This paper focuses on the opportunities offered by the latest advances in silicon technologies for realizing system-on-chip microwave radiometer. Such a highly integrated, low-cost, radiometer chip could be applied to the environmental remote sensing and, in particular, to the forest fire detection. The feasibility study is carried-out in two steps. First, a proof of the concept is given by means of a discrete-component radiometer operating at 12.65 GHz. This radiometer exploits TV-SAT components such as low-noise down-converter and dish antenna. On-field measurements shows a radiometric contrast (increase of the antenna noise temperature due to the fire with respect to the background) of about 8 K for a wooden fire of 0.38 m 2 placed 30 m away from the antenna. Then, a single-chip 13 GHz radiometer has been designed exploiting a CMOS 90 nm standard process. The sensor is based on a direct-conversion architecture with integrated LNA, Gilbertpsilas cell mixer and PLL frequency synthesizer. The IF chain includes an active (gm-C) low-pass filter and a CMOS square-law detector. The circuit simulations show a total receiver gain of 72 dB, an equivalent input noise temperature of 105 K and an IF bandwidth of 100 MHz.