If aircraft and ships are equipped with beacons capable of communicating with satellites, rescue efforts may speed up significantly. In event of disaster, beacons can transmit distress message to satellite which, in turn, will relay message to nearest rescue center, indicating distress location

Shores, P. W.

English

NASA Technical Reports Server

Tiplifiers 
September 1973	 B73-10318 
• 
NASA TECH BRIEF 
Lyndon B. Johnson Space Center
	
A 
NASA Tech Briefs announce new technology derived from the U.S. space, program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Scanning Beacon Locator System: A Concept 
Reception Pattern

3 Beams 
% 2 
P-? 
Array Elements
Local	 "	 -'	 Local
Beam	 Beam	 Beam 
3	 2	 1 
Figure 1. Multiple Beam Array 
Aircraft and ship disasters often sustain many casu-
alties because the rescue crews cannot locate and get to 
them quickly enough. With present communications, the 
search may continue for hours and sometimes days, 
particularly in bad weather. In the future, however, 
rescue efforts may speed up significantly if aircraft and
ships are equipped with beacons capable of communi-
cating with satellites. In the event of disaster, these 
beacons can be activated and transmit a distress message 
to a satellite which, in turn, will relay the message to the 
nearest rescue center, indicating the distress location. 
To be practical, this system must meet at least two 
(continued overleaf) 
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. 
Antenna
round Beacon 
if they were from separate receivers. By varying the 
amounts of relative phase shifts, multiple beams are 
formed simultaneously. All beams can be swept in 
synchronism, using the signal beam steering signals 
(see FigUre 1). 
The ground beacon, by definition, must be simple, 
small, and inexpensive. One concept of such a beacon 
is shown in Figure 2. The heart of the beacon constitutes 
either avalanche or bulk devices that essentially oscillate 
when mounted in an appropriately tuned cavity or strip-
line and the proper dc voltage is applied. 
Modulation of the signal is easily accomplished by 
interrupting the supply voltage. The coded message 
amplitude modulates the carrier. The codes are generated 
from an integrated circuit clock (1 chip) and a four-bit 
shift register (1 chip); the modulator is the final chip. 
The antenna is a simple stripline antenna. Based on this 
design, it is possible to fabricate the entire circuit in a 
single large-scale integration (LSI) chip, including a 
microwave-integrated circuit antenna. 
Notes: 
1. These beacons may also be used in automobiles, 
boats, and other vehicles, to send distress signals from 
remote locations. 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Lyndon B. Johnson Space Center 
Code JM7 
Houston, Texas 77058 
Reference: TSP73-10318 
Patent status: 
Inquiries concerning rights for the commercial use of 
this invention should be addressed to: 
Patent Counsel 
Lyndon B. Johnson Space Center 
Code AM 
Houston, Texas 77058 
Each array element is mixed with a local oscillator 
signal and amplified in an IF amplifier. The output of 	 Source: P. W. Shores 
each amplifier is subdivided into a number of inde-	 Johnson Space Center 
pendent signals, which are summed with other signals as 	 (MSC 12593) 
B73-10318
	 Category 02 
Figure 2. G 
requirements. First, the beacons must be relatively 
inexpensive, and second, satellites must be capable of 
searching an area as large as the continental United 
States (approximately 5000 by 3200 km) and locating 
the distress signal to an accuracy of 2km. 
To cover a large geographical area such as the conti-
nental United States, the satellite should orbit above 
some fixed geographical location (geo-synchronous). 
In this case, the orbit altitude is about 36,200 km. The 
antenna must be capable of scanning a 3200- by 5000-km 
area within 10 seconds and locating the beacon within 
2 km. Acquisition time must be no greater than 10 
seconds after activation of the beacon. 
Various computations were performed to determine 
if such an antenna was technically feasible. To scan the 
specified area within 10 seconds, the horizontal scan-
line rate was computed at 160 lines/second along a 
3200-km front. This rate is possible only with electron-
ically scanned, phased arrays.' Resolution as a function 
of surface was computed as 1.37 S (arc), where S is the 
surface distance. Antenna aperture as a function of 
wavelength was calculated to be 16,181X, where A is 
the wavelength of operating frequency. 
Based on the accuracy goal of 2 km, the operating 
frequency range for the antenna is between 5 and 
30 GHz. Peak pulse powers of 10 watts are generally 
available throughout these bands and are used as a 
basis for further calculations.	 - 
The RF bandwidth based on non-return-to-zero (NRZ) 
data of four bits per element was computed at ap-
proximately 3.5 MHz. Based on this bandwidth, a 
signal-to-noise power ratio of 6 dB and transmitter 
power of 10 watts, the computed antenna diameter 
is 29.6 m. Using 10,000 elements, the size of the array 
is 875 m2 ; its weight is approximately 62,000 kg 
(136,000 lb). Both the antenna size and weight can be 
reduced by a factor of four approximately, by dividing 
the search area into four sub-areas and using four 
hpm.
.


Scanning beacon locator system: A concept

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