U.S. patent number 3,916,413 [Application Number 05/427,259] was granted by the patent office on 1975-10-28 for remotely tuned conductive-body antenna system.
Invention is credited to Ross Alan Davis.
United States Patent |
3,916,413 |
Davis |
October 28, 1975 |
Remotely tuned conductive-body antenna system
Abstract
An improved remotely tuned conductive-body antenna system is
provided which gives superior signal coupling between the low
impedance conductive body and the associated radio-frequency
circuits with minimum loss of selectivity or "Q" in those circuits
by increasing the inductive reactance of the coupling means insofar
as the associated radio-frequency circuits are concerned without
mis-matching the input to the coupling means and the low impedance
conductive-body signal source.
Inventors: |
Davis; Ross Alan (Honolulu,
HI) |
Family
ID: |
23694133 |
Appl.
No.: |
05/427,259 |
Filed: |
December 21, 1973 |
Current U.S.
Class: |
343/712;
343/856 |
Current CPC
Class: |
H01Q
1/1271 (20130101) |
Current International
Class: |
H01Q
1/12 (20060101); H01Q 001/32 () |
Field of
Search: |
;343/711,712,713,856 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lieberman; Eli
Attorney, Agent or Firm: Birchard; Bruce L.
Claims
What is claimed is:
1. A vehicle body antenna system, including:
a windshield opening having a conductive perimeter and being
responsive to a radio frequency field to produce at points across
the perimeter a potential at said radio-frequency;
radio frequency circuits remote from said discontinuity and forming
a part of associated radio apparatus;
coupling means including a secondary winding directly connected to
at-least-one point of the conductive perimeter and juxtaposed to
at-least-one portion thereof to form therewith a transformer with a
single turn primary; and,
tuning means coupled to said transformer and physically positioned
remote from said discontinuity and proximate to said radio
frequency circuits.
2. Apparatus according to claim 1 in which said secondary winding
is connected at its other end to a capacitor which, in turn, is
connected to a point on said conductive perimeter opposite said
at-least-one point.
3. Apparatus according to claim 2 in which the magnitude of said
capacitor is in the order of 0.01 microfarads.
4. Apparatus according to claim 1 in which said secondary winding
comprises first and second sections each having a winding direction
opposite from the other section and each section juxtaposed to a
different portion of said conductive perimeter from said other
section.
5. Apparatus according to claim 1 in which said radio frequency
circuits includes tuning apparatus, said tuning apparatus being
mechanically coupled to said tuning means.
Description
RELEVANT COPENDING APPLICATIONS
Application Ser. No. 427,258, filed Dec. 21, 1973, now abandoned,
by this inventor and entitled Antenna System Utilizing Currents in
Conductive Body. Application Ser. No. 430,095 filed Jan. 2, 1974,
by this inventor and entitled Improved Radio Frequency
Transformer.
BACKGROUND OF THE INVENTION
In U.S. Pat. Nos. 2,923,813; 2,971,191; 3,007,164 and 3,066,293 the
present inventor described several approaches to utilizing as
antennas conductive structures such as automobile bodies. Because
of the very unusual characteristics and extremely difficult
problems encountered in extracting usable R.F. signals from
existing conductive structures, the state of the art has developed
only gradually through the years. This has been particularly true
for the extraction from conductive structures, such as car bodies,
of signals at lower frequencies in the region of the AM broadcast
band. New and unique techniques have been required to extract a
maximum of these elusive signals (corresponding to the magnetic
component of incident electromagnetic fields) from existing
discontinuities and particularly from the limited discontinuities
formed in the fabrication of car bodies. Until recently, the art,
even that developed by this inventor, could not properly meet this
challenge.
To fully appreciate the many steps of painstaking progress and the
many trials and errors involved in achieving the advancements in
the art represented by the invention shown and claimed herein, it
is desirable to trace the problems faced with the systems described
in those patents and how those problems were solved.
As is well known, radiated electromagnetic signals comprise two
components, the electrical component and the magnetic component.
