Microstrip Leaky-Wave Antennas With Nonuniform Periodical Loading of Shorting Pins for Enhanced Frequency Sensitivity

This paper investigates on an effective approach to enhance frequency sensitivity of the classic wideband EH1-mode microstrip leaky-wave antenna (MLWA). Nonuniform loadings of shorting pins are installed into the traditional EH1-mode microstrip line, which provide a unique discontinuity affecting the mutual intersection of the passband and stopband, thus generating a newly created stopband within the continuous EH1-mode fast-wave region. After broadening the stopband, the slope of normalized phase constant is remarkably raised up and the original wide bandwidth of the operating region is effectively reduced, resulting in a dramatically enhanced frequency sensitivity. An equivalent-circuit model of the proposed EH1-mode MLWA with nonuniform loading is built up at first, then its nonuniform loading discontinuity effect on dispersion transformation between passband and stopband is further explicated. Moreover, full-wave numerical extraction is also conducted to accurately demonstrate the modified phase constant under varied lateral pins' loading positions and strip widths. After thorough discussion, one set of optimized parameters are selected into antenna design. Compared with the conventional counterpart, the proposed EH1-mode MLWA with nonuniform loading of shorting pins notably increases the frequency sensitivity from 0.038°/MHz to 0.135°/MHz.