Использование радиофотонного аналого-цифрового преобразователя в структуре цифрового радиоприёмного устройства
Authors: Денисов А.Е. , Данилаев Д.П. 
Published: February 2025

В статье рассмотрены характеристики, структура и отличительные особенности фотонных аналого-цифровых преобразователей (ФАЦП). Определено преимущество достигаемой ФАЦП частоты дискретизации, позволяющей обрабатывать сигналы СВЧ-диапазона без использования переноса частоты и предварительной фильтрации. Исследована возможность увеличения отношения несущей к шуму и эффективного числа бит за счёт усиления принимаемого сигнала. Определены требования и представлено структурное решение, позволяющее использовать преимущества ФАЦП для достижения лучших параметров приёмника.

Introduction Designing digital radio receivers poses challenges primarily related to the selection of ADCs and the constraints they introduce. These challenges include high intrinsic noise levels with varying sources, limited sampling rates, and more. Consequently, the architecture of digital radio receivers incorporates an initial analog component responsible for receiving and processing signals before digitization. The integration of microwave photonics offers a means to move the radio receiver's design closer to the optimal configuration for digital signal processing while enhancing certain receiver parameters. Photonic ADCs hold promise as a key element in achieving these goals. The aim of the work is to assess how photonic ADCs (PADC) impact the parameters and configuration of a digital radio receiver. Evaluation of the parameters of the PADC/ To evaluate the impact of the ADC on the design and parameters of the digital radio receiver, we need to examine the characteristics of the converter. The following advantages are worth noting: 1. The high sampling frequency of 100 GHz has two significant benefits. Firstly, it enables the processing of signals up to 50 GHz, eliminating the need for a mixer to downconvert the signal to a lower frequency. This, in turn, removes an element with a high inherent noise level. Secondly, the PADC's sampling frequency allows for the avoidance of an anti-aliasing filter due to its wide Nyquist zone. The absence of noise from other zones can be achieved by employing antennas tuned to the specific frequency range of the received signals. 2. Incorporating optical elements in the PADC structure enhances the carrier-to-noise ratio (CNR). This is achieved by increasing the average optical power on the photodiode, particularly when the effective noise from the relative intensity of the optical source is negligible. Furthermore, raising the received radio signal level allows for an increase in the optical modulation index. 3. The effective number of bits (ENOB) is directly linked to the carrier-to-noise ratio. Therefore, increasing the average optical power on the photodiode or enhancing the received radio signal also leads to an increase in ENOB. The design of a digital receiver with a PADC. To harness the advantages offered by the PADC, the design of the preliminary section must adhere to specific requirements. It should amplify the received signal in a manner where the most substantial gain is applied to the weakest signal while the strongest signal receives the lowest gain. To fulfill these requirements, a system with channel switching is suggested. This system is configured such that all amplifiers possess different gain levels and are situated in separate branches. At the output of each amplifier, a PADC is employed. Consequently, the selection of the channel in which the signal performs optimally is determined within the software environment. Conclusion. The paper delves into the impact of the PADC on the parameters and structure of a digital radio receiver. An evaluation of the potential advantages of employing the PADC is conducted. Furthermore, a structural approach is presented, offering a means to fully realize the benefits of the PADC.