US2237457A - Aperiodic disturbance suppression circuits - Google Patents

Aperiodic disturbance suppression circuits Download PDF

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Publication number
US2237457A
US2237457A US261257A US26125739A US2237457A US 2237457 A US2237457 A US 2237457A US 261257 A US261257 A US 261257A US 26125739 A US26125739 A US 26125739A US 2237457 A US2237457 A US 2237457A
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voltage
diode
voltages
frequencies
resistance
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US261257A
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English (en)
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Bernardus D H Tellegen
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RCA Corp
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RCA Corp
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G11/00—Limiting amplitude; Limiting rate of change of amplitude
    • H03G11/04—Limiting level dependent on strength of signal; Limiting level dependent on strength of carrier on which signal is modulated
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers
    • H03G3/20—Automatic control
    • H03G3/22—Automatic control in amplifiers having discharge tubes
    • H03G3/26—Muting amplifier when no signal is present

Definitions

  • Such a device may not be actuated, as a matter of course, by the desired signal, and it has, therefore, been proposed to construct the device in such manner that it only responds to disturbance amplitudes 10. which are larger than double the carrier wave amplitude of the desired signal, for with a modulation depth of 100% the maximal signal amplitude is equal to double the carrier wave amplitude. Only disturbance voltages larger than douj ble the carrier wave amplitude can actuate the said device, and thus block up the low frequency amplifier.
  • the invention has for its object to provide a device which permits the elimination of at least part of the interfering voltages which are smaller than twice the carrier wave amplitude.
  • this purpose is attained by supplying the received high, intermediate, or low frequency oscillations to an auxiliary channel which includes a filter which does not pass at least the carrier wave and those sideband frequencies of the high, or intermediate, frequency oscillations which correspond to the lowest modulation frequency, or the lowest modulation frequencies of the low frequency oscillations respectively, while after a determined threshold value has been surpassed the voltages of the remaining frequencies actuate a device for making the low frequency amplifier inoperative.
  • the filter included in th auxiliary channel may,
  • the filter included in this channel may be a low, or a high, pass filter.
  • the voltages of the remaining frequencies are preferably supplied to a biased rectifier, so that they are not rectified until a determined threshold value has been surpassed, and are supplied as a control direct current voltage to the said device for making the low frequency amplifier inoperative.
  • the voltages of the remaining frequencies are rectified and supplied as a control direct current voltage to the device for making the low frequency amplifier inoperative, in such manner that this device starts operating as soon as the said control direct current voltage surpasses a determined threshold Value.
  • the invention affords the possibility of suppressing part of the disturbances which are smaller than double the carrier wave amplitude, since the device for making the low frequency amplifier inoperative can now be actuated by disturbance voltages which are larger than the signal voltages furnished by the high modulation frequencies which are located, for example, over 2500 cycles per second, which signal voltages are considerably smaller than double the carrier wave amplitude.
  • the modulation depth of the frequencies over 2500 cycles per second is under ordinary conditions at the most about 10%. If the auxiliary channel is branched from the high, or intermediate, frequency amplifier, th carrier Wave as well as the frequency corresponding to the lowest modulation frequency have to be suppressed in this auxiliary channel. Use may be made for this purpose of a band-blocking filter,
  • one of the side-bands of the received signal comprises frequencies which originate from a transmitter adjacent as to frequency
  • the voltages, more particularly those of the side-band frequencies corresponding to the high modulation frequencies have a higher value so that the threshold below which disturbance can no longer be eliminated also comes to lie at a higher level.
  • Fig. 1 represents diagrammatically, by way of example, one embodiment of a radio receiver having disturbance elimination according to the invention
  • Fig. 2 represents a practical example of the circuit arrangement of such a receiver
  • Fig. 3 represents a circuit arrangement for limiting the threshold voltage.
  • the high frequency oscillations collected by an aerial I are supplied to a high frequency amplifier 2 comprising a mixing tube and, after amplification and frequency transformation, they are passed through to an intermediate frequency amplifier 3 provided with a detector. In the latter the intermediate frequency oscillations are detected, and supplied to a low frequency amplifier 5 whereupon the low frequency oscillations are made audible by a loudspeaker 6.
  • a control voltage for automatic volume control (AVG) is supplied through a conductor l to the intermediate frequency amplifier and to the high frequency amplifier.
  • the intermediate frequency amplifier has conected to it a filter 1 Which does not pass the carrier wave and the sideband frequencies which correspond to the low modulation frequencies.
  • This filter is followed by a device 3 adapted to operate, with the aid of a relay 9, a switch iii present in the low frequency amplifier 5.
