U.S. patent application number 13/691973 was filed with the patent office on 2014-06-05 for method and apparatus for signal scanning for multimode receiver.
The applicant listed for this patent is David Haub, Zhigang Xu. Invention is credited to David Haub, Zhigang Xu.
Application Number | 20140155060 13/691973 |
Document ID | / |
Family ID | 50736554 |
Filed Date | 2014-06-05 |
United States Patent
Application |
20140155060 |
Kind Code |
A1 |
Haub; David ; et
al. |
June 5, 2014 |
METHOD AND APPARATUS FOR SIGNAL SCANNING FOR MULTIMODE RECEIVER
Abstract
In a signal processing method, an input signal is provided at an
input to a receiver. A bandwidth of the receiver is controlled to a
predetermined wideband setting. For band in a plurality of
frequency bands, the input signal is processed at the receiver with
a mixer, an amplifier, and a filter, to generate a first processed
signal, and a power spectral density of the processed signal is
generated over that frequency band, to provide a frequency domain
signal for that frequency band. Based on the frequency domain
signals corresponding to each frequency band in the plurality of
frequency bands, a frequency domain representation of the processed
signal is reconstructed over a reconstruction band having a
bandwidth larger than the predetermined wideband setting. Based on
the reconstructed frequency domain representation, a spectral
component is identified corresponding to at least one cellular
telephony access mode.
Inventors: |
Haub; David; (San Diego,
CA) ; Xu; Zhigang; (San Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Haub; David
Xu; Zhigang |
San Diego
San Diego |
CA
CA |
US
US |
|
|
Family ID: |
50736554 |
Appl. No.: |
13/691973 |
Filed: |
December 3, 2012 |
Current U.S.
Class: |
455/434 |
Current CPC
Class: |
H04W 48/16 20130101;
H04W 88/06 20130101 |
Class at
Publication: |
455/434 |
International
Class: |
H04W 48/16 20060101
H04W048/16 |
Claims
1. A method comprising: providing an input signal at an input to a
receiver; controlling a bandwidth of the receiver to a
predetermined wideband setting; for each of a plurality of
frequency bands: at the receiver, processing the input signal with
a mixer, an amplifier, and a filter, to generate a first processed
signal, and generating a power spectral density of the first
processed signal over said frequency band, to provide a frequency
domain signal for said frequency band; reconstructing, based on the
frequency domain signals corresponding to each frequency band in
the plurality of frequency bands, a frequency domain representation
of the processed signal over a reconstruction band having a
bandwidth larger than the predetermined wideband setting; and
identifying, based on the reconstructed frequency domain
representation, a spectral component corresponding to at least one
cellular telephony access mode.
2. The method of claim 1, wherein determining the power spectral
density of the first processed signal includes computing a fast
Fourier transform of the first processed signal.
3. The method of claim 1, wherein each band in the plurality of
frequency bands has a bandwidth equal to the predetermined wideband
setting.
4. The method of claim 1, wherein spectral components corresponding
to at least a first and a second cellular telephony access mode are
detected, and the first mode is different from the second mode.
5. The method of claim 4, wherein the first mode is a wideband mode
and the second mode is a narrowband mode.
6. The method of claim 5, wherein the first mode is an LTE mode and
the second mode is a GSM mode.
7. The method of claim 1, wherein the at least one cellular
telephony access mode includes a wideband mode identified by
detecting a plurality of contiguous frequency bins each
corresponding to a power higher than a predetermined threshold.
8. The method of claim 1, wherein the at least one cellular
telephony access mode includes a narrowband mode identified by
detecting a one or more power spectral density spikes, wherein each
spike corresponds to a frequency bin having a power exceeding the
power at respective neighboring bins by at least a predetermined
threshold.
9. The method of claim 1, further comprising identifying, based on
the reconstructed frequency domain representation, a carrier-free
band containing no spectral components corresponding to any
cellular telephony access modes, wherein the carrier-free band is
within the reconstruction band.
10. The method of claim 1, wherein the bands in the plurality of
frequency bands are contiguous bands.
11. The method of claim 1, further comprising: configuring the
receiver to a frequency band associated with one of the modes;
processing the input signal with the mixer, the amplifier, and the
filter after the configuring, to generate a second processed
signal; measuring power or voltage of the second processed signal;
and if the measured power or voltage exceeds a predetermined
threshold, synchronizing the receiver to a base station based on
the frequency band associated with said one mode.
