We propose a new, to the best of our knowledge, broadband signal
downconversion scheme implemented by a monolithic integrated mutual
injection laser. A mathematical derivation, simulation, and
experimental verification are carried out. Because the period-one
oscillation frequency can be selectively operated on a large scale by
controlling the current on the integrated laser, the tuning
downconversion range is realized without changing the experimental
equipment. The experiment verifies that the downconversion of the
linear frequency modulation signal with a bandwidth of 0.5 GHz
from the center frequency of 18.75 to 0.85 GHz, and the
spurious-free dynamic range (SFDR) has reached 71.7dB/Hz2/3. Compared with the scheme based on
discrete components, the system has no electric local oscillator or
external modulator, which provides a method for radar signal
downconversion.