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CySAT Receiving UnitDesign ReportDec. 02th, 2009
Revised
Apr. 20, 2010
Group #: May 10-07
Client: Matthew Nelson/ ISU CySAT Group
Faculty: John Basart
Group Members : Karl Deakyne
Luke Olson
SungHo Yoon
Table of Contents
1. Introduction 41.1 Executive Summary 41.2 Acknowledgement 41.3 Problem Statement 41.4 Operating Environment 4
1.5 Intended Users and Uses 51.6 Assumptions and Limitations 51.7 End-Product Description 5
2. Approach 62.1 Approach Used 62.2 Detailed Design 112.3 Cost Estimate 172.4 Schedules 18
3. Project Team Information 194. Closing Summary 195. References 19
Appendix A: Received Power and Noise Temperature Calculations 20 Appendix B: Calculations for HABET Testing 30
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List of FiguresFigure 1: A Radio Telescope at Fick ObservatoryFigure 2: Component Level System DiagramFigure 3: Amplifier SpecificationsFigure 4: Filter SpecificationsFigure 5: Switch Specifications
List of tablesTable 1: Parts ListTable 2: Total Estimated CostTable 3: Work Schedule
AppendicesAppendix A: Design Constraint Calculations (Received Power, SNR, etc)
List of DefinitionsCySAT (Cyclone Satellite)This is an educational project that students are required to solve complex problems like satellite tracking, communication, control, etc. The goal of the project is to launch a cubes satellite into orbit in the coming years.
SSCL (Space Systems and Control Lab)A lab at Iowa State University founded to carry out academic and scientific missions; those missions include CySAT and HABET.
HABETA project conducted through the SSCL that launches payloads into high altitude using a balloon system.
Low-Noise Amplifier (LNA)An electronic amplifier used to amplify very weak signals captured by an antenna.
Signal to noise ratio (SNR)A measure of signal strength relative to background noise.
Ham Radio Deluxe (HRD)A program that tracks the elevation and azimuth of an orbiting satellite and works with a radio to receive and transmit messages. (Among other things)
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1. Introduction
The following section will introduce the project with the abstract, problem statement, and other background information.
1.1. Executive Summary
The Space Systems and Controls Lab is operating its Cyclone Satellite (CySAT) project that aims to launch a cubesat satellite in the near future. In order to communicate to the satellite and receive information from the satellite, a ground station will be needed. Iowa State currently owns a large dish antenna, a two-phase senior design project has been undertaken to convert this dish into the ground station. The first phase (currently Senior Design 492 ) is working on tracking the satellite and receiving signals 440MHZ. Our phase will be working on the demodulation of the received signals, and modulation and transmission of messages at a frequency of 440 MHz as well as finishing the satellite tracking. The end product will be able to track the satellite, receive and demodulate messages from the satellite, and transmit messages to the satellite.
1.2. Acknowledgement
First of all, the team would like to thank the family of Milo Mather, who donated the ISU’s original telescope and observatory in 1960. This project would not be possible without their contribution.
Also, the team would like to the Space Systems and Controls Lab for supporting the CySat project as well as our project.
1.3. Problem Statement
The cubesat has limitations that require it to be very small, and also needs to operate at very low power. The large dish at Fick Observatory will give us a large gain on the received signal, which will allow the cubesat to send a less powerful signal. However, due to the low power signal we will need to minimize loss after the signal is received and minimize the noise factor of our system in order to properly demodulate the signal. Furthermore, we will need send relatively high power signals to the satellite to ensure the satellite’s receiver can be low power and small in size.
1.4. Operating Environment
The radio telescope is located outdoors at Boone, IA. To maximize the system’s signal-to-noise ratio (SNR), high frequency components of the signal amplification system,
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such as the low noise amplifier (LNA), must be located near the antenna’s feed horn. Likewise, some devices for demodulation can be exposed to Iowa’s harsh weather; rain, snow, ice, and extreme temperatures.
