IDENTIFICATION EQUIPMENT

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP81-00120R000100010009-7
• Release Decision: RIFPUB
• Original Classification: K
• Document Page Count: 12
• Document Creation Date: December 22, 2016
• Document Release Date: December 8, 2003
• Sequence Number: 9
• Content Type: CONT

Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
NOV. 14, 1 3bi-1 N. A. E. WASTERLID 3,353,178
25 26
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FIG.1
INVENTOR
NILS A. E. WASTERLID
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
 Approved For Release 2009/04/10: CIA-RDP81-00120R000100010009-7
Nov. 14, 1967 N. A. E. WASTERLID 3,353,178
Filed Feb. 18, 1966
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FIG.2
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INVENTOR
NILS A. E. WASTERLID
BY
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Approved For Release 2009/04/10: CIA-RDP81-00120R000100010009-7
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
Nov. 14, 1967 N. A. E. WASTERLID 3,353,178
IDENTIFICATION EQUIPMENT
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FIG.3
INVENTOR
NILS A. E. WASTERLID
BY
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
Nov. 14, 1967
Filed Feb. 18, 1966
N. A. E. WASTERLID
IDENTIFICATION EQUIPMENT
FIG.4
76 77
FIG.6
3,353,178
.6 Sheets-Sheet 4
BY
INVENTOR
NILS A. E. WASTERLI0
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
Nov. 14, 1967 N. A. E. WASTERLID 3,353,178
IDtNTIFICATION EQUIPMENT
Filed Feb. 13, 1966 6 Sheets-Sheet 5
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INVENTOR
NILS A. E. WASTERLID
BY
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Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
Nov. 14, 1967
Filed Feb. 18, 1966
T
N. A. E. WASTERL1D 3,353,178
IDENTIFICATION EQUIPMENT
FI G.8
INVENTOR
NILS A. E. WASTERLID
BY
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
 U111LCU O " LCS I"ULC11L '1J111LC
1 2
3,3.531:78
IDENTIFICATION EQUIPMENT
Nits Arne Erland WV sterlid, Skolby, Sweden, assignor to
North American Philips Company, Inc., New York,
N.Y., a corporation of Delaware
Filed Feb. 18, 1966, SSer. No. 528,598
Claims priority, applicatio$tSweden, Feb. 13, 1965,
2,142165
10 Claims. (ci. 343-6.5)
The present invention relates to an equipment for iden-
tification of an object which is movable past a measuring
station, such as a railway carriage or the like, by means
of an inquiry device situated at the measuring station and
adapted to transmit an inquiry signal. A reply unit is situ-
ated upon the object and adapted to respond to the said
inquiry signal in a specific way characteristic for the
object. The equipment is of the type in which high fre-
quency electromagnetic energy is used for transmission
of the information required for the identification. An
identification equipment operating with radio frequency
signals is known in which the reply unit has a transmitter
which is excited by means of a signal transmitted from
the inquiry device and which due to this excitation re-
transmits a reply signal with characteristic form to the
inquiry device. The signals in this known device are modu-
lated carrier signals of different frequencies. This known
system has the drawback that the reply unit necessarily
will be relatively complicated since it comprises a com-
plete transmitter having at least one active element, such
as a transistor or the like. The presence of active ele-
ments in the reply unit also brings about increased risks
for error function and increased costs of maintenance.
The purpose of the invention is to produce an identifi-
cation equipment in which the reply unit can be made
more simple and compact than in known systems and in
which the reply unit does not contain any active elements.
This is achieved in an identification equipment accord-
ing to the invention in that. the inquiry device comprises
generator means for producing electromagnetic wave
energy of high frequency- The generator means coop-
erates with a sweep generator for sweeping the frequency
repeatedly across a certain frequency band. An antenna is
provided for transmitting the .energy directionally to the
reply unit and that the said. reply unit comprises a wave
guide system connected with a plurality of cavity reso-
nators having different resonance frequencies lying with-
in the frequency band of the transmitted energy for form-
ing a code which is characteristic for the object by modi-
fying the wave energy transmitted through the system in
response to the natural frequencies of the resonators. The
input of the system is connected to a receiving antenna
for reception of the said electromagnetic wave energy
and its output is connected to a transmitting antenna for
retransmitting to the detectingstation the transmitted wave
energy as modified by the said resonators. Means are also
provided more arranged in the detecting station for re-
ceiving the re-transmitted energy from the reply unit and
evaluating the reply signal by determining the modifica-
tion in the re-transmitted wave energy caused by the said
cavity resonators.
