication device side by side m substantially the same plane or it may be attached to a dielectric supporting means mounted e.g. on the radio device PCB such that it is substantially parallel with it, but elevated therefrom.
• the antenna module PCB can also be substantially perpendicular to the PCB of the radio communications device.
• Transmitter section 2 includes an input 4 for receiving a digital signal from a digital transmitting source of the radio communication device.
• Input 4 is via a transmission line 5 connected to a digital to analogue (D/A) converter 6 for converting the digital signal to an analogue signal.
• Converter 6 is further, via transmission line 5, connected to an upconverter 7 for upconvertmg the frequency of the analogue signal to the desired RF frequency.
• Upconverter 7 is m turn connected to a power amplifier (PA) 8 via transmission line 5 for amplification of the frequency converted signal.
• Power amplifier 8 is further connected to a transmitter antenna device 9 for transferring the amplified RF signal and for radiating RF waves in dependence on the signal.
• a filter (not shown) may be arranged in the signal path before or after the power amplifier.
• a device 10 for measuring the voltage standing wave ratio (VSWR) in the transmitter section is connected m transmitter section 3, preferably as in Fig. 1 between power amplifier 8 and transmitter antenna device 9, or incorporated m transmitter antenna device 9.
• VSWR voltage standing wave ratio
• Transmitter antenna device 9 comprises a switching device 11 connected to transmission line 5 and a transmitting antenna structure 12, preferably consisting of a plurality of transmitting antenna elements, connectable to transmission line 5 via switching device 11.
• transmitter antenna device 9 may, however, equally well be consisting of a single transmitting antenna that is permanently connected.
• Receiver section 3 includes a receiving antenna structure 13 for receiving RF waves and for generating an RF signal in dependence thereof.
• Receiving antenna structure 13 is switchable between a plurality of (at least two) antenna configuration states, each of which is distinguished by a set of radiation related parameters, such as resonance frequency, input impedance, bandwidth, radiation pattern, gain, polarization and near-field pattern.
• a switching device 14 is arranged in proximity thereof for selectively switching antenna structure 13 between the antenna configuration states.
• the receiving antenna structure 13 and switching device 14 may be arranged integrally in a receiver antenna device 15.
• Antenna structure 13 may comprise a plurality of elements connectable to a transmission line 16 or to RF ground (not shown) and/or comprise a plurality of spaced points of connection connectable to transmission line 16 or to RF ground, respectively, which will be described further below.
• Antenna structure 13 is further connected, via transmission line 16, to one or several low noise amplifiers (LNA's) 17 for amplifying the received signal.
• LNA's low noise amplifiers
• the RF feeding of antenna structure 13 can be achieved via switching device 14 as in the illustrated case, or can be achieved separately, outside of switching device 14.
• reception diversity the signal outputs from the low noise amplifiers 17 are combined in a combiner 18.
• the diversity combining can be of switching type, or be a weighted summation of the signals.
• Transmission line 16 is further connected to a downconverter or downmixer 19 for downconverting the frequency of the signal and to an analogue to digital (A/D) converter 20 for converting the received signal to a digital signal.
• A/D analogue to digital converter 20 for converting the received signal to a digital signal.
• the digital signal is output at 21 to digital processing circuitry of the radio communication device .
• a control device 22 for controlling switching device 14 in receiver section 3, and thus the selective connecting and disconnecting of parts of the receiving antenna structure 13, in dependence on a measure representing the reflection coefficient at transmitter section 2, where the measure may be a voltage standing wave ratio (VSWR) as measured by device 10.
• VSWR voltage standing wave ratio
• the reflected power can be measured.
• the description will refer to VSWR only, even though it shall be appreciated that other reflection measures may be employed.
• antenna structure 13 By means of switching device 14 the connection and disconnection of parts of antenna structure 13 is easily controllable.
• radiation related parameters such as resonance frequency, input impedance, bandwidth, radiation pattern, gain, polarization, and near-field pattern of receiver antenna device 15 can be altered.
• the VSWR is preferably measured repeatedly during use, by sampling at regular time intervals or continuously.