1.5. Intended User and Intended Use
The primary user will be a CySAT team in the Space Systems and Controls Lab, and those who are related to CySAT remote communications. These users will be able to control the satellite dish remotely at Iowa State University, and they will receive the demodulated binary data which is a message from CySAT.
1.6. Assumptions and Limitations
1.6.1. Assumptions
• The CySAT satellite will transmit its message though 1.2GHz or 440MHz frequencies.
• The satellite dish moves so that its remote control can be possible, and the dish has received 440MHz without much noise.
• Messages will be transmitted with a 9600 baud rate.
1.6.2. Limitations
• Current budget is $240.
• Components must be resistant to harsh Iowa weather conditions.
1.7. Expected end product and other deliverables
The end product from our design team shall include a 440 MHz transceiving unit. Our end product will receive a modulated 440 MHz signal from the 492 senior design group’s antenna and deliver the message signal to the CySat computer located at Fick Observatory. Our device also has a transmitting branch, which modulates a message signal from the computer and delivers it to a 440 MHz antenna.
Along with the physical device, our group will implement software for tracking satellites using satellite location data via Ham Radio Deluxe.
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At the end of the year the ground station should be ready to use by the CySat team.
Figure 1: A Radio Telescope at Fick Observatory
Approach
Approach Used
Design ObjectivesThe objectives of our project reflect a solution to the project problem definition listed above. These objectives are summarized below:
Required Objectives
• Performance as a 440 MHz transceiver• Have at least 10 Signal to Noise Ratio through system • Have a low cost • Tracking Software• Implementation at Fick Observatory
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Optional Objectives
• Simple Implementation• Low Power
Functional Requirements
The system shall receive and demodulate signals at 440 MHz
The system shall modulate and transmit signals at 440 MHz
The system shall deliver the received messages to a computer.
The system shall deliver the transmitted signal to an antenna
The system shall allow automatic tracking of orbiting satellites
Non- Functional Requirements
The system shall withstand harsh weather conditions
The system shall minimize the required strength of the incoming signal.
ConstraintsOur system is constrained by many factors, both physical and intangible. The constraints are summarized below.
Design Constraints
• Limit of signal degradation given by Link Budget and Noise Factor Calculation (See Appendix A)
• Budget limited to $240• Must fit on antenna tower• Must accommodate for the frequency shift caused by the Doppler Effect• Antenna tower and lab linked by 200 ft cable• Transmitting signal power is 36.9-40 dBm
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Technology ConsiderationsThe approaches considered in our design can be broken down into the two stages of our system. The First Stage includes the system on the antenna tower. This First Stage is required to get the signal/s from the antenna/s to the coax line. The Second Stage takes the signal from the coax cable, demodulates it and delivers it to the lab computer.
-First Stage Approaches
1.2 GHz transceiver with 440 MHz receiver
Description: This was our original concept design, which included the down conversion of both signals and a transmitting path for the 1.2 GHz
signal
Advantages:
• Two way communication on 1.2 GHz signal• Can interpret 440 MHz signal from antenna• Low loss over coax cable form antenna to lab
Disadvantages:
• Many Devices; High Cost• Lengthy Implementation and testing
440 MHz transceiver
Description: As or design evolved, we needed a simpler system and our client redefined the problem statement. The 440 MHz signal now took
precedence and it needed to both transmit and receive.
Advantages:
• Two way communication on 440 MHz signal• Few Devices, Low cost• Realizable with our time frame
Disadvantages:
• No 1.2 GHz communication in design
-Second Stage Approaches
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Software Defined Radio
Description:
We considered using a software defined radio in our design in order to receive two signals, 1.2 GHz and 440 MHz, and to transmit those frequencies as well. A software defined radio uses processors in order to perform most of the functions of the radio. In this way it allows great flexibility in the signal processing and minimizes the amount of hardware required.