12. The method of claim 1, wherein the at least one cellular
telephony access mode includes a plurality of modes, the method
further comprising: assigning a priority to each mode in the
plurality of modes; configuring the receiver to frequency bands
associated with the respective modes based on the priority of each
mode; for each mode in order of priority: processing the input
signal with the mixer, the amplifier, and the filter after the
configuring of the receiver to the corresponding frequency band, to
generate a second processed signal corresponding to said mode;
measuring power or voltage of the second processed signal; and if
the measured power or voltage exceeds a predetermined threshold,
synchronizing the receiver to a base station based on the frequency
band associated with said mode.
13. The method of claim 12, further comprising: identifying, based
on the reconstructed frequency domain representation, a
carrier-free band containing no spectral components corresponding
to any cellular telephony access modes, wherein the carrier-free
band is within the reconstruction band; assigning to said
carrier-free band a priority lower than all the priorities assigned
to the respective modes in the plurality of modes; configuring the
receiver to said carrier-free band; processing the input signal
with the mixer, the amplifier, and the filter after the configuring
of the receiver to said carrier-free band, to generate a second
processed signal corresponding to said carrier-free band; measuring
power or voltage of said second processed signal corresponding to
said carrier-free band; and if the measured power or voltage of
said second processed signal corresponding to said carrier-free
band exceeds said predetermined threshold, synchronizing the
receiver to a base station corresponding to said carrier-free
band.
14. A system comprising: a receiver including a mixer, an
amplifier, a variable bandwidth filter, and a waveform synthesizer
configured to synthesize a waveform at a variable frequency and
provide the waveform to the mixer, wherein the receiver is
configured to receive an input signal at an input, wherein the
mixer, the amplifier, and the filter are disposed along a serial
processing path and are configured to provide a processed signal
corresponding to said input signal; a power spectral density
computation module configured to generate a power spectral density
of said processed signal over a selected frequency band, to provide
a frequency domain signal for said frequency band, wherein the
selected frequency band is variable; and a state machine configured
to reconstruct, based on plural frequency domain signals provided
by said power spectral density computation module for respective
bands in a plurality of frequency bands, a frequency domain
representation of said processed signal over a reconstruction band
having a bandwidth larger than the predetermined wideband setting,
and further configured to identify, based on said frequency domain
representation, a spectral component corresponding to at least one
cellular telephony access mode.
15. The system of claim 14, further comprising a received signal
strength indication (RSSI) module configured to measure voltage or
power of said processed signal.
16. The system of claim 14, wherein the state machine is further
configured to control a bandwidth and frequency of the
receiver.
17. The system of claim 16, further comprising a received signal
strength indication (RSSI) module configured to measure voltage or
power of said processed signal after said receiver is controlled to
a bandwidth and frequency corresponding to one of the modes.
18. The system of claim 17, wherein said state machine is further
configured to synchronize the receiver to a base station based on
the frequency band associated with said one mode, if an output of
said RSSI module is indicative of a voltage or power measurement
exceeding a predetermined threshold.
19. A system comprising: a first receiver module and a second
receiver module in a multiple input multiple output (MIMO)
communications system, the first and second receiver modules
configured to process a first input signal and a second input
signal, respectively, each receiver module including a mixer, an
amplifier, and a variable bandwidth filter disposed along a serial
processing path, the first and second receiver modules configured
to provide a first processed signal corresponding to said first
input signal and a second processed signal corresponding to said
second input signal, respectively; a power spectral density
computation module configured to generate a power spectral density
of said first processed signal over a selected frequency band, to
provide a frequency domain signal for said frequency band, wherein
the selected frequency band is variable; a received signal strength
indication (RSSI) module configured to measure voltage or power of
said second processed signal; and a state machine having a first
input coupled to an output of said power spectral density
computation module and a second input coupled to an output of said
RSSI module, said state machine configured to reconstruct, based on
plural frequency domain signals provided by said power spectral
density computation module for respective bands in a plurality of
frequency bands, a frequency domain representation of said first
processed signal over a reconstruction band having a bandwidth
larger than the predetermined wideband setting, and further
configured to identify, based on said frequency domain
representation, a spectral component corresponding to at least one
cellular telephony access mode.
20. The system of claim 19, wherein the second receiver module
further comprises a waveform synthesizer configured to synthesize a
waveform at a variable frequency and provide said waveform to the
mixer of said second receiver module; wherein said state machine is
coupled to said filter of said second receiver module and to said
synthesizer of said second receiver module and is configured to
control a bandwidth and frequency of said second receiver module,
and said RSSI module is configured to measure the voltage or power
of said processed signal after said second receiver module is
controlled to a bandwidth and frequency corresponding to one of the
modes.
