TRANSMITTER, RECEIVER AND TRANSCEIVER APPARATUS

Abstract: In transceiver apparatus (1), there is a plurality of sets (A-H) of substantially unidirectional antennae (2). Each set of antennae (2) has a single radio subsystem (3) for providing a radio output signal for transmission by one of the antennae (2) in the set and for receiving a signal received by one of the antennae (2) to provide an output signal from the radio subsystem (3). Each of the plurality of radio subsystems has a switch (11). The switch (11) is operated to switch the output of the radio subsystem (3) to a selected one of the antennae (2) in the set for transmission of a radio signal by said selected antenna (2) and to switch an input of the radio subsystem (3) to a selected one of the antennae (2) in the set such that a signal received by said selected antenna (2) is passed as an input to the radio subsystem (3).

Description: TRANSMITTER, RECEIVER AND TRANSCEIVER APPARATUS The present invention relates to transmitter, receiver and transceiver apparatus . In our International patent application no. PCT/GB97/03472 and our British patent application no. 9726873.4, the entire disclosures of which are incorporated herein by reference, there is disclosed a communications apparatus comprising a mesh of interconnected nodes. Each node can communicate with plural other nodes via point-to- point radio links between nodes by means of substantially unidirectional radio transmissions along the links, i.e. signals are not broadcast but are instead directed to a particular node with signals being capable of being passed in both directions along the link. Each node has plural links to other nodes, for example eight links, providing a connection from each node to eight other nodes. In an example, time division duplex (TDD) is used to alternate transmission and reception modes along a link. In a preferred embodiment, time division multiplexing (TDM) is used to control the timing of transmission and reception between the links. For example, a node is able to transmit along a first link in a first time slot of a transmission portion of a time frame, along a second link during the second time slot of the transmission portion of the time frame, etc., for eight transmission time slots for the eight links. The node then is able to receive along the first link during a first time slot of the reception portion of the time frame, along the second link during the second time slot of the reception portion of the time frame, etc., for eight reception time slots for the eight links. As an alternative to TDD, frequency division duplex (FDD) or other techniques may be used. Because the radio components of a transceiver are relatively expensive, it was proposed in PCT/GB97/03472 and British patent application no. 9726873.4 to provide a single radio subsystem at each node with a M-way switch to switch the radio subsystem between the M links of that node . Because the links between nodes m the communications apparatus disclosed in PCT/GB97/03472 and British patent application no. 9726873.4 are point-to-point using substantially unidirectional transmissions for transmission and reception on a link, i.e. signals are not broadcast but are instead directed to a particular node with signals being capable of being passed m both directions along the link, it is important that the antennae horns of linked nodes be properly and accurately aligned so that transmission from one node to a linked node is properly and completely received. Alignment of the antennae horns is m practice difficult, especially as the linked nodes may be a kilometre or more apart from each other. In principle, the nodes to which a particular node is linked may be located m any direction. The number of nodes to which a particular node is linked is also initially unknown. Furthermore, new nodes m any arbitrary location may be added to the communication apparatus at any time as the communication apparatus develops. Accordingly, it is beneficial to be able to provide substantially 360° azimuthal transmission and reception coverage at each node and then select only particular directions for actual transmission/reception links with other nodes. This can be achieved by providing more antennae horns at each node than there are links at that node. For example, where eight links to and from a node are required, it may be convenient to provide thirty-two antennae horns which together provide 360° coverage in a substantially horizontal plane. For each link direction, at least one of those thirty-two antennae horns is likely to be facing m the appropriate direction so that that particular horn can be selected for providing a transmission/reception link with a neighbouring node. The problem with providing many antennae horns at a particular node is that the cost of the switch that is used for switching between the antennae horns becomes significant. The performance of the switch can also suffer when it is expected to switch between many horns. This is particularly the case at the high frequencies contemplated for the communication apparatus disclosed in PCT/GB97/03472 and British patent application no. 9726873.4 in which frequencies of 1 GHz or higher such as 2.4 GHz or 4 GHz or 40 GHz or 60 GHz or 200 GHz or higher are proposed. Also, at these high frequencies, it is important that the apparatus be as small as possible, with the radio components being positioned close to the antennae horns in order to minimise losses in the couplings. Accordingly, there is a need for apparatus which provides multiple antennae in which the radio components can be positioned