US2060142A - Demodulation circuit - Google Patents

Demodulation circuit Download PDF

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Publication number
US2060142A
US2060142A US700251A US70025133A US2060142A US 2060142 A US2060142 A US 2060142A US 700251 A US700251 A US 700251A US 70025133 A US70025133 A US 70025133A US 2060142 A US2060142 A US 2060142A
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United States
Prior art keywords
grid
frequency
cathode
carrier
voltage
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US700251A
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English (en)
Inventor
Urtel Rudolf
Steimel Karl
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Telefunken AG
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Telefunken AG
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Publication date
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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
    • H03D3/22—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal by means of active elements with more than two electrodes to which two signals are applied derived from the signal to be demodulated and having a phase difference related to the frequency deviation, e.g. phase detector
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
    • H03D1/00—Demodulation of amplitude-modulated oscillations
    • H03D1/14—Demodulation of amplitude-modulated oscillations by means of non-linear elements having more than two poles
    • H03D1/16—Demodulation of amplitude-modulated oscillations by means of non-linear elements having more than two poles of discharge tubes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits
    • H04B1/30—Circuits for homodyne or synchrodyne receivers

Definitions

  • the present invention relates to demodulating arrangements for receiving electromagnetic waves.
  • Demodulation necessitates the formation of the combination frequencies of carrier frequency and side-band frequencies in the case of modulated transmitters, and combination frequencies of the transmission frequency and heterodyne frequency in non-modulated transmitters. Formation of the combination frequency always occurs when a multiplicative effect of the two original voltages of dissimilar frequencies upon each other takes place. This is attainable most simply by that the incoming frequently mixture (spectrum) is brought to act upon a device with non-linear, preferably quadratic current-voltage relation. (Crystal detector, audion, diode, amplifying detector, etc.) All arrangements operating in this manner have certain inherent disadvantages which are obviated in whole or in part by the arrangement hereinafter to be disclosed. In the drawing:
  • Fig. 1 shows a signal demodulator network embodying the invention
  • Fig. 2 shows a modification thereof
  • Fig. 3 illustrates a further modification
  • Fig. 4 shows an embodiment of the invention applied to a heterodyne system
  • Fig. 5 shows a modification of the arrangement shown in Fig. 4.
  • Multiplicative action of two voltages upon one another is concerned, for instance, in the case of a multi-grid tube of such a nature that the slope of the plate-current characteristic referred to one of the grids (mutual conductance) is adjustable by the voltage of a second grid.
  • this holds good for space-charge grid tubes though what has to be put up with then is that the space-charge grid maintained at a positive potential will carry current, and thus consume energy.
  • a screen-grid tube which is equipped with an auxiliary grid I-I between plate A and the screen grid SI. The situation will be still further improved if between the said auxiliary grid and the plate there is disposed a second screen grid S2.
  • This arrangement offers the advantage over an audion that the amplitude that should be handled without incidentally any distortion being occasioned, may be very large, for there happens no shift in the static grid potentials, which, in an audion, give rise to additional harmful plate rectification.
  • this scheme offers the merit that the working point of both grids can be readily so posi-' tioned that with increasing amplitude the mean slope of the region covered will decrease, in other words, so that a smooth start of the oscillations in regenerative circuit arrangements is assured.
  • the amplitudes of the undesired transmitters contained in the incoming spectrum are reduced as far as feasible so that also the amplitudes of the ensuing undesired modulation frequencies will be small compared with the amplitude of the modulation frequencies of the desired transmitter.
  • the amplitude of a combination frequency is directly proportional to the product of the amplitudes of the two original frequencies.
  • the requisite reductions especially in the case of an unfavorable relationship of the field intensities (feeble transmitter and powerful disturber station) may be .secured, .a good deal of radio frequency selection must be provided, and this is an expensive proposition particularly when several circuits must be served simultaneously.
  • demodulation is effected in this manner that there is impressed upon one grid (of a tube satisfying conditions as outlined above) the incoming frequency spectrum, upon the second grid an alternating voltage of the frequency of the carrier wave of the desired transmitter, formation of a combination frequency will occur only between the carrier frequency, on the one hand, and theother frequencies of the incoming spectrum.
  • radio frequency selection will not be necessary. However, even .if, owing to not perfectly .linear modulation, undesired combination frequencies arise, then,by choosing a region of the characteristic being as straight as possible,
  • the amplitude of the undesired combination frequencies may be minimized in contrast with the amplitudes of the combination frequencies which result from the intentional multiplication of the incoming spectrum with the supplemental carrier voltage of the other grid, but especially also by choosing a large amplitude for the supplemental voltage.
  • the arrangement here described has selective properties, and it allows of doing away with a good deal, if not of all, of the selector means.
  • the supplemental carrier voltage should coincide with the alternating carrier wave contained in the incoming spectrum of the desired station not only as regards frequency, but also phase.
  • the ways and means of how to make this supplementary voltage available shall be set forth in more detail further below.
  • a demodulator network including a tube provided with a cathode, an anode, a screen grid which is maintained at a positive direct current potential with respect to the cathode and at the same alternating current potential as the latter, a signal control grid disposed between the cathode and screen grid, and an auxiliary electrode disposed between the screen grid and anode, an input circuit, tuned to the operating carrier frequency, connected between the cathode and signal grid, means for impressing energy of said carrier frequency upon said auxiliary electrode, said impressing means including a connection between said auxiliary electrode and a point of said tuned input circuit, an output network coupled between the cathode and anode for utilizing the demodulated currents, and means for maintaining both said signal grid and auxiliary electrode at a substantial negative direct current potential with respect to said cathode.
  • a demodulator network including a tube provided with a cathode, an anode, a positive screen grid, a signal control grid disposed between the cathode and screen grid, and an auxiliary electrode disposed between the screen grid and anode, an input circuit, tuned to the operating carrier frequency, connected between the cathode and signal grid, means for impressing energy of said carrier frequency upon said auxiliary electrode,
  • said impressing means including a connection between said auxiliary electrode and a point of said tuned input circuit, an output network coupled between the cathode and anode for utilizing the demodulated currents, and means for maintaining both said signal grid and auxiliary electrode at a substantial negative potential with respect to said cathode, said last means including an impedance disposed in the space current path of the tube, and both said signal grid and auxiliary electrode being connected to the anode side of the impedance.
  • a demodulator network including a tube provided with a cathode, an anode, a positive screen grid, a signal control grid disposed between the cathode and screen grid, and an auxiliary electrode disposed between the screen grid and anode, an input circuit, tuned to the operating carrier frequency, connected between the cathode and signal grid, means for impressing energy of said carrier frequency upon said auxiliary electrode, an output network coupled between the cathode and anode for utilizing the demodulated currents, and means for maintaining both said signal grid and auxiliary electrode at a substantial negative potential with respect to said cathode, said impressing means including an adjustable connection between the auxiliary electrode and the said input circuit, and a second positive screen grid between the anode and auxiliary electrode.
  • a demodulator network including a tube provided with a cathode, an anode, a positive screen grid, a signal control grid disposed between the cathode and screen grid, and an auxiliary electrode disposed between the screen grid and anode, an input circuit, tuned to the operating carrier frequency, connected between the cathode and signal grid, means for deriving the carrier frequency from the tuned input circuit and impressing the same upon said auxiliary electrode, an output network coupled between the cathode and anode for utilizing the demodulated currents, and means for maintaining both said signal grid and auxiliary electrode at a substantial negative potential with respect to said cathode.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • Superheterodyne Receivers (AREA)
US700251A 1932-12-27 1933-11-29 Demodulation circuit Expired - Lifetime US2060142A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2060142X 1932-12-27