21. The system of claim 20, wherein said state machine is further
configured to synchronize said second receiver module to a base
station based on the frequency band associated with said one mode,
if the output of said RSSI module is indicative of a voltage or
power measurement exceeding a predetermined threshold.
Description
FIELD
[0001] The present disclosure relates to receiver architectures in
a wireless communications system, and more particularly, some
embodiments relate to methods and systems for scanning RF signals
to identify cellular telephony access technologies used for
communicating a signal wirelessly.
BACKGROUND
[0002] Wireless communications serve an increasingly important role
in the modern world. The electromagnetic spectrum used for wireless
cellular telephony is a valuable and limited resource.
Consequently, many different types of cellular telephony access
technologies (access modes) are being deployed in the available
spectrum. Various known access modes utilize various parts of the
spectrum. FIG. 1 illustrates an example multi-mode radio frequency
(RF) band in which several different technologies might be
deployed. In this example, RF band 100 contains spectral components
102, 104, 106, and 108 corresponding to the wide band LTE standard,
the GSM standard, the narrow band LTE standard, and the time
division synchronous code division multiple access (TD-SCDMA)
standard, respectively. Other scenarios can also exist where the
wideband code division multiple access (W-CDMA) and CDMA2000 1X
standards are deployed.
[0003] Some conventional techniques that employ received signal
strength indication (RSSI) measurements for signal scanning require
all possible channels to be scanned, which can increase the time
spent scanning for or synchronizing to candidate base stations.
When multiple modes are deployed in RF band 100 as shown in FIG. 1,
initial acquisition could be slow because each possible access mode
needs to be scanned for the RF band 100. Conventional scanning
techniques do not provide any indication of what type of access
mode may be present in any particular frequency region. Even if it
is known that a particular access mode is only deployed in a
portion of the band, that entire portion would still need to be
scanned to look for usable base stations. As a result of such
issues, performance inefficiencies (e.g., decreased speed,
increased power consumption) and/or increased cost are frequently
encountered in conventional approaches.
SUMMARY
[0004] In some embodiments of the present disclosure, an input
signal (e.g., signal 202) is provided (block 710) at an input to a
receiver (e.g., receiver 200). A bandwidth of the receiver is
controlled (block 720) to a predetermined wideband setting (e.g.,
20 MHz as for each of WB1, WB2, WB3 in FIG. 3). For each of a
plurality of frequency bands (e.g., WB1, WB2, WB3), blocks 730 and
740 are performed. At the receiver, the input signal is processed
(block 730) with a mixer, an amplifier, and a filter, to generate a
processed signal (e.g. signal 248a or signal 248b, or
alternatively, signals 248a and 248b may together be considered the
processed signal). A Fourier transform (e.g., FFT) of the processed
signal is generated (block 740) over the particular frequency band,
to provide a frequency domain signal for that frequency band. Based
on the frequency domain signals corresponding to each frequency
band in the plurality of frequency bands, a frequency domain
representation of the processed signal is reconstructed (block 750)
over a reconstruction band (e.g., band including regions 501, 502,
503, 504 of FIG. 5) having a bandwidth larger than the
predetermined wideband setting. Based on the reconstructed
frequency domain representation, a spectral component corresponding
to at least one cellular telephony access mode is identified (block
760).
[0005] In some embodiments, a system includes a receiver, a power
spectral density computation module, and a state machine. The
receiver includes a mixer, an amplifier, a variable bandwidth
filter, and a waveform synthesizer configured to synthesize a
waveform at a variable frequency and provide the waveform to the
mixer. The receiver is configured to receive an input signal at an
input. The mixer, the amplifier, and the filter are disposed along
a serial processing path and are configured to provide a processed
signal corresponding to the input signal. The power spectral
density computation module is configured to generate a Fourier
transform of the processed signal over a selected frequency band,
to provide a frequency domain signal for said frequency band. The
selected frequency band is variable. The state machine is
configured to reconstruct, based on plural frequency domain signals
provided by the power spectral density computation module for
respective bands in a plurality of frequency bands, a frequency
domain representation of the processed signal over a reconstruction
band having a bandwidth larger than the predetermined wideband
setting, and is further configured to identify, based on the
frequency domain representation, a spectral component corresponding
to at least one cellular telephony access mode.
