A novel method to synchronize high-speed data converters

Abstract

Phased array and MIMO (Multiple Input Multiple Output) radar systems are being developed with greater number of channels to achieve more flexibility, speed and range. Each channel contains either an ADC (Analog to Digital Converter) — for a receiver channel — or a DAC (Digital to Analog Converter) — for a transmission channel. In such large array, the channels need to be time synchronized as precisely as possible. This is one of the key to reach higher performance systems. One of the main synchronization to realize is at the data converter level. It is necessary to make sure that all channels sample the data at the precise same time to avoid errors in the transmission — such as corruption of orthogonality of an OFDM modulation. In system requiring small instantaneous bandwidth, and thus using low speed data converters (up to a few hundreds of megahertz), synchronizing the multiple channels is easier; the period of the system being larger. However for large instantaneous bandwidth — which relates to sampling rate — and high-speed data converters, synchronizing the channels become challenging. This paper presents an innovative method to synchronize high-speed data converters. This method uses a daisy chain approach with meta-stability detection and correction features to ease synchronizing large number of data converters. In this paper, the difficulty of high-speed synchronization will be discussed; the new method will be presented, along with its calibration and measurement results. Finally, the benefits and limitations of the method will be considered.