The required hardware would be the Universal Software Radio Peripheral (USRP) and software from www.gnuradio.org to do most of the signal processing on the host computer. The USRP handles analog to digital conversion and accepts daughter boards for down-converting high frequency signals.
Advantages:
• Low cost, when working with a wide array of frequencies• Easy to change modulation scheme• Easy to quickly change frequency of incoming or outgoing signal
Disadvantages:
• Relatively high cost, when working with a fixed frequency• Set up time is relatively high • New technology, therefore more limited support
Off the Shelf Radio
Description:
The alternative to a software defined radio is a traditional radio. A traditional high frequency radio down-converts and demodulates received signals and modulates and up-converts signals to be transmitted.
With the off the shelf radio we will need additional hardware (possibly a sound card) to do the analog to digital conversions and vice-versa.
Advantages:
• Well established technology• Relatively low cost for more narrow band of received frequencies• Easy set up
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Disadvantages:
• More narrow band for receiving, will need two radios to receive both 440 MHz and 1.2 GHz
Selected DesignFor the final design we chose to implement the 440 MHz transceiver for the First Stage and the off the shelf radio for the Second Stage. Overall, we’ve decided on this design for a low cost system with simple implementation that receives and transmits a 440 MHz signal. We chose against the software-defined radio because of its extensive cost and decided to implement the 440 MHz system only to keep our system realizable.
Testing Requirement Considerations
End Product The end product can be tested in three ways. First, we generate signals directly from Fick Observatory and ensure that the system acts as expected. This approach will be the easiest and will also provide good feedback, because we will know exactly what the system should do. However, this approach ignores many of the complications that come with receiving signals from satellites that are in orbit.
The second way is to find a satellite currently in orbit that outputs signals at the correct frequency, and test that the system receives those signals correctly. This approach will require more research and will be more dependent on other parts of the overall system. Also, we will not know exactly what we should be receiving which will give less accurate testing results.
The final method will be to conduct a test during ihe CySAT team’s planned test launch of the satellite by using a balloon to get the satellite to near orbit altitude. This will provide an excellent testing opportunity for our team.
Incremental Most of the system testing will be spent on incrementally testing each component. Each part that we buy must be tested in order to confirm that it will perform to our needs. Also, the integration testing between each of the components will need to be tested thoroughly.
HABET Balloon LaunchIn the spring of 2010 CYSAT will be working with the HABET program to perform a test launch of a prototype cube satellite. This presents a unique opportunity to test various components of our system. Inherently, we will be testing the tracking capabilities of the ground station in order to track the satellite for communication (See Appendix B for tracking calculations). We will also test our system’s communication capability by transmitting and receiving test messages to/from the
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cube satellite.
Recommendation for Project ContinuationAt this time, our team recommends that the project continue as planned. Our design is fully realizable, stays within all of our constraints, and can be delivered and implemented this spring.
Detailed DesignOur system is decomposed into stages. In the first stage moves the signal from the antenna to the second stage and vice versa. The second stage demodulates the incoming signal and delivers it to the computer or takes a message from the computer, modulates it and hands it off to the first stage.
The first stage has two paths to accommodate both transmission and reception of the 440 MHz signal. We looked at a few switch implementation methods and found that the simplest method is just using two switches, creating a receiving branch and a transmitting branch.
\
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Coax cable
Switch
SMA to SMA connector
SMA to SMA connector
440 MHz LNA
Coax cable, 200 ft
440 MHz Filter
Off the shelf radio
To/from computer
N-type to SMA bulkhead adapter
SMA to SMA connector
Switch
BNC to SMA bulkhead adapter
To/from antenna
Figure 2: Component Level System DiagramAs you can see from the system diagram, the receiving branch is composed of a Low Noise Amplifier and a 440 MHz filter. The transmitting branch just has a cable connecting the two switches. Both of these implementation schemes are explained later.
