Patent GB-1438470-A (GB)
Title: Delay line device
IPC: H03H7/32
Filed: 1974-04-11
Abstract: 1438470 Delay line assemblies TOKO Inc 11 April 1974 [20 April 1973] 16222/74 Heading H1R [Also in Division H3] A multisection delay line of ladder type comprises (Fig. 1) a first group A of, e.g. 4 coils, each wound on a drum shaped ferrite core and a second group B of, e.g. 4 coils, wound on similar cores arranged equally spaced in rows; the second group being staggered with regard to the first group towards the input which is applied to the first coil of the first group. The turns of the row A coils, are in opposite sense to those of the row B coils to produce positive coupling, therebetween, and the respective coils of row A and those of row B are wound in similar sense inter se to produce negative coupling therebetween. The first coil of the first group A is connected to the first coil of the second group B which is in turn connected to the second coil of the first group. This is connected to the second coil of the second group and so on sequentially, with output derived from the last coil of the second group. The coils are respectively tapped to ground through capacitors C, and the input and output capacitors Ci, Co are similarly grounded while the output coil is untapped. Inter-coil spacing (Fig. 2) is 1 1  and inter row spacing is 1 2  while the inter row stagger is 1 3 . Thus couplings k 1 b, k 4 , k 5  are negligibly low with respect to couplings k 1a , k 2 , k 3 , and the inter-tap coil coupling k 0  # unity, so that the delay line circuitry approximates to that of Fig. 3; in turn reducible to that of Fig. 4 wherein the couplings of adjacent inductances are alternately a 1a  positive and a 1b  negative; those between every second inductance are a 2  and those between every third inductance are a 3 . It is shown that a 1a =αk 0 +#k 1a , a 1b =ak 0  and other couplings are negligible. It is also shown that the couplings may be selected to optional values by varying the inter coil stagger and inter row spacings 1 1 , 1 2 , 1 3  and the tap adjustment, since k 1a  is a function of #l 1 <SP>2</SP>+l 3 <SP>2</SP> and k 3  is a function of #l 2 <SP>1</SP> + (l 1 -l 3 )<SP>2</SP>. A physical structure (Fig. 6) comprises a baseplate 1 grooved at 2 for transverse adjustment of row A and at 3 for longitudinal adjustment of row B; the bases of the A and B rows  having projections 2<SP>1</SP>, 3<SP>1</SP> engaging the grooves. Ferrite rods 6 (Fig. 7) aligned with the rows of coils are carried in apertures of insulant sliders 7 engaged by holders 8 secured at opposite ends of the coil rows, so that the rods are adjustable for proximity to the coil rows. In a modification (Fig. 8) the axes of the coils are horizontal and the turns of coils of rows A, B are of opposed sense while those of the individual coils of the rows are in the same sense, and the respective coils are series connected in succession. The coupling between the coils of row A and those of row B is adjustable from positive through zero to negative with variations of inter row stagger (Figs. 9, 10, not shown). In a further modification (Fig. 11) the axes of the coils are inclined at an angle # to the plane perpendicular to the coil rows, and the coupling between the coils of the respective rows varies with # from positive at #=n/2 to negative at #=0 through zero. The rows of coils may be disposed at different physical levels. Other types of magnetic or non-magnetic cores may be used.