Post on 25-Dec-2021
Communication & Ground StationMasahiko YamazakiDepartment of Aerospace Engineering,College of Science and Technology, Nihon University, Japan
1. What is communication of satellite? What is purpose of communication? What should we consider in developing? Design example of satellite communication.
2. What is communication of CanSat ? What is purpose of communication? Basics of satellite communication
(Protocol, Modulation) Design example of communication system of CanSat
3. Summary
2
I think the purpose of communication subsystem is
I think the purpose of ground station is To communicate with a satellite,
To track satellite: Tracking To receive house keeping and Mission data: Downlink To transmit commands to satellite: Uplink
What is satellite communication?
To communicate with a ground station, To transmit house keeping and Mission data: Downlink To receive commands from a ground station: Receive a command
3
I think the purpose of communication subsystem is To communicate with a ground station,
To transmit house keeping and Mission data: Downlink To receive commands from a ground station: Receive a command
I think the purpose of ground station is To communicate with a satellite,
To track satellite: Tracking To receive house keeping and Mission data: Downlink To transmit commands to satellite: Uplink
The primary goal of the communication subsystem is to provide a linkto relay data findings and send commands to and from the satellite.Communication subsystem will ensure continuous communicationbetween the ground station and the satellite after ejection from therocket.
What is satellite communication? 4 What is satellite communication?Example: Sequence of satellite communication
Ground station Satellite
TrackingOrbit predictionAntenna direction control
Condition confirmation
TransmitHouse keeping data
(Downlink)
Downlink data analysis
Transmit command(Uplink)
ReceiveCommand
(Return response)
TransmitMission data(Downlink)
Mission data collection
House keeping data(Downlink)
Start/AOS
End/LOS
Change satellite mode automatically
Ground station Satellite
TrackingOrbit predictionAntenna direction control
Condition confirmation
TransmitHouse keeping data
(Downlink)
Downlink data analysis
Transmit command(Uplink)
ReceiveCommand
(Return response)
TransmitMission data(Downlink)
Mission data collection
House keeping data(Downlink)
Start/AOS
End/LOS
Change satellite mode automatically
5
Example: Sequence of satellite communication
<CW(Morse)>Low power consumption
<FM packet>High speed data transmission
<FM packet>
Battery voltage, Power generation amount, etc…
Camera data, etc…
What is satellite communication? 6
Satellite communication subsystem Task of communication subsystem(HK data & Mission data downlink)
Data is collected by the sensors and payload. The microcontrollerwill accumulates data from the sensors and convert these inputsinto a stream of 8‐bit binary numbers.
This numerical string is encoded into some protocol(for exampleAX. 25 for amateur radio use), by MPU, modulated by modem,and transmitted to GS by transmitter through the antenna.
What is satellite communication?
7
Satellite communication subsystem Task of communication subsystem(Receive a command)
From the ground, moderators are able to send commands to thesatellite by uplink software. The command is encoded into someprotocol(for example AX. 25 for amateur radio use), modulated bymodem, and transmitted to satellite by transmitter of GS throughthe antenna.
Command is received by receiver, demodulated by modem anddecoded by MPU.
What is satellite communication? 8
Example: CubeSat communication subsystem(SEEDS)What is satellite communication?
9
Example: CubeSat communication subsystem(SEEDS)
FM receiverFrequency: 144MHzModulation: FMProtocol: AX. 25Bitrate: 1200bps
CW/FM transmitterFrequency: 430MHzModulation: CW/FMProtocol: Morse/AX.25Bitrate: 10 wpm/1200bps
What is satellite communication? 10
Satellite ground station Task of ground station: Satellite tracking, House keeping data and
Mission data downlink, Command uplink It consists of uplink‐downlink antenna, TNC(terminal node
controller), transmitter, receiver, tracking and antenna controlsoftware, uplink software and downlink software.
What is satellite communication?
11
Satellite ground station Task of ground station: Satellite tracking, House keeping data and
Mission data downlink, Command uplink It consists of uplink‐downlink antenna, TNC(terminal node
controller), transmitter, receiver, tracking and antenna controlsoftware, uplink software and downlink software.
Overview of ground stationAntenna control
What is satellite communication?
IC-910D
IC-910D
TNC-555
TNC-555
12
Example: Command uplink and Data downlink software
Command list
Transmit button
Raw data(hex number)House keeping data
(decimal number)Voltage, thermal, power generation, etc..
