Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
1999-02-23
2001-11-06
Chin, Stephen (Department: 2634)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S148000, C375S267000, C375S347000, C375S349000, C455S137000
Reexamination Certificate
active
06314127
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a system and method for enhancing signal reception.
BACKGROUND OF THE INVENTION
Current practices for measuring signal parameters of a received electromagnetic signal involve using multiple synchronized receivers. Signal parameters include relative amplitude and correlation between received signals. A received signal may be distributed among multiple signal branches of a measuring system. A signal branch refers to a path for the distribution of one or more received electromagnetic signals. The path of the signal branch may include a transmission media (e.g., coaxial cable) or may be integrated into a circuit board (e.g., microstrip). For each signal branch, a separate receiver typically is required to measure the signal parameters associated with a corresponding signal branch. The requirement for multiple receivers tends to increase the size, weight, and cost of the conventional measuring system.
To obtain accurate correlation measurements between signal branches, all receivers are synchronized using a highly stable external oscillator (e.g., stability better than 10 parts per million of the oscillator frequency). All receivers are calibrated for amplitude variations from unit to unit to reduce errors in the relative amplitude measurements. However, the synchronization and amplitude calibrations are time-consuming and subject to human error. Moreover, each receiver may experience relative amplitude drift due to differences in temperature from receiver to receiver. Thus, a need exists for an improved measuring system which eliminates or expedites the calibration process, including its temporal and amplitudinal aspects.
The reception of received electromagnetic signals may sometimes be improved through the use of diversity antennas. Yet, the full benefit of diversity gain is often lost because the receiving system lacks the necessary sophistication to accurately decide whether or not to combine signals from different diversity branches of the diversity antenna. Thus, a need exists for a measuring system that may be incorporated into a receiving system to enhance reception of received electromagnetic signals through an accurate analysis of signal parameters.
SUMMARY OF THE INVENTION
In accordance with the invention, a system for enhancing signal reception comprises delay devices coupled to a combiner. The delay devices are adapted to delay respective input signals by corresponding offset delay durations to produce time-staggered delayed signals with respect to one another. The combiner is coupled to the delay devices for combining the delayed signals to form a combined signal. A recorder receives the combined signal and records the combined signal in the time-domain. The recorder records the combined signal in successive measurement cycles. Each successive measurement cycle contains a time window corresponding to each of the delayed signals. An evaluator evaluates the recorded signal for determining average power, within each time window, over a group of the successive measurement cycles for each of the delayed signals. The evaluation of the evaluator prepares for determining cross-correlation between pairs of the delayed signals.
In one aspect of the invention, only one time-domain recorder, as opposed to multiple receivers, is required to receive and record input signals from multiple signal branches. Measuring signal parameters is expedited because only one recorder needs to be calibrated regardless of the number of signal branches. The measuring method of the invention is not affected by thermal drift caused by temperature variations among receivers associated with each branch, because only one recorder is required. The reduction in the number of receivers required offers the opportunity to reduce power consumption and cost of the measuring system, while improving the accuracy of measurements of signal parameters.
In another aspect of the invention, a measuring system may be incorporated into a receiving system to enhance the reception of transmitted electromagnetic signals. The reception of transmitted electromagnetic signals is enhanced by improving the accuracy of measurements involving correlation and relative power among multiple signal branches. The receiving system is capable of selecting the best combination of the signal branches as a received signal based upon a mathematical function of the measured correlation and the measured relative power. Therefore, if diversity antennas are used, improvements ranging from approximately 3 dB to 6 dB or more in received signal strength are possible, along with potential reduction of deep fades of the received signal.
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Lynch Michael A.
Triolo Anthony A.
Chin Stephen
Ha Dac V.
Lucent Technologies - Inc.
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