  • This device can be actuated by voltages which pass through the filter I and is connected through a conductor I l to the intermediate frequency amplifier 3 in order to be able to adjust the threshold value which the disturbing voltages have to exceed in order to allow of their being suppressed.
  • Fig. 2 shows this device in detail. Similar components are denoted in Fig. 2 by the same numerals as in Fig. l.
  • the high frequency oscillations received by an aerial i are transformed in known manner by a mixing tube 42 into intermediate frequency oscillations and supplied, through an intermediate frequency band-pass filter E3, to an intermediate frequency amplifying tube Id.
  • the oscillatory circuit l5 of a second intermediate frequency band-pass filter IT is included in the oscillatory circuit l5 of a second intermediate frequency band-pass filter IT.
  • This circuit is connected, through a condenser Hi, to a diode anode [9 arranged in a low frequency amplifying tube 29 and, through condensers 23 and 24, to the cathode 25 of this tube.
  • rectification there is set up across a resistance 20 a control direct current voltage which is supplied, through a filter formed by a resistance 2
  • the oscillatory circuit l6 of the intermediate frequency band-pass filter i1 is connected, on the one hand, to a diode anode 26 which is also incorporated in the amplifying tube 29 and, on the other hand, through the parallel connection of a condenser 2'5 and a resistance 28, to the cathode of the amplifying tube 23.
  • the low frequency voltages set up, by detection, across the resistance 28 are supplied, through a slide contact 30 and a condenser 33, to the control grid 32 of the amplifying tube 29.
  • a control voltage for a cathode ray indicator which is not shown in the figure is taken from the resistance 28 through a filter formed by a resistance 33 and a condenser 34.
  • the amplifying tube 29 is connected, through a filter consisting of a resistance 35 and a condenser 3t and through a switch [0, to the control grid 31 of a final amplifying tube 38, which control grid receives, through a resistance 39, a negative bias voltage.
  • a loudspeaker 6 is connected, with the interposition of a transformer 4%, in the anode circuit of the final amplifying tube 33.
  • the switch it is operated by a relay 9 and is constructed in such manner that when the current passing through the relay 9 decreases the contact is broken and the low frequency amplifier is made inoperative.
  • the intermediate frequency band-pass filter l3 has furthermore connected to tube 4! is connected through a condenser 44 to the filter 1.
  • This filter consists of a parallel resonance circuit 45 which is grounded on either side through series resonance circuits t5 and 41.
  • the circuits 45, 46 and 47 are tuned to the intermediate frequency carrier wave.
  • the anode of the amplifying tube I 4 is connected, through a condenser 48, to a diode anode 49 while the end of the filter l is connected through a condenser 50 to a diode anode 5!.
  • the two diode anodes 49 and 5! form, together with a cathode 52, a duo-diode 53.
  • the cathode 52 is connected to ground through the parallel connection of a resistance 5% and a condenser 55.
  • are grounded through, resistances 56 and 57 respectively.
  • the two diode anodes l9 and 26 present in the low frequency amplifying tube 29 provide, as has been described before, in known manner, for the detection and the automatic volume control.
  • the low frequency alternating voltages set up across the resistance 35 connected in the anode circuit of the amplifying tube 25 are supplied, through a separating condenser 56 and a switch which is closed during normal reception, to the control grid 31 of the final amplifying tube 38 by which they are amplified and then they are reproduced by the loudspeaker 6i.
  • only passes the intermediate frequency sideband frequencies which correspond to the highest modulation frequencies.
  • the diode 49-52 present within the duo-diode tube 53 receives intermediate frequency voltage from the anode circuit of the amplifying tube 14. Since the diode Iiifor the automatic volume control is also connected to this anode circuit this intermediate frequency voltage is substantially constant.
  • the current supplied by the diode 49-52 passes not only through the resistance 56 but also through the resistance 54, the latter having, jointly with the condenser 55, such a time constant that the said current only depends on the intensity of the carrier wave of the received signal.
  • the voltage set up by this current across the resistance 54 consequently constitutes for the. diode 54-52 a bias Voltage which depends on the carrier wave.
  • the intermediate frequency sideband frequencies which correspond to the high modulation frequencies. Since the amplifying tube 41 has substantially the same characteristic as the amplifying tube l4, the ratio between the voltages supplied to the two diodes 49-52 and 5I-52 remains substantially independent of the intensity of the desired signal, The values of the resistances 54 and 56 are so chosen that the bias voltage of the diode 5l-52 exceeds the normal intermediate frequency side-band frequencies corresponding to the high modulation frequencies. Under normal conditions the diode 5I-52 consequently does not rectify, so that the control grid 6d of the tube 6
  • Fig. 3 represents a circuit arrangement wherein the threshold value over which disturbance elimie nation takes place, is dependent on the side-band frequencies which correspond to the high modu: lation frequencies, and wherein this threshold value is limited by the carrier wave of the desired signal. In this case the threshold value is at any instant not larger than is absolutely necessary, and moreover, it cannot exceed a determined limit.
