Dual-mode oscillator for stress compensated cut resonator
View Patent ↗Both parallel-type and serial-type dual-mode oscillators employing stress compensated cut resonators having various configurations are disclosed. Both classes of dual-mode oscillators employ multiple tank circuits to pass one frequency of the resonator and block the other frequency. The tank circuits isolate the operation of the two oscillator sub-circuits that form the dual-mode oscillator from one another. The dual-mode oscillators may be implemented with either bipolar or CMOS transistors. The parallel-type dual-mode oscillators employ inverters to provide gain. The serial-type dual-mode oscillators employ a two (or three) stage design including a follower circuit first stage and an inverting amplifier/limiter circuit second stage, with an optional intervening transimpedance amplifier stage.
1. A parallel-type dual-mode oscillator comprising:
a resonator, the resonator adapted to resonate at a lower frequency F 1 and an upper frequency F 2 ;
a first oscillator sub-circuit adapted to operate at the lower frequency F 1 , the first oscillator sub-circuit including:
a first input tank circuit, the first input tank circuit coupled to the resonator, the first input tank circuit adapted to pass the lower frequency F 1 and to block the upper frequency F 2 ;
a first inverter, the first inverter coupled to the first input tank circuit, the first inverter adapted to invert a signal from the first input tank circuit; and
a first output tank circuit, the first output tank circuit coupled to the first inverter and the resonator, the first output tank circuit adapted to pass the lower frequency F 1 and to block the upper frequency F 2 ;
a second oscillator sub-circuit adapted to operate at the upper frequency F 2 , the second oscillator sub-circuit including:
a second input tank circuit, the second input tank circuit coupled to the resonator, the second input tank circuit adapted to pass the upper frequency F 2 and to block the lower frequency F 1 ;
a second inverter, the second inverter coupled to the second input tank circuit, the second inverter adapted to invert a signal from the second input tank circuit; and
a second output tank circuit, the second output tank circuit coupled to the second inverter and the resonator, the second output tank circuit adapted to pass the upper frequency F 2 and to block the lower frequency F 1 ; and
a third tank circuit, the third tank circuit coupled to the resonator in parallel, the third tank circuit in parallel with the resonator adapted to have a capacitive impedance at the lower frequency F 1 and at the upper frequency F 2 .
2. The parallel-type dual-mode oscillator of claim 1 , wherein the first input tank circuit and the first output tank circuit each includes:
a first leg in parallel with a second leg;
wherein the first leg includes in series:
a first capacitor; and
a first inductor; and
wherein the second leg includes in series:
a second capacitor; and
a second resistor.
3. The parallel-type dual-mode oscillator of claim 2 ,
wherein a series combination of the first capacitor and the first inductor is adapted to resonate at the lower frequency F 1 ; and
wherein a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the upper frequency F 2 .
4. The parallel-type dual-mode oscillator of claim 1 , wherein the second input tank circuit and the second output tank circuit each includes:
a first leg in parallel with a second leg;
wherein the first leg includes in series:
a first capacitor; and
a first inductor; and
wherein the second leg includes in series:
a second inductor; and
a second resistor.
5. The parallel-type dual-mode oscillator of claim 4 ,
wherein a series combination of the first capacitor and the first inductor is adapted to resonate at the upper frequency F 2 ; and
wherein a series combination of the first capacitor and the first inductor in parallel with the second inductor is adapted to resonate at the lower frequency F 1 .
6. The parallel-type dual-mode oscillator of claim 4 , wherein the second leg further includes a second capacitor in parallel with the second inductor.
7. The parallel-type dual-mode oscillator of claim 1 , wherein the third tank circuit includes in series:
a first inductor; and
a first resistor.
8. The parallel-type dual-mode oscillator of claim 1 , wherein one or more of the first input tank circuit, the first output tank circuit, the second input tank circuit, or the second output tank circuit includes a trimmable capacitor.
9. The parallel-type dual-mode oscillator of claim 1 , wherein the upper frequency F 2 is within approximately 10% of the lower frequency F 1 or the upper frequency F 2 is an odd integer multiple of the lower frequency F 1 .
