A cellular range extender

Abstract

A cellular range extender has a primary antenna configured to communicate with a cellular network transmitter, a secondary antenna configured to repeat a signal received from the primary antenna, and control circuitry to interconnect the primary and secondary antennas. The primary antenna includes a circular reflector having a first diameter, a circular radiator having a second diameter smaller than the first diameter, and four circular directors, wherein a first director has a third diameter smaller than the second diameter and second to fourth directors have a fourth diameter smaller than the third diameter, the second to fourth directors being axially spaced apart. The reflector, radiator, and the directors are all coaxial. The reflector and the directors are electrically connected or connectable to each other and the radiator is electrically isolated from the reflector and the directors. The cellular range extender has a sensitivity of the primary antenna of as low as -155 dBm.

Description

[0001] A Cellular Range Extender

[0002] FIELD OF INVENTION

[0003] This invention relates to cellular network signal boosting and to a cellular range extender having a high sensitivity.

[0004] BACKGROUND OF INVENTION

[0005] The Inventor has noted frustration at poor cellular (or mobile) network coverage. A cellular telephone (cell phone) may operate at slow data speeds or disrupted voice channels if the signal is weak, or it may fail to operate at all. This problem is particularly acute in rural areas where mobile network towers are few and far between.

[0006] In broad terms, cellular (or mobile) repeaters, or “range extenders”, are well known. A generic cellular repeater may include two antennas, namely a primary or input antenna to receive a cellular signal (even a weak one), an amplifier and control circuitry to amplify the received signal, and a secondary or output antenna to rebroadcast the cellular signal. A user with a mobile phone may connect to the repeater, the phone communicating with the output antenna of the repeater. The user may even be oblivious to the existence of the repeater, merely experiencing stronger mobile network coverage.

[0007] Existing cellular repeaters of which the inventor is aware are inadequate in areas of very weak signal. The input antenna of the repeater needs at least some level of signal in order to operate effectively. For example, in rural areas in Africa, primary cellular towers may be so sparse with signal levels being so low, that many conventional cellular repeaters simply do not function adequately.

[0008] The Applicant accordingly desires a cellular repeaterwhich is sensitive enough to work in even very low signal conditions.

[0009] SUMMARY OF INVENTION

[0010] Accordingly, the invention provides a cellular range extender which includes a primary antenna configured to communicate with a cellular network transmitter, a secondary antenna configured to repeat a signal received from the primary antenna, and control circuitry to interconnect the primary and secondary antennas, wherein the primary antenna includes:

[0011] a circular reflector having a first diameter,

[0012] a circular radiator having a second diameter smaller than the first diameter, the radiator arranged coaxially on an antenna axis with, and axially outwardly of, the reflector;

[0013] four circular directors, wherein:

[0014] a first director has a third diameter smaller than the second diameter, the first director arranged coaxially on the antenna axis with, and axially outwardly of, the radiator; and

[0015] second to fourth directors have a fourth diameter smaller than the third diameter, the second to fourth directors being axially spaced apart, and arranged coaxially on the antenna axis with, and outwardly of, the first director;

[0016] wherein: the reflector and the directors are electrically connected or connectable to each other;

[0017] the radiator is electrically isolated from the reflector and the directors;

[0018] a first conductor is connected or connectable to the radiator;

[0019] a second conductor is connected or connectable to the reflector and the directors;

[0020] the input antenna is configured to have the following characteristics:

[0021] circular polarisation;

[0022] a gain of 120 ± 5 dBi; and

[0023] 45° aperture angle,

[0024] which, collectively, provide a sensitivity of the primary antenna of as low as -155 dBm.

[0025] The reflector, radiator, and directors may be referred to collectively as antenna elements, or merely elements.

[0026] The first conductor may be an inner conductor of the coaxial cable and the second conductor may be an outer conductor of the coaxial cable

[0027] The primary antenna may be configured for a specific cellular network frequency or frequency band (https: / / en.wikipedia.org / wiki / Cellular frequencies). Dimensions of the elements (e.g., spacing and diameter) may differ depending on the intended network frequency. Example frequencies include 850 MHz, 1,800 MHz, 2,100 MHz, or 2,600 MHz.

