Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
1999-05-18
2001-03-27
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S368000, C342S377000
Reexamination Certificate
active
06208294
ABSTRACT:
BACKGROUD OF THE INVENTION
Field of the Invention
The present invention relates to an array antenna receiving device, and in particular to an array antenna receiving device such as a multibeam antenna or, an adaptive array antenna receiving device in which a plurality of antenna elements arrayed in parallel in a radio base station of a cellular mobile communication system and received signals are converted into digital signals, which are provided with a predetermined amplitude and phase rotation by operations to form a desirable composite beam pattern.
The applications of the multi-beam antenna or the adaptive array antenna receiving device which use digital signal processing in the radio base station of the cellular mobile communication system enable an enhanced gain followed by the beam pattern being equivalently focused. Further, these applications also increase the number of users accommodated in a single cell or sector followed by the reduction of interferences within a communication area due to the directivity.
However, the realization of the array antenna receiving device with signal processing in a digital domain requires a nonlinear device such as a low noise amplifier (LNA) and mixers for a frequency conversion. These devices are required for the receivers respectively which convert the received signals at the antenna elements into base band signals. This may cause a phase deviation between the receivers, which could prevent an efficient beam to be formed and incur characteristic deterioration.
Furthermore, since each of the receivers has a phase difference with respect to one another, which is determined by the arrival direction of a user signal in a communication area (cell or sector) to which the antenna element and the array of antenna elements are directed at, it is necessary to correct or compensate only the phase deviation while maintaining the phase difference information between the receivers, which is required for the composite or synthetic process of the received signals at the antenna elements.
For the phase correction performed during beam forming in a prior art array antenna receiving device, a method such as performing a calibration between the receivers periodically, e.g. once a day, is required. However, this method is no more than beam forming in an indefinite phase condition upon the occurrence of a dynamic phase deviation, which leads to low reliability of the device.
On the other hand, there is a view that the array antenna receiving device adopting an adaptive processing method does not have a substantial phase deviation between the receivers, if any, since the amplitude and phase including the phase deviation are controlled. However, a slow convergence rate in the adaptive processing, and a separation of the phase deviation from the amount of the amplitude and phase control in the adaptive processing is required for transmission beam forming for the amount of the reception time controlled upon transmission.
Further, an array antenna receiving device as shown in
FIG. 22
has also been proposed, in which assuming that the number of array antenna elements in a single sector be “n”. Thus, radio frequency signals from antenna elements
1
l
-
1
n
are provided at an analog beam former
2
with a certain (fixed) amplitude and phase rotation to form a desirable antenna pattern. RF signals received by such beams are converted into base band signals and then converted into digital signals by receivers
3
l
-
3
n.
The outputs of the receivers
3
l
-
3
n
are then selectively switched by a selector
9
to select the largest beam output in power, thereby avoiding phase deviation between the receivers.
However, the prior art array antenna receiving device shown in
FIG. 22
does not perform adaptive beam forming in the digital domain at a latter stage of the device (not shown) so that further characteristic improvements are not obtained. Therefore, without any phase correction by some means, an array antenna receiving device with higher reliability and better performance is not realized, resulting in a problem that an adaptive array antenna or the like is not applicable to a radio base station.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide an array antenna receiving device that compensates a phase deviation to enable efficient beam forming while maintaining phase difference information between receivers using the arrival direction of a user signal in a communication area to which an antenna element and the array of antenna elements in a radio base station is directed.
These and other objects are made by an array antenna receiving device according to the present invention arranged such that an analog beam former makes a composite beam so that a phase difference between adjacent beams have a fixed value determined by the beams selected. Further, a phase compensator provides digital signals from receivers with phase correction quantities based on any one of the digital signals so that phase differences between the antenna elements have the fixed value. Namely, it is arranged so that a phase deviation of an active circuit portion (receiver) is compensated by using inter-antenna branch phase information of a passive circuit portion such as antenna or analog beam former without any phase deviation. Thus, it becomes possible to perform beam forming, which is higher in adaptive processing reliability and efficiency due to the signals produced after the phase compensation. This contributes to a realization of a multi-beam antenna, or an adaptive array antenna receiving device in the digital domain.
Also, the beam former may comprise power distribution circuits and phase shifters.
Furthermore, the array antenna receiving device according to the present invention also maintains a generator for generating an uplink pilot signal forming a reference for any direction in a communication area. In this case, the phase compensator converts the uplink signal into the digital signals provided with the phase correction quantities.
Alternatively, the array antenna receiving device according to the present invention also may include a generator for generating an uplink pilot signal to distribute output signals of the generator to receiving routes. In this case, the phase compensator uses the uplink signal as receiving signals between the antenna elements and the beam former with the fixed phase difference to generate the digital signals provided with the phase correction quantities.
The array antenna receiving device according to the present invention may also include an inverter circuit that performs an operation inverse to the beam former so that output signals of the phase compensator may be equivalent to the receiving signals per a single antenna element; and an adaptive processing portion that combines output signals of the inverter circuit to form the adaptive antenna pattern.
REFERENCES:
patent: 3646558 (1972-02-01), Campanella
patent: 4882589 (1989-11-01), Reisenfeld
patent: 5767806 (1998-06-01), Watanabe et al.
patent: 5933112 (1999-08-01), Hiramatsu et al.
patent: 5999120 (1999-12-01), Yamada
patent: 8330837 (1996-12-01), None
patent: 9162799 (1997-06-01), None
Kobayakawa Shuji
Tanaka Yoshinori
Tsutsui Masafumi
Fujitsu Limited
Gregory Bernarr E.
Helfgott & Karas, P C.
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