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US2158978A - Electric signal transmission system - Google Patents

Electric signal transmission system Download PDF

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US2158978A
US2158978A US127924A US12792437A US2158978A US 2158978 A US2158978 A US 2158978A US 127924 A US127924 A US 127924A US 12792437 A US12792437 A US 12792437A US 2158978 A US2158978 A US 2158978A
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Prior art keywords
frequency
equaliser
sections
attenuation
cable
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US127924A
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Inventor
Bowman-Manifold Michael
Collard John
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EMI Ltd
Electrical and Musical Industries Ltd
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EMI Ltd
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Priority claimed from GB3186537A external-priority patent/GB495815A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/10—Adaptations for transmission by electrical cable
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/14—Control of transmission; Equalising characterised by the equalising network used
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/04—Control of transmission; Equalising
    • H04B3/14—Control of transmission; Equalising characterised by the equalising network used
    • H04B3/141—Control of transmission; Equalising characterised by the equalising network used using multiequalisers, e.g. bump, cosine, Bode

Definitions

  • This invention relates to electric signal transmission systems and more particularly to transmission systems which are required to handle signals covering a wide band of frequencies.
  • equaliser sections somewhat similar to the sections that are contemplated in the present invention have been used for equalising submarine cables over a very narrow frequency band. Howeventhe errors which arise insubmarine cables are totally different from the. errors which are encountered in cables which are required to handle frequencies extending over a wide band of frequency, such as a cable which is requiredto handle television signals.
  • pthephase constant R, L, G and C are, respec- 'tively, the resistance, inductance, leakance and capacitance. of the transmission line per unit length, and w represents the angular frequency of the signal being transmitted and is equal to 21rf where f is. the frequency in cycles per second.
  • the cable ortransmission line which is contemplated in the present specification, is one capable of transmitting a very wide frequency range extending at least up to a hundred kilocycles per second. More particularly, the present invention is concerned with a cable capable of transmitting frequencies from substantially zero frequency to about two or three megacycles per second, such frequencies being ordinarily encountered in the transmission of television signals.
  • wL is large compared with R
  • m is large compared with G, so that the characteristic impedance is approximately 6
  • the cable impedance assuming that the output end is terminated by an impedance approximates to the value where R! is the total series resistance of the cable. In practical cases this value is not ap breciablsl difierent from Y It can also be shown that if wL is fairly large compared with R and wC is fairly large compared with G, then,
  • an electric signal transmission system comprising a transmission line or cable for transmitting a wide frequency band extending at least up to a hundred kilocycles, and an artificial line in series therewith comprising a plurality of equaliser sections, some or all of which consist of, or are electrically equivalent to, series elements consisting of resistances shunted by condensers and shunt elements consisting of inductances in series with resistances, the time constants and the magnitude of the components of said sections being so chosen as substantially to equalise simultaneously the greater part of the variation of attenuation and phase delay due to variation with frequency of the effective resistance, inductance, capacity and leakance of said line or cable.
  • the sections of the artificial line or equaliser may be sufficiently divided that the resultant line approximates to one having uniformly or infinitely distributed constants.
  • the various sections of the equaliser need not be so finely divided so as to approximate toa line having infinitely distributed constants and, in this case, it is preferred that the various equaliser sections be spaced or centred at frequencies corresponding substantially to equal loss increments on the attenuation curve of the transmission line or cable to be equalised.
  • the characteristic impedance of such a form of equaliser is not constant over the frequency range, and in accordance with a further feature of the invention an improved form of termination impedance is provided for terminating the artificial line.
  • the sections of the equaliser are modified and the equaliser terminated as hereinafter more particularly referred It is also possible in accordance with another feature of the invention, to reduce the number of sections employed by an improved form of section which replaces the sections operative at the highest frequencies of the band.
  • Another feature of the invention consists in the use of a plurality of equalisers which are designed to equalise various lengths of the transmission line or cable whereby such equalisers can be readily selected for equalising certain lengths of the cablein cases where, for example, it is necessary to transmit signals at different tapping points along the transmission line or cable.
