FR2503957A1 - Lumped-constant delay line for TV decoder - has all windows mounted on same support also bearing capacitors and formed from single length of wire - Google Patents

Abstract

The device is formed by coils (3) and capacitors (4), and the coils (3), are wound on a single support (1,2). The coils are all formed by a continuous single wire (7). The capacitors (4) are also mounted on this support (1,2). The wire (7) is connected to a capacitor (4) at the point between two coils (3), without being cut. The device uses conventional components, is not cumbersome, is simple to manufacture and is adjustable with a high accuracy. If the capacitors (4) are of the type having wire outputs, they are placed inside the support (1,2), which is hollow, and they are connected to the coils (3) through holes made in the support wall. In one version, the support (1,2) includes a printed circuit board (2) on which the capacitors (4) are mounted.

Description

"DELAYED LINE WITH LOCALIZED CONSTANTS"
The invention relates to a delay line with localized constants, consisting of windings and capacitors.

 Such delay lines find application in the electronics industry. A delay line according to the invention is in particular intended to be used in a television decoding system.

 Usually delay lines with inductances and capacitors are divided into two classes: those whose capacitors are added physical components, and those in which the capacitors are constituted by the capacitance between the winding wire and a surface connected for example to ground. . These have given rise to an abundant literature. They make it possible to obtain low manufacturing costs, but require very long and costly studies. On the other hand the lines with reported capacitors which we call "localized constants" are easier to calculate and to develop, and of this fact one obtains more easily excellent performances.

 It appears from the above considerations that the quantity of parts to be manufactured and the specifications of the line will be the two essential factors in the choice between the two classes.

 It goes without saying that for high-performance lines whose desired quantities are not very large, the lines with added capacities are essential.

 A common production technique consists in winding each coil individually, then connecting each of these coils to each capacitor by means of an appropriate structure of supports and connections. Such a technique is known for example from French patent No. 2,454,222 which describes an inductive delay line and its manufacturing process. This technique requires the handling of the ends of the cut wires of each coil, for its connection to each capacitor, which is particularly delicate.

 The object of the invention is to provide a delay line with attached capacitors, the manufacture of which is particularly simple, which takes up little space, which uses conventional and inexpensive components, and which is adjustable with great precision.

 The invention is based on the idea that by bringing the capacitors directly onto the winding core of the wire from the coils and by connecting the wire to a capacitor each time from one coil to the other, without cutting it, we avoids handling of flying wires at the end of each coil.

 A delay line according to the invention is thus notably remarkable in that the windings being all wound on the same support, they all consist of the same uninterrupted wire and in that the capacitors are also fixed on said support.

 This arrangement has the advantage of being cheaper because it avoids the numerous delicate operations necessary in the prior art for connecting wires.

free at the end of each winding.

 In the case where the capacitors used are of the type with wire outputs, a delay line according to the invention is also remarkable in that, said support being hollow, the capacitors are situated inside this support and are connected to the winding wire through holes in the thickness of the support.

 This arrangement offers the advantage of being less bulky and of freeing the external surface of the support, which facilitates winding.

Advantageously, the support is constituted by the assembly of two parts in the longitudinal direction.
This allows the capacitors to be mounted in advance on one of the two parts, which facilitates their introduction inside the support.

 In one particular embodiment, one of the two parts is constituted by a flat element made of insulating material, of the type generally called "printed circuit, which carries at least one metallized connection track and metallized areas for connecting the capacitors and windings.

 This arrangement makes it possible to produce the support and connection structure of the capacitors using inexpensive and perfectly developed technologies.

 To obtain precisely adjusted delays, the support is advantageously provided with at least one additional metallized track to short-circuit a portion of the delay line on demand.

 The short circuit is produced ~ according to the basic idea of the invention, using the fact that a metallized area is placed precisely where it is needed under the uninterrupted self-sealing wire which can be connected to it, or not, depending on the value of desired delay.

 Finally, generally, some windings have distinct inductance values, for example at the ends of the line. Furthermore, in a particular embodiment, the coils rest in recesses in the support.

 Then it is advantageous that, the number of turns wound in each housing being constant, the housings have recesses of distinct depths.

