Multiport ADCs for Microwave Focal Plane Array Dish Receivers

This paper proposes an architecture that reduces the complexity of traditional N-bit ADCs used in focal plane array (FPA) dish receivers by replacing them with multiport ADCs. The proposed ADC architecture uses a multi-dimensional (MD) noise-shaping method based on a Δ-Σ architecture for wideband RF signals that are received on the focal region of a parabolic dish/lens antenna. In the M-port noise shaping technique, the N-bit quantizers of conventional ADCs are replaced by 1-bit quantizers followed by a spatial feedback system based on a Δ-Σ architecture with spatial oversampling, which shapes the quantization noise out of the region of support (ROS) of the electromagnetic (EM) waves received from the dish. The paper discusses the case of a prime-axis pencil beam in detail for the simplified case of a linear FPA. Simulations for 2.1-5.1 GHz wideband dish signals show 16-element FPAs with oversampling ×l, ×2, and ×4 shows ADC effective number of bits (ENoB) improvements of 2.5 bits, 3.2 bits and 4.2 bits, respectively. Extensions to off-axis pencil-beams and rectangular FPAs will be considered in future work. Potential applications exist across microwave and mm-wave bands, for radio astronomy, radar, and wireless communications.