Thus, the invention is based upon the principle of cou-
pling back to the detecting station a portion of the high
frequency energy transmitted to the reply unit. The in-
formation is then given by ;the frequencies which are
blocked by the resonators in the reply unit and the fre-
quencies which are passed through the unit. Thus all active
elements in the reply unit will be superfluous and the
reply unit only serves as a "reflector" for transmission of
reply information in coded shape.
The reply unit comprises in a preferred embodiment
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two wave guides with the said cavity resonators arranged
in parallel between the wave guides for coupling the wave
guides to each other through the resonators. One of the
wave guides having an input end connected to the said
5 receiving antenna for reception of the transmitted high
frequency wave energy, and the second wave guide has an
output end connected to the transmitting antenna for re-
transmission of energy, so that high frequency wave
energy is coupled from the receiving antenna to the re-
10 transmitting antenna upon coincidence between the fre-
quency of the transmitted energy and the natural fre-
quency of any of the resonators in the reply unit.
The risk of direct coupling between the transmitting and
receiving means at the inquiry side will be decreased if
15 polarized microwave energy is used, and the polarization
in the two paths of transmission in direction to and from
the reply unit respectively are rotated 90? relative to each
other. A simple way of achieving such rotation of the
polarization planes is to use as transmitting and receiving
20 means cooperating wave guide horns which are rotated
90? relative to each other in the two transmission paths.
The invention is now explained more fully in connec-
tion with the accompanying drawings in which
FIG. 1 shows a block diagram of an identification
25 equipment according to the invention operating within
the microwave range,
FIG. 2 shows a block diagram of an evaluation de-
vice which can suitably be used in connection with the
shown identification equipment,
30 FIG. 3 shows a number of time diagrams for explana-
tion of the function of the equipment,
FIG. 4 shows a suitable embodiment of reply unit with
cavity resonators,
FIG. 5 shows a code mask adapted to be used in the
35 reply unit according to FIG. 4,
FIG. 6 shows a preferred embodiment of the reply
unit,
FIG. 7 shows a block diagram of a device for com-
pensating for temperature differences between cavity res-
40 onators in the reply unit and in the detecting station,
FIG. 8 shows time diagrams for explaining the func-
tion of the device according to FIG. 7.
In FIG. 1 reference numeral 1 designates a high fre-
quency generator operating within the microwave range,
45 for example at a wave length of the magnitude 2-10
cm. The high frequency generator has its output con-
nected to two wave guides 2 and 3 of which the said
last wave guide 3 terminates in a wave guide horn 4.
The coupling between the high frequency generator and
50 the wave guides 2 and 3 is such that the main portion
of the energy is fed to the wave guide horn 4 through
the wave guide 3, while only a small portion of the en-
ergy is led to the wave guide 2 for producing reference
and control pulses. The high frequency generator is a
55 backward wave oscillator which is characterized in that
the delivered frequency varies with the voltage applied
to a control electrode. The backward wave oscillator co-
operates according to the invention with a sweep cir-
cuit 5 consisting of a flip-flop 6 and an integrator 7.
60 The flip-flop circuit 6 is assumed in the shown example
to be of bistable type and is controlled from the output
of two detectors 8 and 9. The said detectors are con-
nected to the output of the high frequency generator
-through two cavity resonators 10, 11 which serve as
65 coupling means between two wave guides 12, 13 and
the said wave guide 2. The cavity resonators 12, 13 are
tuned to the limit frequencies of the required frequency
sweep. The integrator 7, which is controlled from the
flip-flop circuit 6 and delivers its output voltage to the
70 frequency control electrode of the back wave oscillator
1, is furthermore provided with a switching circuit (not
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
3
shown) for switching its time constant between two dif-
ferent values. The switching circuit is controlled from
the output of the detectors 8 and 9.
