Multi-mode VCO for direct FM systems

• US 7,974,374 B2
• Filed: 05/16/2007
• Issued: 07/05/2011
• Est. Priority Date: 05/16/2006
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Quintic Holdings (NXP Semiconductors NV)
• Inventors: Costa, Damian, Austin, Joe, Groe, John B.
• Primary Examiner(s): Odom; Curtis B
• Application Number:
  US11/749,538
• Publication Number:
  US 20070291889A1
• Time in Patent Office: 1,511 Days
• Field of Search: 375371-376, 331167-171
• US Class Current: 375/376
• 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 5/1253 the transistors being field-effect transistors
• CPC Class Codes: H03C 3/0925 applying frequency modulation at the divider in the feedback loop
• CPC Class Codes: H03C 3/0933 using fractional frequency division in the feedback loop of the phase locked loop
• CPC Class Codes: H03C 3/0958 applying frequency modulation by varying the characteristics of the voltage controlled oscillator

Abstract

Systems for multi-mode phase modulation are disclosed. Systems provide for direct modulation of a multi-mode voltage controlled oscillator (VCO). A fractional-N counter may be used in a phase-locked loop (PLL) to synthesize a radio frequency carrier signal. The multi-mode VCO may be characterized by a first frequency gain during operation in a first mode and by a second frequency gain during operation in a second mode where signals controlling the first and second operating modes are provided by a control circuit. The control circuit may include a switch to provide control signals to the VCO.

Claims

1. A multi-mode voltage-controlled oscillator comprising:

a voltage control input port to supply a common mode voltage;

a first auxiliary input port;

a second auxiliary input port, wherein the first auxiliary input port and the second auxiliary input port are accessed for direct modulation; and

a LC tank circuit, wherein the LC tank circuit is configured to operate in accordance with a first frequency gain in response to a first signal received at the first auxiliary input port and in accordance with a second frequency gain in response to a second signal received at the second auxiliary input port, wherein the multi-mode voltage-controlled oscillator is configured so that either the first signal is received at the first auxiliary input port or the second signal is received at the second auxiliary input port, wherein the first frequency gain and the second frequency gain are different to cause different frequency modulation ranges.

2. The multi-mode voltage-controlled oscillator of claim 1, wherein the LC tank circuit includes a first network connected to the first auxiliary input port, wherein the first network includes a first plurality of elements selected to achieve the first frequency gain.

3. The multi-mode voltage-controlled oscillator of claim 2, wherein the LC tank circuit includes a second network connected to the second auxiliary input port, wherein the second network includes a second plurality of elements selected to achieve the second frequency gain.

4. The multi-mode voltage-controlled oscillator of claim 3, wherein the multimode voltage-controlled oscillator is coupled to a differentiator device operative to produce the first signal and the second signal.

5. The multi-mode voltage-controlled oscillator of claim 4, wherein the differentiator device includes a multiplier that scales the first signal by a first value during operation in a first mode and the second signal by a second value during operation in a second mode.