The signal component relied upon in the operation of the subject
invention is the magnetic component, as it was in the
earlier-issued patents. The impedance looking into a discontinuity
in an existing conductive structure at radio broadcast frequencies
is extremely low when such a conductive structure is that of a car
body, the inductance being the major part of that impedance with an
average maximum of only 2 micro-henries. Because of the relatively
high impedance of the input circuits of the radio apparatus coupled
to the discontinuity in the conductive body it was considered
impracticable, (prior to the work of the inventor), to couple radio
broadcast signal energy efficiently out of a conductive body into
associated radio apparatus, as for example, into an associated
radio receiver.
To help solve this problem this inventor conceived and successfully
reduced to practice a unique voltage and impedance transformer
usable at radio frequencies and comprising a one-turn conductive
sheath or tube acting as the primary of an auto-transformer, the
secondary being formed by a conductor passing through the inner
opening of the sheath or tube 8 or 9 times (when used at AM
broadcast frequencies) and, hence, being very tightly magnetically
coupled to the single turn primary of the auto-transformer. This
unique design reduces unwanted electrostatic signals and noise in
the transformation process. Further reduction of noise can be
achieved by using a double-walled sheath, the inner wall providing
electrostatic-shielding, as described hereinafter. To further
improve the coupling between the single-turn primary and its
secondary and to increase the inductance of the single-turn primary
to a level such that it matches the inductance of the discontinuity
in the conductive body, and, also, to further shield the
transformer from extraneous electrical signals, a series of
ferrite, high-permeability beads is applied so that it covers
completely the one-turn primary sheath or tubing.
To simplify the discussion which follows, reference will be made
frequently to a car body as the conductive body which acts as the
antenna for this system. It should be understood that any
conductive body, stationary or mobile, having an electrical
discontinuity therein either solely for the purpose of this system
or performing other functions as well, may be used in this system.
In a car body, in addition to desired signals there are many
undesired noise signals produced by the ignition system and various
other electrical equipment found in cars today. These noise signals
are in common conductive paths with the desired signals. Those
noise signals have, in a majority of cases, a large electrostatic
component and, in early systems designed by this inventor, the
interference they produced made acceptable reception of desired
signals most difficult without extreme diligence in isolating and
eliminating the noise signals from the desired signal currents in
the common conductive structure. One method for raising the level
of the desired signals with respect to the undesired, or noise
signals (beyond that accomplished by the use of the R.F.
auto-transformer described herein), is to resonate to the
desired-signal frequency the signal source (the conductive body),
as is shown and described in co-pending application Ser. No.
427,258, filed Dec. 21, 1973, by this inventor. A second method is
to tune the secondary of the auto-transformer to the frequency of
the desired signal. In both cases the inductance is very low and
the size of the capacitor required to resonate the inductances at
broadcast radio frequencies is very large and the range of
capacitance variation required to tune across the broadcast band is
very large (9 to 1) making the use of conventional variable
capacitors generally impracticable. This inventor then devised a
system utilizing banks of small capacitors switched in or out in
single step fashion through a multi-fingered sliding contact device
which was ganged to the variable inductance or "slug" tuner in the
radio and maintained the approximate value required for resonance
of the associated inductance. Unfortunately, the number of
switching contacts required was excessive in parallel resonating
the auto-transformer secondary and the switching noise produced in
the radio input circuits was a problem that required regular
service to maintain quiet operation of this tuner. As a result, in
the early systems, fixed tuning was the only available solution and
it provided less than optimum performance. Further work by this
inventor resulted in the development of a simplified, variable,
series-resonant tuner that was used in the tuning of the
low-impedance primary of the auto-transformer to achieve maximum
coupling of energy from a conductive body discontinuity into
associated radio apparatus. With this series capacity tuning, step
switching was usable because of the low impedance in the primary.
