Device for two-way information link

This invention relates to a device for a two-way information link, where a first one of two units or both units are intended to transmit an interrogation signal to the second unit, and the second unit is capable to transmit a response to the first unit.

BACKGROUND OF THE INVENTION 
It is previously known to arrange two units in the aforedescribed way. In 
known systems, however, transmitter and receiver are separated when they 
are tuned on the same frequency. When transmitter and receiver are 
assembled and have one aerial in common, the transmitter and receiver are 
tuned on different frequencies. Known devices for a two-way information 
link have in common, that they are relatively complicated. 
SUMMARY OF THE INVENTION 
The present invention offers a very simple device for a two-way information 
link which comprises at least two units, each of which includes a 
transmitter and a receiver, and each unit is capable to transmit and 
receive information. 
The invention is characterized thereby, that each unit is capable to 
transmit and receive, respectively, waves of mutually substantially equal 
frequency which are orthogonal relative to each other, and each unit is so 
arranged that at transmitting and receiving, respectively, said waves the 
transmitting element and the receiving element do not affect each other.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 a recording unit 1 is shown, which is assumed to be the 
interrogating unit, and a recording emitter 2, which is assumed to be the 
responding unit. In many cases, however, it is advantageous to design said 
two units identical or almost identical in order to obtain a two-way 
information flow of all kind occurring in the system. 
The recording unit 1 comprises an aerial 3a, a transmitter and receiver 4a, 
a decoding device 5a and a device for e.g. storing, print-recording or 
transmitting the result to a central unit. A starting device 7 is provided 
for starting the transmitter 4a automatically or manually. The recording 
emitter 2 also comprises an aerial 3b and a transmitter and receiver 4b, 
which are identical with the aerial 3a and the transmitter and receiver 4a 
of the recording unit 1. The recording emitter further comprises a 
decoding device 5b of the same kind as comprised in the recording unit 1. 
A coding device 8 is provided in the recording emitter 2 and capable to 
generate a coded signal to be transmitted from the transmitter 4b, in 
which signal the code is the information, which the recording emitter 2 is 
intended to emit. This information, of course, may be of a very great 
variety of types, depending on the connection in which the two-way 
information link is used. An information unit 9 is connected to the coding 
device 8 and contains the value or values, digits etc. to be transferred 
to the recording unit 1 upon an interrogation therefrom. The information 
unit 9, thus, is capable to control the coding device so that the coding 
device codes a signal in agreement with the information to be transmitted. 
The recording unit and the recording emitter operate briefly as follows. 
The starting device 7 sends an impulse to the transmitter 4a to transmit a 
signal via the aerial 3a. The transmitter 4a hereby generates an 
interrogation signal of a fixed frequency. This signal either may be 
continuous or consist of a pulse train 10 of such a shape that the signal 
is coded by having on-off character, and the code of the signal expresses 
which information the recording unit 1 wants to receive from the recording 
emitter 2. A coded signal corresponding to the interrogation, to which the 
recording unit 1 wants a response by the recording emitter 2, is obtained 
thereby that a coding device 11 in the recording unit 1 controls the 
transmitter so that the transmitter generates said coded signal 10. The 
interrogation signal, thus, is transmitted by the aerial 3a and received 
by the aerial 3b of the recording emitter. 
The recording emitter 2 is capable upon receipt of an interrogation signal 
to shift from a "stand-by" position to an operative position. The 
recording emitter 2, thus, does not consume energy while in "stand-by" 
position, as is previously known. 
Upon receipt of the interrogation signal in the recording emitter 2, the 
emitter switches to the operative position. 
The signal from the aerial 3b is received in the receiver 4b and decoded in 
the decoding device 5b, which is of a suitable known type. By guidance of 
the decoded information in the interrogation signal directed to the 
information unit 9, the information unit 9 emits a signal to a coding 
device 8 of a suitable known type, which signal corresponds to the value, 
digit etc. after which the recording unit 1 had interrogated. The 
information unit 9 also may be of a suitable known type. The coding device 
8 is capable to control the transmitter 4b in such a manner, that the 
transmitter generates a signal of fixed frequency, which signal 12 
consists of a pulse train so shaped that the signal is coded by having 
on-off character. The fixed frequency is the same as the fixed frequency 
generated by the transmitter 4 of the recording unit. 
Said signal 12 is emitted from the aerial 3b, after which emittance the 
recording emitter 2 reassumes stand-by position. 
Said lastmentioned signal 12 is received by the aerial 3a and receiver 4a 
in the recording unit 1. The signal received is decoded in a decoding 
device 5a of the same type as mentioned above, whereafter the decoded 
signal is stored in a device 6, for example by means of known memory 
units. The device 6, as mentioned above, further comprises means, for 
example for print-recording the information in the signal 12 emitted from 
the recording emitter and/or transmitting said information further to a 
central station. After the information has been processed in said device 
6, the recording unit 1 assumes "stand-by" position until the starting 
device 7 again actuates the transmitter 4. 