• Control device 22 may be arranged for controlling switching device 14 to switch state, in dependence on the repeatedly received measured VSWR during use of antenna module 1 in a radio communication device, so as to dynamically adapt antenna device 1 to objects, such as the user himself, in the close-by environment of the radio communication device. Hence, the performance of receiver section 3 of the antenna module may be continuously optimized during use.
• Control device 22 comprises preferably a central processing unit (CPU) 23 with a memory 24 connected to measuring device 10 via connections 25, 26 and to switching device 14 via line 27.
• CPU 23 is preferably provided with a suitable control algorithm and memory 24 is used for storing various antenna configuration data for the switching.
• Switching device 14 comprises preferably a microelectromechanical system (MEMS) switch device.
• MEMS microelectromechanical system
• CPU 23 thus receives measured VSWR values from VSWR measuring device 10 through lines 25, 26 and processes each received VSWR value. If it finds it suitable (according to any implemented control algorithm) it sends switching instruction signals to switching device 14 via line 27.
• antenna structure 12 of transmitter section 2 is switchable between a plurality of (at least two) antenna configuration states, each of which is distinguished by a set of radiation related parameters, such as resonance frequency, impedance, radiation pattern, polarization, and bandwidth and switching device 11 is arranged for selectively switching said antenna structure in dependence on control signals sent from control device 22 via a control line 28.
• radiation related parameters such as resonance frequency, impedance, radiation pattern, polarization, and bandwidth
• antenna module 1 comprises a control port 29 for signaling between CPU 23 and circuitry of the radio communication device via line 29a.
• power amplifier 8, low noise amplifiers 17, and combiner 18 may be controlled via lines 30, 31, and 32, respectively.
• reference numeral 33 indicates a parallel-serial converter arranged in transmitter section 2 for converting parallel signaling lines 25, 28, 30 to a serial line 26. This is for reducing the number of lines, and thus connections, between transmitter section 2 and receiver section 3.
• CPU 23, memory 24 and control port 29 may be located in the transmitter section 2 and hence parallel-serial converter
• the antenna module 1 as illustrated in Fig. 1 has only digital ports (input 4, output 21, and control port 29) and thus, it may be referred to as a digital controlled antenna (DCA).
• DCA digital controlled antenna
• an antenna module according to the present invention does not necessarily have to include A/D and D/A converters, frequency converters or amplifiers. In any of these cases the antenna module will obviously have analogue input and output ports .
• the antenna parameters such as resonance frequency, input impedance, bandwidth, radiation pattern, polarization, near-field pattern, of a small-sized wireless communication device are affected by objects in the proximity of the device.
• proximity is here meant the distance within which the effect on the antenna parameters is noticeable. This distance extends roughly about one wavelength from the device.
• a small-sized wireless communication device such as a mobile telephone
• the free space (FS) operation environment is obtained by locating the radio communication device in empty space, i.e. with no objects in the proximity of the device. Air surrounding the device is here considered free space.
• Many operation environments can be approximated by the free space environment. Generally, if the environment has little influence on the antenna parameters, it can be referred to as free space.
• the talk position (TP) operation environment is defined as the position, in which the radio communication device is held to the ear by a user.
• the influence on the antenna parameters varies depending on the person that is holding the device and on exactly how the device is positioned.
• the TP environment is considered as a general case, i.e. covering all individual variations mentioned above.
• antennas for wireless radio communication devices experience detuning due to the presence of the user.
• the resonance frequency may drop a few percent when the user is present, compared to when the device is positioned in free space.
• An adaptive tuning between free space and talk position can reduce this problem substantially.
• a straightforward way to tune an antenna is to alter its electrical length, and thereby altering the resonance frequency. The longer the electrical length is, the lower is the resonance frequency. This is also the most straightforward way to create band switching, if the change in electrical length is large enough .
• a meander-like antenna structure 35 arranged together with a switching device 36 comprising a plurality of switches 37-49.
• Antenna structure 35 may be seen as a plurality of aligned and individually connectable antenna elements 50-54, which in a connected state are connected to a feed point 55 through switching device 36.
• Feed point 55 is further connected to a low noise amplifier of a receiver circuitry (not shown) of a radio communication device, and hence antenna structure 35 operates as a receiving antenna.
• the low noise amplifier may alternatively be located in an antenna module together with the antenna structure 35 and the switching device 36.
