Communication Ground Station

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.


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.


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


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.


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


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..


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


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.


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


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


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



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+

=


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


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


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


21

Example: Antenna Mono‐pole or Di‐pole is suitable for CubeSat.

Transmitting antenna

Receiving antenna

The satellite structure is the ground


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)


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).


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.


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)






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.


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





Xbee


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.


Example: CanSat ground station software Very quick recognition of CanSat condition.


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

Communication Ground Station

Documents

Transcript of Communication Ground Station