What is satellite communication?
13
Example: Satellite tracking software SGP4
Very simple and relatively precise You can calculate future position of your satellite by using TLE
(two line element) given out by NORAD. 1 3 2 7 9 1 U 0 8 0 2 1 J 1 1 2 7 3 . 4 0 5 0 9 8 8 8 . 0 0 0 0 2 4 7 0 0 0 0 0 0 - 0 3 1 4 7 9 - 3 0 9 8 9
2 3 2 7 9 1 9 7 . 8 3 8 6 3 3 5 . 1 1 7 6 0 0 1 5 5 0 2 1 8 9 . 1 4 1 0 1 7 0 . 9 5 3 2 1 4 . 8 2 3 2 5 1 2 1 1 8 5 0 9 7
Map with predicted trajectory
Two line element
3D visualization of an antenna
Orbit data
What is satellite communication? 14
Example: Satellite operation(CubeSat@Low earth orbit) Access time max. from ground station: 10 minutes or so. Access chance max. from ground station: 6 times/day or so. Access length max. from ground station: 2000km or so.
You should construct operation plan beforehand. You should consider transmission rate and
transmission power.
What is satellite communication?
Confirmsatellite condition
Mission or Mission data downlink
AOS(Acquisition of satellite)
Command uplink
10 m
inut
e 1-3
min
ute
6 m
inut
e
1 m
inut
e
15
Transmission from ground station to satellite(Visible area) Enough power to send the data to GS within the visible time. In case of Sun‐synchronous orbit, the net communication time is only
about 1 hour per day. You should forecast the visible time by using the orbit analysis result
and make the mission plan. If , the satellite is visible.sins zG s ELq⋅ >r e r
Earth
O
GS
GzVisible
eR
GH
zGe
sr
ELq
What is satellite communication? 16
Example: Link budget(Transmission power) A link budget is the accounting of all of the gains and losses from the
transmitter, through the medium (free space, cable, waveguide, fiber,etc.) to the receiver in a telecommunication system.
Satellite AntennaModulation MethodOrbit Altitude [km] 635Maximun Transmission Distance D[km] 2012Elevation Angle [deg] 10Satellite Transmitter Power Pt[mW] 400Satellite transmission Frequency f[MHz] 437.485Transmission wavelength [m] 0.686Transmitter Electic Supply Loss Lt[dB] -2Transmission Antenna Gain Gt[dB] -2Effective Isotropically Radiated Power(EIRP) PE[dBW] -7.98Free Space Loss Ld[dB] -151Polarized Wave Loss LP[dB] -3Air Absorption Loss LA[dB] 0Rainfall Loss LRA[dB] 0Transmission Loss Lv[dB] -154
AFSK
Downlink(FM)Mono Pole Antenna Ground Station Antenna
Ground Station Pointing Loss Lp[dB] 0Ground Statin Antenna Gain Gr[dBi] 18.5
Lr[dB] -2Lr[-] 1.58
Antenna Receive Noise/Temperature Ta[K] 300Station Ambient Noise/Temperature Te[K] 300Ground Station Temperature TG[K] 300
NF[-] 2NF[dB] 1.58
Maximun Signal Pass Bandwidth B[kHz] 5Boltzmann Constant K[J/K] 1.38E-23Ground Station System Noise Temperature Tsys[dB] 28.5Receiving Gain G[dB] 16.5Receive G/T G/T[dB] -12.0Demodulation Loss Lb[dB] -6Internal Ground Station Transmission Loss Lg[dB] -1Ground Station Processing Loss L0[dB] -7Ground Station Received Signal Power C[dB] -146Noise Power Spectral Density N0[dB] -200Noise Power N[dB] -177Received Power/Noised Power Ratio C/N0[dB] 54.3Receiver Signal/Noise Power Ratio S/N0[dB] 47.3
Cross Yagi Antenna 2 Stack
Station Receiver Electric Supply Loss
Noise Figure
Ground Station
g 0[ ]Request Bit Frequency Error Pb 0.000001Request Eb/N0 Eb/N0[dB] 10.5Computed Statellite transmission Bps [bps] 1200Request C/N0 C/N0req[dB] 48.3Down Link Margin M[dB] 5.98
What is satellite communication?
