US3798574A

US3798574A - Directional coupler having directly connected taps

Info

Publication number: US3798574A
Application number: US00278025A
Authority: US
Inventors: L Workman
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-08-04
Filing date: 1972-08-04
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19

Abstract

There has been provided an improved directional coupler adapted to be utilized with an electrical distribution line. In a first embodiment a section of coaxial conductor is utilized generally with its center conductor in series with distribution line and its outer conductor as the tap at one end and its other end of outer conductor coupled to ground through a matching resistor. In a second embodiment printed circuit boards are utilized with relatively short parallel conductors with an insulator therebetween. The conductors are coupled in the distribution line in a manner similar to that of the coaxial embodiment. Thirdly a combination of a flat response coupler is connected with either of the above couplers, which have a tilted response, yielding a configuration having tailorable output of controlled gradient.

Description

United States Patent [1 Workman [451 Mar. 19, 1974 DIRECTIONAL COUPLER HAVING DIRECTLY CONNECTED TAPS [76] Inventor: Lester J. Workman, P.O. Box 5547,

Sarasota, Fla. 33579 [22] Filed: Aug. 4, 1972 [21] Appl. No.: 278,025

Related US. Application Data [63] Continuation-impart of Ser; No. 112,297, Feb. 3,

1971, abandoned.

Primary ExaminerPaul L. Gensler Attorney, Agent, or Firm-Cushman, Darby & Cushman [57] ABSTRACT There has been provided an improved directional coupler adapted to be utilized with an electrical distribution line. In a first embodiment a section of coaxial conductor is utilized generally with its center conductor in series with distribution line and its outer conductor as the tap at one end and its other end of outer conductor coupled to ground through a matching resistor.

in a second embodiment printed circuit boards are utilized with relatively short parallel conductors with an insulator therebetween. The conductors are coupled in the distribution line in a manner similar to that of the coaxial embodiment.

Thirdly a combination of a flat response coupler is connected with either of the above couplers, which have a tilted response, yielding a configuration having tailorable output of controlled gradient.

H 6 Figures Z1 Fl/ l/l/l/l/l/l/ml 5 kno DIRECTIONAL COUPLER HAVING DIRECTLY CONNECTED TAPS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 112,297, filed Feb. 3, 1971 now abandoned.

BACKGROUND OF THE INVENTION As is well known, television signals can be transmitted through air at very high frequencies (VHF) and ultra-high frequencies (UHF); however, it is difficult to transmit such high frequency signals through cables because there is an energy loss per unit length of cable. There are businesses which specialize in providing community antennas to pick up signals transmitted through the air and, then, to transmit the signals over the company cable to homes. Generally the effort is to collect a good signal and to transmit it without distortion to the particular homes along the cable distribution line. Because of the energy loss at high frequencies per unit of length travelled, step-up amplifiers may be used at selected stations along the cable, the amplifiers being in series with one another along the line with intermediate signal'take-off stations for home service, each of which utilizes some of the energy so that there is a consequent reduction of available signal energy at the progressive signal take-off stations along the distribution line. It is important to take a portion or component of the signal current from the distribution line at the signal take-off stations with a minimum of interference to the main signal current. It is also important that any noise travelling in the reverse direction on the distribution line not be coupled to the users. In other words, reflected noise which is always present to some extent, should not be transmitted to the other taps. A directional coupler is employed to do this.

In the past, couplers have been of the type which includes transformers, capacitors and resistors in proper arrangement or the conventional strip line type which is used with or without filters; however, these have inherent limitations as is appreciated in the art.

More specifically in the past, one method that has been used for manufacturing such directional couplers employed the use of strip lines whose electrical length was, in general, designed to be at least one quarter wavelength of the lowest frequency. To change the quantity of of coupling, the thickness of the dielectric between the parallel strip lines was changed; The manufacture of these couplers suffers from the following problems: Imperfections in the registration of the parallel lines degrading the directioning and causing variations in the desired amount of coupling, and edge ef fects becoming a function of the separation of the strip line. If any attempt is made to wind the line to obtain volumetric efficiency, the lines frequency cutoff becomes less. Another method which has been used employs lumped linear networks and transformers. The major difficulty in the past with these has been the cost of manufacture; the parts must all be separately assembled and redesigned for each quantity of coupling. As mentioned previously, there are also hybrid versions that use strip line and networks in combination.

