Transceiver systems and methods that preserve frequency...

Details Transceiver systems and methods that preserve frequency... Transceiver systems and methods that preserve frequency...

1998-05-28

2001-11-27

Trost, William (Department: 2683)

Telecommunications

Wireless distribution system

C455S003020, C455S084000, C455S003050

Reexamination Certificate

active

06324379

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to transceivers and more particularly to wireless cable transceivers.
2. Description of the Related Art
FIG. 1
illustrates signal bands that are associated with a variety of communication services that deliver communication signals to consumers. In the oldest of these communication services, off-air television and frequency modulation signals are received through a consumer antenna. Off-air television channels are arranged in three different signal bands that are included in a frequency span of 54-800 MHz and off-air frequency modulation signals extend across a signal band of 88-108 MHz. Subsequently, consumers were offered the alternative of cable television (CATV) in which hard cables deliver television and frequency modulation signals to consumer dwellings over a CATV signal band of 54-648 MHz. Off-air and CATV communication signals are, therefore, substantially contained within a consumer signal band
10
of
FIG. 1
that spans 5-750 MHz.
Consumers can presently choose between an additional pair of communication services. In a first one of these services, communication signals are provided by a direct broadcast satellite (DBS) system. In this system, satellites radiate microwave signal beams in C-band frequencies (e.g., 3.7-4.2 GHz) and Ku-band frequencies (e.g., 11.7-12.75 GHz). Upon direct receipt at a consumer antenna, these satellite signals are initially downconverted to a signal band of 950-1450 MHz before further downconversion and detection at either 479 MHz or 70 MHz.
In a second one of these services, communication signals are provided by a wireless cable system in which signals are directed from a service provider's antenna to a plurality of subscriber antennas. The signals can be sent over two different wireless cable signal bands. One band is the multipoint distribution service (MDS) frequency band
11
of
FIG. 1
that spans 2150-2162 MHz. The other band is the multichannel multipoint distribution service (MMDS) frequency band
12
that extends across 2500-2686 MHz. Signals in these wireless cable bands are typically downconverted at subscriber dwellings by low noise block downconverters (LNB's) that use a converter signal
13
at 2278 MHZ to form MDS and MMDS intermediate frequency bands
14
and
15
that respectively span 116-128 MHz and 222-408 MHz.
The communication signals provided by these consumer services were initially limited to television and frequency modulation signals. Consumers are now being offered, however, an increasing list of other communication options. For example, a communication service can operate as an internet service provider (ISP) who provides access to the internet. It was also initially envisioned that signals were only downlinked to consumers but some of these communication services have now become two-way streets in which consumers uplink data signals (e.g., signals associated with the activities of pay-for-view, banking, home shopping, medical alarm and fire/security).
In the past, uplink data from consumers has typically been channeled over telephone lines. As a first example, consumers communicate home shopping selections over their telephones to wireless cable providers. As a second example, consumer computers communicate through modems and telephone lines with internet ISP's. Telephone lines and conventional modems, however, form a speed bottleneck in these data communications because of their low transmission rates (typically less than 56 kbps).
To provide a path around this bottleneck, the signal band
10
of
FIG. 1
is now generally divided into an uplink signal band
16
of 5-65 MHz for consumer uplinking of data signals and a downlink signal band
17
of 50-750 MHz for provider downlinking of communication signals. Recently introduced data interface modules (e.g., cable modems) take advantage of the higher uplink bandwidth. Accordingly, these modules have significantly higher data transmission rates (e.g., 500 kbps-3 Mbps).
The provider antenna-subscriber antenna structure of wireless cable is especially suited for two-way signal flow. As stated previously, communication signals from wireless cable headends are typically downconverted at subscriber dwellings by LNB's and subscriber data is presently communicated back to the headend by telephone lines which have the speed limitation referred to above. This data path limitation could be removed by provision of a high-speed uplink path. In anticipation of this, a pair of data-uplink signal bands have been proposed. One is a limited-bandwidth (2686.0625-2689.8125 MHz) instructional television fixed service (ITFS) signal band and the other is a wider-bandwidth (2305-2360 MHz) wireless communication service (WCS) signal band. These are respectively shown in
FIG. 1
as signal bands
18
A and
18
B.
In an exemplary uplink path proposed in U.S. Pat. No. 5,437,052 (issued Jul. 25, 1995 to Hemmie, et al.), a bi-directional converter has a downconverter for downconverting MMDS programming signals (i.e., signals in the MMDS band
13
of
FIG. 1
) to converted signals in the 222-408 MHz range (i.e., intermediate frequency band
16
in
FIG. 1
) and an upconverter that converts data/information signals in the 116-128 MHz range (i.e., intermediate frequency band
15
in
FIG. 1
) to the MDS signal band (i.e., MDS band
12
in FIG.
1
).
This proposed uplink path, however, ignores a frequency gap
19
between the uplink signal band
16
and the intermediate frequency MDS band
14
of FIG.
1
. Subscribers wishing to access this uplink path with data interface modules that operate in the uplink signal band
16
, would have to purchase additional interface modules that could span the frequency gap
19
. In addition, if this upconversion structure is used to communicate data to the MDS band (
11
in FIG.
1
), it will invert the data's frequency order in contrast to the conventional MMDS downconversion process which does not invert frequency order. This inversion typically creates problems in communication and data transfer systems.
SUMMARY OF THE INVENTION
The present invention addresses full-duplex, coherent transceivers that can directly couple exiting data interface modules to wireless cable providers and thus establish a high-speed uplink path for subscriber data flow that complements an existing high-speed downlink path for communication signals.
In particular, such transceivers can directly couple data interface modules (e.g., cable modems) operating in the uplink and downlink signal bands
16
and
17
of
FIG. 1
to wireless cable providers through signal bands at the providers' transmission antennas. With this direct interface, subscriber communication devices (e.g., computers, telephones and television displays) can be coupled in high-speed two-way paths with wireless cable providers (and, from there, to other resources such as the internet). Equipment to provide this two-way access is limited to the transceiver, a subscriber antenna and a hookup cable between the externally-positioned transceiver and communication devices inside the subscriber's dwelling. Subscribers are thus spared the cost of additional interface devices (e.g., devices that can span the frequency gap
19
of FIG.
1
).
These goals are achieved with transceivers that position a downconverter mixer in a downconversion path and serially-arranged first and second upconverter mixers in an upconversion path. A stable signal source (e.g., a microwave oscillator phase-locked to a crystal) provides mixer signals to the downconverter mixer and the second upconverter mixer and a frequency divider couples the signal source and the first upconverter mixer.
Accordingly, all mixers convert with coherent signals and the phase coherency required for two-way flow of provider-subscriber signals (e.g., television, internet and telephony signals) is preserved. The division of the frequency divider can be chosen to place the upconverted data signals into selected microwave signal bands at a wirel

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