US2422976A - Noise reducer for amplitude modulation reception - Google Patents

Noise reducer for amplitude modulation reception Download PDF

Info

Publication number
US2422976A
US2422976A US542739A US54273944A US2422976A US 2422976 A US2422976 A US 2422976A US 542739 A US542739 A US 542739A US 54273944 A US54273944 A US 54273944A US 2422976 A US2422976 A US 2422976A
Authority
US
United States
Prior art keywords
noise
point
diode
modulation
output circuit
Prior art date
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
Application number
US542739A
Other languages
English (en)
Inventor
Jr Madison G Nicholson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
COLONIAL RADIO Corp
Original Assignee
COLONIAL RADIO CORP
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority to NL75416D priority Critical patent/NL75416C/xx
Application filed by COLONIAL RADIO CORP filed Critical COLONIAL RADIO CORP
Priority to US542739A priority patent/US2422976A/en
Priority to GB10963/47A priority patent/GB646920A/en
Application granted granted Critical
Publication of US2422976A publication Critical patent/US2422976A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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

Definitions

  • This invention relates to noise limiting circuits, and more particularly to noise limiting circuits adapted and arranged for use in the reception of amplitude modulated signals.
  • radio receiver which is relatively immune to noise of the electrical impulse type and which will operate with relative freedom from noise in the immediate neighborhood of other electrical apparatus, such as automobile ignition systems, electric Shavers, vacuum cleaners, and the like.
  • FIG. 1 is a circuit diagram of apparatus in accordance with my invention.
  • Fig. 2 is a series of curves illustrating the operation of the circuit in accordance with my invention.
  • I0 may represent the final coupling transformer from the last intermediate stage of a superheterodyne receiver or the last T. R. F. stage of a T. R, F. receiver.
  • the transformer I may comprise primary coil I Ila shunted by tuning condenser III'c and secondary coil Ib shunted by condenser Illd. Since the parts ofV the receiverprior to this point are well understood in the art and per' se are not part of this invention, they are not shown or described.
  • 'I'he signal supplied to the coil Ilb may be passed through condenser I I and impressed upon the rectifier diode I2, which may comprise cathode I2c and anode I ⁇ 2 ⁇ a.
  • the currents rectified by the diode I2 pass through resistances- I3 and I4 connected in series and having their upper end connected to the diode anode Ia and their lower end to ground, as indicated.
  • Resistance III maybe shunted by by-pass condenser I5, which eliminates from resistor I4 any radio frequency currents.
  • a connection may be made to anode 26a of rectier diode 2li, having also cathode Zfc.
  • the latter may be connected to ground throughcondenser 2,4, and may supply audio signals to the audio frequency amplifier through condenser ZI, resistance 22, and volume control resistance 23, all being connected in series n between cathode 20c and ground.
  • From the anode 12a of diode I2 ⁇ a connection may be made through resistance I8 to anode 26a of diode 2li, which anode may be connected' to ground through condenser 2l.
  • An additional diode Zlimay be provided having its anode 29d connected to the cathode Zlio and its cathode 29o connected through resistance 30 and condenser 28 to the common point of condensers I6 and I1, and the end of resistance I8, which is connected to anode 26a, may be connected through resistance I9 to the common point of condenser 28 and resistance 30.
  • the average value of EB . is negative and represents the axis of the modulation curve EB, which can nevel ⁇ go above the zero line.
  • a reduced signal voltage is applied to the anode 20a of diode 20 through the voltage divider formed by resistances I3 and I4, which are preferably chosen so that the voltage from point A to ground is about one-third that from point B to ground. So long as the anode 20a is positive with respect to cathode 20cy diode 20 will act like a wire connection and will pass the audio frequency signal through condenser 2I and resistances 22 and 23.
  • the potential of point A with respect to ground is shown in curve EA.
  • diode 20 acts as an open circuit and the voltage at point D will begin to approach the voltage at point C, the rate of approach being determined primarily by the time constant of resistance 30 and condenser 24. Should this process complete itself, the resulting noise pulse in the output would have an amplitude equal to one hundred per cent modulation, as shown in curve EL. However, this process is not allowed to complete itself because the noise pulse is rectied in the diode 26, producing a voltage which makes point E more positive than point D, thus opening the circuit through diode 29.
  • point D is isolated from all input sources because both diodes 20 and 29 no longer pass current, and point D simply floats during the small time interval of the noise pulse.
  • Diode 26 is biased to cut-off for all signals equal or less than normal modulation peaks, this being determined by the ratio of condensers I6 and I'I.
  • the final or output wave then has the form shown in curve Eo, from which it will be seen that the only eiect of the noise impulse is to produce a small irregularity or dimple in the iinal audio wave form.
  • a radio receiver of the amplitude modulation type in combination, a signal demoduu lator, a capacity charged thereby, an audio output circuit containing capacity, a, connection between said output circuit and said demodulator and a second connection between said output circuit and the first capacity, and means for interrupting both of said connections during the occurrence of noise pulses substantially exceeding the level ci" one hundred per cent positive modulation peaks.
  • a radio receiver of the amplitude modulation type in combination, a signal demodulator, a capacity charged thereby, an audio output circuit containing capacity, a connection between said output circuit and said demodulator and a second connection between said output circuit and the first capacity, and means comprising a pair of diodes for interrupting both of said connections during the occurrence of noise pulses substantially exceeding the level of one hundred per cent positive modulation peaks.
  • a radio receiver of the amplitude modulation type in combination, a signal demodulator, a capacity charged thereby, an audio output circuit containing capacity, a connection between said output circuit and said demodulator and between said output circuit and the first capacity, and means comprising a pair of diodes and means for maintaining the anodes thereof negative with respect to their cathodes for interrupting both of said connections during the occurrence of noise pulses substantially exceeding the level of one hundred per cent positive modulation peaks.
  • a radio receiver of the amplitude modulation type in combination, a signal demodulator, a capacity charged thereby, an audio output circuit containing capacity, a connection between said output circuit and said demodulator and between said output circuit and the rst capacity, and means comprising a. pair of diodes and means for maintaining the anodes thereof negative with respect to their cathodes for interrupting both of said connections during the occurrence of noise pulses substantially exceeding the level of one hundred per cent positive modulation peaks, having the anode of one and the cathode of the other connected together.
  • a radio receiver of the amplitude modulation type in combination, a signal demodulator, a capacity charged thereby, an audio output circuit containing capacity, a connection between said output circuit and said demodulator and between said output circuit and the first capacity, and means comprising a pair of diodes and means for maintaining the anodes thereof negative with respect to their cathodes for interrupting both of said connections during the occurrence of noise pulses substantially exceeding the level of one hundred per cent positive modulation peaks, said last mentioned means comprising a third diode arranged to rectify noise pulses having an amplitude substantially exceeding the level of one hundred per cent positive modulation peaks.
  • a radio receiver of the amplitude modulation type in combination, a signal demodulator, a capacity charged thereby, an audio output 'circuit containing capacity, a connection between said output circuit and said demodulator and between said output circuit and the first capacity, and means comprising a pair of diodes and means for maintaining the anodes thereof negative with respect to their cathodes for interrupting both of said connections during the occurrence of noise pulses substantially exceeding the level of one hundred per cent positive modulation peaks, said last mentioned means comprising a third diode arranged to rectify noise pulses having an amplitude substantially exceeding the level of one hundred per cent positive modulation peaks, said last diode being biased to prevent operation in response to voltages less than the level of one hundred per cent positive REFERENCES CITED
  • the following references are of record in the le of this patent:

