Digital receiver function

The signal processor performs the following functions:

  • Filtering (smoothing) the IF signal using one of the two types of FIR filters: the legacy bandpass filter where the user sets the filter length and bandwidth, or the matched filter which is a conjugated version of the transmit waveform. These include range gating and option coherent averaging.
  • Measuring the transmit burst sample and calculating its frequency, phase, and amplitude
  • Correcting the I and Q phase and amplitude based on the transmit burst sample
  • Optionally correcting I and Q based on the interference filtering algorithm
  • For magnetron systems, calculating the AFC frequency error to apply corrections in the STALO control

The digital approach allows the software algorithms for these functions to be easily changed. Configuration information (for example, processor major mode, PRF, pulse width, range gate spacing, and so on) is supplied from the RVP10SRV host computer.

After IFDR10 has generated I and Q data, these can be corrected in a number of manners. The transmit burst pulse is sampled to measure its frequency, phase, and power. With this information, the following corrections may be performed.

I and Q data correction methods
Correction method Description
Amplitude correction The RVP10 burst pulse analysis computes a running average of the transmit power. Individual received I and Q samples are corrected for pulse-to-pulse deviations from this average. This can substantially improve the phase stability of a magnetron system for clutter cancellation performance to near klystron levels. This also optionally allows adjustment in the radar constant calibration to account for different power levels pulse-to-pulse.
Phase correction The phase of the transmitted pulse is measured. The I and Q values are adjusted for this measure phase, so that the phases stored have a common reference point. The coherency achievable is better than 0.1 degree by this technique.
Large signal linearization

When an IF signal saturates the ADCs, there is still considerable information in the signal since only the peaks of oscillating wave are clipped.

The proprietary large signal linearization algorithm used in RPV10 provides an extra 3 - 4 dB of dynamic range accounting for the effects of saturation.