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A Aug. 8, 1950
Filed June 23, 1945
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LeRoy Apkßev‘,
by /vWfJW/[email protected]
t-iis 'Attorney
Íäafented Àug. 8, >ÍÍÉÉÓ
UL'rirA nien ritEQUEncY RECEIVER
‘ Le- Roy Apker,v Niskayuna, N. Y., assìgnor to Gen
- eral- Electric Company, ar corporation of New
‘ Y Application June 23, 1945, Serial No. 601,124 1
5 claims.
(o1. 25o-_20)
`My invention _relatesïto ultra high frequency
apparatus and it hasïfor its-primary object to
provide new’ and improved means and methods
for-analyzing ultra high' frequency waves.>
in the appended claims. "The invention itself,
together with further objects and 'advantages
thereof, may »best be understood by reference to
the following description taken‘ïin'fconnection
The usual wide band ultra high frequency»
receiver for spectrum analysis is of the super
with the accompanying drawing-in which Fig.> l
is ‘ïa block diagramv illustrating the component
heterodyne type and provides frequency con
parts of an ultra high -frequencyl receiver suit#
ably embodying my invention; Fig. 2 isv a‘ hori
zontal section of my ultra high frequency appa-L'
ratus; Fig. 3 is a vertical sectionl taken along -the
linev 3-3 of Fig; 2; and Fig. 4 is 'an enlarged
transverse section-taken along the line 4`---'41~of-
version in the first stage of the receiver.> It is a
characteristic of such a receiver thatffor‘ each
single-frequency signal applied to the input, re
sponses are found when the receiver yis tuned
not only to the signal frequency but also to
various other vfrequencies.A The number` and
exact values `or positions in the frequency'spec
trum of these responses depend on the specific
values of the structuralv components of the re
ceiver.- The-usual receiver of this type has two
(the signal land its image) and frequently has
several other responses for each incident fre
quency, so that-it' is'often difficult to discriminate 20
betweenA genuine-’andfspurious‘ responses. vAc
cordingly, it'is'an'objectfof the present invention
to provide a new and` improved Wide band ultra
Y Eig. 2. '
Y The receiver circuit in Fig.' 1 comprises-a source
of input ‘signals »l’ which may beg'for-example sig
nals received by? an a?tenna'fïand varied ‘over a'
wide frequency' range', such‘gas from` ‘_1-0' `to 3500
megacycles, 'and rwhich -are supplied ¿through _a
choke 2 to a first mixer or rfrequency converter'3.'
Locally generated oscillations’ ofïïa frequency vf2
considerably higher than the frequency fl -ofthe
received signals,_ for example inthe- vcentimeter
Wave region, and varying' over a range which is
at least as broad’ (in magacycles) >asïtheïrange
ing the characteristics of a received «wave and in 25 of the receivedlsignals, 'are' supplied `from' a "varie
able frequency local oscillator 4 through a rejec`-‘
which, over any? practical range of received signal
tion filter 5 to thev mixer or frequency converter
frequencies, spurious -responsesin the output are
3. The converted ’output> signals >of the mixer
3, which are signals of a constant, very highfre~
'ï It is another object ef my invention to‘provide
a new and' improved wide band yultra high fre;- L quency, are l suppliedïfthro‘ugh " a ' sharply l tuned
transmission [filter 6 to al'second mixer-` or fre'
quency `signal vconverterv which ~-is both simple in
construction'and reliable -in operation. The con
quency converter 1.' Local-oscillations are 4like
wise supplied to the .mixer 'l'ífrom a second local
verter» minimizes spuriousv responses over a wide
oscillator B'through afpa'ir of‘.rejectionïfilters‘9,4
range of frequency without requiring tuning ele-y
ments resonant yin this range. v'In thisway, the
I0. vThe frequency f3‘^of theoscillationsof the
oscillator~ 8 is' . of yther isame order- i'as-r that of vthe'
usual ltuners placediß'ahead'ï of superheterodyne
oscillator 4. It is separated from-«the constant
converters (for example)`v for rejection of spurious
frequency output Í signal ïof mixer-"3I by a fre-`
responses `are eliminated. l
' "
high frequency spectrum analyzer for determin
quency difference such -that the ¿constant -fre'
" One of thefeatures of my invention -ïis the em
ployment, in -an' instrument for analyzingA the 40 quency output signal of :the mixer ‘I -is offan order
such that the`ampliñer1l2 may be‘conventional
spectrum of av wide band of ultra-high frequencies,
in character. This` output signaltha's a constant
of ¿a vsource - of-l oscillations- considerably 'higher in
frequency than lthe‘s'ig?als to be analyzed‘- This
source is variable over- a range as broad in'mega
frequency value» considerably > lower >than Íthe
Two stages of frequency conversion are‘connected
of Ímixer 3. The Ioutputìofïthe amplifierA |.2‘l may
be supplied to _any l'output’hmeans,suchfïfasf-a
cathode ray tube |Í3,ïtofmeasure or otherWise`de-~
tuned frequency'of the 'oscillators 4 and B-"an‘d