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US2060142A true US2060142A (en) 1936-11-10

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Application Number Title Priority Date Filing Date
US700251A Expired - Lifetime US2060142A (en) 1932-12-27 1933-11-29 Demodulation circuit

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US (1) US2060142A (enrdf_load_stackoverflow)
NL (1) NL48758C (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2433361A (en) * 1940-01-20 1947-12-30 Submarine Signal Co Method and apparatus for echo ranging
US2436807A (en) * 1939-12-09 1948-03-02 Sperry Corp Electrical follow-up system
US2541066A (en) * 1943-11-24 1951-02-13 Sperry Corp Object detecting and warning system and method
US3009111A (en) * 1957-01-02 1961-11-14 Rca Corp Signal translating system
US3015069A (en) * 1956-11-07 1961-12-26 Rca Corp Oscillating in-phase detectors

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2436807A (en) * 1939-12-09 1948-03-02 Sperry Corp Electrical follow-up system
US2433361A (en) * 1940-01-20 1947-12-30 Submarine Signal Co Method and apparatus for echo ranging
US2541066A (en) * 1943-11-24 1951-02-13 Sperry Corp Object detecting and warning system and method
US3015069A (en) * 1956-11-07 1961-12-26 Rca Corp Oscillating in-phase detectors
US3009111A (en) * 1957-01-02 1961-11-14 Rca Corp Signal translating system

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Publication number Publication date
NL48758C (enrdf_load_stackoverflow)

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