PLL circuit, radio-communication equipment and method of oscillation frequency control

• US 20050237125A1
• Filed: 04/07/2005
• Published: 10/27/2005
• Est. Priority Date: 04/26/2004
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Hino, Takuo
• Granted Patent: US 7,301,414 B2
• Time in Patent Office: Days
• US Class Current: 331/179
• 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 5/1231 the amplifier comprising one or more bipolar 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: H03B 5/1293 having means for achieving a desired tuning characteristic, e.g. linearising the frequency characteristic across the tuning voltage range
• CPC Class Codes: H03J 5/244 using electronic means
• CPC Class Codes: H03L 2207/06 Phase locked loops with a controlled oscillator having at least two frequency control terminals
• CPC Class Codes: H03L 7/0898 the source or sink current values being variable H03L7/0896 takes precedence
• CPC Class Codes: H03L 7/1072 by changing characteristics of the charge pump, e.g. changing the gain
• CPC Class Codes: H03L 7/183 a time difference being used for locking the loop, the counter counting between fixed numbers or the frequency divider dividing by a fixed number H03L7/1806 takes precedence

Abstract

A Phase-Locked Loop (PPL) circuit includes a voltage controlled oscillator (VCO), a reference signal oscillator, first and second frequency dividers, a phase comparator, a charge pump and a loop filter. The VCO has a plural number of oscillation frequency boards and oscillates according to a control voltage in a selected band. The first frequency divider frequency divides the output signal of the VCO. The second frequency divider frequency divides the reference signal outputted from the reference signal oscillator. The phase comparator detects the phase difference between the output signal of the first and second frequency dividers and outputs a phase difference signal. The charge pump inputs and outputs a current generated by a gain that was set depending on the selected band based on the phase difference signal. The loop filter increases or decreases the voltage with a specified low pass filter.

Claims

1. Phase Locked Loop (PLL) circuit comprising

a voltage controlled oscillator which has a plural number of oscillation frequency bands “

band”

) and oscillates according to a control voltage in a selected band,

a first frequency divider frequency-dividing the output signal of said voltage controlled oscillator,

a reference signal oscillator,

a second frequency divider frequency-dividing the reference signal outputted from said reference signal oscillator,

a phase comparator detecting a phase difference between the output signal of said first frequency divider and the output signal of said second frequency divider and outputing a phase difference signal,

a charge pump that inputs and outputs a current generated by a gain that was set depending on the selected band based on said phase difference signal, and

a loop filter which increases or decreases the voltage with a specified low pass filter characteristic by a current which said charge pump inputs and outputs and thereby generates said control voltage.

2. The PLL circuit claimed in claim 1 comprising

a frequency measurement unit to which said reference signal or a frequency-divided signal of said reference signal and the output signal of said voltage controlled oscillator or a frequency-divided signal thereof are inputted, and which measures the frequency of the output signal of the voltage controlled oscillator or of the frequency-divided signal thereof based on said reference signal or the frequency-divided signal of said reference signal, and

a band selection unit selecting a band on which said voltage-controlled oscillator operates according to the frequency measured by said frequency measurement unit.

3. The PLL circuit claimed in claim 1 characterized in that said charge pump inputs and outputs a current that was set depending on the selected band in the time period according to said phase difference signal.

4. The PLL circuit claimed in claim 1 further comprising

a switch inserted between said loop filter and said voltage controlled oscillator, and wherein

said switch selects and outputs either the output voltage of said loop filter or the first constant voltage as the control voltage to said voltage controlled oscillator.

5. The PLL circuit claimed in claim 1 further comprising

a switch inserted between said loop filter and said voltage controlled oscillator, and wherein

said switch selectively outputs a voltage selected from the output voltage of said loop filter, the first constant voltage, and one or plural number of the second constant voltage as the control voltage to said voltage controlled oscillator.

6. A radio communication equipment which has the PLL circuit claimed in claim 1, and modulates the input signal with the output signal of said voltage controlled oscillator or with the frequency-divided signal thereof which was outputted from said PLL circuit and radio-transmits it, or demodulates the radio-received input signal.

7. The radio communication equipment claimed in claim 6 characterized in that said radio communication equipment is either of a mobile terminal or a base station apparatus of a mobile phone system.

8. An oscillation frequency control method comprising

an oscillation step of making the voltage controlled oscillator having a plural number of bands oscillate in the selected band,

a first frequency-dividing step to divide the frequency of the output signal of said voltage controlled oscillator,

a second frequency-dividing step to divide the frequency of the reference signal,

a phase comparing step of detecting the phase difference between the frequency-divided signal in said first frequency-dividing step and the frequency-divided signal in said second frequency-dividing step and of outputting the phase difference signal,

a current driving step for inputting and outputting a current generated at a gain which was set depending on the selected band based on said phase difference signal, and

a control voltage generation step for generating a control voltage of said voltage controlled oscillator by increasing or decreasing the voltage with a specified low-pass filter characteristic by the current inputted and outputted at said current driving step.

9. The oscillation frequency control method claimed in claim 8 characterized in that a current inputs and outputs a current that was set responding to the band selected in the time period according to said current driving step.

