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Link Budget
Link Budget
This link budget has been generated according to the link budget generation process outlined in chapter 13 of Space Mission and Design (2005). Acceptance criteria for this link budget is a link margin exceeding 3 dB for both uplink and downlink. What follows is a brief explanation of the main aspects of the link budget:
EIRP: Equivalent Isotropic Radiated Power, the total power radiated from a transmitter, in a given direction.
Free Space Loss: Loss of signal strength due to travel over long distances of space.
Pointing Loss: Losses due to inaccuracies in antenna pointing.
Receiver Gains/Losses: Gains or losses due to receiver hardware.
Boltzmann Term: Link budget term associated with Boltzmann constant.
Bitrate Term: Losses due to amount of data being transmitted.
Attenuation Loss: Other attenuation losses due to Earth's atmosphere.
Calculated Eb/N0: Sum of all above terms.
Link Margin: Difference between estimated Eb/N0 and required Eb/N0 to meet required bit error rate.
Data Budget
Data Budget
Data budgets were drafted to determine data rate requirements. These budgets are quite conservative both in their derivation and large margin. Based off of these calculations the minimum required data rate was determined as 7.28 kBps (58.24 kbps), well below the system rate of 15.63 kBps (125 kbps).
Normal Ops Budget
Normal Ops Budget
LEOP Budget
LEOP Budget
Subsystem Data Budgets
Subsystem Data Budgets
Patch Antenna Placement
Patch Antenna Placement
Preliminary Analysis (HFSS)
Preliminary Analysis (HFSS)
A preliminary analysis is performed on the simplified model of the double patch antenna with a coaxial feed using the HFSS analysis tool. The simplified antenna is analyzed in no-wing, open-wing, and closed-wing configurations, showing the effects of the solar wing on the performance and gain of the antenna.
Figure 1: a) No-Wing Gain Pattern, b) Open-Wing Gain Pattern, c) Closed-Wing Gain Pattern
It is apparent from the figure above that having the open solar wing positioned perpendicular to the patch antenna does not effect the direction of the gain (peak of the main lobe). However, there are more reflections observed as a result of the aluminum frame. These reflections are shown in figure 3 as prominent side lobes that can cause signal leakage, loss of power, and reduction of the SNR (signal to noise ratio).
Note that the antenna used for this analysis is a simplified version of the model and the antenna parameters are not accurate to the COTS dual patch antenna. This analysis will be modified once the COTS antenna is procured in phase D. It is expected to have a more prominent main lobe using the accurate model of the patch antenna. Given this, the identified 1.65 GHz gain shown below is not an accurate representation of the Dual patch antenna. The gain of the COTS dual patch antenna will be tested in the University of Manitoba's Antenna Lab in Phase D.
Further, in the closed-wing configuration, the direction of the gain is disturbed. Evidence of this can be observed in figure 4 where the main lobe is no longer located at 0 degrees. Also, evidence of polarization leakage is observed in the cross polar gain plot for the 90 degree phi in this configuration.
Figure 2: No-Wing Co-polarization and Cross-Polarization at 0 and 90 degrees
Figure 3: Open-Wing Co-polarization and Cross-Polarization at 0 and 90 degrees
Figure 4: Closed-Wing Co-polarization and Cross-Polarization at 0 and 90 degrees
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