Method and apparatus for adjusting threshold weight of frequency domain to improve anti-jamming performance and eliminate jamming in GPS system
A method and apparatus for improving anti-jamming performance are provided. A threshold value level estimated in a GPS (global positioning system) receiver RF/IF stage, a threshold value weight, a median value of a median value of a 2˜8 MHz bandwidth is estimated as a threshold value with respect to a frequency component exceeding the estimated threshold value level, and an adjustable K-median threshold scheme is provided in a multi-jamming environment.
1. An adjustable GPS jamming elimination method implemented by a jamming excisor, the method comprising:
converting a signal received from a reception antenna to a signal in a frequency domain;
determining a jamming signal in an in-band spectrum of the converted signal in the frequency domain;
setting initially an estimated threshold value for anti jamming filtering;
selecting a median value in a frequency domain of the jamming signal;
determining a conclusive threshold value by applying the estimated threshold value to an adjustable threshold value based on an amplitude of the median value; and
determining whether to eliminate an individual bin of the jamming signal as an interference frequency component based on the conclusive threshold value.
2. The method of claim 1 , wherein the adjustable threshold value is obtained by using a JNR (jamming to noise ratio) gain that corresponds to a ratio between the amplitude of the median value and nose of a receiver.
3. The method of claim 2 , wherein the adjustable threshold value is divided into four stages based on the amplitude of the median value.
4. The method of claim 2 , further comprising:
when the JNR gain is 10 dB or smaller, setting the adjustable threshold value as 4;
when the JNR gain exceeds 10 dB, determining whether or not the JNR gain exceeds 25 dB, and when the JNR gain is 25 dB or lower, setting the adjustable threshold value as 3, and when the JNR gain exceeds 25 dB, determining whether or not the JNR gain exceeds 40 dB; and
when the JNR gain is 40 dB or lower, setting the adjustable threshold value as 2, and when the JNR gain exceeds 40 dB, setting the adjustable value as 1.
5. The method of claim 1 , wherein the median value is a median value of an in-band spectrum of a received signal.
6. The method of claim 5 , wherein the received signal is a signal received from one or more of a GPS system, a GLONASS system, and a Galileo system.