• feed point 55 is connected to a power amplifier of a radio communication transmitter for receiving an RF signal, and hence antenna structure 35 operates as a transmitting antenna.
• a typical example of operation is as follows. Assume that switches 37 and 46-49 are closed and remaining switches are opened and that such an antenna configuration state is adapted for optimal performance when being arranged in a hand-portable telephone located in free space. When the telephone is moved to talk position, the influence of the user lowers the resonance frequency and thus, in order to compensate for the presence of the user, switch 49 is opened, whereby the electrical length of the connected antenna structure is reduced and accordingly the resonance frequency is increased. This increase shall with an appropriate design of antenna structure 35 and switching device 36 compensate for the reduction as introduced when the telephone is moved from free space to talk position.
• the same antenna structure 35 and switching device 36 may also be used for switching between two different frequency bands such as GSM900 and GSM1800.
• an antenna configuration state which includes antenna elements 50-53 connected to feed point 55 (switches 37 and 46-48 closed and remaining switches opened)
• switching to the GSM1800 frequency band may be effectuated by simply open switch 47, whereby the electrical length of the presently connected antenna structure (elements 50 and 51) is reduced to approximately half the previous length, implying that the resonance frequency is approximately doubled, which would be suitable for the GSM1800 frequency band.
• An antenna structure can have feed points at different locations.
• Each location has a different ratio between the E and H fields, resulting in different input impedances. This phenomenon can be exploited by switching the feed point, provided that the feed point switching has little influence on the rest of the antenna structure.
• the antenna can be matched to the feed line impedance by altering for example the feed point of the antenna structure.
• RF grounding points can be altered.
• FIG. 3 is schematically shown an example of such an implementation of an antenna structure 61 that can be selectively RF grounded at a number of different points spaced apart from each other.
• Antenna structure 61 is in the illustrated case a planar inverted F antenna (PIFA) mounted on a PCB 62 of a radio communication device.
• Antenna 61 has a feed line 63 and N different spaced RF ground connections 64. By switching from one RF ground connection to another, the impedance is slightly altered.
• PIFA planar inverted F antenna
• switching in/out parasitic antenna elements can produce an impedance matching, since the mutual coupling from the parasitic antenna element to the active antenna element produces a mutual impedance, which adds to the input impedance of the active antenna element.
• Typical usage positions than FS and TP can be defined, such as for instance waist position, pocket position, and on a steel table. Each case may have a typical tuning/matching, so that only a limited number of points need to be switched through. If outer limits for the detuning of the antenna elements can be found, the range of adaptive tuning/matching that needs to be covered by the antenna device can be estimated.
• One implementation is to define a number of antenna configuration states that cover the tuning/impedance matching range. There can be equal or unequal impedance difference between each different antenna configuration state.
• the radiation pattern of a wireless terminal is affected by the presence of a user or other object in its near-field area. Loss- introducing material will not only alter the radiation pattern, but also introduce loss in radiated power due to absorption.
• the radiation pattern of the terminal is adaptively controlled.
• the radiation pattern near- field
• the radiation pattern can be directed mainly away from the loss-introducing object, which will reduce the overall losses.
• a change in radiation pattern requires the currents producing the electromagnetic radiation to be altered.
• a small device e.g. a hand-portable telephone
• Another way may be to switch from an antenna structure that interacts heavily with the PCB of the radio communication device (e.g. whip or patch antenna) to another antenna not doing so (e.g. loop antenna). This will change the radiating currents dramatically since interaction with the PCB introduces large currents on the PCB (the PCB is used as main radiating structure) .
• an antenna structure that interacts heavily with the PCB of the radio communication device (e.g. whip or patch antenna) to another antenna not doing so (e.g. loop antenna).
• VSWR may be a good indicator of when there are small losses.
• Small changes in VSWR as compared to VSWR of free space implies small losses due to nearby objects.
• the discussion above concerns the antenna near-field and loss from objects in the near-field. However, in a general case, one could be able to direct a main beam in the far-field pattern in a favorable direction producing good signal conditions.
• the polarization can be altered in order to improve the signal conditions.
• the measured VSWR is processed in some kind of algorithm, which controls the state of the switches. All described algorithms will be of trial-and-error type, since there is no knowledge about the new state util it has been reached.