In addition to the objects which will be apparent from the foregoing and the description to follow, this invention has as an object an improved directional coupler for the signal take-off stations which is capable of tapping off part of the signal current in one direction only, so that it cannot go back into the main line which would otherwise cause trouble by interfering with the main signal being transmitted along the cable. More specifically, there often occurs in practice the problem of transmitting radio frequency (RF) power to several user terminals. To accomplish this, directional couplers are employed to couple energy from a main transmission line to the user. The adjective directional is used to describe a device which will attenuate any energy that is sent back toward the main transmission line which causes deleterious reflection. This reflection could be caused by mistermination or of poor isolation from other electronic circuitry. The directional coupler has, therefore, as an object the prevention of this noise from continuing down the distribution line and disturbing'other users.

SUMMARY OF THE INVENTION There have been provided improved directional couplers adapted to be used with an electrical distribution line. The improvement comprises, in a first embodiment a length of insulated coaxial cable including, as seen in cross-section, a central electrical conductor of a first length and a conductor sleeve shielding, axially surrounded in spaced relation with the central conductor. The shielding is of an axial length less than that of the central conductor, and first and second means are respectively adapted for connection with opposite ends of the central conductor and the shielding for coupling to the distribution'line and a resistor having one end coupled to groundis adapted to be selectively coupled to one or the other of said first and second means in accordance with which of said means is to be grounded.

In a second embodiment the coupler comprises, a first conductor of a given length between its ends adapted to be coupled to the distribution line, and a second electrical conductor of a selected length adapted at one end to be a tap and its other end coupled through a resistor to ground. Each conductor being secured as a portion of printed circuit board and separated by a selected thickness of insulator.

In a third embodiment either of the couplers recited above is coupled with a fiat response coupler, the former couplers exhibiting a tilted response increasing with frequency whereby the configuration of a flat and tilt coupler provides for tailoring of the output signal ultimately tapped.

For a better understanding of the present invention, together with other and further objects thereof, reference is directed to the following description, taken in connection with the accompanying drawings, while its scope will be pointed out in the appended claims.

DESCRIPTION OF THE DRAWINGS FIG. 1 of the drawings is a view in cross-section of one embodiment of a coupler constructed in accordance with this invention.

FIG. 2 is a drawing illustrative of another embodiment of a coupler constructed according to the principles recited below.

FIG. 3 is a graphic illustration of signal response characteristics considered in the development of the present invention.

FIG. 4 is a circuit combining couplers having different response characteristics.

FIG. 5 is a graphic illustration of the response characteristics of the circuit of FIG. 4.

FIG. 6 is an illustration of a coupler having a flat response characteristic.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides improved directional couplers to be implemented with ordinary cable signal transmission lines, providing the advantages of large coupling per unit length which gives volume efficiency. It also provides an advantage of low cost as will be seen, by reason of their construction and adaptability for connection in a distribution line. A further advantage is that they are of uniform predictable construction, with the amount of coupling being uniform and easily controlled. It results in increased directivity and better VSWR (Voltage Standing Wave Ratio); and, most of all, wider bandwidth is also available. A single small unit of the type of this invention works very well from the lower VI-IF signal range to the higher UHF signal range. As regards this latter advantage, a single unit having this bandwidth can be simply designed to have any preassigned quantity of coupling. The volume occupied by such a coupler can be less than 1 cubic inch.

In the drawings, the basic coupler is generally designated by the numeral 12. It includes a length of coaxial cable which may be insulated as at 22 and in which a center conductor 11 is used for a through-put line and an outer conductor 13 is used for a tap, there being conventional dielectric material 15 separating these conductors. In the use of the directional coupler now to be described, the roles of the outer conductor 13; and the inner conductor 11 can be reversed. In use, energy is coupled in the tap, both by electromagnetic and electrostatic means, that is, both inductive and capacitive coupling. These reinforce each other in the correct direction of coupling from the tap 14 to the input 20, or from the input to the tap; however, the electrostatic coupling serves to cancel the effect of the electromagnetic coupling for coupling from the output to the tap, or from the tap to the output. This produces the desired directivity. The lines are terminated in the characteristic impedances z To increase the amount of coupling, a longer line is used. In general, the line need not be precisely one quarter wavelength long. If the line is shorter than one quarter wavelength, a rising frequency dependence of coupling is effected. This generally helps compensate for a falling frequency dependence of the main transmission line. If, however, this is undesirable, a lumped transmission filter can be used and designed by those skilled in the art. The characteristics of the filter are that its driving point impedance be real and equal to the characteristic impedance of the line, and that its transfer function shape the desired frequency response. The distribution line, not shown, transmits the signal to the input zone of the directional coupler 12 which taps a portion of the signal current through the tap with the main signal component leaving the output zone as at 16.