 This has the advantage that separate inductance values will be obtained with the same number of turns per winding, which simplifies said winding.

 FIG. 1 represents a perspective view of a portion of the delay line according to the invention.

 FIG. 2 represents a perspective view of one of the longitudinal parts, supporting capacitors.

 Figure 3 shows a sectional view of a delay line according to the invention.

 FIG. 4 represents the electrical diagram of an end of the delay line.

 FIG. 5 represents, in plan view, one end of a printed circuit constituting one of the two longitudinal parts of the winding support.

 Figure 6 shows in elevation one end of the other longitudinal part.

 FIG. 1 shows a portion of a delay line with localized constants, consisting of windings 3 and capacitors 4. Each elementary cell consists of two windings and a capacitor.

 The general support consists of the assembly of two parts 1,2 in the longitudinal direction.

 The coils 3 are all wound on the same support 1,2 and they all consist of the same uninterrupted wire which passes from one coil to the other directly, as shown for example by the strand referenced 7. In addition capacitors 4 are fixed on said support, more precisely on part 2 of the support.

 The capacitors, which are of the wire output type, are located inside the support 1,2 and are connected to the wire 7 of the windings through holes made in the thickness of the support, more precisely from part 2 of the support. Of course part 1 of the support has a recess behind part 2 so that the capacitors find their place there. Therefore the entire support 1,2 is hollow.

 As shown in Figure 2, part 2 is constituted by a flat element of insulating material, of the type generally called "printed circuit". It carries at least one metallized track 5 which is a so-called "common" connection, for all the capacitors. It also carries metallized pads 8.9, interconnected, for the connection of the capacitors and the windings. A capacitor is connected to track 8 passing through the printed circuit, and wire 7 is connected to track 9, therefore to the capacitor.

The operations necessary for producing such a delay line are as follows 1 / Manufacturing of part 1, for example by molding in
a plastic material.

2 / Manufacture of printed circuit 2, single-sided, by a
well known conventional process.

3 / Mounting and soldering of the capacitors 4 on the circuit 2.

4 / Assembly of the two parts 1 and 2.

5 / Winding of all inductors 3 using a wire
uninterrupted 7.

6 / Welding of the strands 7 on the corresponding pads 9.

 Figure 3 shows in section the parts 1 and 2 assembled. The assembly of parts 1 and 2 is facilitated because part 1 is provided with an imprint 19 in which part 2 is placed. Part 2 is secured in this imprint by lugs 22 carried by part 1 and which come to fit part 2. This process colloquially called "clipping" is well known. These pins 22 are quite small and few in number so as not to interfere with the winding.

 FIG. 1 shows a strand 7 of the wire which is welded on passage, by means of a tin-lead solder, over the metallized area 9. In order to facilitate this operation, self-sealing enameled wire is used, that is to say -to say whose enamel volatilizes during a tin soldering operation.

The use of such a wire is particularly indicated here, because the strand 7 stretched above the plate 2 would be very difficult to strip in the case of a non-self-sealing wire.

 A variant of such a delay line can be constructed by means of capacitors without connection wires, of the so-called "chip" type in English. In this case, you can place the capacitors, which are very small, between each winding and outside the support or anywhere, inside, the connection to the winding wire being obtained via metallized holes in the circuit. printed 2.

 Figure 4 shows part of the electrical diagram of such a delay line. The elements located on the left in the figure are elements for adapting the end of the line. The inductance of element 3A is different from that of elements 3B, 3C, 3D, itself different from that of elements 3E, 3F and following. Similarly, the capacitor 4A has a different value from that of the capacitor 4B and the following ones. An elementary cell comprising two coils and a capacitor is indicated by the dotted frame. (The values allowing to constitute all these elements will be indicated below). These are critical coupling cells. The couplings indicated by the arrows 18 are correctly obtained with regular spacing of the coils 3 between them.