Switching noise was not objectionable even in high-gain car radio
input circuits adapted for use with the subject car body antenna
system. However, such tuning of the low-impedance primary, by
itself, left much to be desired both in selectivity and signal
voltage gain. Signal voltage gain is particularly important when
the source is a low impedance conductive-body discontinuity, as it
is in this case. Attempts to increase the voltage gain in the
auto-transformer by conventional means, such as by loosening the
primary-secondary coupling (to reduce inherent inter-winding
capacitance) and increasing the number of primary and secondary
turns were not entirely acceptable. Further development work by
this inventor was necessary to achieve the required voltage gain
and "Q" in the circuits (and a better L/C ratio, particularly in
the low impedance input transformer used to further isolate
troublesome noise problems); and, finally, to permit a more
simplified tuning of the antenna system remotely, as from the radio
receiver in the car, simultaneously with the tuning of that
receiver, all without adversely affecting voltage gain and signal
selectivity in the receiver.
This inventor then hit upon the idea of connecting the secondary
tuning condenser in the electrical center of the secondary winding
of the auto-transformer with its tightly coupled, low-impedance
primary and higher impedance secondary. By locating the secondary
tuning condenser in the electrical center of the secondary,
(whether that secondary is lumped in the matching transformer or
distributed along the border of a discontinuity), the effective
distributed capacity of the secondary is reduced sharply and the
number of turns on that secondary may be increased for a given
desired frequency of operation, thus permitting greater voltage
gain in the transformer and permitting the remote location of the
secondary-tuning capacitor through extended shielded cables. It
should be noted that in the lumped auto-transformer the secondary
is contained within (and is electrostatically shielded by) the
single turn tubular primary. An additional tube or sheath may be
provided for electrostatic shielding. Further, the primary is
encased with ferrite material to produce a primary inductance which
is matched to the source of signal; viz., the conductive body
discontinuity, so that maximum signal current flow may be produced
in the single turn primary. (The full voltage available from the
discontinuity is applied across this one-turn primary).
To further advance and simplify this body (magnetic) signal
technique and at the same time make it fully adaptable to today's
standard high impedance car radio inputs (with a minimum of
required changed and increased costs), a very practical combination
of car body magnetic signals and electrostatic signals from a
conventional antenna has been made. This combination simplifies
adapting this inventor's car-body signal techniques to use with
standard radio receiver input circuits. This combination further
reduces the need for dual magnetic signal input to the associated
radio receiver so that a single conductive-body-signal input may be
used when properly combined with a high impedance electrostatic
antenna input. Also additional performance features have been
gained over both the electrostatic and magnetic systems, which are
not available from either separately. This added signal input can
be derived from the simple addition of an insulated fine wire
antenna imbedded in the windshield (or rear window) as is currently
being done in both American made and American imported cars. The
magnetic conductive-body signal may be derived by magnetic
induction from the perimeter of the same windshield or rear window
to reduce costs and simplify manufacture. Or, as described in
patent application Ser. No. 427,258 of this inventor, the car-body
magnetic signal may be taken from a structural element adjacent the
windshield or rear window. One of the unusual assets gained in this
combination of electromagnetic and electrostatic signals is that
further noise reduction can be achieved when R. F. noise from the
two sources is properly phased and balanced as shown and described
herein. Further greater extended signal range can be now
accomplished by this combination, thus increasing the
practicability of the insulated windshield wire antenna which is
known for its limited ability to function in poor signal areas. The
electrostatic antenna also suffers from sharp signal attenuation in
structural, overpass and mountainous areas. To further enhance this
combination of signal sources, a functional switch can be added to
allow switching in either system separately or in combination. This
switching capability is also useful in demonstrating the superior
performance of the car-body antenna with respect to the insulated
wire electrostatic antenna in varied situations.
Another method for improving the coupling of the signal from the
body source to the relatively high impedance receiver input
circuits is the double-ended driving of the extended primary of a
transformer having a correspondingly larger secondary winding, as
described hereinafter.
