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Radio frequency signal processors typically require automatic gain control (AGC) in order to detect and process RF signals that may vary over a wide range of signal strength. A typical radar signal consists of bursts of RF energy referred to as pulses. From the perspective of the intercept receiver, these pulses will vary greatly in amplitude with the rotation of the transmitter’s antenna.
The Navy has developed an AGC that allows the intercept system’s signal processor to adjust for these changes in amplitude, thereby maintaining acceptable signal amplitude at the analog to digital converter (ADC). A radar signal environment typically contains multiple signals varying independently in amplitude. The new AGC is capable of functioning well in such an environment, although performance may degrade somewhat when the pulses of one signal are interlaced with those of another signal.
This AGC RF signal processor for receiver systems, includes an attenuator having an input for receiving an analog RF input signal, an amplifier coupled to the attenuator, a bandpass filter coupled to the amplifier output, a single ADC coupled to the bandpass filter, a digital logic circuit, and a FIFO buffer.
The digital logic circuit has an input for receiving the ADC output signal, an output coupled to a variable gain control input of the attenuator, and a second output. The logic circuit includes signal detection logic for detecting the presence of a pulse within the ADC signal, determining a peak amplitude value of the pulse, and based on the peak amplitude value generating an attenuation value that is applied to the variable gain control input of the attenuator.
The sampling logic averages a number of ADC data samples to determine a moving average and compares this to threshold values to detect the presence of a pulse and determine when to initiate and when to terminate storage of ADC sample data. The averaging is carried out to determine whether an assigned number m of n samples is above the processing threshold value or whether the pulse should be terminated.
- AGC circuit placed in front of the ADC to continuously adjust the signal level to be within the dynamic range of the ADC
- Optimized for detecting and processing radar signals
- Decreased cost and complexity
- Businesses can commercialize the technology by licensing U.S. Patent 7,088,794 from the Navy
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