US2226026A - Frequency transposer or converter and circuit therefor - Google Patents

Frequency transposer or converter and circuit therefor Download PDF

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Publication number
US2226026A
US2226026A US177762A US17776237A US2226026A US 2226026 A US2226026 A US 2226026A US 177762 A US177762 A US 177762A US 17776237 A US17776237 A US 17776237A US 2226026 A US2226026 A US 2226026A
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filter
frequency
frequencies
input
band
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Stieltjes Frederik Hendrik
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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
    • 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
    • H03C1/54—Balanced modulators, e.g. bridge type, ring type or double balanced type
    • H03C1/56—Balanced modulators, e.g. bridge type, ring type or double balanced type comprising variable two-pole elements only
    • H03C1/58—Balanced modulators, e.g. bridge type, ring type or double balanced type comprising variable two-pole elements only comprising diodes

Definitions

  • the invention refers to frequency transposers or converters of the type in which one or more input frequencies are output into one or more desired transposed frequencies by means of a transposing frequency. More in particular the invention refers to such transposers in which the frequencies generated caused by retroaction further undesired frequencies to be generated besides the original frequencies supplied for transposition.
  • transposers An important group of such transposers are modulators; the subgroup known as inversion modulators for instance satisfies the above description. Primarily the present specification will for simplicitys sake be limited to this subgroup. The latter part of the specification will indicate to which further groups of transposers the inventive idea, as exemplified with reference to the example of the subgroup of inversion modulators, may be applied.
  • the invention is likewise applicable to make and break modulators, as well as to such modulators working with complete interruption as to those where the periodic interruption is not absolute.
  • a simple interruption modulator of the first kind will not be suitable for the application of the invention, for such a modulator would not function at all if provided 5 with reactances according to the invention. It is seen at once that such is the case if it be borne in mind that at both ends of such a modulator the current would periodically be fixed in value, viz. at zero, which evidently will only be possible if either the currents are identically zero, or beside the currents of desired frequency currents of other frequency may fiow. This requirement is not to be reconciled with what has been said in the above about the reactances to be connected.
  • the transposing frequency does not or only very slightly participates in the energy exchange and that the energy exchange between the frequency (frequencies) to be transposed and the transposed frequency (frequencies) is practically without losses.
  • the field of apnlication of the invention may thus be described by combining the above requirements.
  • the invention may then be defined by stating, that in such a frequency transposer the connected elements will have low impedances to undesired frequencies at those terminals where the currents are dependent on the quantities at other terminals, whereas these impedances are high at other terminals.
  • transposers realizing the invention, but which are distinct from the simple examples described in the above, e. g. due to the transposer being built up of two partial transposers, which of themselves do not satisfy the requirement, or due to the presence of more than two pairs of terminals, in which case matrix relations will in general exist between those pairs, these relations being reducible in the case of two pairs of terminals (not counting those of the transposing frequency) to a reciprocity relation.
  • the latter may subsidiarily be used as a basis for describing the limits of the invention, such, that at any moment the ratio between input and output currents equals the ratio between output and input voltages. If the field of the invention is thus described, its definition, viz.
  • a transposer embodying the invention may be usefully applied in a number of circuits.
  • Such a transposer might, for instance, be incorporated in a filter circuit, which to that end would be opened up at a certain point, such point being arbitrarily subject to the requirement that the nature of the impedances to both sides of the transposer conform to the conditions given above as long as provisions have been made that a frequency transposition will have occurred behind the transposer, so that the filter elements in the filter part concerned will have to be suitably transformed with respect to the elements in the remaining portion of the filter.