The inquiry device also comprises, in the shown cx-
rnple, ten cavity resontors 14-23 for producing refer-
ence pulses for evaluation purposes. These cavity reso-
nators serve as coupling means between the said wave
guide 2 connected to the output of the high frequency
generator and a wave guide 24 which leads the energy
coupled through the resonators to a detector 25. The
output of detector 25 is connected to a first input of an
AND-gate 26, the second input of which is connected
to that output of the flip-flop circuit 6 which is used for
control of the integrator. A voltage will appear upon the
output lead 27 of the AND-gate 26 only if a voltage is
present on both of its inputs.
The resonance frequencies of the cavity resonators
14-23 are suitably distributed evenly over the frequency
range of the high frequency generator 1.
Zhe reply unit shown to the left in FIG. 1 consists
of two wave guides 28 and 29 each connected to a wave
guide horn 30 and 31, respectively, and connected to
each other through, in the shown example, six cavity
resonators 32-37. The wave guide horn 30 receives the
energy transmitted from the inquiry device through the
wave guide horn 4, while the horn 31 retransmits the
energy coupled through the cavity resonators to the in-
quiry device. The resonance frequencies of the cavity
resonators of the reply unit are distributed within the fre-
quency range of the high frequency generator in the same
way as the resonance frequencies of the cavity resona-
tors included in the inquiry device for producing reference
pulses, however, with the difference that some of the
cavity resonators at the reply side are either omitted or
disabled by means of a code mask. The wave guides are
terminated by suitable impedances 38, 39.
The re-transmitted energy is received on the inquiry
side through a wave guide horn 40 and fed to a detector
41. The signal from detector 41 containing the informa.
tion required for the identification is fed to the evalua-
tion device shown in FIG. 2 through a lead 42.
To the evaluation device are also applied the output
pulses from the detector 9 through a lead 43 and the in-
verted output voltage from the flip flop 6 through a lead
44.
For eliminating the risk of direct coupling between the
wave guide horn 4 and the horn 40 as effectively as pos-
sible, the two cooperating wave guide horn pairs 4, 30 and
31, 40 arc suitably rotated 90? in relation to each other,
whereby the polarisation planes of the energy in the two
transmission paths will also be rotated 90? relative to each
other. The wave guide horns may furthermore suitably
be filled with a dielectric material for preventing collec-
tion of dirt.
The device functions basically such that the high fre-
quency generator is forced by the integrator to produce
successive frequency sweeps, and electromagnetic energy
during each such sweep is coupled back to the receiving
horn 40 of the inquiry device through the cavity reso-
nators of the reply unit as soon as the frequency of the
electromagnetic energy coincides with the resonance fre-
quency of any of the cavity resonators of the reply unit.
The detector 41 will as a result deliver a pulse series in
+'hich presence of a pulse at a certain time position rela-
rivc to the frequency sweep indicates presence of corre-
''ponding cavity resonator in the reply unit and absence of
pulse indicates that corresponding cavity resonator is
mi'`ing or doubled.
tie function is illustrated by nseans of the diagrams
'(1)"P. 3 where diagram A shows the output voltage of
ilop circuit 6 fed to the integrator, B shows the fre-
variation of the high frequency generator 1 with
C shows the output pulses from detector 8, D shows
?"'a. of pulses from detector 9, E shows the output
p* tiOni AND-gate 26 and G shows the output pulses
4
from detector 41. T1-T7 in FIG. 3 are successive meas-
uring intervals separated by a short return interval.
The flip-flop is assumed initially to be in zero position
and at this time delivers zero voltage to integrator 7 (A
in FIG. 3). The integrator having a low time constant at
this moment produces a voltage which varies rapidly with
time and produces a corresponding rapid frequency
sweep, the return sweep, of the high frequency generator
(diagram B in FIG. 3). When the generated frequency
reaches the resonance frequency of resonator 12 then de-
tector 8 will deliver a pulse (C in FIG. 3) which pulse
switches flip-flop 6. The pulse from detector 8 also switches
the time switching circuit of the integrator so that the
said time constant now assumes its higher value. The
output voltage of the integrator therefore will vary slowly
in opposite direction and produces a slow sweep of the
frequency of signal generator 1, until the frequency
reaches the resonance frequency of resonator 14. Then de-
tector 9 will deliver a pulse (D in FIG. 3) which pulse
20 returns flip-flop 6 to zero position and at the same time
changes the time constant of the integrator to its lower
value. The output voltage of the integrator and therefore
the frequency of the signal generator now varies rapidly
until the resonance frequency of resonator 12 is again
25 reached. Then flip-flop 6 and the time constant of the
integrator are switched and a new frequency sweep starts
etc. ,
Each time the frequency of the generator 1 coincides
with the resonance frequency of any of the resonators
30 14--23 coupling will be established between the wave
guides 2 and 24 and consequently an output pulse will
be delivered from detector 25. AND-gate 26 receives
voltage from the flip-flop 6, during the slow frequency
sweep whereby all ten produced pulses during this sweep
35 will pass through the gate and arrive to the evaluation
device (see diagram E in FIG. 3). Contrarily no voltage
is led from flip-flop 6 to the gate 26 during the rapid re-
turn sweep and the produced pulses during this sweep
will consequently be blocked by the gate.
