dino – peer review 4 december 2015 dino communication system peer review zach allen chris page

DINO – Peer Review April 18, 2023

DINO Communication

System Peer Review

Zach Allen

Chris Page

Colorado Space Grant Consortium 2


Purpose

• Establish two-way communication link between satellite and ground station.– Link must allow transfer of map files from

satellite to ground.– Must allow transmission of health and status

data from satellite to ground.– Must allow the satellite radios and flight

computer to receive command lines transmitted by ground station.



Requirements Imposed by other Subsystems

• Data Rate: must be high enough to accommodate all data– 20 kbytes per topographical map– 255 bytes per Health and Status Packet– 5 kbytes per uploaded schedule

• Antennas– Must be deployable by structures– No deployable ground plane allowed



Requirements on Power

– Transmitter (Radio1)• Transmit mode: 12 V at 1.4 A (16.8 W)• Idle mode: 12 V at 90 mA (450 mW)• Must have capability to be activated/deactivated by flight

computer.

– Receiver (Radio2)• 5 V at 90 mA (450 mW)

• Must be active concurrently with flight computer

– External TNC (tentative): 12 V at 200 mA (2.4 W)• Must always be active when flight computer is active



Requirements on C+DH

• Two RS-232 Serial Ports– 1 serial port dedicated to external TNC

• 9600 baud, 8 data bits, no parity bit, 1 stop bit• Must have hardware flow control (CTS, RTS)

– 1 serial port shared between radio1 and radio2• Must be able to switch at any time between the two radios• 9600 baud, 8 data bits, no parity bit, 1 stop bit• Software flow control only



Requirements on Software

• Set up Radio1 (Transmitter) Parameters– Switch the shared serial port to Radio1 immediately

after Radio1 is powered on (every time!)– Must program the following parameters into Radio1:

• Transmit frequency (TBD, after FCC assigns the frequency)• Transmit power (5 Watts)



Requirements on Software, Continued

• Set up Radio2 (Receiver) Parameters– Switch the shared serial port to Radio2 immediately

after Radio2 is powered on (every time!)– Must program the following parameters into Radio2:

• Receive frequency (TBD, after FCC assigns the frequency)• Squelch



Requirements on Structures

• Mass– Two Transceivers

– 170 grams each

– 2 x 170 grams = 340 grams total

– External TNC– Still determining. Upper limit is 40g.

– Bent Dipole Antenna (transmit antenna)– Duck Antenna (receive antenna)– Approximately 2 feet of coax to feed the antennas



Requirements on Structures, Continued

• Dimensions– Two Transceivers

– 4.9 x 2.3 x 1.2 inches each

– Mounted together in one 3CS-sized box (7.25 x 4.75 x 1 inch)

– External TNC– Model still being determined

– Upper Limit 6.1 x 7.3 x 1.3 inch

– Box arrangements TBD

– Antennas– Deploy Bent Dipole

– Deploy Duck Antenna



Subsystem Block Diagram

• All Data lines use RS-232 Serial

• Transmitter operates at 12 V

• Receiver operates at 5 V.• External TNC: 12 V line,

allows 9,600 bps link to ground.

• Internal TNC proven to be reliable at 1,200 bps.

12 V line voltage1.4 A16.8 W transmitting(450 mW idle)

5 V line voltage90 mA450 mW(constant)

12 V line voltage400 mA, 4.8 W(constant)

RS-232 Serial9,600 bps(during setup only)

RS-232 Serial9,600 bps(during setup only)

RS-232 Serial9,600 bps(constant)

Radio1Transmitter

Kenwood TH-D7

Radio2Receiver

Kenwood TH-D7

External Terminal Node Controller(TNC)

InternalTNC

InternalTNC

Antenna

Power LineData Line

Legend

Antenna



Design

• Transceivers– Two Kenwood TH-D7 radios

• Radio1: Downlink, approximately 436 MHz

• Radio2: Uplink, approximately 145 MHz

• TNC still under consideration– Timewave PK-96

• Requires removing many electrolytic capacitors

– Kantronics KPC 9612+• Requires removing many electrolytic caps

– Paccomm UP-9600• Already surface mount

• Heritage with Citizen Explorer Mission



Analysis: Power Requirements

• Daytime Operation– Receiver: 0.45 W (5 V, 90 mA) always.– TNC: 2.4 W (12 V, 200 mA) always.– Transmitter: 16.8 W (12 V, 1.4 A) for approx. 8 minutes,

otherwise same as Receiver (0.45 W).

