Tuners – Variable inductor tuned
Reexamination Certificate
2002-02-27
2003-09-09
Ham, Seungsook (Department: 2817)
Tuners
Variable inductor tuned
C333S131000
Reexamination Certificate
active
06617947
ABSTRACT:
BACKGROUND OF THE INVENTION
In the telecommunications industry and more particularly in the video transmission industry signals (e.g., 5 MHz to 1 GHz) are carried over coax conductors from a headend to customers. At the headend of the systems, numerous signals are manipulated to achieve a wide variety of functions and objectives. For example, signals carried on numerous coax cables may be combined onto a single coax conductor. Similarly, a signal on a main coax conductor may be divided into a plurality of signals carried on branch coax conductors.
FIG. 1
is a top view of a portion of a circuit board having a tuning circuit according to the prior art. A circuit
10
is provided in which tuning coils are used to provide better isolation between ports of a splitter or combiner module. More particularly, the circuit
10
includes a printed circuit board
12
, a splitter inductor
14
, a first trace
16
and a second trace
18
. The first and second trace each have a first end
20
,
22
respectively and a second end
21
,
23
respectively. The second ends
21
,
23
of the first and second traces
16
,
18
are coupled together by the splitter inductor
14
. While the inductor
14
is referred to as a splitter inductor, the tuning circuit as described could be used in a combiner module. Located at the first ends
20
,
22
of the first and second traces
16
,
18
respectively, are a first port
25
and a second port
27
. If the circuit is being used in a splitter then the first and second ports
25
,
27
are output ports. If the circuit is being used in a combiner, then ports
25
,
27
are input ports.
Because the first and second traces
16
,
18
are physically and electrically connected through the inductor
14
, providing isolation between the traces becomes important. It has been found that to provide a better level of isolation between the first and second traces
16
,
18
, tuning coils
24
and a resistor
29
between the coils were placed on the circuit. In particular, a first via
26
and a second via
28
are provided on the circuit board. Each tuning coil
38
has a first leg
30
and a second leg
32
(see FIG.
2
). The first and second legs
30
,
32
fit in the first and second vias
32
,
34
. The tuning coils
24
can then be soldered to the circuit board
12
by any well known method. One tuning coil
24
is placed alongside the first trace
16
and the other tuning coil
24
is placed alongside the second trace
18
. Of course, since a splitter or combiner typically would have more than a first and second trace, separate tuning coils would be provided for each trace.
FIG. 2
is a perspective view of the prior art circuit shown in FIG.
1
. As can be seen in
FIG. 2
each tuning coil
24
has a double loop structure
38
. To tune the circuit, a frequency analyzer is coupled to the first and second traces
16
,
18
and, while monitoring the frequency response of that portion of the circuit, one adjusts the spacing between each loop by either pressing the loops closer together or pulling them further apart to tune that portion of the circuit.
FIG. 3
is an elevational view of a tuning coil according to the prior art. Such a tuning coil is typically made of copper and more preferably, copper wire having a gauge of 20 AWG. The tuning coil
24
when used in a combiner or splitter might have a length of 1.39 inches, a height of 0.32 inches and a thickness of 0.107 The loop
38
might have a diameter of 0.157 inches.
FIG. 4
is a side view of the prior art coil shown in FIG.
3
.
While the tuning circuit shown in
FIGS. 1-4
provides a degree of isolation, there is always a need to provide for better isolation between traces in a simple and inexpensive way.
SUMMARY OF THE INVENTION
According to a first aspect of the invention, there is provided a circuit for providing tuning on a circuit board. The circuit includes a first trace, a second trace and an inductor. The first trace and second trace each have a first end and a second end. The inductor couples the first trace and the second trace at their respective first ends. A first tuning coil and a second tuning coil are provided. The first tuning coil has a first leg and a second leg coupled together by a loop. The first and second legs are coupled to the circuit board alongside the first trace and the loop of the first tuning coil extends partially over the inductor coupling. The second tuning coil has a first leg and a second leg coupled together by a loop. The first and second legs are coupled to the circuit board alongside the second trace and the loop of the second tuning coil extends partially over the inductor coupling.
According to a second aspect of the invention, there is provided a NX
1
combiner circuit. The circuit includes N input traces, a first tuning coil and a second tuning coil. The N input traces are on a circuit board and are divided into N/2 pairs and each pair is coupled to a distinct inductor coupling. The first tuning coil has a first leg and a second leg coupled together by a loop. The first and second legs are coupled to the circuit board alongside a first trace of a pair and the loop of the first tuning coil extends partially over the inductor coupling associated with that pair. The second tuning coil has a first leg and a second leg coupled together by a loop. The first and second legs are coupled to the circuit board alongside a second trace of the pair and the loop of the second tuning coil extends partially over the inductor coupling associated with that pair.
According to a third aspect of the invention, there is provided a NX
1
splitter circuit. The splitter circuit includes N output traces, a first tuning coil and second tuning coil. The N output traces are on a circuit board and are divided into N/2 pairs and each pair is coupled to a distinct inductor coupling. The first tuning coil has a first leg and a second leg coupled together by a loop. The first and second legs are coupled to the circuit board alongside a first trace of a pair and the loop of the first tuning coil extends partially over the inductor coupling associated with that pair. The second tuning coil has a first leg and a second leg coupled together by a loop. The first and second legs are coupled to the circuit board alongside a second trace of the pair and the loop of the second tuning coil extends partially over the inductor coupling associated with that pair.
According to a fourth aspect of the invention, there is provided a method of tuning a circuit having a first trace having a first end and a second end, a second trace having a first end and a second end, an inductor coupling the first trace and the second trace at their perspective first ends, a first tuning coil having a first leg and a second leg coupled together by a loop wherein the first and second leg are coupled to the circuit board alongside the first trace, and a second tuning coil having a first leg and a second leg coupled together by a loop wherein the first and second legs are coupled to the circuit board alongside the second trace, The method includes the steps of bending the loop of the first tuning coil so that the loop of the first tuning coil extends partially over the inductor coupling, bending the loop of the second tuning coil over the loop of the first tuning coil so that the loop of the second tuning coil extends partially over the inductor coupling and the loop of the first tuning coil, and adjusting the distance between the loop of the first coil and the loop of the second coil until a desired amount of isolation is achieved between the first trace and the second trace.
According to a fifth aspect of the invention, there is provided an apparatus for providing tuning on a circuit board. The apparatus includes a first tuning coil and a second tuning coil. The first tuning coil has a first leg and a second leg coupled together by a loop and the first and second legs are coupled to a circuit board alongside a first trace. The second tuning coil has a first leg and a second leg coupled together by a loop and the first and second le
ADC Telecommunications Inc.
Ham Seungsook
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