Self-oscillating burst mode transmitter with integral number of periods

• US 4,980,898 A
• Filed: 08/08/1989
• Issued: 12/25/1990
• Est. Priority Date: 08/08/1989
• Status: Expired due to Term

• Current Assignee: Pacesetter Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Siemens Pacesetter, Inc. (Abbott Laboratories Incorporated)
• Inventors: Silvian, Sergiu
• Primary Examiner(s): Safourek, Benedict V.
• Assistant Examiner(s): Tse, Young
• Application Number:
  US07/391,077
• Time in Patent Office: 504 Days
• Field of Search: 375/3, 375/4, 375/59, 375/68, 375/71, 331/165, 331/166, 178/70 TS, 178/71 M, 128/419 P, 128/419 PG, 128/422
• US Class Current: 375/295
• CPC Class Codes: H03B 11/10 interrupter being semiconductor device
• CPC Class Codes: H03B 5/1221 the amplifier comprising multiple amplification stages connected in cascade
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H04B 2001/0491 with frequency synthesizers, frequency converters or modulators

Abstract

A self-oscillating burst mode transmitter transmits an integral number of cycles of a carrier signal in each transmission burst. Each burst commences at a peak value of the carrier signal and terminates at a peak value. The transmitter includes an L-C tank circuit comprising a transmitting coil (L1) connected to a capacitor (C4). The L-C tank circuit is selectively energized through a switching network (Q1, Q2, U1, U2) connected to a power source, causing the tank circuit to resonate at a prescribed frequency (f₀). Selective energization of the tank circuit is achieved by the switching network as controlled by a peak voltage detection circuit (32, 34). The peak detection circuit senses when a peak voltage is present in the oscillatory waveform appearing across the coil of the resonating tank circuit. Power is switched off to the tank circuit at the conclusion of each transmission burst only when the oscillatory voltage waveform, as sensed by the peak detection circuit, is at a peak. This peak voltage is stored by the capacitor of the tank circuit during the time the power source is not connected to the tank circuit. At the beginning of the next transmission burst, when power is again coupled to the tank circuit through the switching network, the voltage initially appearing across the coil, and hence the voltage at the commencement of the next oscillatory waveform of the transmission burst, begins at the peak voltage value stored on the capacitor.

Claims

1. A self-oscillating burst mode transmitter comprising:

an L-C tank circuit, said L-C tank circuit including a transmitting coil connected to a capacitor;

switch means responsive to a control signal for switchably connecting an energy source to said L-C tank circuit, whereby said L-C tank circuit oscillates at a resonant frequency, an oscillatory voltage waveform being developed across said transmitting coil and capacitor as said tank circuit oscillates;

phase shift means coupled to said transmitting coil for generating an output voltage signal having the same frequency as said oscillatory voltage waveform, but having a phase angle that is shifted from the phase angle of said oscillatory voltage waveform by a prescribed amount;

comparator means coupled to said phase shift means for comparing the amplitude of the output voltage signal generated by said phase shift means with a reference signal, and for generating thereby said control signal which changes in value as a function of whether the amplitude of said output voltage signal is less than or greater than said reference signal, whereby the value of said control signal changes upon the occurrence of a prescribed voltage value of the oscillatory waveform; and

inhibiting means coupled to said comparator means, for selectively blocking the delivery of said control signal to said switch means at a time within a cycle of said oscillatory voltage waveform when the voltage appearing across said transmitting coil and capacitor is at the prescribed voltage value, the capacitor of said L-C tank circuit storing said prescribed voltage value until such time as said control signal is no longer inhibited;

said tank circuit starting its next oscillatory cycle when not inhibited by said inhibiting means with the voltage waveform across the transmitter coil at said stored prescribed voltage value, and stopping its oscillatory cycle with the voltage waveform across the transmitter coil at a corresponding prescribed voltage value, an integral number of periods of said oscillating voltage waveform occurring between the time said oscillatory cycle starts and stops.