  • a band filter will be described below consisting of an initial part and a latter part with a frequency transposer arranged bet ⁇ veen,the initial part passing the band from f1 to f1+f2, and the latter part passing the band from f1+fo to f1+f2+fo.
  • a frequency transposer arranged bet ⁇ veen
  • the initial part passing the band from f1 to f1+f2
  • the latter part passing the band from f1+fo to f1+f2+fo.
  • Figure l is a diagrammatic illustration of an inversion modulator comprising contiguous filters
  • Figure 2 is an equivalent or explanatory diagram of an inversion modulator, by reference to which certain fundamental relations can be readily explained;
  • FIG. 3 illustrates one embodiment of transposition filter according to the invention
  • Figure 4 is an explanatory diagram similar to Figure 2;
  • FIG. 7 is an explanatory circuit diagram
  • Figure 8 is a curve of certain values in a constant-K filter.
  • FIGS 9, l0 and 11 diagrammatically illustrate other arrangements of filter parts, transposer, etc.
  • S is an inversion modulator of known type made up of contact rectifiers, the polarisation voltages of which are controlled by the transposing frequency in.
  • the inversion modulator is connected to an input filter I and an output filter B.
  • the elements shown connected inter se and with an incoming and an outgoing line by transformers 1-6.
  • the voltage of frequency f0 has a considerable amplitude, whereby currents arriving on the winding 3 and having a single harmonic frequency f1 will be converted into currents in winding 4 consisting of a frequency spectrum containing components fi-l-fo, i-fn etc.
  • the discussion will in the first instance be limited to the case where the winding 1 is connected to a low-frequency incoming line.
  • the filter I may then be a low-pass filter.
  • the filter B may then be a band filter with a pass range from e. g. It to fO+f1.
  • the frequency f1 may be taken as representative of the low frequency alternations (e. g. of a speech band) arriving on the low frequency line. If we take for instance the case 6 are explanatory curve diaof a long carrier frequency line with terminal installations conforming to Fig.
  • low frequency lines may immediately be connected tothe low-pass filters, and thus a speech channel might be formed via the carrier line, the said channel only comprising simple filters and inversion modulators; the latter hardly have any losses, so that amplification of the currents is not required.
  • the low damping in the inversion modulators is obtained by making the impedance of the filter I as seen from the winding 2 low for frequencies outside the pass range. and the impedance of the filter B high for frequencies outside the pass range.
  • the impedance of the filter I as seen from the winding 2 low for frequencies outside the pass range.
  • the impedance of the filter B high for frequencies outside the pass range.
  • the alternative might also be the case.
  • Fig. 2 the supply frequency and the frequencies formed at the input are shown in the rows and the frequencies produced at the output are shown in the columns. Only a few of the infinite number of frequencies produced are shown.
  • the diagram represents the interaction between voltages and currents of different frequency as if their frequencies were equal.
  • the transformers which are illustrated here in a symbolical sense, have a transforming as well as a transposing action, the latter being however without interest to the interaction as such.
  • the transposition will have to be taken into account, so that for instance the impedances to be connected in the diagram to the terminals f13fo should be calculated to the frequency f1--3fc; if this frequency is negative this should also be taken into account.
  • the use of the diagram may, for instance, be exemplified by assuming the above condition to be fulfilled, viz. that with a view to reducing the losses, the output presents shorts to a number of undesired frequencies such as f13fo. J1Jo, f1+3fo, f1+5f0 etc. so that only f1+fo remains. Then the prevention of energy losses at the input in the sense of the invention is obviously only possible by there providing open circuits for the undesired frequencies f1+2fo, f12fo etc., taking care that only the frequency f1 finds an impedance differing from zero.
  • the ratio between the voltages f1 and f1+fo will be determined by the central transformer and thus the voltage at f1+fo will be 1r/2 as great as that at f1.
  • Fig. 3 shows a band filter containing a transposer or converter.
  • the filter consists of an initial part BI and a latter part BU between which a. transposer S is introduced.
  • the part BI is designed for passing a band of frequencies from ii to f1+f2; the part BU for transmitting a band from f1+fo to f1+f2+fc.
  • the transposition occurs from the first mentioned band to the latter band.
  • the initial part ends in a complete shunt impedance and the latter part begins with a complete series impedance.
  • This requirement might, of course, also be satisfied by entirely separating the initial and the latter part and by ending one part at mid-shunt and the other at mid-series.