10. A serial-type dual-mode oscillator comprising:
a resonator, the resonator adapted to resonate at a lower frequency F 1 and an upper frequency F 2 , a parasitic frequency F 3 corresponding approximately to an average of the lower frequency F 1 and the upper frequency F 2 ;
a first oscillator sub-circuit adapted to operate at the lower frequency F 1 , the first oscillator sub-circuit including:
a first tank circuit, the first tank circuit coupled to the resonator, the first tank circuit adapted to pass the lower frequency F 1 and to block the upper frequency F 2 ;
a first follower circuit, the first follower circuit including a first node coupled to the first tank circuit, a second node, and a third node;
a third tank circuit, the third tank circuit coupled between the second node of the first follower circuit and ground, the third tank circuit adapted to allow amplifier/limiter gain at the lower frequency F 1 and to shunt the parasitic frequency F 3 to ground; and
a first inverting amplifier/limiter circuit, the first inverting amplifier/limiter circuit coupled between the second node of the first follower circuit and the third node of the first follower circuit, the first inverting amplifier/limiter circuit adapted to amplify and limit a signal at the third node of the first follower circuit;
a second oscillator sub-circuit adapted to operate at the upper frequency F 2 , the second oscillator sub-circuit including:
a second tank circuit, the second tank circuit coupled to the resonator, the second tank circuit adapted to pass the upper frequency F 2 and to block the lower frequency F 1 ;
a second follower circuit, the second follower circuit including a first node coupled to the second tank circuit, a second node, and a third node;
a fourth tank circuit, the fourth tank circuit coupled between the second node of the second follower circuit and ground, the fourth tank circuit adapted to allow amplifier/limiter gain at the upper frequency F 2 and to shunt the parasitic frequency F 3 to ground; and
a second inverting amplifier/limiter circuit, the second inverting amplifier/limiter circuit coupled between the second node of the second follower circuit and the third node of the second follower circuit, the second inverting amplifier/limiter circuit adapted to amplify and limit a signal at the third node of the second follower circuit.
11. The serial-type dual-mode oscillator of claim 10 , wherein the first tank circuit and the fourth tank circuit each includes:
a first leg in parallel with a second leg;
wherein the first leg includes in series:
a first capacitor; and
a first inductor; and
wherein the second leg includes in series:
a second capacitor; and
a second resistor.
12. The serial-type dual-mode oscillator of claim 11 ,
wherein, for the first tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the lower frequency F 1 ; and
wherein, for the first tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the upper frequency F 2 .
13. The serial-type dual-mode oscillator of claim 11 ,
wherein, for the fourth tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the parasitic frequency F 3 ; and
wherein, for the fourth tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the upper frequency F 2 .
14. The serial-type dual-mode oscillator of claim 10 , wherein the second tank circuit and the third tank circuit each includes:
a first leg in parallel with a second leg;
wherein the first leg includes in series:
a first capacitor; and
a first inductor; and
wherein the second leg includes in series:
a second inductor; and
a second resistor.
15. The serial-type dual-mode oscillator of claim 14 ,
wherein, for the second tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the upper frequency F 2 ; and
wherein, for the second tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the lower frequency F 1 .
16. The serial-type dual-mode oscillator of claim 14 ,
wherein, for the third tank circuit, a series combination of the first capacitor and the first inductor is adapted to resonate at the parasitic frequency F 3 ; and
wherein, for the third tank circuit, a series combination of the first capacitor and the first inductor in parallel with the second capacitor is adapted to resonate at the lower frequency F 1 .
17. The serial-type dual-mode oscillator of claim 14 , wherein the second leg further includes a second capacitor in parallel with the second inductor.
18. The serial-type dual-mode oscillator of claim 10 ,
wherein each of the first follower circuit and the second follower circuit includes one of a bipolar transistor follower circuit, a metal oxide semiconductor field effect transistor (MOSFET) follower circuit, or a compound-transistor follower circuit; and
wherein the compound-transistor follower circuit includes:
a first MOSFET of a first type adapted to have an M P1 =1;
a second MOSFET of the first type adapted to have an M P2 >1; and
a third MOSFET of a second type opposite the first type.
19. The serial-type dual-mode oscillator of claim 10 ,
wherein the first inverting amplifier/limiter circuit and the second inverting amplifier/limiter circuit each includes a corresponding transimpedance amplifier; and
wherein one or more of the first tank circuit, the second tank circuit, the third tank circuit, or the fourth tank circuit includes a trimmable capacitor.
20. The serial-type dual-mode oscillator of claim 10 , wherein the upper frequency F 2 is within approximately 10% of the lower frequency F 1 or the upper frequency F 2 is an odd integer multiple of the lower frequency F 1 .