17
Example: Link budget(Transmission power) Carrier power to Noise ratio should be enough large
Output power decays until the radio wave reaches to the receiver in ground station.
Free space loss and other loss
System noise in GS. Feeding
What is satellite communication? 18
Example: Link budget(Transmission power) Carrier power to Noise ratio should be enough large
Free space loss is larger if the frequency is larger.
Free space loss and other loss
10
420 logd
fdL
c
æ ö÷ç ÷= - ç ÷ç ÷çè ø
Earth
O
ELqd
e GR H+eR H+
vq
( )coscos
( )sin
cos
e G ELv EL
e
e v
EL
R H
R HR H
d
qq q
q
q
é ù+ê ú= -ê ú+ê úë û+
=
What is satellite communication?
In satellite communications, free‐space loss is the major losssuffered by signals in travelling over the Earth‐satellite path.The loss is inversely proportional to the square of thedistance travelled and inversely proportional to the squareof the frequency used.
19
Example: Link budget(Transmission power) Carrier power to Noise ratio should be enough large
System noise is estimated by temperature
System noise in GS. Feeding
** *AF E* *
FRX FRX
110 log 1s
TT T T
L L
é ùæ ö÷çê ú÷ç= + - +÷ê úç ÷ç ÷ê ú÷çè øë û
What is satellite communication? 20
Example: Link budget(Transmission power) A link budget is the accounting of all of the gains and losses from the
transmitter, through the medium (free space, cable, waveguide, fiber,etc.) to the receiver in a telecommunication system.
Satellite AntennaModulation MethodOrbit Altitude [km] 635Maximun Transmission Distance D[km] 2012Elevation Angle [deg] 10Satellite Transmitter Power Pt[mW] 400Satellite transmission Frequency f[MHz] 437.485Transmission wavelength [m] 0.686Transmitter Electic Supply Loss Lt[dB] -2Transmission Antenna Gain Gt[dB] -2Effective Isotropically Radiated Power(EIRP) PE[dBW] -7.98Free Space Loss Ld[dB] -151Polarized Wave Loss LP[dB] -3Air Absorption Loss LA[dB] 0Rainfall Loss LRA[dB] 0Transmission Loss Lv[dB] -154
AFSK
Downlink(FM)Mono Pole Antenna Ground Station Antenna
Ground Station Pointing Loss Lp[dB] 0Ground Statin Antenna Gain Gr[dBi] 18.5
Lr[dB] -2Lr[-] 1.58
Antenna Receive Noise/Temperature Ta[K] 300Station Ambient Noise/Temperature Te[K] 300Ground Station Temperature TG[K] 300
NF[-] 2NF[dB] 1.58
Maximun Signal Pass Bandwidth B[kHz] 5Boltzmann Constant K[J/K] 1.38E-23Ground Station System Noise Temperature Tsys[dB] 28.5Receiving Gain G[dB] 16.5Receive G/T G/T[dB] -12.0Demodulation Loss Lb[dB] -6Internal Ground Station Transmission Loss Lg[dB] -1Ground Station Processing Loss L0[dB] -7Ground Station Received Signal Power C[dB] -146Noise Power Spectral Density N0[dB] -200Noise Power N[dB] -177Received Power/Noised Power Ratio C/N0[dB] 54.3Receiver Signal/Noise Power Ratio S/N0[dB] 47.3
Cross Yagi Antenna 2 Stack
Station Receiver Electric Supply Loss
Noise Figure
Ground Station
g 0[ ]Request Bit Frequency Error Pb 0.000001Request Eb/N0 Eb/N0[dB] 10.5Computed Statellite transmission Bps [bps] 1200Request C/N0 C/N0req[dB] 48.3Down Link Margin M[dB] 5.98
What is satellite communication?
21
Example: Antenna Mono‐pole or Di‐pole is suitable for CubeSat.
Transmitting antenna
Receiving antenna
The satellite structure is the ground
What is satellite communication? 22
Example: Antenna testing Antenna pattern
Refers to the directional (angular) dependence of the strength of theradio waves.
Impedance matching Impedance matching is the practice of designing the input impedance
of an electrical load to minimize reflections from the load. Impedance matching is quite important.
SEEDS-I: 207mmSEEDS-II: 215mm (theory:172mm)
What is satellite communication?
CanSat?