Landscapes

  • Noise Elimination (AREA)
US542739A 1944-06-29 1944-06-29 Noise reducer for amplitude modulation reception Expired - Lifetime US2422976A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
NL75416D NL75416C (enrdf_load_stackoverflow) 1944-06-29
US542739A US2422976A (en) 1944-06-29 1944-06-29 Noise reducer for amplitude modulation reception
GB10963/47A GB646920A (en) 1944-06-29 1947-04-24 Improvements in or relating to a noise reduction system for radio receivers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US542739A US2422976A (en) 1944-06-29 1944-06-29 Noise reducer for amplitude modulation reception

Publications (1)

Publication Number Publication Date
US2422976A true US2422976A (en) 1947-06-24

Family

ID=24165090

Family Applications (1)

Application Number Title Priority Date Filing Date
US542739A Expired - Lifetime US2422976A (en) 1944-06-29 1944-06-29 Noise reducer for amplitude modulation reception

Country Status (3)

Country Link
US (1) US2422976A (enrdf_load_stackoverflow)
GB (1) GB646920A (enrdf_load_stackoverflow)
NL (1) NL75416C (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2586190A (en) * 1947-07-23 1952-02-19 Wasmansdorff Carlton Radio receiver noise reducing circuit
US2621290A (en) * 1947-03-29 1952-12-09 Gilbert J C Andresen Limiter system
US2668233A (en) * 1948-07-19 1954-02-02 Sylvania Electric Prod Automatic noise limiter
US2673294A (en) * 1951-08-10 1954-03-23 Ca Nat Research Council Discriminator circuit
US2710310A (en) * 1948-11-20 1955-06-07 Sylvania Electric Prod Variable level synchronizing signal clipper
US2771549A (en) * 1955-02-10 1956-11-20 Collins Radio Co Signal receiving circuit
US3064197A (en) * 1960-09-20 1962-11-13 Collins Radio Co Automatic noise limiter circuit
US3234334A (en) * 1962-12-14 1966-02-08 Sherwood Electronic Lab Inc Fm stereo-multiplex receiving system
US4042883A (en) * 1976-03-25 1977-08-16 Motorola, Inc. Automatic noise limiter

