TRANSMITTER COMBINER ARRANGEMENT

Abstract: The invention relates to a transmitter combiner arrangement, and more specifically a transmitter combiner arrangement usable in communication systems transmitting signals with a wide dynamic range, e.g. in a base station of a multilobe telecommunication system having phased array antennas. The transmitter arrangement according to the invention enables amplification of low and high levels with high efficiency by means of a hybride arrangement comprising a hybride of progressively coupled single carrier power amplifiers (SCPA) and a multicarrier power amplifier (MCPA) connected with a combiner network.

Description: TITLE OF INVENTION: TRANSMITTER COMBINER ARRANGEMENT FIELD OF THE INVENTION The present invention relates to a transmitter combiner arrangement, and more specifically a transmitter combiner arrangement usable in a base station of a multilobe telecom- munication system having phased array antennas. However, the invention is not limited to such a system, but is very use¬ ful with systems having a large dynamic range, e.g. up to 110 dB or more. The transmitter arrangement according to the invention enables amplification of low and high levels with high efficiency by means of a hybride arrangement combining efficient single carrier power amplifiers (SCPA) and high power multicarrier power amplifiers (MCPA) . STATE OF THF, ART Single carrier power amplifiers are known amplifier circuits having high efficiency at maximum output power but are, of course, used for only one carrier frequency at a time. Today it is conventional to combine such SCPAs with filter combiners. It is also conventional to use SCPAs with 3 dB combiners. However, power is lost in the combiner re¬ sulting in low efficiency and high current consumption, which means high costs . The multicarrier power amplifier is a known amplifying circuit having high power but low efficiency. The advantage of this circuit is that it may accomodate many channels. However, they are expensive and difficult to implement when different carriers are at different levels, such as when power control is used or in phased array antennas. The problems stated above are solved by the present invention by using single carrier power amplifiers in a progressive coupling, which enhances efficiency compared to a 3 dB combiner amplifier. This is combined with a multi- carrier power amplifier for lower power carriers. This re¬ duces costs significantly compared to high power MCPA. For enhanced capacity the invention features an expansion input. SUMMARY OF THE INVENTION Thus, the present invention provides a transmitter combiner arrangement comprising a hybride of progressively coupled single carrier power amplifiers and a multicarrier power amplifier connected with a combiner network. The invention is set forth in detail in the accompanying claims. BRIEF DESCRIPTION OF THE DRAWINGS The invention is described below with reference to the accompanying drawings, in which Figure 1 is a block diagram of a first embodiment of the invention including progressively coupled single carrier power amplifiers and a multicarrier power amplifier con¬ nected by a combiner network; Figure 2 is a block diagram of another embodiment of the invention in which single carrier power amplifiers are connected by a filter bank; Figure 3 is a block diagram of a further embodiment- of the invention in which single carrier power amplifiers are connected by the filter bank and a 3 dB combiner; Figure 4A is a block diagram of a preferred embodiment of a single carrier power amplifier according to the inven- tion; and Figure 4B is a block diagram of a possible implementa¬ tion of a single carrier power amplifier. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS As is mentioned above, the transmitter combiner arrangement according to the present invention is suitable for use in communication systems that transmit signals with a wide dynamic range. In a multilobe system with a phased array antenna, the power is distributed to many radiating elements, and in order to obtain low sidelobe levels, the power sent to the different radiating elements may vary 30 dB . In a base station, it is also desirable to use power control in order not to send out more power than necessary, the usable power being about 80 dB. This leads to a require- ment for dynamic range of 110 dB. As the requirement for suppression of intermodulation is 60-70 dB depending on the application, the requirement for intermodulation product suppression with this dynamic range is 170-180 dB, which is not achievable with an ordinary MCPA. The base station includes a lobe-shaping unit for con¬ trolling the signals to the phased array antenna. A base station controller in turn controls the base stations of the telecommunication system. The lobe-shaping unit and the base station controller do not form any parts of the present in- vention. In Figure 1 is shown a preferred embodiment of the pre¬ sent invention. As may be seen the transmitter arrangement includes a number of SCPAs connected by transmitter combiner circuits WILKD3DB, which may be of the conventional Wilkin- son 3dB type, in a step arrangement having equal attenuation steps. Thus, the top SCPA will be able to furnish the lowest output power. In front of the SCPAs are variable attenuators WA. The inputs to the various SCPAs are arranged according to the input level or power requirement, such that the correct output power is obtained at the. output. At the top transmitter combiner is a further expansion input for additional low power channels. The transmitter arrangement also comprises a multi- carrier power amplifier. In front of the MCPAs is a combiner network, which may consist of transmitter combiners or a resistive combiner network. The combiner network is pre¬ ferably symmetrical, such that the gain through the ampli¬ fiers is the same independent of input port. The MCPA is suitable for amplifying many low levels since these will not generate important intermodulation products. The SCPAs and the MCPA are combined in a final trans¬ mitter combiner. At the output of the MCPA is a detector for providing information to a control unit. The control unit controls the various amplifier units of the SCPAs and the MCPA by pro- viding the correct input voltage and input currents, i.e. the bias of the amplifier units. Thus the efficiency of the amplifiers can be optimised. The control unit also receives input information from a base site controller and a lobe- shaping unit, if the transmitter combiner arrangement according to the invention forms part of such a telecommu¬ nication system. In Figure 2 is shown another embodiment of the present invention. In this embodiment the SCPAs are connected by a filter bank to the final transmitter combinex. The filters of the filter bank are connected by λ/4 and λ/2 transmission lines to the combiner for correct addition at the combiner. In Figure 3 is shown an embodiment of the invention featuring only SCPAs combined with filters. This embodiment is useful when it is desired to amplify many similar high level signals. It is especially advantageous with a pre¬ ferred embodiment of a single carrier power amplifier according to the present invention as described below with reference to Figures 4A and B. In Figure 4A is shown an especially advantageous form of a single carrier power amplifier having variable power and amplification levels. As may be seen, the amplifier comprises a number of amplifier units AMP which may be en¬ abled by setting a corresponding number of switches. The amplifier unit at the far left can only output low signal levels. When a higher signal levels are required, the middle amplifier is also enabled as it can supply medium output " levels. At high output levels, also the amplifier unit at the far right is enabled being able to supply high output levels. When the middle or right-hand amplifiers are disabled, their biases are turned off so that the power consumption is considerably reduced and the signal is by¬ passed. With this arrangement, the efficiency of the amplifier is maintained fairly independent of the output signal level. Also, the amplifier arrangement achieves 60 dB gain control. This is achieved by varying the bias of the amplifiers. A voltage variable attenuator WA is used to fine tune the gain. Figure 4B shows a possible implementation of the amplifier circuit including switchable PIN diodes and λ/4 transmission lines MTRL. The present invention has been described with reference to the disclosed embodiments in great detail. However, many variations and modifications of the embodiments may be app¬ reciated by a person skilled in the art. The invention is only restricted by the scope of the claims below.

