JPH01154626A - Phase locked oscillation circuit - Google Patents

Abstract

PURPOSE:To obtain an output frequency other than a frequency being an integral number of multiple and to eliminate a spurious wave completely by mixing an output signal of a 1st phase locked loop obtained by a 1st reference signal with a 2nd reference signal at a mixer, giving it through a band pass filter, using it at a 2nd phase locked loop to obtain an output signal. CONSTITUTION:An output signal from a 1st voltage controlled oscillator 1 of the 1st phase locked loop L1 is an integral number of multiple of the 1st reference signal I in the phase comparator 3 and mixed by the 2nd reference signal II by a mixer 5 to obtain a signal of a desired frequency. The spurious wave generated in this case is attenuated to some degree by a band pass filter 6. The output signal is frequency-divided by a frequency divider 7 and fed to the 2nd phase locked loop L2 and it is phase-compared with a frequency division output by the frequency divider of the 2nd voltage controlled oscillator 8 at a phase comparator 10 and its output is fed back to the 2nd voltage controlled oscillator 8 through the amplifier 11. Thus, the spurious wave is eliminated to obtain a frequency other than the integral number of multiple.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a phase-locked oscillation circuit used in a local oscillator, etc., and particularly to a phase-locked oscillation circuit that can be set to an arbitrary frequency and that produces an output signal that does not contain unnecessary waves. The present invention relates to a phase-locked oscillation circuit that can be obtained.

[Conventional technology]

2. Description of the Related Art Conventionally, there is a phase synchronized oscillation circuit using a voltage controlled oscillator having a configuration shown in FIG. That is, it is composed of a voltage controlled oscillator 19, a frequency divider 21, a phase comparator 3, and an amplifier 4, and the output from the voltage controlled oscillator 1 is divided by the frequency divider 2, and the phase of this divided output and the reference signal I is compared. A phase locked loop is constructed by comparing the phases in the device 3 and feeding back the comparison output to the voltage controlled oscillator 1 through the amplifier 4.

[Problem that the invention seeks to solve]

In the conventional phase-locked oscillator circuit described above, the comparison voltage obtained by comparing the phases of the frequency-divided output of the voltage-controlled oscillator and the reference signal is fed back to the voltage-controlled oscillator to obtain the output of the phase-locked oscillator. The output frequency is only an integral multiple of the phase comparison frequency, and it is not possible to obtain an output frequency other than an integral multiple of the phase comparison frequency.

For this reason, a configuration has also been proposed in which a mixer is attached to obtain an output frequency other than an integer multiple, and the signal mixed with a reference signal by this mixer is passed through a bandpass filter to obtain an output frequency other than an integer multiple. However, there is a problem in that the unnecessary waves generated by the mixer cannot be completely removed.

The present invention can obtain an output frequency other than an integer multiple,
Moreover, it is an object of the present invention to provide a phase-locked oscillation circuit that can completely eliminate unnecessary waves.

[Means for solving problems]

The phase-locked oscillator circuit of the present invention includes a first phase-locked loop that obtains an output by comparing the phases of the output of the first voltage-controlled oscillator and a first reference signal, and a second phase-locked loop that uses the output signal of the first phase-locked loop as a second reference signal. It has a mixer for mixing with the signal, a bandpass filter connected to the mixer, and a second phase-locked loop that compares the phases of the passed output of the bandpass filter and the output of the second voltage-controlled oscillator to obtain an output. are doing.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

In the figure, the output signal from the first voltage controlled oscillator 1 is frequency-divided by a frequency divider 2, the output signal and the first reference signal I are phase-compared in a phase comparator 3, and the phase comparison output is sent to an amplifier 4. The first phase-locked loop L1 is configured by feeding back to the voltage-controlled oscillator 1 through the voltage-controlled oscillator 1. The output signal of the first voltage controlled oscillator 1 obtained from this phase synchronization operation is mixed with the second reference signal 2 by the mixer 5. Then, the mixed signal is passed through a bandpass filter 6 to extract only the desired output signal and further frequency-divided. This frequency divided signal is sent to the second voltage controlled oscillator 89, frequency divider 9° phase comparator 1
0. It is used as a reference signal for the second phase-locked loop L2 composed of the amplifier 11.

According to this configuration, the output signal from the first voltage-controlled oscillator 1 of the first phase-locked loop L1 becomes an integral multiple of the first reference signal ■ in the phase comparator 3, and then the second reference signal By mixing with the signal (2), a signal of the desired frequency can be obtained. However, at this time, unnecessary waves are generated. This unnecessary wave is filtered by the band pass filter 6.
Although it is attenuated to some extent, it is difficult to completely eliminate it.

Therefore, after dividing this output signal by the frequency divider 7, the second
The phase-locked loop L2 is supplied to the phase-locked loop L2, and the phase is compared with the frequency-divided output from the frequency divider 9 of the second voltage-controlled oscillator 8 in the phase comparator 10, and the output is fed back to the second voltage-controlled oscillator 8 through the amplifier 11. ing. As a result, unnecessary waves are removed from the output frequency of the second voltage controlled oscillator 8, and an output signal having a frequency other than an integral multiple of the comparison frequency of the phase comparator 3 can be obtained.

〔Effect of the invention〕

As explained above, the present invention mixes the output signal of the first phase-locked loop obtained using the first reference signal with the second reference signal in a mixer, passes this through a bandpass filter, and then mixes the output signal of the first phase-locked loop obtained using the first reference signal.
Since the output signal is obtained by comparing the phases in the phase-locked loop, any frequency can be obtained by arbitrarily selecting each phase-locked loop, the frequency division number between them, and the reference signal frequency. The action of the locked loop has the effect of obtaining an output signal that completely eliminates unnecessary waves that cannot be attenuated by a bandpass filter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the phase-locked oscillation circuit of the present invention, and FIG. 2 is a block diagram of a conventional phase-locked oscillation circuit. ■...First voltage controlled oscillator, 2...Frequency divider, 3...
・Phase comparator, 4... Amplifier, 5... Mixer, 6.
...bandpass filter, 7...frequency divider, 8...second
Voltage controlled oscillator, 9... Frequency divider, 10... Phase comparator, 11... Amplifier, Ll... First phase locked loop, L2... Second phase locked loop, ■... 1st reference signal, ■...2nd reference signal.

Claims (1)

[Claims] (1) A first phase-locked loop that obtains an output by comparing the phases of the output of the first voltage controlled oscillator and the first reference signal;
a mixer for mixing the output signal of the phase-locked loop with a second reference signal; a bandpass filter connected to the mixer;
A phase-locked oscillation circuit characterized by comprising a second phase-locked loop that compares the phases of the passed output of the band-pass filter and the output of the second voltage-controlled oscillator to obtain an output.