Direct PWM reflectometer

A time domain reflectometer (TDR), comprising:

• a transmit pulse generator for producing transmit pulses at a transmit clock frequency;
• a conductor connected to the transmit pulse generator;
• a transmission line connected to the conductor for conducting transmit pulses to and reflecting pulses from a discontinuity along the transmission line produced by extending the transmission line into a material;
• a termination connected to the conductor to terminate reflected signals from the transmission line and to form a realtime pulse width modulated (PWM) signal;
• a detector and converter connected to the termination to detect the realtime PWM signal and convert the realtime PWM signal to a digital PWM signal;
• a signal processor to obtain material level from the digital PWM signal.

A method of detecting the level of a material, comprising:

• producing transmit pulses at a clock frequency;
• transmitting the transmit pulses into a transmission line which extends into the material;
• combining the transmitted pulses with echo pulses from the transmission line to form a realtime PWM signal;
• threshold detecting the realtime PWM signal;
• processing the detected realtime PWM signal to indicate material level.

A method of detecting the level of a material, comprising:

• producing transmit pulses at a clock frequency;
• transmitting the transmit pulses into a transmission line which extends into the material;
• combining the transmitted pulses with echo pulses from the transmission line to form a realtime PWM signal;
• producing receive clock pulses with swept phase relative to the transmit clock pulses;
• sampling the realtime PWM signal with timing from the receive clock pulses to produce an expanded-time PWM signal;
• processing the detected realtime PWM signal to indicate material level.

A method of detecting the level of a material, comprising:

• operating a transmit clock at a transmit clock frequency;
• producing, at the transmit clock frequency, transmit pulses;
• transmitting the transmit pulses into a transmission line which extends into the material;
• combining the transmitted pulses with echo pulses from the transmission line to form a realtime PWM signal;
• operating a receive clock at a receive clock frequency that is offset from the transmit clock frequency by a floating frequency Δ;
• sampling the realtime PWM signal with timing from the receive clock to produce an expanded-time PWM signal having a floating repetition period 1/Δ;
• processing the detected realtime PWM signal to indicate material level substantially independent of Δ.

A time domain reflectometer (TDR), comprising:

• a transmit-pulse generator for producing transmit pulses,
• a conductor connected to the transmit pulse generator,
• a transmission line connected to the conductor for conducting transmit pulses to and reflecting pulses from a discontinuity along the transmission line at a range to be determined produced by extending the transmission line into a material,
• a termination connected to the conductor to terminate reflected transmit pulses received from the transmission line and to form a realtime PWM signal,
• a threshold detector connected to the termination for detecting the realtime PWM signal to produce a detected realtime PWM signal;
• a signal processor to obtain material level from the detected realtime PWM signal.

A time domain reflectometer (TDR), comprising:

• a transmit pulse generator for producing transmit pulses at a transmit clock frequency,
• a conductor connected to the transmit pulse generator,
• a transmission line connected to the conductor for conducting transmit pulses to and reflecting transmit pulses from discontinuities along the transmission line at a range to be determined produced by extending the transmission line into a material,
• a termination connected to the conductor to terminate reflected transmit pulses received from the transmission line and to form a realtime PWM signal,
• a sampler connected to generate an expanded-time PWM signal,
• a gating pulse generator connected to the sampler and operating with swept phase relative to the transmit pulses,
• a signal conditioner connected to the sampler for at least one of amplifying or threshold detecting the expanded-time PWM signal;
• a signal processor to obtain material level from the signal conditioned expanded-time PWM signal.

A time domain reflectometer (TDR), comprising:

• a transmit pulse generator for producing transmit pulses at a first frequency,
• a conductor connected to the transmit pulse generator,
• a transmission line connected to the conductor for conducting transmit pulses to and reflecting transmit pulses from discontinuities along the transmission line at a range to be determined produced by extending the transmission line into a material,
• a termination connected to the conductor to terminate reflected transmit pulses received from the transmission line and to form a realtime PWM signal,
• a sampler connected to generate an expanded-time PWM signal,
• a gating pulse generator connected to the sampler and operating at a second frequency that is offset from the first frequency by a floating offset frequency Δ,
• a signal conditioner connected to the sampler for at least one of amplifying or threshold detecting the expanded-time PWM signal;
• a signal processor to obtain material level from the signal conditioned expanded-time PWM signal.