U.S. patent number 3,789,331 [Application Number 05/293,465] was granted by the patent office on 1974-01-29 for vernier tuning means for uhf tuner or the like.
This patent grant is currently assigned to General Instrument Corporation. Invention is credited to Edward Balash, Carroll R. Miner.
United States Patent |
3,789,331 |
Miner , et al. |
January 29, 1974 |
VERNIER TUNING MEANS FOR UHF TUNER OR THE LIKE
Abstract
In a conventional variable capacitor type tuner, in which the
rotor plates optionally may be provided with positionally
adjustable sections which sequentially and cumulatively come into
capacitive relationship with a stator plate of appreciable area,
vernier tuning is accomplished by providing an additional stator
plate of limited area which cooperates with its own rotor having
individually positionable sections of substantially the same
angular extent as the corresponding stator and which come
sequentially and non-cumulatively into operative relationship with
the stator. The individually positionable sections of the vernier
rotor may be staggered with respect to the individually
positionable sections of the standard rotor for optimum results.
The vernier rotor can generally be similar to the standard rotor in
having its sections extend generally at right angles to the axis of
rotation, in which case where many channels are to be tuned the
individual sections of the vernier rotor may encompass the tuning
of a limited plurality of said channels, or the sections of the
vernier rotor may comprise extensions thereof extending generally
parallel to the axis of rotation thereof, in which case a larger
number of individual sections can be provided than with
conventional rotors.
Inventors: |
Miner; Carroll R. (Wilbraham,
MA), Balash; Edward (Chicopee, MA) |
Assignee: |
General Instrument Corporation
(Newark, NJ)
|
Family
ID: |
23129196 |
Appl.
No.: |
05/293,465 |
Filed: |
September 29, 1972 |
Current U.S.
Class: |
334/82;
361/298.5; 361/299.4; 334/78; 334/83 |
Current CPC
Class: |
H03J
3/20 (20130101) |
Current International
Class: |
H03J
3/00 (20060101); H03J 3/20 (20060101); H03j
003/20 () |
Field of
Search: |
;334/78,79,82,83
;317/253,254 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lawrence; James W.
Assistant Examiner: Chatmon, Jr.; Saxfield
Attorney, Agent or Firm: Maxwell James et al.
Claims
We claim:
1. In a high frequency tuner, variable capacitor means comprising
first and second capacitors each comprising a stator and a rotor,
the stators of said two capacitors being directly electrically
connected, the rotors of said two capacitors being directly
electrically connected and operatively mechanically connected for
simultaneous movement over first and second given distances
respectively to tune over the desired range, said stator of said
first capacitor having a dimension extending in the general
direction of said movement of said rotor of said first capacitor
which at least substantially corresponds to said first movement
distance, said rotor of said first capacitor having a dimension
extending in the said general direction of said movement of said
rotor which at least substantially corresponds to said first given
distance, said rotor being movable over said first given distance
between positions of minimum and maximum operative overlap with
said stator, said stator of said second capacitor having a
dimension extending in the general direction of movement of said
rotor of said second capacitor which is only a minor fraction of
said second given distance, said rotor of said second capacitor
having a dimension extending in the said general direction of
movement of said rotor which is much larger than the corresponding
dimension of said stator of said second capacitor and being divided
into a plurality of sections each having a dimension in the said
general direction of movement of said rotor approximately that of
said stator of said second capacitor and movable sequentially into
and out of operative overlap with their corresponding stator as
said rotor is moved from end of the desired range to the other, the
spacing of said sections relative to their corresponding stator
when overlapping said stator being individually adjustable, thereby
to facilitate the adjustment of the capacitance-rotation
characteristic of said capacitor means for a multiplicity of
rotational points.
2. The tuner of claim 1, in which said rotor of said first
capacitor is divided into a plurality of sections each having a
dimension in the general direction of movement of said rotor which
is a fraction of the corresponding overall dimension of said rotor
and movable sequentially into cumulative operative overlap with
their corresponding stator as said rotor is moved from one end of
the desired tuning range to the other, the spacing of said sections
relative to their corresponding stator while overlapping said
stator being individually adjustable.