  • the transmission through S would seriously be impaired at the limits ,of the range to be transmitted, because the impedance of the mid-series network approaches zero at the limits, then again to increase outside the pass range.
  • the impedance of the mid-shunt network approaches infinity at the limits, before it decreases.
  • a filter made up like that of Fig. 3 may also be designed for the transition of low frequency signalling to double side band, in which case the impedance ratio should however be 1 /2, as may at once be seen from the equivalent diagram.
  • the total attenuation of a modulator if connected between resistances is equal to 1n 7r/2+b, I) being the attenuation of the modulator proper; and if the invention is applied it equals Area sinh 1r/2 sinh b.
  • the invention is applicable to power transposers or converters as well as to transposers or converters for communication systems.
  • the invention thus also refers to a transposition filter permitting the formation of combination frequencies and filtering the same; and furthermore refers to a filter therefor, the general nature of which has been described above.
  • both the initial and the latter parts might exercise a filtering action; viz., the initial part may have a low frequency selective action and the latter part a high frequency selective action for separating the desired transposed frequency from the undesired frequencies resulting from the transposition. It has been described above how the frequencies produced at the transposer output will occasion by retroaction on the input the desired (i.
  • the side bands are produced in pairs. If single side band transmission is desired one of those side bands will be a desired frequency (group) and the other an undesired frequency (group). It has been discovered that in the absence of suitable precautions, in some cases the side band situated in the attenuation region of the latter part filter will exert an infiuence on the impedance of this filter to the side band situated in the pass range of the filter, the adaptation of the initial and latter parts being thereby disturbed.
  • the invention consists in this aspect mainly in means for preventing this undesired effect, the nature of which means may best be explained from the diagram shown in Fig. 2, by retaining only the rows for f1 and the columns for ,71-10 and f1+fo; thus the diagram of Fig. 4 is obtained.
  • the filter connected to the transposed output is represented in the diaphragm by two ideal filters for the side bands; it is seen that these are in this case series-related.
  • Fig. 5 shows the real parts I of the impedance of a latter part as a function of the audio-frequency, as well as the reactive components 8 and 9; the carrier is supposed to lie at the border of the band.
  • the filter in question has, for its admittance, the midshunt admittance of a constant-K filter completed by a shunt-branch of conductivity equal to 0.3 of that of the full shunt-branch of that constant-K filter.
  • Fig. 6 shows, for a certain case, the components of the initial part as seen from the transposer. According to the invention the sum of the reactive impedance components (taking into account the occurring transpositions and transformations) is as near as possible equal to zero.
  • the mutual disturbance in the present case corresponds entirely to that occurring in the case of Fig. 7, if, to the band filters there shown, the pass and attenuation ranges of which are mutually reciprocal, a frequency is applied which is passed by the one filter and attenuated by the other.
  • the characteristic impedance of the source may be a resistance R; as far as the real components are concerned, the impedance of the pass filter need, in this case only, be reckoned with; the real component of this impedance should equal R.
  • the symbol .r is used as follows: (1) when the filter terminates on a shunt branch, :1: signifies the ratio of the admittance of this branch to the admittance of the full shunt branch in the filter; (2) when the filter terminates on a series branch, at signifies the ratio of the impedance of this branch to the impedance of the full series branch in the filter.
  • Fig. 8 shows the real and the imaginary parts of a certain constant-K filter.
  • the real component evidently varies rather strongly over its entire frequency range (the pass range), which fact in general is objectionable if the filter must be combined with other elements.
  • filters and in particular also the transposition filter according to this part of the invention, in such a manner that their input impedances at the input and the output show a given characteristic normalized for filters in general.
  • This characteristic may be more or less flat, as is shown by the dot-dash line in Fig. 8 for the case there shown.
  • the dot-dash line may be obtained from the full-drawn curve for the filter in question, of which Fig.
