Value chain · CLM-0980
In plain terms
The company that designed the timing system in 1978 handled the bending of the transmitter by dividing it into groups of patches, each with its own small computer working out the correction from where the guide beam appeared to come from and where that group's elements actually were. How big a group could be depended on how much the structure bent. The report also shows how much cable length matters: two centimetres of mismatch between levels is about 58 degrees of error at 2.48 GHz but under two degrees at 70 MHz, and its remedy is to keep the cable lengths matched.
The claim as recorded
LinCom's 1978 design answers the flexing question by grouping: "Due to the flexing of the SPS antenna, it is divided into groups of subarrays", each group served by one phase-correction computer fed by a monopulse tracker reading the pilot's arrival angle and by the positions of the radiating elements in the group, and "the number of subarrays in the group is determined by several factors, e.g., antenna flexing, plane waves approximation of a spherical wave". The same report puts the reference on a master slave returnable timing system with one phase control centre per subarray and "zero phase build up" from path delays, 1,364 PCCs plus one master; it converts 2 cm of differential cable length to about 58 degrees at 2.48 GHz against 1.68 degrees at 70 MHz; and it sets the phasing system's jitter "below 6 degrees" for 96 per cent transmission efficiency.
Evidence behind this: T3-contractor report, the designer of the baseline phase control system.
Scope and limits
THE GROUP SIZE IS NAMED AS A FUNCTION OF FLEXING AND NOT GIVEN A VALUE, and no flexing amplitude or frequency is stated anywhere in the report; the register's CALC-109 amplitudes are what this design would need as input. The 6 degrees and the 96 per cent are LinCom's own loss relation and are not the same quantity as Boeing's later 7.09 degrees at 1.53 per cent (CLM-0978).
What it assumes
Square 14 m x 14 m subarrays, 4,096 in the array, in the worked example (p.61); the group size itself is not given a number.
Where it comes from
p.110, normalised: "Due to the flexing of the SPS antenna, it is divided into groups of subarrays. In each subarray there are M radiating elements and, along with each radiating element, there is a power amplifier and a conjugating circuit." p.113: "There are two inputs to this computer: the input from the monopulse tracking svstem producing azimuth and elevation angles of the arriving pilot beam and the other position coordinates of all the radiating elements in the group of subarrays... The number of subarrays in the group is determined by several factors, e.g., antenna flexing, plane waves approximation of a spherical wave" ("svstem" in the layer). p.78: "8.4 Master Slave Returnable Timing System Hybrid Configuration... In this system there is only one PCC per subarray to receive the incoming phase... The operation of this system is independent of the path delays which means zero phase build up." p.6: "1364 PCCs are required plus one master PCC." p.27: "for 2 cm. differential cable length we have about 58 degrees of phase build up at 2.48 GHz and 1.68 degrees at 70 MHz." p.127: "to obtain the power transmission efficiency of 96%, the phase jitter introduced by the phasing system should be below 6 degrees."
Basis: degrees of phase; groups of subarrays; phase control centres
Related records
- Answers question
- QST-013 not published in this release
Cite this
energyaperture.com/c/clm-0980
CLM-0980, Energy Aperture, as of 1978-02.
Connected records
Other published records linked to this one. A list, not a judgement.