Cellular telephone antenna array

Abstract: An antenna assembly which is safer for a user of an electronic communications device, such as a cellular telephone, is disclosed. The electronic communications device includes a housing and a communications port. The antenna assembly includes a stationary active member (e.g., an antenna) that is connected to the communications port. The stationary active member may be an existing antenna on the electronic communications device. The antenna assembly also includes a field diverter which is connected to the stationary active member and reduces radiation adjacent to the electronic communications device. The field diverter is made up of a non-stationary active member and a connecting arm which connects the non-stationary active-member to the stationary active member. Power is divided between the stationary active member and the non-stationary active member in order to decrease radiation in an area where a user's head is located by creating a notch in the azimuth pattern near the area where the user's head is located. The notch forms a sector where the radiation is decreased or diverted to an area away from the sector (i.e., away from the user's head).

Description: The present invention relates generally to an antenna assembly, and more particularly to a design for an antenna assembly for a cellular telephone that is safe for the user. Recent newspaper, radio and television stories are publicising the possibility of dangers from the current cellular telephone antenna designs. The current antenna designs are variations of a half-wavelength dipole or a quarter-wavelength monopole on a ground plane with the use of inductive coils and/or capacitive top loading to reduce the length of the antenna and to achieve a satisfactory impedance match. These designs all radiate omni-directional in the azimuth plane, which means that the user's head, and hence brain, is irradiated with an amount of electromagnetic (EM) radiation equal to that in any other direction in azimuth, which may be unsafe, particularly with repeated exposure. Published studies have shown that the curvature of the skull bones and brain matter focuses to some extent on impinging EM radiation creating "hot spots" within the brain. Recently, the media has been focusing on the possible increased risk to the user of developing a brain tumour. However, other medical problems are also possible, including increased risk of stroke, Parkinson's disease and Alzheimer's Syndrome. Thus, a need exists for a cellular telephone antenna design which decreases the radiation near a user's head and is therefore safer for the user. US-A-5539419, WO99/56342A and WO 94/14208 disclose antenna arrangements as defined in the preamble of Claim 1, to reduce radiation to the user. In accordance with aspects of the invention, an antenna assembly which is still safer for a user of an electronic communications device, such as a cellular telephone, is disclosed and is claimed in Claim 1. In preferred forms of the invention, the field diverter is made up of a second active member opposite (e.g. substantially parallel to) the first active member. Preferably, the pair of active members (i.e. the first active member and the second active member) are substantially identical to each other, for example, both are monopole antennas or both are dipole antennas. In various embodiments, the pair of active members are extendible. In other embodiments, the pair of active members are extracted from the housing. There is about a 90-degree phase differential between the two active members. Conveniently the pair of active members are connected by an active connecting member (e.g. an arm). Preferably, the active connecting member is rotatable such that the second active member rotates about the first active member. In various embodiments, the active connecting member is extendible. The active connecting member includes a power divider which splits power from the communications port substantially equally between the pair of active members such that the pair of active members have input voltages equal in amplitude. There may also be an inactive connecting member opposite (e.g. substantially parallel to) the active connecting member. Preferably, the inactive connecting member is made of non-metallic and/or dielectric materials. There may also be a transmit enable switch that is only operable when the second active member is in a transmit detented position. There may also be a transmit disable switch that disables transmissions from the electronic communications device when the pair of active members are