Blood pressure monitor

1. A blood pressure monitor comprising:

a cuff to be worn around an arm of a human subject;

a microwave transmitting unit for radiating a microwave onto said human subject;

a microwave receiving unit for receiving a reflected wave Doppler-shifted relative to said radiated microwave due to a heartbeat of said subject; and

a correct position detector for detecting, based on said reflected wave, whether said cuff is located in a correct position relative to a position of the heart of said human subject,

said correct position detector including,

a first movement detector for detecting a first moving state in which said cuff is being moved toward a front part of a chest of said subject, based on an amplitude of a phase difference signal representing a phase difference between a transmitted microwave signal corresponding to said microwave radiated by said microwave transmitting unit and a received microwave signal corresponding to said reflected wave received by said microwave receiving unit, and

a second movement detector for detecting a second moving state in which said cuff is being moved toward said correct position on the front part of said chest, based on signal frequency components of said phase difference signal.

2. The blood pressure monitor according to claim 1 , wherein after it is determined by said first movement detector that said first moving state is completed, said second movement detector detects said second moving state.

3. The blood pressure monitor according to claim 2 , wherein said first movement detector detects said first moving state by detecting from said phase difference signal any signal whose amplitude exceeds a prescribed amplitude range, and

said second movement detector performs Fourier transform processing by accumulating over a predetermined time interval said phase difference signal whose amplitude does not exceed said prescribed amplitude range, extracts a fundamental wave of signal components, and detects said second moving state by extracting, as a pulse wave, signal components of said fundamental wave that fall within a prescribed frequency range.

4. The blood pressure monitor according to claim 3 , wherein said first movement detector includes an AD converter for converting said phase difference signal into digital form for output, and a signal saturation state detector,

said AD converter converts said phase difference signal into a digital signal by sampling said phase difference signal based on first time information, and

said signal saturation state detector counts, based on said digital signal, the number of occurrences of amplitude saturation exceeding said prescribed amplitude range bounded by a first saturation threshold value and a second saturation threshold value, wherein when the number of occurrences of said amplitude saturation is larger than a predetermined number, it is determined that said first moving state is in progress and, when the number of occurrences of said amplitude saturation decreases to zero after it is determined that said first moving state is in progress, it is determined that said first moving state is completed; and

said second movement detector includes an FFT unit for performing said Fourier transform processing, and a pulse wave detector,

said FFT unit performs said Fourier transform processing by accumulating said digital signal over said predetermined time interval based on second time information, and thereby extracts said fundamental wave of signal components, and

said pulse wave detector, based on said fundamental wave, extracts as said pulse wave said signal components that fall within said prescribed frequency range bounded by a first frequency threshold value and a second frequency threshold value, and determines, upon detection of said pulse wave, that said cuff has been moved to said correct position.

5. The blood pressure monitor according to claim 4 , wherein said second movement detector further includes a blood pressure measurement determining unit for determining whether said cuff is located in said correct position, and a blood pressure measuring unit, and

when it is determined by said blood pressure measurement determining unit that said cuff has been moved to said correct position, said blood pressure measuring unit starts blood pressure measurement.

6. The blood pressure monitor according to claim 5 , further comprising:

a timer;

a memory; and

an alarm for annunciating information by means of a display, sound, light, vibration, or a combination thereof, and

wherein date/time information obtained from said timer, information related to said pulse wave, and a result of said blood pressure measurement are stored in said memory, and contents stored in said memory are annunciated by using said alarm.

7. The blood pressure monitor according to claim 6 , wherein when it is determined by said blood pressure measurement determining unit that said cuff has been moved to said correct position, said alarm annunciates that said cuff is located in said correct position.

8. The blood pressure monitor according to claim 6 , wherein said second movement detector extracts respiration information from said phase difference signal when detecting said second moving state, and stores said respiration information in said memory along with said date/time information obtained from said timer, said information related to said pulse wave, and the result of said blood pressure measurement.

9. The blood pressure monitor according to claim 4 , wherein if said cuff is displaced from said correct position after said blood pressure measurement has been started, said blood pressure measuring unit stops said blood pressure measurement.