Atomic clock digital modulation circuit

Abstract

The invention discloses an atomic clock digital modulation circuit, comprising a crystal oscillator, a single-chip microcomputer, a D trigger, a direct digital frequency synthesizer, an exclusive-OR gate, a crystal filter and a triode frequency selection amplification circuit. One path of the 10MHz crystal oscillator generates a 5MHz signal after frequency division by a D trigger, and the other path generates a 312.5 KHz modulation signal through a direct digital frequency synthesizer, the two signals are subjected to frequency combination through an exclusive-OR gate to generate a 5.3125 MHzmodulation signal, and the modulation signal passes through a crystal filter and a triode frequency selection amplification circuit to obtain a mantissa with stable power and high frequency spectrum purity. The clock circuit of the direct digital frequency synthesizer is simple in circuit structure, and is characterized in that the clock circuit of the direct digital frequency synthesizer does notneed to be additionally provided with a frequency doubling circuit, the frequency spectrum purity of 5.3125 MHz signals is high, the modulation depth and the center frequency are accurate and adjustable, the adaptability to rubidium absorption bubbles is high, and the clock circuit can be directly applied to a high-performance rubidium atom frequency standard circuit.

Description

technical field [0001] The invention belongs to the field of digital frequency modulation circuits, and more specifically relates to an atomic clock digital modulation circuit, which can be directly used in space-borne rubidium atomic frequency standards and high-performance commercial rubidium atomic frequency standards. [0002] technical background [0003] Rubidium atomic frequency standards are widely used due to their small size, low power consumption, and good stability, especially in the fields of satellite positioning and navigation. It is mainly composed of two parts: physical system and circuit. The former provides a reference frequency as a frequency discriminator, and the latter is equivalent to a frequency locked loop to lock the output frequency of the voltage-controlled crystal oscillator to the reference frequency of the physical system. The circuit part is mainly composed of RF frequency multiplier, frequency synthesizer, modulator and servo circuit. [00...

AI Technical Summary

Problems solved by technology

[0006] In the present invention, if the 5.3125MHz modulation signal is directly generated by a direct digital frequency synthesizer (DDS), according to the Nyquist theory, then the input clock frequency of the direct digital frequency synthesizer (DDS) is at least more than 25MHz. For the 10MHz signal of the crystal oscillator, the design of the frequency multiplier circuit must be added, which will complicate the circuit and introduce additional circuit noise

Images