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2129027A (en) * 1936-05-19 1938-09-06 Rca Corp Receiver noise limiting circuit
US2135949A (en) * 1937-06-17 1938-11-08 Rca Corp Noise suppressor circuit
US2172922A (en) * 1936-04-04 1939-09-12 E H Scott Automatic noise suppressor
US2192189A (en) * 1938-03-12 1940-03-05 Philip M Haffcke Static limitation in radio receivers
US2208398A (en) * 1939-02-23 1940-07-16 Bell Telephone Labor Inc Radio receiver
US2208953A (en) * 1939-07-12 1940-07-23 American Telephone & Telegraph Noise reducing receiving system
US2216517A (en) * 1937-09-21 1940-10-01 Rca Corp Noise suppression circuits
US2231371A (en) * 1939-01-04 1941-02-11 Rca Corp Noise suppression circuit
US2344697A (en) * 1942-04-17 1944-03-21 Rca Corp Noise reduction system

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2172922A (en) * 1936-04-04 1939-09-12 E H Scott Automatic noise suppressor
US2129027A (en) * 1936-05-19 1938-09-06 Rca Corp Receiver noise limiting circuit
US2135949A (en) * 1937-06-17 1938-11-08 Rca Corp Noise suppressor circuit
US2216517A (en) * 1937-09-21 1940-10-01 Rca Corp Noise suppression circuits
US2192189A (en) * 1938-03-12 1940-03-05 Philip M Haffcke Static limitation in radio receivers
US2231371A (en) * 1939-01-04 1941-02-11 Rca Corp Noise suppression circuit
US2208398A (en) * 1939-02-23 1940-07-16 Bell Telephone Labor Inc Radio receiver
US2208953A (en) * 1939-07-12 1940-07-23 American Telephone & Telegraph Noise reducing receiving system
US2344697A (en) * 1942-04-17 1944-03-21 Rca Corp Noise reduction system

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2621290A (en) * 1947-03-29 1952-12-09 Gilbert J C Andresen Limiter system
US2586190A (en) * 1947-07-23 1952-02-19 Wasmansdorff Carlton Radio receiver noise reducing circuit
US2668233A (en) * 1948-07-19 1954-02-02 Sylvania Electric Prod Automatic noise limiter
US2710310A (en) * 1948-11-20 1955-06-07 Sylvania Electric Prod Variable level synchronizing signal clipper
US2673294A (en) * 1951-08-10 1954-03-23 Ca Nat Research Council Discriminator circuit
US2771549A (en) * 1955-02-10 1956-11-20 Collins Radio Co Signal receiving circuit
US3064197A (en) * 1960-09-20 1962-11-13 Collins Radio Co Automatic noise limiter circuit
US3234334A (en) * 1962-12-14 1966-02-08 Sherwood Electronic Lab Inc Fm stereo-multiplex receiving system
US4042883A (en) * 1976-03-25 1977-08-16 Motorola, Inc. Automatic noise limiter

Also Published As

Publication number Publication date
NL75416C (enrdf_load_stackoverflow)
GB646920A (en) 1950-11-29

Similar Documents

Publication Publication Date Title
US2422976A (en) Noise reducer for amplitude modulation reception
US2410983A (en) Discriminator-rectifier circuit
US2200049A (en) Delayed automatic volume control circuits
US2247324A (en) Noise-limiting circuits for carrier wave communication systems
US2773181A (en) Frequency discriminator system
US2286442A (en) Amplitude limiter circuit
US2515196A (en) Automatic gain control
US2420248A (en) Amplitude limiter circuit
US2429762A (en) Combined frequency modulation and amplitude modulation detector circuits
US2675473A (en) Limiting circuit
US2318075A (en) Automatic gain control system
US2279819A (en) Signal receiving system
US2197516A (en) Silencing network
US2337196A (en) Signal and noise control system
US2142038A (en) Band pass filter
US2385211A (en) Apparatus for communication systems
US2221728A (en) Noise-limiting circuit for carrier wave communication systems
US2128996A (en) Automatic volume control circuits
US2271203A (en) Amplitude-limiting signal-translating channel
US2421136A (en) Gain control system for pulse modulation receivers
US2144935A (en) Automatic volume control circuits
US2507211A (en) Pulse receiver circuit
US2293835A (en) Noise limiter
US2207587A (en) Signal receiving system
US2105538A (en) Reduction of noise