Research On Key Technology Of Transmitter Based On Channel Emulator

The fifth generation mobile communication(5G)has the characteristics of high speed,low latency,and large channel capacity.At present,the Sub-6G frequency band has entered the large-scale commercial stage,and the millimeter wave frequency band is undergoing intense testing.The development of 5G wireless communication system requires high-performance communication test instruments.Among them,the channel emulator,as a test instrument for wireless terminals,has an important impact on the performance of the 5G communication system.This article mainly studies the key technologies of transmitter of 5G channel emulator.A broadband low phase noise frequency synthesizer and broadband IQ modulators of 5G channel emulator are developed.The transmitter of channel emulator has the characteristics of wide frequency band,small size,and low power consumption.The main work of this paper is as follows:Combining the characteristics of low phase noise of sampling phase-locked loop and wide frequency band of digital phase-locked loop,a frequency synthesizer capable of dual-loop switching between digital phase-locked and sampled phase-locked is developed.The digital phase-locked loop is locked near the predetermined output frequency,and it is switched to the sampling phase-locked loop through the CMOS switch to ensure that the output of the frequency synthesizer has the characteristics of wide frequency band and low phase noise.The frequency output range of the dual-loop frequency synthesis scheme developed in this paper can meet the needs of 5G communication systems.After testing,when the output frequency is3.5GHz and the frequency offset is 100 k Hz,the phase noise is-123.7dBc/Hz.The test results show that the dual-loop switching frequency synthesizer has lower phase noise and higher spurious suppression.This thesis also develops an IQ modulator with a wide frequency band and high local oscillation suppression applied to direct modulation transmitters,with a working range of6?28GHz.This modulator is a key component of a direct modulation transmitter.The IQ modulator is composed of two wideband IQ mixers,one produces the main output signal,the other produces the inverted local oscillator signal with adjustable amplitude.The two signals are combined and output to cancel the local oscillator signal,thereby generating a wideband IQ modulated signal with high local oscillation suppression.According to the performance simulation of IQ modulator by EDA simulation software ADS,an IQ modulator working at6?28GHz was developed.After testing,When the input frequency of the modulator's local oscillator is 14 GHz,the local oscillation suppression is improved by 18.47 dB.Use this modulator to modulate 16 QAM intermediate frequency signal with bandwidth of 400 MHz,the measured vector modulation error is 0.94%.