  • the threshold value is at any instant not larger than is absolutely necessary, and moreover, it cannot exceed a determined limit.
  • are connected to the band: blocking filter I through condensers 43 and 56 respectively.
  • the direct current circuit for the diode 49-52 is formed by series connected resistances 54; and 56. Across the resistance 54 there is set up a direct current voltage which forms a threshold voltage for the diode 5l-52.
  • the value of the alternating voltage supplied through the condenser 50 to this diode is ad; justed with the aid of this condenser in such manner that in the case of normal reception rectification does not yet occur in the diode 5l-52. When a disturbance is received, the latter will. be rectified and in the manner above describedit causes the control grid 69 .of tube 6
  • the circuit arrangement of Fig. 3 further come, prises a duo-diode 65.
  • the diode anode EBthereof is connected to the cathode 52 of the first duo-. diode 53.
  • the other diode anode 61 is connected to ground through a coil 68,
  • the cathode 691s grounded through the parallel connection of a resistance 70, which is small relatively to the resistance 54, and of a condenser H.
  • the duodiode 65 has for its task to limit the value of the threshold voltage of the first duo-diode 53, for if there occurs a series of successive disturbances, the threshold voltage across the resistance 54 gradually increases with the result that the level above which the disturbances cause the low frequency amplifier to become inoperative, also rises. Owing to the limitation of the threshold value this level is also limited. If the voltage across the resistance 54 exceeds a determined value which is determined by the positive voltage of the cathode 69 of the duo-diode 65 with respect to ground, the diode 66-69 becomes conductive with the result that the resistance 10 in series with the diode 66-69 is connected in parallel with the resistance 54.
  • This parallel connection causes in series with the resistance 56 such a division of the direct current voltage existing across the diode 49-52 that the amplitude of the disturbing voltages which give rise to the initial rise of the threshold is larger than the partial voltage across the parallel connection of the resistances 56 and 16, so that these interfering voltages are suppressed,
  • the positive voltage which the cathode 69 of the duo-diode 65 has with respect to ground is determined by the value of the alternating voltage existing between the diode anode 6'! and ground, which alternating voltage may inductively be taken, for example with the aid of an inductance coil 66, from the oscillatory circuit 15 which is included in the anode circuit of the amplifying tube l4.
  • a side band modulated carrier receiving system of the type provided with a carrier demodulator and a demodulation voltage utilization. network
  • the improvement which comprises a network for deriving from the carrier voltage prior to demodulation voltage of side band component frequencies corresponding to higher modulation frequencies, means for rectifying the derived voltage, means responsive to the carrier amplitude for controlling the operation of said rectifying means, and means responsive to the rectified voltage for controlling the said utilization network.
  • a side band modulated carrier receiving system of the type provided with a carrier demodulator and a demodulation voltage utilization network
  • the improvement which comprises a network for deriving from the carrier voltage prior todemodulation voltage of side band component frequencies corresponding to higher modulation frequencies, means for rectifying the derived voltage, means responsive to said derived voltage for determining the amplitude level at which said rectifying means is operative, and means responsive to the rectified voltage for controlling the said utilization network.
  • a radio receiving system having a rncdulated carrier amplifier, a detector and. audio amplifier, means for suppressing the reproduction of disturbances without substantially interfering with reproduction of modulation frequencies, said means comprising a'rnodulated carrier voltage path, said path including a filter network for passing voltages solely of side band frequencies, corresponding to the high modulation frequencies, a rectifier coupled to said filter network for deriving a control voltage from said passed voltages,
  • a method of receiving side band modulated carrier waves Without interference from disturbing electrical impulses which includes collecting modulated carrier waves and disturbance impulses, demodulating the collected waves and impulses, amplifying and reproducing the demodulated waves and impulses, deriving from the collected waves prior to demodulation thereof voltages of side band frequency components corresponding to the high modulation frequencies, deriving a uni-directional control voltage from the derived voltages, controlling the amplification of said demodulated Waves in response to said control voltage, and simultaneously regulating the derivation of said control voltage in response to collected waves.
  • a method of receiving side band modulated carrier waves without interference from disturb ing electrical impulses which includes collecting modulated carrier waves and disturbance impulses, demodulating the collected waves and impulses, amplifying and reproducing the demodulated waves and impulses, deriving from the collccted waves prior to demodulation thereof voltages of side band frequency components corresponding to the high modulation frequencies, deriving a uni-directional control voltage from the derived voltages, controlling the amplification of said demodulated waves in response to said control voltage, and simultaneously controlling the derivation of said control voltage in response to the amplitude of said first named derived voltages.