Claims: CLAIMS 1. A transmitter combiner arrangement, characterised by a hybrid of progressively coupled single carrier power amplifiers (SCPA) and a multicarrier power amplifier (MCPA) connected with a combiner network. 2. A transmitter combiner arrangement according to claim 1, characterised in that the single carrier power amplifiers are coupled in equal steps by transmitter combin¬ ers, e.g. of Wilkinson type. 3. A transmitter combiner arrangement according to claim 1 or 2, characterised in that the combiner network of the multicarrier power amplifier is symmetrical for equal amplification of the multicarrier power amplifier channels. 4. A transmitter combiner arrangement according to any one of claims 1 to 3 , characterised by having an expansion input for adding more single carrier power amplifiers . 5. A transmitter combiner arrangement according to any one of the preceding claims, characterised by a control unit receiving information from a detector connected to the out- puts of the single carrier power amplifiers and the multi- carrier power amplifier for controlling the bias of the amplifier units of the single carrier power amplifiers and the multicarrier power amplifier. 6. A transmitter combiner arrangement according to claim 5, characterised in that the control unit receives information from a base site controller (BSC) and/or a lobe shaping unit of a multilobe telecommunication system. 7. A transmitter combiner arrangement, characterised by a hybrid of single carrier power amplifiers (SCPA) coupled by a filter bank and a multicarrier power amplifier (MCPA) connected with a combiner network. 8. A single carrier power amplifier, characterised by an assembly of a plurality of amplifier units having a high efficiency for varying input levels, wherein the amplifier units are enabled progressively by switches for varying output powers . 9. A single carrier power amplifier according to claim 8, characterised in that the switches of the amplifier circuit include switchable PIN diodes and λ/4 transmission lines (MTRL) . 10. A transmitter combiner arrangement according to any one of claims 1 to 7, characterised by a single carrier power amplifier according to claims 8 or 9.

Inventors: JOHNSON TORBJOERN, MALMGREN JENS, JOHNSON, TORBJOERN, MALMGREN, JENS
Applicants: JOHNSON TORBJOERN, MALMGREN JENS, RADIO DESIGN INNOVATION AB, JOHNSON, TORBJOERN, MALMGREN, JENS
Application year: 1997
Main classification: H04B1
IPC codes: H01Q3, H01Q23, H03F1, H03F3, H03G1, H03G3, H04B1