The second stage of the system is an off the shelf radio which takes the 440 MHz signal, demodulates it and delivers the analog baseband signal to the computer sound card. At this point the computer can perform the analog to digital conversion of received signals as well as generate, modulate and transmit baseband analog signals to the radio. A 200 foot coaxial cable connects the two stages.
Not pictured in the diagram are the DC power cables that will send power to our box and the DC power strip that will act to prevent forces on the wires acting directly on the devices, i.e. if wire is pulled off, it is pulled off the power strip and not the device.
Table 1: Parts List
Part Retailer Part No. Price Quantity
SMA to N-Type Bulkhead Adapter
Fairview Microwave SM4239AA 22 1 $22
BNC to SMA Bulkhead Adapter
Fairview Microwave SM4712b 21 1 $21
SMA to SMA connector Minicircuits SM-SM50+ 5.95 4 $23.80 440 MHz LNA Minicircuits ZX60-33LN+ 79.95 1 $79.95 440 MHz Filter Minicircuits SLP-550+ 34.95 1 $34.95 Switch Mouser 881-CCR-33S6O 91 2 $182 Coax cable In lab $0 Power Strip In lab $0 DC Cable In lab $0 Off the shelf radio AESHam Icom 208H 310 1 $310Total $674
In Depth Design
There are four main parts of our design (radio, amplifier, switch and filter), each with its own desired specifications. Each has a description below, along with the desired and actual specifications.
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RadioDescription: Our radio’s sensitivity helped us to determine the specifications of
the other parts of our system. We desired a low sensitivity since it would reduce the amplification needed. The radio needs to transceive signals at 440
MHz with a baud rate at 9600.
Desired Specifications:
• Low sensitivity, around incoming signal -105.6 dBm
• Low price
Actual Specifications:
• Sensitivity: .18uV, -121.8 dBm
• Price: $310, one of the lowest that meet the requirements
AmplifierDescription:
From our link budget calculation, we found the receiver sensitivity was already lower than the incoming signal power. We debated whether we would need an amplifier at all, but determined that an LNA would help us with the signal bandwidth and the Signal to Noise ratio. To avoid harmonic frequencies in the received signal, we wanted a cutoff frequency just above 440 MHz, but this was not available, so we implemented a filter after amplification. Also, to avoid loss from multiple conversions, we wanted all devices in the box to have SMA connectors.
Desired Specifications:
• Some Gain
• Low Noise Figure
• Coaxial Connectors (SMA)
• Low Bandwidth, cutoff just above 440 MHz
Actual Specifications of ZX60-33LN+:
• Gain at 440 MHz: about 20 dB
• Noise Figure: Typical 1.1 dB
• SMA connectors
• Frequency Range : 50 – 3000 MHz
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Figure 3: Amplifier Specifications-Graphs and Table from mini-circuits ZX60-33LN+ datasheet
FilterDescription:
Since the amplifier was so broadband, we determined that harmonics of the incoming signal could present a problem for our system. We desired a Low Pass filter that would filter out signals just above 440 MHz, had an acceptable power rating, and that had SMA connectors.
Desired Specifications:
• Low Pass Cutoff frequency just above 440 MHz
• Power Rating higher than -101.8 dBm
• SMA connectors
• Passive Fiter (Optional)
Actual Specifications of SLP-550+:
• Cutoff Frequency: 570 MHz
• Power rating: 26.9 dBm
• SMA connectors
• Passive Filter
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Figure 4: Filter Specifications
-Graphs and Table from minicircuits SLP-550+ datasheet
SwitchDescription:
After we found our Low Noise Amplifier and our Low Pass Filter, we needed to find our switches. These switches are particularly important because they allow our device to operate as both a receiver and a transmitter. We needed a single pole double throw switch that could be controlled through an electrical signal (since the location makes physical switching undesirable), that had a fast switching speed, that had low loss, and that power rating high enough for transmission. The chosen part may seem to exceed specifications unnecessarily, however the specifications are quite common for electromechanical switches at these freqeucies.
