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Патент USA US3084340

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April 2, 1963
E. H. HUGENHOLTZ
3,084,330
FREQUENCY CONVERTING CIRCUIT WITH MIXING ELEMENT IN
INPUT CIRCUIT OF AMPLIFYING DEVICE
Filed Nov. 10, 1959
I l f?m
2 Sheets-Sheet 1 _
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Hes
INVENTOR.
E. H. HUGENHOLTZ
BY
M/PW“
A GENT
Apnl 2, 1963
E. H. HUGENHOLTZ
3,084,330
FREQUENCY CONVERTING CIRCUIT WITH MIXING ELEMENT IN
INPUT CIRCUIT OF AMPLIFYING DEVICE
Filed NOV. 10, 1959
2 Sheets-Sheet 2
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INVENTOR.
E. H. HUGENHOLTZ
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3,034,339
lations being coupled to the mixing element. The input
radio frequency signal is also coupled to the mixing ele
ment where it is mixed with the signal at the given fre
quency to produce the intermediate frequency signal.
The intermediate frequency signal is coupled back to the
Eduard Herman Hugenhoitz, Toronto, (tartaric, Canada,
electronic amplifying device and is ampli?ed in this de
assignor to North American Philips Company, inc,
vice. A special advantage possible With this arrangement
New York, N.Y., a corporation of Delaware
is that the oscillator frequency determining circuit is lo
Filed Nov. 10, 1959, Ser. No. 852,954
cated
totally in the input circuit of the electronic ampli—
7 Claims. ((Zi. 32S—440)
10 fying device, eliminating the output to input local oscil
lation frequency determining circuit.
The invention relates to a frequency converting circuit
FREQUENCY CGNVERTKNG CERCUHT WKTH MEX
ING ELEMENT 1N lNi’UT (IIRQUHT ()F Ah’ii’Li
FYENG DEVICE
Since the mixing element may be a vacuum diode With
arrangement comprising a mixing element and a self
a separate cathode contained in the same envelope as the
oscillating electronic amplifying device. It has for its
electronic amplifying device when a tube is employed or
object to provide an improvement in gain and stability
15 a simple semiconductor diode When either a tube or a
over that found in self-oscillating mixer circuits.
transistor is employed as the amplifying device, the in
Self-oscillating mixer circuits are frequency converter
crease in cost is low and the added space required is circuits in which the mixing and oscillation functions are
extremely small. Therefore, the basic advantages of the
achieved by the same amplifying device, such as an elec
self-oscillating mixer, which are the use of few compo
tron tube or transistor. Although self-oscillating mixing
circuits provide economy of space and components, they 20 nents and low cost, are maintained.
The separate mixing element in this invention provides
also provide several disadvantages. Since the input cir
a separation of the signal at the given frequency from
cuit is connected to an oscillating electronic amplifying
the input circuit and thus reduces radiation of this signal.
device in aself-oscillating mixer, radiation of the oscil
The higher mixing efficiency of this separate mixing ele
lating signal at the given or local oscillator frequency
ment and the higher ampli?cation of the electronic ampli
through the input circuit may exceed tolerable limits and
fying device when it is not biased to mix provide a greater
as a result, special ?ltering may be required.
overall gain. In addition, the electronic ampiifying de
Another disadvantage of self-oscillating mixer circuits
vice provides less damping to the lower intermediate fre
is the low gain of the electronic amplifying device which
quencies and therefore provides an even greater gain.
is a result of the biasing or operating point at which the
Due to the separation of the circuit containing the
electronic amplifying device is set to permit it to mix
oscillations of the local oscillator frequency and the elec
satisfactorily. In addition, the input circuit of the elec
tronic amplifying device provides high damping of a sig
nal at a high value of radio frequency, which further
reduces the gain of the system.
A ‘further disadvantage of self-oscillating mixer cir- 9
cuits is the tendency for the oscillations of the local
oscillator to be pulled or blocked entirely by a strong
tronic amplifying device provided by the separate mix
ing element, frequency pulling and blocking of the oscil
lator is substantially reduced. In addition, this separa
tion also enhances the stability of the oscillator as the
tuning circuit for the oscillator is varied.
Since the local oscillator frequency determining cir
cuit is located totally in the input circuit of electronic
input radio frequency signal. Blocking or frequency
amplifying device, adjustment of the tuned circuits in the
pulling of the local oscillator is particularly noticeable
when a receiver employing a self-oscillating mixer circuit 40 output and input of the electronic amplifying device will
have less effect on each other and thus facilitate their
is tuned to a weak or distant station with a strong local
individual tuning.
station occupying the adjacent channel.