3. The tuner of claim 2, in which said sections of said first
capacitor are separated from one another at a first set of points
spaced from one another in the general direction of movement of
said rotor and said sections of said second capacitor are separated
from one another at a second set of points spaced from one another
in the general direction of movement of said rotor and differing
from said first set of points.
4. The tuner of claim 3, in which said first set of points and said
second set of points alternate with each other in the general
direction of movement of said rotor.
5. The tuner of claim 3, in which said first set of points and said
second set of points alternate with each other substantially
uniformly in the general direction of movement of said rotor.
6. The tuner of claim 1, in which said tuner is a UHF tuner
designed to tune over substantially the seventy channels of the UHF
band, and said dimension of said stator of said second capacitor
corresponds to the tuning of about six channels in the UHF
band.
7. The tuner of claim 6, in which said rotor of said first
capacitor is divided into a plurality of sections each having a
dimension in the general direction of movement of said rotor which
is a fraction of the corresponding overall dimension of said rotor
and movable sequentially into cumulative operative overlap with
their corresponding stator as said rotor is moved from one end of
the desired tuning range to the other, the spacing of said sections
relative to their corresponding stator while overlapping said
stator being individually adjustable.
8. The tuner of claim 7, in which said sections of said first
capacitor are separated from one another at a first set of points
spaced from one another in the general direction of movement of
said rotor and said sections of said second capacitor are separated
from one another at a second set of points spaced from one another
in the general direction of movement of said rotor and differing
from said first set of points.
9. The tuner of claim 8, in which said first set of points and said
second set of points alternate with each other in the general
direction of movement of said rotor.
10. The tuner of claim 8, in which said first set of points and
said second set of points alternate with each other substantially
uniformly in the general direction of movement of said rotor.
11. The tuner of claim 7, in which said sections of said rotor of
said first capacitor have a said dimension corresponding to the
tuning of about six channels in the UHF band.
12. The tuner of claim 8, in which said sections of said rotor of
said first capacitor have a dimension corresponding to the tuning
of about six channels in the UHF band.
13. The tuner of claim 9, in which said sections of said rotor of
said first capacitor have a said dimension corresponding to the
tuning of about six channels in the UHF band.
14. The tuner of claim 10, in which said sections of said rotor of
said first capacitor have a said dimension corresponding to the
tuning of about six channels in the UHF band.
15. The tuner of claim 1, in which said rotor and said stator of
said first capacitor comprise parallel plates with said rotor
rotatable about an axis substantially at right angles to said
plates, and said rotor and stator of said second capacitor comprise
parallel plates substantially perpendicular to the corresponding
parts of said first capacitor.
16. The tuner of claim 1, in which said rotor and said stator of
said first capacitor comprise parallel plates with said rotor
rotatable about an axis substantially at right angles to said
plates, and said rotor and stator of said second capacitor means
comprise parallel plates substantially parallel to the
corresponding parts of said first capacitor.
17. The tuner of claim 1, in which said rotor of said second
capacitor comprises a member rotatable about an axis and having
said sections extending therefrom substantially in the same
direction as said axis, the stator of said second capacitor being
mounted adjacent said sections to extend in a direction
substantially parallel thereto.
18. The tuner of claim 1, in which said rotor of said second
capacitor comprises a disk rotatable about an axis, said sections
of said capacitor means being defined by fingers arranged
circumferentially around said disk and extending therefrom in a
direction substantially parallel to said axis, the stator of said
second capacitor being mounted adjacent said sections to extend in
a direction substantially parallel thereto.
Description
The present invention relates to means for achieving vernier
control of tuning in tuners such as those designed for use in the
UHF reception band.
It has long been known that the various circuits of a
communications receiver such as a television receiver may be tuned
by gang condenser means, comprising a plurality of rotary variable
condensers the rotors of which move simultaneously and overlap
their corresponding stator plates to cumulatively progressive
degrees. It is necessary that the individual circuits thus
simultaneously tuned track one another over the entire range of
tuning, that is to say, the variation in capacitance, and hence in
tuned frequency, accomplished in each of the circuits should
correspond in desired fashion to the variation accomplished in all
of the other circuits. In addition, it is usually desired that
there be a certain desired relationship between tuned frequency and
angular rotation of the operating shaft. To these ends it is
conventional to provide in rotary variable condensers some means
for manual adjustment of the capacity curve of one or more of the
tuning sections. This is commonly done by serrating or slotting one
or both of the outer blades so that the sections of the blades thus
formed between the serrations or slots may be bent toward or away
from the stator plates, thereby to change the incremental capacity
value achieved at discrete angles of rotation. This approach has
proven to be adequate in many tuning requirements to comply with
tracking requirements and conformance to a desired calibration
curve.
