Pulse or digital communications – Transceivers – Transmission interface between two stations or terminals
Reexamination Certificate
1998-10-20
2002-07-30
Le, Amanda T. (Department: 2634)
Pulse or digital communications
Transceivers
Transmission interface between two stations or terminals
C375S257000, C375S285000, C379S399010, C370S284000, C370S285000, C333S02400C
Reexamination Certificate
active
06426970
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present method and apparatus generally relate to a system for the simultaneous transmission and reception of signals over a single transmission medium utilizing a common path for both transmission and reception, and more particularly, to a bi-directional signal coupler for use with the single transmission medium.
2. Discussion of the Related Art
In the field of radio frequency (RF) interconnections, there exists a strong need to have devices, referred to herein as bi-directional couplers, for coupling both a transmitter and a receiver to a single communication medium. In a typical bi-directional transmission/reception communication system
10
as shown in
FIG. 1
, a transmitter
12
and receiver
14
operate simultaneously and at the same frequency for sending and receiving signals, respectively, over the communication medium
16
. In the latter instance, signals are only differentiated by the direction in which the respective signals are proceeding. A bi-directional coupler
18
couples transmitter
12
and receiver
14
to the communication medium
16
. A second bi-directional coupler
20
couples a second receiver
22
and second transmitter
24
to communication medium
16
. Signals transmitted by transmitter
12
are send across communication medium
16
and received by receiver
22
. Similarly, signals transmitted by transmitter
24
are transmitted across communication medium
16
and received by receiver
14
.
With reference still to
FIG. 1
, two bi-directional couplers
18
and
20
are shown connected to each other via the communication medium
16
. The communication medium
16
can be either a wired communication medium or a wireless communication medium. An exemplary wire medium includes a current-conducting medium. An exemplary wireless medium includes the use of RF (radio frequency) waves transmitted and received over a non-conductive path such as air. Other communication mediums are also contemplated, including optical fiber and such mediums as may additionally require the use of encoders, decoders, modulators, and/or demodulators, or other devise(s) necessary to facilitate the use of or interface the bi-directional coupler with the actual medium.
Major disadvantages and/or problems which occur in bi-directional coupling devices (
18
,
20
), such as illustrated in
FIG. 1
, include insertion loss, rejection ratio, and parts precision. Insertion loss can be characterized, for example, in terms of the amount of transmitted energy from transmitter
12
that gets through the bi-directional coupler
18
and onto the connecting communication medium
16
. Insertion loss may likewise be characterized in terms of the amount of transmitted energy from transmitter
24
that gets through the bi-directional coupler
20
onto the communication medium
16
. An insertion loss of zero decibels (0 dB) would be highly desirable, however, typical insertion loss is on the order of −10 dB. The insertion loss of 10 dB suggests an approximate ninety percent (90%) loss of power as a normal loss through a standard bi-directional coupler.
Rejection ratio is an attribute of a bi-directional coupling device and is characterized as a measure of how much of the signal which is transmitted via the transmit port is received by (i.e., comes out of) the receive port of the same bi-directional coupler. That is, with reference to
FIG. 1
, rejection ratio is characterized as a measure of an amount of signal from transmitter
12
which is delivered into receiver
14
from bi-directional coupler
18
will undesirably limit the detection range of receiver
14
with respect to signals present on medium
16
which are traveling toward receiver
14
.
In connection with the rejection ratio, component parts precision plays a significant role. Parts precision can be characterized as the quality of rejection that results from balancing of an electronic bridge in the particular bi-directional coupler. The electronic bridge of a bi-directional coupler is highly dependent upon a precision of the components or component parts that make it up. Parts tolerance, especially over a temperature range, is therefore a critical factor to the maintaining of a high rejection quality.
With reference now to
FIG. 2
, a bridge
26
from a general class of bridges used in typical bi-directional coupler devices is illustrated. That is, with typical bi-directional coupler devices, a balanced bridge
26
is employed. With the use of the bridge
26
, a bi-directional coupler operates in accordance with a process for nulling, removing, or subtracting a first signal, which is to be transmitted, in such a way as to only be able to detect a second signal, which is to be received. A typical manner for nulling the transmitted signal is to use a version of the transmitted signal to cancel itself at the receive output port of the bi-directional coupler, leaving only the incoming (received) signal at the receive output port. Variations of a bridge which can be used to provide less forward signal loss but otherwise still suffers from the limitations as discussed above, are shown in
FIGS. 3A
,
3
B, and
3
C, to be discussed further herein below.
With respect to
FIG. 2
, the bridge
26
is made up of resistive elements
28
(Z
1
) and
30
(Z
2
) for one side
32
(or “leg”) of the bridge
26
. A resistive element
34
(Z
3
) and a cable impedance
36
form the other side
38
(or “leg”) of the bridge
26
. A signal to be transmitted is coupled across nodes
40
and
42
of bridge
26
. A signal to be received is detected across nodes
44
and
46
.
With respect to
FIG. 3A
, bridge
50
is made up of resistive elements
52
(R
2
) and
54
(R
3
) for one side
56
(or leg) of the bridge. The resistive element
58
(R
1
) and a cable impedance
60
form the other side
62
(or leg) of the bridge
50
. A signal to be transmitted (denoted “A”) is input to bridge
50
at node
64
. A signal to be received (denoted “B”) is output from bridge
50
at node
66
. Referring still to
FIG. 3A
, the signal to be transmitted is further coupled to a high input impedance buffer
68
, and further coupled via an isolation transformer
70
(T
1
).
Turning now briefly to
FIG. 3B
, bridge
72
is similar to bridge
50
of
FIG. 3A
except for the presence of additional resistive elements
74
,
76
,
78
and
80
. Resistive elements
82
and
84
contribute to one side
86
(or leg) of bridge
72
. A resistive element
88
and a cable impedance (L/O line)
90
contribute to the other side
92
(or leg) of bridge
72
. A signal to be transmitted (Tx) is input to bridge
72
at node
94
. A signal to be received (Rx) is output from bridge
72
at node
96
. Referring still to
FIG. 3B
, the signal to be transmitted (Tx) is further coupled to a resistive element
98
, which is further coupled to isolation transformer
100
(T
1
).
With reference now to
FIG. 3C
, bridge
102
includes resistive and impedance elements. Winding
104
of isolation transformer
106
and resistive element
108
contribute to one side
110
(or leg) of bridge
102
. Resistive elements
112
,
114
, and
116
, winding
118
of isolation transformer
106
, and the cable impedance
120
(I/O line) contribute to the other side
122
(or leg) of bridge
102
. A signal to be transmitted (Tx) is input to bridge
102
at node
124
. A signal to be received (Rx) is output from bridge
102
at node
126
.
The above described method for nulling a transmitted signal in order to detect a received signal at a bi-directional coupler
18
ultimately requires the use of a bridge. In the above-mentioned illustrations in
FIGS. 2
,
3
A,
3
B, and
3
C, the bridge is made up of resistive elements R
2
(Z
1
) and R
3
(Z
2
) for one side (or “leg”) of the bridge, while the resistive element R
1
(Z
3
) and a cable impedance form the other side (or “leg”) of the bridge. In such a bridge, there is a practical limit to the amount of signal cancellation that can be achieved with the use of standard, commercially available, component parts
Long Jack E.
Thornton Barry
Clearcube Technology, Inc.
Conley Rose & Tayon PC
Le Amanda T.
LandOfFree
Bi-directional signal coupler method and apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bi-directional signal coupler method and apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bi-directional signal coupler method and apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2832988