Electromagnetic energy transmitted to the reply unit
will as mentioned be coupled back to the receiving horn
of the inquiry device through the cavity resonators situ-
ated in the reply unit provided that the reply unit is sit-
uated within the working range of the inquiry device.
Each resonator will then give rise to a pulse at the output
of detector 41, which pulse is led to an evaluation device
(see -diagram G in FIG. 3 )..In the first moment when the
coupling between the transmitting and receiving horns
of the inquiry device and reply unit is weak during the
movement of the reply unit relative to the inquiry device
it is possible that an erroneous response is produced. This
is assumed to have occurred during the first frequency
sweep Ti in .FIG. 3.
The pulses produced by the cavity resonators of the
inquiry device will coincide in time with the reply pulses
from the reply unit due to the fact that the inquiry de-
vice comprises the same resonance frequencies as the re-
ply unit. The pulses from the output of AND-gate 26
can therefore be used as time reference for the reply
pulses.
The shown evaluation device consists according to
FIG. 2 of a shift register 50 and a memory 51. Both
shift register and memory are composed by bistable cir-
cuits F1-F10 and Ml-M10, respectively, of a type known
per se and each have each a number of such bistable cir-
cuits or stages equal to the number of resonance circuits
used for producing reference pulses in the inquiry de-
vice, i.e. in the present case ten stages. The said code
pulse series G from detector 41 are led to the first stage
Fl in the shift register, while the reference pulses E
from AND-gate 26 are applied to the shift inputs of the
stages F1-F10. The pulses D from detector 9 indicating
the end of a frequency sweep are led to all stages Fl-
F10 in the shift register and furthermore to all stages
MI-M10 in the memory in order to in a way known per
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 Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
se transfer the
to the memory
shift register.
5
information stored in the shift register
under simultaneous zero setting of the
Each stage of the memory has one output connected
to a first input of an AND-gate GI-G10 included in a
blocking device 52, which AND-gates have a second input
connected to the output of a device 53. The device 53 pro-
duces output pulse only if in the shown example three
successive sweeps give rise to the same registration in the
shift register. The device 53 consists of an OR-gate 54
with twenty inputs connected to the outputs of the in-
dividual stages MI-M10 of the memory 51 through dif-
ferentiating circuits dl, d2 .. d20. The OR-gate 54
produces output pulse of a certain polarity when a volt-
age change corresponding to the selected polarity ap-
pears upon any of the inputs of the gate. Output pulse
will be received from gate 54 as' soon as any of the
stages of the memory is switched in either direction due
to the fact that both outputs of the memory stages Ml-
M!O are. monitored. The output pulse from OR-gate 54 is
used to switch a monostable flip-flop 55 having a return
time which is somewhat longer than the period time of
the frequency sweep. The output pulse from OR-gate 54
is also led to a first input of an AND-gate 56, the second
input of which is connected to one output from flip-flop
55. The AND-gate 56 is open when flip-flop 55 is in
position 1 and blocked when the flip-flop is in position 0.
The output of AND-gate 56 is connected to a second
monostable flip-flop 57 having a return time which also
somewhat exceeds the period time of the frequency sweep.
The monostable flip-flop 57 is thus switched by the out-
put pulse from OR-gate 54 provided that the preceding
flip-flop 55 is in position 1. An output AND-gate 58 is
connected on.the one hand to the two monostable flip-
flops 55 and 57 and on the other hand to the sweep flip-
flop 6. The AND-gate 58 produces output pulse only if
the two monostable flip-flops 55 and 57 are in position 0
and the flip-flop 6 is also in the 0-position, i.e. the position
when the rapid return sweep is produced.