In a preferred embodiment, the coupler 12 is provided with means 18 adapting the connection of it in a distribution line, which, as shown, comprise the extending

portions

18 and 28 of the center conductor 11, which may be connected to the distribution line by conventional conductor means. Also, means are provided to adapt one end of the shielding or outer conductor 13 to an electrical tap lead 30 and, at the other end, as at 32, to connect the shielding through an electrical lead 34 in series with a suitable resistor 24 to ground 26, the means illustrated being soldered connections of the leads to the ends of the shielding with the insulation material being shortened axially to accommodate the same.

The coaxial cable used may also be either rigid or flexible wherein the outer conductor 13 is respectively either a pipe or braided shield. If constructed in the rigid configuration it is preferably manufactured from a quality brass material forming a rigid cylindrical pipe for optimum results.

If on the other hand the non-rigid coupler is used longer lengths may be configured in a small enclosure,

and the coupler could be looped without appreciable losses. In the preferred style the loops should be avoided unless the current direction is kept uniform relative to adjacent conductors.

In FIG. 2 a second embodiment has been developed which illustrates another adaptation for the principles recited herein.

The coupler illustrated generally at is adapted to be coupled to a distribution line at

terminals

16 and 20 which are coupled to a conductor 41 by leads 48. The conductor 41 is separated by a dielectric material 42 from a second conductor 43. The conductor 43 is coupled to tap wire lead 44 at one end and at its other end to lead 45 coupled to resistor 24 and ground 26 similarly as in FIG. 1.

The system as illustrated in FIG. 2 utilizes printed circuit boards or the like 46 and 47 for respectively mounting upper and

lower conductors

41 and 43. In addition the length of the conductor regulates the amount of coupling as well as the thickness of the dielectric 42.

In the past, as previously mentioned, it was necessary to utilize a coupler having a length equal to a quarter wavelength of some optimum center frequency; however, neither of the systems of FIG. 1 nor 2 require such a specification to be operable. In fact, it has been found that this requirement is not material any longer.

There have been described methods of coupling similar to the system of FIG. 2 insofar as the printed circuit board and a dielectric has been used. Those systems utilize a serpentine pattern on one board and a mirror image on the opposite one. The system has the drawback that it causes interference within itself when adjacent portions of the conductive pattern are of opposite polarity in the sense of carrying current, which attentuates the coupling.

This maze" like pattern or serpentine pattern referred to was utilized because it was thought that a quarter-wavelength was necessary for proper coupling and lengths required under that theory were upwards of 12 inches or more. The reversals of pattern at high frequency destroys their efficiency. However, it was discovered that in a preferred embodiment only a relatively short section of printed circuit conductors having a configuration as in FIG. 2 were required. In fact, one such coupler is only one half to three quarters of an inch long.

It has been found that the output signal of the coupling devices described herein provides a linear output generally having a greater output at higher than at lower frequencies.

Further experimental research has revealed that by utilizing the couplingdevice illustrated herein, roll-off of the signal does not occur at high frequencies. As a matter of fact, the output is linear from low to high frequencies, e.g., from Channel 2 through at least Channel 13. This linearity was not possible with prior devices because in order to obtain a reasonable output at high frequencies, i.e., greater than Channel 8, it was necessary to design a coupler which would have a response similar to that shown in Curve H of FIG. 3, which is a diagram showing relative response requirements at various channels (i.e., frequencies).

Curve A shows a response curve which has been generally effective in rendering reasonable reception. Curve B shows what would be closer to ideal, i.e., a linear response which response is delivered as a result of the invention herein. It is possible with the apparatus of the present invention to linearize Curve A to approximate a straight line as B and therefore obtain a response for a band of frequencies compatible with available channels.

While the curves of FIG. 3 are not intended to show absolute values, they do illustrate in an approximate form an object of the invention (i.e., more linear signal coupling) and are intended to help clarify the shortcomings of prior devices and the advantages of the present apparatus.