close to the antennae and which provides for switching between the multiple antennae at low cost but with high performance. According to a first aspect of the present invention, there is provided transmitter apparatus, the apparatus comprising: a plurality of sets of substantially unidirectional antennae; each set of antennae having a single radio subsystem for providing a radio output signal for transmission by one of the antennae in the set; each of the plurality of radio subsystems having a switch for switching the output of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected for transmission of a radio signal output by the radio subsystem from said selected antenna. According to a second aspect of the present invention, there is provided receiver apparatus, the apparatus comprising: a plurality of sets of substantially unidirectional antennae; each set of antennae having a single radio subsystem for receiving a signal received by one of the antennae to provide an output signal from the radio subsystem; each of the plurality of radio subsystems having a switch for switching an input of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected such that a signal received by said selected antenna is passed as an input to the radio subsystem. According to a third aspect of the present invention, there is provided transceiver apparatus, the apparatus comprising: a plurality of sets of substantially unidirectional antennae; each set of antennae having a single radio subsystem for providing a radio output signal for transmission by one of the antennae in the set and for receiving a signal received by one of the antennae to provide an output from the radio subsystem; each of the plurality of radio subsystems having a switch for switching the output of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected for transmission of a radio signal output by the radio subsystem by said selected antenna and for switching an input of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected such that a signal received by said selected antenna is passed as an input to the radio subsystem. The present invention in its various aspects allows radio subsystems to be shared between multiple antennae, keeping down the costs, whilst allowing each radio subsystem to be positioned close to the antennae which are served by that radio subsystem. At the same time, the number and complexity of the switches is also optimised to keep down costs whilst ensuring high performance. In the third aspect, each radio subsystem may be arranged to switch between reception and transmission modes using time division duplex. At least one of the radio subsystems may be arranged to operate at a first frequency for signals input to the radio subsystem from the antennae and at a second frequency for signals output by the radio subsystem to the antennae. Said at least one radio subsystem may be arranged to receive and transmit signals substantially simultaneously. In any of the aspects mentioned above, the antennae are preferably arranged to provide 360° azimuthal coverage. This greatly facilitates set-up and maintenance of radio transmission links between apparatus according to the present invention. The antennae are preferably arranged in a circular array in which all of the antennae are directed away from a common origin. Again, this greatly facilitates set-up and maintenance of radio transmission links between apparatus according to the present invention. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a schematic plan view of a first example of apparatus according to the present invention; Fig. 2 is a schematic side elevation of the apparatus of Figure 1 with some of the antennae horns removed for clarity; Fig. 3 is a more detailed plan view of a portion of the apparatus of Figure 1; Fig. 4 is a block circuit diagram showing an example of a radio subsystem using TDD; Fig. 5 is a block diagram showing a radio subsystem and a switch; and, Fig. 6 is a block circuit diagram showing an example of a radio subsystem using FDD. Referring to the drawings, and particularly Figures 1 to 3, transceiver apparatus 1 includes thirty-two antennae horns 2. The antennae horns 2 are arranged in a single plane and are all directed away from a common origin 0 to provide a circular array of the horns 2 which therefore provide substantially 360° coverage in the plane in which the horns 2 lie. The horns 2 are grouped into eight sets A-H each consisting of four horns 2. Each horn 2 within a set A-H is connected to the same radio subsystem 3 at the base of the horn 2 by means of a suitable connection 4. Thus, a single radio subsystem 3 is provided for each of plural antennae horns 2 in the apparatus 1. In the specific example, where there are thirty-two horns 2 divided into eight sets A-H, there are eight radio subsystems 3, i.e. one radio subsystem 3 for each set A-H of four horns 2. In Figure 3, four horns 2 of a set A-H are shown subtending an angle of 90° as a variation to four horns 2 of a set subtending an angle of 45° as shown in Figure 1. The eight radio subsystems 3 are all mounted on a single radio board 5. The single radio board 5 receives an intermediate frequency (IF) signal from an IF subsystem 6. The IF subsystem 6 in turn receives power 7 from a power source (not shown) and transmits baseband signals 8 to and receives baseband signals 8 from apparatus (such as a computer, not shown) associated with the apparatus 1. Figure 4 shows a radio subsystem 3 in more detail . The radio subsystem 3 shown m Figure 4 uses time division duplex (TDD) to alternate transmission and reception