Self-oscillating mixers generally exhibit a tendency to
In order that the invention’ may be readily carried into
effect, it will now be described in greater detail with ref
erence to the accompanying drawing, in which:
FIG. 1 is a block diagram of a frequency converting
wards instability of the local oscillator when the tuned
circuit for the input radio frequency signal is varied.
This is due to the inherent coupling of the tuned circuit
for the input signal and the tuned circuit for the local
oscillator.
In order to prevent positive or negative feedback of the
circuit according to the invention;
FIG. 2 is a circuit diagram illustrating one embodi
ment of the invention;
FIG. 3 is a circuit diagram of a portion of the circuit
intermediate frequency and still permit ampli?cation at 50
of FIG. 2. illustrated as a bridge circuit;
this frequency, it has been generally necessary to employ
FIG. 4 is a circuit diagram illustrating another em
an oscillator which utilized a frequency determining cir
bodiment of the invention;
7
cuit which compels the oscillator to oscillate at the given
FIG. 5 is a circuit diagram of a portion of the circuit
frequency connected between the output and input of the 55
of FIG. 4'illustrated as a bridge circuit;
,
electronic amplifying device or between plate and grid,
FIG. 6 is a circuit diagram of still another embodi
when a tube is used as the electronic amplifying device,
ment of the invention; and , t ,
.
in order to permit the signal at the second value of he
FIG. 7 is a circuit diagram ,of a portion of the circuit
quency to be connected to'the input or grid, and yet not
of FIG. 6 illustrated as a bridge circuit.
.have the ampli?ed signal at the second value of fre—
FIG. 1 shows a block diagram of the invention in which
quency at the plate fed back through the given frequency 60
the input terminals iii of the mixing element 11 receive
circuit to the grid. When a circuit is connected between
the input radio frequency signals. The electronic amplify
the input and output of the electronic amplifying device, 1
ing device 12;, which is adapted to oscillate at a given
a greater interaction of the input and output tuned cir
cuits takes place, making the individual adjustment of
any one of these circuits di?icult.
frequency, is coupled to the mixing element 11 through
\ 65 coupling 13 to permit the signal at the'given frequency to
The frequency converting arrangement according’ to‘v
this invention mitigates the previously mentioned disad
vantages of self-oscillating mixer circuits by carrying out
be conveyed to the mixing'clement l1 Where it mixes
with the input radio frequency signals to produce the inter
mediate frequency signals. The intermediate frequency
signals are coupled to the electronic amplifying device 12
in the input circuit of the electronic amplifying device. 70 through the coupling 13. The ampli?ed intermediate fre
quency signals are derived at the output terminals 14 of
In this arrangement the amplifying device is adapted to
the electronic amplifying device 12.
oscillate at the local oscillation frequency, the local‘ oscil
the mixing process in a separate mixing element located
3,084,330
3
4
FIG. 2 illustrates an embodiment of the invention which
capacitors C17, ‘C14, C15, C18, C15 and C19 and
employs a semiconductor diode D1 as the mixing element
pentode T2 form an oscillator at a given frequency. The
signal at the given frequency across L4 is coupled to the
and a vacuum ‘tube triode T; as the electronic amplifying
device. 'In this ‘circuit the radio frequency signal is
diodes through capacitors C17 and ‘C18 where it mixes the
input signal to produce theintermediate frequency which
coupledfrom inductor L1 to inductor L2. ‘ L2‘ and C3 are
resonant at thefrequency of the input signals and the
is impressed across a circuit tuned to this frequency and
radio frequency signals are impressed on semiconductor
composed of inductor L3 in conjunction with capacitors
diode D1; Inductor L4 in conjunction with the triode T1
C17, C18, C14, C15 and C16. The intermediate frequency
and capacitors C6, C3-C8 and’ the input capacity of T1
signal across inductor L3 is coupled through the direct
form a Colpitts, oscillator which is adaptedto oscillate 10 current blocking capacitor C14, to‘the control grid of the
at a, given frequency. Since the oscillator oscillations are
pentode T2 where it is ampli?ed.
generated across the inductor L4, they are'also impressed
The ampli?ed versionof the intermediate frequency
on diode D1 through capacitor C5. Theinductor L3 in
signal is derived across the plate tuned circuit comprised
conjunction with C6, C7, C8 and the input capacitylof
principally of inductor L5, capacitor C20, and the output
the triode T1 form a resonant circuit at the intermediate 15
capacity of tube ‘T2. The-ampli?ed intermediate frequency
signal ‘is coupledv from‘ inductor L5 to inductor L5. In~
FIG. 3 illustrates a portion of, the circuit of FIG. 2 as
ductor' L5, capacitor C23 and the input capacity of the
a bridge circuit, wherein the alternating component of
amplifying device of. the next, stage form the input tuned
Cathode current is fed around inductor L3 through, two
circuit at the intermediate frequency for the next stage.