It is apparent to everybody, that a system corresponding to the one 
described above can be utilized for a great number of purposes, such as 
information transfer of data concerning, for example, water pressure, 
temperature, flow, weight etc. between two or more objects movable 
relative to each other. 
A special application of this system is the recording of objects as 
described in our Swedish patent applications Nos. 7503620-2 and 
7503621-0. 
When the recording emitter 2 is positioned stationary along a road 14, as 
shown in FIG. 2, and the recording unit 1 is positioned in a vehicle 13, 
the recording emitter 2 then can give information on road choice and 
rainfall, temperature, winds, road repairs etc. farther ahead on the road 
on which the vehicle is driving. In such a case, the interrogation signal 
emitted from the recording unit 1 may also contain an identification code 
for the interrogating vehicle, which code can be transmitted further by 
the recording emitter 2 to a central unit for processing. The recording 
emitter 2 further may receive information from a central unit, which 
information also is stored in the information unit 9. 
Known devices for a two-way information link, as already mentioned, are 
relatively complicated, for example, as concerns the aerials, where 
several frequencies must be used in order to prevent the receiver and 
transmitter from affecting one another. The present invention offers a 
device, at which the same frequency is used for the interrogation signal 
as well as the response signal, and where transmitter and receiver do not 
affect each other, because the signal generated by the active transmitter 
element is transformed so that the aerials emit waves of a special nature 
which are transformed before they arrive at the active receiver element. 
In FIGS. 3a and 3b a device according to a first embodiment of the 
invention is shown. In FIG. 3a the device is shown by way of a section 
seen from the side, and in FIG. 3b seen straight from ahead. 
FIGS. 3a, 3b show the active oscillation element of the transmitter which 
consists of a transmitter diode 20, and the active receiving element of 
the receiver which consists of a receiver diode 21, both of which are 
positioned in the rearward space 23 of a waveguide funnel 22 common for 
transmission and receiving and connected to suitable electric circuits 
(not shown). The diodes 20, 21 are positioned perpendicularly in relation 
to each other in a plane perpendicular to the wave propagation direction 
of a transmitted or received wave. As a consequence thereof, the 
transmitter diode 20 and receiver diode 21, respectively, transmit and 
receive, respectively, waves which are plane polarized each in one of two 
planes perpendicular to each other, in such a manner, that said elements 
do not affect each other. 
The waveguide funnel 22 and the diodes 20, 21 are of a suitable known 
design. 
A means is provided for dividing said plane polarized signal generated from 
the transmitter diode into two orthogonal waves, one of which preferably 
is dephased 90.degree. in relation to the other wave, i.e. so that a 
circular polarized wave is produced and transmitted from the aerial. Said 
means transforms in the same way a received corresponding wave system to a 
plane polarized wave by dephasing one of the orthogonal waves in relation 
to the other wave, so that these waves will be in phase. The plane 
polarized wave thus obtained then is located in the plane, in which the 
receiver diode 21 is located. 
The units 1, 2 further are of such a nature, due to the location of the 
diodes 20, 21 relative to each other and to said means, that two units 1, 
2 directed toward each other are capable to transmit each a circular 
polarized wave of such a nature, that the wave from one unit has a 
direction of rotation opposite to the direction of rotation of the wave 
from the second unit, seen in a direction from one of the units to the 
other unit. 
When observing two units, said means, thus, brings about the effect that, 
when the transmitter element 20, 30 in each unit 1, 2 emits a signal, this 
signal is transformed to a wave system 10, which is orthogonal to a 
corresponding wave system 12 received by the same unit 1, 2, and which 
said means 23, 24 also is capable to transform to a signal directed to the 
receiving element of the same unit 1,2. 
Said means consists of a plane plate 24 of a dielectric material. The plate 
24 is located in said wave guide funnel 22 ahead of the diodes 20, 21 and 
positioned 45.degree. to the two polarization planes and in parallel with 
the wave propagation direction of the transmitter. 
The transmitting diode 20 of one of two units, thus, generates a plane 
polarized wave in the plane, in which the diode 20 is located, which wave 
when passing the plate 24 is transformed to a circular polarized wave, 
which is transmitted. This wave is received by the second one of the two 
units. The circular polarized wave when passing the plate 24 thereof is 
transformed to a plane polarized wave in the plane, in which its receiver 
diode is located. To achieve this, the diodes 20, 21, for example, in two 
units directed to each other can be positioned equally, and the two plates 
24 be located in the same plane when the transmitter diodes and the 
receiver diodes, respectively, are located in the same plane. The 
aforedescribed device, thus, comprises the transmitter and receiver 4a, 4b 
and the aerial 3a, 3b in one unit, where the transmitter diode 20 and the 
receiver diode 21 do not affect each other during the transmission or 
receiving operation, because at transmission and receiving, respectively, 
they are only connected each to one of two planes perpendicular relative 
to each other. 
