Coded data generation or conversion – Analog to or from digital conversion – Analog to digital conversion
Reexamination Certificate
2002-08-20
2004-07-27
Tohar, Michael (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Analog to digital conversion
C375S141000
Reexamination Certificate
active
06768441
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the field of communications and more particularly to methods of receiving communications signals and related receivers.
In a conventional receiver, an analog-to-digital converter (ADC) may be used to convert a received analog radio signal into a digital signal for further digital signal processing. An analog-to-digital converter, however, may operate in a limited dynamic range, and if an amplitude of the analog signal exceeds this dynamic range, the resulting digital signal may be distorted. Reception of the radio signal may thus be degraded if the amplitude of the analog signal exceeds the dynamic range of the analog-to-digital converter. In addition, reception of the radio signal may be degraded if the amplitude of the analog radio signal is not a significant portion of the dynamic range such as when the analog radio signal is relatively weak. Accordingly, a receiver should be designed such that a significant portion of the dynamic range of the analog-to-digital converter is used without exceeding the dynamic range of the analog-to-digital converter.
Automatic gain control (AGC) has thus been used to maintain the amplitude of the received analog radio signal within the dynamic range of the analog-to-digital converter. In other words, one or more attenuators and/or amplifiers can be used in an automatic gain control circuit to adjust an amplitude of a received analog radio signal before performing analog-to-digital conversion. The attenuators and/or amplifiers of the automatic gain control circuit can be switched on/off depending on the strength of the received analog radio signal. The signal strength of the received analog radio signal used to provide automatic gain control can be measured in the analog domain of the receiver before analog-to-digital conversion or in the digital domain of the receiver after analog-to-digital conversion.
SUMMARY OF THE INVENTION
According to embodiments of the present invention, methods of receiving communications signals can include generating a received analog signal including energy corresponding to communications transmitted from a remote transmitter, and performing an analog-to-digital conversion of the received analog signal to provide a received digital signal. The received digital signal can be digitally filtered using a first digital filter having a first bandwidth to provide a first filtered digital signal, and the first filtered digital signal can be processed to provide an estimate of the communications transmitted from the remote transmitter. The received digital signal can be digitally filtered using a second digital filter having a second bandwidth to provide a second filtered digital signal wherein the second bandwidth is greater than the first bandwidth, and a signal characteristic of the second filtered digital signal can be measured.
According to additional embodiments of the present invention, the measured signal characteristic can be a received signal strength. Moreover, the measured signal characteristic can be used to adjust a gain of the received analog signal, to adjust the first bandwidth of the first digital filter, to adjust operation of a digital signal processor, and/or to adjust operation of a whitening filter. In addition, each of the first and second digital filters can be selected from the group including a finite impulse response filter, an infinite impulse response filter, a cascaded integrator-comb filter, and/or a realization filter.
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Singvall Jakob
Stenstrom Niklas
Myers Bigel & Sibley & Sajovec
Nguyen Linh V
Telefonaktiebolaget L.M. Ericsson
Tohar Michael
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