US1907109A - Radio signaling system - Google Patents

Radio signaling system Download PDF

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Publication number
US1907109A
US1907109A US501825A US50182530A US1907109A US 1907109 A US1907109 A US 1907109A US 501825 A US501825 A US 501825A US 50182530 A US50182530 A US 50182530A US 1907109 A US1907109 A US 1907109A
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US
United States
Prior art keywords
frequency
frequencies
band
carrier
signal
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
US501825A
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English (en)
Inventor
Hinton Leslie Turner
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.)
AT&T Corp
Original Assignee
Western Electric Co Inc
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Filing date
Publication date
Application filed by Western Electric Co Inc filed Critical Western Electric Co Inc
Application granted granted Critical
Publication of US1907109A publication Critical patent/US1907109A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/08—Transmission systems not characterised by the medium used for transmission characterised by the use of a sub-carrier
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03C—MODULATION
    • H03C1/00—Amplitude modulation
    • H03C1/52—Modulators in which carrier or one sideband is wholly or partially suppressed
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/002—Transmission systems not characterised by the medium used for transmission characterised by the use of a carrier modulation
    • H04B14/004—Amplitude modulation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/005—Control of transmission; Equalising

Definitions

  • one of the objects of the present invention is to reduce this quality degradation and to improve the standard of quality of the transmitted signals.
  • the received signal usually consists of a carrier wave and of two side bands. It is a known fact that particularly in short wave operation a selective fading effect develops. This effect is usually explained by the phase dif ferences in the received signals when they are received over different space channels. The phase differences vary with the weather, the
  • the receiver picks up three frequencies, viZ., 0+ 1100, C and C 1100, where C is the carrier frequency.
  • C is the carrier frequency.
  • the amplitude of the 1100 cycles received is afunction of the amplitude of the carrier wave and of the side bands whereas that of the unwanted modulation products of 2200 cycles is a function of the amplitude of the side band alone.
  • the amplitude of the carrier wave may decrease considerably while the amplitude of the side bands may remain unchanged. Then the ratio of the received signals of 1100 cycles to the one of 2200 cycles will be considerably changed, that of 2200 cycles appearing in such an amount that it harms the quality of the transmit-ted signals.
  • harmonics of the original frequencies are produced whenever a modulated wave is demodulated in a device operating by means of a nonlinear characteristic.
  • these harmonics are always produced in the usual types of receivers employing an ordinary detector.
  • the predominant harmonic is the second (i. e. 2f where f is the fundamental of the si al frequency) and the ratio of the ampiitn" e of the second hannonic to the amplitude of the fundamental is a function of the percentage modulation.
  • any signaling system utilizing a modulated carrier wave i. e. using inverted or non-inverted signal frequency bands
  • spurious frequencies which are not harmonics of the original frequencies are introduced. This occurs whenever, as in the case of music broadcasting, more than one frequency is transmitted at a time. In such case the various signal frequencies beat together, giving terms whose frequencies are equal to the sums and differences of all the original signal. frequencies taken together in pairs. This a degradation of quality which. is often noticeable in the reception of ordinary broadcasting.
  • means are provided for minimizing the influence of spurious harmonics in a high frequency signaling system.
  • the spurious harmonics are reduced by suitably choosing the relative positions in the frequency spectrum of the carrier frequency'and of the signal frequency hand.
  • the spacing frequency that is to say, the distance in the frequency spectrum between the carrier frequency and the lower frequency of the signal frequency band, is different from zero, some parasitic intermodulation products falling within the signal frequency band are cut out.
  • the spacing frequency is equal to the frequency band Width of the signal frequency cut-off frequencies, substantially all these spurious or parasitic inter-modulation prodnets are cut out.
  • One advantage of the present invention is that the present method for reducing the influence of spurious harmonies may be applied eitherto a secret signaling system wherein the whole frequency band is inverted, or to a system wherein only some sub-bands of the signal freqnency bands are inverted. In either of the cases an improvement in the quality of the transmitted signals is obtained.
  • a high frequency signaling system is provided with the side bands located at such distance from the carrier band that undesirable frequencies are substantially eliminated.
  • Figs. 1 and 2 il lustrate the position in the frequency spectrum of the side band and of the carrier frequency.