 In order to be able to precisely adjust the line at the end of manufacturing, an additional metallization, referenced 13 -13 in FIG. 5, makes it possible to short-circuit and eliminate on request a basic cell of the delay line. This device can be repeated at the level of a plurality of cells, each of which causes a different delay, calculated according to the well-known principle known as the “weight box”, so that by selecting the short-circuited cells it is possible to adjust with great precision the whole line. Each of the points 5,9,10,11, 14 is found. on the two figures 4 and 5, thus making it possible to understand clearly how the electrical diagram of figure 4 is produced by means of the printed circuit of figure 5. The areas 11,10,14,9 blackened on figure 5 correspond to points where the wire is welded during the operation referenced 6 in the description of operations made above. On the other hand, the pad 8 is connected during operation 3 to a capacitor, but is not connected to the wire, which passes over it while remaining isolated.

If the wire is soldered at 13-13 to short-circuit a cell, it must also be soldered at 21 and cut between 13 and 21, to eliminate the cell.

 FIG. 6 shows that part 1 of the support is provided with recessed housings, for example 12, 16 and 6. In these housings, the section of which is of semi-circular shape, and which are also shown with the reference 6, on Figure 1, rest the windings. A plurality of cells, each of which causes a different delay, or else the adaptation half-cells at the end of the line, require windings having a plurality of different inductance values. To obtain this, the number of turns wound in each housing being constant, the housings have recesses of distinct depths. For example, the housings 16 are deeper than the housing 12, which results in a lower self-inductance value. These housings 12 and 16 are also visible in dotted lines in the section of FIG. 3.

 The references 20 and 15 in FIG. 5 indicate output pins soldered to circuit 2 and which are housed in the grooves 17 of part 1 represented by FIG. 6.

The main characteristics of production and performance of a line, cited only by way of example, are as follows - Spacing between the windings: 3.81 mm - Radius of the semi-circular bottom
of the 12 or 6 housings 4,875 mm - Radius of the semi-circular bottom of the housing 16: 3.85 mm - Number of turns of each coil: 10, in enamelled wire
10/100 - Capacity value: 4A: 56 pF, 4B: 110 pF
4C and following: 220 pF
The complete delay line includes thirty two cells.

Among them, thirty are identical, and two (one of them for example, consists of the elements 3C, 3D, 4B) cause a half-delay, thanks to half values for the inductances and the capacitance. Each of these latter cells therefore represents a delay of 0.5. 32 or 1.56% of the total delay, which allows the delay to be adjusted to + 0.8%.

The printed circuit is arranged so that one can short-circuit up to two normal cells and two "half" cells on demand, which makes it possible to make up for dispersions in a range of 10%. The first two induetances 3A and 3B have respectively a normal value and a half value, to adapt the impedance at the end of the line.

The overall performance of the complete line is as follows
Characteristic impedance: 120 n
Delay: adjustable from 900 to 940 nS Bandwidth: O to 6 MHz, 3 dB
Delay adjustment accuracy: - 0.8%
Variation in delay in bandwidth: t 1%
This last particularly remarkable result is obtained thanks to the very precise development that one can obtain, since by modifying the value of a parameter, for example the physical dimension or the number of turns of the inductances, one does not modify unintentionally all other parameters.

 In addition, this result is obtained with simple manufacturing equipment and an inexpensive construction method.

Claims (6)

- CLAIMS  1.- Delay line with localized constants, consisting of windings and capacitors, characterized in that the windings (3) being wound on the same support (1,2), they all consist of the same wire (7) uninterrupted and in that the capacitors are also fixed on said support (2).  2. Delay line according to claim 1, the capacitors of which are of the type with wire outputs, characterized in that, said support being hollow, the capacitors are located inside this support and are connected to the wire (7 ) windings through holes made in the thickness of the support (2).  3. Delay line according to any one of claims 1 or 2, characterized in that the support is constituted by the assembly of two parts (1,2) in the longitudinal direction.  4. Delay line according to claim 3, characterized in that one of the two parts is constituted by a flat element (2) of insulating material, of the type generally called "printed circuit", which carries at least one metallized track connection (5) and metallized areas (8,9) for the connection of capacitors and windings.  5. Delay line according to claim 4, characterized in that the support is provided with at least one additional metallized track (13) for short-circuiting on demand a portion of the delay line.  6. Delay line according to any one of claims 1 to 5, the coils of which rest in recesses (6), and have a plurality of distinct inductance values, characterized in that, the number of turns being wound in each housing being constant, the housings (6,16) have hollows of distinct depths.