[0006] In some embodiments, a system includes a first receiver
module and a second receiver module in a MIMO communications
system, a power spectral density computation module, a received
signal strength indication (RSSI) module, and a state machine. The
first and second receiver modules are configured to process a first
input signal and a second input signal, respectively. Each receiver
module includes a mixer, an amplifier, and a variable bandwidth
filter disposed along a serial processing path. The first and
second receiver modules are configured to provide a first processed
signal corresponding to said first input signal and a second
processed signal corresponding to said second input signal,
respectively. The power spectral density computation module is
configured to generate a Fourier transform of said first processed
signal over a selected frequency band, to provide a frequency
domain signal for said frequency band. The selected frequency band
is variable. The received signal strength indication (RSSI) module
is configured to measure voltage or power of the second processed
signal. The state machine has a first input coupled to an output of
the power spectral density computation module and a second input
coupled to an output of the RSSI module. The state machine is
configured to reconstruct, based on frequency domain signals
provided by the power spectral density computation module for
respective bands in a plurality of frequency bands, a frequency
domain representation of the first processed signal over a
reconstruction band having a bandwidth larger than the
predetermined wideband setting, and is further configured to
identify, based on the frequency domain representation, a spectral
component corresponding to at least one cellular telephony access
mode.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The following will be apparent from elements of the figures,
which are provided for illustrative purposes and are not
necessarily to scale.
[0008] FIG. 1 is an illustration of an RF band with multiple
deployed cellular telephony access modes.
[0009] FIG. 2 is a receiver architecture diagram in accordance with
some embodiments of the present disclosure.
[0010] FIG. 3 is an illustration of example wideband scans in
accordance with some embodiments.
[0011] FIGS. 4A-4C are plots of example FFT results from wideband
scans in accordance with some embodiments.
[0012] FIG. 5 is a plot showing reconstructed band power spectral
density (PSD) in accordance with some embodiments.
[0013] FIG. 6 is a flow diagram of a process in accordance with
some embodiments.
[0014] FIG. 7 is a flow diagram of another process in accordance
with some embodiments.
[0015] FIG. 8 is an architecture diagram of a multiple
input/multiple output (MIMO) receiver in accordance with some
embodiments.
DETAILED DESCRIPTION
[0016] This description of the exemplary embodiments is intended to
be read in connection with the accompanying drawings, which are to
be considered part of the entire written description.
[0017] Various embodiments of the present disclosure provide
techniques for improving the time required to perform scans of RF
signals for identification of usable base stations, thereby
promoting faster synchronization to the relevant cellular telephony
access mode (access technology). Also, embodiments provide the
ability to skip scans or to change the priority of scans for
particular access technologies in particular frequency regions in
order to speed up the acquisition process.
[0018] FIG. 2 is a receiver architecture diagram in accordance with
some embodiments of the present disclosure. A receiver 200 includes
components configured to process an input signal 202 that is
received, e.g., from an antenna. The input signal is shown in
differential form (RF_RX+ and RF_RX-); other signals in FIG. 2 may
be in differential form but are not labeled as such, for visual
clarity and to reduce clutter. The input signal is amplified by a
low noise amplifier (LNA) 204 to provide an amplified input signal
214. A local oscillator 210 generates one or more oscillator
signals 212 (e.g., sinusoids) based on control signals 208 from a
synthesizer 206. With the synthesizer and with variable bandwidth
filter(s) as described below, receiver 200 is tunable to receive a
signal at a desired frequency.
[0019] A mixer 216 mixes the amplified input signal 214 with the
oscillator signal 212. The mixer may include 216a and 216b, one of
which may process an in-phase component and one of which may
process a quadrature component. Separate processing pathways are
shown in FIG. 2 for the in-phase and quadrature components (with
similar reference characters but different suffixes, "a" or "b"),
but the processing is similar for each, so the discussion below
focuses on the top pathway in FIG. 2, which may be an in-phase or
quadrature path. It is to be understood that the various feedback
effects from state machine 254 to filters may apply to filters in
either the in-phase or quadrature path or using both.
[0020] Mixed signal 218a provided by mixer 216 is processed by a
series of filters 222a, 232a, 242a, which may be baseband filters.
These filters implement the overall interference rejection of the
baseband, and they may have programmable bandwidths with many
different settings. Although three stages of filters are shown in
this example, various numbers of filters may be used. In some
implementations, the filters provide progressively more rejection
as one moves further toward the output (toward the right side of
FIG. 2). Gain adjustment may be provided by a post-mixer amplifier
(PMA) 226a and variable gain amplifier (VGA) 246a.
