The present invention relates in general to a combiner for electromagnetic waves, for example, in a radio base station. In addition, the invention relates to a unit for a combiner and to a radio base station with one or more such combiners.
In, for example, radio base stations, combiners are used for feeding and filtering of, for example, microwaves of particular frequencies from different transmitters to a shared antenna in order to prevent signals of a particular frequency from one transmitter affecting signals from another transmitter and in order that the signals should reach the antenna without being attenuated too much. A combiner comprises several cavity filters, such as waveguide filters, coaxial filters or ceramic filters, which are each connected to their respective transceiver by a lead. From the cavity filters an output signal is taken out and led to the shared antenna via, for example, coaxial cables belonging to a star connection and a shared bandpass filter.
U.S. Pat. No. 5,440,281 A describes a combiner in a radio communication system for mobile telephony and is hereby incorporated as a reference. Each cavity filter in the device described comprises a tuner, the position of which in relation to a resonator body can be varied for setting a resonance frequency for each cavity filter. This setting is carried out manually, which is not suitable for many applications where there is a need to change the resonance frequency of the cavity filters frequently. Therefore modern cavity filters are provided with a motor that is controlled by an automatic or remote-controlled control unit. In addition, modern combiners comprise sensor units for taking measurement values, such as temperature and current, which measurement values are processed by the control unit. In addition, devices are included for protecting the transceivers from generating harmful intermodulation products and for suppressing the transmission of intermodulation products to the antenna. These devices are designed to pass current/power in one direction but to prevent current in another direction. Examples are circulators and insulators, where losses in one direction are much greater than losses in another direction. Throughout the remainder of this Application, the devices for protecting the transceivers are called xe2x80x9cinsulatorsxe2x80x9d. These insulators can produce a relatively large amount of heat that must be dissipated and they must also be screened carefully in order not to interfere with surrounding electrical and electronic components and signals. The insulators are therefore each housed in separate casings designed to provide sufficient screening and because of a lack of space the insulators are positioned on different sides of the cavity filters, which makes the cooling difficult. Regarding radio base stations, there are standardized dimensions for how much space the combiners can take up. Present configurations mean that a large number of coaxial cables must be used to connect together among other things cavity filter, sensor unit, control unit and insulators. The limited space, together with the many combiners and their associated coaxial cables, means, for example, that inspection, assembly, repairing and cooling of the combiners can be made more difficult.
A first aim of the present invention is to achieve a combiner that allows more simple assembly, manufacture, repairing and inspection of the combiner.
A second aim is to achieve a combiner that allows better cooling of the components incorporated therein.
A third aim is to improve the performance of a combiner, both mechanically and electrically.
A fourth aim is to reduce the effect of both electrical fields and magnetic fields that the different units generate and with which they affect each other.
A fifth aim is to increase the reliability of a combiner and thereby of a radio base station.
A sixth aim is to increase the number of variants of combiners that can fit in a radio base station of standard dimensions. Additional aims, advantages and effects will be apparent from the following description.
The invention relates to a combiner for electromagnetic waves. The combiner comprises a first unit and a second unit, where the first unit comprises
a first casing;
at least two component arrangements, each comprising
a connector connected to the first casing and designed to make a connection with a device for the transmission of electromagnetic waves,
at least one insulator connected to the connector and enclosed in the first casing and
an input device which is connected to the insulator;
at least one screen between the insulators, for screening electromagnetic fields; and
at least one first circuit board with at least one sensor, where the first circuit board is at least partially housed in the first casing;
and where the second unit comprises
a second casing that defines a cavity for electromagnetic waves for each of the input devices, and
at least one output device for tapping electromagnetic waves from at least one of the cavities.
By this means, a compact combiner is achieved with a single common casing for insulators, input devices and circuit board for taking measurement values. By achieving a smaller combiner for a required frequency, more combiners can be fitted into a radio base station with standardized internal dimensions, as well as more variants of combiners. As the insulators, input devices and the circuit board are assembled in the same casing, a better precision is achieved between the parts compared to if these components had been assembled in different casings. The improved precision makes it easier to calibrate the interaction between these components concerning, for example, a common impedance, and it is easier to obtain the required accuracy in the signals that are to pass through these components. The collecting of the insulators in a single casing also means that a cooling medium only needs to be taken past the first casing for cooling purposes, and not past several casings that are usually located at a distance from each other. In addition, the number of cables is reduced for the combiner, which among other things means that the combiner is cheaper to manufacture and that the power losses in the combiner are smaller.