10. The oscillation frequency control method claimed in claim 8 further comprising

a first frequency measurement step in which, under the condition that said voltage-controlled oscillator is set to a specified band and said control voltage of a constant value is applied, said reference signal or the frequency-divided signal of said reference signal and the output signal of said voltage controlled oscillator or the frequency-divided signal thereof are inputted, and based on said reference signal or the frequency-divided signal of said reference signal, the frequency of the output signal of said voltage controlled oscillator or of the frequency-divided signal thereof is measured, and

a band-selection step to select a band in which said voltage-controlled oscillator operates according to the frequency measured in said first frequency measurement step.

11. The oscillation frequency control method claimed in claim 8 comprising

a second frequency measurement step for measuring the oscillation frequency of said voltage controlled oscillator by applying the first constant voltage as said control voltage in the selected band,

a third frequency measurement step for measuring the oscillation frequency of said voltage controlled oscillator by applying the second constant voltage as said control voltage in the selected band,

a gain setting step to set the gain at said current driving step in the band, based on the difference between the measured oscillation frequency in said second frequency measurement step and the measured oscillation frequency in said third frequency measurement step, and

a step to make said voltage controlled oscillator oscillate by inputting and outputting the current generated at the gain that was set based on said phase difference signal in said current driving step, and by applying the output voltage of said control voltage generation step as said control voltage.

12. The oscillation frequency control method claimed in claim 8 comprising

a second frequency measurement step for measuring the oscillation frequency of said voltage controlled oscillator by applying the first constant voltage as said control voltage in the selected band,

a fourth frequency measurement step for measuring the oscillation frequency of said voltage controlled oscillator by applying the output voltage of said control voltage generation step in the selected band,

a fifth frequency measurement step in which, in the selected band, when the frequency measured in the fourth frequency measurement step is higher than the frequency measured in the second frequency measurement step, a constant voltage higher by the amount of a specified voltage than said first constant voltage is selected, while when the frequency measured in the fourth frequency measurement step is lower than the voltage measured in the second frequency measurement step, a constant voltage lower by a specified voltage than said first constant voltage, and then the selected constant voltage is applied as said control voltage, thereby the oscillation frequency of said voltage controlled oscillator is measured,

a gain setting step to set the gain at said current driving step in the band, based on the frequency difference between the measured oscillation frequency in said second frequency measurement step and the measured oscillation frequency in said fifth frequency measurement step, and

a step to make said voltage controlled oscillator oscillate by inputting and outputting the current generated at the gain that was set based on said phase difference signal in said current driving step, and then by applying the output voltage of said control voltage generation step as said control voltage.

13. An oscillation frequency control method characterized in that, when power is turned on, it executes one of those oscillation frequency control methods claimed in claim 10 is executed having a specified frequency as a target frequency, a band including a target frequency is selected, and then the gain in said current driving step is set.

14. An oscillation frequency control method further comprising

a step to prohibit or permit the band selection action and the gain setting action in said current driving step, and wherein, only when the band selection action and the gain setting action in said current driving step are permitted, the oscillation frequency control method claimed in claim 10 is executed.

15. An oscillation frequency control method further comprising

a step to execute the oscillation frequency control method claimed in claim 8 so that said voltage controlled oscillator oscillates at a specified target frequency at the time when the power source is turned on, and

a step in which, in case that a new target frequency is set, based on the new target frequency, or based on a difference between the new target frequency and said specified target frequency, the band selection and the gain setting in said current driving step are executed using a specified arithmetic expression or a specified table.

16. An oscillation frequency control method characterized in that it selectively executes

a step to read and set the gain of said current driving step corresponding to the selected band from a memory storing the gain of said current driving step for respective bands, and to execute the oscillation frequency control method claimed in claim 8, and

a first frequency measurement step in which, under the condition that said voltage-controlled oscillator is set to a specified band and said control voltage of a constant value is applied, said reference signal or the frequency-divided signal of said reference signal and the output signal of said voltage controlled oscillator or the frequency-divided signal thereof are inputted, and based on said reference signal or the frequency-divided signal of said reference signal, the frequency of the output signal of said voltage controlled oscillator or of the frequency-divided signal thereof is measured, and

a band-selection step to select a band in which said voltage-controlled oscillator operates according to the frequency measured in said first frequency measurement step.

17. The oscillation frequency control method claimed claim 10 characterized in that, when switching over from the step for measuring the oscillation frequency of said voltage controlled oscillator by applying a constant voltage as said control voltage to the step for making said voltage controlled oscillator oscillate by applying the output voltage of said control voltage generation step as said control voltage, setting the gain of said current driving step is transiently set high, and after a specified time lapses or after the osillation frequency of said voltage controlled oscillator was locked in a certain specified range of error with respect to a target frequency, the gain of said current driving step is set to a value responding to said selected band.

18. An oscillation frequency control method comprising

a radio communication step to modulate the input signal by an output signal of the voltage controlled oscillator or a frequency-divided signal thereof for the radio-transmission, or to demodulate the radio-received input signal, and

an adjustment step to execute the oscillation frequency control method claimed in claim 10 during the period while said radio communication step is not executed.

19. An oscillation frequency control method claimed in claim 18 characterized in that said adjustment step is executed during the period while said radio communication is not executed and the oscillation frequency of said voltage controlled oscillator deviates more than a specified threshold value from the target frequency.