The device, thus, is very simple and shows the special advantages, that the 
aerial as well as the electric circuits coupled to the diodes can be 
designed tuned on the same frequency with respect to transmitting and 
receiving. A further very essential advantage is, that the mutual relation 
of rotation between two units directed to each other is of no importance 
for transmitting or receiving, because the waves existing between the 
units are circular polarized. This advantage is particularly valuable when 
information is to be exchanged between two units with unknown mutual 
relation of rotation. 
One example thereof is a crane hook associated with a crane where a 
recording unit is positioned stationary in relation to the jib and a 
recording emitter is stationary attached to the crane hook, which is 
rotated in relation to the jib by action a.o. of the load. At this 
example, information concerning the load weight in question is fed via a 
wire strain gauge on the crane hook to the information unit 9. The 
recording unit then interrogates the recording emitter at suitable times 
on the load weight in question, and the emitter emits a response signal to 
the recording unit. 
A second embodiment according to the invention for the transmitter and 
receiver 4 and the aerial 3 is shown in FIG. 4. At this embodiment the 
active oscillation element of the transmitter consists of a transmitter 
diode 30, and the active receiving element of the receiver consists of a 
receiver diode 31 positioned in electric circuits 32, 33 to generate a.o. 
the effect required for transmission. 
A hybride 34 is provided, which preferably is a so-called 3dB hybride. The 
hybride comprises four connection terminals, of which two, Te1 and Te2, 
are connected to an aerial 35 common for transmitting and receiving, and 
one terminal, Te3, is connected to the transmitter diode 30, and one 
terminal, Te4, is connected to the receiver diode 31. 
The hybride 34 at this embodiment constitutes said means for dividing the 
signal generated by the transmitter diode into two signals, which are 
emitted as two orthogonal waves, and for transforming a received 
corresponding wave system to a signal emitted to the receiving unit. The 
hybride is of such a nature, that a signal generated by the transmitter 
diode 30 and fed in at the terminal Te3 is divided into two signals 
dephased by 90.degree., of which signals one is fed out at the terminal 
Te3 and the other one at the terminal Te2. The terminal Te4 then is dead. 
Inversely, upon receiving, a first signal is fed in from the aerial 35 at 
the terminal Te1, and a second signal dephased 90.degree. relative to the 
first signal is fed in at the terminal Te2. One or both of these signals 
are phase turned in the hybride 34, so that the two signals are given the 
same phase, whereafter they are fed out at the terminal Te4 while the 
terminal Te3 is dead. The hybride 34, thus, causes at transmission two 
signals be fed to the aerial 35. Said aerial 35 is a per se known mat 36 
of electrically non-conductive material provided with electrically 
conductive elements 39 arranged in spaced relationship in rows 37 and 
columns 38. Said elements are row-wise and column-wise electrically 
connected to electric conductors. All rows, besides, are interconnected 
along two sides perpendicular to each other, and all columns are 
interconnected by conductors 40 and 41, respectively. Each conductor 40, 
41 is provided on its centre with a tap 42 and 43, respectively, which 
form an input or output for a high-frequency signal emitted or received by 
the aerial. When a signal is applied only to one of the two inputs, a 
plane polarized wave is emitted with an orientation, which is in parallel 
with the rows 37 when the output 42 is used, and which is in parallel with 
the columns 38 when the output 43 is used. 
The signals thus fed from the hybride 34 with a phase-shifting of 
90.degree., but with the same frequency, are fed in at the inputs 43 and 
42, respectively. Owing to the fact that the signals are of the same 
frequency and dephased 90.degree. relative to each other, a circular 
polarized wave is emitted from the aerial which, thus, consists of two 
orthogonal waves. 
Inversely, when such a wave system is to be received, the aerial 35 reacts 
inversely, because it is sensitive in two directions, so that the aerial 
divides a received circular polarized wave into two orthogonal components 
having the same frequency but dephased 90.degree. relative to each other. 
One of these components is fed out as signal at output 42, and the other 
component at output 43. The hybride 34, as mentioned above, is of such a 
nature that only one wave is fed out at the terminal Te4, i.e. to the 
receiver diode 31. 
As described above in connection with the first embodiment, also the units 
according to the embodiment described last are of such a nature, resulting 
from the design of the hybride 34 in relation to the location of the 
diodes 30, 31, that two units 1, 2 directed to each other are capable to 
emit each a circular polarized wave of such a nature, that the wave from 
one unit has a direction of rotation opposite to the direction of rotation 
from the second unit, seen in a direction from one of the units to the 
other one. 
According to this embodiment of the invention, thus, it also is achieved 
that the waves emitted and received, respectively, are mutually 
orthogonal, and the device is of such a nature that at transmitting and 
receiving, respectively, the transmitting element and the receiving 
element do not affect each other. 
The device described, thus, comprises the transmitter and receiver 4a, 4b 
and the aerial 3a, 3b. The advantages of the device according to the 
second embodiment are in agreement with the advantages explained above 
concerning the first embodiment, with respect to that the transmitting and 
the receiving element do not affect each other, and with respect to the 
simplicity and use of the device. 
The invention must not be regarded restricted to the embodiment described 
and shown and to their structures, because they can be altered within 
their scope defined in the attached claims.