Krishnamachari Uppili

Coherent Receiver for High Linearity Radio Frequency Photonic Links Krishnamachari Uppili

Radio frequency photonic links employing phase modulation can exhibit high dynamic range provided the received RF signal can be linearly demodulated. The linearity of conventional interferometer based coherent receivers is limited by their sinusoidal response. A balanced receiver with negative feedback to a reference tracking modulator is presented in this text. In order to achieve high linearity, the tracking modulator is used to reduce the net phase swing across the demodulator such that the interferometer response is restricted to its linear regime without penalty to the signal to noise ratio. In order to achieve linear phase tracking at high frequencies, high loop gain and loop bandwidth are required. This means the physical delay of the feedback loop must be sufficiently short enough to prevent loop instability at higher frequencies. Novel techniques in monolithic integration of the receiver components is thus utilized to achieve an ultra-compact receiver architecture.