  • this principle may quite easily be applied by constructing the filter for instance with an initial part comprising, as seen from the transposer, an inductance-preferably equal to 1.4/1r of the inductance present in the series branch of the constant-K band filter having the same nominal characteristic impedance and the same band width as the filter used in the latter part-optionally in series with a condenser for establishing resonance for a low frequency in the pass range, this inductance, o. q, this resonant circuit having to be followed by an impedance with the least possible reactance and equal to 4/1 times the characteristic impedance of the band filter.
  • Fig. 10 which shows considerable similarity to Fig. 9, illustrates a transposition filter with input terminals at the left hand side, and at the right hand side the beginning of the band filter constituting the latter part. This beginning thus shows similarity with the parts 1 and g of Fig. 9.
  • the transposer T is shown connected before this beginning, and said transposed is supplied with the frequencies to be transposed via the circuit element 12' and with the transposing frequency S.
  • the circuit element It has the same function as the element h in Fig. 9, which was described above.
  • a frequency transposing system the combination of a low-pass filter connected with a signal source, a band-pass filter connected with a load circuit, and transposing means coupled with said filters and supplied with a transposing frequency, said band-pass filter having an input impedance corresponding substantially to that of a constant-K filter characterized by a 0.8 input shuntbranch, said low-pass filter comprising a series inductance adjacent to the transposer having 1.4/1r of the inductance present in the series branch of the constant-K filter having the same nominal characteristic impedance and band width as said band-pass filter.
  • a low-pass filter connected with a single source, a band-pass filter connected with a load circuit, and transposing means coupled with said filters and supplied into a transposing frequency
  • said band-pass filter having an admittance substantially equal to that of a constant-K filter having a 0.8 shuntinput branch
  • said lowpass filter comprising adjacent to the transposer a parallel capacity of 1.4/1r the capacity present in the shunt-branch of the constant-K filter having the same nominal characteristic impedance and band width as said band-pass filter.
  • a low-pass filter connected with a signal source, a band-pass filter connected with a load circuit, an input transformer comprising a primary winding connected with said low-pass filter and a secondary winding provided with an intermediate tap, an output transformer comprising a secondary winding connected with said band-pass filter and a primary winding pro vided with an intermediate tap, a source of transposing frequencies connected with said intermediate taps, and a network of rectifiers establishing unilateral conductivity from the ends of said output transformer primary to the ends of said input transformer secondary, and establishing transposed unilateral conductivity from the ends of said input transformer secondary to the diagonally opposite ends of said output transformer primary, said band-pass filter comprising a series inductance at its input end presenting high impedance to undesired frequencies, said low-pass filter presenting low impedance to undesired frequencies.
  • a low-pass filter connected with a signal source, a band-pass filter connected with a load circuit, an input transformer comprising a primary winding connected with said low-pass filter and a secondary winding, an output transformer comprising a secondary winding connected with said band-pass filter and a primary winding, a network of rectifiers establishing unilateral conductivity from the ends of said output transformer primary to the ends of said input transformer secondary, and establishing transposed unilateral conductivity from the ends of said input transformer secondary to the diagonally opposite ends of said output transformer primary, and a source of transposing frequencies connected with said network, said band-pass filter having an input impedance corresponding substantially to that of a constant-K filter characterized by a 0.8 input shunt-branch; said lowpass filter comprising a series inductance having 1.4/1r of the inductance present in the series branch of the constant-K filter adjacent to the transposer having the same nominal characteristic impedance and band-pass width as said band-pass filter.
  • the method of filtering and transposing frequencies wherein one or more input frequencies are transposed to one or more desired output frequencies by the action of a transposing frequency and wherein the input voltages are dependent on the output currents and voltages and at the same time the output currents are dependent upon the input currents and voltages which comprises supplying the input frequencies through an input filter section, discharging the output frequencies through an output filter section, supplying the transposing frequency to transposing means coupled between said filter sections, and presenting low impedance to undesired frequencies in one of said filter sections adjacent to the transposer and high impedance to undesired frequencies in the other filter section adjacent to the transposer while retaining normal filtering characteristics, whereby the transposlng frequency participates only to a slight extent in the energy transfer, and whereby the energy transfer between the input frequency or frequencies and the output frequency or frequencies is substantially free of losses.