The UHF television band in this country contains 70 channels each 6
mc. wide between 470 MHz and 890 MHz. The tuner is conventionally
of the superheterodyne type using an intermediate frequency 45.75
MHz., for the visual carrier of the television signal, thus giving
rise to the requirement of a local oscillator range of 517-931 MHz.
Recent governmental requirements relating to tuners capable of
tuning all seventy of the available UHF channels explicitly and
implicitly require tuning accuracies over the large frequency range
involved which have not been achievable by prior art approaches.
For example, it is required that each channel selected must tune
within one-half a channel width of the correct frequency without
the aid of manual fine tuning. This involves an accuracy of plus or
minus 3 MHz. In terms of the absolute frequency of the local
oscillator, this represents a variation of approximately plus or
minus 0.3 percent, and in terms of the band coverage, this
represents approximately plus or minus 0.7 percent. Even these
rigorous requirements will not permit automatic fine tuning; if
automatic fine tuning is desired, the problem becomes most
forbidding, requiring approximately six times the precision
specified above.
In the UHF band tuning is typically accomplished by the rotation
(usually through 180.degree. or less) of a variable capacitor which
terminates a quarter wave or half wave distributed constant
transmission line which is the resonant element of either a tube or
solid state amplifier or oscillator circuit. The relationship
between capacitance of the terminated variable condenser of a
resonant transmission line and the frequency to which that line is
tuned is quite complex, but to a rough approximation the
capacitance varies inversely as the square of the frequency tuned.
In UHF tuners it is desirable for the frequency to vary linearly
with tuning so that equal angular rotation will generate equal
tuning changes, thus providing for tuning from one channel to
another by equal angular rotation no matter where those channels
may be in the UHF band. This can be done, as has been known to the
art, by using specially shaped capacitor plates, generally of the
conventional rotary variable condenser type, in which the stator
plate or plates have an area or angular extent, considered in terms
of the movement of the rotor plate between one tuning extreme and
the other, which encompasses substantially the full degree of
movement of the rotor plate, the rotor plate being movable from one
extreme position where it overlaps the stator plate either not at
all or to a minimal degree (minimum capacitance and maximum
frequency) to another extreme position in which it overlaps the
stator plate to a maximum degree (maximum capacitance and minimum
frequency). Thus the individual segments of the rotor plate move
sequentially into operative engagement with the stator plate as the
rotor plate is moved from its position of minimal overlap to its
position of maximum overlap, with a segment of the rotor plate once
moved into overlapping relation with the stator plate remaining in
that overlapping relationship as the rotor plate moves further to
its position of maximum overlap. Hence each segment of the rotor
plate, once it comes into overlapping relationship with its stator
plate, acts cumulatively with those segments of the rotor plate
which had theretofore overlapped the stator plate and those
segments of the rotor plate which thereafter come to overlap the
stator plate.
As has been mentioned, the conventional approach to vernier control
of capacitance with variable capacitance tuners of the type
described is to serrate one or more of the rotor plates into
sections and then to bend those sections individually toward or
away from the corresponding stator plate. If the section is bent
toward the corresponding stator plate it will, when it comes into
overlapping relationship therewith, produce a higher capacitance
therewith than when it is bent away therefrom. The conventional
alignment approach when using a serrated rotor blade of the type
described is to start at the high frequency end of the band, when
the rotor is at its position of minimum overlap with the stator,
adjust the first section of the stator, and move respectively to
lower frequencies as succeeding sections come into operative
engagement with the stator plate and then adjust those other
sections in appropriate fashion. The effects of these adjustments
are cumulative in that the total tuning capacity at any point of
rotation includes the sum of the effects of each of the adjustments
made up to that point on the rotor blade sections overlapping the
stator plates.
