Telecommunications – Receiver or analog modulated signal frequency converter – Plural receivers
Reexamination Certificate
1997-09-25
2001-02-27
Trost, William G. (Department: 2744)
Telecommunications
Receiver or analog modulated signal frequency converter
Plural receivers
C455S043000, C370S482000, C370S517000, C375S349000
Reexamination Certificate
active
06195537
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electronic signal processing in general, and, more particularly, to a technique for selectively suppressing carrier signals in a multi-carrier signal.
BACKGROUND OF THE INVENTION
FIG. 1
depicts wideband digital radio receiver
100
in the prior art, which may also be known as a “block” or “software” radio. Wideband digital radio receivers are increasingly common and are characterized by the fact that they digitize an incoming multi-carrier signal and separate the carrier signals digitally, in contrast to more conventional receivers that separate the carrier signals using analog bandpass filters and then digitize each carrier signal individually.
Wideband digital radio receiver
100
typically comprises antenna
101
, RF front end
103
, analog-to-digital converter
105
and channelizer
107
. Antenna
101
receives a multi-carrier RF signal and converts it into an electrical signal for RF front end
103
, in well-known fashion. RF front end
103
amplifies the multi-carrier signal, typically using a low-noise amplifier, and downconverts the multi-carrier signal to either baseband or a suitable intermediate frequency, also in well-known fashion. Analog-to-digital converter
105
digitizes the multi-carrier signal, in well-known fashion, and channelizer
107
isolates and demodulates each carrier signal of interest using digital signal processing techniques, in well-known fashion.
FIG. 2
depicts a graph of the signal strength for each of twelve frequency-disparate carrier signals in an illustrative multi-carrier signal. When the signal strength of one or more of the carrier signals is great, the danger arises that the strong carrier signals could saturate analog-to-digital converter
105
. Because analog-to-digital converter
105
has a non-linear frequency response, the potential exists that intermodulation products or “intermods” could be introduced into the digitized multi-carrier signal. Intermodulation products are clearly disadvantageous because they can attenuate or distort other carrier signals in the digitized multi-carrier signal.
Therefore, the need exists for a technique that prevents strong signals in a multi-carrier signal from saturating a device with a non-linear frequency response.
SUMMARY OF THE INVENTION
Some embodiments of the present invention are capable of preventing strong signals in a multi-carrier signal from saturating a device with a non-linear frequency response. In the context of block radio design, some embodiments of the present invention identify and selectively attenuate any carrier signal in a multi-carrier signal that could saturate the analog-to-digital converter before the multi-carrier signal is digitized by the analog-to-digital converter. Furthermore, some embodiments of the present invention attenuate the stronger carrier signals in the multi-carrier signal without affecting the weaker carrier signals.
These results are obtained in an illustrative embodiment of the present invention that comprises: a signal replicator for creating two analog representations of an incoming multi-carrier signal, a scanner that identifies the potentially problematic carrier signals in the multi-carrier signal, a resynthesizer that regenerates the potentially problematic carrier signals, and a signal combiner that subtracts the regenerated carrier signals from the original multi-carrier signal, thus creating a multi-carrier signal in which the potentially problematic carrier signals are attenuated and the weaker carrier signals are left unaffected.
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patent: 5321847 (1994-06-01), Johnson, Jr.
patent: 5510743 (1996-04-01), Shi
patent: 5564095 (1996-10-01), Arnstein et al.
patent: 5678213 (1997-10-01), Myer
patent: 5678218 (1997-10-01), Daikoku
patent: 5694395 (1997-12-01), Myer et al.
patent: 5694396 (1997-12-01), Firouzbakht et al.
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Allpress Stephen Alan
Pagano Carmine James
Tarallo Joseph Anthony
Breyer Wayne S.
Craver Charles
DeMont Jason Paul
DeMont & Breyer LLC
Lucent Technologies - Inc.
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