Injection locking oscillator with phase rotation capability
A system includes an oscillator and an injection circuit coupled to the oscillator. The injection circuit includes a first injection branch coupled to a node, wherein the first injection branch is configured to receive a first clock signal and generate a first injection current based on the first clock signal. The injection circuit also includes a second injection branch coupled to the node, wherein the second injection branch is configured to receive a second clock signal and generate a second injection current based on the second clock signal, and wherein the first injection current and the second injection current are combined at the node.
1 . A system, comprising:
an oscillator; and
an injection circuit coupled to the oscillator, wherein the injection circuit comprises:
a first injection branch coupled to a node, wherein the first injection branch comprises:
a first input circuit configured to receive a first clock signal and generate a first injection current based on the first clock signal; and
a first strength control circuit coupled between the node and the first input circuit, wherein the first strength control circuit is configured to set a strength of the first injection current based on a first control code; and
a second injection branch coupled to the node, wherein the second injection branch comprises:
a second input circuit configured to receive a second clock signal and generate a second injection current based on the second clock signal, wherein the first clock signal and the second clock signal are phase offset from one another by 45 degrees; and
a second strength control circuit coupled between the node and the second input circuit, wherein the second strength control circuit is configured to set a strength of the second injection current based on a second control code, and wherein the first injection current and the second injection current are combined at the node.
2 . The system of claim 1 ,
wherein the first control code and the second control code are complementary.
3 . The system of claim 1 , wherein the oscillator includes a first stage and a second stage, and the node is coupled between an output of the first stage and an input of the second stage.
4 . The system of claim 1 , wherein the first input circuit comprises a first input transistor, wherein a gate of the first input transistor is configured to receive the first clock signal, and wherein
the first strength control circuit is coupled between the node and a drain of the first input transistor.
5 . The system of claim 4 , wherein the second input circuit comprises a second input transistor, wherein a gate of the second input transistor is configured to receive the second clock signal, and wherein
the second strength control circuit is coupled between the node and a drain of the second input transistor.
6 . The system of claim 5 , wherein the first control code and the second control code are complementary.
7 . The system of claim 5 , wherein the first strength control circuit comprises:
first transistors coupled in parallel between the node and the drain of the first input transistor; and
a first controller configured to control a number of the first transistors that are turned on based on the first control code.
8 . The system of claim 7 , wherein the second strength control circuit comprises:
second transistors coupled in parallel between the node and the drain of the second input transistor; and
a second controller configured to control a number of the second transistors that are turned on based on the second control code.
9 . The system of claim 8 , wherein the first control code and the second control code are complementary.
10 . The system of claim 5 , wherein a source of the first input transistor is coupled to a ground, and a source of the second input transistor is coupled to the ground.
11 . The system of claim 10 , wherein the first input transistor comprises a first n-type field effect transistor (NFET) and the second input transistor comprises a second NFET.
12 . A system, comprising:
an oscillator; and
a first injection circuit coupled to the oscillator, wherein the first injection circuit comprises:
a first multiplexer configured to receive multiple clock signals, select a first clock signal and a second clock signal from among the multiple clock signals, and output the first clock signal and the second clock signal;
a first injection branch coupled to a first node, wherein the first injection branch is configured to receive the first clock signal from the first multiplexer and generate a first injection current based on the first clock signal; and
a second injection branch coupled to the first node, wherein the second injection branch is configured to receive the second clock signal from the first multiplexer and generate a second injection current based on the second clock signal, and wherein the first injection current and the second injection current are combined at the first node; and
a second injection circuit coupled to the oscillator, wherein the second injection circuit comprises:
a second multiplexer configured to receive the multiple clock signals, select a third clock signal and a fourth clock signal from among the multiple clock signals, and output the third clock signal and the fourth clock signal, wherein the first clock signal, the second clock signal, the third clock signal, and the fourth clock signal are phase offset from one another;
a third injection branch coupled to a second node, wherein the third injection branch is configured to receive the third clock signal from the second multiplexer and generate a third injection current based on the third clock signal; and
a fourth injection branch coupled to the second node, wherein the fourth injection branch is configured to receive the fourth clock signal from the second multiplexer and generate a fourth injection current based on the fourth signal, and wherein the third injection current and the fourth injection current are combined at the second node.
13 . The system of claim 12 , wherein the first node and the second node are coupled to different nodes of the oscillator.
14 . The system of claim 12 , wherein the multiple clock signals are phase offset from one another.
15 . The system of claim 14 , wherein the multiple clock signals are phase offset from one another by 45 degrees.
16 . The system of claim 12 , further comprising a multiphase generator configured to receive one or more input clock signals, generate the multiple clock signals based on the one or more input clock signals, and output the multiple clock signals to the multiplexer.
17 . The system of claim 16 , wherein the one or more input clock signals comprise complementary clock signals.
18 . A system, comprising:
an oscillator; and
an injection circuit coupled to the oscillator, wherein the injection circuit comprises:
a first injection branch coupled to a node, wherein the first injection branch comprises:
a first input circuit configured to receive a first clock signal and generate a first injection current based on the first clock signal; and
a first strength control circuit coupled between the node and the first input circuit; and
a second injection branch coupled to the node, wherein the second injection branch comprises:
a second input circuit configured to receive a second clock signal and generate a second injection current based on the second clock signal; and
a second strength control circuit coupled between the node and the second input circuit, wherein the first injection current and the second injection current are combined at the node to obtain a combined injection current, and wherein the first strength control circuit and the second strength control circuit are configured to adjust the first injection current and the second injection current, respectively, in opposite directions to adjust a phase of the combined injection current.
19 . The system of claim 18 , wherein:
the first strength control circuit comprises:
first transistors coupled in parallel between the node and the first input circuit; and
a first controller configured to control a number of the first transistors that are turned on;
the second strength control circuit comprises:
second transistors coupled in parallel between the node and the second input circuit; and
a second controller configured to control a number of the second transistors that are turned on such that a total number of the first transistors and the second transistor that are turned on is constant across phase rotations of the combined injection current.
20 . The system of claim 18 , wherein the oscillator includes a first stage and a second stage, and the node is coupled between an output of the first stage and an input of the second stage.
21 . The system of claim 18 , wherein the first clock signal and the second clock signal are phase offset from one another by 45 degrees.
22 . The system of claim 18 , wherein:
the first input circuit comprises a first input transistor, wherein a gate of the first input transistor is configured to receive the first clock signal, and wherein the first strength control circuit is coupled between the node and a drain of the first input transistor; and
the second input circuit comprises a second input transistor, wherein a gate of the second input transistor is configured to receive the second clock signal, and wherein the second strength control circuit is coupled between the node and a drain of the second input transistor.