Pulse or digital communications – Receivers – Automatic gain control
Reexamination Certificate
2000-05-26
2002-12-24
Corrielus, Jean (Department: 2631)
Pulse or digital communications
Receivers
Automatic gain control
C375S316000, C341S143000
Reexamination Certificate
active
06498819
ABSTRACT:
TECHNICAL FIELD
This invention relates in general to radio receivers and more particularly to integrated digital radio receiver subsystems.
BACKGROUND
It is well known in the art that a dual conversion radio receiver converts incoming radio frequency (RF) signals using a common heterodyning process with two mixers. The RF signal is most often detected, converted and amplified into an audible format using some type of transducer such as a speaker. As seen in prior art
FIG. 1
, a known integrated radio receiver back-end or second intermediate frequency stage
10
will include an IF signal input
11
that is amplified by preamp
13
and then fed to a mixer
15
where it is mixed with a signal from a local oscillator synthesizer
17
controlled by a clock synthesizer
19
. The resultant second IF signal is then processed by a bandpass sigma-delta (&Sgr;-&Dgr;) converter
21
where it is noise shaped and converted into a digital format. Undesired out of band components of the converter signal can then be filtered using a discrete time filter
23
. Thereafter, it is further processed and mixed to baseband using a frequency translator
25
. Undesired components of this resultant signal are filtered using another discrete time filter
29
whose output is fed to the parallel to serial data converter
33
and the output
35
. In order to limit the input signal to the &Sgr;-&Dgr; converter
21
, an automatic gain control (AGC) circuit is employed to keep the &Sgr;-&Dgr; converter out of “clip” and reduce signal distortion.
Thus, as can be readily seen from
FIG. 1
, the radio receivers of today have greatly increased in complexity where they are not only highly integrated but also convert analog signals into a digital format where they can be manipulated and/or digitally processed for use as either audible information or data.
One problem typically associated of such high level integration of digital radio receiver has been to provide the back-end i.e. the second intermediate frequency (IF) components in addition to the digital mode sigma-delta converter in one integrated package. Specific obstacles such as analog or lumped filters (such as inductor-capacitor (LC) filters or ceramic resonators), have made such integrated circuits difficult to use and implement. Thus, the need exists to provide a highly integrated digital/analog RF receiver back-end which incorporates integrated filtering and a smart gain control that is easy to use with other receiver systems and offers superior performance characteristics.
REFERENCES:
patent: 5345409 (1994-09-01), McGrath et al.
patent: 5442353 (1995-08-01), Jackson
patent: 5541600 (1996-07-01), Blumenkrantz et al.
patent: 5621345 (1997-04-01), Lee et al.
patent: 5689440 (1997-11-01), Leitch et al.
patent: 5787125 (1998-07-01), Mittel
patent: 6151354 (2000-11-01), Abbey
Corrielus Jean
Motorola Inc.
Scutch, III Frank M.
LandOfFree
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