Design, development, and verification of the Planck low frequency instrument 70 GHz front-end and back-end modules

70 GHz radiometer front-end and back-end modules for the Low Frequency Instrument of the European Space Agency's Planck Mission were built and tested. The operating principles and the design details of the mechanical structures are described along with the key InP MMIC low noise amplifiers and phase switches of the units. The units were tested in specially designed cryogenic vacuum chambers capable of producing the operating conditions required for Planck radiometers, specifically, a physical temperature of 20 K for the front-end modules, 300 K for the back-end modules and 4 K for the reference signal sources. Test results of the low noise amplifiers and phase switches, the front and back-end modules, and the combined results of both modules are discussed. At 70 GHz frequency, the system noise temperature of the front and back end is 28 K; the effective bandwidth 16 GHz, and the 1/f spectrum knee frequency is 38 mHz.The test results indicate state-of-the-art performance at 70 GHz frequency and fulfil the Planck performance requirements.