2. The burst mode transmitter as set forth in claim 1 wherein said switch means comprises a first transistor switch that selectively connects said L-C tank circuit to a first polarity of a power source in response to one state of said control signal, and a second transistor switch that selectively connects said L-C tank circuit to a second polarity of said power source in response to the other state of said control signal.

3. The burst mode transmitter as set forth in claim 2 wherein said phase shift means comprises a circuit that differentiates the oscillatory voltage waveform, thereby causing said output voltage waveform to assume a waveform representative of the derivative of the oscillatory voltage waveform, said output voltage waveform being shifted in phase relative to said oscillatory voltage waveform by approximately 90 degrees.

4. The burst mode transmitter as set forth in claim 3 wherein the reference signal against which the amplitude of the output voltage signal is compared comprises a zero volt reference signal, whereby said comparator means functions as a zero crossing detector of said output voltage signal, said zero crossings corresponding to peaks in said oscillatory voltage waveform.

5. The burst mode transmitter as set forth in claim 4 wherein said inhibiting means comprise first and second logic gates connected to control said first and second transistor switches, respectively, each of said logic gates having an enabling signal applied thereto generated by a flip flop, said logic gates and flip flop being configured so as to prevent said first and second transistor switches from being turned on at the same time, yet allowing said transistor switches to both be turned off at the same time.

6. The burst mode transmitter as set forth in claim 5 wherein said flip flop is clocked by said control signal generated by said comparator means, which clock signal changes levels coincident with the occurrence of a peak in said oscillatory voltage waveform, a transition from a first level to a second level of said control signal occurring in response to a positive peak in said oscillatory voltage waveform, and a transition from the second level to the first level of said control signal occurring in response to a negative peak in said oscillatory voltage waveform, said flip flop being configured to assume the state of a data input signal in synchrony with a prescribed transition of a clock signal applied thereto, an ON/OFF enabling signal being applied to said flip flop as said data input, said flip flop thereby assuming a first state in synchrony with the occurrence of a prescribed peak of said oscillatory voltage waveform when said ON/OFF enabling signal is at a high level, and assuming a second state in synchrony with the occurrence of said prescribed peak of said oscillatory voltage waveform when said ON/OFF enabling signal is at a low level, said first state of said flip flop causing said first and second logic gates to be enabled.

7. The burst mode transmitter as set forth in claim 6 wherein said flip flop is further configured to assume said first state immediately in response to said ON/OFF control signal changing to a high level, and said flip flop assumes said second state in synchrony with the occurrence of said prescribed peak of said oscillatory waveform only after said ON/OFF control signal changes to a low level.

8. A self-oscillating burst mode transmitter comprising:

a tank circuit;

switch means responsive to a control signal for switchably connecting an energy source to said tank circuit, whereby said tank circuit oscillates at a resonant frequency, an oscillatory signal being developed across said tank circuit as said tank circuit oscillates;

peak detection means for generating said control signal as a function of when the peaks within said oscillatory signal occur; and

inhibiting means for selectively inhibiting the delivery of said control signal to said switch means coincident with the occurrence of the peaks within said oscillatory signal, said tank circuit including means for storing the energy associated with the peak signal until such time as said control signal is no longer inhibited;

said tank circuit starting its next oscillatory cycle when not inhibited by said inhibiting means at a peak signal corresponding to the energy previously stored in said tank circuit, and stopping its oscillatory cycle when the oscillatory signal across the tank circuit is at a corresponding peak value, an integral number of periods of said oscillating signal thereby occurring between the time said oscillatory cycle starts and stops.

9. The burst mode transmitter as set forth in claim 8 wherein said peak detection means comprises:

a differentiator circuit for differentiating the oscillatory signal; and

a zero crossing detector for sensing each zero crossing of the differentiated oscillatory signal and for generating said control signal as a function of said sensed zero crossings, said control signal including a transition from one level to another for each sensed zero crossing of the differentiated oscillatory signal.

10. The burst mode transmitter as set forth in claim 8 further including means for programmably setting the number of integral periods of said oscillating signal occurring between the time said oscillatory cycle starts and stops.