cycles as the frequencyfspectrum to be covered. 45 lower than thefconstantfrequency output signal
through means for filtering the'signals atvthe
output of the first `stage-"of conversion toremove '
undesired modulation products. The signal pro
termine or display th'e‘ïlfrequency of -` the input
duced at the 'output ‘ofthe second stage is of' a 50
constant frequency'having'a value such that it:
can be ampliñed"
Etconventional amplifier cir-A
.In the' circuit of Figfi, the alters 5, t andiïlu
are all tuned tothe frequency of theconstantf
frequency` signal obtained" through the frequencyv
conversion actionv of the mixer 3, kthat `is,fo'r
' The featuresof-the invention which 1 desire »to
protect herein areïpointe'd outwith partioularìty 55, example the'difference between the frequency 'of
me'gaeycles, arel mixed through the action vof the
crystal -25 withioscilla'tions from the source 4 to
provide a constant frequency signal. This con
stantI frequency signal is filtered by the trans
mission filter 6 -to 'removeundesired modulation
products and 'supplied to‘thecrystal 36 where it
is ’mixed with'oscillationsfrom the source 8 to
produce a constant frequency output signal of
relatively low lfrequency which-is supplied to the‘V
amplifier I2. Thé oscillator 4 is' variable in char
acter and isVaried-"over its tuning range, which
may be from 22,000 to 25,500megacycles, until
the- mixed signalï produced by the crystal 25 is of
the frequency to which- the transmission filter 6
tuned;y When-the‘frequencies of the source I
andthe oscillator 4 are thus correlated, a con
stantultra high frequency signal is provided by
crystal 25. This signal passes through trans- mission filter 6 and is combined by crystal 36
with oscillations from voscillator-8. >These oscil
lations are of ultra'high frequency, for example
21,885 megacycles. The crystal 36combines the
two ultra high frequency waves to form a con-k
ventiou as applicable to an ultra' hignfrequenoy
spectrum analyzer, it is apparent that the invene
tion may be employed to analyze lower >frequency
waves?, one of the requirements being »the use of '
an oscillator variable over a- frequency 'range‘of
cycles or kilocycles equal to the range »of fre-1
quencies to be covered by the analyzer. `It isap
parent likewise that- whenl used for lower fre'
quencies the filters of thesystem which »are em
ployed may be different in form from those illus
trated in the ñgures of the drawing; Further
more, by the use of suitable pretuning circuits
»before supplying an input waveto a ñrstmixer
of the analyzer, further rejectionv of undesired
WhileisI obtained.
have shown and‘ described my
tion by reference to a particular embodiment
thereof, it will be understood that numerous
modifications may be made by those skilled in
the art without departing from' the invention. I
therefore aim in the appended claimsto coverall
such equivalent variations as come within the
v-true spirit and scope of my invention.
, y
,. What I claim as new and desire to secure 4by
stant low frequency signal'which is supplied over
Patent of the United States, is:
the transmission line 38, 39 -to the amplifier l2 so
» 1. Apparatus for determining `the frequency of
that an indication -is obtained on the cathode ray
an ultra high frequency wave comprising a metal
tube i3 vor anyother suitable output device. The
lic _Wave guide of the hollowpipe type, a pair ,of 0S.
rejection filter 5 reflects the constant frequency
connected respectively to opposite ends
signal obtained 'through the- action of the crystal
of said guide for supplying thereto oscillations of
25 in proper phase so that this signal is not lostl 30 a
frequency substantially larger than> the fre
in the guide section connecting with oscillator 4.
quency of said wave, a pair of nonlinear devices
but is transmitted efñciently to element 36. Sim
connected across said guide at spaced points, filf
ilarly, the rejection filter I0 vprevents transmis-v
tering means comprising a cavity resonator pof
sion to the oscillator 8 of the constant frequencyv
signal transmittedthrough the transmission fll- '
Vsitioned vtransverse said guide between ~said
points, said resonator having apertures -corn
ter 6 and permits efiicientpickup and conversion f . municating
with said guide on opposite sides of
by crystal 36. The filter eshort-circuits thesaid resonator, means for supplying said wave
crystal‘36 for undesired modulation products of I _
crystal 25 that leak through filter 6.
~ From the foregoing explanation, it is seen that
an important advantage of my spectrum analyzer
is that it allows the detection of input frequencies
over a wide range and simply through the tuning
of the oscillator 4 alone, which may be effected
by a simple tuning knob, supplies to the amplifier
l2 a constant frequency signal. At the same time, '
undesired modulation products which might
to said guide on one side of saidñltering means,
and output means connected to `said guide ¿on
the other side of said filtering means.