This system has two primary disadvantages - first, because the
adjustments are effectively cumulative, if, after the alignment is
accomplished, an additional correction is needed at some point in
the band and a readjustment is made, all frequencies in the band
lower than the frequency at which the adjustment is made are
affected and it is necessary then to readjust all of those other
sections. Second, each section optimizes the tuning for but a
single point over a range of frequencies, and hence the degree to
which the tuning curve is affected for all frequencies is often far
from optimal.
The adjustment problems presented by normal tuning requirements are
greatly intensified when a very large number of channels must be
tuned, such as the seventy channels involved in the UHF band. If an
individual segment is to be provided in the rotor plate for each of
those bands, and because as a practical matter the rotor plates
cannot be turned more than 180.degree., the physical constraints
required in attempting to provide seventy tabs or segments, each
individually adjustable, are prohibitive. In tuning over the VHF
band where only 12 channels are involved, providing an individually
adjustable segment on the rotor plate for each channel would
require segments occupying 15.degree. of rotation about the axis of
rotation of the rotor. This is an entirely practical value.
However, if 70 individual segments must be provided, those segments
could be only 2.6.degree. wide. This would leave only about 0.02
inch of metal at a 1/2 inch radius from the axis of rotation.
Closer to the axis of rotation the width of the tab would become
vanishingly small. These values do not even take into consideration
the fact that some spacing would have to be left between the tabs
where material was removed from the rotor plate.
Thus both physical requirements and electrical requirements,
including the realities of adjustment procedure, appear to rule out
the use of individually adjustable rotor plate segments in order to
provide vernier tuning in the UHF band.
It is the prime object of the present invention to provide means
for control of tuning by a variable capacitor tuner which is
accurate, which is easily accomplished by means of practical and
sturdy structure, and which is particularly adaptable for tuning
requirements where a very large number of channels or stations must
be tuned.
It is another object of the present invention to provide a
vernier-controlled tuning system which utilizes conventional rotary
variable condenser-type tuners and which adds thereto, for vernier
tuning control, structure which takes up but a minimal amount of
space and costs but a minimal amount of money and which requires no
great precision in manufacture.
It is yet another object of the present invention to provide a
rotary variable condenser-type of tuner with a much greater degree
of tracking adjustability in its tuning operation and has not
heretofore been achievable except through the use of the most
complex, expensive and easily misaligned equipment.
It is a still further object of the present invention to devise a
vernier tuning system of a rotary variable type of capacitor tuner
in which vernier adjustment of the tuning effect at a given
location in the tuning band may be carried out independently, and
without requireing any modification of the tuning band.
To these ends, we provide a second variable capacitor means
electrically connected to the standard capacitor means, but
differing therefrom in that the stator plate, instead of having an
area or angular extent in the direction of movement of the rotor
substantially corresponding to the entire tuning movement of the
rotor and therefore to the entire tuning range, in fact has an area
or angular extent of much lesser size, corresponding to a single
channel to be tuned or to a small plurality of channels to be
tuned. The rotor plate of this second capacitor means comprises a
plurality of individually adjustable sections each having an area
or angular extent in the direction of movement of the rotor,
substantially corresponding to that of the stator plate with which
it cooperates. Consequently as the rotor is moved these sections
will be brought sequentially into overlapping relationship with the
stator plate, but in a non-cumulative manner - one such section
will be moved away from the stator plate as the next section is
moved into overlapping relationship with the stator plate. This
type of tuning arrangement has been known. It has, however, been
used only per se, as the tuning device in a given installation.
What we have discovered, considered broadly, is that by using this
non-cumulative type of tuning arrangement in conjunction with the
conventional cumulative type of capacitive tuner, a very high
degree of accuracy in tuning relationship, sufficiently high to
satisfy the exacting modern requirements for a seventy-channel UHF
tuners, can be achieved.
Where physical requirements make it impractical or impossible to
provide individually adjustable rotor sections for each of the
channels to be tuned, as is the case in connection with 70 -channel
UHF tuning, each of the individually adjustable rotor sections may
be made of sufficient area or angular extent to correspond to a
small plurality of the channels to be tuned, to wit, five to seven
channels out of 70, and an even greater degree of precision is
obtained when the conventional rotor is provided with the usual
cumulatively acting adjustable sections, but with the sections on
the conventional rotor rotationally staggered with respect to the
sections of the vernier rotor.
