JPH0568133U - Phase lock loop device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to realize a PLL device that widens the capture range and improves the characteristics when locked. This apparatus has two input terminals, and outputs a voltage corresponding to the phase difference between signals applied to the two input terminals and a phase comparator, and outputs the output of the phase comparator. A switched capacitor filter that removes out-of-band components that are determined by the frequency input that changes the cutoff frequency, a frequency generator that inputs the frequency according to the output voltage of the phase comparator to the switched capacitor filter, and a switched capacitor filter. A phase-locked loop device comprising: a voltage-controlled oscillator that outputs an oscillation frequency determined by an output voltage of a capacitor filter to one input end of a phase comparator.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to improvement of lock characteristics of a phase lock loop (hereinafter abbreviated as PLL) device.

[0002]

[Prior Art]

 A conventional PLL device has two input terminals and outputs a voltage corresponding to the phase difference between signals applied to the two input terminals, and an output of this phase comparator to input the out-of-band signal. It is composed of a low-pass filter that removes the component and a voltage-controlled oscillator (hereinafter abbreviated as VCO) that outputs the oscillation frequency determined by the output voltage of the low-pass filter to one input end of the phase comparator. It was

[0003]

[Problems to be solved by the device]

 The device having such a configuration has the following problems. The VCO synchronizes with, or locks to, the input signal of the phase comparator. Once locked, it will match the input signal, omitting the constant phase difference. Also, once locked, it follows changes in the input frequency. However, widen the cap challenge to make it easier to lock. That is, the cutoff frequency of the low pass filter is increased. Then, since the noise band is wide, the characteristics at the time of locking are deteriorated. Also, if the cutoff frequency of the low-pass filter is lowered, the lock characteristics will improve, but it will be difficult to lock.

An object of the present invention is to realize a PLL device which has a wide capture range and has good lock characteristics.

[0005]

[Means for Solving the Problems]

 The present invention is a phase-locked loop device used for FM modulation and oscillators, which has two input terminals and outputs a voltage corresponding to the phase difference between signals applied to these two input terminals. And a switched capacitor filter for removing the out-of-band component determined by the frequency input that changes the cutoff frequency by inputting the output of this phase comparator, and the frequency according to the output voltage of the phase comparator. A frequency generator for inputting to the switched capacitor filter, and a voltage controlled oscillator for outputting the oscillation frequency determined by the output voltage of the switched capacitor filter to one input terminal of the phase comparator. It is characterized by that.

[0006]

[Action]

 In the present invention, the characteristics of the filter can be changed by providing the switched capacitor filter (hereinafter abbreviated as SCF) and the frequency generator. As a result, it is possible to realize a PLL device that widens the capture range and improves the characteristics when locked.

[0007]

【Example】

 The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, reference numeral 1 denotes a phase comparator which has two input terminals and outputs a voltage corresponding to a phase difference of signals applied to the two input terminals, and 2 denotes an input of the output of the phase comparator 1. , SCF for removing the out-of-band component determined by the frequency input that changes the cutoff frequency, 3 is a frequency generator for inputting a frequency according to the output voltage of the phase comparator 1 to SCF 2, and 4 is It is a VCO that outputs the oscillation frequency determined by the output voltage of the SCF 2 to one input terminal 12 of the phase comparator 1. In the frequency generator 3, 31 is a rectifier that rectifies the output voltage Ve of the phase comparator 1, 32 is a filter that is a low-pass filter that receives the output voltage of the rectifier 31 and removes out-of-band components, and 33 is , The VCO that inputs the oscillation frequency determined by the output voltage of the filter 32 to the SCF 2.

The operation of such a device will be described below. If the control voltage is 0, the VCO 4 oscillates at the free-running frequency. When the input signal Vs is applied to one input terminal 11 of the phase comparator 1, an error voltage Ve is generated according to the frequency between the frequency output Vo of the VCO 4 and the input Vs or the phase difference. Upon receiving the error voltage Ve, the rectifier 31 rectifies it. That is, the error is converted into a positive component and output to the filter 32. The VCO 33 outputs an oscillation frequency determined by the voltage output from the filter 32 to the SCF 2. The SCF 2 raises the cutoff frequency when the frequency of the VCO 33 is high, and lowers the cutoff frequency when the frequency is low. A low frequency component is taken out from the error voltage Ve by the SCF 2 and is used as a control voltage Vc of the VCO 4. The control voltage Vc changes the frequency of the output Vo of the VCO 4 so that the phase difference between the input Vs and the output Vo of the VCO 4 decreases.

In other words, when unlocked, the cutoff frequency of the SCF 2 becomes high, the capture range of the PLL device is widened, and locking becomes easier. Then, when locked, the cutoff frequency of the SCF 2 is lowered, and the lock characteristic is improved. Further, the change in the cutoff frequency of SCF2 is controlled by the error voltage Ve. You can rock once to lower the cutoff frequency, and if it goes out of lock range, you can immediately raise the cutoff frequency to widen the capture range. As a result, the range width can be changed by immediately following the input of the phase comparator.

The rectifier may be between the filter and the VCO. In short, it is sufficient to increase the frequency of the frequency generator when the error is large with respect to the frequency difference or the phase difference in the phase comparator, and to decrease the frequency when the error is small. In other words, when the error output of the phase comparator is positive and changes, the role of the rectifier of the frequency generator is that the VCO in the frequency generator has a large difference with respect to the frequency difference or the phase difference. When the frequency of the frequency generator is large and the error is small, it is sufficient if the voltage can be adjusted so as to reduce the frequency.

[0011]

[Effect of the device]

 The present invention has the following effects. When unlocked, the capture range is widened to make it easier to lock, and when locked, the lock range is narrowed to improve the lock characteristics. In addition, since the change in the cutoff frequency of the SCF is controlled by the error voltage, the range width can be changed by immediately following the input of the phase comparator.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 phase comparator 2 SCF 3 frequency generator 4 VCO 11, 12 input end

Claims (1)

[Scope of utility model registration request] 1. A phase-locked loop device used for FM modulation or an oscillator, comprising: two phase inputs; and a phase comparator outputting a voltage corresponding to a phase difference between signals applied to the two mode inputs. And a switched capacitor filter for removing the out-of-band component determined by the frequency input that changes the cutoff frequency by inputting the output of this phase comparator, and a frequency corresponding to the output voltage of the phase comparator, A frequency generator for inputting to the switched capacitor filter; and a voltage controlled oscillator for outputting the oscillation frequency determined by the output voltage of the switched capacitor filter to one input terminal of the phase comparator, Phase-locked loop device.