  • Fig. 1 illustrates diagrammatically a transmission line or cable with an equaliser constructed in accordance with the invention
  • Figs. 2 and 3 are explanatory diagrams
  • Fig. 4 is a diagram illustrating the type of equaliser section employed in the invention.
  • Figs. 5, 6,7, and 8 illustrate further forms of equaliser sections electrically equivalent to that shown in Fig. 4,
  • Fig. 11 illustrates a modified 'form of section for use at the highest frequencies of the band.
  • a short length of a transmission line which may be arranged as a balanced or unbalanced line is shown comprising two conductors l and 2.
  • the series resistance of the line and the series inductance are denoted by Re and L0 in series with a number of units each comprising an inductance and a resistance.
  • Re and L0 in series with a number of units each comprising an inductance and a resistance.
  • RA, LA, RB, LB, Rc, Lo are shown.
  • series impedances in the line are shown in one conductor only.
  • the impedances wLA and W113 are very small compared with their appropriate '"resistances so that the resultant circuit may be to L0 and the resistance has risen from
  • the impedance of. B is and if D consists of a resistance R2 in series with an inductance L2, its impedance will be R2+1iwLs. The product of these two impedances must be equal to Z0 and the following conditions are therefore obtained:
  • B and D In order that B and D shall give the required equalisation, it is necessary (a) that B should be small and D large, and (b) that they should work between impedances equal to Z0. Let it be assumed that B is made infinitely small and D infinitely large, then the equaliser becomes, in effect a line with uniformly distributed constants. Its characteristic impedance will, therefore, be
  • the equaliser section so obtained will equalise the effect of one of the single inductance-resistance units described above so that one equaliser section of this type will be required for each of the inductance-resistance units.
  • Figure l for example, three such units are illustrated so that in this case three corresponding equaliser sections are required.
  • the constants of the three equaliser sections will be different, but if they are designed in accordance with the above principles, they will each have the same characteristic impedance and can, therefore, all be connected in series without producing reflection ef.- fects.
  • the composite equaliser formed, in this example, by joining together the three equaliser sections would form an equaliser suitable for equalising a short length of the cable. Since the cable will have appreciable length, a number of these composite equalisers would be placed in series to build up a total equaliser having a length equivalent to that of the cable to be equalised.
  • the current ratios referred to were the complex ratics, and therefore, include both the attenuation and phase effects. It follows, therefore, that an equaliser designed in accordance with the above principles will equalise simultaneously both the attenuation and the phase of the cable.
  • the equaliser should consist of a large number of sections each equalising a very small length of cable so that the equaliser does, in effect, approximate to the case of an actual line in which the sections are infinitely finely distributed. Provided, therefore, that this condition of approximation to the infinitely finely divided sections is met the equaliser will equalise simultaneously both the attenuation and the phase of the cable.
  • the artificial line comprises, as will be seen from Figs. 1 and e, a plurality of series elements each comprising a condenser C1 arranged in series with the line and shunted by a resistance R1.
  • a shunt element comprising a resistance R2 in series with an inductance L2 the impedance of the shunt element with respect to the impedance Z0 oi the artificial line is the inverse of the series element to which it corresponds.
  • the product of the impedances of the series element and the corresponding shunt element is then equal to Z0 at all frequencies.
  • the first step is to measure the attenuation and phase constants of the transmission line over the desired range of frequencies.
  • the introduction of an artificial line will produce an attenuation equal to where R. is the total resistance of the artificial line, Z is the impedance of the artificial line (the impedance about which the series elements are inverted to obtain the shunt elements) w is the frequency in radians per second and T is the time constant of the condenser and resistance of the particular loading considered.
  • R and T The determination of values of R and T is most easily done by plotting a typical attenuation-frequency curve for the artificial line using logarithmic scales for attenuation and frequency.
  • This typical curve is obtained by giving R/Z and T any desired value, for instance, unity. Since the curve is plotted to logarithmic scales a change in the value of R/Z only results in moving the curve bodily up or down and does not change its shape. Similarly, changing the value of T does not alter the shape of the curve but merely moves it sideways.
