US2203746A

US2203746A - Radio frequency distribution system

Info

Publication number: US2203746A
Application number: US228306A
Authority: US
Inventors: Roosenstein Hans Otto
Original assignee: Telefunken AG
Current assignee: Telefunken AG
Priority date: 1937-07-29
Filing date: 1938-09-03
Publication date: 1940-06-11
Anticipated expiration: 1957-06-11

Description

SUBSTITUTE FOR MISSIIENG am June; 11, 1940. H. c. ROOSENSTEIN 2,203,745

5mm FRE -mum ms'mmn'ton SYSTEM Filed Sept. 5, 193a.

l i e 7- LA K 5 a L;

INVENTOR umuszzaamuwsnnw ATTORNEY I 2203TQ6 j 5 OR IN 333/8 m Patented June 11, i2

arctic- 'UNE'EED sra'ras Paras-r GFFECE rispzo'rnreunuor nrs'mrsurzox srsm Hans Oiio'Eoose-nstein, Berlin-Tempelhof, Germany.- asa'gnor to Teleinnken Gcsellscliaft fiir' Drahtlose Telegraphic m. 1:. PL, Berlin, Ger- V many, a. corporation of Germany Application September 3, 1938. Serial'No. 228,306 In Germany July 29, 1937.

Claims. (0:. t's-45y A serious trouble met with in a great many practical cases s that in R. 3-. receivers or amplifiers the input impedance for the lead-in is non-ohmic in nature.

:- inputpotential, for instance. to be Taried by means of a series res stance cu: in the line and being of ohmic nature, this :egulazlon will become a function of the frequency as a result of the fact that the input resistazce of :ne receiver or amplifier depends upon :he frequency. A case of this kind is me: with. for instance, in

communal or party reception of television programs where the incoming video are ampiified in a communal antenna amplzier and are thereupon transmitted to a party or feeder line (for instance, by way of an intermediate "carrier"), whence leads are brought to the various receivers. have available ways and means adapted to adjust the picture brightness or b. :e, and in this connection one essential condizion is that this amplitude regulation or Tatiana-should be accomplishable under conditions unaiected by frequency, in other words. so thatthe action willbe equal and uniform throughout the whole frequency band. However,' such freedom from frequency effects within the entire frequency band as required in practice will be assuredonly if the receiver represents a p r ohmic input re- 80 sistance.

According to the invention. the input impedance of the receiver or amrflifier forms a part of a chain structure or recurrent network comprising inductances, capacities; and optionally also ohmic resistances, which network, when looking at it from the downlead end. represents an ohmic resistance which, is independent of the frequency within a certain desired frequency band. The size oftliis ohmic resistance may be adjusted at will by choosing suitable values for the constituent elements of the chain or .net work structure.

The invention shall now be explained in more detail by reference to the attached drawing wherein Fig. 1 shows a circuit embodying the invention coupled to the input of an R. F. receiver. Fig. 2 shows a practical embodiment and use of the circuit scheme shown in Pig-1. and Figs.

3 and 4 are modified forms of the circuit shown in Fig. 1. Referring to Fig.1.- E denotes the receiver and C: connected across its input terminals represents its input capacity.- Girls will, as a matter of fact, be true inmost instances.) In the conventional type of receiver schemes the said capacity will mcin'y consist of the grid-fila- More particularly,- it the In such a scheme it is desL-able to meat capacitance of the first or input tube, or

else. in the case of television receiver apparatus, it will consist, for instance, of the input capacity of the Braun cathode-ray tube. Capacity C: is tuned by the inductance Le to the mean frequency of the frequency band to be transmitted, and this circuit is suitably used to form one of two equivalenz cross arms of a chain structure or network, the line or series arm of which consists of the tuned series cont: ice-m of the capacity C: and the inductance La. The shunt or cross element C! Li connected across the input terminals i of the network is homogeneous or similar to the cross elements L2 C2 contained in the receiver. The entire network is terminated by a resistance R which, for the purpose of insuring optimal transmission properties for the chain structure or network is chosen slightly higher than the surge impedance of the network.

In Fig. 2 there is illustrated a practical embodiment and use of a circuit scheme of the kind shown in Pig. 1. In this figure G denotes the joint line or lead of a television receiving scheme known as a party or communal arrangement whence the various leads Z are brought down to the different receiver apparatus E. For the sake of simplicity, only one such installation has been shown. Now, the input impedance of the receiver E (represented by the dotted line condenser C) forms part of the chain structure or network so that the receiver represents an ohmic resistance. In the circuitscheme shown in Fig. 2 also the capacity of the leads Z (represented by the dotted line condenser C") serves at. the same time as part of the said networx so that one of the cross elements consists solely of an inductance and the leads Z. For the purpose of varying the picture brilliance or amplitude a variable ohmic resistance V. is included in one of the leads Z. the said resistance. if desired, being accommodated directly inside the socket serving to connect the lead Z with the communal or party line G. The resistance W is shunted or bridged by a choke-coil D or else by a. band-pass filler for the tonal frequencies (A. 5'.) which are directly transmitted through the line G, so that In choosing the dimensions for the network K in Fig. 2, values may under certain circumstances be required for the various elements of the structure which are with dimculty realizable by conventional or practical means. For example. if it is discovered that the inductance of the line elements is very high, while the capacity must become very small, this will practically be irrcalizabie, for the reason that the coil that is required would involve such a high self-capaciance that its capacitive reutance becomes less elements C: and L; may consist of standard commcrcial condensers and inductance coils. As to the rest. Fig. 3 corresponds to Hg. 1.