11. A burst mode integral period oscillator comprising:

a tank circuit including a transmitting coil connected to a capacitor;

switch means for delivering power to said tank circuit, said tank circuit oscillating at a resonant frequency in response to said delivered power, an oscillatory voltage waveform being developed across said transmitting coil and capacitor as said tank circuit oscillates;

sensing means for sensing when said oscillatory voltage waveform is at a peak value; and

inhibiting means synchronized with said sensing means for selectively stopping the delivery of said power to said tank circuit at a time when the oscillatory voltage waveform developed across said transmitting coil and capacitor is at a peak voltage value, the capacitor of said tank circuit storing this peak voltage value until said inhibiting means again allows power to be delivered to said tank circuit, at which time said tank circuit again begins to oscillate at said resonant frequency, the oscillatory voltage waveform beginning at said peak voltage value stored by said capacitor;

said tank circuit thereby starting an oscillatory cycle as allowed by said inhibiting means at a time in an oscillatory cycle of said oscillatory voltage waveform when the voltage waveform across the transmitter coil is at a first peak value, and said tank circuit stopping said oscillatory cycle as controlled by said inhibiting means at a time in the oscillatory cycle when the voltage waveform across the transmitter coil is at a second peak value, an integral number of periods of said oscillating voltage waveform occurring between said first and second peak values.

12. The integral period oscillator as set forth in claim 11 wherein said sensing means comprises

phase-shifting means for shifting the phase of said oscillatory waveform by a prescribed amount;

and

threshold means for sensing when the amplitude of the phase-shifted oscillatory waveform exceeds a prescribed threshold value.

13. The integral period oscillator as set forth in claim 12 wherein the prescribed amount by which the phase of said oscillatory waveform is shifted by said phase-shifting means comprises approximately 90 degrees, and further wherein said prescribed threshold value of said threshold means comprises approximately zero volts.

14. The integral period oscillator as set forth in claim 12 wherein said phase shifting means comprises a differentiator circuit that differentiates said oscillatory waveform.

15. The integral period oscillator as set forth in claim 11 further including means for programmably setting the number of integral periods of said oscillatory voltage waveform that occur between said first and second peak values.

16. A method of controlling a burst mode oscillator so that each burst contains an integral number of cycles, said oscillator including a tank circuit that generates an oscillatory waveform having a prescribed frequency upon being energized with power from an external power source, said method comprising:

(a) energizing said tank circuit with said power when a first burst of oscillations is desired;

(b) sensing when the oscillatory waveform associated with said energized tank circuit is at a peak value;

(c) selectively inhibiting the delivery of power to said tank circuit at the conclusion of said first burst of oscillations at a point within a cycle of the oscillatory waveform when the oscillatory waveform sensed in step (b) is at a prescribed value;

(d) storing the energy associated with the prescribed value of the oscillatory waveform during the time when said tank circuit is inhibited; and

(e) starting the oscillatory waveform of said tank circuit, when next energized at the beginning of a second burst of oscillations, at the prescribed value stored within said tank circuit in step (d).

17. The method set forth in claim 16 wherein step (b) comprises shifting the phase of the oscillatory waveform by a prescribed amount and sensing when the amplitude of the resulting phase-shifted signal exceeds a prescribed threshold.

18. The method set forth in claim 17 wherein the step of shifting the phase of the oscillatory waveform by a prescribed amount comprises shifting the phase by approximately 90 degrees, and sensing when the amplitude of the resulting phase-shifted signal is greater than zero.

19. The method set forth in claim 16 wherein the prescribed value of the oscillatory waveform at which the delivery of power to said tank circuit is inhibited at the conclusion of said first burst of oscillations comprises a peak value.

20. The method set forth in claim 16 further including:

counting the number of oscillations of said oscillatory waveform, determining if the counted oscillations equal a prescribed number of oscillations, and inhibiting the delivery of power to said tank circuit in accordance with step (c) only if the counted oscillations equals the prescribed number of oscillations.