24 Purpose of communication
To communicate with a ground station, To receive commands from a ground station: Receive a command To transmit house keeping and Mission data: Downlink
I think purpose of ground station of CanSat is To communicate with a satellite,
To track CanSat: Tracking(by hand) To receive house keeping and Mission data: Downlink To transmit commands to CanSat: Uplink
I think purpose of communication subsystem of CanSat is
25 Purpose of communication
To communicate with a ground station, To receive commands from a ground station: Receive a command To transmit house keeping and Mission data: Downlink
I think purpose of ground station of CanSat is To communicate with a satellite,
To track CanSat: Tracking(by hand) To receive house keeping and Mission data: Downlink To transmit commands to CanSat: Uplink
I think purpose of communication subsystem of CanSat is
The primary goal of the communication subsystem is to provide a linkto relay data findings and send commands to and from the CanSat.Communication subsystem will ensure continuous communicationbetween the ground station and the CanSat after ejection from therocket or Balloon.
26 Purpose of communicationCanSat: Differences from Satellites(about communication) I think the main difference from satellite about communication is distance
between satellite and ground station. CanSat: ground to air(100m ~ 4000m), Satellite: ground to space(2000km)
System architecture is same Transmitter, Receiver, Transmitting and Receiving antenna, Modem,
Encode/Decode equipments.
Communication
Receiver Transmitter
Sensor
S1 S2 Sn
voltage, temperature, current, gps sensor
Command & Data handling
Actuator
MotorNichrome wire
Mission Subsystem
SensorExperimental system
Camera etc.
Electrical power supply
Battery
OBC Memory
Uplink Downlink
Structure
27 Purpose of communicationExample: CanSat communication subsystem Task of communication subsystem(HK data & Mission data downlink)
Data is collected by the sensors and payload. The microcontrollerwill accumulates data from the sensors and convert these inputsinto a stream of 8‐bit binary numbers.
This numerical string is encoded into some protocol by MPU,modulated by modem, and transmitted to GS by transmitterthrough the antenna.
28 Purpose of communicationExample: CanSat communication subsystem Task of communication subsystem(Receive a command)
From the ground, moderators are able to send commands to theCanSat by uplink software. The command is encoded into someprotocol, modulated by modem, and transmitted to CanSat bytransmitter of GS through the antenna.
Command is received by receiver, demodulated by modem anddecoded by MPU.
29 Basics of communicationCommunication using radio wave CanSat communication systems convey information using
electromagnetic waves , which is commonly referred to as a "carrier“. The carrier itself does not convey any information(data). Information is
conveyed by modifying one or more attributes of the carrier. Data(information) is encoded into some protocol after that,
modulated by modem(make analog signal). Transmitted by transmitter through antenna(increase radio signal).
30 Basics of communicationCommunication using radio wave(Protocol) The processor collects the data from the satellite computer and
generates an some protocol data stream. A protocol is basically a method of formatting information and a
communication method. A data structure is used that containsinformation for addressing a receiver, identifying the transmitter,identifying the type of data, and error checking and correction.Example
31 Basics of communicationCommunication using radio wave(AX. 25 protocol) The most common protocol for CubeSat is AX.25, which was originally
developed for amateur radio use. For the transmission to be efficient,reliable, and robust.
It is widely used in the amateur radio community for sending weatherreports, position coordinates and other short sets of data.
Detect start of message
Identify the source, address and type of protocol
Error checking
Detect end of message
32 Basics of communicationCommunication using radio wave(protocol & modulation) Data is encoded into some protocol, after that,modulated by modem. The simplest method is Morse code. A radio signal is turned on and off
at certain times to generate a pattern that conveys information. Morsecode uses short and long radio pulses.
More complicated communications use various modulationtechniques. Most have heard of AM and FM radio. AM radiomodulates a radio signal by adjusting the amplitude of the radio signal.FM radio modulates by shifting the frequency of the radio signal.
33
Example: Modulation
Mounting dataModulation/keying
Data is encoded (based on some protocol) by MPU, modulated by modem,and transmitted to GS by transmitter.
Command is received by receiver, demodulated by modem and decodedby MPU.
Picking up dataDemodulation
Carrier wave
Carrier wave
Basics of communication 34
AM: Amplitude modulation, FM: Frequency modulation
Carrier wave
AM(ASK):modulating by amplitudeModulating of information in a carrier wave by varying the strength of the wave.
FM(FSK):modulating by frequencyModulating of information in a carrier wave by varying the instantaneous frequency of the wave.