  • Fig. 3 illustrates the position of the side hands when they have been spaced from the carrier frequency.
  • Figs. 4c and 5 show improved high frequency signaling systems.
  • spurious frequencies are produced in the received signals occupying a hand of frequency of width 2a.
  • the original signal frequency band occupies the position 1 in the frequency spectrum whereas 2 represents the range covered by the spurious frequencies which are obtained during selective fading conditions.
  • the width of the useful baml 0 should not be greater than that of the band a.
  • Fig. 4 shows the system schrnnatical iy in the form applied to a simple tckqihouc systmn.
  • a band having a frequency range from 0 to 3 kilocycles is increased in frequency by known means such as by a modulator MOD and selection of a side band by means of the filter F, and demodulators if necessary and is fed to the transmitter T as a frequency band from 3 to (i hilocycles.
  • the useful received signal will be comprised between 3 to 0 kilocycles and the useless one between 6 to 12 lrilocycles.
  • the two bands are then separated by a filter F which allows the passage of the useful signal alone.
  • a frequency step-down device which may comprise a filter F and a frequency changing device FG (which may be similar to the stepup arrangement used at the transmitting end) the frequency band is brought to the position of 0 to 3 kilocycles, thus giving a frequency band at the receiving point having the same position in the frequency spectrum the ori inal frequency band at the sending point.
  • *ig. 5 shows an alternative way for modifying the position of a signal frequency band in the frequency spectrum so as to reduce spurious frequencies.
  • the speech signals are applied to an apparatus T for transforming sound vibrations into electrical vibrations.
  • the said electrical vibrations are applied to a low pass filter LP having a cut-off frequency of 3000 cycles per second.
  • the filtered signals thereafter are applied to a modulator MODl, supplied with a modulating frequency of say 20 kilocycles, and the upper side band thus produced is selected by means of a filter F having a suitable pass range, for instance a pass range between 20 and 23 kilocycles.
  • This side hand then enters a demodulator MOD2 supplied with a carrier frequency of say 26 kilocycles the lower side band being then selected by means of a low pass filter LP having a cut-off frequency of 6000 cycles.
  • an inverted speech band with a frequency range of 3000 to 6000 cycles This is applied to the transmitter T and sent to the receiving station R.
  • the inverted speech is applied to a high pass filter HP having a cut-ofi frequency of 3000 cycles and is thereafter applied to a modulator MOD.1 supplied with a carrier frequency of 20 kilocycles, the upper side band being selected by means of a band pass filter BF of suitable range, for example a. pass filter of 23 to 26 kilocycles.
  • the out At the receivin .ioint' put of filter BF is applied to a demodulator MOD2 which is supplied with a carrier frequency of 26 lrilocycles, the lower side band being selected by means of a low pass filter Ll" with a cut-oil frequency of 3000 cycles, normal speech being ()btt-tll'md after this operation.
  • the normal. speech vibrations are applied to a device T adapted to transform electrical vibrations into sound waves.
  • the present systems permit an increase in the degree of modulation at the transmitter since the spurious harmonic frequencies are no longer troublesome. In certain cases the present system. allows a reduction of the signal to noise ratio, that is to say a reduction of the ratio of the received field strength to the field strength due to static inasmuch as this reduction of signd strength is offset by the increased perccn modulation that may be used.
  • the method of signaling which comprises generating a pair of sidebands displaced by a frequency interval from the neighborhood of an associated carrier Wave, transmitting said carrier and displaced sidebands, detecting displaced signals therefrom with incidental production of combination frequencies due to inter-modulation between the two sidebands, said combination frequencies lying mainly outside the frequency range of said signals due to said displacement of the sidebands, selecting said signals and translating them to their original frequency range substantially free from said combinat'ion frequencies.
  • a high frequency signaling system using signal frequency inversion wherein the transmitting wave comprises a carrier Wave and side-hands, said side-bands inversely related in frequencies to the signal frequencies, and spaced from said carrier and each other in the frequency spectrum by at least twice the Width of one of said side-bands.
  • the method of substantially eliminating effects in the received and translated Waves of the quality degrading combination and intermodulation frequencies produced in transmission which comprises spacing the inverted signal frequency bands, in the transmitted Waves, at least twice the signal frequency range apart, and separating said quality degrading frequencies from the useful components of the received Waves by frequency e discriminating means.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Noise Elimination (AREA)
US501825A 1930-01-02 1930-12-12 Radio signaling system Expired - Lifetime US1907109A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB1907109X 1930-01-02
NL54620A NL34797C (enrdf_load_stackoverflow) 1930-01-02 1930-12-03
FR733626T 1931-06-15

