Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
1999-03-23
2001-11-13
Vo, Nguyen T. (Department: 2682)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S127500, C455S103000
Reexamination Certificate
active
06317610
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method of combining several signals, the method being used at base stations of a radio network, carrier waves and signals being generated at the base station, the signals being used for modulating the generated carrier waves, the base station comprising an antenna for transmitting the modulated signals to a carrier wave.
The invention further relates to a base station used for combining several signals in a radio network, the base station comprising an antenna, modulating means for generating and modulating carrier waves, and transmitters for generating signals for modulating the generated carrier waves, the signals being transmitted modulated to a carrier wave using the antenna.
2. Description of the Related Art
In cellular radio systems, such as GSM/DCS systems, the base station antenna transmits several signals generated by base station transmitters. The signals modulate the carrier wave and the carrier waves are transmitted to the radio path using a radio channel. There are various methods of transmitting signals generated by transmitters to the radio path using only one antenna. It is common to use different combiners for combining several transmitters with the same antenna at the base station.
Very often a transmitting and a receiving antenna do not have a clear line of sight; instead, there are obstacles in the line of sight caused by terrain or buildings. Thus the signal perceived in the receiver is the sum of signals propagated on several routes reflected off the obstacles, and are of different phases. The sum of several signals of different phases follows the Rayleigh distribution, when the phases are randomly distributed. The fading of the signal also depends on the frequency of the signal. The frequency selective fading of a signal is one of the reasons why the frequency hopping technique is used in digital cellular radio networks. Frequency hopping means that the transmission frequency used o n a connection is changed at regular intervals. Due to frequency hopping, the transfer quality of a signal can be improved, especially in cases in which a subscriber terminal moves very slowly or is stationary, which is often the case when e.g. a mobile phone is used. In addition to the frequency diversity brought about by frequency hopping, the technique is useful in scattering the interference caused by a radio connection over several frequencies such that the momentary interference at a particular frequency remains small.
In order to achieve an advantage from frequency hopping in the digital GSM and DCS systems, more than four frequencies should be used. Currently narrowband transmitter combiners are commonly used at base stations. The narrowband combiners, whose function is to combine several transmitters with one antenna, restrict the number of frequencies used in frequency hopping to the number of actual transceiver units and combiner filters. Thus for example, a base station using three transceiver units and three combiner filters enables the use of three frequencies in frequency hopping.
Narrowband transmitter combiners are large and complex components because they have to able to be tuned. Wideband combiners have also been developed that do not require tuning such as a narrowband transmitter. Wideband combiners, together with frequency hopping synthesizers, do not restrict the number of frequencies used. A problem with wideband combiners is, however, that combiner attenuations become extremely large compared with narrowband combiners, when more than two transmitters are combined with the same wideband combiner. Hence, it has not been possible to use wideband combiners at base stations, from which a large traffic capacity is required, but narrowband combiners have had to be used. The implementation of frequency hopping at these base stations has thus been inadequate.
Alternatively, it has also been possible to combine the modulated carrier waves before the final amplification of the signal. A linear amplifier in particular has been used as the amplifier. A disadvantage of the linear amplifier has, however, been its difficult technical implementation, as the linearity requirements of the amplifier have been high. Furthermore, the performance of linear amplifiers has been poor.
BRIEF SUMMARY OF THE INVENTION
A method and apparatus are provided to allow several transmitters to be combined into the same antenna in such a manner as to permit easy implementation of frequency hopping. Further the present invention provides for the implementation of a base station, in which an amplifier that is easy to implement is used to amplify the carrier wave.
The method comprises two or more signals that are modulated to their own carrier wave, and then the carrier waves modulated by the signals are amplified. The carrier waves modulated by the signals are passively combined after amplification to the same antenna.
The base station of the present invention comprises the means for amplifying the carrier waves modulated by the signals, and means for passively combining the carrier waves modulated by the signals after amplification to the same antenna wherein the modulating means modulate two or more signals to their own carrier waves.
An advantage achieved with the method of the present invention is that the carrier wave is modulated by two different signals and several carrier waves are combined in such a manner that the carrier waves can be transmitted using one antenna. The method preferably uses a DDS modulating method, in which, e.g. two modulating signals can be easily implemented. Furthermore, the carrier waves are amplified with an amplifier, whose linearity requirements are easy to implement. In addition, the carrier waves are combined to one antenna in wideband to enable the use of frequency hopping.
The preferred embodiments of the method of the invention are also disclosed in the enclosed dependent claims and the preferred embodiments of the base station of the invention are disclosed in the enclosed dependent claims.
REFERENCES:
patent: 4941200 (1990-07-01), Leslie et al.
patent: 5163181 (1992-11-01), Koontz
patent: 5214787 (1993-05-01), Karkota et al.
patent: 5559788 (1996-09-01), Zscheile, Jr. et al.
patent: 502811 (1996-01-01), None
patent: 0622910 (1994-11-01), None
patent: 0681374 (1995-11-01), None
patent: 60-150344 (1985-08-01), None
patent: WO 96/13917 (1996-05-01), None
J. Carter, “Communications repeaters”, Chapter 14, Satellite Communication SystemS, 1987, pp. 230-250.
Extend-A-Cell IV Technical Manual, vol. 3, 1993, Technical Information, pp. 1-1 -3-11.
Nokia Telecommunications Oy
Pillsbury & Winthrop LLP
Vo Nguyen T.
LandOfFree
Method of combining several signals, and base station does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of combining several signals, and base station, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of combining several signals, and base station will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581746