Abstract

Microstrip patch antennas are widely used in 2.4 GHz ISM-band radios, yet narrow bandwidth and modest gain limit them, and no existing review isolates this single-band case. Following PRISMA 2020, we searched Scopus, IEEE Xplore and Web of Science, identified 3,046 records and sought 280 reports; the 191 read in full yielded 137 studies from 2015 to 2025, every value traced to its full text. Five technique families emerged: EBG, metamaterial, FSS and superstrate structures (43 studies); arrays (33); slots, parasitic elements and fractals (26); defected ground structures (22); and air gap or substrate engineering (13). Among single structures, 50 studies pair a baseline bandwidth with an enhanced value and 49 pair a gain. The median changes are +69% and +1.3 dB, and they stay between +32% and +98% and between +0.8 and +2.5 dB under five sensitivity checks. Only one bandwidth pair and four gain pairs are measured; 41 and 39 are simulated, with medians of +54% and +0.8 dB, and the rest leave the validation type of one value unstated. Twenty-eight studies make a claim in the abstract or title that their own results contradict, and in 16 the claim favours the design. The literature reports large simulated improvements and almost no measured before-and-after evidence, so these figures describe what is reported rather than estimate effects.