Further, it should be mentioned that by experimentation it has been found that the length of the outer conductor governs the height of the line B shown again in FIG. 3, wherein dotted lines C and D represent respectively higher and lower attenuations of signal response with respective increases and decreases in outer conductor 13 length as the frequency increases. This may be useful in optimizing the response for different locations and the idiosyncracies of particular receivers.

Referring to FIG. 4 there is shown a circuit for utilizing either of the couplers of FIG. 1 or 2, and a flat response coupler to be described further in the specification. This circuit of FIG. 4 includes a distribution line adapted to be coupled to the circuit herein as in FIG. 1 at

points

16 and 20. A choke 50 is coupled across the input to the output to carry a low frequency component of the transmission signal, and block high frequency components. Capacitors 51 and 52 are utilized to isolate low frequency signals and couple the high frequency component into the coupling section of the circuit of FIG. 4.

Coupler 55A is the type referred to above in FIGS. 1 or 2 and has a response characteristic illustrated in H6. 3. Coupler 55B is a known type coupler which has a flat response characteristic across a wide range of frequencies, such characteristic is illustrated in FIG. 5 curve E. Coupler 55A is disposed so as to be serially coupled at its input and with the flat coupler 55B, and through capacitors 51 and 52. The output of flat coupler 55B is connected over a lead 56 to the output portion of coupler 55A thence over lead 57 to a signal splitter 58 and ground 26. The signal splitter 58 is a conventional device for providing multiple taps or multiple connections for a plurality of TV sets and the like. The flat coupler is connected to ground 26 over matching resistor 24.

In referring to FIG. 5 it can be seen that the response characteristic E for the flat coupler is modified as in curves F and G in accordance with the length of the coupler 55A. The selected length utilized yields a response characteristic G shown in FIG. 5. However, if a shorter coupler is used a response F is realized (See also FIG. 3, Curves B, C, and D). The ordinate represents the output voltage of the coupler E in any conventional units beginning from zero output. As previously mentioned the curves G and F are similar to those shown in FIG. 3 for various lengths of the tilted output coupler. When the flat coupler 55B is serially coupled with a tilt coupler 55A the respective outputs F and G shown in FIG. 5 occur. For example, the addition of curve F with curve E yields curve F, since the response of F does not occur over the whole band width from channel 2 through channel 13 and above. The tilt provided to the coupler response F is relatively moderate. However, the response of a coupler as illustrated by curve G would have a greater effect on a flat response E, thereby producing the curve G which has a greater incline.

The combination of a flat and tilt coupler, 55A and 55B respectively, as shown in FIG. 4 permits the designer to tailor the response in accordance with the needs of the particular area. It should be noted that a flat response coupler is not necessarily the best device to use in all situations. The reason for this is that when high frequency signals are communicated over transmission line, the very high frequencies, for example, the frequencies of the channel 13 range as opposed to the channel 2 range are attenuated at a greater rate per unit distance of transmission. For this reason it is necessary to get a better response at high frequency in the coupler than at low because so little high frequency signal is available.

An example of a type of flat response coupler is shown in FIG. 6 and it includes coupling coils C1, C2, C3 and C4. Coupling coil C1 is adapted to be coupled to the distribution line at 16 and 20 as in the other figures herein. In this embodiment coils Cl and C2 have a turns ratio of l to n for n greater than 1, with coil C2 having one end coupled to ground and a second end coupled to coil C4 in a center tap fashion. Coil Cl is also coupled via a center tap to one end of coil C3, which has its other end coupled to ground 26. Coil C4 is coupled at one end to the tap 59 and to the other end to matching resistor 24 and ground 26. Coils C3 and C4 have turns ratio of n to l with n greater than 1.

The circuit herein provides for isolation of the input and the output and in addition provides for a broad flat response from any of a number of frequencies between the channel 13 range at least.

In the example of FIG. 6 the input signal from the transmission line is inductively coupled across the C1, C2 coils in a ratio of 1:2 thereby stepping up the signal in one respect. Part of the signal to Cl is also coupled with coil C3 and provides an output to coil C4. Furthermore, the output of coil C2 is coupled in the center top fashion to the output coil C4 thereby reinforcing the signal provided by coil C3. The coils are wound in such a fashion so as to promote reinforcement of the input signal from the transmission line and to block the re- .verse currents tending to be provided by the tap 59 from any receiver device.

