U.S. patent number 3,902,177 [Application Number 05/338,419] was granted by the patent office on 1975-08-26 for antenna for direction finders.
This patent grant is currently assigned to Taiyo Musen Co., Ltd.. Invention is credited to Norio Ikeda, Yujiro Katsube, Kenzo Mori, Hyo Yasuda.
United States Patent |
3,902,177 |
Mori , et al. |
August 26, 1975 |
Antenna for direction finders
Abstract
This invention relates to an antenna for direction finders
presenting a high sensitivity in a narrow band by making a loop
antenna and a shielding tube resonate at any two desired
frequencies.
Inventors: |
Mori; Kenzo (Tokyo,
JA), Yasuda; Hyo (Tokyo, JA), Katsube;
Yujiro (Tokyo, JA), Ikeda; Norio (Ichikawa,
JA) |
Assignee: |
Taiyo Musen Co., Ltd. (Tokyo,
JA)
|
Family
ID: |
14076380 |
Appl.
No.: |
05/338,419 |
Filed: |
March 6, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Sep 19, 1972 [JA] |
|
|
47-93217 |
|
Current U.S.
Class: |
343/741; 343/842;
343/748; 343/846 |
Current CPC
Class: |
H01Q
5/378 (20150115); H01Q 7/04 (20130101) |
Current International
Class: |
H01Q
7/04 (20060101); H01Q 5/00 (20060101); H01Q
7/00 (20060101); H01q 007/04 (); H01q 011/12 () |
Field of
Search: |
;343/748,741-744,764,841-842,866-869 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lawrence; James W.
Assistant Examiner: Nussbaum; Marvin
Attorney, Agent or Firm: Breiner; A. W.
Claims
What is claimed is:
1. An antenna for direction finders comprising a first conductor
forming a loop antenna having opposite ends, an auxiliary conductor
having a cut at the top thereof arranged near and in parallel with
said first conductor, first capacitor means connected between both
ends of said loop antenna for providing a resonant circuit with
said loop antenna which is resonant at a first frequency and second
capacitor means connected between both ends of said cut of said
auxiliary conductor at the top part of said antenna for providing a
resonant circuit with said auxiliary conductor which is resonant at
a second frequency higher than said first frequency, the values of
inductance of said auxiliary conductor and of capacitance of said
second capacitor means being selected with respect to the values of
inductance of said loop antenna and of capacitance of said first
capacitor means so that at a third frequency higher than said
second frequency the combination of said auxiliary conductor and
second capacitor means provides inductive impedance of such value
as to cooperate with said first capacitor means and cause said loop
antenna to be resonant at said third frequency permitting a high
sensitivity in each narrow band of said first and third
frequencies.
2. An antenna according to claim 1 wherein said auxiliary conductor
is a shielding tube.
3. An antenna according to claim 1 wherein said loop antenna is
formed to be tubular and said auxiliary conductor is coaxially
arranged within this tubular conductor so that the sensitivity at
said first frequency is increased.
Description
This invention relates to antennas for direction finders.
Loop antennas are generally used as directional antennas for
direction finders. It is the general practice to fit such loop
antenna with a shielding tube. However, conventional antennas of
this kind have a high sensitivity only at a comparatively low
frequency. Further, by inserting a condenser between both ends of a
loop antenna and making its electrostatic capacitance and the
inductance of the antenna resonate with each other, the sensitivity
can be increased near the resonating frequency.
An object of the present invention is to provide an antenna for
direction finders wherein a suitable electrostatic capacitance is
formed also between both ends of another auxiliary conductor
arranged near and in parallel with a conductor forming a loop
antenna as in the above mentioned shielding tube and said
electrostatic capacitance and the inductance of the auxiliary
conductor are made to resonate with each other so that a high
sensitivity may be again presented at any desired frequency higher
than the above mentioned resonating frequency.
The drawing is a view showing a wiring of an embodiment of the
present invention.
In the drawing, a conductor forming a loop antenna 1 is fitted with
a shielding tube 2 provided with a cut 3 in the top part. A proper
insulator 4 is inserted between the inside surface of the shielding
tube 2 and the antenna 1. A condenser 5 is inserted between both
ends of such loop antenna 1 and a condenser 6 is connected also
between both ends of the cut 3 of the shielding tube 2 so as to
respectively form proper electrostatic capacitances. Both terminals
7 and 8 of the loop antenna 1 can be connected with a cable 10
through a transformer. Further, a resistance 11 connects to the
secondary side or primary side of the transformer 9. In a direction
finder, such two loop antennas as are described above are so
arranged as to intersect at right angles with each other and are
led to a goniometer or the like through respective cables. Further,
the shielding tube 2 can be used not only as directly grounded but
also without being grounded.
As described above, in the present invention, suitable
electrostatic capacitances 6 and 5 are connected respectively in a
cut in the top part, for example, of a shielding tube arranged near
and in parallel with a conductor forming a loop antenna and between
both ends of the loop antenna. The inductance of the loop antenna 1
and the electrostatic capacitance 5 between both ends of the loop
antenna are resonated with each other at any desired first
frequency and the inductance of the shielding tube 2 and the
electrostatic capacitance 6 between both ends of the shielding tube
are resonated with each other at any higher suitable second
frequency so that all members 1 through 9 may resonate at a still
higher third frequency. Therefore, for arriving electric waves of
such low frequency at which the condenser 5 inserted between both
ends of the loop antenna presents an impedance high enough, the
antenna will have the same sensitivity as of a conventional loop
antenna of this kind and the impedance as seen from the terminals 7
and 8 will show an inductivity. When the frequency of the electric
waves increases to a value of said first frequency and the
electrostatic capacitance of the condenser 5 and the inductance of
the above mentioned loop antenna resonate in parallel with each
other, the impedance as seen toward the antenna side from the
terminals 7 and 8 will become so high that the sensitivity will
quickly rise. When the frequency increases to be so high as to
exceed the above mentioned resonating point, the impedance will
vary to be capacitive from being inductive. However, if the
frequency of the arriving waves further increases to a third
frequency which is higher than said second frequency at which the
electrostatic capacitance by the condenser 6 or the like and the
inductance of the shielding tube 2 resonate with each other, the
impedance as seen from the terminals 7 and 8 will vary again to be
inductive and will resonate with the condenser 5, therefore a large
electric current will be induced in said antenna 1 and the
receiving sensitivity will increase again. Therefore, when the
diameter of the loop antenna 1, thickness of the shielding tube 2,
material of the insulator 4 and capacitances of the condensers 5
and 6 are properly selected in the design so that the loop antenna
1 and the shielding tube 2 may respectively resonate with each
other at two desired frequencies, there will be obtained an antenna
for direction finders having a high sensitivity at the above
mentioned first and third frequencies.
In the above has been explained an embodiment wherein the shielding
tube is utilized as an auxiliary conductor. In order to increase
the sensitivity at the lower frequency by reducing the inductance
of a loop antenna, it is necessary to enlarge the diameter of the
conductor. Therefore, in such case, the loop antenna may be formed
of a tubular conductor and an auxiliary conductor may be coaxially
arranged within said tubular conductor.
* * * * *