Waveform encoded altitude sensor

A waveform encoding altitude sensing apparatus, comprising:

• a radio frequency source,
• a random code generator coupled to said radio frequency source for producing a plurality of unique coded signals and unique radio frequency random code modulated signals,
• first epoch detecting means coupled to the output of said random code generator for detecting a unique epoch chip representative of one of said unique signals and for generating a start epoch signal,
• altitude counting means started by said start epoch signal,
• transmitting means for transmitting said unique modulated signals,
• receiving means for receiving returned delayed and attenuated reflected signals,
• mixer means coupled to said receiver means and said radio frequency source for producing demodulated received signals and phase shifted demodulated received signals,
• power detector means comprising an early, an edge and a later power detector,
• each said detector being coupled to said demodulated signals from said mixer means for recovering the demodulated returned signals,
• tracking code generator means adapted to track said returned demodulated signals,
• delay means in the output of said tracking code generator for producing an output indicative of an early chip time, an edge chip time and a late chip time,
• said early, edge and late chip time outputs being coupled to said early, edge and late power detectors respectively for detecting the power outputs representative of early, edge and late power correlation respectively,
• summing circuit means coupled to said power detecting means for determining when the maximum predetermined power correlation exists between said edge chip time output from said delay means and said demodulated signals from said mixer means,
• voltage controlled oscillator means coupled to said summing circuit means for speeding up or slowing down said tracking code generator means, and
• second epoch detector means coupled to said tracking code generator means for detecting said unique epoch chip and for generating a stop epoch signal adapted to stop said altitude counting means, whereby said altitude count is indicative of a sensed altitude.

The method of measuring altitude employing a spread spectrum carrier wave generated signal, comprising the steps of:

• generating a random code modulated signal by modulating a random code signal with a carrier wave signal,
• detecting a unique chip in said random code and startng an altitude counter,
• transmitting said random code modulated signals, receiving a delayed reflected version of said transmitted signal,
• demodulating said delayed reflected received signals, applying said demodulated reflected signals to a plurality of power detectors,
• generating a random code tracking signal,
• delaying said random code tracking signals with a tapped delay to produce an early chip time output, an edge chip time output and a late chip time output,
• applying said early, edge and late chip time outputs to one of said plurality of said power detectors,
• logically summing the power sensed by said power detectors to determine if said random code tracking signal is early or late relative to said received demodulated signal,
• generating a correction signal for speeding up or slowing down said random code tracking signals,
• detecting said unique chip in said random code of said random code tracking signals, and
• stopping said altitude counter when said unique chip in said random code tracking signals is detected, whereby said altitude count is indicative of a sensed altitude.