Introduction to Space Systems and Spacecraft Design Space Systems Design Communications - Antennas Ref: SMAD Sections – 13 Communications Architecture

Introduction to Space Systems and Spacecraft Design University of Idaho 2 Communications I How do these antennas work? RF – radio frequency

Introduction to Space Systems and Spacecraft Design Space Systems Design 3 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 4 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 5 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 6 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 7 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 8 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 9 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 10 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 11 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 12 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 13 Communications - Antennas Ground Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 14 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 15 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 16 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 17 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 18 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 19 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 20 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 21 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 22 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 23 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 24 Communications - Antennas Spacecraft Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 25 Communications - Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 26 Communications - Antennas W = Power Density – W/M 2 S = distance from antenna to a point in space La = atmospheric loss EIRP = effective isotropic radiated power

Introduction to Space Systems and Spacecraft Design Space Systems Design 27 Communications - Antennas Antenna gain for a parabolic antenna

Introduction to Space Systems and Spacecraft Design Space Systems Design 28 Communications - Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 29 Communications - Antennas ( ) 2

Introduction to Space Systems and Spacecraft Design Space Systems Design 30 Communications - Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 31 Communications - Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 32 Communications - Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 33 Communications - Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 34 Communications - Antennas

Introduction to Space Systems and Spacecraft Design Space Systems Design 35 Communications - Antennas What is the affect on the gain of antennas with frequency? When perfect impedance match – get 100% transfer to antenna 100% Perfect impedance match – get VSWR = 1.0

Introduction to Space Systems and Spacecraft Design Space Systems Design 36 Communications - Antennas What is the affect on the gain of antennas with frequency? What happens when VSWR > 1.0? <100% forward wave Output power of antenna (gain) is less off resonant frequency. Reflected wave

Introduction to Space Systems and Spacecraft Design Space Systems Design 37 Communications - Antennas What is the affect on the gain of antennas with frequency? The gain on all antennas are frequency sensitive.

Introduction to Space Systems and Spacecraft Design Space Systems Design 38 Communications - Antennas ¼ wavelength antenna above a ground plane Center fed ½ wavelength ~ ~ Antenna Polarization

Introduction to Space Systems and Spacecraft Design Space Systems Design 39 Communications - Antennas Electric field lines from a ½ wave antenna Generated vertical electric field lines Vertically polarized antenna Antenna Polarization Ground (B) (A) (C)

Introduction to Space Systems and Spacecraft Design Space Systems Design 40 Communications - Antennas (C) Electric field lines from a ½ wave antenna Horizontal electric field lines Horizontal polarized antenna (A) (B) Antenna Polarization Ground

41 Communications - Antennas Antenna Polarization Circular Polarization Helical Antenna Spiraling electric field Introduction to Space Systems and Spacecraft Design Space Systems Design

Introduction to Space Systems and Spacecraft Design Space Systems Design 42 Communications - Antennas Antenna Polarization Circular Polarized Helical Antenna Rotating electric field Counter clockwise rotating Looking to forward end of antenna LHP – left hand polarization Clockwise rotating Looking to forward end of antenna RHP – left hand polarization

Introduction to Space Systems and Spacecraft Design Space Systems Design 43 Communications - Antennas Antenna Polarization Polarized Antenna Coupling

Introduction to Space Systems and Spacecraft Design Space Systems Design 44 Communications - Antennas Antenna Polarization What type of antenna polarization should be used on satellites and ground stations? V polarization? H polarization? LH circular? RH circular? V polarization? H polarization? LH circular? RH circular? What about when satellite is coming toward you? What about when satellite is going away from you?

Introduction to Space Systems and Spacecraft Design Space Systems Design 45 Communications - Antennas Antenna Polarization Didn’t answer the question of polarization on the ground and on the satellite??? Something tricky happens to the polarization as the RF passes through the atmosphere to and from the satellite. We will find out when we look further at the link equations.

Introduction to Space Systems and Spacecraft Design Space Systems Design 46 Communications - Antennas Questions?