  • a curve is then plotted for the transmission where the artificial line curve was fitted O1: should not exceed i the phase is simultaneously"equalised.
  • One of the series elements is replaced by two elements which are similar to one another and,
  • the original shunt element is also. replaced by two shunt elements, one corresponding to each of the two series elements.
  • .fI'he two series and two shunt elements are then connected to form two sections of a ladder network. 'I'henew attenuation of the line is then measured and compared with the attenuation before,v the sub-division. If no appreciable change is found, then the previous degree of approximation is sufficiently'accurate and sub-division of the. elements is unnecessary; When the artificial..line approximates to infinite distribution the propagation constantis proportional to the sum of. the impedances of the series elements.
  • the equaliser section described with reference to Fig. 4 may be replaced by a section which is electrically equivalent thereto,
  • two adjacent series elements of the equaliser comprising two resistances in series each shunted by a condenser
  • the resistance R2 and inductance L2 of Fig. 4 may, of course, be disposed at the left-hand side of the series element, as shown in Fig. 6 without affecting the characteristics.
  • the sections can be converted to sections of the T-type as shown in Fig. 7, or of the 1r type, as shown in Fig. 8.
  • the arrangement of the components of the sections in these last two mentioned figures will be clearly appreciated without further description whilst the values of the components compared with the values of the components of the section shown in Fig. 4 being indicated by the numerical prefixes. It will also be understood that by employing one of these types of section in conjunction with another type for an adjacent section, it is possible to combine some of the elements of the sections so as to obtain a different type of section.
  • the equaliser undergoes two forms of subdivision. Initially, the equaliser is divided into small sections so that the errors in fitting the attenuation curve are not of practical importance, such subdivision being a comparatively coarse one. The sections are subsequently divided more finely in order that the equaliser may approximate to the infinitely distributed case, in which event the phase and attenuation of the cable are simultaneously equalised.
  • the impedance will be independent of frequency and will be equal to Z0. If, however, the sections do not approximate to the infinite distribution, as is contemplated in accordance with a further embodiment of the invention, that is to say, when the attenuation varies either as a direct function of the frequency or as a direct function of the square root of the frequency, it has been found that the characteristic impedance of the equaliser varies with frequency and is only equal to Z at very high frequencies.
  • the equaliser is terminated with a constant impedance Z0, this termination will not be found correct over most of the frequency range resulting in reflection, and the attenuation and phase curves of the equaliser will differ from the theoretical curves calculated on the assumption of a correct termination and will thus give rise to difficulties in the design of the equaliser.
  • k represents the current ratio at zero frequency of the equaliser sections.
  • a constant resistance type of equalizer section instead of employing the artificial line type of equaliser described above use is made of a constant resistance type of equalizer section.
  • These sections are identical with the sections shown in Fig, 4, with the exception that in order to obtain a constant resistance an additional resistance equal to Z0 (i. e. a resistance substantially equal to the characteristic impedance of the cable) is inserted in parallel with the resistance R], as shown in Fig. 10. If, in this case, the equaliser is terminated by a constant impedance equal to Z0, it will be found that the input impedance is substantially constant and equal to Z0 at all frequencies within a predetermined range. It will of course be appreciated that other forms of con stant resistance section can be employed.
  • the equaliser sections in accordance with another feature of the invention are centred at successive frequencies which correspond to equal increments of loss on the cable attenuation-frequency curve.
  • the attenuation of a single equaliser section has a maximum value at zero frequency and gradually falls to zero as the frequency rises. At some frequency the: attenuation will have fallen to half its maximum value and this frequency is conveniently referred to as the centre frequency.
  • an equalised section is centred at a predetermined frequency by adjusting the time constant of the section so that at the predetermined frequency the loss of the section has fallen to half its maximum value.
  • k is the current ratio corresponding to the zero frequency attenuation of the equaliser section.
  • the attenuation curve of a cable can, over the greater part of the frequency range, be represented as the sum of two terms, one proportional to frequency and the other proportional to the square root of frequency. It is, therefore, possible to design two equalisers using the spacing factors at given above one equaliser equalising the attenuation which varies with frequency and the other attenuation which varies with the square root frequency. By combining these two equalisers it is possible to obtain a single equaliser which will simultaneously equalise the attenuation and phase of the cable while not requiring to be so finely divided that it approximates to the infinitely distributed case.