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  • Amplifiers (AREA)
  • Noise Elimination (AREA)
US261257A 1938-06-24 1939-03-11 Aperiodic disturbance suppression circuits Expired - Lifetime US2237457A (en)

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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2438501A (en) * 1942-08-20 1948-03-30 Electronic Lab Inc Radio noise rejector circuit
US2459675A (en) * 1941-04-05 1949-01-18 Motorola Inc Interference reducing radio receiver
US2488153A (en) * 1947-03-04 1949-11-15 Jay D Wiener Portable telephone extension
US2489254A (en) * 1944-01-04 1949-11-29 Otto F A Arnold Radio system
US2527561A (en) * 1947-04-30 1950-10-31 Farnsworth Res Corp Selective calling system
US2538040A (en) * 1943-05-01 1951-01-16 Arthur C Prichard Interference reduction circuit for radio pulse receivers
US2546987A (en) * 1946-12-06 1951-04-03 Standard Telephones Cables Ltd Noise suppression circuit
US2604587A (en) * 1947-11-12 1952-07-22 Rca Corp Signal selecting means
US2644082A (en) * 1949-02-23 1953-06-30 Rca Corp Automatic gain control system
US2761060A (en) * 1952-08-01 1956-08-28 Rca Corp Auto alarm systems
US2761897A (en) * 1951-11-07 1956-09-04 Jones Robert Clark Electronic device for automatically discriminating between speech and music forms
US2852622A (en) * 1955-01-13 1958-09-16 Collins Radio Co Signal-to-noise squelch control circuit
US2966657A (en) * 1949-03-31 1960-12-27 James F Price Acoustic direction finder
US3569840A (en) * 1968-10-04 1971-03-09 Collins Radio Co Of Canada Ltd Carrier squelch scheme
US3701025A (en) * 1954-11-02 1972-10-24 Us Navy Selective signal tuning device

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2459675A (en) * 1941-04-05 1949-01-18 Motorola Inc Interference reducing radio receiver
US2438501A (en) * 1942-08-20 1948-03-30 Electronic Lab Inc Radio noise rejector circuit
US2538040A (en) * 1943-05-01 1951-01-16 Arthur C Prichard Interference reduction circuit for radio pulse receivers
US2489254A (en) * 1944-01-04 1949-11-29 Otto F A Arnold Radio system
US2546987A (en) * 1946-12-06 1951-04-03 Standard Telephones Cables Ltd Noise suppression circuit
US2488153A (en) * 1947-03-04 1949-11-15 Jay D Wiener Portable telephone extension
US2527561A (en) * 1947-04-30 1950-10-31 Farnsworth Res Corp Selective calling system
US2604587A (en) * 1947-11-12 1952-07-22 Rca Corp Signal selecting means
US2644082A (en) * 1949-02-23 1953-06-30 Rca Corp Automatic gain control system
US2966657A (en) * 1949-03-31 1960-12-27 James F Price Acoustic direction finder
US2761897A (en) * 1951-11-07 1956-09-04 Jones Robert Clark Electronic device for automatically discriminating between speech and music forms
US2761060A (en) * 1952-08-01 1956-08-28 Rca Corp Auto alarm systems
US3701025A (en) * 1954-11-02 1972-10-24 Us Navy Selective signal tuning device
US2852622A (en) * 1955-01-13 1958-09-16 Collins Radio Co Signal-to-noise squelch control circuit
US3569840A (en) * 1968-10-04 1971-03-09 Collins Radio Co Of Canada Ltd Carrier squelch scheme

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