The first casing suitably comprises a first casing element and a second casing element, where at least the second casing element is provided with at least a first cooling fin and the insulators are in contact with the second casing element. By this means, improved cooling of the first casing and the insulators is achieved.
The input devices are preferably partially enclosed in the first casing and partially enclosed in the second casing. By only the first and the second casing being involved in the fixing of the input devices, the precision of the very important position of the input devices in the cavity is improved, as few components result in smaller tolerances.
In order to be able to connect the input devices to the respective cavity in a simple way, the second casing comprises a third casing element with through-openings to receive the input devices, the number of which openings is the same as the number of input devices.
The third casing element comprises at least one integral external conduit that acts as an outer conductor for the output device for connection to, for example, a star connection, where both the conduit and the output device extend away from the cavities. By this means, the output device can be connected to a star connection in a secure way at a distance from the cavities, which makes the assembly of the combiner even easier.
The combiner preferably comprises a third unit, where the third unit comprises:
a third casing,
a second circuit board with a CPU for receiving and processing measurement signals from the first circuit board and for controlling motors, the number of which is the same as the number of cavities, for moving tuners in the cavities, and at least one port designed for a cable to an external computer unit or display screen. By this means, a combiner is achieved that, for example, can process measurement values and automatically or upon command from the external computer unit, control the motors so that they set the required resonance frequency in any of the cavities.
The third casing preferably comprises at least one second cooling fin and the second circuit board comprises at least one memory for data. By this means, improved cooling of the second circuit board and the ability to save measurement values or other information in the memory are achieved.
The combiner preferably comprises at least one connecting circuit board that is connected between the first circuit board and the second circuit board and that thereby enables measurement signals from the first circuit board to be sent to the second circuit board. By this means, an even more reliable combiner is achieved, as cables must otherwise be used.
The first casing and the third casing are suitably fixed to the second casing on the third casing element in such a way that the port, connectors and output device are pointing in the same direction and situated essentially in the same plane. By this means, a common front is obtained for the three units, to which input signal cables, power supply cables, data cables to the CPU and output cables can easily be attached.
In order for the combiner to be suitable for a radio base station for the transmission of microwaves, the combiner comprises resonators, the number of which is the same as the number of cavities.
The output device preferably comprises a coaxial conductor and a loop, which is inserted into two of the cavities to tap off electromagnetic waves.
The output device is suitably designed to be connected to a star connection that leads to a bandpass filter. By this means, for a conventional star connection, at least two output signals from one or more units of the same type as the second unit according to the present invention are sent to a bandpass filter in a common cable.
The present invention also relates to a radio base station that comprises at least one of the combiners described above.
In addition, the present invention relates to a unit for a combiner, comprising
a casing;
at least two component arrangements, each of which comprises
a connector connected to the casing and designed to make a connection with a device for the transmission of electromagnetic waves, at least one insulator connected to the connector and enclosed in the casing and an input device which is connected to the insulator;
at least one screen between the insulators, for screening electromagnetic fields; and
at least one circuit board with at least one sensor, where the circuit board is at least partially housed in the casing.
In order to reduce the manufacture of different parts and thereby reduce the tolerances between the screen and the insulators, the screen is integrated into the second casing element.
The casing suitably comprises guide pins and the circuit board suitably comprises corresponding guide holes or recesses for the guide pins, in order to make it easier to guide the control card during assembly.
The input devices can preferably be inserted into the casing from outside through openings in the casing intended for the input devices, even when the two casing elements are fixed to each other. In addition, the unit comprises conductors, the number of which is the same as the number of connectors, which conductors connect the connectors to the respective insulator.
Each of the conductors is preferably located at least partially in its respective recess in the casing, and sensor devices, the number of which is the same as the number of conductors, for recording the direction of the current/power that passes through the conductors, are comprised in the circuit board and placed on the circuit board in such a way that each recess has at least one of the sensor devices essentially directly above it. By this means, a unit is achieved that can read off the power/current that arises in the respective conductors.
The sensor devices are preferably directional connectors, such as directional couplers. In addition, the unit comprises temperature sensors, preferably arranged on the circuit board, for sending warning signals if the temperature should become too high in the unit.