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1 INTEGRATED CIRCUIT AND METHOD FOR RECEPTION OF RADIO FREQUENCY SIGNALS
BACKGROUND OF THE INVENTION
The invention is based on the priority application EP 07290252.1 which is hereby incorporated by reference.
The present invention relates to an integrated circuit for reception of radio frequency signals in an antenna network system, to an antenna network circuit, to a method for reception of antenna signals, and to a base station for a cellular telecommunications system.
Antenna network circuits, as used for instance in base stations for cellular communication systems, comprise low noise amplifiers (LNA) boards for amplifying received radio frequency, RF, signals.
Existing LNA boards, in particular LNA boards for diversity (i.e., multiple parallel) reception of RF signals, are dedicated to a single specific frequency bandwidth or standard and use discrete components. In this way, a completely new development of the LNA board is required when changing equipment or when moving to a new bandwidth or standard. Moreover, the fact that known LNA boards are designed based on using discrete parts, e.g., a digital processing unit (CPU) and unitary components such as transistors, varactors, PIN diodes, resistors, capacitors and inductors, the part count and overall costs are high, especially if two identical structures are necessary for diversity reception, as required for instance by GSM. Furthermore, building up an LNA board from discrete parts requires considerable tuning and adjustments on board before a corresponding solution is ready for manufacturing. Due to their assembly from discrete parts, known LNA boards show an elevated consumption of both space and power, which presents an issue for the design of future equipment.
Altematively, the Low Noise Amplifier function (LNA function) is designed by combining several transistor stages in a single full-custom module, i.e., dies wire-bond on a ceramic (i.e. alumina) substrate and other components assembled in a unique custom package. This is again a full custom design for on particular frequency and standard having the above-mentioned disadvantages.
It is the object of the present invention to provide an integrated circuit for reception of radio frequency signals in an antenna network system as well as a method for antenna signal adaptation which allow to address multiple bandwidths or standards in order to cover a wide range of antenna system equipment while providing a significant cost reduction of the LNA function. Furthermore, integration of the LNA function in an antenna network architecture shall be simplified by reducing the part count and power dissipation.
According to a first aspect of the present invention the object is achieved by providing an integrated circuit for reception of radio frequency signals in an antenna network, the IC comprising: a plurality of amplifying paths to cover a plurality of radio frequency, RF, bandwidths or standards, each amplifying path comprising at least one low noise amplifier, at least one variable attenuator unit (or adjustable/variable gain element), and/or at least one gain flattening unit, each of the low noise amplifier, the variable attenuator unit, and the gain flattening unit being adapted to operate at a respective
radio frequency bandwidth or standard; at least one control interface connected with at least one of the low noise amplifier, the variable attenuator unit, and the gain flattening unit in each amplifying path and adapted for communication with a digital processing unit to control operation of the at least one of the low noise amplifier, the variable attenuator unit, and the gain flattening unit.
In one embodiment of the integrated circuit in accordance with the present invention, to address said antenna network, two identical sets of amplifying paths or amplifying RF paths (‘A’ and ‘B’) are integrated in one chip for diversity reception of antenna signals. Alternatively, for ease of integration on board the chip may include only one set of amplifying paths, and the chip will be used twice for applications which require diversity reception. An advantage of this is to improve ASIC power dissipation, with reference to standard packaging, such as QFN package for instance.
According to a second aspect of the present invention the object is achieved by providing an antenna network circuit comprising the integrated circuit according to said first aspect of the present invention in connection with a first amplifier stage having at least one low noise amplifier, said first amplifier stage being connected with the integrated circuit so that the low noise amplifier of the first amplifier stage is connected with an active one of the amplifying paths in the integrated circuit.
According to a third aspect of the present invention the object is achieved by providing a method for reception of antenna signals, the method comprising: receiving a radio frequency, RF, antenna signal; selectively providing said RF antenna signal to one of a plurality of amplifying paths, each of said amplifying paths covering a dedicated RF bandwidth or standard and comprising at least one low noise amplifier, at least one variable attenuator unit, and/or at least one gain flattening unit, each of the low noise amplifier, the variable attenuator unit, and the gain flattening unit being operated at a respective RF bandwidth or standard and implemented inside an integrated circuit; and controlling gain and/ or flatness of the amplifying path by means of a digital processing unit through at least one control interface.
According to a fourth aspect of the present invention the object is achieved by providing a base station for a cellular telecommunications system, the base station comprising an antenna network circuit according to said second aspect of the present invention.
Preferred embodiments of various aspects of the present invention are comprised in the dependent claims, the wording of which is herewith incorporated by reference in the present description to avoid unnecessary repetition of text.
By means of embodiments in accordance with the present invention, multiple bandwidths for covering a wide range of (diversity) antenna systems equipment can be addressed with a single LNA integrated circuit or module which may include the complete electronics for digital control, thus providing a significant cost reduction of the LNA function. Furthermore, embodiments of the present invention add flexibility to various antenna systems by re-using the same part reference for new equipment and/or a new frequency bandwidth or standard. Furthermore, the present invention achieves reduction of the part count and power dissipation.
