Project Cyclops, A Design... - Department of Earth and Planetary ...

9. THE RECEIVER SYSTEM
The receiver system consists of three subsystems:
(1) the antenna feed system, (2) the signal conversion
system, and (3) the local oscillator system, as shown in
Figure 9-1. The following were considered to be the
most important requirements for the Cyclops receiver
design:
1. High aperture efficiency. Because the major expense
of the Cyclops system is the cost of the
collecting area, it is imperative that the area be
used efficiently. A 10% increase in aperture
efficiency could represent a saving of a billion
dollars in the full-scale system.
2. Low noise temperature. A two to one reduction in
system noise temperature is equivalent to a twofold
increase in antenna area. The cost of liquid
helium cryogenics is saved many times over in
antenna cost, and only the lowest noise front ends
were considered. For the same reason only very
low ground spillover feeds can be used.
3. Wide instantaneous bandwidth. The wider the
bandwidth that can be searched simultaneously,
the less will be the search time per star. Ideally, we
would like to search the entire microwave window
at one pass but present technology and interfering
signals from Earth do not allow this.
4. RapM remote band switching. Because no low
noise receiver can cover the entire band of
interest, and because on-site receiver tuning is out
of the question in an array of a thousand or more
elements, the receivers must be rapidly and remotely
tunable and capable of being bandswitched
from the control center.
5. Universal polarization capability. Cyclops must be
able to receive with minimum loss a signal having
an arbitrary polarization. Beacons may be expected
to be circularly polarized (Chap. 6) but
may be either left or right, and leakage signals
could
have any polarization.
FEED
SIGNAL
6. Automatic phasing, calibration, and fault detection.
The Cyclops array must remain properly
phased at all times, with all elements delivering the
same signal amplitude without operator attention.
This means the system must incorporate computer-controlled
calibration and fault-location
systems.
SYSTEM
CONVERSION
SYSTEM
Figure 9-1.
1
ANTENNA
FEED
LRI_FF _R "_l LOCAL OSCILLATOR
AMP I SYSTEM
.._ !I LOCAL OSCILLATOR
I LOCAL
SYNTHESIS
AND
OSCILLATOR
l AM#LFFIER DISTRIBUTION I
IFREQUENCY
I _ STANDARD ]
Major elements of the Cyclops receiver.
The receiver design outlined here is believed capable
of meeting the above criteria as well as the present state
of the art allows. The design is not complete in detail
and, of course, in some areas, such as optimization of
feeds, a great deal of experimental work would be
needed to arrive at the best final design. Nevertheless,
the design permits some rough estimates to be made of
performance and cost.
The proposed design covers the low end of the
microwave window from 500 MItz to 3 Gttz and is
capable of being extended to 10 GHz if desired. Six
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