Digitally Controlled Injection Locked Oscillator

• US 20140266480A1
• Filed: 03/15/2013
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Innophase, Inc.
• Original Assignee: Innophase, Inc.
• Inventors: Li, Xi, Xu, Yang
• Granted Patent: US 9,024,696 B2
• Time in Patent Office: Days
• US Class Current: 331/117.FE
• CPC Class Codes: H03B 2200/007 Generation of oscillations based on harmonic frequencies, e.g. overtone oscillators
• CPC Class Codes: H03B 2200/0074 Locking of an oscillator by injecting an input signal directly into the oscillator
• CPC Class Codes: H03B 2201/0208 the means being an element with a variable capacitance, e.g. capacitance diode
• CPC Class Codes: H03B 2201/0291 and being controlled by a processing device, e.g. a microprocessor
• CPC Class Codes: H03B 5/1215 the current source or degeneration circuit being in common to both transistors of the pair, e.g. a cross-coupled long-tailed pair
• CPC Class Codes: H03B 5/1228 the amplifier comprising one or more field effect transistors
• CPC Class Codes: H03B 5/1243 the means comprising voltage variable capacitance diodes
• CPC Class Codes: H03B 5/1265 switched capacitors
• CPC Class Codes: H03D 3/22 by means of active elements with more than two electrodes to which two signals are applied derived from the signal to be demodulated and having a phase difference related to the frequency deviation, e.g. phase detector

Abstract

An injection locking oscillator (ILO) comprising a tank circuit having a digitally controlled capacitor bank, a cross-coupled differential transistor pair coupled to the tank circuit, at least one signal injection node, and at least one output node configured to provide an injection locked output signal; a digitally controlled injection-ratio circuit having an injection output coupled to the at least one signal injection node, configured to accept an input signal and to generate an adjustable injection signal applied to the at least one injection node; and, an ILO controller connected to the capacitor bank and the injection-ratio circuit configured to apply a control signal to the capacitor bank to adjust a resonant frequency of the tank circuit and to apply a control signal to the injection-ratio circuit to adjust a signal injection ratio.

Claims

1. An apparatus comprising:

an injection locking oscillator (ILO) comprising a tank circuit having a digitally controlled capacitor bank, a cross-coupled differential transistor pair coupled to the tank circuit, at least one signal injection node, and at least one output node configured to provide an injection locked output signal;

a digitally controlled injection-ratio circuit having an injection output coupled to the at least one signal injection node, configured to accept an input signal and to generate an adjustable injection signal applied to the at least one injection node; and

,

an ILO controller connected to the capacitor bank and the injection-ratio circuit configured to apply a control signal to the capacitor bank to adjust a resonant frequency of the tank circuit and to apply a control signal to the injection-ratio circuit to adjust a signal injection ratio.

2. The apparatus of claim 1 wherein the at least one injection node is a pair of differential mode injection nodes.

3. The apparatus of claim 1 wherein the at least one injection node is a common mode injection node.

4. The apparatus of claim 1 wherein the injection-ratio circuit has a plurality of parallel stages connected to the controller for providing the adjustable injection signal.

5. The apparatus of claim 4 wherein the parallel stages comprises a variable transconductance amplifier stage.

6. The apparatus of claim 5 wherein the variable transconductance stage includes at least some transconductance stages providing different amounts of gain. (corresponding to binary code and thermometer code)

7. The apparatus of claim 4 wherein the parallel stages comprise a plurality of parallel injection transistors.

8. The apparatus of claim 1 wherein the injection-ratio circuit includes a bias current adjustment circuit. (bias adjustment is parallel devices to alter current, or bias voltage adjustment)

9. The apparatus of claim 1 wherein the at least one injection node comprises a common mode injection node and a pair of differential mode injection nodes, the apparatus further comprising a digitally controlled injection node selection circuit configured to selectably apply the adjustable injection signal to either the common mode injection node or to the pair of differential mode injection nodes.

10. The apparatus of claim 1 wherein the ILO controller comprises a frequency detector configured to determine a resonant frequency, wherein the controller adjusts the capacitors to adjust a free-running frequency of the ILO.

11. The apparatus of claim 10 wherein the frequency detector comprises configurable counters. (the configuration changes the characteristics of the control loop)

12. The apparatus of claim 1 wherein a quality factor of the ILO is adjusted by altering a resistive component of the tank circuit.

13. The apparatus of claim 1 further comprising:

a mixer having inputs configured to accept the input signal and the injection locked output signal, and configured to provide an output signal at a mixer output node; and

,

a control circuit for adjusting a ILO delay characteristic between the input signal and the injection locked output signal based on the output signal at the mixer output node.

14. A method comprising:

adjusting a digitally controlled capacitor bank of a tank circuit in an injection locking oscillator (ILO);

adjusting an ILO injection ratio using a digitally controlled injection-ratio circuit; and

,

measuring the performance of the ILO and responsively adjusting either the capacitor bank or the injection ratio.

15. The method of claim 14 further comprising adjusting a digitally controlled resistor bank of the tank circuit.

16. The method of claim 14 wherein measuring the performance of the ILO comprises measuring a free-running frequency of the ILO.

17. The method of claim 14 wherein measuring the performance of the ILO comprises:

generating a mixer output by mixing an input of the ILO and an output of the ILO; and

,

measuring a DC offset component of the mixer output.

18. An apparatus comprising:

an injection locking oscillator (ILO) comprising a tank circuit having a digitally controlled capacitor bank, a cross-coupled differential transistor pair coupled to the tank circuit, at least one common mode signal injection node and at least one differential mode signal injection node, and at least one output node configured to provide an injection locked output signal;

an injection node selection circuit configured to apply an injection signal having a center frequency f_c to either the at least one common mode injection node or at least one differential mode injection node; and

,

an ILO controller circuit connected to the digitally controlled capacitor bank and to the injection node selection circuit, and configured to either (i) cause the injection node selection circuit to apply the injection signal to a common mode injection node and to apply a control signal to the capacitor bank to adjust a resonant frequency of the tank circuit to be approximately f_c or (ii) cause the injection node selection circuit to apply the injection signal to differential mode injection node and to apply a control signal to the capacitor bank to adjust a resonant frequency of the tank circuit to be approximately f_c/2.

19. The apparatus of claim 18 wherein an ILO controller circuit is a finite state machine.

20. The apparatus of claim 18 further comprising an injection-ratio circuit configured to adjust a signal injection ratio, and wherein the ILO controller circuit is connected to the injection-ratio circuit and is configured to adjust a signal injection ratio.