CW and pulsed doppler diagnostic system

A frequency to voltage converter comprising

• an input circuit for receiving a stream of pulses with either fixed or variable time intervals between pulses,
• timing means coupled to said input circuit for receiving pulses of said stream of pulses and responsive to the receipt of each of said pulses for charging a capacitor,
• a discharge circuit connected to said capacitor and having a discharge characteristic that varies as an inverse function of time, and
• an output circuit,
• said timing means comprising means responsive to the receipt of each pulse by said input circuit for applying the voltage across said capacitor to said output circuit substantially immediately prior to said charging of said capacitor and means for inhibiting the application of the voltage across said capacitor to said output circuit between the time of application of voltage across said capacitor and the occurrence of the next pulse of said stream of pulses, whereby the output of said output circuit comprises a voltage proportional to the frequency of said pulses.

A system for indicating the frequency spectrum of Doppler shift frequencies of fluid flow, comprising

• means for producing a pulse train of pulses having an instantaneous frequency related to Doppler shift frequency of flowing fluid;
• means for producing a voltage that varies as an inverse function of the time interval between the pulses of the pulse train of pulses applied thereto,
• an output circuit,
• first means responsive to the pulses of said stream of pulses for sampling the voltage output of said voltage producing means,
• second means responsive to the pulses of said stream of pulses for applying input pulses to said voltage producing means subsequent to the sampling thereof by said first means;
• and
• timing means comprising means for applying the voltage output of said voltage producing means to said output circuit substantially immediately prior to the application of input pulses to said voltage producing means by said second means,
• said first means comprising means for inhibiting the sampling of said voltage output between the time of application of said input pulses to said voltage producing means and the occurrence of the next pulse of said stream of pulses,
• whereby the output of said output circuit comprises a signal corresponding to the frequency spectrum of Doppler shift frequencies of said fluid flow.

A system for indicating the frequency spectrum of Doppler shift frequencies of fluid flow, comprising

• means for producing a first pulse train of pulses having an instantaneous frequency related to Doppler shift frequency of fluid flowing in a first direction;
• means for producing a second pulse train of pulses having an instantaneous frequency related to Doppler shift frequency of flowing fluid flowing in a second direction different from said first direction;
• whereby pulses of said first and second pulse trains do not occur simultaneously;
• first and second means for producing a voltage that varies as an inverse function of the time interval between the pulses applied thereto,
• an output circuit,
• first timing means for applying the outputs of said first and second pulse producing means to said output circuit in response to each pulse of said first and second pulse trains;
• and
• second timing means for applying a predefined pulse to said first and second voltage producing means in response to each pulse of said first and second train of pulses, respectively, subsequent the application of the output of the respective voltage producing means to said output circuit by said first timing means;
• whereby the output of said output circuit comprises a signal corresponding to the frequency spectrum of Doppler shift frequencies of said fluid flow.