The various combinations of the circuits used in this description provide a system which has a response characteristic which is tailorable in accordance with the selected needs, an example of which would be the varying output characteristics of a cable TV channel, said variations occurring in accordance with the position of the tap relative to some amplification station. The system exhibits a linear response with effectively no roll off at high frequencies and may be set up so as to be responsive to relatively low frequency, for example, megahertz, as well as the higher frequencies of channel 2, for example, which is approximately 54 megahertz and channel 13 which is around 216 megahertz.

Also, multiple taps have been created by modifying multiple conductors in a shielded cable. The shield becomes the main transmission line and each inner conductor becomes a tap. Another method of making multiple taps, using a cable with multiple conductors, is to modify it so that one of the conductors is a main transmission line and all the remaining conductors become that many taps.

Incidentally, referring to the drawing, it is also possible to modify the coaxial cable, so that the shield becomes the main transmission line, and the center conductor becomes the tap.

In place of ordinary coaxial cable, certain lamp cords can be modified for use as a directional coupler. In fact, any twin pair of electrical conductors giving a reasonable amount of electromagnetic and electrostatic coupling, can be modified for use as a directional coupler.

What is claimed is:

1. In combination with an electrical distribution line, an improved directional coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises:

a first electrical conductor of given length between its opposite ends,

an outer electrical conductor in the form of a sleeve circumferentially disposed in spaced relation about said first conductor to form a high frequency coaxial line,

said outer conductor having between its opposite ends an axial length less than said given length of said first conductor,

said outer conductor being lengthwise disposed about said first conductor so as to expose the said opposite ends of said first conductor for connection purposes,

one of said conductors being in series with said distribution line by direct connection thereto of its said opposite ends,

terminating resistor means directly connected externally to one of said opposite ends of said other conductor, and

a tap directly connected only externally to the other of said opposite ends of said other conductor for directly tapping off said high frequency signal.

2. The combination in claim 1 wherein said coaxial line comprises a length of insulated coaxial cable including said first and outer conductors.

3. The combination in claim 1 wherein a bed of dielectric material is provided intermediate said first and outer conductors.

4. The combination in claim 1 wherein said outer conductor is a rigid cylindrical pipe conductor.

5. The combination in claim 1 wherein said coaxial line provides a sustantially linear response characteristic between an input signal available from said transmission line and an output at said tap.

6. The combination in claim 1 wherein said one conductor that is series connected with said distribution line is said first conductor, said tap and terminating resistor means being connected to the said opposite ends of said outer conductor.

7. The improved directional coupler as in claim 1 wherein said outer conductor is rigid.

8. The improved directional coupler as in claim 7 wherein said outer conductor is made of brass.

9. In combination with an electrical distribution line, an improved directional coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises:

a first printed electrical conductor of given straight length between its opposite ends,

a second printed electrical conductor in a parallel spaced coupled relation with said first conductor to form a high frequency line and having between its opposite ends a desired straight length relative to said given length of said first conductor,

the first of said conductors being series with said distribution line by connection thereto of its said opposite ends,

terminating resistor means directly connected externally to one of said opposite ends of said second conductor, and

a tap directly connected to the other second conductor end for directly tapping off said high frequency signal.

10. The combination as in claim 9 wherein both of said conductors comprise segments of printed circuit board including strips of conductive material in parallel plate configurations.

11. The combination as in claim 9 wherein a dielectric material separates each conductor from the other.

12. An improved directional coupler for effectively tapping off a high frequency signal from an electrical distribution line, wherein the improvement comprises:

a first directional coupler having a flat response characteristic over a broad range of transmitted frequencies including;

an input transformer having its primary coil center tapped and a secondary coil coupled to ground at one end, and

an output transformer having its secondary coil center tapped with the other end of said input transformer secondary, and further coupled to an output tap lead at one end and to ground through a matching resistor at its other end, and the primary coil of said output transformer coupled at one end to ground and at its other end to the center tap of said primary of said input transformer; and

a second coupler having a primary response characteristic increasing with frequency including a length of cable having as seen in cross section a central electrical conductor of a first length; a rigid conductive shielding circumferentiallydisposed in spaced relation about the central conductor said shielding being of an axial length less than that of the central conductor, said central conductor being coupled serially between an input of said fiat coupler and the distribution line, and said shielding being coupled at one end to the output tap of said flat coupler, and an output tap of said improved directional coupler leading from an opposite end of said rigid shielding.

