Remote loop-back device

Remote loop-back device intended to frequency-transpose a microwave signal of frequency f1 propagating in a waveguide (3) into a microwave signal of frequency f2, the transposition being carried out using a diode (8) and a local oscillator (8′) which resonates at the frequency f1-f2, with f1-f2<<f1 or f2, the signals of frequency f1 and f2 both having wavelengths close to a value λ,

• characterized in that the device is mounted outside the waveguide (3), and in that it includes:
• a first line (9) of length λ/2, a first end of which is slightly inserted into the waveguide (3) and serves as an antenna for receiving the signal of frequency f1 as well as for transmitting the signal of frequency f2, and a second end of which is connected to a first electrode of the diode (8),
• a second line (10) of length λ/2, the first end of which is connected to the first electrode of the said diode (8) and the second end of which is unconnected in order to return a very high impedance to the first end of the first line (9);
• a third line (11) whose length is close to λ/4 but without being equal to this value, the first end of the said third line (11) being connected to a second electrode of the said diode (8) and its second end being unconnected,
• the fourth line (12) of length λ/4, the first end of which is connected to the second electrode of the said diode (8) and the second end of which is connected, on the one hand, to a stub (13) and, on the other hand, to the output of the local oscillator (8′) the stub (13) being intended to return a zero impedance for the signals of wavelength λ on the second end of the fourth line (12), and
• a fifth line (14) of length λ/4, the first end of which is connected to the first electrode of the said diode (8) and the second end of which is earthed.