Desired Specifications:
• Switching Speed: Luke what was this?
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• Insertion Loss less than .1 dB
• Power handling greater than 10 W
Actual Specifications of CCR-33LT
• Switching speed: 10ms Max
• Insertion Loss .2 dB
• Power Handling greater than 200W at 440 MHz
Figure 5 : Switch Specifications-Graph and Table from Teledyne CCR-33LT datasheet
ConnectorsDescription:
These parts were selected to put every other piece together. The connector on the antenna is BNC, and the outgoing cable has an N-type connector so we needed two conversion pieces on the edge of our box. Also, every most devices in the box have SMA female connectors on them, with the exception of the filter, which has both a male and a female, so we needed a total of four male-to-male SMA connectors. We wanted these connectors to have a characteristic impedance of 50 ohms, which each device meets.
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Cost EstimateThis is an abbreviated representation of the estimated costs for the project. For a more detailed representation, please refer to the Project Plan document.
Table 2: Total Estimated CostTask Without Labor ($) With Labor ($)
Project Reporting 0 $1440
Checking Radio Telescope 0 $360-370
Component Consideration (and purchase price) $674(see Table 1) $1290
Device Testing 0 $480-600
Implementation 0 $360
On Site Testing 0 $300
End-Product Documentation 0 $450
Totals: $674 $4580-$4710
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1.8. Schedules
Weekly reports will be finished and handed in every Sunday.
Table 3: Work Schedule
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2. Project Team Information2.1. Client Information
Name: Nelson, Matthew EDept.: Aerospace Engineering
Office: 2348 Howe Hall, Ames, IA 50011-2271
Email: [email protected]
2.2.Faculty advisor InformationName: Basart, John Philip
Dept.: Aerospace Engineering
Office: 2361 Howe Hall, Ames, IA 50011-2271
Email: [email protected]
2.3. Student Team InformationName: Deakyne, Karl Robert
Major: Electrical Engineering
Email: [email protected]
Name: Olson, Lucas Jens
Major: Software Engineering
Email: [email protected]
Name: Yoon, SungHo
Major: Electrical Engineering
Email: [email protected]
5. Closing SummaryWithout a ground station to effectively communicate with the satellite, the CySAT team might as well send a rock into orbit. As with most things communication is the key to success, and we will do everything we can to provide the CySAT team with a system that will make the CySAT project a success.
6. ReferencesJohn Basart, Technical AdvisorB.P. Lathi, Zhi Ding. Modern Digital and Analog Communication Systems. 4th Ed.
Oxford University Press.Superheterodyne receiver and IF Amplifier, http://www.radartutorial.eu/09.receivers/rx05.en.html
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Appendix ACalculations for Power Gains and Losses from the CySAT to Radio
The power calculations are divided into three parts. The first part is link budget to estimate received power at the satellite dish. The second part is about a noise power calculation by noise temperatures. We can calculate SNR from the first two parts. The third part will be a power calculation inside of the designed system. By calculating these three parts, we expect to determine if the signals from the cubesat is receivable, if we can receive high quality signals, and if the radio can decode the input signals in the designed system.
• Link Budget
Link budget is defined as the accounting of all of the gains and losses from transmitter to receivers so that the link budget shows the received power at the satellite dish. With the link budget calculations, we can check if the received signal is receivable by comparing it to its antenna noise.
Note: In link budget, the “receiver” is denoted by a satellite antenna, not radio.