[0028] For the 850 MHz frequency, the primary antenna will have the following values:

[0029] Characteristic (850 MHz) Values

[0030] Diameter of reflector 223 mm ± 1%

[0031]

[0032] Diameter of radiator 166 mm ± 1% Characteristic (850 MHz) Values Diameter of first director 121 mm ± 1% Diameter of second-fourth directors, each 86 mm ± 1% Axial spacing between reflector and radiator 22 mm ± 1% Axial spacing between radiator and first director 19 mm ± 1% Axial spacing adjacent directors, each 73 mm ± 1%

[0033]

[0034] Spacing between antenna axis and cable axis 59 mm ± 1%

[0035] For the 1 ,800 MHz frequency, the primary antenna will have the following values:

[0036] Characteristic (1,800 MHz) Values Diameter of reflector 109 mm ± 1% Diameter of radiator 81 mm ± 1% Diameter of first director 59 mm ± 1% Diameter of second-fourth directors, each 42 mm ± 1% Axial spacing between reflector and radiator 11 mm ± 1% Axial spacing between radiator and first director 9 mm ± 1% Axial spacing adjacent directors, each 35 mm ± 1%

[0037]

[0038] Spacing between antenna axis and cable axis 28.5 mm ± 1%

[0039] For the 2,100 MHz frequency, the primary antenna will have the following values:

[0040] Characteristic (2,100 MHz) Values Diameter of reflector 100 mm ± 1% Diameter of radiator 74 mm ± 1% Diameter of first director 54 mm ± 1% Diameter of second-fourth directors, each 39 mm ± 1% Axial spacing between reflector and radiator 10 mm ± 1% Axial spacing between radiator and first director 9 mm ± 1% Axial spacing adjacent directors, each 33 mm ± 1%

[0041]

[0042] Spacing between antenna axis and cable axis 27 mm ± 1%

[0043] For the 2,600 MHz frequency, the primary antenna will have the following values:

[0044] Characteristic (2,600 MHz) Values Diameter of reflector 76 mm ± 1% Diameter of radiator 57 mm ± 1% Diameter of first director 41 mm ± 1% Diameter of second-fourth directors, each 30 mm ± 1% Axial spacing between reflector and radiator 7 mm ± 1% Axial spacing between radiator and first director 6 mm ± 1% Axial spacing adjacent directors, each 25 mm ± 1%

[0045]

[0046] Spacing between antenna axis and cable axis 20.5 mm ± 1% The cellular range extender may include plural primary antennas. The plural primary antennas may be configured to function at different bandwidths. For example, a dualband cellular range extender may include two primary antennas configured for separate frequencies (or a quad-band cellular range extender may include four primary antennas configured for separate frequencies).

[0047] The primary antenna may have a power supply of 45 ± 2 dBm.

[0048] The antenna may provide the gain of 120 ± 5 d Bi .

[0049] The control circuitry may include a signal filter. The filter may preserve or even improve signal quality.

[0050] The primary antenna may have a standing wave ratio of < 1.5. The primary antenna may have an impedance of 50 Q.

[0051] The cellular range extender may include a displaceable support to which the primary antenna is mounted or mountable. The displaceable support may permit the primary antenna to be displaced such that it can be orientated or pointed in a direction of effective or optimum signal reception. The displaceable support may include azimuth and elevation control mechanisms. The displaceable support one stepper motors to actuate the azimuth and elevation control mechanisms.

[0052] The cellular range extender may include one motor configured to displace the displaceable support. The motor may be controllable by the control circuitry to optimise the orientation of the primary antenna. The control circuitry may be configured to cycle through a plurality or antenna orientations and measure the received signal strength at each orientation. The control circuit is configured to set an operative orientation corresponding to the orientation at which the received signal was the strongest or was stronger than a minimum operation threshold.

[0053] BRIEF DESCRIPTION OF DRAWINGS

[0054] The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings.

[0055] In the drawings:

[0056] FIG. 1 shows a three-dimensional view of a primary antenna for use in a cellular range extender, in accordance with the invention;

[0057] FIG. 2 shows a schematic side view of the primary antenna of FIG. 1 ;

[0058] FIG. 3 shows a cellular range extender, in accordance with the invention, incorporatingthe primary antenna of FIG. 1 ;

[0059] FIG. 4 shows a horizontal radiation pattern of the primary antenna of FIG. 1 ; and FIG. 5 shows a three-dimensional radiation pattern of the primary antenna of FIG. 1.

[0060] DETAILED DESCRIPTION OF EMBODIMENT

[0061] The following description of an example embodiment of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that changes can be made to the example embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the example embodiment without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the example embodiment are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description of the example embodiment is provided as illustrative of the principles of the present invention and not a limitation thereof.

[0062] Basic Configuration

[0063] FIGS 1-2 illustrate a primary antenna 100 for use in a cellular range extender 200 (see FIG.

