Adaptive loop gain control circuit for voltage controlled oscillator

• US 6,833,766 B2
• Filed: 04/09/2003
• Issued: 12/21/2004
• Est. Priority Date: 04/19/2002
• Status: Expired due to Fees

• Current Assignee: Pendragon Electronics and Telecommunications Research LLC (Pendrell Corporation)
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Kim, Kwi-dong, Kwon, Jong-Kee, Jung, Hee-Bum, Kim, Kyung-Soo
• Primary Examiner(s): Pascal, Robert
• Assistant Examiner(s): Chang, Joseph
• Application Number:
  US10/410,829
• Publication Number:
  US 20030197570A1
• Time in Patent Office: 622 Days
• Field of Search: 331/17, 331/74, 331/57, 331/176, 327/148, 327/157
• US Class Current: 331/17
• CPC Class Codes: H03L 1/00 Stabilisation of generator output against variations of physical values, e.g. power supply
• CPC Class Codes: H03L 7/0995 the oscillator comprising a ring oscillator

Abstract

There is provided an adaptive loop gain control circuit for a voltage-controlled oscillator (VCO). The adaptive loop gain control circuit for a voltage-controlled oscillator (VCO) includes a detected voltage generating unit which generates a detected voltage signal according to changes in an operating voltage and an operating temperature, and a control circuit unit which outputs an oscillation control current signal according to the detected voltage signal and an input control voltage signal. The adaptive loop gain control circuit for a voltage-controlled oscillator (VCO) compensates for an oscillation control current according to changes in operating voltage and temperature and compensates for the gain of a phase locked loop (PLL) system, thereby ensuring high operating stability in the PLL circuit.

Claims

1. An adaptive loop gain control circuit comprising:

a detected voltage generating unit which generates a detected voltage signal in response to changes in the operating voltage and operating temperature; and

a control circuit unit which outputs an oscillation control current signal according to the detected voltage signal and an input control voltage signal,

wherein the detected voltage generating unit comprises a filter which eliminates noise of the detected voltage signal.

2. The adaptive loop gain control circuit of claim 1, wherein the filter is an RC filter comprising a resistor and a capacitor.

3. The adaptive loop gain control circuit of claim 1, wherein the detected voltage generating unit comprises:

a first MOS transistor which has a gate and a drain that are connected to a first supply voltage and a source that outputs the detected voltage; and

a second MOS transistor which has a gate and a drain that are connected to a second supply voltage and a source that is connected the source of the first MOS transistor.

4. The adaptive loop gain control circuit of claim 1, wherein the control circuit unit comprises:

a first operational amplifier where the input control voltage signal is inputted to a non-inverting terminal and an inverting terminal is connected to an output terminal;

a second operational amplifier where the detected voltage signal is inputted to a non-inverting terminal, an inverting terminal is connected to the output terminal of the first operational amplifier, the second operational amplifier amplifying a difference between output voltages of the detected voltage and the first operational amplifier and outputting the current control voltage signal; and

a third MOS transistor which has a gate connected to the output terminal of the second operational amplifier and a source connected to the first supply voltage and outputs the control current signal to the first supply voltage.

5. The adaptive loop gain control circuit of claim 4, wherein the adaptive loop gain control circuit further comprises a filter comprising a capacitor and a resistor connected with each other in parallel between the inverting terminal and the output terminal of the second operational amplifier.