In the usual type of variable capacitor tuner, the rotor and stator
blades, parallel to one another, extend in a direction
substantially at right angles to the axis of rotation of the rotor
blades. The vernier tuning capacitor involved in the present
invention may be similarly constructed. However, for even greater
accuracy, and for more individual control of the many channels
involved, a special form of vernier condenser is disclosed in which
the individually adjustable sections of the rotor extend in a
direction substantially parallel to the axis of rotation of the
rotor and are arranged circumferentially around a disk-like
support. With this structure a much larger number of strong and
reliably adjustable sections can be produced mechanically than with
the convential rotor plate construction where the sections must
extend radially outwardly from the axis of rotation.
To the accomplishment of the above, and to such other objects as
may hereinafter appear, the present invention relates to the
structure and arrangement of a tuning instrumentality as defined in
the appended claims and as described in this specification, taken
together with the accompanying drawings, in which:
FIG. 1 is a top plan view of a section of a tuner constructed in
accordance with the present invention showing two tuning circuits
such as might be employed for the detector and the local oscillator
of a superheterodyne receiver;
FIG. 2 is a front elevational view of a convential rotor plate used
in the main tuning portion of a given tuning section;
FIG. 3 is a front elevational view of the rotor plate used in the
vernier tuning section of the tuner of the present invention;
FIG. 4a is a composite rear elevational view of the conventional
rotor plate of FIG. 2 and the stator plate with which it
cooperates, the rotor plate being shown in a position toward the
low frequency end of the tuning band;
FIG. 4b is a composite rear elevational view of the rotor plate of
FIG. 3 and the stator plate with which it cooperates, showing the
same relative rotational position as corresponds to that of the
rotor and stator plates in FIG. 4a;
FIGS. 5a and 5b are views similar to FIGS. 4a and 4b respectively
but showing the rotor plates in their respective positions relative
to their respective stator plates at a higher tuning frequency than
that shown in FIGS. 4a and 4b;
FIGS. 6a and 6b are views similar to FIGS. 5a and 5b respectively
but showing the parts in the positions which they assume at a still
higher tuning frequency; and
FIG. 7 is a view similar to FIG. 1 but showing a specifically
different construction for the vernier tuning capacitor.
The invention is here specifically disclosed in connection with a
tuner designed to tune all seventy of the channels in the UHF band,
that being done because the tuner of the present invention is
exceptionally well adapted to meet the tuning requirements there
involved, while other tuning arrangements have failed to meet those
requirements. It will be appreciated, however, that the invention
is not limited to that particular application, but may be applied
more broadly. Moreover, while the capacitive tuners have been here
disclosed as of the rotary variable type, the terms "rotor" and
"stator" therefore being applied to the relatively movable and
stationary parts thereof in conventional fashion, it will be
understood that rotary movement of the parts relative to one
another is not essential to their operative tuning relationship,
nor is it essential that one of the elements stand still while the
other moves - they both could move, either in the same direction at
different speeds or in opposite directions. Hence it will be
appreciated that the terms "rotor" and "stator" are used
generically, the term "rotor" referring to a movable element and
the term "stator" referring to an element which may either be
stationary or movable but with respect to which the "rotor" moves.
It will further be understood that although the tuners are here
disclosed as embodied in quarter wave or half wave transmission
line structures, that is exemplary only, and they could be used in
conjunction with any circuitry or structure by means of which an
electrical tuning condition is produced.
FIG. 1 is an idealized view on an enlarged scale, of a tuner such
as might be employed, in accordance with the present invention, for
tuning over the entire seventy channel range of the UHF band. It
comprises conductive side walls 2 and partitions 4 which divide the
interior structure into compartments 6 and 8 which house the tuning
structure for two different circuits, such as the detector and the
local oscillator. Each of those individual tuning devices, as
hereby specifically disclosed, are of the transmission line type,
including an elongated conductive element 10 which extends from one
end wall of a given compartment 6 or 8 toward the other end wall
thereof and spaced from the bottom wall thereof, and which carries
at its end a plurality of electrically connected stator plates 12.