[0064] 5). The primary antenna 100 has a plurality of antenna elements 110, 112, 129, 122, 124, 126 arranged coaxially along a central support member 102. A set of orthogonal axes (x-axis, y-axis, z-axis) are defined, with the x-axis being coaxial with the support member 102.

[0065] The antenna elements 110, 112, 129, 122, 124, 126 are configured and arranged in in a specific way, in accordance with the invention. The antenna elements 110, 112, 129, 122, 124, 126 are all circular and are arranged coaxially with one another along the x-axis. They are physically mounted to the support member 102.

[0066] The first element 110 (moving outwardly along the x-axis) is a reflector 110 which has a first diameter di. The next element 112 is a radiator 112 which has a second diameter d2which is smaller than di. The reflector 110 and the radiator 112 are spaced a first distance Si apart.

[0067] There are four directors 120, 122, 124, 126 (also considered as “guiding” elements) provided along the support member 102. A first director 120 has a third diameter d3which is smaller than d2. The first director 120 and the radiator 112 are spaced a second distance s2apart. Second to fourth directors 122, 124, 126 have a fourth diameter d4which is smaller than d3. Adjacent directors 120, 122, 124, 126 (e.g., the first director 120 and the second director 122) are spaced a third distance s3apart. The coaxial cable has two conductors, namely an inner (or first) conductor and an outer (or second) conductor. Practically, the inner conductor is provided by a core and the outer conductor is provided by the braid or sheath. The radiator 112 only is connected to the inner conductor, while the reflector 110 and directors 120, 122, 124, 126 are connected to the outer conductor (and thus to each other). The primary antenna 100 itself does not interconnect the radiator 112 with the other elements 110, 120, 122, 124, 126.

[0068] The coaxial cable may define defines its own axis which is coaxial with, but radially offset by a determined or determinable distance Oi, from the x-axis.

[0069] This configuration provides the primary antenna 100 with the following characteristics:

[0070] Characteristic Value

[0071] Polarisation Circular

[0072] Gain 120 ± 5 dBi

[0073] Aperture angle 45°

[0074]

[0075] Sensitivity -155 dBm

[0076] The dimensions (di...d4, S1...S3) of the primary antenna 100 may be determined based on a cellular band in which the primary antenna 100 is to operate. Four frequency bands (or bandwidths) have been determined:

[0077] Band 850 MHz 1,800 MHz 2,100 MHz 2,600 MHz

[0078] di 223 mm 109 mm 100 mm 76 mm

[0079] d2166 mm 81 mm 74 mm 57 mm

[0080] d3121 mm 59 mm 54 mm 41 mm

[0081] d486 mm 42 mm 39 mm 30 mm

[0082] Si 22 mm 11 mm 10 mm 7 mm

[0083] S2 19 mm 9 mm 9 mm 6 mm

[0084] S3 73 mm 35 mm 33 mm 25 mm

[0085]

[0086] 01 59 mm 28.5 mm 27 mm 20.5 mm Allowing for tolerances, the Applicant believes some or more of these values may be varied by up to 1 % and still achieve most of the desired result. FIG. 3 illustrates a cellular range extender 200 in accordance with the invention. The cellular range extender 200 includes two primary antennas 100 which may be configured to operate at different bands, thus making the cellular range extender 200 a dual band apparatus. The cellular range extender 200 may include more or fewer antennas 100.

[0087] The cellular range extender 200 has a support member 12 to mount the antennas 100 to an articulated arm 14 configured to support the antennas 100 at an extended or elevated position. A pin 16 attaches the articulated arm 14 to a rotational guide ring 18, configured to permit guided rotation of the articulated arm 14.

[0088] An elevation guide screw 20 supports the guide ring 18 and is configured to be controlled to raise or lower the guide ring 18, thereby to permit a change in elevation or inclination of the antennas 100. An antenna azimuth guide system 22 is attached to a rear end of the articulated arm 14. The cellular range extender 200 further includes a motor housing 24 which houses a motor (not illustrated) and an azimuth guidance system translation locking screw 26.

[0089] Various hardware or support components, like machine frames 28, assembly bolts (M6) 30, 36, and studs (M10) 40 are also provided. The cellular range extender200 has a brush mechanism protection system 32, a spring housing part 34, and a rotational guide collar 38 of the antenna azimuth guidance system.

[0090] Beneath these, there is an on-board antenna component package 42 supported on an upright stand 44. The cellular range extender 200 is anchored via fasteners like M16 anchor bolts 46 to a base structure 48 (e.g., a wall or other concrete structure).