The evaluation procedure is illustrated by the lower
diagrams in FIG. 3, wherein El shows the pulses led
from the sweep flip-flop 6 to the output gate 58, diagram
H shows the output pulses from OR-gate 54, K shows
the pulses which are led from flip-flop 55 to AND-gate 57,
R shows the pulses led from flip-flop 55 to AND-gate 53
and I, shows the pulses led from flip-flop 57 to AND-
gate 58, The last diagram F in FIG. 3 shows the pulses
which are derived from AND-gate 58 and form output
pulses from device 53. The output pulses F from AND-
gate 58 are according to FIG. 2 led to all AND-gates G1-
G10 in the device 52 and furthermore through a delay
device 59 to all stages MI-M10 in the memory 51. At
the appearance of output pulse F from 58 are all AND-
gates in the device 53 opened and the information stored
in the memory 51 is then led through the respective AND-
gate to an indication or computer device (not shown).
The delay device 59 has a time delay which somewhat
exceeds the pulse length of pulses F from AND-gate 58.
The delayed pulse F from device 59 produces switching
of all stages in memory 51 to 0-position.
It has been assumed in FIG. 3 that the re-transmitted
signal during the first frequency sweep is incorrect due
to weak coupling between the reply unit and the inquiry
device, while the remaining sweeps produce correct in-
formation. Before the reply unit has cone within reach
of the inquiry signal all stages are in the shift register
and the memory in 0-position.
The evaluation of the reply information is effected in
the following way.
When the frequency of the generator during a sweep
reaches the resonance frequency of the cavity resonator
in the inquiry device which has the lowest or highest fre-
quency dependent upon the sweep direction, then AND-
gate 26 will deliver the first reference pulse E (FIG. 1).
This pulse is led to the shift inputs of all stages in the
shift register 5o but as all stages in the register are in 0-
position the shifting has no effect at this moment. If the
corresponding cavity resonator is present in the reply unit
and this is within reach of the signal from the inquiry de-
vice, pulse E is. simultaneously received from detector 41,
which pulse will be registered in the shift register in that
the first stage F1 is switched to position 1. If no pulse E
appears, F1 remains in 0-position. When the frequency
has reached the resonance frequency of the second rdsona-
10 for in the inquiry device the digit I in Fl, if present, will
be shifted to F2 at the same time as presence of corre-
sponding cavity resonator in the reply unit is registered
in that F1 remains in position 1; otherwise F1 is switched
15 to position 0. The information upon reaching of the next
resonance frequency is again shifted one step to the right
at the same time as possible pulse caused by the presence
of corresponding cavity resonator in the reply unit Is
registered in Fl etc. After the reception of the 10th and
20 last pulse E from AND-gate 26 the first E-pulse received,
if present, will be stored in the last stage F10, while the
next pulse will be stored in F9 etc. Immediately thereafter
pulse D from detector 9 arrives whereby the conditions
of the different stages in the shift register 50 is transferred
25 to corresponding stages in the memory 51 at the same
time as the shift register is zeroed. As the memory stages
were initially in 0-position output pulse H from OR-gate
54 is produced and the flip-flop 55 switched to position 1.
The pulse H can, however, not switch flip-flop 57 as AND-
30 gate 56 is blocked at the moment for appearance of H-
pulse (flip-flop 55 in 0-position). Presence or absence of
signal frequencies in the re-transmitted signal is during
the next following sweep T2 registered in the same way
in the shift register 50 and the information transferred
35 from shift register to the memory at the end of the sweep.
As according to the foregoing it is assumed that the same
information is not received during the two first sweeps,
at least one memory stage will be switched and output
pulse H from OR-gate 54 is received at the end of the
40 second sweep '12, see diagram 3. The monostable flip-flop
55 is still in position 1 and output pulse H therefore will
switch flip-flop 57 to position 1. The flip-flop 57 will then
deliver a blocking pulse to the AND-gate 58. New register-
ing in the shift register 50 and transfer of the information
45 to the memory 51 at the end of the frequency sweep is
effected during the following frequency sweep T3. In this
case it is assumed that the same information is received
as during the foregoing period, and therefore none of the
stages in memory 51 is switched. No output pulse II is
50 received from OR-gate 54 and the flip-flop 55 which has
returned to position 0 during T3 remains in position 0.