Here is the equation for link budget.
where: PRX = received power (dBm) PTX = transmitter output power (dBm) GTX = transmitter antenna gain (dBi) LTX = transmitter losses (coax, connectors...) (dB) LFS = free space loss or path loss (dB) LM = miscellaneous losses (fading margin, body loss, polarization mismatch, other losses...) (dB) GRX = receiver antenna gain (dBi) LRX = receiver losses (coax, connectors...) (dB)
<Reference: http://en.wikipedia.org/wiki/Link_budget >
Results: (Used Equation: PRX, Worst = PTX +GTX - LTX - LFS, Worst - LM + GRX - LRX)
PRX 1.2GHz 440MHzThe Worst Received Power -109.11 dBm -109.11 dBm
1 PTX = transmitter output power (dBm) 30.0 dBm2 GTX = transmitter antenna gain (dB) 0.0 dB3 LTX = transmitter losses (coax, connectors...) (dB) 2.0 dB4 LFS = free space path loss (dB) 157.5 dB5 LM = miscellaneous losses (dB) 5.0 dB6 GRX = receiver antenna gain for 440MHz (dB) 28.4 dB7 LRX = receiver losses (coax, connectors...) (dB) 3.0 dB
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Process Calculation:
• Transmitter output power: 30.0 dBm CySAT team is planning that their satellite has 1W transmitting power. The 1W is converted to 30dBm in dB scale.
• Transmitter antenna gain: 0.0 dB
The transmitter antenna gain is assumed to be almost zero because the antenna size of the cube sat is very small which means it cannot amplify much power.
• Transmitter losses: 2.0 dB
CySAT team expects that the transmitter losses will be about 2.0dB.
• Free-space path loss: 157.5 dB
Free-space path loss is proportional to the square of the carrier frequency and also the square of the distance between the transmitter and receiver. The equation for the free-space path loss is:
[W]
, where : The signal wavelength (in meters)
: The signal frequency (in hertz)
: The distance from the transmitter (in meters)
: The speed of light in a vacuum, 2.99792458 × 108 meters / second
• The unit [W] could be converted to [dB] by the equation, .
• The distance from the transmitter to the receiver, :
By Pythagorean Theorem, the longest distance is 4056 km where the radius of earth is 6357 km. Also, the shortest distance (dshortest) is given by Cysat team, which is 1200km.
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Distance between the satellite dish and the cube sate.
With the longest distance, we could calculate the path losses like below, and 157.54dB loss is what we consider mainly for our design.
Free-space path loss (FSPL)
Best Case (90 °) Worst Case (0 °)
Carrier frequency 1280 MHz 1280 MHzPath distance 1200 km 4086 km
FSPL 4.14E+15 W 4.80E+16 W156.17 dB 166.81 Db
Carrier frequency 440 MHz 440 MHzPath distance 1200 km 4086 km
FSPL 4.89E+14 W 5.67E+15 W146.89 dB 157.54 dB
• Miscellaneous losses: 5dB
There are not huge miscellaneous losses in transmitting/receiving, but we suppose it is 5dB loss because we need to think of the worst case.
• Receiver antenna gain: 23.5 dB
The gain of an antenna with losses is proportional to antenna efficiency and physical antenna area, and it is inversely proportional to the square of the wave length. The antenna efficiency is assumed to less than 50 % in case of 440 MHz because the antenna for 440MHz is made by an amateur team that does not have much antenna-design experiences. We use 45% for the antenna efficiency. Here is the equation and the results for antenna gain.
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<Reference: http://www.tscm.com/antennas.pdf>
Receiver antenna gain 1.28 GHz 440 MHz2r, (antenna Diameter) 8.5 m 8.5 mA, (antena area) 57.3 m2 57.3 m2
ƞ, (efficiency) 45 % 45 %λ (=c/f) 0.25 m 0.68 mG (gain) 37.1dB 28.4dB
• Receiver losses: 3.0 dB
The coax cable from the satellite dish to the LNA box we designed is about 30 feet, which losses are assumed about -2.80dB. For the total receiver losses, our team advisor has suggested it is about 3dB loss.
• Noise Power (by Noise Temperature)
Noise power is obtained from the noise temperature. The noise temperature is one of the ways to describe signal-to-noise degradation. High noise temperature means that there is large noise, vice versa. The noise temperature can be described like below.
