Ultra-Wideband 6-Bit Passive Phase Shifter with Open-Circuit Microstrip Pseudo- $\pi$ Network and Low RMS Phase Error

This study presents an ultra-wideband (UWB) 6-bit passive phase shifter (PS) with low root-mean-square (RMS) phase error in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.25-\mu \mathrm{m}$</tex> GaAs technology. By adopting the opencircuit microstrip pseudo- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\pi$</tex> network (OMPN), the proposed PS achieves a low RMS phase error over a wide fractional bandwidth (FBW). The phase accuracy is improved by optimizing the characteristic impedance of the microstrip lines in the OMPN. The proposed UWB 6-bit passive PS covers 360° with a 5.625° resolution over <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{5. 5 - 1 8. 1 ~ G H z}$</tex>. Measurements indicate that the RMS phase error is below 3° at the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$107\%$</tex> fractional bandwidth (FBW). The average insertion loss (IL) is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$13 \pm 2 ~\text{dB}$</tex> with an RMS amplitude error of less than 1.1 dB. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{I P}_{1 ~\text{dB}}$</tex> is about 23 dBm. The chip area, including all pads, switch driver, DC routing, and RF routing, is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.6 ~\text{mm} \times 3.6 ~\text{mm}$</tex>.