The voltage pulse X can, however, not produce any out-
put pulse F from AND-gate 58 at the end of sweep T3
as the monostable flip-flop 57 is still in position 1 and
55 blocks the gate 58. During the following sweep T4 is
the same information again registered in shift register 50
and no stage in the memory is switched. No output pulse
H is received from OR-gate 54, and the flip-flop 55 re-
mains in 0-position. 57 returns to position 0 during the
60 period T4 and at the end of the 4th period T4 thus both
flip-flops are in 0-position. The pulse 1 at the end of this
period will therefore produce a corresponding output pulse
F from the output of AND-gate 58, which output pulse
F opens all AND-gales in the blocking device 52 so that
65 the information stored in the memory 51 is led further to
the indicator or data computor device. The output pulse
F also produces zero setting of all stages in the memory
51 through the delay device 59.
If it is assumed that the movable reply unit is still
ef- fectively coupled to the inquiry device a new correct
registering wilt be received in the shift register 50 during
the following sweep period T5, which registering is trans-
ferred to memory 51 at the end of the period. As the
75 memory was initially in 0-position an output pulse H will
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he received from the OR-gate 54 and flip-flop 55 is
switched. Provided that correct information is received
from the reply unit during the next period T6 no stage
in the memory 51 will be switched at the end of the said
period T6, whereby no pulse H is produced and flip-flop
57 remains in position 0. During the next following period
T7 returns flip-flop 55 to position 0. At the end of this peri-
od both 55 and 57 are thus in 0-position and a pulse F
is again received from AND-gate 58.
By means of logic circuit elements it is possible to fur-
ther decrease the probability for erroneous evaluation in
that 4, 5 or more successive and equal registrations are
necessary before the blocking is released and the stored
information is led out for computation or indication pur-
poses.
FIG. 4 shows a perspective partially transparent view
of a suitable embodiment of the reply unit With cavity
resonators and wave guides. The cavity resonators in-
cluded in the inquiry device may be of the same con-
struction apart from the fact that no code mask is re-
quired in this case.
The shown reply unit consists of a metallic body 60
which is tapered toward one of its ends and which con-
tains apertures 61-65. The wave guides 66, 67 are ar-
ranged on each side of the body 60 having their side walls
bearing against the surfaces of the body 60 containing
the said apertures. The apertures form cavity resonators
which are coupled to the respective wave guide through
circular openings in the side wall of the respective wave
guide. The cavity resonators will have different lengths
due to the varying height of the body 60 and hereby a
successive variation of the resonance frequency from
cavity to cavity is produced.
At the separation line between wave guide 67 and the
body 60 there is a slot in which the code mask 68 shown
in FIG. 5 can be introduced. The code mask 68 consists
of a number of metallic tongues 70-72 fixed upon a
common body 69, which tongues may either have a con-
vex end as shown at 73 and 75 or a concave end as shown
at 74. In the said first case the actual cavity will be
screened-off at introduction of the code mask in that the
opening between the wave guide and the cavity is covered
by the metallic tongue, while in the said last case the
opening between cavity and wave guide will remain free.
It is also possible to omit the metallic tongues at those
places where no blocking of the cavity resonator is to
take place. By the use of such code masks all reply units
can be shaped in the same way. Only the code mask will
have varying shape in different units. It is also possible to
achieve recoding in a simple way by replacing the code
mask. The cavity resonators of the inquiry device may
suitably be shaped in the same way but without code
mask or with a code mask which gives free passage to all
cavities.
The resonators in the reply unit may alternatively be
of constant height and varying diameter. In FIG. 6 is
shown a small section of such a reply unit, in which the
resonators are formed by a number of metallic tubes 76,
77, 78, 79 arranged in parallel between the two wave
guides. The tubes are of the same length but varying
inner diameter from tube to tube. An advantage for this
type of resonators is that a wider frequency band will be
available without risk for false resonator modes in the
resonators. Thus it is possible for example to operate in
the frequency band from 14-16 gHz. without false reso-
nances. This results in that a very large number of reso-
nators, of the order 50-60 or even more, can be used in
the reply unit resulting in a corresponding number of in-
formation bits in the coded reply information.
A suitable code is the two-out-of-five code, in which
the resonators are divided into groups of five resonators
and each such group cooperating for forming a digit ac-
cording to the said code.