Embodiments of the present invention, in particular embodiments comprising an additional first amplifier stage connected with the integrated circuit, can be easily adapted with respect to their RF performance to match the constraints of the antenna system, e.g., very low noise, variable gain over a wide range, high linearity capability (e.g., IP3), while supporting as many integrated LNAs as required for covering
different frequency bandwidths or standard. Said bandwidths or standard include (without limitation) AMPS, EGSM, DCS, PCS, UMTS, etc. Embodiments in accordance with the present invention are also well suited to address different bands of WIMAX (Worldwide Interoperability for Microwave Access). Using a suitable design of amplifying paths, embodiments of the integrated circuit or the antenna network circuit in accordance with the present invention are able to integrate WIMAX bands in conjunction with, e.g., UMTS.
For supporting one dedicated application standard, the associated amplifying path is powered up by means of a corresponding control command issued by the digital processing unit, e.g., for powering up the associated LNA on said amplifying path which may also be referred to as “active” amplifying path. In order to reduce power consumption, the other LNAs (on different amplifying paths) are kept in power down mode. A dedicated application program as well as necessary application data is downloaded to a memory section of the digital processing unit. According to embodiments of the present invention, said memory unit or memory section can be arranged either internally or extemally of the integrated circuit. According to an embodiment of the present invention, the digital processing unit is comprised within the integrated circuit. In this case, for reasons of manufacturing and cost reduction, said memory section or memory unit is preferably located externally of the integrated circuit.
According to further embodiments of the present invention, said memory unit can be devised as a flash memory. However, the present invention is not limited to such an embodiment of the memory unit which generally may take on the form of any Electrically Erasable Programmable ReadOnly Memory (EEPROM).
The digital processing unit as used in embodiments of the present invention is able to handle gain tumng and flattening performed by the various elements on an active amplifying path (i.e., LNA, variable attenuator, gain flattening unit) and to manage additional system requests, such as alarm, gain and signalling status, requests for hardware type, software version, etc.
In accordance with further embodiments of the present invention the integrated circuit includes a temperature sensor for providing temperature data to the digital processing unit. Correspondingly, the digital processing unit is able to process temperature data provided by the temperature sensor for compensating temperature effects and may thus adjust gain on said amplifying paths by suitably controlling the corresponding variable attenuator.
In accordance with further embodiments of the present invention the integrated circuit is designed to match with requirements for outdoor equipment, i.e., to cover a temperature range from —55° C. to +85° C.
As already stated above, in accordance with embodiments of the present invention the integrated circuit may be preceded by a further LNA stage (hereinafter also referred to as “on-board” LNA stage) to achieve optimum performance. Keeping an on-board LNA stage in combination with an integrated amplifying path has the advantage that different manufacturing technologies can be used for providing the on-board LNA stage on one hand and the integrated amplifying path (or amplification stage) on the other hand. For instance, GaAs technology may be used in connection with the on-board LNA stage while elements on the integrated amplifying path can be realised using BiCMOS technology based on SiGe. This may further enhance the cost effectiveness of the proposed solution.
In accordance with embodiments of the present invention, there are two main possible approaches for defining the integrated circuit or LNA module:
According to a first approach, the integrated circuit may be designed as a mixed signal or mixed-mode application specific integrated circuit (ASIC) including—on each amplifying path—a variable gain amplifier with high linearity and reasonable noise figure as well as the digital processing unit and the temperature sensor (“all-in-one” approach). This architecture may require an extemal memory unit, e.g., an extemal flash memory, to store the data and application program dedicated to the application standard being used. As already stated above, due to the noise figure constraints on LNA inputs, embodiments using this approach may include an external LNA stage.
In accordance with the second approach, embodiments of the integrated circuit in accordance with the present invention take on the form of a multi-chip design including at least one dedicated (packaged) RF chip for providing the LNA function in connection with a digital processing unit (CPU) and a temperature sensor. In a further embodiment based on this approach, the RF chip or die as well as dies for the digital processing unit and the temperature sensor may be combined in a small ceramic to realise a single multi-chip module (MCM) for easy integration.
In accordance with the general concept underlying the present invention, in both approaches the proposed integrated circuit or module canbe used to design either a GSM or a DCS or a PCS or a UMTS equipment without any architectural changes. As will be appreciated by a person skilled in the art, the present invention is by no means limited to the abovementioned standards.A corresponding amplifying path selection and execution of application programs will be operated by means of the digital processing unit.
In this way, the present invention achieves a reduced part count in connection with improved system compactness and presents a building block that can be used with multiple frequency standards. This leads to a greatly reduced development schedule resulting in a significant reduction of product costs.
Further advantages and characteristics of the present invention can be gathered from the following description of preferred embodiments given by way of example only with reference to the enclosed drawings. Features mentioned above as well as below can be used in accordance with the present invention either individually or in conjunction. The following description is not to be regarded as an exhaustive enumeration but rather as examples with respect to a general concept underlying the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of an antenna network circuit in accordance with the present invention comprising an embodiment of the integrated circuit according to the present invention;
FIG. 2 is a schematic diagram of an embodiment of a radio frequency path in the integrated circuit in accordance with the present invention;
FIG. 3 is a schematic diagram providing an architecture overview of another embodiment of the antenna network circuit and integrated circuit in accordance with the present invention;
FIG. 4 is a more detailed schematic diagram of the antenna network circuit and integrated circuit of FIG. 3;