not properly spaced from each other. The functionality of the transmit enable switch and transmit disable switch can be combined into a single switch. Preferably, the electronic communications device is always capable of receiving an incoming signal (e.g. an incoming call). The preferred antenna assembly transmits in an azimuth pattern which includes a notch near the area where the user's head is located, this defining the field isolation zone. The notch forms a sector of about 55 degrees in which the radiation is decreased (e.g. the radiation in the sector is decreased by at least 20 dB). The radiation is increased (by about 3dB) in an area away from the user's head. These, as well as other features of the preferred embodiments of the present invention, will become more apparent upon reference to the drawings wherein: Figure 1 is a top view of a prior art cellular telephone; Figure 2 is a front view of the cellular telephone of Figure 1; Figure 3 is a top view of a cellular telephone with an antenna formed in accordance with a preferred embodiment; Figure 4 is a front view of the cellular telephone of Figure 3; and Figure 5 is an illustration showing the azimuth patterns for a single dipole and for the antenna system of the preferred embodiment with a pictorial of the head and telephone positions. The present invention is directed to an antenna system (e.g. for a cellular telephone) that reduces EM radiation directed towards the head and brain of a user by 20 dB or more. In exemplary embodiments, the antenna of the present invention is compatible with each cellular telephone manufacturer's currently designed telephones, for example, a cellular telephone with a dipole antenna. Figures 1 and 2 illustrate exemplary front and side views, respectively, of a typical (prior art) cellular telephone 10. Telephone 10 includes circuitry (not shown) contained in a housing 12. Exemplary (prior art) telephone 10 includes a stationary active member (e.g. an antenna) 14 which is proximate the housing 12, for example, proximate the top of the housing in the illustrated example. It will be appreciated that in various embodiments the stationary active member 14 may be a telescoping structure wherein the antenna may be located within the housing 12 when the user is not transmitting, but can be placed in the extended position when the user wishes to transmit. In the example shown in Figure 2, stationary active member 14 includes a fixed portion 16 and an extendible portion 18. The stationary active member 14 is stationary (not necessarily static) in that its position relative to the telephone 10 (e.g., connected to a communications port 20) is constant even though the stationary active member itself may be not be static (e.g., may be telescoping or may pivot). For example, the stationary antenna 14 of Figure 1 is located on the right-hand side of the top of the telephone 10 and is connected to communications port 20. Communications port 20 forwards input signals received by the stationary active member 14 to the circuitry. Similarly, output (or transmit) signals are sent from the circuitry to the stationary active member 14 via the communications port 20. The exemplary embodiment illustrated and described herein is described with respect to the details and dimensions for a telephone with a half-wavelength dipole antenna 14. As discussed above, it will be appreciated that embodiments exist for virtually every cellular telephone model manufactured by any manufacturer. For example, the antenna could be a quarter wavelength monopole antenna with a ground plane within the case, a quarter wavelength monopole with a ground plane within the case and the length of the monopole shortened by using an inductive coil at the feed point at the base of the monopole and/or a captive load at the tip of the monopole. In accordance with the present invention, a safer cellular telephone 30 (shown in Figures 3 and 4) includes a field diverter 34 in addition to the elements of prior art telephone 10. The field diverter 34 diverts radiation away from the user's head as shown in Figure 5 and described later. The field diverter 34 includes, a non-stationary active member 36 which is preferably identical to the stationary active member 14. For example, the non-stationary active member 36, like the stationary active member 14, is a telescoping antenna which includes a fixed member 38 and an extendible member 40. The non-stationary active member 36 is connected to the stationary active member 14 by a connecting arm 42 which is capable of rotating, e.g., 90 degrees, to a detented position, as shown