US2282910A - Variable frequency detector system - Google Patents

Variable frequency detector system Download PDF

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Publication number
US2282910A
US2282910A US363744A US36374440A US2282910A US 2282910 A US2282910 A US 2282910A US 363744 A US363744 A US 363744A US 36374440 A US36374440 A US 36374440A US 2282910 A US2282910 A US 2282910A
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Prior art keywords
balanced
circuit
frequency
output
impedance
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Expired - Lifetime
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US363744A
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English (en)
Inventor
Leland E Thompson
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RCA Corp
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RCA Corp
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Priority to NL60191D priority Critical patent/NL60191C/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US363744A priority patent/US2282910A/en
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
    • H03D3/02—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal
    • H03D3/06—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal by combining signals additively or in product demodulators
    • H03D3/08—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal by combining signals additively or in product demodulators by means of diodes, e.g. Foster-Seeley discriminator

Definitions

  • This invention relates to detector systems for frequency modulated and other variable frequency signals including a frequency discriminator network and a balanced rectifier output circuit from which audio frequency signals and control potentials resulting from frequency variation or signal modulation are taken.
  • the figure is e a schematic circuit diagram of a variable frequency detector system embodying the invention, and having as a signal source the output amplifier stage of an intermediate frequency am plifier.
  • the system of the present example is coupled to the amplifier output circuit 6 by means of two primary windings 1 and 8, in series and A circuit of this type is effective to prevent the transmission of amplitude modulated signals and amplitude variations of a frequency modulated signalgp rovided that the center or carrier frequency' of a received signal does not vary or drift and provided that the tuning of the circuits'l3 and i4 does not vary or drift.
  • both the center frequency of a recoupled to corresponding secondary windings 9 and It which are tuned to resonance above and below a predetermined center frequency by suitable tuning capacitors indicated at H and I2.
  • the two tuned frequency discriminator circuits I3 and I4 are connected to balanced rectifier means comprising a tube I5 having an anode l6 connected with the high potential terminal I! of the circuit I3 and having a second anode l8 connected with the high potential terminal IQ of the circuit M.
  • the low potential terminals of the tuned circuits Hi and I4 are connected to a common low potential lead 26 which, in turn, is connected to the center tap 2
  • This circuit arrangement provides one wellwhich the output potentials vice or tube, the value of by'suitable control electrode means.
  • ceived signal and the tuning of the signal circuits may change for various reasons, such as temperature change in certain of the circuit components, both at the signal source and at the receiver. 7
  • this tendency' to drift is compensated in the output network of the detector system to maintain a resistanceor a voltage balance effective to prevent transmission of amplitude modulated signals and amplitude variations of a variable frequency signal therethrough.
  • a dual amplifier tube 35 is provided with a tube element comprising a cathode 36, a control grid 37 and an anode 38 connected respectively to the center terminal 2
  • a second tube element comprising a cathode 4
  • the control grid connection in each-casein includes a filter resistor 46 and filter capacitor 41 providing a-predetermined time constant for the which is controllable 1 application of potentials to the control grids and 55 connected between the terminals and v 2
  • They may, however, comprise any suitable impedance elements or may be provided as a sin- V gle unit having taps thereon as shown?
  • the circuit arrangement is such. that a porput resistor network is shunted by the anodecathode impedance of a tube element of the tube 35.
  • the anode-cathode impedance 3638 is connected in shunt across the resistor sections 5
  • -44 is connected across the resistor sections 54 and 55 between the terminals 45 and 2
  • the signal output from the balanced network is taken from suitable points in balanced relation to each other on opposite sides of the center tap 2
  • the output circuit is connected to an amplifier circuit such as an audio frequency amplifier stage 64 comprising an amplifier tube 65 havin a control grid 66 coupled through a capacitor 61 with the lead 62 and having a cathode 68 connected through a bias resistor 69 with the output lead 60,
  • Thesignal output from the amplifier stage is taken through the anode circuit indicated at 10.
  • the circuit shown operates to maintain a voltage balance of the undesired amplitude modulation resulting therefrom, the amplitude modulation being either noise voltages or an interfering heterodyne signal.
  • the operation of this circuit is as follows:
  • '6--26 comprises the resistor sections 50, 5
  • comprises the resistor sections 53, 54 and 55, together with the balancing capacitor 3
  • are adjusted to obtain the same phase relationship between current and voltage in the two balanced diode circuits or branches 22 and 23.
  • and 45 may be adjusted by means of the contact 63 to be substantially equal and out of phase, so that these voltages cancel and do not appear on the output circuit between the terminals 63 and 45, and hence are not amplified through the output stage 64.
  • the current through branch 22, for example may be assumed to increase while that through the branch 23, under the same assumption, will decrease. connected at points 39 and 43, with signal rectification both grids will assume a positive potential, with respect to the cathodes, which will increase on the grid 31 and decrease on the grid 42 under the condition of unbalance.
  • will decrease, while the anode circuit resistance between the terminals 45 and 2
  • the frequency discriminator network provides a balanced output circuit for maintaining a resistance or voltage balance therein effective to prevent the transfer therethrough of output voltages resulting from amplitude modulated signals or amplitude variations of a frequency modulated signal or carrier wave.
  • a variable frequency detector system comprising, in combination, a frequency discriminator network and rectifier means in balanced relation thereto for the detection of variable frequency signals, means including a series of impedance elements having a common center output terminal and two end terminals providing a balanced output circuit for said rectifier means, an electric discharge device having the anodecathode impedance thereof connected between said common terminal and an intermediate tap on either side thereof in connection with said series connected impedance elements, a control grid for each of said anode-cathode impedances connected on either side of said center terminal, and means providing a balanced signal output connection with said series connected impedance elements on either side of said center terminal.
  • a variable frequency detector system comprising, in combination, a frequency discriminator network and balanced rectifier means for the detection of variable frequency signals, means providing a balanced output impedance network.
  • means comprising two series for said rectifier branch circuits having a common center tap and two outer terminals, electric discharge tube elements for controlling the impedance of each of said branch circuits having cathodes connected with said center tap and having anode elements connected at points on said branch circuits intermediate between said center and outer terminals to provide the anode-cathode impedance of said tube elements in balanced relation across a portion of each of said branch circuits, a control grid for each of said means providing a control grid connection from each of said grids to the respective branch circuit across which the anode-cathode impedance controlled thereby is connected at a point intermediate between the anode connection therefor and the common center terminal.
  • a variable frequency detector system comprising, in combination, a frequency discriminator network, rectifier means connected with said network in balanced relation thereto, means providing a balanced output circuit for said last tube elements, and
  • rectifier means including a series of impedance elements connected on either side of a common output terminal, means providing balanced output circuit connections including certain of said impedance elements on "opposite sides of said common output terminal, electric discharge control means having cathode elements connected with said common output terminal and having anode elements connected in balanced relation to each other on opposite sides thereof with said series connected impedance elements, and means providing control grid connections for said electric discharge control means on opposite sides of said common output terminal for maintaining a resistance and voltage balance in said output circuit to'fprevent the transfer therethrough of output voltages resulting from amplitude modulated signals and amplitude variations of a frequency modulated signal in said network.
  • a variable frequency detector system comprising, in combination, means for amplifying received variable frequency signal energy, means for detecting said signal energy comprising detecting circuits connected in balanced opposition to amplitude modulated signals andin cut-ofphase relation to variable frequency signals, a balanced output circuit for ergy, means in said circuit for maintaining a predetermined phase relation between current and voltage in the detected signal energy in said output circuit, and means for changing the impedance of the branches circuit in response to amplitude variations in the substantially constant.
  • a detector for variable frequency signals means for eliminating amplitude modulated signals and disturbances which comprises two detector circuits connected in opposition to amplitude modulated signals and inout-of-phase relation to variable frequency signals, an input circuit for applying received signals to said detector circuits, a balanced output circuit for said detectors including impedance elements for maintaining thesame phase relation between current and voltagein the outputs of said circuits, and a variable impedance element in shunt relation to at least a portion of each branch of said balanced output circuit responsive to the carrier voltage input to said detector circuits for changing the impedance in said output circuit branches to maintain the signal amplitude equal therein.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)
US363744A 1940-10-31 1940-10-31 Variable frequency detector system Expired - Lifetime US2282910A (en)