Mounted for rotation in the tuner is a shaft 14 which, in each
compartment 6 and 8, has rotor plates 16 secured thereto and
rotatable therewith. The plates 12 and 16 define a variable
capacitor which, in conjunction with the conductor 10 and the walls
2 and 4, define a resonant cavity transmission line the resonant
frequency of which is determined by the capacitance defined between
the stator plates 12 and the rotor plates 16. As is shown in FIG.
4a, the stator plates 12 are of a considerable area and,
considering that area in terms of angular rotation about the axis
of 14' of the shaft 14, the plates 12 extend about the axis 14'
over approximately 180.degree., that being the full extent of
rotation of the shaft 14 from one extreme of the tuning range to
the other. As may be seen from FIGS. 2 and 4A, the rotor plates 16,
mounted fast on the shaft 14 by means of the recess 18 formed in
the plates 16 which snaps over shaft 14, is likewise of a
considerable area, and extends rotationally around the axis 14' of
the shaft 14 over approximately 180.degree.. Its radially outer
edge 16', while curved, is neither circular nor coaxial with the
axis 14' the radial extent of the rotor plate 16 varying from one
end thereof to the other, this being a well-known and conventional
approach to the objective of providing, at least roughly, a desired
relationship between tuning frequency and angular rotation of the
plate 16, in this case providing for equal frequency changes for a
given degree of angular rotation from one end of the tuning range
to the other. Moreover, and again as is conventional and well
known, one or more of the outermost rotor plates 16 in a given
section - the plates that are not interposed between stator plates
12 but instead are outside one or the other of the end stator
plates 12 - is provided with a plurality of inwardly extending
notches or slots 20, thereby to divide the radially outer portion
of the plate 16 into a plurality of circumferentially separated
sections 16a-161. Each of these sections 16a-161 may be bent out of
the plane of the rotor plate 16 toward or away from the stator
plate 12 with which the rotor plate is adapted to cooperate,
thereby to trim or adjust the capacitance of the device. When the
shaft 14 is rotated clockwise as far as it will go, thus bringing
the rotor plates 16 into substantially completely overlapping
relationship with their corresponding stator plates 12, the
capacitor will be at the low frequency end of its tuning range, and
all of the sections 16a-161 will be in a capacitance-producing
relationship with the stator plates 12. As the shaft 14 is then
rotated in a counter-clockwise direction to increase the tuning
frequency, the rotor plate 16 will move to its positions shown in
FIGS. 4A, 5A and 6A and then even further in a counter-clockwise
direction, thereby progressively removing portions of the plate 16,
including selected ones of the sections 16a-161, from overlapping
or capacitance-producing relationship with the stator plates 12. In
FIG. 2 the angular locations of the slots 20 in the rotor plate 16
are indicated in terms of the degrees of rotation of the shaft 14
from its maximum clockwise position for low frequency tuning to its
maximum counterclockwise position for high frequency tuning. Thus
in one typical embodiment the slot 20 between sections 16a and 16b
will come into approximate alignment with the upper edge of the
stator plate 12 when the shaft 14 has been rotated 10 degrees from
its full counter-clockwise position, the slot 20 between sections
16b and 16c will register with the upper edge of the stator plate
12 after 23-1/2 degrees of rotation, the slot 20 between sections
16c and 16d will come into registration with the upper edge of
plate 12 after 37 degrees of rotation, and so on. FIG. 4a
illustrates a rotation of the shaft 14 of 45-1/2.degree., and it
will be seen that the slot 20 between sections 16c and 16d has
already moved above the upper edge of the plate 12, while the slot
20 between sections 16d and 16e is just beginning to move into
registration with the upper edge of the plate 12. As shown in FIG.
