US2189308A - Constant selectivity receiver - Google Patents

Constant selectivity receiver Download PDF

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Publication number
US2189308A
US2189308A US506877A US50687731A US2189308A US 2189308 A US2189308 A US 2189308A US 506877 A US506877 A US 506877A US 50687731 A US50687731 A US 50687731A US 2189308 A US2189308 A US 2189308A
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United States
Prior art keywords
audio
frequency
radio
frequencies
circuit
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Expired - Lifetime
Application number
US506877A
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English (en)
Inventor
Rene A Braden
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RCA Corp
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RCA Corp
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Filing date
Publication date
Priority to BE385446D priority Critical patent/BE385446A/xx
Application filed by RCA Corp filed Critical RCA Corp
Priority to US506877A priority patent/US2189308A/en
Priority to DER83724D priority patent/DE614585C/de
Application granted granted Critical
Publication of US2189308A publication Critical patent/US2189308A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J3/00—Continuous tuning
    • H03J3/02—Details
    • H03J3/06—Arrangements for obtaining constant bandwidth or gain throughout tuning range or ranges

Definitions

  • a frequency amplier which includes at leastfonetuned circuit in each pair of ⁇ coupled input and ⁇ output circuits, the tuned circuit possessing a 'constant resistance over apredeterrnined range of frequencies whereby the sharpness of tuning is Vsubstantially the same at all frequencies Within a predetermined range, such as the broadcast range.,.
  • aA tuned radio ⁇ frequency j amplifier is provided which does not tune too sharply at low carrier frequencies, and too-broadly at high carrier frequencies, but rather has a constant selectivity characteristic throughout the desired radio ireque'rrcy range.
  • ⁇ a radioreceiver comprising a constantlselectivity "tuned radio frequency amplifier combined with an audio frequency amplifiedwhose fidelity curve is modified so that the overall curve of the receiver is practically flat up tol 5,000 cycles whereby a receiver of good fidelity is obtained.
  • Another4 importantfobject of the present in vention is to provide a method off, andmeans for,
  • ⁇ Anotlierobjec'zt of the invention is to provide a radio broadcast receiver arrangement utilizing a compensating audio frequency amplierwith a constant selectivity radio 'frequencyamplifier for bringing up thehi'gh notes tothejsame amplitude as the low notes whereby improved quality of re ⁇ - ception is secured throughout the broadcast range without impairng the ⁇ selectivity'of reception, in
  • Fig. 1 diagrammatically shows a receiver embodying the invention
  • Fig. 2 is a graphic representation of the operation of the compensating audio frequency amplifier.
  • a radio receiver comprising the usual signal energyy collecting means consisting of an antenna A,
  • the grounded antenna circuit is coupled, as at M, to the input electrodes of the screen grid tube I in the first stage 'of radio frequency amplification.
  • the coupling .means M ⁇ the cathode in the well known manner.
  • the anode of the tube I is ⁇ connected to the positive terminal of a source of uni-directional current B through the primary coil 2', the negative'terminal Aof the source B being connected to
  • the inputcircuit ofthe tube I is tuned by a Variable condenser 4, the latter being connected in series with a circuit generally denoted by the reference numeral 5.
  • the circuit 5 comprises an inductance Lo in serieswith a resistance RL, the latter two elements being in shunt with the series connection between the capacity Co and resistance
  • the primary coil 2' is coupled t0 the secondary coil 3', both coils constituting the coupling means 40 between the output circuit of tube I and the input circuit of screen grid tube vI5.
  • the input circuit of tube 6 is tuned by a variable condenser 4 connected in series with an impedance circuit 5, the
  • the anode of tube 6 is energized from a source B, the latter, if desired, being a source common with the source B connectedwith the anode of tube I.
  • the output circuit of the tube I5 is coupled, by the same type of coupling used in connection with the rst two tubes, to the input circuit of the screen grid tube 1, the control electrode circuit of this tube being arranged for detection.
  • This is accomplished by the well known series capacity and shunt grid leak connection, generally denoted by the reference numeral 8, in the control electrode circuit,
  • a variable condenser pending application Serial No. 396,956 already referred to, the utilization of the impedance circuit 5 in series with the tuning condenser 4 in 'each tuned radio frequency stage results in a substantially vconstant degree of sharpness of tuning throughout a predetermined range of i'requencies, such as the broadcast range.
  • the tuned radio frequencyamplifler is rendered constantly selective by suitable selection of the values of the constants of the elements Lo, RL, Co and Rait being clearly understoodthat the present disclosure of the means for imparting a constant resistance characteristic to the tuned radio frequency circuits is not to be interpreted as limiting in any manner the mode of securing a constant selectivity characteristic.
  • my aforementioned copending application discloses other modes and principles of securing the same result, the essential feature for the design of the tuned radio frequency stages being the production of amplifying tuned circuits possessing a constant effective resistance throughout a given frequency range.
  • the detector stage impresses across the primary coil I of the first audio'. transformer coupling Il, a band of audio frequencies having a width of substantially 10 kilocyclesthat is to say each side band is ,5,000 cycles wide
  • the remaining problem, solved by me in the present application is to transmit this selected band of audio frequencies through the subsequent audio frequency amplifier in such a manner that the audio frequency output will be apparently the same at all audio frequencies within selected 10 kilocycle bands.