It should be noted that the antenna system described herein may be
used equally well in the transmitting mode as in the receiving
mode.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a representation, partially as an elevational view and
partially as a schematic diagram of an antenna system according to
the present invention;
FIG. 2A is a representation, partially in elevation and partially
in schematic form of a second antenna system incorporating the
present invention;
FIG. 2B is a schematic representation of a variation in the antenna
system of FIG. 2A;
FIG. 3A is a representation, partially in elevation and partially
in schematic form of a third form of antenna system incorporating
the present invention;
FIG. 3B is a schematic diagram of a variation of the antenna system
of FIG. 3A;
FIG. 4A is a schematic diagram of an additional variation of an
antenna system according to the present invention;
FIG. 4B is a circuit diagram showing variation of the antenna
system of FIG. 4A;
FIG. 5 is a diagram, partially in schematic form, of an antenna
system for deriving dual tuned signals from a single
discontinuity;
FIG. 6 is a partially schematic diagram of an antenna system
according to the present invention utilizing existing functional
elements of an automobile for disguising the antenna coupling
element;
FIG. 7A is a schematic diagram of a first doubleended primary drive
for the transformer in an antenna system according to the present
invention;
FIG. 7B is a schematic diagram of a variation in the coupling
system utilized in FIG. 7A;
FIG. 8 is a schematic diagram of a transformerless double-ended
signal coupling circuit according to the present invention; and
FIG. 9 is a schematic diagram of a dual source coupling system
according to the present invention.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
In FIG. 1 conductive body 10 has opening 11, therein. For purposes
of convenience body 10 is shown as a car body and opening 11 may be
a front or a rear window therein. Opening 11 is bounded by
conductive edge 12 along which radio-frequency currents flow when
body 10 is exposed to a radio-frequency energy field. As a result
of such current flow a radio-frequency potential difference exists
between points 13 and 14 along edge 12. Further, because of the
close proximity of conductors 15, 16, 17 and 18 to edge 12 (they
may actually be hidden under the trim which normally covers edge 12
for aesthetic purposes) that portion of edge 12 between points 14
and 13 on the side proximate to conductors 15, 16, 17 and 18 is
inductively coupled to those conductors and may be considered,
along with exciter lead 19, to be the primary of an
auto-transformer of which conductors 15, 16, 17 and 18 constitute
the secondary. This secondary is tapped by means of conductors 20
and 21 more or less at its center point. The tapping point may vary
from the exact center point without departing from the essence of
this invention. As conductors 20 and 21 emerge from shielding
sheath 22 they are coupled across variable condenser 23. Variable
condenser 23 may be ganged with main variable inductance or slug
tuner 25 which is shunted by trimmer 24. Slug tuner 25, has coupled
thereto winding 26 which transfers energy to or from associated
electrical circuits for receiving or transmitting radio-frequency
signals. Coupling condenser 27 may, by reason of the central tuning
of the secondary comprising conductors 15, 16, 17 and 18, be from
20 to 100 pico-farads without destroying the selectivity of the
tuned circuit comprising condenser 24 and inductor 25.
Padding condenser 29, which may be of a magnitude of 0.01
micro-farads is coupled between end terminal 30 of the
autotransformer made up of conductors 15 through 18, and edge 12 in
the region of point 14. The relative capacitance of padding
condenser 29 and coupling condenser 27 determines the portion of
the total signal voltage introduced into slug tuner 25. In addition
to the signal picked up from the R. F. currents flowing in edge 12,
a separate sense antenna 31 may be provided. This is essentially an
electrostatic pick-up device which may be embedded in the glass
placed in opening 11. The signal from this antenna is carried by
conductor 32 to terminal 33 of a two-pole triple-throw selector
switch including fixed contacts 33, 34, 35, 36, 37 and 38 and
movable contacts 39 and 40. With the selector switch in the
position shown both the car body signal and the sense-antenna
signal are fed through noise filter choke 40' to the radio receiver
input tuned circuit. With the selector switch moved to the left in
FIG. 1, i.e., with movable contact 39 connected to fixed contact 35
and movable contact 40 cooperating with fixed contact 36, only the
car body signal is coupled to the receiver input circuit. With the
selector switch moved to the right, i.e., with movable contact 39
connected to fixed contact 33 and movable contact 40 connected to
fixed contact 38, only sense-antenna 31 is in use. In some
situations the combination of the signals from the sense antenna
and the car body gives optimum results. Sometimes the best signal
is derived from the car body alone. Occasionally it may be
desirable to use the sense antenna alone. The switching system of
FIG. 1 permits the selection of optimum signal strength.