  • the centering of the section of the composite equaliser so formed will at any part of the frequency range depend on the proportion of the two terms mentioned above, and the spacing will, therefore, vary. Over the lower portion of the frequency range the attenuation varies as the root of frequency whilst at the higher frequncies a. term directly proportional to frequency becomes progressively prominent. At the low frequencies, therefore, the spacing of the section is substantially constant as stated above, but at the higher frequencies the spacing of the sections progressively increase.
  • the series element consists of a resistance R1 in parallel with a condenser C1 and an inductance L3 in series whilst the shunt element consists of an inductance L2 and a resistance R2, the inductance L2
  • the inductance L3 is provided in series with the condenser C1 and the condenser C2 is also added in shunt with the inductance L2.
  • the values of C2 and L3 are chosen so that at a predetermined frequency C2 resonates with L2 and L3 with C1.
  • the effect of these added components is to cause the attenuation curve of the equaliser section to fall off more rapidly over a part of the frequency range up to the resonant frequency so that the same rate of change of attenuation can be obtained with one section of this type that could be obtained with a large number of the normal type.
  • the equaliser at the end of the cable must be capable of adjustment to suit the different lengths of the cable due to the different tapping points.
  • the correct equaliser for a four-mile section by omitting every other section of the equaliser which is necessary for the eight-mile section.
  • the correct equaliser for a two-mile section can be obtained by omitting every other section from a four-mile equaliser, and so on.
  • the above-described method of correction does not remove the reduction of velocity at low frequencies due to the Heaviside condition not being satisfied.
  • This low frequency effect can be eliminated by inserting series capacity loading as described in the specification of British Patent No. 455,492. Since the characteristic impedance of a series capacity loaded cable is that of a condenser in series with a resistance, it is not possible to insert the artificial lines, the characteristic impedance of which is a pure resistance, at intermediate points in the line.
  • the artificial line may be connected to the transmission line through a condenser equal to the series capacity of the transmission line, the characteristic impedance of the artificial line being equal to the resistive term of the characteristic impedance of the transmission line. The line is thus correctly terminated.
  • the artificial line may be connected in a repeater between. two sections of the transmission line.
  • Partial equalisation at high frequencies may also be obtained in the manner described in the provided additional equaliser sections being provided between additional amplifier stages.
  • a system for transmitting electric signals of frequencies within a range covering at least about kilocycles comprising a transmission line of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby causing variations of attenuation and phase delay resulting in distortion of said signals, and a plurality of equaliser sections all connected in series with said line, said sections comprising a series element and a shunt element, said series element composed of resistance shun ed by capacity, said shunt element composed of inductance in series with resistance, said elements being substantially different for different sections as to time constant and magnitude of the components and being so chosen as to substantially and simultaneously compensate for the greater part of said variations.
  • a system for transmitting electric signals of frequencies within a range covering at least about kilocycles comprising a transmission line of the type as exemplified by a cable, having its primary constants varying with frequency Within said range, thereby causing variations of attenuation and phase delay resulting in distortion of said signals, means for introducing said signals into said transmission line, and a plurality of equaliser sections all connected in series with said line, said sections comprising a series element and a shunt element, said series element composed of resistance shunted by capacity, said shunt element composed of inductance in series with resistance, said resistance of said series element being small compared With said resistance of said shunt element, the time constant and the magnitude of the components of said elements being substantially different for different sections and being so chosen as to substantially and simultaneously compensate for the greater part of said variations.
  • a system for transmitting electric signals of frequencies within a range covering at least about 100 kilocycles comprising a transmission line of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby causing variations of attenuation and phase delay resulting in distortion of said signals, and a plurality of equaliser sections all connected in series with said line, said sections comprising a series element and a shunt element, said series element composed of resistance shunted by capacity, said shunt element composed of inductance in series with resistance, said resistance of said series element being small compared with said resistance of said shunt element, said elements being substantially different for different sections as to time constant and magnitude of the components and being so chosen as to substantially and simultaneously compensate for the greater part of said variations within a selected portion of said line.
