The differential method is extensively adopted in the group delay measurement, where a contradiction between frequency-resolution and precision is present owning to the phase measurement error. This paper proposes a novel method for group delay calculating based on improved Tikhonov regularization that can omit the difference procedure. The comparative analysis demonstrates that the new method is capable of obtaining more precise group delay value along with high frequency-resolution when the measurement error of phase is included.
True time delay lines and phase shifters are widely used in RF timed/phased array systems. Conventional delay lines and phase shifters often associate with reflection type circuits or distributed (periodically loaded) transmission lines. In this paper, we propose a new type of distributed circuit which composed of uniform transmission lines built on integrated Schottky active layer. A bi-functional chip is designed based on the new distributed structure. An Archimedean spiral topology is adopted to reduce the chip area. Theoretical analysis of the design method and circuit parameters is performed and a miniaturized prototype is implemented with p-HEMT technology to validate the design theory. Measurement results shows that this chip could work as either an areaefficient true-time delay line or a low-voltage phase shifter over the bandwidth 11-15 GHz. As an area-efficient true-time delay line, this chip provides 82.1 ps delay time per square millimeter when the biasing voltage fixed at −1.4 V. As a low-voltage phase shifter, this chip provides 26.43°p hase shift per volt when the biasing voltage sweeps form 0 V to −1.4 V.
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