The size of the wire used for conductors 15 through 19 can be
varied between 18 and 40 gauge with the criteria being minimal
obstruction of vision through opening 11 and minimum resistance in
the secondary comprising conductors 15 through 18
In FIG. 2A the secondary of the auto-transformer is disposed in
both halves of opening 11. Conductor 200, in combination with edge
portions 201, 202 and 203, constitutes the primary of a first half
of the secondary comprising conductors 207 and 208, and conductor
200, in combination with edge portions 204, 205 and 206,
constitutes the primary of a second half of the secondary
comprising conductors 209 and 210. The method for tuning the
inductance appearing between center-tap conductors 211 and 212 and
for coupling into and out of associated radio apparatus is the same
as that described in connection with conductors 20 and 21 of FIG.
1, and need not be repeated here. Early experiments have indicated
that the secondary disposition described in connection with FIG. 2A
may reduce noise signals arising from local sources, such as the
automobile ignition system. Sense antenna 213 is provided for the
same purpose and with the same results described for sense antenna
31 in FIG. 1. It is coupled through conductor 214 to a selector
switch comprising fixed contacts 215 through 220 and movable
contacts 221 and 222. This selector switch performs the same
function as the selector switch of FIG. 1.
In FIG. 2B the extraction of desired magnetic signals from the car
body is accomplished by means of inductive coupling from edge
portions 230 through 233, which constitute the primary of a
transformer, of which conductors 234, 235, 236 and 237 constitute
the secondary. This combination differs from the structure of FIG.
2A in that there is no direct connection to the boundary of the
discontinuity 238. The advantage of this configuration is that the
conductive noise currents which might be mixed with signal currents
in the body and are conductively isolated from the radio input
circuits, because only inductive coupling transfers signals from
the primary to the secondary. A single ground point for the input
circuits further limits and conductively isolates these troublesome
noise currents. The secondary is balanced as in FIG. 2A, and
similarly has a figure-eight configuration. Central tuning of the
secondary is accomplished, remotely, in the fashion described in
connection with the antenna system of FIG. 2A utilizing condenser
239 coupled through conductors 240 and 241 to the R. F. transformer
secondary made up of conductors 233 through 237. The leads to the
remote circuits are shielded from noise pick-up by conductive
sheath 241'. Sense antenna 242 may be provided and functions as
described in connection with FIG. 2A.
In FIG. 3A the secondary tuning concept of this invention is shown
applied to an antenna system of the type disclosed in co-pending
application Ser. No. 427,258 entitled Antenna System Utilizing
Currents in Conductive Body and filed by this inventor on Dec. 21,
1973.
In FIG. 3B, column 300 in a conductive body has an impedance
discontinuity therein produced by severing the column, using
ferrite in and around the column or increasing its resistance in a
region, resulting in the appearance of an electrical potential
across points 301 and 302. Sheath 303, of copper or other
conductive material is connected at its extremes 304 and 305 to
points 301 and 302, respectively, and acts as the primary of an
auto-transformer for which conductors 306 and 307 form the
secondary. The secondary is split at points 308 and 309 and is
coupled by means of connectors 310 and 311 to tuning condenser 312
which may be ganged with variable inductance 315. Inductance 315,
in turn, is shunted by trimmer 313. This coupling network functions
in the same fashion as that described in connection with FIG. 1 and
need not be described further here.
Ferrite material 314 may be applied to sheath 303 to provide
magnetic shielding and to increase the coupling of the primary and
secondary portions of the auto-transformer. Sheath 303, its ferrite
covering 314 and the conductors 306 and 307 may be made
aesthetically more attractive by incorporating them in a mirror,
for example, mounted on column 300, taking care not to short
circuit the desired impedance discontinuity in column 300.
In FIG. 3B auto-transformer 320 is located remotely from the
discontinuity in the conductive body but is coupled thereto by
coaxial cable 321 having central conductor 322 and conductive
sheath 323. Central conductor 322 is connected to point 324 and
conductive sheath 323 is connected to point 325 on opposite sides
of discontinuity 326 in column 300. Thus, the full R.F. potential
appearing between points 324 and 325 is applied across coaxial
cable 321. While a coaxial cable has been found to perform best in
this coupling directly to the low impedance signal source, strictly
speaking a coaxial cable is not required but merely an internal
conductor insulated from an outer conductive sheath may be used
when of good design for R. F. energy transfer. The outer sheath, in
either case minimizes noise signal pickup from surrounding noise
sources when correctly grounded at both ends.