in Figure 3. In addition, a 90-degree power divider is used to split the incoming power from the telephone's transmitter circuitry substantially evenly (from 1:1 to 0.95:1.05) between the two active members 14 and 36, but with a 90-degree phase differential ( +/- 10 degrees) between the signal communicated between the two active members. To ensure proper antenna deployment before the transmitter power is delivered to the active members 14 and 36, the connecting arm 42 activates a transmit enable switch (not shown) which enables the transmit circuitry only when the non-stationary active member 36 is in the transmit detented position. The receiver circuitry is always operational to receive the "ring" of an incoming call. Preferably, the input voltages of the active members 14 and 36 are equal in amplitude and 90 degrees apart in phase. As described above, a power divider divides the voltage evenly between the antennas 14 and 36. The transmit power enters the input port of the power divider and is split evenly within he device such that one-half of the power exits the device via each of the two exit ports. Various implementations can be used to divide the power, for example, a discrete 90 degree hybrid (for example, Model 4356A Quadrature Hybrid or Broadband 90° Hybrid, both manufactured by Narda, a subsidiary of Loral) may be used, a micro-strip etched power divider with an additional quarter-wavelength at the transmit frequency, e.g., 90 degrees, in line length leading to the detented antenna (for example, a Multi-Octave Type SMA 2-Way Power Divider, manufactured by Narda, a subsidiary of Loral) may be used, or another variation may be used. It may be useful in some cases to modify elements (e.g., the inductance coil at the base) of the currently used impedance matching network as well, in order to better match the input impedance of the antenna pair to the feed network. Ideally, the pair of active members 14 and 36 are one quarter wavelength apart at the transmit frequency to a tolerance of +/- 5% (i.e., 20 to 30% of the transmit frequency wavelength. For some cellular telephone designs, this phase differential may be more than the width of the telephone body, in which case, the connecting "arm" 42 may be telescoping, such as the connecting arm shown in Figure 4 which includes a fixed member 44 and an extendible member 46. Various embodiments also include an inactive structure 48 (preferably made of non-metallic and/or dielectric materials) that allows the two active members 14 and 36 to be pushed side-by-side when in the stored condition and pulled out to the appropriate spacing when being readied for use. As with connecting arm 42, the inactive structure may be telescoping, and include a fixed member 50 and an extendible member 52. Exemplary embodiments may also include a transmit disable switch (not shown) to disable the transmitter function when the active members 14 and 36 are not at the appropriate spacing. Preferably, this switch is combined with the transmit enable switch to disable the transmitter function when the non-stationary active member 36 is not in its detented position. If the switches are combined, a single switch activates the transmitter function only when the two antennas are in their proper positions and spacing. In this case, two motions (performed in either order) are required by the user: (1) the antennas are pulled apart to the appropriate spacing; and (2) the pivoting antenna is rotated to the detented position. Figure 5 shows the azimuth patterns for a single dipole 60 and for the antenna system of the present invention with a pictorial of the user's head 62 and telephone 30 positions. Each of the rings 64 represents 10dB. It will be appreciated that while the following comparisons are directed to a dipole, they hold true for any variation of dipole or monopole formed in accordance with the present invention. The invention has approximately 3dB more gain 66 in the direction away from the head than the single dipole 60 has, as shown in Figure 5. As is shown, for the 180 degrees starting from facing forward through the side directly away from the head and ending directly behind, the present invention has gain equal to or greater than a single dipole. The additional gain over this region is due to the "notch" in the pattern 68 in the area where the head 40 (and, therefore, the brain) is located. There is an approximately 55-degree sector 70 created by notch 68 where the radiation is 20 dB or more below that of the single dipole in which the head 62 and brain are located. In the elevation plan of Figure 5 (which is 0 