[0091] The Applicant notes that the cellular range extender 200 with the primary antenna 100 performs betterthan the most powerful / sensitive comparable PRIOR ART range extender which the Applicant could procure: Characteristic PRIOR ART Extender Cellular range extender 200 Gain 95 ± 5 dBi 120 ± 5 dBi

[0092] Power supply 43 ± 2 dBm 45 ± 2 dBm

[0093] Aperture angle 60° 45°

[0094] Frequency band 850, 1,800, 2,100, 2,600 MHz 850, 1,800, 2,100, 2,600 MHz Standing wave ratio < 1.5 < 1.5

[0095] Impedance 50 Q 50 Q

[0096]

[0097] Sensitivity -128 dBm -155 dBm

[0098] The Applicant emphasises the improvement in sensitivity of the present cellular range extender 200.

[0099] Simulated Antenna Output

[0100] FIGS 4-5 illustrate a horizontal radiation pattern 300 and a three-dimensional radiation pattern 400 of the primary antenna 100 of the cellular range extender 200.

[0101] Measured Results

[0102] The Applicant further conducted field tests of the cellular range extender 200. The Applicant ran several tests comparing received signal strength between a generic but capable cellular telephone handset and the cellular range extender 200 using different cellular network providers and towers.

[0103] Distance from tower Network Operator Antenna

[0104] 7.10 km 9.01 km 12.60 km 14.04 km Range extender 200 -55 dBm -68 dBm -68 dBm -76 dBm Airtel

[0105] Cellular phone only -107 bDm n / s n / s n / s Range extender 200 -53 dBm -55 dBm -64 dBm -72 dBm Orange

[0106] Cellular phone only -102 bDm -105 dBm n / s n / s Range extender 200 -68 dBm -75 dBm -83 dBm -93 dBm Africell

[0107] Cellular phone only n / s n / s n / s n / s Range extender 200 -51 dBm -59 dBm -65 dBm -70 dBm Vodacom

[0108]

[0109] Cellular phone only -99 dBm -101 dBm n / s n / s (Where n / s = no signal or 0 dBm.)

[0110] io These results are not intended to compare cellular providers to each other, because the respective cellular towers would have had different locations, different intervening geography, different radiation patterns, etc. However, the results for the cellular range extender 200 of the present invention compared to a conventional cellular telephone are demonstrative.

[0111] The Applicant believes that the invention as exemplified provides a cellular range extender 200 with a primary antenna 100 that is more sensitive the conventional outdoor antennas. This means that the cellular range extender 200 may perform better, particularly in rural or isolated areas where it is not cost efficient to erectan entire cellular tower.

[0112] The Outdoor cellular range extender 200 is a network station which helps to increase coverage areas that were not getting cellular mobile signal; it has a directional antenna whereby the configuration of the direction of the best signal is not manual, that direction is found through a mechanical system driven by a stepper motor to control the antenna 100 in elevation and azimuth via an algorithm in the controller.

[0113] With improved radiative, geometric and electrical properties, the cellular range extender 200 allow pick up of a signal in poor radio conditions. Given its low price it is suitable for environments less profitable for mobile operators.

[0114] The experience during the different runs (shown in the table in the Measured Results above) shows that places where the mobile phone did not pick up the network signal before, after initialising the cellular range extender 200, the mobile phone did pick up the network signal.

[0115] The cellular range extender 200 is configured to detect a weak signal from different mobile network operators in areas far from the mobile base station, amplify it, then transmit it via a transceiver module. The smart embedded part of the cellular range extender 200 determines the optimal direction at which the maximum signal power from the operator base station could be collected. The cellular range extender 200 was characterised in terms of signal sensitivity, distance span and gain after field testing, -55 dBm, 14.04 km and 120±5 dBi were successfully demonstrated for the antenna 100, respectively: sensitivity, distance between the cellular range extender 200 and the operator base station and antenna gain.

Claims

CLAIMS1. A cellular range extender which includes a primary antenna configured to communicate with a cellular network transmitter, a secondary antenna configured to repeat a signal received from the primary antenna, and control circuitry to interconnect the primary and secondary antennas, wherein the primary antenna includes:a circular reflector having a first diameter,a circular radiator having a second diameter smaller than the first diameter, the radiator arranged coaxially on an antenna axis with, and axially outwardly of, the reflector;four circular directors, wherein:a first director has a third diameter smaller than the second diameter, the first director arranged coaxially on the antenna axis with, and axially outwardly of, the radiator; andsecond to fourth directors have a fourth diameter smaller than the third diameter, the second to fourth directors being axially spaced apart, and arranged coaxially on the antenna axis with, and outwardly of, the first director;wherein:the radiator is electrically isolated from the reflector and the directors; a first conductor is connected or connectable to the radiator;a second conductor is connected to the reflector and the directors; and the input antenna is configured to have the following characteristics: circular polarisation;a gain of 120 ± 5 d Bi; and45° aperture angle,which, collectively, provide a sensitivity of the primary antenna of as low as -155 dBm.