[0021] Thus, mixed signal 218 is filtered by filter 222a to provide
signal 224a, which is amplified to provide signal 228a. The
amplified signal 228a is filtered to provide signal 234a and then
filtered to provide signal 244a, which is amplified to provide
signal 248a, which is a processed signal provided by the receiver
200. It is understood that signal 248b is also such a processed
signal provided by the receiver.
[0022] A logic module 250 includes a received signal strength
indication (RSSI) module 252, which measures signal strength (e.g.,
power or voltage) and provides an output 259 to an RSSI scanning
state machine 254. The state machine 254, which may be implemented
with digital logic circuitry, controls the bandwidth of the
receiver and the measurement channel (e.g., frequency). State
machine 254 also receives an input provided by a power spectral
density (PSD) computation module 253, which is used for baseband
signal processing and which may implement a (PSD) computation,
e.g., a fast Fourier transform (FFT), using known circuitry. State
machine 254 uses the RSSI and FFT information from modules 252 and
253 as part of an algorithm for improved scanning State machine 254
is coupled to a transmitter 280 that is configured to transmit
signals so that the receiver and transmitter may function as a
transceiver.
[0023] The architecture shown in FIG. 1 provides improved scanning
for base stations in a multi-mode environment. A wide bandwidth
filter is used to perform a set of scans as shown in FIG. 3. In
this example, the entire RF band is scanned by performing three
measurements identified in FIG. 3 as WB1, WB2, and WB3. For
example, a 60 MHz frequency band can be scanned with 3 measurements
using a 20 MHz LTE baseband filter. These 3 scans may result in the
FFT results shown in FIGS. 4A-4C for FFT with frequency resolution
of 180 kHz. The value of 180 kHz may be used in some embodiments
because it represents roughly the bandwidth of a typical narrowband
GSM signal and it is the average of 12 FFT bins for the 15 kHz LTE
spacing.
[0024] FIGS. 4A-4C are plots of example FFT results from wideband
scans WB1, WB2, and WB3, respectively, in accordance with some
embodiments. These results can be combined to provide an overall
spectral estimation for the entire frequency range as shown in FIG.
5.
[0025] FIG. 5 is a plot showing reconstructed band power spectral
density (PSD) which is computed by combining the PSD results (e.g.,
FFT results) associated with the respective wideband scans WB1,
WB2, and WB3. The reconstructed power spectral density is used to
estimate both the power and the type of signals present (or likely
present) in the RF band 100. For example, FIG. 5 shows region 501
that likely contains wideband LTE signal content; region 502 that
likely contains GSM signal content; region 503 that likely contains
no strong carriers; and region 504 that likely contains narrowband
LTE and/or TD-SCDMA or W-CDMA. The methodology for making these
determinations regarding regions 501, 502, 503, and 504 is
described below.
[0026] Observations of relatively high signal power over numerous
contiguous frequency bins may indicate the possible presence of
wideband LTE such as 20 MHz LTE, and therefore the search for those
signals can be limited to or minimally focused on a frequency
region (frequency band) having such a large number of contiguous
frequency bins. For example, region 501 may be identified as likely
containing wideband LTE content on the basis of detecting a
plurality of contiguous frequency bins (e.g., at least contiguous N
bins, where N is a positive integer) each corresponding to a power
higher than a predetermined threshold.
[0027] High signal power present in individual, isolated frequency
bins (e.g., bins computed by an FFT) indicates high probability of
a mode corresponding to a narrowband access technology such as GSM.
So again, the search for GSM signals may be limited to or focused
on the frequency region of interest. For example, region 502 may be
identified as likely containing GSM content on the basis of
detecting a one or more PSD spikes (e.g., three power spikes at
respective, non-contiguous bins of region 502 in the example
illustrated in FIG. 5), with each spike corresponding to a
frequency bin having a power exceeding the power at respective
neighboring bins by at least a predetermined threshold.
[0028] Region 503 may be identified as likely containing no strong
carriers on the basis of determining low signal power in the
corresponding frequency bins, e.g., in the case where none of the
bins in that region has power exceeding a predetermined
threshold.
[0029] Region 504 may be identified as likely containing narrowband
LTE and/or TD-SCDMA or W-CDMA on the basis of identifying a
specified number (e.g., a positive integer M) of contiguous bins
(e.g., with M<N, where N was described above in the context of
region 501) each corresponding to a power higher than a
predetermined threshold.