  • a system for transmitting electric signals of frequencies within arange covering at least about 100 kilocycles comprising a transmission line of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby causing variations of attenuation and phase delay resulting in distortion of said signals, and a plurality of equaliser sections all connected in series with said line, said sections comprising a series element and a shunt element, said series element composed of resistance shunted by capacity, said shunt element composed of inductance in series with resistance, said elements being substantially different for different sections as to time constant and magnitude of the components and being so chosen as to substantially and simultaneously compensate for the greater part of said variations, the number of said sections being chosen so as to approximate substantially an infinitely fine distribution of said sections.
  • a system for transmitting electric signals of frequencies within a range covering at least about 100 kilocycl-es, up to and including television range comprising a transmission line of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby causing variations of attenuation and phase delay resulting in distortion of said signals, and an artificial line connected to said transmission line and comprising a plurality of equaliser sections all in series with said transmission line, said sections comprising a series element and a shunt element, said series element composed of resistance shunted by capacity, said shunt element composed of inductance in series with resistance, the time constant and the magnitude of the components of said elements being substantially different for different sections and being so chosen that the total of the variations of attenuation and phase delay, causing distortion of said artificial line and of said transmission line together are zero to a desired substantial degree.
  • a system for transmitting electric signals of frequencies within a range covering at least about 100 kilocycles, up to and including television range comprising a transmission line of the type as exemplified by a cable, having its primary con,- stants varying with frequency within said range, thereby causing variations of attenuation and phase delay resulting in distortion of said signals, means for introducing said signals into said transmission line, and an artificial line connected to said transmission line comprising a plurality of equaliser sections all in series with said line, said sections comprising a series element and a shunt element, said series element composed of resistance shunted by capacity, said shunt element composed of inductance in, series with resistance, said elements being substantially different for different sections as to time constant and magnitude of the components and being so a chosen that said sections form constant resistance sections and the total of the variations of attenuation and phase delay, causing distortion of said artificial line and of said transmission line together are zero to a desired substantial degree.
  • a system for transmitting electric signals of frequencies within a given substantial range comprising a transmission line, of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby producing variations of attenuation and phase delay resulting in distortion of said signals, said variations of attenuation comprising the sum of a pair of terms, one of said terms varying substantially as the square root of said frequency, the other varying substantially directly as said frequency, and two equalizers composed of equaliser section groups connected all in series with said line, the components in one of said groups being substantially different for diiferent sec i tions and being so chosen that the greater part of the variation corresponding to said term varying as the square root of frequency is compensated, the components in the other of said groups being substantially different for different sec tions and being so chosen that the variation corresponding to said other term is substantially compensated, and that the variations of phase delay causing distortion are substantially compensated simultaneously.
  • a system for transmitting electric signals of frequencies within. a given range comprising a transmission line of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby producing variations of attenuation and phase delay resulting in distortion of said signals, said variations of attenuation comprising a term varying substantially as the square root of said frequency, and a group of equalizersections connected in series with said line, the components of said group being so chosen that the attenuations of said sections fall to half at predetermined frequencies within said range, said latter frequencies being arranged at substantially equal increments of attenuation on the curve representing said term varying as the square root of said frequency.
  • a system for transmitting electric signals of frequencies within a given range comprising a transmission line of the type as exemplified by a cable, having its primary constants varying withfrequency within said range, thereby producing variations of attenuation and phase delayresulting in distortion of said signals, said variations of attenuation comprising a term varying substantially directly as said frequency, and a group of equaliser sections connected in series with said line, the components of said group being so chosen that the attenuations of said sections fall to half at predetermined frequencies within said range, said latter frequencies being arranged at substantially equal increments of attenuation on the curve representing said term varying directly as said frequency.
