  We present an enhanced design -- in terms of resolution flexibility, input
port position arbitrariness and frequency-range tunability -- of the planar
Rotman lens spectrum decomposer (RL-SD). This enhancement is achieved by
manipulating the output port locations through proper sampling of the
frequency-position law of the RL-SD, inserting a calibration array compensating
for frequency deviation induced by input modification and introducing port
switching, respectively. A complete design procedure is provided and two
enhanced RL-SD prototypes, with uniform port distribution and uniform frequency
resolution, respectively, are numerically and experimentally demonstrated.