It will be understood that the invention is not restricted to the partzcular form of network here illustrated, in fact, it may be carried out in practice by the use of any desired system of chain structure or recurrent network. For instance, another exemplified embodiment shall be described by reference to Fig. 4. Receiver E is again represented as having a capacity C: at its input impedmce. By the use, for instance, of two series or line coils LI and L2 and of the receiver capacitance C: constituting the shunt or cross element, it is then possible to design a network whose surge impedance is equal to the surge impedance of the communal or party line G. It is then feasible to include the network comprising the receiver directly in series with the communal line, without the line incidentally being affected in any way and without the other receivers being troubled. As a matter of fact, the receiver simply acts like an additional line portion by which the communal line is extended in length, without its electrical properties being altered incident-ally. The inductances LI and L2 are preferably built fixedly into the communal line, whereas the receiver together with its lead-in is capable of being disconnected. In order that no disturbing actions may be occasioned upon disconnection and connection, it is preferable to cut in a substitute (ballast) capacitance conjointly with the disconnection of the receiver, so that, after removal of the receiver, the network comprising Ll, L2 and C: may stay unvaried. The said substitute or ballast condenser may be located directly in the socket and the same may be so disposed that it Is cut out of circuit when the receiver lead is plugged in. In an arrangement of circuits as shown in P g. 4, the chain structure or network need not be terminated by any additional ohmic resistance seeing that its terminating resistance is formed by the onward-extending communal line G. As a matter of fact, it is solely at the last branch-oil point at the end of the communal llne G where a resistance R. equal to the surge impedance of the line must be provided as a. termination.

What I claim is: r

1. A system for the distribution of radio frequency signals including television, comprising a main transmission line and r. rlurality of branch lines, the latter each 11.71118 connected thereto at least one receiver of such signals, characterized in that the input impedance of each receiver constitutes an element of a filter network included in the branch line. said network having such 5 values of inductance and capacity as to constitute an ohmic resistance which is substantially constant over the received frequency range or band.

2. A system for the distribution of radio frequency signals including television, comprising a main transmission line and a plurality of branch lines. the latter each having connected thereto a receiver of such signals, characterized in that the input impedance of each receiver constitutes an element of a filter network which comprises a series tuned circuit and a pair of parallel tuned circuits, said network having such values of inductance and capacity as to constitute an ohmic resistance which is substantially :onstant over the received frequency range or band.

3. A system for the distribution of radio frequency signals including television, comprising a main transmission line and a plurality of branch lines, the latter each having connected thereto a receiver of such signals, a filter network included in each branch line and coupled to its respective receiver, said network comprising a pair of parallel tuned circuits constituting the shunt sections of the filter network and a series tuned circuit connected between the parallel $0 tuned circuits and constituting the line section of said network, said network having such values of inductance and capacity as to constitute an ohmic resistance which is substantially constant over the received frequency range or band, the

capacity element of one of the parallel tuned circuits being constituted by the input impedance of the receiver and the capacity element of the other parallel tuned circuit being constituted by the capacitance of the branch line.

4. A system as defined in claim 3, wherein a variable resistance is serially connected in the branch line for regulating the amplitude of the signals fed to the receiver.

5. A system for the distribution of radio fre quency signals including television, comprising a main transmission line and a plurality of branch lines, the latter each having connected thereto a receiver of such signals characterized in that the input impedance of each receiver constitutes an element of a filter network included in the branch line, said network comprising a pair of parallel tuned circuits and a serles'tuned circuit transformer coupled to said parallel tuned circuits and having such values 0! inductance and 56 capacity as to constitute an ohmic resistance which is independent of frequency within the received frequency range or band.

6. A system for the distribution of radio frequency signals including television, comprising a 00 main transmission line and a plurality of branch lines, the latter having connected thereto a plurality of receivers, characterized in that the input impedance of each receiver constitutes an element of a filter network comprising a series section end a pair of shunt sections. said network having such values of inductance and capacity as to constitute an ohmic resistance which is substantially constant over the received frequency range or band, and further characterized in that to the input impedance of the receiver comprises a capacity, an inductance shunting said capacity and forming a'tuned circuit which constitutes one of the shunt sections. said filter network being terminated at the end to w tab the receiver is 1| spasms 3 piurality of receivezs, characterized in that the input impedance of each receiver constitutes an element of a'filter net'a'crk comprising a series section and a pair of sins: SECJOBS, said network having such values of inductance and capacity as to constitute an ohmic resistance which is substantially constant over the received frequency' range or band, and iurther characterized in that the input impedance of the receivercompriscs a capacity and the leads of the branch line aiso constitute a capacity, an inductance forming with each of said capacities a pair of tuned circuits which constitute the shunt sections. said filter network being terminated at the end to which the receiver is connected by an ohmic resistance which is equal approximately to the characteristic surge impedance of the network.

we o'rro aooscns'nam.