degrees), the present invention has the same pattern 66 as the single dipole 60. In each case, there is a null in the pattern where the head 62 is located. Hence, the elevation pattern radiation does not create a hazard to the head 62 and brain, rather the azimuth pattern creates the hazard. Azimuth vs. relative gain for an exemplary embodiment of the invention (as shown in Figure 5) is shown in Table I. The configuration used for the example shown in Table I is as follows: frequency is .9 GHz; antenna spacing is 8.328 cm; amplitude distribution is uniform; phase shift is 90 degrees; the antenna is a dipole antenna with a length of 16.655 cm; there is no ground plane; the polarization is substantially parallel to the length of the antenna; the absolute maximum gain is 5.16 dBi; and the absolute maximum gain repeated for one antenna is 2.15 dBi; hence a 3dB difference. Relative gain subtracts the 5.16 dBi from all of the values, thereby normalizing the peak gain to 0 dB. Azimuth (in degrees) Relative Gain (in dB) 0 0 + /- 1 -5.17726E-07 +/- 2 -3.106357E-06 +/- 3 -9.836804E-06 +/- 4 -2.407432E-05 + /- 5 -5.151404E-05 +/- 6 -9.888678E-05 +/- 7 -1.742183E-04 +/- 8 -2.865708E-04 +/- 9 -4.47856E-04 +/- 10 -6.69989E-04 +/- 11 -9.661841E-04 +/- 12 -1.35277E-03 +/- 13 -1.845826E-03 +/- 14 -2.462744E-03 +/- 15 -3.223781E-03 + /- 16 -4.148189E-03 +/- 17 -5.259137E-03 +/- 18 -6.578546E-03 +/- 19 -8.130985E-03 +/- 20 -9.941095E-03 +/- 21 -1.203671E-02 +/- 22 -1.444395E-02 + /- 23 -1.719194E-02 +/- 24 -2.031017E-02 +/- 25 -2.382991E-02 +/- 26 -2.778157E-02 + /- 27 -3.219762E-02 +/- 28 -3.711262E-02 +/- 29 -4.255965E-02 +/- 30 -4.857394E-02 + /- 31 -5.519114E-02 +/- 32 -6.244735E-02 +/- 33 -7.038022E-02 +/- 34 -7.902692E-02 +/- 35 -8.842605E-02 +/- 36 -9.861715E-02 +/- 37 -.1096379 +/- 38 -.1215302 +/- 39 -.1343332 + /- 40 -.1480884 +/- 41 -.1628372 + /- 42 -.1786201 + /- 43 -.1954798 +/- 44 -.2134588 + /- 45 -.2325992 +/- 46 -.252944 +/- 47 -.2745358 +/- 48 -.2974186 +/- 49 -.3216347 +/- 50 -.3472292 +/- 51 -.374245 +/- 52 -.4027253 +/- 53 -.4327153 +/- 54 -.4642577 +/- 55 -.4973982 +/- 56 -.53218 +/- 57 -.5686468 +/- 58 -.6068445 +/- 59 -.6468159 +/- 60 -.6886062 +/- 61 -.7322592 +/- 62 -.7778198 + /- 63 -.8253322 + /- 64 -.8748406 +/- 65 -.9263904 +/- 66 -.9800246 +/- 67 -1.035789 +/- 68 -1.093728 +/- 69 -1.153885 +/- 70 -1.216307 +/- 71 -1.281036 +/- 72 -1.348119 +/- 73 -1.4176 + /- 74 -1.489524 +/- 75 -1.563937 +/- 76 -1.640885 +/- 77 -1.720412 +/- 78 -1.802564 +/- 79 -1.887387 + /- 80 -1.974929 +/- 81 -2.065236 +/- 82 -2.158354 +/- 83 -2.254333 +/- 84 -2.353218 +/- 85 -2.455059 +/- 86 -2.559905 +/- 87 -2.667805 +/- 88 -2.778811 +/- 89 -2.892971 +/- 90 -3.01034 +/- 91 -3.130969 +/- 92 -3.254911 +/- 93 -3.382222 +/- 94 -3.512957 +/- 95 -3.647171 +/- 96 -3.784926 +/- 97 -3.926277 +/- 98 -4.071289 +/- 99 -4.22002 +/- 100 -4.37254 +/- 101 -4.52891 +/- 102 -4.689198 +/- 103 -4.853477 +/- 104 -5.021817 + /- 105 -5.194294 +/- 106 -5.370983 +/- 107 -5.551965 +/- 108 -5.737323 +/- 109 -5.927143 +/- 110 -6.121512 +/- 111 -6.320527 +/- 112 -6.524281 + /- 113 -6.732876 +/- 114 -6.946416 + /- 115 -7.165015 +/- 116 -7.388783 +/- 117 -7.61784 +/- 118 -7.852318 +/- 119 -8.09234 +/- 120 -8.338052 +/- 121 -8.589599 +/- 122 -8.847129 + /- 123 -9.11081 +/- 124 -9.380809 +/- 125 -9.657308 +/- 126 -9.940493 +/- 127 -10.23057 +/- 128 -10.52775 +/- 129 -10.83226 +/- 130 -11.14434 +/- 131 -11.46424 +/- 132 -11.79223 +/- 133 -12.12861 +/- 134 -12.47368 +/- 135 -12.82776 +/- 136 -13.19122 +/- 137 -13.56442 +/- 138 -13.94778 +/- 139 -14.34171 +/- 140 -14.7467 +/- 141 -15.16324 +/- 142 -15.59186 +/- 143 -16.03317 +/- 144 -16.4878 +/- 145 -16.95642 +/- 146 -17.4398 +/- 147 -17.93874 +/- 148 -18.45415 +/- 149 -18.98699 +/- 150 -19.53835 +/- 151 -20.10938 +/- 152 -20.70142 +/- 153 -21.3159 +/- 154 -21.95442 +/- 155 -22.6188 +/- 156 -23.31101 +/- 157 -24.03335 +/- 158 -24.78834 +/- 159 -25.5789 +/- 160 -26.40833 +/- 161 -27.28043 + /- 162 -28.19957 + /- 163 -29.17092 +/- 164 -30.2004 +/- 165 -31.29513 +/- 166 -32.46349 +/- 167 -33.71564 +/- 168 -35.06391 +/- 169 -36.52363 +/- 170 -38.1136 +/- 171 -39.85785 +/- 172 -41.7872 +/- 173 -43.94123 +/- 174 -46.37207 +/- 175 -52.34441 +/- 176 -56.03831 +/- 178 -60 +/- 179 -60 +/- 180 -∞ Additional modifications and improvements of the present invention may also be apparent to those of ordinary skill in the art. Thus, the particular parts described and illustrated herein is intended to represent only one embodiment of the present invention, and is not intended to serve as limitations of alternative devices within the spirit and scope of the invention.

