Expanding the Dynamic Range of Radio Receivers with Photonic ADCs

Introduction. The field of radio photonics has advanced rapidly, enabling the development of photonic analog-to-digital converters (PADCs) with distinct advantages over traditional electronic ADCs. PADCs offer new opportunities for designing digital radio receivers with enhanced performance. This paper evaluates the potential of PADCs in radio receivers through modeling in specialized software. The study addresses the following objectives: (1) selecting an optimal PADC circuit for a radio receiver, (2) developing a model of a radio receiver incorporating a PADC, (3) fine-tuning the PADC elements’ parameters, (4) validating the model using a test signal mixed with noise, and (5) assessing the performance characteristics of the receiver with a PADC. Modeling. The model of the PADC’s optical circuit was developed using OptiSystem software, which provides an extensive library of optical and electronic components with adjustable parameters. This setup enables a detailed analysis of how individual elements affect PADC performance. OptiSystem also integrates with MATLAB for additional computational capabilities. Established models of circuit components, such as a mode-locked laser with specifications aligned with real-world systems, were incorporated during model development and testing. Results. The resulting model of a digital radio receiver with an all-photonic ADC exhibits the following characteristics: 1) Bit depth – 8 bits, scalable by adding channels; 2) Sampling frequency – Adjustable via pulse repetition rate, reaching up to 100 GHz in the model; 3) Noise considerations – Accounts for intrinsic noise from optical and electronic components. Simulations revealed that a 4 dB increase in insertion loss at the Mach-Zehnder modulator (MZM) could cause signal degradation, which can be mitigated by adjusting the comparator’s response level. Notably, maximizing the photodiode’s thermal noise did not alter the output signal. Conclusion. The proposed digital radio receiver with a PADC achieves a sensitivity of -110 dBm in the absence of external interference. The structure supports signal processing up to 50 GHz without requiring additional filtering or signal transfer components. This design demonstrates the potential of PADCs to enhance the dynamic range and performance of radio receivers.