Design Of Nonlinear Ampltude And Phase Test Module Of Tavelling-wave-tube-amplfier

As a kind of vacuum device work in the large-signal microwave status,travelling-wave-tube amplifier(TWTA) with excellent performance wideband, high gain and high operating frequency, etc., are widely used in the field of deep space radio communications and electronic countermeasures to detect, and which plays an important role in the signal amplification. Since TWTA is a non-linear device, under large signal conditions it will exhibit nonlinear amplitude and phase(AM-AM, AM-PM) effects which will affect the whole system lead to bad communication quality. Based on this, it is necessary to create a pre-test module for TWTA’s AM-AM, AM-PM effects.Based on the basic principles of TWTA test, first, this paper survey the research status on non-linear amplitude and phase of the TWTA both here and abroad. Through in-depth understanding of both the amplitude and phase of the testing system, taking fabricating cost, on-line testing and test precision into account, here proposes the use of amplitude and phase tests based on six-port circuit. The derivation of the amplitude correlation coefficient, confirmed the test module using six-port circuit as a non-linear amplitude and phase components is rational. This article studied and tested module design from the following aspects:1. Based on the test philosophy, determined using multi-section coupler with asymmetric form as sampling device. Doing a research on multi-section symmetric/asymmetric coupler,and a modified 10 dB coupler with coupling about 10±1dB, return loss >15dB, isolation >20dB has been made out.2. In order to improve return loss and isolation performance, 2~8GHz 90° hybrid coupler with zigzag structure has been made out, and a 6~18GHz 90° hybrid coupler with rectangular structures has been designed. The measured results show that: 2~8GHz 90° hybrid coupler possessed a performance of return loss >20dB, isolation >25dB; 6~18GHz 90° hybrid coupler had a performance of return loss >15dB, isolation >17dB3. Researching the innate characters of the ultra-wide-band Wilkinson power divider, which including chebyshev transformer and isolation resistors. And given the methods to design power dividers worked in 2~8GHz and 6~18GHz frequency,and simulation procedure have been carried out to the power dividers. The physical of the power divider worked in the frequency 2~8GHz have been made out;4. Based on the design principle of 90° hybrid coupler, semi- and fully- integrated forms of six-port circuits worked in 2~8GHz have been designed, and a fully- integrated form 6~18GHz six-port has been developed. A test system has been set up to verify the feasibility of the module. Compared with Agilent E8363 B measured scores, the test results show that: amplitude error less than 1.2dB, phase error less than 10°.