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NL60191D NL60191C (en)) 1940-10-31
US363744A US2282910A (en) 1940-10-31 1940-10-31 Variable frequency detector system

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2422083A (en) * 1942-03-20 1947-06-10 Rca Corp Frequency modulation receiver
US2429771A (en) * 1942-09-26 1947-10-28 Rca Corp Frequency responsive remotecontrol system
US2446077A (en) * 1945-05-02 1948-07-27 Press Wireless Inc Frequency-shift telegraph system
US2478977A (en) * 1944-11-13 1949-08-16 Colonial Radio Corp Signal seeking receiver for frequency modulated signals
US2511448A (en) * 1946-03-21 1950-06-13 Rca Corp Angle modulation detector
US2607890A (en) * 1948-03-04 1952-08-19 Stewart Warner Corp Variably sensitive frequency discriminator
US2662179A (en) * 1946-12-04 1953-12-08 Philips Nv Circuit-arrangement for receiving and detecting frequency modulated oscillations
US2710350A (en) * 1952-10-13 1955-06-07 Hartford Nat Bank & Trust Co Ratio detector circuit for frequencymodulated oscillations

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2422083A (en) * 1942-03-20 1947-06-10 Rca Corp Frequency modulation receiver
US2429771A (en) * 1942-09-26 1947-10-28 Rca Corp Frequency responsive remotecontrol system
US2478977A (en) * 1944-11-13 1949-08-16 Colonial Radio Corp Signal seeking receiver for frequency modulated signals
US2446077A (en) * 1945-05-02 1948-07-27 Press Wireless Inc Frequency-shift telegraph system
US2511448A (en) * 1946-03-21 1950-06-13 Rca Corp Angle modulation detector
US2662179A (en) * 1946-12-04 1953-12-08 Philips Nv Circuit-arrangement for receiving and detecting frequency modulated oscillations
US2607890A (en) * 1948-03-04 1952-08-19 Stewart Warner Corp Variably sensitive frequency discriminator
US2710350A (en) * 1952-10-13 1955-06-07 Hartford Nat Bank & Trust Co Ratio detector circuit for frequencymodulated oscillations

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Publication number Publication date
NL60191C (en))

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