Phase II Final Report - NASA's Institute for Advanced Concepts

Planetary Exploration Using Biomimetics
An Entomopter for Flight on Mars
4.3.6 Link Budget Results
The specifications for the radar portions of the system requirements are more stringent compared
to the communications requirements. Thus, initially system parameters will be based on
radar performance, and communications calculations will be based on these assumptions.
4.3.6.1 Obstacle Detection Results
The following assumptions were made for the radar to perform obstacle detection.
Table 4-1: Parameters for Obstacle-detection Analysis
Effective target cross section, σ (m 2 ) 1
Temperature of receiver To (Kelvin) 290
Range resolution, ∆Rmin (m) 0.5
Isotropic gain of transmitting antenna G T (dBi) 8
Signal-to-noise ration (dB) 10
Interpulse period, T (ms) 1
Pulse repetition frequency, (kpps) 1
Following the analysis procedure outlined above, the required peak and average transmitter
powers are shown in Figure 4-15 for an operating frequency of 18 GHz. It was determined that
the minimum and maximum distances for obstacle detection are about 15 m and 200 m, respectively,
and range resolution should be held to about 0.5 m. Using the assumptions shown in
Table 4-1, the peak and average powers at 18 GHz for a 15-m range are 2.4 µW and 8 pW,
respectively. The peak and average powers for a 200-m distance are 76 mW and 254 nW, respectively.
The required peak and average powers are plotted as a function of operating frequency in
Figures 4-16 and 4-17, respectively. For the chosen parameters, there is little variation in power
with frequency. The plots do indicate a savings in required power at frequencies below 0.5 GHz.
However, using the chosen pulsewidth, physically realizable operating frequencies are limited to
values greater than 0.6 GHz to maintain a bandwidth greater than twice the operating frequency.
Peak and average powers at 18 GHz
0.1 1 0.01
1.10 3
1.10 4
1.10
1.10 6
5
1.10 7
1.10
1.10 9
8
1.10 10
1.10 11
1.10
1.10 13
12
1.10 14
0 50 100 150 200
Range (m)
Peak
Average
Figure 4-15: Peak and Average Transmitter Power Required for Obstacle Detection at
18 GHz as a Function of Range
Power (W)
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