Radio frequency particulate sensing system

A particulate sensing system for a particulate trap comprising:

• a particulate trap including a filter body and a filter medium;
• a radio frequency transmit circuit including:
• a waveform generator configured to generate at least one waveform signal;
• a sample trigger line coupled to the waveform generator and configured to provide a sample trigger signal;
• a voltage controlled oscillator coupled to the waveform generator and configured to produce a narrowband radio signal having a frequency that is proportional to the waveform signal;
• a transmit antenna disposed within the filter body and adjacent to the filter medium and coupled to the voltage controlled oscillator, the transmit antenna configured to propagate the narrowband radio frequency signal through the filter medium;
• a radio frequency receive circuit including:
• a receive antenna, disposed in the filter body opposing the transmit antenna and adjacent to the filter medium, the receive antenna configured to receive the narrowband radio frequency signal propagated through the filter medium;
• a bandpass filter coupled to the receive antenna and configured to limit a frequency range of the received narrowband radio frequency signal;
• a radio frequency power sensing device coupled to the bandpass filter and configured to sense a power level of the received narrowband radio frequency signal and configured to provide an output signal proportional to the total power received across an operating frequency range of the radio frequency power sensing device;
• a low pass filter coupled to the radio frequency power sensing device and configured to integrate the output signal;
• and
• a sample-and-hold circuit coupled to the low pass filter and the sample trigger line, the sample-and-hold circuit configured to sample an output of the low pass filter using the sample trigger signal, hold the sampled value, and produce an analog signal representing received radio frequency power.

A method of sensing particulate matter in a particulate trap, the method comprising:

• providing a radio frequency transmit circuit including a waveform generator, a sample trigger line, a voltage controlled oscillator, and a transmit antenna;
• generating at least one waveform signal using the waveform generator;
• providing a sample trigger signal using the sample trigger line;
• producing a narrowband radio frequency signal based on the waveform signal using the voltage controlled oscillator;
• propagating the narrowband radio frequency signal through a filter medium of the particulate trap using the transmit antenna;
• providing a radio frequency receive circuit including a receive antenna, a bandpass filter, a radio frequency power sensing device, a low pass filter, and a sample-and-hold circuit;
• receiving the narrowband radio frequency signal propagated through the filter medium using the receive antenna;
• limiting a frequency range of the received narrowband radio frequency signal using the bandpass filter;
• sensing a power level of the received narrowband radio frequency signal using the radio frequency power sensing device;
• providing an output signal proportional to the total power received across an operating frequency range of the radio frequency power sensing device;
• integrating the output signal using the low pass filter;
• and
• producing an analog signal using the sample-and-hold circuit, the analog signal representing received radio frequency power.