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The blind velocity for a specific pulse repetition frequency (PRF) is an integer multiple of the following, which causes the signal to have zero doppler. B l i n d V e l o c i t y = ( C × P R F 2 × T r a n s m i t F r e q u e n c y ) {\displaystyle Blind\ Velocity=\left({\frac {C\times PRF}{2\times Transmit\ Frequency}}\right)}
By storing the phase signal, instead of the original analog signal, or video, and comparing the stored and current signal for changes in phase, the moving targets are revealed. This technique is far more resistant to noise, and can easily be tuned to select different velocity thresholds to filter out different types of motion. [1]
The system was developed partly because access to foreign government-controlled global navigation satellite systems is not guaranteed in hostile situations, as happened to the Indian military in 1999 when the United States denied an Indian request for Global Positioning System (GPS) data for the Kargil region, which would have provided vital information. [22]
Pulse-Doppler signal processing is a radar and CEUS performance enhancement strategy that allows small high-speed objects to be detected in close proximity to large slow moving objects. Detection improvements on the order of 1,000,000:1 are common.
Inertial navigation is a self-contained navigation technique in which measurements provided by accelerometers and gyroscopes are used to track the position and orientation of an object relative to a known starting point, orientation and velocity.
Doppler systems involve velocity measurements similar to the kind of measurements made using a strobe light. For example, a strobe light can be used as a tachometer to measure rotational velocity for rotating machinery. Strobe light measurements can be inaccurate because the light may be flashing 2 or 3 times faster than shaft rotation speed.
This audio signal allows the pilot to concentrate on the external view instead of having to watch the instruments, thus improving safety and also giving the pilot more opportunity to search for promising looking clouds and other signs of lift. A variometer that produces this type of audible tone is known as an "audio variometer".
The velocity integrators operate in a similar manner to the acceleration integrators, except that the output signal is not smoothed because the so-called M-transmitters are step-function devices. The M-transmitters send the integrated velocity (= distance) signal to the Position and Homing System PHI-4.