Doppler Speed Radar

Is there a way of increasing the range of the Doppler radar? As in the data sheet of the Doppler radar(that I bought from an Indian market) shows a maximum sensing range of 20ms . But when I tested it on road, it gave me hardy1.5-1.8ms sensitivity. The parallex X-band sensor have a range 2.4-9m approx. I need to increase the range of my Doppler since I cannot get a parallex model whose sensitivity range can be controlled with a trim pot.