「に」→
「く」→
「にく」→
“o” →
“n” →
“on” →
「に」→
「く」→
「にく」→ “o” →
“n” →
“on” →
Basics of communication
35
Example: Frequency modulation of digital data Modulation/Demodulation
Modulation in general sense is themixing of two signals.
In the communication systemmodulation is the process of varyingsome characteristics of carrier wave(Amplitude, phase or frequency) withrespect to the modulating wave (messagesignal).
Basics of communication
1 0 1 10
1 0 1 10
TransmitterModemMPU(encode)
Transmitting antennaReceiving antenna
MPU(decode)Receiver Modem
Demodulation ModulationDigital data Analog dataAnalog data Digital data
36
CW: Morse Data size is small but it is resistant to noise. SEEDS transmits CW which include important HK data.
FM(AFSK): AX.25 protocol 1200bps (slow communication) It can transmit a certain amount of data and its bandwidth is
narrow. Therefore, it is suitable for simple modulation.
FM(GMSK): AX.25 protocol SPROUT uses 9600bps GMSK transmitter for large amount of data
such as camera image data. It is relatively weak for the noise because it contains Gaussian
filter to avoid large bandwidth.
Basics of communication
37 Basics of communicationCommunication using radio wave(radio law) CanSat must comply radio law. Amateur radio law
Long range but low data rate. Requires license. License is international.
Special low power devices Specially allowed regulation without
license in domestic law. Some imported devices are not allowed
to use in Japan. Please check radio law in your country!
DJ‐C7©Alinco
Xbee©Digi international Inc.
38 Design example of communicationIdentify requirements:The mission sequence should be imaged well, discussed, and should beshared well in the team.
During selection/assembly/integration/test process, you should checkthe availability, usability, interactions between other subsystems.
39
Example: Mission sequence
Separation
Autonomous Flight
Launch Ground stationObjective point
Downlink
Uplink
Design example of communication 40
Example: Mission sequence
Separation
Autonomous Flight
Launch Ground stationObjective point
Downlink
Uplink
Communication – Structure, distance from ground station, datasize, flight time = signal power, bit rate, packet size, etc.
Design example of communication
41 Design example of communication
Identify requirements
Components selection
Assembly/Integration
Test
Meet requirements?
AvailabilityUsability
Interactions between subsystems, etc.
Distance from ground station,Data size, flight time
Transmitter, Receiver, TNC, Antenna, Frequency, Bit rate, Modulation, Protocol, Ground station design, Link analysis
No
Yes
Design finished
42
If you want to use amateur radio frequency You have to make a lot of components.
Example: Amateur radio communication for CanSat
Modem(FX614)
MPU(PIC)
Transmitter/Receiver (DJC7)
TransmitterModemMPU(encode)
Transmitting antennaReceiving antenna
MPU(decode)Receiver Modem
Demodulation ModulationDigital data Analog dataAnalog data Digital data
Design example of communication
43
Example: Handy GS for amateur radio communication It consists of uplink‐downlink antenna, TNC(terminal node controller),
transmitter, receiver, tracking and antenna control software, uplinksoftware and downlink software.
Design example of communication 44
Xbee(©Digi international Inc.) is all in one component for radiocommunication.
Example: CanSat communication subsystem using Xbee
RF data rate 250 KbpsMaximum range 1.5kmTransmitting power 10mWFrequency 2.4GHzInterface 3.3V UART
TransmitterModemMPU(encode)
Transmitting antennaReceiving antenna
MPU(decode)Receiver Modem
Demodulation ModulationDigital data Analog dataAnalog data Digital data
Xbee
Design example of communication
45
Example: CanSat handy ground station It consists of uplink‐downlink antenna, TNC(terminal node controller),
transmitter, receiver, tracking and antenna control software, uplinksoftware and downlink software.
Design example of communication 46
Example: CanSat ground station software Very quick recognition of CanSat condition.
Design example of communication
Summary
I think, The primary goal of the communication subsystem is to provide a
link to relay data findings and send commands to and from theCanSat.
The mission sequence should be imaged well, discussed, and shouldbe shared well in the team. Identify the requirements, select/assembly/integration/test.
To verify RF communication by measuring the decode ratio.
In this lecture, I talked about Purpose of radio frequency communication and ground station Design example of satellite and CanSat RF communication.
800m