Oscillator mode suppression apparatus having bandpass effect

• US 4,378,532 A
• Filed: 08/27/1981
• Issued: 03/29/1983
• Est. Priority Date: 04/02/1979
• Status: Expired due to Term

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Burgoon, John R.
• Primary Examiner(s): Moore, David K.
• Application Number:
  US06/296,746
• Time in Patent Office: 579 Days
• Field of Search: 331/117 R, 331/116 R, 331/158, 331/159, 331/160, 331/164
• US Class Current: 331/158
• CPC Class Codes: H03B 2200/0012 Pierce oscillator
• CPC Class Codes: H03B 5/32 being a piezoelectric resonator selection of piezoelectric material H10N30/00

Abstract

An apparatus utilizing the basic oscillation characteristics of the Colpitts or Pierce and Hartley oscillator configurations. In this embodiment the basic shunt reactive shunt arms are replaced with a selected pair of tank circuits or one of the shunt arms with a series-parallel tank circuit.

These tank circuits are tuned such that the sign of their effective reactances are the same between the range of resonant frequencies of the individual tank circuits or of the series and parallel resonant frequencies of the series-parallel tank. When this occurs and their sign differs from the sign of the effective reactance of the series reactive element, there is a 180° signal phase shift in the feedback loop, and therefore oscillation.

Claims

1. Signal Oscillator with mode suppression apparatus for limiting the frequencies of oscillation to a selected band of frequencies, said apparatus comprising:

inverting amplifier means having an input terminal and an output terminal; and

signal feedback means for providing a 180°

phase shift in the selected band of frequencies, said signal feedback means including;

crystal resonator means connected in series between the input and output terminals of the inverting amplifier means for producing a relatively stable oscillator output signal; and

first and second shunt reactive means for suppressing oscillation outside the selected band of frequencies, said first shunt reactive means having one end connected to the input terminal of the inverting amplifier means, said second shunt reactive means having one end connected to the output terminal of the inverting amplifier means, the other ends of the first and second shunt reactive means being connected one to the other;

at least one of said first and second shunt reactive means having a resonant tank circuit, said resonant tank circuit having a reactance value such that for each frequency outside the selected band of frequencies at least one of said first and second shunt reactive means has reactance value of the same sign as the reactance value of the crystal resonator means.

2. Signal oscillator with mode suppression apparatus as in claim 1 wherein one of said first and second shunt reactive means includes a parallel resonant tank and the other of said first and second shunt reactive means includes a series resonant tank.

3. Signal oscillator with mode suppression apparatus as in claim 2 wherein:

said parallel resonant tank has a resonant frequency, f₁, and said parallel tank has a negative reactance above f₁ and a positive reactance below f₁ ; and

said series resonant tank has a resonant frequency, f₂, and said series tank has a positive reactance above f₂ and a negative reactance below f₂ ;

said resonant frequencies f₁ and f₂ defining said selected band of frequencies.

4. Signal oscillator with mode suppression apparatus as in claim 3 wherein f₁ is selected to be less than f₂ causing said crystal resonator means to assume a positive reactance value between f₁ and f₂ and the oscillator to operate in a Colpitts configuration between frequencies f₁ and f₂.

5. Signal oscillator with mode suppression apparatus as in claim 3 wherein f₂ is selected to be less than f₁ causing said crystal resonator means to assume a negative reactance value between f₂ and f₁ and the oscillator to operate in the Hartley configuration between frequencies f₂ and f₁.

6. Signal oscillator with mode suppression apparatus as in claim 1 wherein:

one of said first and second shunt reactive means includes a tank circuit having a series resonant path and a parallel resonant path; and

the other of said first and second shunt reactive means includes a first non-resonant reactive circuit;

a tank circuit configured as above defined has a series resonant frequency and a parallel resonant frequency, these frequencies defining the band of frequencies between which oscillation is possible.

7. Signal oscillator with mode suppression apparatus as in claim 6 wherein the tank circuit comprises a series resonant reactive circuit path in parallel with a second non-resonant reactive circuit path.

8. Signal oscillator with mode suppression apparatus as in claim 7 wherein the series resonant reactive circuit path comprises an inductor connected in series with a capacitor.

9. Signal oscillator with mode suppression apparatus as in claim 8 wherein:

said second non-resonant reactive circuit path comprises an inductor; and

said first non-resonant reactive circuit comprises a capacitor.

10. Signal oscillator with mode suppression apparatus as in claim 9 wherein:

said second non-resonant reactive circuit path comprises a capacitor; and

said first non-resonant reactive circuit comprises an inductor.

11. Signal oscillator with mode suppression apparatus as in claim 6 wherein the tank circuit comprises a parallel resonant reactive circuit path in series with a second non-resonant reactive circuit path.

12. Signal oscillator with mode suppression apparatus as in claim 11 wherein the parallel resonant reactive circuit path comprises an inductor connected in parallel with a capacitor.

13. Signal oscillator with mode suppression apparatus as in claim 12 wherein:

said second non-resonant reactive circuit path comprises an inductor; and

said first non-resonant reactive circuit comprises a capacitor.

14. Signal oscillator with mode suppression apparatus as in claim 13 wherein:

said second non-resonant reactive circuit path comprises a capacitor; and

said first non-resonant reactive circuit comprises an inductor.