  • a system for transmitting electric signals of frequencies within a given range comprising a transmission line, of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby producing variations of attenuation and phase delay resulting in distortion of said signals, said variations of attenuation comprising the sum of a pair of terms, one of said terms varying substantially as the square root of said frequency, the other varying substantially directly as said frequency, and two groups of equaliser sections connected all in series with said line, said equaliser sections comprising series and shunt elements, said series elements composed substantially of resistance shunted by capacity, said shunt elements composed substantially of inductance in series with resistance, the components in one of said groups being substantially different for different sections and being so chosen that the greater part of the variation corresponding to said term varying as the square root of said frequency is substantially compensated, the components in the other of said groups being substantially different for different sections and being so chosen that the variation corresponding to said other term is substantially compensated, and that the variations of phase delay causing distortion
  • a system for transmitting electric signals comprising a transmission line of the type as exemplified by a cable, the attenuation of which can be represented by the sum of two terms, one proportional to frequency and the other proportional to the square root of frequency, and a plurality of equalizer sections, said equalisers being of the constant resistance type, the spacing of said sections correspond to a: increment of loss on the attenuation curve of said line the value of a: for that part of the attenuation. which varies directly with frequency being substantially equal to,
  • A represents the total series-impedance of the respective equalizer section and Z the characteristic impedance of said line.
  • a system for transmitting electric signals of a range including lower and higher frequencies comprising a transmission line of the type as exemplified by a cable, the attenuation of which varies substantially as the square root of the frequency range within said lower frequency range and more rapidly within said higher frequency range, and a plurality of equalizer sections, said sections equivalent to, and including, series elements and shunt elements, said series elements substantially composed of resistance shunted by capacity, said shunt elements substantially composed of inductance in series with resistance, part of said sections arranged for compensating said transmission line as far as its attenuation varies substantially as the square root of the frequency and the other part of said sections arranged for compensation of higher frequencies, the impedance and time constant of said first part of sections being adjusted so that their attenuations fall to about half of their maximum value at frequencies corresponding substantially to equal loss increments on the attenuation-frequency curve of said transmission line within said lower frequency range, the impedance and time constant of said other part of sections being adjusted so that their attenuations fall to about half
  • a system for transmitting electric signals terms one proportional to frequency and the other to the square root of frequency, and two groups of equalizers, each composed of sections centered at frequencies corresponding substantially to equal loss increments of attenuation with respect to one of said turns, one of said groups adjusted so as to substantially equalize the attenuation of said line which varies directly with frequency, the other of said groups adjusted so as to substantially equalize the attenuation which varies as the square root of frequency.
  • a system for transmitting electric signals of frequencies within a given range comprising a transmission line of the type as exemplified by a cable, having its primary constants varying with frequency within said range, thereby producing variations of attenuation and phase delay resulting in distortion of said signals, said variations of attenuation in the lower frequency portion of said range approximating to a variation as the square root of frequency, and a plurality of equalizer sections connected in series with said line, said equalizer sections comprising series and shunt elements, said series elements composed substantially of resistance shunted by capacity, said shunt elements composed substantially of inductance in series with resistance, the components of said sections being so chosen that the attenuations of said sections fall to half at pre-- variation of attenuation at substantially equal in-- crements of attenuation within said lower portion of said range, and at progressively increasing increments of attenuation in the higher. frequency portion of said range, so as to substantially and simultaneously compensate said variations of attenuation. and phase delay.
  • the equalizer sections possess an image impedance which varies with frequency, an impedance arranged for terminating said sections, said im pedance' consisting of a resistance in series with a further resistance, said latter resistance shunted by a condenser.
  • a system for transmitting electric signals of frequencies within a range covering at least about 100 kilocycles comprising a transmission line of the type as exemplified by acable, having its primary constants varying with frequency within said range, thereby causing variations of attenuation and phase delay so as to cause distortion of said signals, means for introducing said signals at a number, including one, of points along said line spaced from its ends, and a plurality of equalizers, each equalizer possessing a pluralityof equaliser sections, the elements of the sections being substantially different for different sections and being so chosen that each equaliser equalisesr an associated substantial length of line so that the distortions of said signals injected at said point, due respectively to said variations of attenuation and phase delay, are substantially and simultaneously equalised.
