| Popis: |
With the aim to enhance the phase shift range and bandwidth of the novel Inverted-E topology for single-bit and multi-bit phase shifters, this work proposes a new structure, wherein the $50~\Omega $ Main Transmission Line (MTL) in the Inverted-E topology is replaced by a tunable transmission line with a fixed open circuited stub loaded at its center point. Therefore, offering four design freedoms, precisely the characteristic impedances and electrical lengths of the transmission line and the fixed open circuited stub, that provides it the flexibility to achieve much smaller susceptance values for large phase shifts up to 180°. The required susceptances are realized using three symmetric open or short-circuited stubs, which are loaded to the tunable transmission line using switching p-i-n diodes. The fixed open circuited stubs ensure excellent circuit matching to the port impedance of $50~\Omega $ in the OFF-state, without the need of any additional matching network. Whereas, the enhanced design flexibility enables the realization of compact dimensions and lower insertion loss. A systematic design procedure is developed, supported by detailed design theory and mathematical formulations, followed by validation through analysis and simulations of typical 22.5°, 45°, 90° and 180° digital phase shifters. For experimental verifications, 90° and 180° designs are manufactured at center frequency of 2.4 GHz and a good agreement is observed with theory and simulations. The results indicate compact dimensions of $0.36\lambda \text{g}\,\,\times 0.14\lambda \text{g}$ and $0.33\lambda \text{g}\,\,\times 0.27\lambda \text{g}$ , corresponding insertion losses of 1.7 dB and 2.85 dB with phase error less than 1° at center frequency. Moreover, the phase variation is observed to be 2° and 5°, in bandwidths of 400 MHz and 100 MHz respectively. |