For disturbance suppression in order to eliminate the
risk that false pulses are indicated in the evaluation de-
vice as reply pulses it is suitable to block all pulses from
the receiving antenna 40 (FIG. 1) which do not coincide
in time with a reference pulse from the reference reso-
nators 14-23. If such a time discrimination of the reply
pulses is to be used it will be necessary to ensure that the
pulses from corresponding resonators in the reply unit
and the reference unit appear at the same moments. How-
ever, the dimensions of the resonators and consequently
the resonance frequencies are dependent upon tempera-
ture, and therefore small temperature differences between
the resonators in the reply unit and the reference reso-
nators will cause a small displacement of the resonance
frequencies in the reply unit relative to the reference
resonance frequencies resulting in a corresponding time
displacement between the reply pulses and reference
pulses. The temperature deviation can normally be made
small by arranging the reference resonators in proximity
of the reply unit. However, it cannot be avoided that un-
der unfavourable circumstances a temperature deviation
will appear, for example due to warming up of the reso-
nators in the reply unit from the wagon. A time discrim-
ination of described kind must therefore be combined
with an automatic temperature compensation.
This can for example be made by means of additional
resonators of equal dimensions in the reply unit and the
reference unit which are not included in the reply code
and only used for setting a compensation voltage in de-
pendence upon a measured time difference between the
extra pulse from. the reply unit and the corresponding
pulse from the reference unit. It is then assumed that all
pulses from corresponding cavities are time displaced the
same value and the compensation voltage is used to de-
lay for example the reference pulses such that they will
coincide in time with corresponding reply pulses.
A circuit for effecting such a temperature compensa-
tion is shown in FIG. 7. This circuit is adapted to be con-
nected between the pulse generating arrangement shown
in FIG. 1 and the evaluation device shown in FIG. 2.
The temperature compensation circuit consists accord-
ing to FIG. 7 of a fix time delay for the reply pulses G
shown in the form of a monostable flip-flop 81, a pulse
shaping monostable flip-flop 82 for the reply pulses, a
monostable flip-flop 83 controlled by the starting pulse C
for the frequency sweep (FIG. 1), three input gates 84,
85, 86, two sweep circuits 87, 88, a memory circuit 89,
a comparing device 90, a pulse shaping monostable fli
-
p
flop 91 for the reference pulses and an output gate 92.
The function of the compensation circuit is as follows,
reference being made to the waveform diagrams shown
in FIG. 8, in which the different diagrams are designated
in the same way as the corresponding points in the block
diagram according to FIG. 7 where the voltages in ques-
tion appear.
At the start of -a frequency sweep a pulse C appears.
55 This pulse is used to switch flip-flop 83. In switched posi-
tion flip-flop 83 delivers voltages T and T to the input gates
such that gates 84 and 86 are open and gate 85 closed.
When the frequency is increasing it will first reach the
60 resonance frequencies for the said additional resonators,
it being assumed in FIG. 8 that the temperature difference
between the reply unit and the reference unit is such that
pulse is first received from the additional resonator in the
the reference unit and a short time interval later pulse
65 from the additional resonator in the reply unit. The pulse
from the reference unit passes through gate 84 and starts
a linear sweep in sweep circuit 87, while the pulse from the
reply unit switches the delay flip-flop 81. When flip-flop
81 returns to its initial position it switches pulse shaping
70 flip-flop 82. The voltage rise at the left hand output from
flip-flop 82 passes 11rough gate 86 and stops the linear
sweep in circuit 87. The sweep voltage from 87 at the
end of the sweep its maintained in a memory circuit. 89,
75 the output voltage 0 of which thus will be a measure of
Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
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Approved For Release 2009/04/10: CIA-RDP81-0012OR000100010009-7
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the time delay S plus the fix delay in flip-flop 81. The of cavity resonators having different resonant frequencies
voltage flank appearing at the right hand output of flip-flop within said predetermined band for forming a code
82 at return of the said flip-flop is used to reset flip-flop characteristic of said object, second directional antenna
83, which thereafter remains in reset position during the means for receiving said transmitted energy and applying
whole frequency sweep until the beginning of the next 5' the received energy to said cavity resonators, whereby
sweep. At resetting the voltages at the output of flip-flop said received energy is modified by said cavity resonators
83 are altered so that gates 84 and 86 are closed and gate in response to their natural frequencies, and a third
85 opened. The next coming reference pulse E therefore directional antenna means for transmitting said modified
passes through gate 85 and starts sweep circuit 88 which energy toward said detecting station, said detecting station
has exactly the same sweep velocity as circuit 87. The 10 further comprising fourth directional antenna means for
voltage from sweep circuit 88 is compared with the con- receiving said modified energy, and means for determining
stant stored voltage in memory circuit 89 and at equal the modification of the received modified energy caused
voltages from 88 and 89 the comparing device 90 delivers by said cavity resonators.
