In this Phase I SBIR proposal we describe our plan to develop two key technologies for future combined radar/radiometer systems operating at L-band. The first, a dual frequency, dual polarization microstrip antenna array, will allow a 1.2 GHz radar and a 1.4 GHz radiometer to share a single aperture. The second, an integrated transmit/receive (T/R) module, will combine a 2W transmitter with digital phase and amplitude control with a low-noise down-converting receiver. Phase I research will involve selecting appropriate broadband patch and feed network designs, evaluating their performance using GENESYS, a commercial RF simulation package. Candidate T/R module designs will also be evaluated using GENESYS. The imaging capability of the resultant designs will be tested on realistic ocean and land scenes using a custom software package developed by ProSensing.