In speed radar, if you point it at a wall and nothing is moving, the system does not show you the returns from the wall, but if you throw a baseball it will give you the speed based on calculations of the returns of various pulses returned from the object compared to the time the waves traveled.
Most consumer speed radar does not do any ranging whatsoever. Instead of pulsed, the gunn diode runs CW. The transmitted frequency is mixed with the return and the envelope is detected. With no motion the envelope is steady. With motion, a dopplar shift is generated. (Dopplar speed radar) The mixed output of the 2 frequencies is detected. The beat frequency is directly related to the Frequency of the radar and the speed of the object causing a doplar shift. The frequency is counted and displayed as speed.
One other FCC requirement besides interferance with CB or millitary. Any interferance including cordless phones, TV, sound systems, etc is prohibitied. Transmisison on most frequencies are prohibited, except those designated such as the ISM band. (Industrial, Scientiefic, Medical)
Please familiarize yourself with the FCC regulations before building any transmitter. Many (Most) have to be Type Accepted..
Here is a link to get you started and out of jail.
Section 15 is in regards to devices.
Section 18 covers the ISM frequencies.