Multiple-phase-interpolation LC voltage-controlled oscillator

• US 6,204,733 B1
• Filed: 07/31/1999
• Issued: 03/20/2001
• Est. Priority Date: 07/31/1998
• Status: Expired due to Term

• Current Assignee: Microsemi Storage Solutions, Inc (Microchip Technology Incorporated)
• Original Assignee: Vitesse Semiconductor Corp (Microchip Technology Incorporated)
• Inventors: Cai, Yijun
• Primary Examiner(s): Grimm, Siegfried H.
• Application Number:
  US09/364,974
• Time in Patent Office: 598 Days
• Field of Search: 331/108.B, 331/117.FE, 331/117.R, 331/135, 331/167, 331/168, 331/177.R
• US Class Current: 331/108.00B
• CPC Class Codes: H03B 5/1209 the amplifier having two current paths operating in a differential manner and a current source or degeneration circuit in common to both paths, e.g. a long-tailed pair. H03B5/1215 takes precedence
• 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: H03B 5/24 active element in amplifier being semiconductor device H03B5/26 takes precedence
• CPC Class Codes: H03K 2005/00052 by mixing the outputs of fixed delayed signals with each other or with the input signal

Abstract

A phase interpolation voltage controlled oscillator (VCO). In one embodiment, the VCO is a multiple phase interpolation VCO. The multiple phase interpolation VCO includes a plurality of phase shifting cells each receiving an oscillating signal, and each phase shifting the oscillation signal a different amount. Summing cells receive the phase shifted oscillating signals and combine the signals to determine an output oscillating signal. In one embodiment, further summing cells receive the output of other summing cells to determine the output oscillating signal.

Claims

1. A voltage-controlled oscillator, comprising:

a plurality of phase shifting cells producing phase shifted signals; and

a plurality of interpolating cells for cumulatively summing the phase shifted signals.

2. The voltage-controlled oscillator of claim 1, wherein the phase shifting cell comprises:

a first LC resonant circuit having a first terminal coupled to a voltage line and a second terminal coupled to a first terminal of a first transistor, the first transistor having a second terminal coupled to a current source, and a gate coupled to a first input;

a second LC resonant circuit having a first terminal coupled to the voltage line and a second terminal coupled to a first terminal of a second transistor, the second transistor having a second terminal coupled to the current source, and a gate coupled to a second input.

3. The voltage-controlled oscillator of claim 1, wherein the interpolating cell comprises:

a first interpolating cell LC resonant circuit having a first terminal coupled to a voltage line and a second terminal coupled to a first terminal of a first interpolating cell transistor, the first interpolating cell transistor having a second terminal coupled to a current source, and a gate coupled to a first interpolating cell input;

a second interpolating cell LC resonant circuit having a first terminal coupled to the voltage line and a second terminal coupled to a first terminal of a second interpolating cell transistor, the second interpolating cell transistor having a second terminal coupled to the current source, and a gate coupled to a second interpolating cell input;

a third transistor having a first terminal coupled to an output, a second terminal coupled to the current source and coupled to the second transistor, and a gate coupled to a third input; and

a fourth transistor having a first terminal coupled to an output, a second terminal coupled to the current source and coupled to the first transistor, and a gate coupled to a fourth input.

4. A voltage controlled oscillator comprising:

a plurality of phase shifting cells, each of the phase shifting cells receiving a common input signal and outputting a phase shifted output signal which is phase shifted with respect to the common input signal, the phase shifted output signal from each phase shifting cell being phase shifted different amounts than phase shifted output signals from other phase shifting cells; and

at least one summing cell receiving the phase shifted output signals of at least two phase shifting cells, the summing cells outputting a signal representative of the sum of the phase shifted output signals; and

wherein there are n phase shifting cells and n−

1 levels of summing cells; and

wherein a first level of the n−

1 levels of summing cells receives the phase shifted output signals and the remaining levels of the summing cells receive signals representative of the sum of the phase shifted output signals.

5. A voltage controlled oscillator providing an oscillating signal, the frequency of the oscillating signal being controllable within a tuning range of frequencies about a center frequency, the voltage controlled oscillator comprising:

a first phase shifting cell receiving the oscillating signal and outputting a first phase shifted output signal, the first phase shifted output signal being phase shifted a positive amount with respect to the oscillating signal;

a second phase shifting cell receiving the oscillating signal and outputting a second chase shifted output signal, the second phase shifted output signal being phase shifted a negative amount with respect to the oscillating signal;

a summing cell receiving the first phase shifted output signal and the second chase shifted output signal and outputting the oscillating signal, the oscillating signal being based on a summation of the first phase shifted output signal and the second phase shifted output signal;

wherein the first phase shifting cell comprises a first LC tank, the first LC tank having a resonant frequency less than the center frequency, and wherein the second phase shifting cell comprises a second LC tank, the second LC tank having a resonant frequency greater than the center frequency;

wherein the summing cell comprises a summing cell LC tank, the summing cell LC tank having approximately zero phase shift about the center frequency;

wherein the summing cell LC tank has a resonant frequency greater than the center frequency; and

wherein the first LC tank and the second LC tank are parallel LC tanks, and the summing cell LC tank is a series LC tank.

6. The voltage controlled oscillator of claim 5 wherein the summing cell comprises a modified Gilbert cell, the modification being the use of an LC tank at a summing node of the Gilbert cell.

7. A voltage controlled oscillator comprising:

a plurality of n phase shifting cells, with n at least 3, each of the phase shifting cells receiving a common input signal and outputting a phase shifted output signal which is phase shifted with respect to the common input signal, the phase shifted output signal from each phase shifting cell being phase shifted different amounts than phase shifted output signals from other phase shifting cells; and

a plurality of summing cells receiving the phase shifted output signals of at least two phase shifting cells, the summing cells outputting signals representative of the sum of the phase shifted output signals.