  • the solution of this phase of the problem is now to be described in detail.v Across the primary coil IIJ is connected a series'connection of a resistor I2 and an inductance I3, it being understood that the anode of the detector tube I is maintained at the proper triode type being adapted to be substituted forv by any other desired type of space discharge device.
  • the control electrode is preferably maintained at a proper negative biasing potential by connecting the low potential terminal of coil I4 to the negative terminal of a biasing source C, the positive terminal of the source C being connected to the cathode, in a manner well known to those skilled in the art, but not shown herein in order to preserve simplicity of description.
  • the tube l has its anode positively biased from a source-B2, it being obvious that this source mayT be the same source as the source B1, the anode being connected to the positive terminal of source B2 through the primary coil ID of the second audio transformer I l'.
  • a series impedance path composed of a capacity I6, a resistance I1, and an inductance I8, all in series, is connected across the primary coil I0'.
  • the secondaryv coil I4 of transformer II is connected between the input electrodes of tube I9, the latter preferably being an audio power tube of any desired type.
  • the control electrode of tube I9 is negatively biased from a source C1, ⁇ in ⁇ a manner similar to the control electrode of tube I5, while the anode of tube I9 ispositively biased from a source B3 through the primary coil 20 of the output audio transformer 2
  • the secondary coil 22 of output transformer ZI maybe connected to any well known type of utilization means, such as head phones, a loud speaker and the like.
  • Fig. 2 there is shown, in a graphical manner, a curve which demonstrates the operation of the compensating audio frequency amplifier. It will be noted from the curve that the amplincation increases with frequency up to about 5,000 cycles in substantially direct proportion to increase in frequency from a point approximately at '700 cycles.
  • an audio frequency amplifier is employed in the receiver circuit shown in Fig. l, whose frequency characteristic is the U quency amplifier.
  • Fig. 2 graphically shows the combined effect of both shunting circuits in the audiofre
  • said tuned circuit including an imi pedance element having resistance therein arranged in such a manner that the resonance curve ofthe coupledresonant circuits is substantially the same at whatever carrier frequencies in a desired carrier frequency range the said one circuit is tuned to, and a compensating audio frequency amplifier comprising at least two coupled stages, the coupling between ⁇ said stages being designed in such a manner that the ampliication of the audio frequency amplifier increases with audio frequency whereby the apparent audio frequency amplification of the side bands of selected carrier frequencies throughout said range is substantially uniform.
  • a radicfrequency amplifier in a radio receiver, a radicfrequency amplifier, means for tuning said amplifier over adesired range of modulated carrier frequencies, yadditional means electrically associated with said tuning means and amplifier for producing a uniform selectivity characteristic for said amplifier, means for detecting selected modulated carrier energy, and an audio frequency ampliiier having an amplification characteristic which is directly proportional to audio frequencies to be amplified.
  • a selec- ⁇ detector in combination, in a radio receiver, a selec- ⁇ detector, and an audio frequency amplifier including means to preserve an audio frequency amplification ratio between the detected selected carrier and side bands which is the inverse of said ⁇ radio frequency amplification ratio.
  • the method of receiving bands of radio fre- ⁇ quencies, corresponding to modulated carrier energy at different carrier frequencies, throughout a desired frequency range which consists in selecting .a desiredband of radio frequencies comprising a carrier and its side bands due to modulation, subjecting the selected band to radio frequency amplification, selectively amplifying the amplified band at least another time whereby band varies inversely according to a predetermined ⁇ relation with the spacing between the said given frequency and the carrier, detecting the selectively amplified band of frequencies to produce a bandof audio frequencies corresponding to the selected bandof radio frequencies, amplifying the band of audio frequencies in a manner inverse to that ⁇ at radio frequency amplication, and maintaining said predetermined radio frequency amplification relation substantially constant for all selected bands of radio frequencies throughout said desired frequency range.
  • An apparatus for receiving a carrier wave modulated by a desired signal including, in combination, selective receiving means, the selectivity of said means being such that the amplitude of the modulation frequencies over a substantial portion of the modulation frequency range will be relatively altered, means for relatively altering the amplitude of the said modulation frequencies inthe opposite sense, and additional means, electrically' associated with said selective receiving means, for maintaining the said first alteration substantially constant over the tuning range of said receiving means.

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  • Amplifiers (AREA)
US506877A 1931-01-06 1931-01-06 Constant selectivity receiver Expired - Lifetime US2189308A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE385446D BE385446A (enrdf_load_stackoverflow) 1931-01-06
US506877A US2189308A (en) 1931-01-06 1931-01-06 Constant selectivity receiver
DER83724D DE614585C (de) 1931-01-06 1932-01-06 Empfangseinrichtung

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US506877A US2189308A (en) 1931-01-06 1931-01-06 Constant selectivity receiver

Publications (1)

Publication Number Publication Date
US2189308A true US2189308A (en) 1940-02-06

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Family Applications (1)

Application Number Title Priority Date Filing Date
US506877A Expired - Lifetime US2189308A (en) 1931-01-06 1931-01-06 Constant selectivity receiver

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US (1) US2189308A (enrdf_load_stackoverflow)
BE (1) BE385446A (enrdf_load_stackoverflow)
DE (1) DE614585C (enrdf_load_stackoverflow)

Also Published As

Publication number Publication date
DE614585C (de) 1935-06-13
BE385446A (enrdf_load_stackoverflow)

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