, where
T0= 290 K (a standardized temperature in Kelvin (290 K is an IEEE standard))F = noise factor= (Sin/Nin)/(Sout/Nout)
For a resistive element,
, where
T = atmosphere temperature (320.8K is the highest outside temperature in Iowa)
< Reference: http://www.netstate.com/states/geography/ia_geography.htmand www.ieee.li/pdf/viewgraphs_mohr_noise.pdf >
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Noise temperatures of each elements are measured by these equations. The cascading noise temperatures are caculated like below.
Results:
Stage 0
(Sky noise)Stage 1 (cable 1)
Stage 2 (Switch)
Stage 3 (Switch)
Stage 4 (LNA, 5V)
Stage 5 (switch)
Stage 6(cable 2)
Stage 7 (Radio)
Gain (dB) -2.8 -0.2 -0.2 21.1 -0.2 -5.8 Gain Ratio 0.52 0.95 0.95 128.6 0.95 0.3 NF(dB) 0.998 F 1.3 T (K) 320.8 320.8 320.8 320.8 320.8 Te (K) 700.0 290.6 15.1 15.1 74.9 15.1 898.8 4076.1 Cascading cal. 700.0 290.6 28.8 30.17 156.56 0.25 15.29 263.71
• Input Noise Temperature, Tsys: 1485.35 K
• Noise Power, PRL = kTsBn = 1.5E-16 [W] = -126.27 [dB]
Process calculations:
Note: The elements’ gains, losses, and noise figure came from manuals.
• Sky noise: 700 K
The 700K is the natural noise temperature from sky in case of the 500MHz signal. This value will be added with the system noise temperature to obtain the input noise temperature.
• Coax cable 1: 290.6 K
The coax cable from the satellite dish to the LNA box is RG-8, and its model number is Carol® C1166. According to its manual, the insertion loss is 10.17dB/100ft when it’s 400MHz signal.
Through some calculation, its loss is estimated to about 2.8dB/30ft at 440MHz.
<reference: http://www.generalcable.com/NR/rdonlyres/4F9763E4-0F09-426F-A58E-7A159BC7549E/0/Pg074_076_RG58U.pdf>
• Switches: 15.1 K
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⓪ ① ② ⑦⑤④③ ⑥
The switch we use has 0.2dB loss.
• LNA: 74.9 K
Its noise factor is 1.3, so we use the equation (A) to get the noise temperature. This is the only element which is not resistive.
• Coax cable 2: 898.8 K
This coax cable is RG-8, and its model number is Belden 9913. The length of this coax is about 200ft. We could find its manual by this information, and the manual says the insertion loss is about 5.8 dB/200ft.
Loss in Transmission cable vs. Frequency
• Radio: 4076.1 KThe radio’s sensitivity is 0.18μV, so its sensitivity power is 6.48E-16 W. By the sensitivity power and the transmitting signal’s bandwidth, we calculated its noise temperature with the equation, Ts=PRL/kBn.
- For our system, the noise temperature is applied in cascade, so we use the below equation to get the input noise temperature.
Therefore, the input noise temperature = Ta + Tsys, or cas =700K + 265.35K = 965.35 K
- Noise power is obatained by the equation below. This noise power is proportional to temperature and the bandwidth of the transmitting signal from the cubesat.
PRL = kTsBn [W],
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, where = Boltzmann Constant (1.381×10−23 J/K, joules per Kelvin) = noise temperature (K) = bandwidth (Hz) = 11,520Hz
(20% wider than the bandwidth of transmitting signal)
Therefore, the noise power = 2.4E-16 [W] = -126.27 [dBm]
Conclusion:
From the received power taken by link budget and the noise power just we got, we can get the signal-to-noise ratio by subtracting those two powers described in dB.
