The upgrade program, called the HARM Control Section Modification, adds a GPS receiver to the missile as well as an improved inertial measurement unit.
Other enhancements are a digital flight computer that merges targeting solutions from navigation and seeker systems.
"HCSM improves HARM's anti-radar capability to defeat counter-HARM tactics, while reducing the risk of fratricide and collateral damage," said Harry Schulte, vice president of Air Warfare Systems for Raytheon Missile Systems.
"HCSM also enables warfighters to leverage HARM's supersonic speed and standoff capability to rapidly and accurately engage time-critical targets."
HARM missiles are designed to destroy surface-to-air missile radars, early warning radars and radar-directed air defense artillery systems.
Raytheon is competing for a full-rate production contract from the U.S. Air Force for missile enhancements.
"Raytheon's HCSM offers the warfighter enhanced capability and we believe it will provide the taxpayer the best value," said Chuck Pinney, Raytheon Missile Systems' HARM program director.
"Instead of buying similar systems that cost more, or spending billions of dollars to develop an entirely new system, Raytheon's HCSM will give HARM new capability at an affordable price."