318 BELL SYSTEM TECHNICAL JOURNAL 



ceiving station Is always an integral multiple of either: 



d[\-\cosl) (4) 



or 



so that for either the front or the rear group the delay compensation 

 could be adjusted by means of a single shaft geared to various indi- 

 vidual delay compensators through gears having integral ratios. 



Practically, the difficulty in building continuously variable delay 

 circuits resulted in the use of continuously variable phase shifters. 



For any particular delay t there is a corresponding phase shift — r— 



A 



radians. Since this phase shift is a function of frequency, for a given 

 phase shifter setting the frequencies in a wide band transmission will 

 not all be in phase. The substitution of phase shifters for delay 

 compensating circuits therefore results in a restriction of the band of 

 simultaneous reception from a given angle. For the group of antennas 

 ahead of the station the band restriction is small, since the space and 

 transmission line paths give a partial delay compensation. For the 

 antennas behind the station the net delay difference between antennas 

 is large and the band Is restricted to a much greater extent. 



When using phase shifters It is possible to get minus as well as plus 

 values of phase shift. This makes it possible to reverse the order in 

 which delay compensation was assumed to be added in the above 

 discussion so that no phase compensation is added to antenna 9, one 

 negative unit is added to antenna 8, two to antenna 7, etc. In the 

 equipment herein described the phase shifters were so designed. 



Assume that the phase shifters of the front group are all set alike 

 and then changed so as to receive from an angle 8. There will have 

 been Introduced a change of phase of 



lircd / 1 1 \ 



= — (---COS6J (6) 



between each of the antenna outputs. 



Similarly If the phase shifters of the rear group were initially set 



alike, and similar to the initial condition of the front group, and then 



changed to receive from an angle 5 the change of phase which would 



be required would be 



lircd / 1 , 1 \ ,„, 



- + - cos 5 . (7) 



V c 



