Single Sideband Up-Down Converter for Sub-Octave Bandwidth Transmission of Low Frequency Signals

A system comprising:

• a quadrature hybrid coupler receiving an input signal having a frequency, f0, and outputting a first signal in phase with the input signal at a first coupler output and a second signal 90° out of phase with the input signal at a second coupler output;
• a local oscillator (LO) subsystem producing a first LO signal having frequency, f1, with f1>f0 and in phase with the input signal and a second (LO) signal having frequency, f1 and 90° out of phase with the first LO signal;
• a first mixer downstream of the first coupler output, the first mixer receiving the first LO signal and outputting a first mixed signal;
• a second mixer downstream of the second coupler output, the second mixer receiving the second LO signal and outputting a second mixed signal;
• and
• a summer downstream of the first mixer and second mixer for producing a first transmission signal;
• a source of a second transmission signal;
• and
• a combiner for frequency stacking the first transmission signal and the second transmission signal, and wherein the first transmission signal and the second transmission signal have frequencies in a sub-octave band of frequencies between a low frequency fL and a high frequency fH, wherein fH<2fL.

A method for processing an input signal having a frequency, f0, to produce an upshifted signal having a suppressed sideband for transmission over an optical fiber, said method comprising the steps of:

• receiving the input signal at a quadrature hybrid coupler and outputting a first signal in phase with the input signal at a first coupler output and a second signal 90° out of phase with the input signal at a second coupler output;
• producing a first local oscillator (LO) signal having frequency, f1, with f1>f0 and in phase with the input signal and a second (LO) signal having frequency, f1 and 90° out of phase with the first LO signal;
• receiving the first LO signal at a first mixer downstream of the first coupler output, and outputting a first mixed signal;
• receiving the second LO signal at a second mixer downstream of the second coupler output, and outputting a second mixed signal;
• and
• summing signals downstream of the first mixer and second mixer to output an upshifted, sideband suppressed signal.