within a time frame. The radio subsystem 3 is shown m Figure 4 as configured for transmission. An input IF signal 10 is passed from the IF subsystem 6 through the radio board 5 to a first switch 11 of the radio subsystem 3. As mentioned above, the radio subsystem 3 is shown m Figure 4 as configured for transmission. Accordingly, the first switch 11 is set so that the input IF signal passes to a first mixer 12 where it is mixed with a carrier frequency signal from a multiplier 13 which has an input 14 from a local oscillator (not shown) . The output of the first mixer 12 passes to a power amplifier 15 where it is amplified to a power suitable or required for transmission. The output from the power amplifier 15 passes to a second switch 16 which is set so that the amplified signal output by the power amplifier 15 is passed as an output signal 17 from the radio subsystem 3. When the radio subsystem 3 is in reception mode, a received signal 17 passes to the second switch 16 which has been switched to the lowermost position m Figure 4 so that the received signal 17 is passed to a low-noise amplifier 18. The low-noise amplifier 18 amplifies the received signal and passes it to a down converter 19 which also receives as an input signal the local oscillator input 14 passing via the multiplier 13 and the mixer 12. The received signal is thereby down converted in the down converter 19 to an intermediate frequency signal. The IF signal from the down converter 19 is passed to the first switch 11. The first switch 11 has already been set to the lowermost position in Figure 4 so that the IF signal passes as an output 10 from the radio subsystem 3. Operation of the first and second switches 11,16 can be under the control of a clock signal passed to the first and second switches 11,16. It will be appreciated that the switching of the switches 11,16 is synchronised with the expected transmission and reception times for the antennae horn or horns 2 to which the radio subsystem 3 is connected according to the time division duplex frame. Referring to Figure 5, the transmission output/reception input 17 of each radio subsystem 3 is connected to its own radio switch 20. The radio switch 20 can selectively switch the transmission output/reception input 17 of each radio subsystem 3 between one of four input/output connections 21 of the switch 20. Each of the four input/output connections 21 of the switch 20 is connected via a horn connection 4 to a respective antennae horn 2. In a specific example, where the transmission carrier frequency is in the GHz range, the switch 20 and horn connections 4 to the antennae horns 2 are implemented by means of a microwave monolithic integrated circuit (MMIC) . The horn connections 4 are designed to allow maximum transfer of RF power between the switch 20 and the horns 2. It is especially important that the radio subsystem 3 be positioned close to the antennae horns 2 in such a case. This is because it is important to minimise the length of the horn connections 4 so as to minimise power losses and interference, as well as making the apparatus 1 as compact as possible. It will be appreciated that a MMIC radio subsystem 3 will typically only be approximately 1mm by 1mm in size. Losses in signal strength between the horns 1 and ' the radio subsystem 3 can be considerable if the horn connections 4 are of the wrong geometry or insufficiently compact . The communications system operator or the users associated with the nodes can install at each node a single antennae array apparatus 1 having plural horns 2 to provide 360° coverage. A set-up procedure can be followed whereby for example the node automatically sends out test signals through each of the horns 2 in turn by appropriate operation of the radio switches 20 for each set A-H of horns 2. When the appropriate horn 2 has been located for transmission and/or reception (i.e. in this example, when a point-to-point radio transmission link with another node has been established through a particular horn 2) , the position of the radio switch 20 can be fixed so that that particular horn 2 is always selected for transmission or reception out of the four horns 2 which comprise a particular sector A-H. Alternatively, where different horns 2 within the same sector A-H are to be used for transmission and/or reception at different times, a clock signal to the radio switch 20 can be provided to operate the radio switch 20 so that the correct horn 2 is selected at the appropriate times. Thus, manual set-up and manual alignment of the antennae horns 2 can be avoided. The array of antennae horns 2 can be reconfigured without requiring manual adjustment of the direction of the antennae horns 2 as the various switches 20 can simply be controlled so that different antennae horns 2 are selected and used for transmission and reception as required. This is especially advantageous when the communications apparatus is in use as new nodes can be added at any time and will need to be linked to other nodes. Moreover, a link between a particular pair of nodes may be lost for some reason (perhaps because of a temporary obstruction, for example) and the affected nodes can be reconfigured to transmit and receive along links to other nodes via different antennae horns. In Figure 6, there is shown a radio subsystem 3 which uses frequency division duplex (FDD) to separate transmissions and receptions. Components which are the same as in the TDD radio subsystem 3 shown in Figure 4 have the same reference numerals. An input IF signal 10A is passed to a first mixer 12 where it is mixed with a carrier frequency signal