Magnetic resonance detection (MRD) system for and methods of detecting and classifying multiple chemical substances

A magnetic resonance detection apparatus, comprising:

• a frequency-tunable transducer circuit comprising a coil and a tuning network;
• a transmit/receive switch circuit having a common port coupled to the frequency-tunable transducer circuit and having a multi-octave operating bandwidth;
• a transmitter circuit coupled to an input port of the transmit/receive switch circuit, the transmitter circuit comprising a power amplifier with a multi-octave operating bandwidth;
• a digital quadrature receiver circuit coupled to an output port of the transmit/receive switch circuit and having a multi-octave operating bandwidth;
• a tunable frequency source coupled to the transmitter circuit and to the receiver circuit, the tunable frequency source having a multi-octave operating bandwidth;
• and
• a controller circuit configured to control the frequency source, the transmitter circuit, and the transmit/receive switch so as to emit a series of radio-frequency (RF) pulses from the coil and further configured to control the frequency source, the receiver circuit and the transmit/receive switch so as to measure nuclear quadrupole resonance (NQR) responses after each RF pulse.