  • Filtering means for use as an input and output of a system comprising a low frequency source and a modulator, said filtering means having an output termination in the form of a bandpass filter including an input impedance corresponding specifically to that of a constant-K filter characterized by a 0.8 input shunt-branch, and a low-pass filter in the input comprising a series inductance adjacent to the modulator having 1.4/1 of the inductance present in the series branch of the constant-K filter having the same nominal characteristic impedance and band width as said band-pass filter.
  • a system of the class described comprising a frequency transposer acting to establish correspondence between different current/voltage phenomena, each phenomenon being determined by a definite frequency and a definite set of transposer terminals, certain phenomena being moreover desired in the system and certain other phenomena being undesired, the phenomena being divisible into two groups A and B, such that the current values of the A phenomena are completely determined, due to the transposer action, by the current and voltage values of the B phenomena, whereas the voltage values of the B phenomena are likewise determined by the current and voltage values of the A phenomena, the algebraical sum of the energy fiuxes into the transposer due to the action of the combined phenomena being practically Zero, networks being connected to the transposer such that in as high a degree as possible for the undesired phenomena, the A phenomena are limited to their current aspect and the B phenomena to their voltage aspect.
  • transposer action is such that the transposer may be considered to be replaced by a set of m columns of mn transformers grouped in 11. rows (if the A group contains m phenomena and the B group n phenomena), each of the transformers having a frequency transposing tion (from one of the m A phenomena to one of the n B phenomena) as well as a voltage and current transforming action, the primary windings of the row transformers corresponding to a single B phenomenon being connected in series, and the secondaries of the n column transformers belonging to a single A phenomenon being connected in parallel.
  • a system according to claim '7 characterized in that for those undesired phenomena to which complete application of the rule of claim 7 has not been possible, as well as for the desired phenomena, the networks joined to the transposer are such that at the junctions for as many of the desired phenomena as possible, and otherwise for suitable combinations of phenomena including desired phenomena, conditions of optimum energy transfer exist, or are approximated, these implying joined impedances being conjugate complexes,
  • a filter for frequency converting systems of the class described the combination of a low-pass filter portion in the input and a band-pass filter portion in the output, said bandpass filter portion having an admittance equal to that of a constant-K filter having an 0.8 input shunt-branch, said low-pass filter portion comprising a parallel capacity of 1.41r the capacity present in the shunt branch of a constant-K filter having the same nominal characteristic impedance and band width as said band-pass filter portion.
  • Patent No. 2,226,026 is a patent No. 2,226,026.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
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  • Filters And Equalizers (AREA)
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US177762A 1936-12-04 1937-12-02 Frequency transposer or converter and circuit therefor Expired - Lifetime US2226026A (en)

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NL266216X 1936-12-04

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US (1) US2226026A (xx)
BE (1) BE425004A (xx)
CH (1) CH266216A (xx)
DE (1) DE905381C (xx)
GB (1) GB506790A (xx)
NL (1) NL55869C (xx)

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BE511435A (xx) * 1951-05-18

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DE589696C (de) * 1933-12-13 Lorenz Akt Ges C Verfahren zur Vermeidung des Klirrfaktors bei modulierten Roehrensendern durch Kompensation der Verzerrungen mittels gleichgerichteter, modulierter Hochfrequenz
US1448702A (en) * 1920-07-10 1923-03-13 American Telephone & Telegraph Translating circuits
US1672056A (en) * 1924-12-22 1928-06-05 American Telephone & Telegraph Translating circuit

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GB506790A (en) 1939-05-26
CH266216A (fr) 1950-01-15
DE905381C (de) 1954-03-01
NL55869C (xx)

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