US2266496A - Carrier frequency system - Google Patents

Carrier frequency system Download PDF

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Publication number
US2266496A
US2266496A US280715A US28071539A US2266496A US 2266496 A US2266496 A US 2266496A US 280715 A US280715 A US 280715A US 28071539 A US28071539 A US 28071539A US 2266496 A US2266496 A US 2266496A
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US
United States
Prior art keywords
channels
filters
attenuation
channel
impedance
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
US280715A
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English (en)
Inventor
Hagen Wolfgang
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.)
Alcatel Lucent Deutschland AG
C Lorenz AG
Original Assignee
Standard Elektrik Lorenz AG
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Publication date
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Publication of US2266496A publication Critical patent/US2266496A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J1/00—Frequency-division multiplex systems
    • H04J1/02—Details
    • H04J1/04—Frequency-transposition arrangements
    • H04J1/045—Filters applied to frequency transposition

Definitions

  • Figs. 1, 2, 3 are graphic representationsthat serve to explain the theory underlying prior arrangements While Fig. 4 is a diagram which serves to describe one embodiment of the invention by way of example. 7
  • the filters of such arrangements have to meet the following requirements: In the transmission range they must have the least possible attenuation whereas in the ranges of the neighbouring channels the impedance of the filters as viewed in backward direction must have either high ohmic impedance or very low ohmic impedance according to whether the filters are connected in parallel or in series.
  • a twofold modulation is employed in order to reduce the demand on the filters, as will be'understood from Figs. 1 and 2.
  • the suppressing attenuation intended to afiect the neighbouring channel is produced with the aid of means located in the output filter A of the premodulating stage A while the output filter B of the second modulating stage B has to suppress by attenuation the second sideband only.
  • the output filters A are then assembled in a manner so that all the chaner many July 1, 1938 (o nap-44) nels are amplified by an amplifier V common to them.
  • the fact that less attenuation is here demanded of the output filters B is inconsistent with the strict requirements regarding the impedance of the neighbouring channels.
  • the filters here employed have the property that the impedance, before assuming high values in the suppression range, passes through a resonance point of the impedance zero, as will ap pear from Fig. 3. With filters of such type this point would be contained in the neighbouring channel.
  • the attenuation characteristic in this channel will therefore be irregular to such extent that it will be diflicult to correct or equalize it.
  • Th invention aims to overcome all these disadvantages.
  • the even numbered ones on the other hand are assembled to form frequency mixtures and these are conveyed to a fourwire connection where they join each other.
  • the channels numbered I, 3, 5, 1, etc. and those numbered 2, 4, 6, etc. are assembled to join each other in a four-wire connection, as shown in Fig. 4 by way of example.
  • the characteristic of channel K3 may be of so fiat a course as not to present the requisite high ohmic impedance characteristic until the commencement of channel K5 or KI, as the case may be.
  • the characteristic of the filter impedance is of no effect upon the operation of the system. It therefore entails no risk to have the impedance pass here through the zero value. Similar conditions apply for the filters of the even numbered channels. The demands on the filters are considerably reduced in this way. By use of the proposed arrangement the requirements with respect to the impedance characteristic need not be more severe than with respect to the attenuation characteristic.
  • the filter output circuits of the channels are joined in parallel connection to the transformers, that is to say, the impedances of the filters must be of high ohmic impedance in the suppression range.
  • the aforesaid particulars also apply for series connection of the channel filters, provided that these are so calculated that within the range of attenuation their impedances approach the zero value.
  • the described arrangement entails an additional attenuation of about 3 decibels. This, however, does not represent a loss greater than if the channels are comprised without making use ofthe novel arrangement, because as stated channels on the one hand and the odd numbered 55 the filters in consequence of their simple construction do not attain either a high impedance or a low one, in the suppression range for the neighbouring channels, causing the neighbouring channels to undergo losses due to attenuation.
  • Such attenuation losses also have the disadvantage of depending on frequency, whereby the channels require special correcting or equalizing measures to be provided. In the novel arrangement, however, such correction may in general be dispensed with.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Filters And Equalizers (AREA)
US280715A 1938-07-01 1939-06-23 Carrier frequency system Expired - Lifetime US2266496A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE210931X 1938-07-01

Publications (1)

Publication Number Publication Date
US2266496A true US2266496A (en) 1941-12-16

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ID=5799978

Family Applications (1)

Application Number Title Priority Date Filing Date
US280715A Expired - Lifetime US2266496A (en) 1938-07-01 1939-06-23 Carrier frequency system

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US (1) US2266496A (en(2012))
BE (1) BE435104A (en(2012))
CH (1) CH210931A (en(2012))
FR (1) FR856911A (en(2012))

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2700753A (en) * 1948-06-28 1955-01-25 Phillips Petroleum Co Method of and apparatus for seismic prospecting
US2874356A (en) * 1948-06-28 1959-02-17 Phillips Petroleum Co Method of and apparatus for seismic prospecting

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2700753A (en) * 1948-06-28 1955-01-25 Phillips Petroleum Co Method of and apparatus for seismic prospecting
US2874356A (en) * 1948-06-28 1959-02-17 Phillips Petroleum Co Method of and apparatus for seismic prospecting

Also Published As

Publication number Publication date
BE435104A (en(2012))
CH210931A (de) 1940-08-15
FR856911A (fr) 1940-08-16

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