2. An ultra high frequency receiver comprising
a metallic wave guide of the hollow pipe type, a
pair of oscillators connected respectively to op
posite ends of said guide forsupplying thereto
oscillations of a frequency substantially larger
than the frequency of a received wave, a pair of
nonlinear devices connected across said guide at
spaced points, filtering means comprising a
otherwise produce spurious responses are sup
pressed through the filtering action of the filters
5, t, 9, and i0. It is thus apparent that a single 50 cavity resonator positioned transverse said guide
between said points, said resonator having
full strength response for a given input signal
apertures communicating with said guide on op
is obtained if the oscillator 4 is tuned through its
posite sides of said resonator, means supplying
complete range, all other responses requiring at
said wave to said guide on one side of said filter
least a 30 db. larger input. Another advantage
of my invention is that the nlters required are . ing means, output means connected to said guide
on the other side of said filtering means, and
simple in character and at the high frequencies
additional cavity resonators connected across
employed, are quite sharp in action and have a
said guide between each of said nonlinear de
high Q.
vices and the one of said oscillators adjacent
It is well known that in frequency conversion
apparatus utilizing crystals as a frequency con 60 thereto.
3. A receiver for high frequency signals varying
verting medium, the crystals must be operated
a wide range of high frequency comprising
under eñicient conditions in order to prevent loss
‘a metallic wave guide of the hollow pipe type, a
of received signals. To that end it is essential
first source of oscillations of a frequency higher
that proper termination of the wave transmit
than the frequency of said signals connected to
ting channel be provided for the various fre
said wave guide at one end thereof, means for sup
quency waves present in the crystal circuits.
plying received signals to said guide at a point
This is achieved in my improved circuits by
adjacent said one end, means for combining said
means of the filters 5, 6, 9, and l0 and by means
received signals with said oscillations to produce
of the chokes 2 and H, which so terminate the
a converted signal of constant high frequency, a
respective portions of the wave transmission
second source of oscillations having a frequency
channel that no received energy is dissipated
of the order of the frequency of said first oscil
through improper termination. As a result, good
lations connected to said wave guide at its other
conversion efficiency is obtained in each of the
end, means including a cavity resonator con
crystals 25, 36.
While in the foregoing I have described my in 75 nectcd across said guide between said converting
Ineens and said second source for removing'nun
desired modulation products 4from said converted
signal, and means for combining said converted
signal with said second oscillations to produce a
second converted Vsignal of lower constant fre
4. A receiver for signals varying over a Ywide
range'of ultra high» frequencies comprising a
metallic wave guide of the hollow pipe type, a
first-source of oscillations of a frequency higher
than any frequency in said range connected to
one end of said guide, the frequency of said first
source being variable over a. second range equal
in width to said first range, a second source of
constant frequency oscillations of a frequency
higher than any frequencyl of said ñrst rangecon
nected to said guide at its other end, filtering
means_comprising a cavity resonator positioned
_transverse said guide at a point between said
ends, said resonator having apertures communi
eating. with said guide lon opposite sides of said
resonator,l means for supplying said signals to
said guideat a point between said filtering means
Constant .frequemaosciilatorconnected t0 laid
,guide .at its other end», ,fi-11st.l _ñltering means com
prising _a cavity l:resonator„positioned transverse
said guide at al point between said ends, said
resonator .havingl apertures communicating `with
said guide onoppositesidesof. said resonator,
.means ,for suppbl’ingfsaid „signalsfto said guide be
tween Isaid ¿variable „« oscillator A and said filtering
means, a flrstrcry’stal; rectifier connectedacross
saidl‘guide for. 'mixing Lvsaid . oscillations from said
:variable -oscillatorand saidvsignals to produce a
constant frequencyvwave, said filtering means îbe
,ing >tuned to thefrequency oisaid wave, a second
lcavity resonator connected between said first
crystal »rectifier .and said ¿variable oscillator to
prevent loss Aof said wave, atîecoxiel` crystal rectifier
connected-between said. :first filtering means and
said constant _fi‘equencyoscillator to produce an
output signal determined by the frequency oi said
wave and ksaid constant frequency oscillations, a
third cavity resonator connected between said
second crystal rectiñer and s_aidconstant fre
quency oscillator to`A prevent said wave from reach~
md'said first source', mixing means connected
ing said _constant frequency oscillator, and output
across said guide between said ñltering means and ’
electrodey means connected to said guide between
said .nrst source to combine said signals and oscil
lations of said first source to produce a constant
saidiirst andftliirdí cavity resonators. ,
frequency wave, said filtering means being tuned
to the frequency of said wave, a second mixing
means connected to said guide between said filter
ing means and said second source to produce a
` The following>vv referencesf‘are" lo1' record'ln the
constant. frequency output signal determinedby
iile of vthis. patenti'
the frequency of said wave and oscillations of
said second source, and output means connected
to» said guide between said filtering means and
said second source.
5. A receiver for signals varying over a wide
range of ultra high frequencies comprising a wave
»guide of the hollow pipe type, a variable oscillator
connected to said guide at one of its ends andla 40
n 2,378,944
Ohl ____ __i ...... ..-v__- June 26, 1945
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