• the simplest algorithm is probably a switch-and-stay algorithm as shown in the flow diagram of Fig. 4.
• each state 1,... , N is used until the detected VSWR exceeds the predefined limit.
• the algorithm steps through the predefined states until a state is reached, which has a VSWR below threshold.
• Both the transmitter and receiver antenna structures can be switched at the same time.
• An arbitrary number of states may be defined, enabling switching to be performed between a manifold of states.
• a more advanced switch-and-stay algorithm as shown in the flow diagram of Fig. 5.
• Step 70 may look like:
• step 68 the algorithm is returned to step 68. Note that this algorithm may require quite fast switching and measuring of the VSWR, since all states have to be switched through in step 70.
• Fig. 6 is shown a flow diagram of such a further algorithm.
• VSWRi VSWR of state i
• a step 73 VSWRold a step 73 follows, wherein "change” is set to +change (this step i not really necessary) .
• Steps 74 and 75 follow, wherein VSWRold is set to present VSWR, i.e. VSWRi, and the antenna configuration state is changed to i + "change", i.e.
• step 76 follows, wherein variable "change” is set to -change.
• step 74 and 75 Note that in this case the algorithm changes "direction" .
• the algorithm assumes relatively small differences between two adjacent states, and that the antenna configuration states are arranged so that the rate of changes between each state is roughly equal. This means that between each state there is a similar quantity of change in, for example, resonance frequency. For example, small changes in the separation between feed and RF ground connections at a PIFA antenna structure would suit this algorithm perfectly, see Fig. 3. In all described algorithms it may be necessary to perform the switching only in specific time intervals adapted to the operation of the radio communication device.
• control device 22 of Fig. 1 may hold a look-up table with absolute or relative voltage standing wave ratio (VSWR) ranges, of which each is associated with a respective antenna configuration state.
• VSWR voltage standing wave ratio
• FIG. 7a shows an antenna structure pattern arranged around a switching device or unit 81.
• the antenna structure comprises receiving antenna elements, here in the form of four loop-shaped antenna elements 82. Within each of the loop- shaped antenna elements 82 a loop-shaped parasitic antenna element 83 is formed.
• Switching unit 81 comprises a matrix of electrically controllable switches (not shown) arranged for connecting and disconnecting antenna elements 82 and 83.
• the switches may be PIN diode switches, or GaAs field effect transistors, FET, but are preferably microelectromechanical system (MEMS) switches.
• MEMS microelectromechanical system
• the loop-shaped antenna elements can be connected in parallel or in series with each other, or some elements can be connected in series and some in parallel. Further, one or more elements can be completely disconnected or connected to RF ground (not shown) .
• Fig. 7b which shows an alternative antenna structure. It comprises all the antenna elements of Fig. 7a and further, between each pair of loop-shaped elements 82, 83, a meander-shaped antenna element 84.
• One or more of the meander- shaped antenna elements 84 can be used separately or in any combination with the loop antenna elements.
• Fig. 7c-e are shown antenna structures comprising two slot antenna elements 85, two meander-shaped antenna elements 87, and two patch antennas 89, repectively, connected to switching device 81.
• Each antenna element 85, 87, 89 may be fed at alternative spaced feed connections 86, 88, 90.
• Fig. 7f shows an antenna structure comprising a whip and/or helical antenna 91 and a meander-shaped antenna element 92 connected to switching device 81.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)
• Transceivers (AREA)
• Radio Relay Systems (AREA)
• Radio Transmission System (AREA)

Applications Claiming Priority (3)

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ID=20417563

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• 1999
  • 1999-10-29 SE SE9903943A patent/SE516531C2/sv not_active IP Right Cessation
• 2000
  • 2000-10-24 AU AU13188/01A patent/AU1318801A/en not_active Abandoned
  • 2000-10-24 CN CNB008152268A patent/CN1240191C/zh not_active Expired - Fee Related
  • 2000-10-24 EP EP00975088A patent/EP1234350A1/en not_active Ceased
  • 2000-10-24 KR KR1020027004960A patent/KR100669484B1/ko not_active IP Right Cessation
  • 2000-10-24 WO PCT/SE2000/002056 patent/WO2001031732A1/en active Application Filing

Non-Patent Citations (1)

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