Frequency standard comparison measurement has important practical significance for the rational use of frequency standard in engineering. This paper was devoted to the study of frequency standard comparison measurement based on classical dual mixing time difference method. However, in the actual system design and implementation, the commonly used counter was discarded and the phase difference was measured by a digital signal processing method based on Field Programmable Gate Array (FPGA). A miniaturized 10 MHz frequency standard comparator with good noise floor was successfully developed. The size of the prototype circuit board is only about 292.1 cm2. The experimental results showed that the noise floor of the frequency standard comparator was typically better than 7.50 × 10-12/s, and its relative error of phase difference measurement was less than 1.70 × 10-5.
With the development of global navigation satellite systems (GNSS), multiple signals modulated on different sub-carriers are needed to provide various services and to ensure compatibility with previous signals. As an effective method to provide diversified signals without introducing the nonlinear distortion of High Power Amplifier (HPA), the multi-carrier constant envelope multiplexing is widely used in satellite navigation systems. However, the previous method does not consider the influence of sub-carrier frequency constraint on the multiplexing signal, which may lead to signal power leakage. By determining the signal states probability according to the sub-carrier frequency constraint and solving the orthogonal bases according to the homogeneous equations, this article proposed multi-carrier constant envelope multiplexing methods based on probability and homogeneous equations. The analysis results show that the methods can multiplex multi-carrier signals without power leakage, thereby reducing the impact on signal ranging performance. Meanwhile, the methods could reduce the computation complexity. In the case of three different carriers multiplexing, the number of optimization equations is reduced by nearly 66%.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.