[0030] A similar approach may be used to focus the search for
particular access technologies in particular frequency regions. For
example, various modes may be assigned respective priorities, and
the modes may be searched in order of priority. Also, any region
that seems devoid of any signal may either be skipped altogether or
at least reprioritized based on this measurement result. For
example, region 503 may be assigned a priority lower than some or
all of regions 501, 502, 504 and then searched, or it may be
skipped altogether.
[0031] FIG. 6 is a flow diagram of a process in accordance with
some embodiments. After process 600 begins, various supported
access modes are ranked by preference (block 610). For example, the
ranking may be: 1. LTE 20 MHz; 2. LTE 5 MHz; 3. LTE 3 MHz; 4.
TD-SCDMA; 5. GSM. A wide filter bandwidth (e.g., 20 MHz as in FIG.
3) is set to perform a scan over the various regions (block 620).
The receiver 200 is set to each region corresponding a respective
wideband scan, and a power spectral density (PSD) of a signal is
computed (block 614), e.g., using a fast Fourier transform (FFT).
The PSD results are analyzed with an algorithm that looks for
certain patterns in the power spectral density. Various algorithms
may be used to analyze the spectrum. Once the likely regions for
particular access technologies are determined (block 616), an
access mode is considered based on priority (block 618). This
includes configuring the receiver to the bandwidth and operational
state associated with receiving the particular access mode. Then,
RSSI scanning is initiated (block 620). For a particular access
technology, the RSSI scanning may start with the most likely
frequency region based on the analysis of the power spectral
density or possibly (e.g., if no likely region is found) the scan
may be skipped or performed last. If the scan finds RSSI higher
than a predetermined threshold (YES at block 622), a
synchronization to a base station may be attempted (block 624). If
either the scanning does not find any channels with "good"
(sufficient) RSSI or if the synchronization fails (NO at block
626), then the next access mode in order of priority is checked
(block 618). If synchronization succeeds (YES at block 626), the
relevant channel may be "camped" on, i.e., maintained and used for
subsequent communications.
[0032] If process 600 completes without achieving synchronization,
a full search (on all possible channels) may be executed.
[0033] FIG. 7 is a flow diagram of another process in accordance
with some embodiments. After process 700 begins, an input signal
(e.g., signal 202) is provided (block 710) at an input to a
receiver (e.g., receiver 200). A bandwidth of the receiver is
controlled (block 720) to a predetermined wideband setting (e.g.,
20 MHz as for each of WB1, WB2, WB3 in FIG. 3). For each of a
plurality of frequency bands (e.g., WB1, WB2, WB3), blocks 730 and
740 are performed. At the receiver, the input signal is processed
(block 730) with a mixer, an amplifier, and a filter, to generate a
processed signal (e.g. signal 248a or signal 248b, or
alternatively, signals 248a and 248b may together be considered the
processed signal). A power spectral density of the processed signal
is generated (block 740) (e.g., using a fast Fourier transform)
over the particular frequency band, to provide a frequency domain
signal for that frequency band. Based on the frequency domain
signals corresponding to each frequency band in the plurality of
frequency bands, a frequency domain representation of the processed
signal is reconstructed (block 750) over a reconstruction band
(e.g., band including regions 501, 502, 503, 504 of FIG. 5) having
a bandwidth larger than the predetermined wideband setting. Based
on the reconstructed frequency domain representation, a spectral
component corresponding to at least one cellular telephony access
mode is identified (block 760).
[0034] FIG. 8 is an architecture diagram of a multiple
input/multiple output (MIMO) receiver in accordance with some
embodiments. A primary receiver module 820 and a diversity receiver
module 810 are coupled to a primary antenna 802 and a diversity
antenna 801, respectively. Each receiver module functions similarly
as receiver 200, and only differences associated with the MIMO
architecture are described herein for convenience. Primary receiver
module 820, which is coupled to RSSI module 850, is used for normal
scanning, and diversity receiver module 810, which is coupled to
power spectral density computation module (e.g., FFT module) 852,
is used for wideband scans. RSSI module 853 and FFT module 852
provide their outputs to state machine 854, which controls the
frequency (via a control signal sent to synthesizer 830) and
bandwidth of primary receiver module 820. The bandwidth of the
diversity receiver module 810 may be controlled independently.
[0035] Although examples are illustrated and described herein,
embodiments are nevertheless not limited to the details shown,
since various modifications and structural changes may be made
therein by those of ordinary skill within the scope and range of
equivalents of the claims.
* * * * *