The invention provides a 340GHz eighth
harmonic mixer. The 340GHz eighth
harmonic mixer comprises a radio-frequency input
waveguide, a radio-frequency
waveguide-suspended
microstrip transition structure, a
diode, a radio-frequency suppressing low-pass filter, a suspended
microstrip-
microstrip interconnecting structure, an intermediate-frequency filter, a
local oscillator waveguide-microstrip transition structure and a
local oscillator input waveguide; a radio-frequency
signal is input from the radio-frequency input waveguide and coupled and fed into the
diode via the radio-frequency waveguide-suspended microstrip transition structure; the intermediate-frequency filter, the
local oscillator waveguide-microstrip transition structure and the local oscillator input waveguide are combined to form a local oscillator-intermediate-frequency
duplexer; a local oscillator is fed into the
diode after orderly passing through the
duplexer, the suspended microstrip-microstrip interconnecting structure and the radio-frequency suppressing low-pass filter; the radio-frequency
signal and the
local oscillator signal are mixed in the diode and a mixed
signal is output. According to the 340GHz eighth
harmonic mixer, an eighth harmonic mixing form is adopted so that the local frequency is greatly reduced; meanwhile, the size of the mixer is effectively reduced and the manufacturing difficulty and cost are reduced.