2. The cellular range extender as claimed in claim 1 , in which:the first and second conductors are provided by a coaxial cable; the first conductor is an inner conductor of the coaxial cable and the second conductor is an outer conductor of the coaxial cable.

3. The cellular range extender as claimed in claim 1, which has a frequency band of 850 MHz and has some or all of the following characteristics:Characteristic (850 MHz) ValuesDiameter of reflector 223 mm ± 1% Diameter of radiator 166 mm ± 1% Diameter of first director 121 mm ± 1% Diameter of second-fourth directors, each 86 mm ± 1%Axial spacing between reflector and radiator 22 mm ± 1%Axial spacing between radiator and first director 19 mm ± 1%Axial spacing adjacent directors, each 73 mm ± 1%Spacing between antenna axis and cable axis 59 mm ± 1%4. The cellular range extender as claimed in claim 1, which has a frequency band of 1 ,800 MHz and has some or all of the following characteristics:Characteristic (1,800 MHz) ValuesDiameter of reflector 109 mm ± 1% Diameter of radiator 81 mm ± 1% Diameter of first director 59 mm ± 1% Diameter of second-fourth directors, each 42 mm ± 1%Axial spacing between reflector and radiator 11 mm ± 1%Axial spacing between radiator and first director 9 mm ± 1%Axial spacing adjacent directors, each 35 mm ± 1%Spacing between antenna axis and cable axis 28.5 mm ± 1%5. The cellular range extender as claimed in claim 1, which has a frequency band of 2,100 MHz and has some or all of the following characteristics:Characteristic (2,100 MHz) ValuesDiameter of reflector 100 mm ± 1% Diameter of radiator 74 mm ± 1% Diameter of first director 54 mm ± 1% Diameter of second-fourth directors, each 39 mm ± 1%Axial spacing between reflector and radiator 10 mm ± 1%Axial spacing between radiator and first director 9 mm ± 1%Axial spacing adjacent directors, each 33 mm ± 1%Spacing between antenna axis and cable axis 27 mm ± 16. The cellular range extender as claimed in claim 1, which has a frequency band of 2,600 MHz and has some or all of the following characteristics:Characteristic (2,600 MHz) ValuesDiameter of reflector 76 mm ± 1% Diameter of radiator 57 mm ± 1% Diameter of first director 41 mm ± 1% Diameter of second-fourth directors, each 30 mm ± 1%Axial spacing between reflector and radiator 7 mm ± 1%Axial spacing between radiator and first director 6 mm ± 1%Axial spacing adjacent directors, each 25 mm ± 1%Spacing between antenna axis and cable axis 20.5 mm ± 1%7. The cellular range extender as claimed in claim 1, which includes plural primary antennas.

8. The cellular range extender as claimed in claim 7, in which the plural primary antennas are configured to function at different bandwidths.

9. The cellular range extender as claimed in claim 1 , in which the primary antenna has a power supply of 45 ± 2 dBm.

10. The cellular range extender as claimed in claim 1, in which the primary antenna provides the gain of 120 ± 5 d Bi .

11. The cellular range extender as claimed in claim 1, in which the control circuitry includes a signal filter.

12. The cellular range extender as claimed in claim 1, in which the primary antenna has a standing wave ratio of < 1.5 and an impedance of 50 Q.

13. The cellular range extender as claimed in claim 1, which includes a displaceable support to which the primary antenna is mounted or mountable.

14. The cellular range extender as claimed in claim 13, in which the displaceable support includes azimuth and elevation control mechanisms and at least one motor to actuate the azimuth and elevation control mechanisms.

15. The cellular range extender as claimed in claim 14, in which the control circuitry is configured to control the motor to displace the displaceable support to optimise the orientation of the primary antenna.

16. The cellular range extender as claimed in claim 15, in which the control circuitry is configured to cycle through a plurality or antenna orientations and measure the received signal strength at each orientation, and then to set an operative orientation corresponding to the orientation at which the received signal was the strongest or was stronger than a minimum operation threshold.

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