4A, the sections 16a, 16b and 16c no longer have any substantial
capacitance-producing effect in conjunction with the plate 12, the
sections 16e-161 are still fully in capacitance-producing
relationship with the plate 12, and the section 16b is partially in
and partially out of capacitance-producing relationship with plate
12. FIGS. 5A and 6A show the relationship between the rotor plate
16 and its corresponding stator plate 12 for rotations of
80.degree. and 130-1/2.degree. respectively, the slot 20 between
sections 16f and 16g being in substantial registration with the
upper edge of the plates 12 in FIG. 5A, while in FIG. 6A the plate
16 is shown in a position intermediate between registration of the
upper edge of the plate 12 with the slot 20 between section 16i and
16j and the slot 20 between sections 16j and 16k respectively.
Because of the cumulative capacitance-producing effect of those
sections 16a-161 which are at any point in time in overlapping and
capacitance-producing relationship with the corresponding stator
plate 12, it is not possible, as a practical matter, to adjust the
positions of the individual sections 16a-161 and achieve accurate
tracking and tuning of the circuits involved over all seventy
channels of the UHF range. Because of the physical limitations on
the size (circumferentially) of the sections 16a-161 it is not
possible to provide an individual section for each channel, and
because of the cumulative effect of those sections in producing
capacitance, even if individual sections were provided for each
channel it would still not be practical to align the various
circuits and to maintain them in alignment and to make corrections
in alignment as time went on with regards to individual channels to
be tuned.
The tuning device in compartment 6 of FIG. 1 is modified in
accordance with the present invention in order to provide for the
desired tuning and tracking accuracy. To that end an auxiliary
stator plate 22 is electrically connected to the stator plates 12,
but differs from the stator plates 12, as may clearly be seen from
FIG. 4B, in that its angular or circumferential extent is very much
smaller than that of plates 12, and, instead of extending around
the rotor shaft axis 14' by 180.degree., as is the case with the
plates 12, it has an angular extent of only about 15 degrees.
Moreover, while the standard stator plates 12 extend all the way to
the rotor shaft 14, the stator plate 22 extends only a fraction of
that distance toward the shaft 14. Fast on the rotor shaft 14, and
cooperable with the stator plate 22, is a rotor plate 24 the outer
periphery of which is divided, by slots 26, into a plurality of
sections 24a-241, each of those sections having an angular extent
of approximately 15.degree. except for section 24a, which has an
angular extent of approximately 17 1/2.degree.. Thus, as may be
clearly seen from FIG. 4B, the angular extent of each of the
sections 24a-241 is closely the same as that of the stator plate
22. It will moreover be apparent from FIG. 4B that the extent to
which the stator plate 22 extends radially inwardly toward the
shaft 14 is roughly commenserate with the radial extent of the
sections 24a-241. Consequently, as the rotor shaft 14 is rotated,
each of the sections 24a-241 will be moved into overlapping
capacitance-producing relationship with the stator plate 22 and
then moved out of that relationship. In FIG. 4B section 24d is in
capacitance-producing relation with plates 22, sections 24c and 24e
and in perhaps peripheral minor capacitance-producing relationship
therewith, and all of the other sections of plate 24 are out of
capacitance-producing relationship with the plate 22. When the
rotor shaft 14 is rotated to the position shown in FIG. 5B sections
24f and 24g are each partially in capacitance-producing
relationship with plates 22, while the other sections of the plate
24 are not, and when the rotor shaft 14 is rotated to the position
shown in FIG. 6B it is section 24j which is in
capacitance-producing relationship with plate 22, sections 24k and
24i are perhaps peripherally in that condition, and the other
sections are not in that condition.
Thus each of the sections 24a-241 produces with the stator plate 22
a certain amount of capacitance, the particular amount being
dependent upon the spacing between the plates when they overlap and
hence being adjustable by bending a corresponding section out of
the plane of the plate 24 either toward or away from the plate 22.
In a tuner designed to tune seventy channels and provided with 12
sections 24a-241 as described, each section will provide tuning
control for approximately 6 channels. The non-cumulative type of
capacitance-production derived from the plates 22 and 24, when
added to the capacitance produced by the plates 12 and 16, results
in an accurately attainable and highly reliable type of tuning.