Publications (1)

Publication Number Publication Date
US1907109A true US1907109A (en) 1933-05-02

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ID=10893335

Family Applications (1)

Application Number Title Priority Date Filing Date
US501825A Expired - Lifetime US1907109A (en) 1930-01-02 1930-12-12 Radio signaling system

Country Status (4)

Country Link
US (1) US1907109A (enrdf_load_stackoverflow)
DE (1) DE609540C (enrdf_load_stackoverflow)
FR (1) FR733626A (enrdf_load_stackoverflow)
NL (1) NL34797C (enrdf_load_stackoverflow)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2455959A (en) * 1941-04-03 1948-12-14 Hartford Nat Bank & Trust Co Device for the transmission of signals by means of frequency-modulated carrier waves
US2502955A (en) * 1947-03-25 1950-04-04 Hartford Nat Bank & Trust Co Apparatus for deriving from a recurrent wave, a voltage of relatively low fundamental frequency but of the same shape
US2509716A (en) * 1944-05-08 1950-05-30 Radio Electr Soc Fr Arrangement for secret radio telephony
US2522846A (en) * 1943-08-02 1950-09-19 Comm Engineering Pty Ltd Multichannel carrier telephone system providing for music transmission at carrier frequencies
US2662933A (en) * 1951-04-26 1953-12-15 Bell Telephone Labor Inc Multiplex carrier telegraph system
US2693577A (en) * 1947-09-03 1954-11-02 Hartford Nat Bank & Trust Co Radio transmission system having a high signal-to-noise ratio
US3040125A (en) * 1958-09-16 1962-06-19 Fernseh Gmbh Method and apparatus for recording and reproducing video signals
US3678390A (en) * 1968-10-11 1972-07-18 Tokyo Shibaura Electric Co Frequency modulation communication system

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE767200C (de) * 1932-12-23 1952-02-14 Siemens & Halske A G Mehrfachtraegerfrequenzuebertragungssystem fuer Sprache unter Anwendung einer zwei- oder mehrfachen Modulation, insbesondere ueber Kabelleitungen
DE763148C (de) * 1937-10-26 1954-08-02 Telefunken Gmbh Anordnung zur Traegerfrequenzuebertragung eines auch sehr niedrige Frequenzen enthaltenden Fernsehfrequenzbandes
DE889903C (de) * 1939-11-17 1953-09-14 Fernseh Gmbh Fernsehuebertragungsverfahren
GB556079A (en) * 1942-03-12 1943-09-20 Standard Telephones Cables Ltd Improvements relating to multi-channel electrical communication systems
US2621325A (en) * 1946-08-20 1952-12-09 Radio Electr Soc Fr Plural modulation multiplex system

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2455959A (en) * 1941-04-03 1948-12-14 Hartford Nat Bank & Trust Co Device for the transmission of signals by means of frequency-modulated carrier waves
US2522846A (en) * 1943-08-02 1950-09-19 Comm Engineering Pty Ltd Multichannel carrier telephone system providing for music transmission at carrier frequencies
US2509716A (en) * 1944-05-08 1950-05-30 Radio Electr Soc Fr Arrangement for secret radio telephony
US2502955A (en) * 1947-03-25 1950-04-04 Hartford Nat Bank & Trust Co Apparatus for deriving from a recurrent wave, a voltage of relatively low fundamental frequency but of the same shape
US2693577A (en) * 1947-09-03 1954-11-02 Hartford Nat Bank & Trust Co Radio transmission system having a high signal-to-noise ratio
US2662933A (en) * 1951-04-26 1953-12-15 Bell Telephone Labor Inc Multiplex carrier telegraph system
US3040125A (en) * 1958-09-16 1962-06-19 Fernseh Gmbh Method and apparatus for recording and reproducing video signals
US3678390A (en) * 1968-10-11 1972-07-18 Tokyo Shibaura Electric Co Frequency modulation communication system

Also Published As

Publication number Publication date
NL34797C (enrdf_load_stackoverflow) 1935-03-15
FR733626A (fr) 1932-10-08
DE609540C (de) 1935-02-20

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