new feed system is presented for improving the quality and bandwidth of circularly polarised stacked microstrip antennas (CPSMAs). The feed system consists of a microstrip line and a via (or pin) from the microstrip line to a driven patch. A systematic design process to achieve near-optimal CP performance from these antennas is presented. An example design demonstrated a measured 3 dB axial-ratio (AR) bandwidth of 17% and a measured 10 dB return bandwidth of 35%. The measured gain is more than 8 dBic over the 3 dB AR bandwidth. The total height of the antenna is 8.536 mm or 0.156lo at 5.5 GHz. The new feed system is found to be very useful for the design of wideband, compact, low-cost, CP microstrip antennas and arrays.