Tuning accuracy over the entire range is further enhanced if, as is
specifically disclosed, the sections 24a-241 or rotor plate 24 are
disposed around the axis of rotation 14' of the rotor shaft 14 in a
staggered manner relative to the sections 16a-161 of the rotor
plate 16. Thus, while in a typical installation the slots 20
separating the rotor sections 16a-161 may occur at rotational
values of 10.degree., 23 1/2.degree., 37.degree., 52.degree.,
66.degree., 80.degree., 94.degree., 108.degree., 122.degree., 136
1/2.degree., and 149-1/2.degree. respectively, the slots 20
separating the sections 24a-241 may occur at rotational values of
17-1/2.degree., 31.degree., 45 1/2.degree., 59-1/2.degree.,
74.degree., 88.degree., 101 1/2.degree., 116.degree., 130
1/2.degree., 144 1/2.degree. and 159.degree. respectively. If 13 or
14 individual sections are provided instead of the twelve sections
here specifically disclosed by way of example, the actual angular
values separating the individual sections will be correspondingly
varied, but preferably without departing from the overlapping or
alternate arrangement here disclosed.
Thus, as may be seen from comparing FIGS. 4A and B, FIGS. 5A and B
and FIGS. 6A and B, when a slot 20 on one rotor blade 16 or 24 is
approximately in line with the upper edge of its corresponding
stator plate 12 or 22, the upper edge of the other stator plate 22
or 12 is located approximately between a pair of adjacent slots 20
on its corresponding rotor plate.
As has been indicated, ideally it would be preferable to provide,
on the rotor plate 24, an individual section for each channel to be
tuned but as a practical matter it is not feasable to do this with
seventy channels because individual angularly oriented sections
would be too small to be manipulatable or to reliably withstand
shock or vibration. The use of twelve to fourteen sub-sections on
the rotor plates 24 provide an acceptable degree of accuracy and
adjustability, particularly when the sections on the two
cooperating rotor plates are angularly or circumferentially
staggered. However, an even greater degree of precision and
adjustability can be obtained by using the construction shown in
FIG. 7 for the vernier tuning means. As there disclosed the size of
plate 22' is of limited angular extent relative to the rotation of
the rotor shaft 14, is located radially outside the rotor plates
16, and extends in a direction substantially parallel to that of
the rotor shaft axis 14'. The rotor 24' in FIG. 7 comprises a disc
or some like part fast on shaft 14 from the periphery of which a
plurality of finger-like sections 26 extend, those sections 26
being oriented substantially at right angles to the disc-like
portion of the rotor 24' and therefore being substantially parallel
to the plane of plates 22' and the axis 14' of the rotor shaft 14.
Because of the location and orientation of the finger-like sections
26, many more of them can be provided within a given spatial
limitation than is the case with the radially extending sections of
the embodiment previously disclosed. Individual adjustment of the
capacitance produced by each of the sections 26 relative to the
stator 22' is accomplished by bending the appropriate section 26
toward or away from plate 22'. The angular extent of plates 22'
relative to the rotor shaft axis 14' preferably will be
substantially the same as the corresponding angular extent of the
individual finger-like sections 26.
With the staggered or alternating section arrangement of the
embodiment shown in FIGS. 1-6, if the cumulatively acting rotor
plate sections 16a-161 line up with their respective stator plates
at channels 83, 77, 71, 65, 59, etc., then the sections 24a-241 on
the rotor plate 24 will line up with their respective stator plates
22 at channels 80, 74, 68, 62, etc., thus effectively providing an
alignment every three channels and permitting positive, accurate
and smooth alignment of the complete band according to a prescribed
procedure without the need for a continual touch-up adjustment as
would be required if a cumulatively acting system alone were used.
The addition of the non-cumulatively-acting tuning portion acts to
correct residual error in the cumulatively-acting portion and makes
for easier adjustment of the cumulatively-acting portion itself.
Through the use of the present invention alignment accuracies are
achieved which are three times greater than what could be obtained
formerly by the cumulative-acting system alone.
It will be understood that the tuning arrangement here disclosed
can be used whether or not the normal variable capacitor tuning
means is provided with adjustable sections such as the sections
16a-161 or not, particularly if the vernier tuning means of FIG. 7
is employed where a large number of individual adjusting sections
may be provided. While but a limited number of embodiments of the
present invention have been here specifically disclosed, it will be
apparent that many variations may be made therein, all within the
scope of the instant invention as defined in the following
claims.
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