13. The improved directional coupler of claim 12 wherein said input and output transformers have complimentary turn ratios and are each wound so as to reinforce the output of said output transformer and isolate the input transformer from the distribution line from reflected signals.

14. An improved directional coupler adapted to use with an electrical distribution line wherein the improvement comprises:

a first directional coupler having a flat response characteristic over a broad range of transmitted frequencies including:

an input transformer having its primary coil center tapped, and a secondary coil coupled to ground at one end and;

an output transformer having its secondary coil center tapped with the other end of said input transformer secondary, and further coupled to an output tap lead at one end and to ground through a matching resistor at its other end, and the primary coil of said output transformer coupled at one end to ground and at its other end to the center tap of said input primary coil; and

a second coupler having a primary response characteristic increasing with frequency including a first electrical conductor of a given length between its opposite ends, a second electrical conductor in parallel space relation with said first conductor, said second conductor having between its opposite ends an axial length less than its given length of said first conductor, one end of said second conductor forming an output tap and its other end adapted to be coupled to the output tap of said first flat response coupler, and serially coupled over its first electrical conductor with said flat response coupler and-said distribution line.

15. In combination with an electrical distribution line an improved directional coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises:

a first electrical conductor of given length between its opposite ends,

one of said conductors being in series with said distribution line by connection thereto of its said opposite ends,

a tap directly connected only externally to the other of said opposite ends of said other conductor for directly tapping off said high frequency signal,

wherein said directional coupler has a sloping response characteristic that substantially linearly increases with frequency over a broad range of frequencies including from at least about television channel 2 to at least about television channel 13,

said combination further including a second directional coupler having a substantially flat response characteristic over said frequency range,

said second coupler having two input terminals connecting the second coupler in series between said distribution line and one of said opposite ends of said one conductor, terminating resistor means,

said second coupler having two output terminals respectively connected to said terminating means and to the said one opposite end of said other conductor to cause from the said tap of the first mentioned coupler a total response characteristic over said frequency range that is substantially the addition of the said sloping and flat response characteristics, the length of said outer conductor being determinative of the amount of antenuation of the said sloping curve.

16. In combination with an electrical distribution line, an improved directional coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises:

the first of said conductors being in series with said distribution line by connection thereto of its said opposite ends,

a tap connected to the other second conductor end for directly tapping off said high frequency signal,

said directional coupler having a sloping response characteristic that substantially linearly increases with frequency over a broad range of frequencies including from at least about television channel 2 to at least about television channel 13,

said second coupler having two output terminals respectively connected to said terminating means and to the said one opposite end of said other conductor to cause from the said tap of the first mentioned coupler a total response characteristic over said frequency range that is substantially the addition of the said sloping and flat response characteristics, the length of said outer conductor being determinative of the amount of attenuation of the said sloping curve.

Claims

1. In combination with an electrical distribution line, an improved directional coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises: a first electrical conductor of given length between its opposite ends, an outer electrical conductor in the form of a sleeve circumferentially disposed in spaced relation about said first conductor to form a high frequency coaxial line, said outer conductor having between its opposite ends an axial length less than said given length of said first conductor, said outer conductor being lengthwise disposed about said first conductor so as to expose the said opposite ends of said first conductor For connection purposes, one of said conductors being in series with said distribution line by direct connection thereto of its said opposite ends, terminating resistor means directly connected externally to one of said opposite ends of said other conductor, and a tap directly connected only externally to the other of said opposite ends of said other conductor for directly tapping off said high frequency signal.

9. In combination with an electrical distribution line, an improved directional coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises: a first printed electrical conductor of given straight length between its opposite ends, a second printed electrical conductor in a parallel spaced coupled relation with said first conductor to form a high frequency line and having between its opposite ends a desired straight length relative to said given length of said first conductor, the first of said conductors being series with said distribution line by connection thereto of its said opposite ends, terminating resistor means directly connected externally to one of said opposite ends of said second conductor, and a tap directly connected to the other second conductor end for directly tapping off said high frequency signal.

