Telecommunications – Receiver or analog modulated signal frequency converter – With wave collector
Reexamination Certificate
1999-01-13
2001-02-13
Maung, Nay (Department: 2744)
Telecommunications
Receiver or analog modulated signal frequency converter
With wave collector
C455S277200, C455S562100
Reexamination Certificate
active
06188879
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the diversity reception of a transmitted signal using an array of antennas, and more specifically to the performance assessment of an array of antennas in a switched space diversity receiving system.
3. Description of the Related Art
Diversity combining is used in a space-diversity technique for combining signals received via independent propagation paths in such a way that a high signal to noise ratio is achieved. This technique is suitable for applications where a deep fade occurs in the propagation paths. However, if the fading pattern of a propagation path is obscure such as the one that occurs frequently during a cellular mobile communication, diversity combining technique is not suitable. In such instances, a switched space diversity technique is employed for selecting the highest of the received signals.
A fault detection technique for an array of antennas is disclosed in Japanese Laid-Open Patent Specification Hei-9-83418. According to this prior art, signals from an array of antennas are monitored to determine their strength values and the highest value is selected as a reference. Differences between the strength value of the antennas and the reference are determined respectively for the antennas and then compared with a threshold. Counters are associated respectively with the antennas. If one of the difference values exceeds the threshold, the counter associated with that difference value is incremented. This counter is reset to zero whenever that difference value is lower than the threshold. If the counter has been incremented to a value exceeding some critical value, an alarm indication is given that the antenna associated with this counter is not functioning properly.
However, the detection of performance degradation of a whole array of antennas, rather than with individual antennas, is also important. Although detecting electromagnetic reflections from the antennas or subjecting them to switching between a d.c. short-circuit and an open- circuit condition would be one solution, the hardware installation cost cannot economically be justified.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a switched space diversity receiver capable of determining performance degradation of a whole antenna array as well as faulty individual antennas without hardware installation.
According to a first aspect of the present invention, there is provided a diversity receiving system comprising an array of antenna systems for receiving modulated radio-frequency signals via a plurality of independent propagation paths and respectively recovering information signals from the modulated signals, a plurality of detectors connected respectively to the antenna systems for producing strength data indicating respective strengths of the information signals, a diversity switch, and call processing circuitry connected to the diversity switch for establishing a connection from a transmit site. A diversity controller is provided for selecting a highest strength signal from the information signals and controlling the diversity switch to supply the selected information signal to the call processing circuitry. Further provided is a memory having a plurality of locations respectively mapped to the antennas. The diversity controller is responsive to each connection established by the call processing circuitry for storing the strength data of the selected signal in a corresponding one of the memory locations. The diversity controller analyzes the contents of the memory locations when a predetermined number of strength data are stored, and generates an alarm indication of the whole array of antenna systems if none of the strength data exceeds a threshold value. If at least one strength data exceeds the threshold value, the memory locations are tested to see if there is at least one vacant location which contains no strength data. If such a vacant location is detected, an alarm indication is given of the antenna that is mapped to the vacant location.
According to a second aspect of the present invention, the diversity controller is arranged to compare all strength data stored in the memory locations with a threshold value when the predetermined number of strength data are stored in the memory, generate an alarm indication of the whole array of antenna systems if none of the strength data exceeds the threshold value, count strength data stored in each memory location to produce a plurality of respective counts for the memory locations if at least one strength data exceeds the threshold value, determines a difference between a maximum and a minimum value of the counts. If the difference is greater than a predetermined value, an alarm indication is given of the antenna that is mapped to the memory location of the minimum count value.
According to a third aspect, the present invention provides a diversity reception method comprising the steps of (a) receiving modulated radio-frequency signals via independent propagation paths using an array of antennas and respectively recovering information signals from the modulated signals, (b) producing strength data indicating respective strengths of the information signals, (c) selecting a highest strength signal from the information signals and allowing a connection to be established from a transmit site using the selected signal, (d) storing the strength data of the selected signal in a corresponding one of a plurality of locations of a memory, the locations being respectively mapped to the antennas, (e) repeating the steps (a) to (d) a predetermined number of times, (f) analyzing strength data stored in the memory locations, (g) if none of the strength data exceeds a threshold value, generating an alarm indication of the whole array of antennas, and (h) if there is at least one vacant memory location which contains no strength data, generating an alarm indication of the antenna mapped to the vacant location.
According to a fourth aspect, the present invention provides a diversity reception method comprising the steps of (a) receiving modulated radio-frequency signals via a plurality of independent propagation paths using an array of antennas and respectively recovering information signals from the modulated signals, (b) producing strength data indicating respective strengths of the information signals, (c) selecting a highest strength signal from the information signals and allowing a connection to be established from a transmit site using the selected signal, (d) storing the strength data of the selected signal in a corresponding one of a plurality of ii locations of a memory, the locations being respectively mapped to the antennas, (e) repeating the steps (a) to (d) a predetermined number of times, (f) comparing all strength data of the memory with a threshold value, (g) generating an alarm indication of the whole array of antennas if none of the strength data exceeds the threshold value, (h) counting strength data stored in each of the memory locations to produce a plurality of respective counts for the locations of the memory if at least one strength data exceeds the threshold value, (i) determining a difference between a maximum and a minimum value of the counts, and (j) generating an alarm indication of the antenna mapped to the memory location of the minimum count value if the difference is greater than the predetermined value.
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Maung Nay
NEC Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Trinh Sonny
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