having a first frequency Vi from a multiplier 13 which has an input 14 from a local oscillator (not shown) . The output of the first mixer 12 passes to a power amplifier 15 where it is amplified to a power suitable or required for transmission. The output from the power amplifier 15 passes to a frequency diplexing filter 22 from where it is passed as an output signal 17 at the first frequency v_ from the radio subsystem 3. The output signal 17 is passed to a switch 20 as described above with reference to Figure 5. When a radio signal, which is at a different frequency v 2, is received at an antennae horn 2, the received signal 17 passes to the frequency diplexing filter 22. The received signal at frequency v 2 is filtered out by the diplexing filter 20 and passed to the low-noise amplifier 18 where it is amplified and passed to the down converter 19. The down converter 19 down converts the received signal at the second frequency v 2 and passes the down converted signal as an output 10B from the radio subsystem 3. The present invention provides low cost but high performance switching between plural antennae horns 2. Substantially 360° coverage can be obtained without requiring precise manual adjustment and alignment of the antennae horns 2 simply by operating the switches 20 appropriately. The radio subsystems 3 can be positioned close to the antennae horns 2, thereby minimising power losses and interference. It will be appreciated that, in the specific example described above, there are thirty-two antennae horns divided into eight sectors A-H of four horns each. Each sector of four horns has its own radio subsystem 3 which can be selectively connected to one of the horns by means of a four-way radio switch. More generally, where there are N antennae to address, this can be achieved with M radio subsystems and M S-way switches where N = M x S. An embodiment of the present invention has been described with particular reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention. For example, as an alternative to TDM, frequency division multiplexing (FDM) or other techniques such as code division multiplexing (CDM) may be used provided that not all antennae horns are required to be active at any one time so that radio subsystems can be shared and appropriate switches employed. Further, the arrangement of the horns 2 may be different to that described above and shown in the drawings. For example, there may be thirty horns 2 arranged in two stacked layers of fifteen horns 2 each. The horns 2 of one layer can be rotated by 12° (i.e. half a horn) in a horizontal plane relative to the horns 2 of the other layer. Other arrangements to provide 360° coverage are possible.

Claims: CLAIMS 1. Transmitter apparatus, the apparatus comprising: a plurality of sets of substantially unidirectional antennae; each set of antennae having a single radio subsystem for providing a radio output signal for transmission by one of the antennae in the set; each of the plurality of radio subsystems having a switch for switching the output of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected for transmission of a radio signal output by the radio subsystem from said selected antenna. 2. Receiver apparatus, the apparatus comprising: a plurality of sets of substantially unidirectional antennae; each set of antennae having a single radio subsystem for receiving a signal received by one of the antennae to provide an output signal from the radio subsystem; each of the plurality of radio subsystems having a switch for switching an input of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected such that a signal received by said selected antenna is passed as an input to the radio subsystem. 3. Transceiver apparatus, the apparatus comprising: a plurality of sets of substantially unidirectional antennae; each set of antennae having a single radio subsystem for providing a radio output signal for transmission by one of the antennae in the set and for receiving a signal received by one of the antennae to provide an output signal from the radio subsystem; each of the plurality of radio subsystems having a switch for switching the output of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected for transmission of a radio signal output by the radio subsystem by said selected antenna and for switching an input of the radio subsystem to a selected one of the antennae in the set to which the radio subsystem is connected such that a signal received by said selected antenna is passed as an input to the radio subsystem. 4. Apparatus according to claim 3, wherein at least one of the radio subsystems is arranged to switch between reception and transmission modes using time division duplex. 5. Apparatus according to claim 3 or claim 4, wherein at least one of the radio subsystems is arranged to operate at a first frequency for signals input to the radio subsystem from the antennae and at a second frequency for signals output by the radio subsystem to the antennae. 6. Apparatus according to claim 5, wherein said at least one radio subsystem can receive and transmit signals substantially simultaneously. 7. Apparatus according to any of claims 1 to 6 , wherein the antennae are arranged to provide 360° azimuthal coverage . 8. Apparatus according to any of claims 1 to 7 , wherein the antennae are arranged in a circular array in which all of the antennae are directed away from a common origin.

Inventors: FITZ STEPHEN MARK, FITZ, STEPHEN, MARK
Applicants: FITZ STEPHEN MARK, RADIANT NETWORKS PLC, FITZ, STEPHEN, MARK
Application year: 1999
Main classification: H04B7
IPC codes: H04B7