12. An improved directional coupler for effectively tapping off a high frequency signal from an electrical distribution line, wherein the improvement comprises: a first directional coupler having a flat response characteristic over a broad range of transmitted frequencies including; an input transformer having its primary coil center tapped and a secondary coil coupled to ground at one end, and an output transformer having its secondary coil center tapped with the other end of said input transformer secondary, and further coupled to an output tap lead at one end and to ground through a matching resistor at its other end, and the primary coil of said output transformer coupled at one end to ground and at its other end to the center tap of said primary of said input transformer; and a second coupler having a primary response characteristic increasing with frequency including a length of cable having as seen in cross section a central electrical conductor of a first length; a rigid conductive shielding circumferentially disposed in spaced relation about the central conductor said shielding being of an axial length less than that of the central conductor, said central conductor being coupled serially between an input of said flat coupler and the distribution line, and said shielding being coupled at one end to the output taP of said flat coupler, and an output tap of said improved directional coupler leading from an opposite end of said rigid shielding.

14. An improved directional coupler adapted to use with an electrical distribution line wherein the improvement comprises: a first directional coupler having a flat response characteristic over a broad range of transmitted frequencies including: an input transformer having its primary coil center tapped, and a secondary coil coupled to ground at one end and; an output transformer having its secondary coil center tapped with the other end of said input transformer secondary, and further coupled to an output tap lead at one end and to ground through a matching resistor at its other end, and the primary coil of said output transformer coupled at one end to ground and at its other end to the center tap of said input primary coil; and a second coupler having a primary response characteristic increasing with frequency including a first electrical conductor of a given length between its opposite ends, a second electrical conductor in parallel space relation with said first conductor, said second conductor having between its opposite ends an axial length less than its given length of said first conductor, one end of said second conductor forming an output tap and its other end adapted to be coupled to the output tap of said first flat response coupler, and serially coupled over its first electrical conductor with said flat response coupler and said distribution line.

15. In combination with an electrical distribution line an improved directional coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises: a first electrical conductor of given length between its opposite ends, an outer electrical conductor in the form of a sleeve circumferentially disposed in spaced relation about said first conductor to form a high frequency coaxial line, said outer conductor having between its opposite ends an axial length less than said given length of said first conductor, said outer conductor being lengthwise disposed about said first conductor so as to expose the said opposite ends of said first conductor for connection purposes, one of said conductors being in series with said distribution line by connection thereto of its said opposite ends, a tap directly connected only externally to the other of said opposite ends of said other conductor for directly tapping off said high frequency signal, wherein said directional coupler has a sloping response characteristic that substantially linearly increases with frequency over a broad range of frequencies including from at least about television channel 2 to at least about television channel 13, said combination further including a second directional coupler having a substantially flat response characteristic over said frequency range, said second coupler having two input terminals connecting the second coupler in series between said distribution line and one of said opposite ends of said one conductor, terminating resistor means, said second coupler having two output terminals respectively connected to said terminating means and to the said one opposite end of said other conductor to cause from the said tap of the first mentioned coupler a total response characteristic over said frequency range that is substantially the addition of the said sloping and flat response characteristics, the length of said outer conductor being determinative of the amount of antenuation of the said sloping curve.

16. In combination with an electrical distribution line, an improved directionAl coupler for effectively tapping off a high frequency signal from said electrical distribution line, wherein the improvement comprises: a first printed electrical conductor of given straight length between its opposite ends, a second printed electrical conductor in a parallel spaced coupled relation with said first conductor to form a high frequency line and having between its opposite ends a desired straight length relative to said given length of said first conductor, the first of said conductors being in series with said distribution line by connection thereto of its said opposite ends, a tap connected to the other second conductor end for directly tapping off said high frequency signal, said directional coupler having a sloping response characteristic that substantially linearly increases with frequency over a broad range of frequencies including from at least about television channel 2 to at least about television channel 13, said combination further including a second directional coupler having a substantially flat response characteristic over said frequency range, said second coupler having two input terminals connecting the second coupler in series between said distribution line and one of said opposite ends of said one conductor, terminating resistor means, said second coupler having two output terminals respectively connected to said terminating means and to the said one opposite end of said other conductor to cause from the said tap of the first mentioned coupler a total response characteristic over said frequency range that is substantially the addition of the said sloping and flat response characteristics, the length of said outer conductor being determinative of the amount of attenuation of the said sloping curve.