• Nighttime Operation– Receiver: 0.45 W (5 V, 90 mA) always.– TNC: 2.4 W (12 V, 200 mA) always.– Transmitter: 16.8 W (12 V, 1.4 A) for approx. 4 seconds,

otherwise same as Receiver (0.45 W).

• Safe Mode– Same as nighttime.



Analysis: Calculating Transmission Time

• We need to find the transmission time in order to find the exact power requirements over the course of one day.

• Time needed to send one packet:– 10 bits/byte * 256 bytes/packet 1200 bits/sec =

2.133 sec/packet• Total transmission time (assuming 25 kB per pass during

daytime):– 2.133 sec/packet * 25 kB/pass

256 bytes/packet = 208.3 sec/pass = ~ 3.5 minutes (absolute minimum)

– May be approx. twice the minimum (resending, errors, etc.)

– This is a realizable amount of time.



Antenna/Structure Considerations

• Fit on nadir plate without obstructing cameras• Little room for placement inside satellite• Deployment of antenna• Antenna Structure

– Cost– Weight– Material (no outgasing)



Antenna Considerations

• Noise Factor and Loss• Maximum transmission distance• Radiation Pattern

– Gain– Beam width– Efficiency

• Link Budget– Carrier – to – Noise Ratio– Energy per bit – to – Noise Ratio (Available to Required)– Margin



Noise Factor and Loss

• The receivers will determine the noise factor based on criteria like– Bandwidth– Sensitivity

• Losses– Free space loss– Polarization loss– Pointing, component, and implementation losses– Atmospheric loss



Maximum Transmission Distance Calculations

• Low orbit height from earth = 425km

• Maximum distance from base station antenna (horizon) = (with =5o , slant angle) 1.84x106m– For =10o 1.39x106m– For =15o 0.99x106m

• These distances play into our free space loss and ultimately our link budget

Diagram Reference:Vincent L. Pisacane and Robert C.

Moore, Eds., Fundamentals of Space Systems. New York: Oxford University Press, 1994.



Up-link (Rubber Duck Antenna)

• Targeted Frequency of 145 MHz– Wavelength of approx. 2.1m

• Why chosen?– Ability to transmit high power and gain from base station– Heritage

• Antenna Radiation Patterns– Gain– Beam Width

• Link Budget



Up-Link (Rubber Duck Antenna): Radiation Patterns

• Gain– To be on the safe side, gain was projected to be 0dB

• Beam Width– Minimal beam width expected.



Up-Link (Rubber Duck Antenna): Link Budget

Forward 145 MHz Link UnitsTransmitter (Tx)

1 Tx Power, Pt 43.9 dBm2 Tx Component Line Losses, Ltl 3.0 dB 3 Tx Antenna Gain (Peak), Gt 15.0 dBi4 Tx Pointing Loss, Ltp 1.0 dB5 Tx Radome Loss, Ltr 0.0 dB

6 EIRP (1-2+3-4-5) 54.9 dBm

PropagationTransmission Frequency, f 145.0 MHzLink Range, R 1700.0 kmPropagation Factor, n 1.0

7 Free Space Loss, Ls 140.3 dB8 Atmospheric Absorption, Lpa 0.0 dB9 Precipitation Absorption, Lpp 0.0 dB

10 Total Propagation Loss (7+8+9) 140.3 dB

Receiver (Rx)11 Rx Antenna Gain (Peak), Gr 0.0 dBi12 Rx Polarization Loss, Lrpol 3.0 dB13 Rx Pointing Loss, Lrp 0.0 dB14 Rx Radome Loss, Lrr 0.0 dB15 Rx Component Line Losses, Lrl 1.0 dB16 Rx Implementation Losses, Lri 1.0 dB