paths. The ?rst path is through C7 and C8 and the second 20 The bridge circuit ofFIG. 5 is a portion of the circuit
is through C6+Cgk and 'C5+L4. C5+L4form at the
of FIG. 4 in bridge form; This circuit illustratesfthe
intermediate frequency an effective capacitance designated
means by which oscillation at the intermediate frequency
C5’. The ratio of Cq-l-Csk to C5’ is equal. to the ratio of
is prevented. The ratio of capacitor C15 to capacitor C18
is chosen equal tothe ratio ofcapacitor C16 to capacitor
O; to C8. in this way, the cathode current forms no feed
back voltage across L3 and, therefore, the electronic 25 C“. In this way no intermediate frequency component ‘of
amplifying ‘device does not oscillate atthe intermediate
the cathode current is impressed across inductor L3 and
frequency. C9 has the function in this circuit of neutraliz
therefore there is no feedback at the intermediate fre
frequency.
'
'
'
'
’
ing the plate to grid capacity Cpg.
"
'
quency.
Although the bridge circuit prevents oscillation, at the
FIG. 6 illustrates a modi?cation ‘of the frequency con~
intermediate frequency, the signal of the intermediateffre
quency is coupled throughothe direct current blocking
condenser C4 to the gridof the electronic‘ amplifying de
30 verter of FIG. 2, utilizing a transistor Spas the electronic
amplifying device, and a semiconductor diode D1 asgthe
mixing‘elementi FIG. 7 ~illustrates the bridge'lcircuit of
the circuit of FIG. 6, which prevents oscillation at the
intermediate frequency. The principle of operation of the
The ampli?ed version of :the- signal at. the intermediate 35 circuit'of FIGS. 6 and 7 is identical to thatlof FIGS. 2
‘and 3 with the exception of the standard biasing arrange
frequency is coupled from L5 to input of the next stage
vice wherein it isampli?ed andrderived at the tuned cir
cuit comprised of L5, C10 and the output capacity of T1.
which is comprised of L6 and C13. '
i
ment required for the transistor.
V
‘
'
,While the invention has been described by means of
speci?c examples and in speci?c embodiments, I do not
the diode D1. R2 serves as a direct current return for
the grid of T1. R3 serves in place of a choke to maintain 40 wish to be limited thereto, for‘obvious modi?cationswill
occur to those skilled in the art without departing from
the cathode of T1 at. an alternating potential above
the spirit and scope of the invention. '
ground. R4 serves to de-couple the direct current plate
In this circuit, R1 serves as a direct current return for
supply voltage for T1.’ C11 and C12 serve to place the '
lower connections ofoL's and L?atalternating current
ground.
-
I’
'
Purely by way of illustration and in no sense by way
said input electrode and said point of reference potential,
means respectively connecting said common electrode to
Capacitor C3 ________ _..___. V4.7 ,u/tf.
said tuned circuit whereby local oscillations are generated,
Capacitor C4 ____________ _. 1000 [.t/Lf.
Capacitor C5 ____________ _. 6.8 Intf.
50 a source'of'high frequency osciliations, a imixing device
having ?rst and second terminals, means connecting said
Capacitor C6 ______ __'____... 4 n/if.
source between said ?rst terminal and said point of refer
Capacitor C7 ____________ _. 6.8 uni.
ence potential, means connecting ‘said second terminal to
Capacitor C8__r__'_ _____ __‘ 10 ,upsfp
‘said input electrode .Whereby said high frequency oscil
Capacitor C9 ____________ _. l ,uuf.
55 lations and local oscillations are mixed in said mixing de
l-O ,lL/Lf.
_
1000 p/rf.
120 ,u/tf.
.10 ,unf.
1.5K ohms.
vice to provide oscillations of an intermediate‘frequency
and said‘ intermediate frequency ‘oscillations are applied
to said input electrode, and outputcircuit tmeansrconnected
to‘said output electrode to derive ampli?ed intermediate
60
Resistor R2 _____________ -.' 100K ohms.
Resistor R3 __________ _'____ 1500 ohms.
’Device T1 ______________ __ Tube 6ER5.
frequency oscillations therefrom.
.
'
2. The circuit of claim 1 in which said mixing. device
comprises a pair of diodes connected‘in a‘ balanced cir
,
Device D1 ______________ _. Germanium diode 1N87A.