In FIG. 3B, auto-transformer 320 functions as does the
auto-transformer described in connection with FIG. 3A. However, it
is often inconvenient to mount the auto-transformer at the body
discontinuity. This inventor has found, surprisingly, that the
remote location of auto-transformer 320 not only performs an
effective impedance and voltage transformation but also produces a
significant noise reduction by reason of the shielding and
electrostatic isolating effect of outer tubing or sheath 327 which
also constitutes the one-turn primary of auto-transformer 320. The
remote location of transformer 320 also allows conductive isolation
from undesirable noise currents flowing with the desired signal
currents in the conductive structure. Additional shielding sheath
or tube 328 provides further noise suppression by isolating the
primary and secondary portions of transformer 320,
electrostatically, from each other. This system has proven in tests
to be very effective in cars with high levels of locally generated
noise. The remainder of the circuit of FIG. 3B operates in the same
fashion as the circuit of FIG. 3A.
In FIG. 4A the signal potential produced between points 401 and 402
on opposite sides of discontinuity 403 in column 404 is applied to
conductors 405 and 406 of coaxial cable 407. Sheath 406 is grounded
at the receiver end, as shown. Center conductor 405 is coupled
through series tuning condenser 408 to primary coil 409 of input
transformer 410, the secondary 411 of which is core or slug tuned.
Condenser 408 and the movable core which tunes secondary 411 may be
ganged. Noise transfer from primary 409 to secondary 411 is
prevented by electrostatic shield 412. Inherently however, because
of the low impedance of the network including coaxial cable 407 and
primary 409, little noise is picked up in that network.
In FIG. 4B, signals appearing across points 401 and 402 are coupled
to primary 409 through a balanced system as contrasted with the
unbalanced system of FIG. 4A. Conductive shield 413, which is
grounded at the receiver end as shown, prevents noise pickup in the
coupling between the signal source and the receiver primary 409.
Series condenser 408 series resonates the circuit including primary
409, as described in connection with FIG. 4A. Electrostatic shield
414 reduces noise coupling between primary 409 and secondary
411.
In FIG. 5, two signals having differing directional characteristics
are derived from a single discontinuity in a car body and remote
tuning of the dual antenna system is provided.
Conductive sheath 500 is connected to the boundary of the opening
at points 501 and 502 and, as described in connection with earlier
embodiments, constitutes the primary of an auto-transformer, the
secondary of which comprises conductors 503, 504 and 505 and 506
which pass through the primary and are tightly coupled thereto. In
some applications the car body trim itself may act as the primary
of the auto-transformer and the conductors may pass through that
trim. The conductors pass diagonally across opening 507 in
returning for passage through the primary. The size of the wires is
such that they do not obstruct vision through the opening, which
may be the rear window. The secondary is center-tapped and the
leads come out at conductors 508 and 509 to permit center tuning of
the secondary of the auto-transformer by condenser 510. Padding
condenser 511 is coupled between low-impedance antenna output lead
512 and ground. Conductor 512 is coupled to the receiver input
circuits.
Similarly, signals are picked up between points 513 and 514 along
the boundary of discontinuity 507 and are transformed in voltage,
upwardly, by the auto-transformer action of primary 515 and
secondary conductors 516 through 519 passing through the
primary.
Output signals are taken from conductor 519, as shown. The
secondary of this auto-transformer is tuned at its center by
condenser 520 which is remote, as at the radio receiver, and may be
ganged with the main tuning device of the radio receiver.
It should be noted that the car body surrounding the discontinuity
507 acts as a shield for this antenna system against many
electrostatic noise signals.
In FIG. 6 the concepts set forth in connection with FIGS. 1 through
5 are embodied in an otherwise functional portion of the car body.