17 Received effective carrier power -90.4 dBm(6-10+11-12-13-14-15-16)

Noise18 Standard Thermal Noise, kT -174.0 dBm/Hz19 Rx Noise Bandwidth, W 44.8 dBHz20 Rx Noise Figure, NF -1.3 dB

21 Effective Noise Power (18+19+20) -130.4 dBm

Result22 Available CNR (17-21) 40.1 dB23 Data Rate 39.8 dBHz24 Available Eb/No (22+19-23) 45.0 dB25 Implementation Losses 3.0 dB26 Required Eb/No 14.2 dB25 Margin (24-25-26) 27.8 dB

Link Budget Form courtesy of Dr. Stephen Horan, New Mexico State University.



Down Link

• Targeted Frequency of 436 MHz– Wavelength of approx. 0.7m

• Primary consideration– Bent Dipole

• Helix design still in simulation• Next consideration is phased, 4 element

antenna array



Down-Link (Bent Dipole Antenna)

• Antenna Radiation Patterns– Gain– Beam Width

• Link Budget• Simulations (NEC)

– Design– Radiation Pattern– 3D view of Radiation Pattern



Down-Link (Bent Dipole Antenna): Radiation Patterns

• Gain– 6.58 dB (NEC Simulation 12-8)

• Transmitted Power– 36.9 dBm (5W)

• Beam Width– 120o

– Filled requirement of 90o



Down-Link (Bent Dipole Antenna): Link Budget

Link Budget Form courtesy of Dr. Stephen Horan, New Mexico State University.



Down-Link (Bent Dipole Antenna): Simulation Design



Down-Link (Bent Dipole Antenna): Simulation Radiation Pattern



Down-Link (Bent Dipole Antenna): 3D View of Radiation Pattern

6.58

0.286

-14



Antenna Deployment

Before Deployment

After Deployment

Note: placement of monopole will need to be simulated and tested for best results

BentDipole Monopole



Commands – After Antenna Deployment

Radio2 power activated Software switches serial port to Radio2

Software programs Radio2

Radio1 power activated Software switches serial port to Radio1

Software programs Radio1

TNC power activated

12 3

4

56

7

System Ready



Antenna Test Plan

• Testing to be done either at Ball Aerospace or CU Antenna Lab– Test for resonant frequency

• By measuring reflection S parameters

– Antenna Radiation Pattern Measurements• Gain• Beam width• Efficiency

– Power transmitted to power received

– Transfer files to and from spacecraft CDH system



Radio/TNC Test Plan

• Incremental Testing is important to track bugs– Test TNC on bench first, connected directly to another TNC– Connect TNC to flight radios. Make transmissions of ASCII

character strings. Verify proper operation.– Test to make sure that received packets get properly decoded

and sent out of TNC serial port.– Install Radios and flight antenna prototypes into metal DINO

model– Connect a computer running the flight software to the TNC in the

DINO model– Attempt communication link between ground station and DINO

flight model.



Parts list and Cost

• Rubber duck– Bought through distributor – Cost of between $20-$50

• Bent dipole– Metal selections considered

• Copper: ~0.68 pounds• Aluminum: ~0.2 pounds

– Estimated cost of $30 for each prototype• All design and manufacturing will be done by Space Grant



Parts List and Cost

• Transmitter (Radio1): $360.00• Receiver (Radio2): $360.00• External TNC

• Initial cost: $595.00• Custom Firmware: $80



Issues and Concerns

• Link Budget Issues– Need to verify noise figure and thermal noise for link

budgets.– Need to verify link range

• Bent Dipole Issues– Gain and beam width only simulated, prototype must

be built and tested.– What will be the margin of error between angle

needed to angle achieved when deployed



Issues and Concerns

• External 9600 baud TNC interface still in question– Fall-back is 1200 baud

dino – peer review 4 december 2015 dino communication system peer review zach allen chris page

Documents

dino peer review

active slide

duck antenna slide

watts slide

frequency squelch slide

antenna duck antenna

shared serial port

radio1 transmitter parameters