According to the technical demand of direct digital synthesizer(DDS),in this paper we designed and realized four signal sources for high-frequency pulse radar based on the core chip AD9959,which is controlled by C8051 microcomputer. The C8051 MCU is adopted to process the input control word and then program AD9959 to produce the desired four signal sources with high precision of frequency,phase and amplitude in high-frequency pulsed radar.In addition,four low-pass filters were designed to reduce crosstalk and clutter,ensuring the output signal of good spectral purity.The signal sources have been applied in the Ionosonde of high-frequency pulse radar,and the experimental results showed that the RF signal sources had several advantages such as high frequency stability,fast scan switching speed,precise modulation of phase,and suitable for a variety of encoding,which fully meet the techinical requirements and performance index of the signal sources in high-frequency pulse radar.

The measurement precision of ionospheric virtual height can be increased by measuring the variation of ionospheric echo′s phase with scan frequency.This paper introduces the basic principle of ionospheric virtual height measurement based on ionospheric echo′s phase and the basic measurement method of combined pulse echo′s phase,and does a series of experiments of ionospheric virtual height measurement.The experimental results show that the measurement precision of ionospheric virtual height is ten times higher by means of echo′s phase method than time of arrival method.This is very important in accurate ionospheric electronic density profile inversion and ionospheric subtle structure research.