Inductor L1 _________ ______. 1.7 uh.
Inductor L2 ________ __o____. 1.5 ah.
cuit.
-
FIG. 4 illustrates a frequency converter which utilizes
two diodes in a balanced mixer circuit, and a pentode in’
the oscillator-ampli?er. circuit. :Inductor L1 couples'the
'radio frequency signalto the semiconductor diodes D2
and D3 through inductor L2. Inductor L4 in conjunction
'
-
’
3. The circuit of‘claim 1 in which said amplifying de
65 vice is an electron discharge tube.
‘
'
4. The circuit of claim 1 in which said amplifying de
vice is a transistor having ‘base, emitter and collector elec~
trodes, said input, common and output electrodes‘ com
Inductor Lam ___________ _. 1.1 ,uh.
Inductor L4_...__'_________ _. _0.4 ch. 7
Inductor L5 ___________ __._. 1.1 uh.’
,
ence potential, tuned circuit means connected between
be employedin the circuit of FIG. 2:
Cm ________ __'___
C11 ___________ __
Cm ___________ _C13 ____________ _
Resistor R1 _____________ __
'
l. A frequency converting circuit comprising an ampli—
fying device having at least an‘input electrode, a com
45 mon electrode, and an output electrode, a 'point of refer
of limitation, the following circuit component valuesmay
Capacitor
‘Capacitor
Capacitor
Capacitor
What I claim is:
prising said base,‘ emitter and collector electrodes, respec
70
tively.
'
5. A frequency converting circuit comprisingv an elec
tron discharge tube having‘cathode, control ‘grid, and
anode electrodes, impedance means connecting said cath
ode to ground, a local" oscillation frequency determining
75 circuit regeneratively connected to said tube for provid
3,084,330
5
ing local oscillations comprising ?rst and second serially
connected capacitors connected in parallel with ?rst in
ductance means between said control grid and ground, and
means connecting the junction of said capacitors to said
cathode, a source of high frequency oscillations, a diode
mixing ‘device, means applying said high frequency oscil
lations to said mixing device, and means connecting said
mixing device to said control grid electrode whereby said
local oscillations and high frequency oscillations are
mixed in said mixing device to provide intermediate oscil
lations, and said intermediate oscillations are applied to
the control grid electrode of said discharge tube.
6. A frequency converting circuit comprising an elec
6
mixing device to said control gn'd electrode whereby said
local oscillations and high frequency oscillations are
mixed in said mixing device to provide intermediate oscil
lations, and said intermediate oscillations are applied to
the control grid electrode of said discharge tube.
7. A frequency converting circuit comprising an ampli
*fying device having at least an input electrode, an output
electrode, and a common electrode, a source of high fre
quency oscillations, diode means having ?rst and second
terminals, ?rst tuned circuit means connected between said
input electrode and a point of reference potential, second
tuned circuit means connected between ‘said input e1ec~\
trode and point of reference potential, bridge means con
necting said common electrode to said ?rst and second
tron discharge tube having cathode, control grid, and
anode electrodes, impedance means connecting said cath 16 tuned circuits to provide self-generated local oscillations
of the frequency of said ?rst tuned circuit and to prevent
ode to ground, a local oscillation frequency determining
circuit regeneratively connected to said tube for provid
self-oscillations at the frequency of said second tuned cir
cuit, means connecting said source of high frequency
ing local oscillations comprising ?rst, second and third
oscillations between said ?rst terminal and said point of
serially connected capacitors connected in parallel with
reference potential, means connecting said second terminal
?rst inductance means between said control grid and
to said input electrode whereby said high frequency and
ground, means connecting the junction of said ?rst and
local oscillations are mixed in said diode means to pro
second capacitors to said cathode, intermediate frequency
duce intermediate frequency oscillations that are applied
determining means non-regeneratively connected to said
to said second tuned circuit and input electrode, said
tube comprising second inductance means connected in
parallel with said ?rst and second capacitors, a fourth 25 second tuned circuit being tuned to the frequency of said
intermediate oscillations, and output circuit means for
capacitor, means serially connecting said fourth capaci
deriving ampli?ed intermediate frequency oscillations
tor and third capacitor in parallel with said second in
from said output electrode.
ductor, neutralizing capacitor means connected between
said anode and the junction of said second and third ca
References Cited in the ?le of this patent
pacitors, a source of high frequency oscillations, a diode 30
UNITED STATES PATENTS
mixing device, means applying said high frequency oscil
lations to said mixing device, and means connecting said
2,789,215
Pan ________________ __ Apr. 16, 1957
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