In the disclosed embodiment the primary 600 of the auto-transformer
bounds a portion of the perimeter wind-wing assembly 601 and may be
a hollow conductive sheath or tube through which the secondary
windings 605, 606 and 607 pass. The potential difference between
points 602 and 603 on the car body edge 604 is used to drive this
longer portion of this low impedance primary. The secondary of the
auto-transformer is tuned remotely by condenser 606 which may be
ganged with the receiver main tuner 617. Instead of incorporating
the auto-transformer in the wind-wing assembly it may be
incorporated in a rear-view mirror mounted between conductive body
driving points 602 and 603, with the balance of this primary being
used to support the external mirror.
The structure shown and described in FIG. 6 may be duplicated on
the opposite side of the vehicle to obtain multi-directional
signals and provide nearly omni-directional reception. Switching,
automatic or manual, may be provided, as shown using fixed contacts
607', 608, 609 and 610 and movable contacts 611 and 612. Energy
from the second auto-transformer, not shown, is brought to the
switch through coaxial cable 613. Condensers 614 and 615 are
coupling condensers bringing signals to the receiver input
circuits. Condensers 614' and 615' act as padding condensers to
apply the optimum signal to the receiver input circuits including
trimmer condenser 616 and core tuned inductance 617.
In FIG. 7A oppositely phased signal voltages appearing at points 70
and 71 on column 72 are fed to opposite extremities 73 and 74 of
conductive sheath or tube 75 which acts as the primary of an
impedance and voltage step-up transformer 76 through which a
secondary terminating in leads 77 and 78 passes. Because primary 75
is being driven in push-pull fashion with its center grounded its
length may be doubled for better matching of the impedance of the
source and, at the same time, greater signal step-up may be
realized in the secondary. Ferrite beads 79, which surround sheath
75 assure increased primary-secondary coupling and permit direct
parallel tuning of the secondary of transformer 76 by condenser 80
which is ganged with receiver input circuit tuning inductor 81.
Signals are injected at the high potential end of that inductor
through coupling condenser 82 which may have a capacitance of 10
pico-farads. Input to the first receiver translating element is
through secondary 83.
In FIG. 7B push-pull (or double-ended) driving of primary 84
occurs, as with primary 75 in FIG. 7A. However, the method of
coupling signals from the secondary winding of step-up transformer
85 through leads 86 and 87 to associated radio apparatus is
different from the method in FIG. 7A. Series tuning of the cicuit
including the secondary of transformer 85 and coupling inductances
88 and 89 is accomplished by capacitance 90 which is ganged with
input tuning inductor 91 to assure optimum performance of the
antenna system at each setting of the tuner in the associated radio
apparatus. Again, the antenna tuning element is located remotely
from the conductive-body signal source.
In FIG. 7B the signal source is shown as being points 92 and 93 on
column 94 in which there is a discontinuity. A second signal may be
derived from a second source, not shown and supplied through cables
95 and 96, to which terminals 97 and 98 of primary 84 may be
appropriately switched.
In FIG. 8 signals may be derived alternately from points 800, 801
and 802, 803, respectively, by operation of slide switch 804. This
is a balanced system with remote tuning of the antenna system
accomplished by series condenser 805 which may be ganged with
variable inductance 806. Coils 807 and 808 may be wound in layers,
one on the other and connected in aiding fashion. Their self and
mutual inductance may be increased by using a ferrite core. In
fact, it is possible to design the tuning core for inductance 806
so that it has a portion always within coils 807 and 808 despite
the controlled entrance of that core into inductor 806 for tuning
purposes.
In FIG. 9, signals may be coupled into and out of discontinuities
900 and 901 which may be between the header 908 and body 909 of an
automobile. Omni-directionality in transmission and reception may
be approached by proper coupling of energy into and out of the
conductive body through cables 902 and 903. Tuning of the
combination of the body inductance and primary inductance 904 to a
desired frequency is accomplished by capacitance 905, which may be
ganged with variable tuning inductance 906 in associated radio
apparatus. Signals into and out of the system may be taken through
coupling coil 907. This circuit has been used very successfully at
27 magaherz.
While specific embodiments have been described, modifications may
be made within the scope of the invention. The following claims are
intended to cover such embodiments.
* * * * *