The type 45 has 2 radars. The first is the S1850M volume search radar (rear mast on the vessel) this is a traditional type radar system used for long
range high volume search. It was developed as part of the PAAMS when we were part of the horizon frigate progamme. When we switch to the type 45
development it was retained as a legacy part of the design. it is actually not needed (according to BAE systems) as the type 45s have the addition of
the Sampson radar system.
It was originally developed by Siemens-Plessey, the radar is a result of UK government's (DERA) investment in the MESAR demonstrator programme
(Multi-function Electronically Scanned ARray.) Siemens-Plessey was acquired by British Aerospace in 1997, now BAE Systems.
As an active array, SAMPSON uses software to shape and direct its beam allowing several functions to be carried out at once and, through adaptive
waveform control, is virtually immune to enemy jamming. Active arrays have both longer range and higher accuracy than conventional radars.
People all too often fall into the trap of thinking that because the samson radar rototes it must be a mechanically scanned array. This is simply not
true. The system consists of two arrays placed back to back. These two arrays are both electronically scanning active phased arrays. The design
choices for using the two rotating arrays are that it will save weight and thereby allow the radar to be sighted higher up giving a larger range with
little or no loss in functionality.
The combination of the rotating back to back arrays (rotating at over 30rpm, actual value is classified) and the electronic scanning mean that it can
put a a beam anywhere at anytime (they are coordinated by special software). Bae investigated a number of different designs including 1, 2, 3, 4 and
5 (a vertical one) arrays and found the 2 rotating array design to be the best choice in performance vs weight.
As an aside in a recent test the sampson radar being tested near Portsmouth tracked all aircraft flying into and out of heathrow, Gatwick, Stanstead,
Paris CDG, Berlin and Schiphol (amsterdam) at the same time.
Lockheed were so impressed with the designs a few years ago they even talked about joining forces with Bae on future devlopment of radars.