  • a system for transmitting electric signals comprising a transmission line of the type as exemplified by a cable, the variation of attenuation of which with frequency causing distortion of said signals can be represented by the sum of two terms, the first of said terms proportional to frequency of said signals and the second of said terms proportional to the square root of saidfrequency, and two groups of equaliser sections, the components of one of said groups being substantially different for different sections and adjusted so as to substantially equalise the attenuation represented by said first term, the components of the other of said groups being substantially different for different sections and adjusted so as to substantially equalise the attenuation represented by said second term.
  • a system for transmitting electric signals comprising a transmission line 'of the type as exemplified by a cable, the variation of attenuation of which with frequency causing distortion of said signals can be represented by the sum of two terms, the first of said terms proportional to frequency of said signals and the'second of said terms proportional to the square root of said frequency, and two groups of equaliser sections, the components of one of said groups being substantiallyvdifferent for different sections and adjusted so as to substantially equalise the attenuation represented by said first term, the components of the other of said groups being substantially different for difierent sections and adjusted so as to substantially equalise the attenuation represented by said second term, all of said sections being of the constant resistance type, and those in said group equalising the attenuation represented bys aid first term being centred at frequencies corresponding to increments in said first term substantially equal to while those in said group equalising the attenuation represented bysaidsecond term are centred at frequencies corresponding to increments in said second term substantially equal to ln:

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Multimedia (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
US127924A 1936-03-03 1937-02-26 Electric signal transmission system Expired - Lifetime US2158978A (en)

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GB6483/36A GB476799A (en) 1936-03-03 1936-03-03 Improvements in or relating to electric signal transmission systems
GB3186537A GB495815A (en) 1939-02-10 1937-02-18 Improvements in or relating to electric signal transmission systems
GB443839A GB524907A (en) 1939-02-10 1939-02-10 Improvements in or relating to wave transmission systems

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2768355A (en) * 1952-05-31 1956-10-23 Bell Telephone Labor Inc Transmission line with impedancematching terminations
US3750052A (en) * 1970-12-11 1973-07-31 Int Standard Electric Corp Adjustable frequency-dependent equalizer
US4718100A (en) * 1985-03-15 1988-01-05 Brisson Bruce A High current demand cable
US20050052255A1 (en) * 2003-09-05 2005-03-10 Infinera Corporation Transmission line with low dispersive properties and its application in equalization
US20090099026A1 (en) * 2004-04-20 2009-04-16 Sumitomo Electric Industries Ltd Method of processing width of superconducting wire rod

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE741788C (de) * 1939-01-20 1943-11-17 Telefunken Gmbh Schaltungsanordnung zur Phasen- und Daempfungsentzerrung von elektrischen UEbertragungssystemen
AU2009290143A1 (en) * 2008-09-05 2010-03-11 Sato Holdings Corporation Impedance compensation in an RF signal system

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2768355A (en) * 1952-05-31 1956-10-23 Bell Telephone Labor Inc Transmission line with impedancematching terminations
US3750052A (en) * 1970-12-11 1973-07-31 Int Standard Electric Corp Adjustable frequency-dependent equalizer
US4718100A (en) * 1985-03-15 1988-01-05 Brisson Bruce A High current demand cable
US20050052255A1 (en) * 2003-09-05 2005-03-10 Infinera Corporation Transmission line with low dispersive properties and its application in equalization
US7446622B2 (en) 2003-09-05 2008-11-04 Infinera Corporation Transmission line with low dispersive properties and its application in equalization
US20090099026A1 (en) * 2004-04-20 2009-04-16 Sumitomo Electric Industries Ltd Method of processing width of superconducting wire rod

Also Published As

Publication number Publication date
FR55162E (fr) 1951-10-02
FR833987A (fr) 1938-11-09
FR57145E (fr) 1952-12-15
FR818700A (fr) 1937-10-01
GB541882A (en) 1941-12-16
GB476799A (en) 1937-12-03
US2165838A (en) 1939-07-11
FR54937E (fr) 1951-04-30
GB524908A (en) 1940-08-16

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