a voltage pulse to sweep circuit 88, which stops the sweep. 2. The system of claim 1, characterized in that the
The rear flank of the sweep voltage from 88 switches flip- 15 reply unit comprises two wave guides, said cavity reso-
flop 91 which delivers a delayed reference pulse E'. As nators being arranged in parallel between the wave guides
the sweep velocities and the final sweep voltages are the for coupling the wave guides to each other through said
same in both circuits 87 and 88, the time delay of the resonators, one of the wave guides having an input end
reference pulse and all following reference pulses will be connected of Me said second antenna means for reception
exactly equal to the sum of time difference 5 and the fix 20 of the transmitted high frequency wave energy and the
delay in 81. The fix delay in 81 is chosen such that the second wave guide having an output end connected to said
sum of a and the fixed delay in 81 is always positive even third antenna means for re-transmission of energy, where-
at maximum temperature difference in such direction that by high frequency wave energy is coupled from second
the reply pulse G appears before the reference pulse E antenna means to the third antenna means upon coin-
(d negative). The delayed reference pulse E' is led on the 25 cidence between the frequency of the energy received
one hand to the evaluation device and on the other hand by said second antenna means and the natural frequency
to an input of output gate 92. At another input, gate 92 of any of the resonators in the reply unit.
receives the delayed reply pulse from flip-flop 82 and on 3. The system of claim 1, in which polarized micro-
a third input a control voltage from flip-flop 83. Due to wave energy is: used for transmission to the reply unit
the described automatic setting of the delay of reference 30 and re-transmission from the reply unit, characterized
pulse E' these reference pulses E' will always coincide in in that the polarization directions in the two transmission
time with possible reply pulses N from the output of flip- paths are substantially 90? with respect to each other.
flop 82, whereby the pulses N will pass through gate 92 4. The system of claim 1 wherein said detecting station
and form an output pulse signal G'. In the contrary if comprises a plurality of reference cavity resonators corre-
false pulses appear at the output of flip-flop 82: in wrong 35 sponding to the resonators in the reply unit, means for
time moments these pulses will be blocked by gate 92. applying energy from the said source to said reference
The fix time delay 81 and the adjustable delay may of cavity resonators, means for producing reference pulses
course change place so that the reference pulses are instead from said reference resonators, means for producing
delayed by a fixed amount and the delay of the reply pulses reply pulses from the energy received from said fourth
adjusted in accordance with the measured time difference. 40 antenna means, a gate circuit, means for applying said
The reply pulses G' and reference pulses E' can be reference and reply pulses to said gate circuit to produce
treated in the same way as described previously for pulses output pulses by coincidence, and recording means re-
E and G. sponsive to said output pulses for recording a coin-
Instead of using a reply unit operating such that only cidence in time: between a reply pulse and a gate refer-
those frequencies are re-transmitted which coincide with 45 ence pulse.
the resonance frequencies of the resonators in the reply 5. The system of claim 4, wherein said detecting sta-
unit it is alternatively possible to modify the reply unit tion is provided with a temperature compensation
such that it re-transmits all frequencies except the said device comprising time delay means for imparting to
resonance frequencies resulting in dips in the re-trans- the reply pulses or the reference gate pulses a time delay
mitted energy for each resonance frequency. This is 50 which is dependent upon a measured time difference be-
achieved in a simple way by arranging the receiving wave tween pulses from corresponding cavities in the reply
guide horn and re-transmitting wave guide horn at each unit and referrte cavities in order to make the pulses
end of one and the same wave guide and connecting the from corresporrrg, cavities to coincide in time.
cavity resonators in parallel between this wave guide and 6. The system of claim 1, wherein the cavities are of
a second wave guide with absorbing material so that the 55 the same inner d