SNR = (Worst received power) – (System noise power)
= (-109.11dBm) – (-126.27 dBm) = 17.16 dB
This is greater than 10dB which we wanted to get as a SNR. Because the SNR is large, we expect that we can receive good quality signal from the cubesat.
• Power Gains and Losses in the LNA box
The power gains and losses in the LNA box are organized in the table below.
3. Power in the designed process (440MHz)Worst received power at the satellite dish -109.11 dBm
Coax Cable (Carol® C1166) -2.76 dB/30ft LNA (ZX60-33LN+) 21dB (Gain)Microwave Switch (ZX80-DR230+), 3units -2.1dB (Insertion Loss)SMA to SMA adapter (SM-SM50+), 4units -0.12dB (Insertion Loss)Coax Cable (Belden 9913 (RG-8)) -5.8dB/200ft (Insertion Loss)Radio Input Power -98.9 dBm
Power of Radio Sensitivity -121.9 dBm
Conclusion: Because the radio input power is much greater than the power of the radio sensitivity, the signal coming into radio can be decoded by the radio, or the radio can decode the transmitting signal from the cubesat.
Note: The power calculation without the LNA system has 8.67dB as its SNR, which does not meet the requirement.
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Appendix BCalculations for HABET Spring Test of Cube Satellite
Abstract:In the Spring, the CySat Club will be testing the capabilities of the cube satellite by
suspending it above the ground with a weather balloon. From a GPS unit suspended with the satellite, the team will receive GPS information, including longitude and latitude coordinates as well as elevation information. From this information, and similar information about the antenna dish at Fick University, we need to determine the elevation and azimuth angles of the dish so that it will point at the balloon.
Given Longitude Latitude ElevationPoint 1 (balloon) a b cPoint 2 (Antenna Dish) x y z
The analysis of this problem requires two parts. In the first, the longitude and latitude values are used to determine an angle theta, to be defined later, and in the second, this theta value is used to determine the elevation angle. Also, North and East values will be assigned positive angles and East and West values will be assigned negative angles.
Here are two alternate views of the angle theta, which is the angle between the two radii of the earth, one radius at pointing at the balloon, the other pointing at the antenna tower. Figure 2 is a spherical representation we will use to determine the azimuth angle. Notice that and are the compliments of x and a, and equal 90 degrees minus x or a, respectively.
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Figure 1 Figure 2
b-y
From figure 2 we can make a spherical triangle with sides , , and and an inner angle of the absolute value of b-y. Notice that the absolute value is needed only so that all inner angles are positive, and that the absolute value can eventually be removed. To solve for theta we can use the law of cosines for spherical triangles.
which equals:
given that cos(x) = cos(-x) and therefore cos(|b-y|) = cos(b-y) = cos(y-b). Using this law, we can solve for theta directly.
The azimuth angle is equal to the angle opposite , which we can call . To solve for , we can again use the law of cosines.
Notice that this calculation will return a value between 0 and 180 degrees, which will only be correct when y is greater than b. Otherwise, we will need the negative of the returned value.
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Figure 3Figure 2
b-y
In the next step, we slice a cross section of the earth along the two radii that make the angle .
Now at the end of each radii, we can add the elevation of the antenna tower, , and the elevation of the balloon, .
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Figure 2
Figure 4
Figure 4 shows the set-up for solving for the elevation angle . If we draw a perpendicular line from , it will eventually intersect the z line if the z line is long enough. The length of the z line that extends past the perpendicular line is p. The length of the perpendicular line to c from point c to the intersection point is length g. The derivation of is as follows.
Now that we have equations for p and g in terms of r, c, and , we can find our angle . Notice that due to parallel lines, appears in the right triangle with p.
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g
Figure 5
Figure 6
This is a complicated formula, but will indeed return the correct elevation angle for a given . These results are entered into an excel file so that the user can enter in two points with longitude, latitude, and elevation and receive the elevation and azimuth angle from point 1 to point 2.
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