Claims: An antenna assembly for an electronic communications device (30), the electronic communications device having a housing (12) with a communications port (20), the antenna assembly (32) comprising: a) a stationary active member (14) that is in communication with the communications port (20); and characterised by : a) a non-stationary active member (36) opposing the stationary active member (14), wherein the stationary active member and the non-stationary active member form a pair of active members; and b) an active connecting member (42) that connects the non-stationary active member to the stationary active member, whereby the stationary active member (14) and the non-stationary active member (36) are a) one quarter wavelength a part at a transmit frequency; and b) have input voltages substantially equal in amplitude and comprising about a 90-degree phase differential. The antenna assembly of Claim 1, further comprising an inactive connecting member (48) opposing the active connecting member (42). The antenna assembly of Claim 2, wherein the inactive connecting member comprises non-metallic materials. The antenna assembly of Claim 2, wherein the inactive connecting member comprises dielectric materials. The antenna assembly of Claim 1, wherein the active connecting member is rotatable such that the non-stationary active member (36) rotates about the stationary active member (14). The antenna assembly of Claim 1, wherein the pair of active members are substantially identical to each other. The antenna assembly of Claim 6, wherein the pair of active members are monopole antennas. The antenna assembly of Claim 6, wherein the pair of active members are dipole antennas. The antenna assembly of Claim 1, wherein the pair of active members are extendible. The antenna assembly of Claim 1, wherein the pair of active members are extracted from the housing. The antenna assembly of Claim 1, wherein the active connecting member is extendible. The antenna assembly of Claim 1, wherein the antenna assembly pivots. The antenna assembly of Claim 1, further comprising a transmit enable switch. 13 The antenna assembly of Claim 13, wherein the transmit enable switch is only operable when the non-stationary active member is in a transmit detented position. The antenna assembly of Claim 1, further comprising a transmit disable switch that disables transmissions from the electronic communications device when the pair of active members are not properly spaced from each other. The antenna assembly of any preceding claim, wherein the electronic communications device (30) is a cellular telephone. The antenna assembly of any preceding claim, wherein the electronic communications device is always capable of receiving an incoming signal. The antenna assembly of any preceding claim, wherein an azimuth pattern for the antenna assembly transmission comprises a notch (68) in the azimuth pattern near the area where the user's head (62) is located, the notch defining a boundary of the field isolation zone (68). The antenna assembly of Claim 18, wherein the notch forms a sector of about 55 degrees where the radiation in the sector is decreased. The antenna of Claim 19, wherein the radiation in the sector is decreased by at least 20 dB. The antenna assembly of Claim 19, wherein the radiation is increased in an area not hear the user's head. The antenna assembly of Claim 21, wherein the radiation is increased by about 3dB in the area not near the user's head.

Inventors: VAN HOOZEN ALLEN L, VAN HOOZEN, ALLEN L.
Applicants: NORTHROP GRUMMAN CORP, NORTHROP GRUMMAN CORPORATION
Application year: 2001
Main classification: H01Q1
IPC codes: H01Q1