JPH03141724A - Phase locked loop oscillation circuit - Google Patents

Abstract

PURPOSE:To vary an oscillating frequency without using a variable frequency divider and to simplify circuit configuration by providing a means to add (subtract) an external control voltage, which sets the oscillating frequency of a voltage controlled oscillator, to the control signal of the voltage controlled oscillator. CONSTITUTION:A reference signal inputted from an input terminal 11 is inputted to a sampling phase detector 12 and the output is inputted through an LPF 13, etc., to a voltage controlled oscillator 14. Next, the output of the oscillator 14 is taken out from an output terminal 15 as a microwave output, fed back and connected to the detector 12 and a phase locked loop is constituted. In such a case, a adder circuit 17 is provided to add an external control voltage VC to be supplied to an input terminal 16 to the control signal of the oscillator 14 to be outputted from the detector 12 from the output part of the detector 12 to the control signal input part of the oscillator 14. (Under this condition, the circuit 17 not only executes an adding operation but also executes a subtracting operation). Thus, the oscillating frequency can be made variable without using the variable frequency divider and the circuit configuration is simplified. Then, a noise characteristic is improved and a loop filter can be easily designed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a phase-locked oscillation circuit whose oscillation frequency is variable in the microwave band.

(Prior Art) A phase-locked oscillation circuit is widely known as a high-frequency oscillation circuit.

FIG. 4 is a block diagram showing the configuration of a conventional phase-locked oscillation circuit with variable oscillation frequency.

In the figure, the reference signal input from the input terminal 41 is
It is input to one input terminal of a phase comparator 42, and its output is input to a voltage controlled oscillator (VC◯) 44 via a low pass filter (LPF) 43. Voltage controlled oscillator 44
The output is taken out from the output terminal 45 as a microwave output, and is feedback-connected to the other input terminal of the phase comparator 42 via the variable frequency divider 46, thereby forming a phase locked loop.

In this way, by frequency-dividing the output of the voltage-controlled oscillator 44, the phase is compared with the reference signal, and an output proportional to the error is given as the control power of the voltage-controlled oscillator 44 via the low-pass filter 43. , a highly stable microwave output synchronized with the reference signal can be taken out from the output terminal 45.

Note that in this configuration, the oscillation frequency of the voltage controlled oscillator 44 can be changed according to the frequency division ratio set in the variable frequency divider 46.

[Problems to be Solved by the Invention] By the way, circuits such as a dual modulus prescaler known as a variable frequency divider are complex, and the operable frequency is low. Therefore, when the oscillator output is in the microwave band, it is necessary to provide a high-speed fixed frequency divider before the variable frequency divider to lower the frequency. This lowers the frequency of the reference signal for phase comparison, which worsens the noise characteristics and reduces the loop filter (
This has become a factor that makes it difficult to design the low-pass filter 43).

SUMMARY OF THE INVENTION An object of the present invention is to provide a phase synchronized oscillation circuit that can vary the oscillation frequency without using a variable frequency divider and has a simple circuit configuration.

[Means for Solving the Problems] The present invention includes a sampling phase detector into which a reference signal is manually input to one input terminal, and a low-pass filter that removes high-frequency components from the output signal of the sampling phase detector. ,
a voltage controlled oscillator whose oscillation frequency is set using the output signal of the sampling phase detector via the low-pass filter as a control signal, and whose oscillator output is feedback-connected to the other input terminal of the sampling phase detector; In a phase-locked oscillator circuit that generates an oscillator output synchronized with a reference signal, an external control voltage that sets the oscillation frequency of the voltage-controlled oscillator is connected between the output of the sampling phase detector and the control signal input of the voltage-controlled oscillator. It is configured to include means for adding to or subtracting from the control signal of the voltage controlled oscillator.

[For production]

By using a sampling phase detector as a phase comparator, a super high frequency signal (microwave output) is sampled with a low frequency signal (reference signal), and the phase of the harmonic components of the low frequency signal and the super high frequency signal can be directly compared. is possible, so no frequency divider is required.

In the present invention, an external control voltage supplied from a voltage source provided outside the phase-locked oscillator circuit is added to a control signal for the voltage-controlled oscillator output from a sampling phase detector, thereby controlling the voltage-controlled oscillator. Oscillation frequency can be changed.

Note that when the oscillation frequency of the voltage controlled oscillator becomes close to an integral multiple of the reference signal frequency, the phase is pulled in by the sampling phase detector, and a synchronized state is achieved.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

Note that in the phase-locked oscillation circuit of the present invention, a sampling phase detector is used as the phase comparator. A numbering phase detector samples a super high frequency signal with a low frequency signal to directly compare the phases of the harmonic components of the low frequency signal and the super high frequency signal. In the literature (Saka et al., "X-hand phase-locked oscillator", 1986 IEICE Semiconductor and Materials Division Zenten 2-28), as a component of a phase-locked oscillator circuit with a fixed oscillation frequency, it is stabilized in a lecture resonator. A configuration using this sampling phase detector together with a voltage controlled oscillator with a narrow frequency variable width is shown.

In a phase-locked oscillator circuit that uses a sampling phase detector as a phase comparator, when the reference signal frequency and the frequency of the voltage-controlled oscillator become an integral multiple, the output of the sampling phase detector becomes constant, and the synchronized loop becomes synchronized. becomes.

The present invention uses this sampling phase detector together with a voltage controlled oscillator with a wide frequency variable range, and by adopting a configuration in which the oscillation frequency is made variable by an external control voltage, it is possible to synchronize at a frequency that is an arbitrary integral multiple of the reference signal frequency. That is.

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

In the figure, the reference signal manually input from the input terminal 11 is
The signal is input to one input terminal of a sampling phase detector 12, and its output is input to a voltage controlled oscillator (VCO) 14 via a low pass filter (LPF) 13. The output of the voltage controlled oscillator 14 is taken out as a microwave output from an output terminal 15, and is feedback-connected to the other input terminal of the sampling phase detector 12, thereby forming a phase-locked loop.

Here, the feature of the present invention is that the external control voltage VC supplied to the input terminal 16 is connected to the sampling phase between the output part of the sampling phase detector 12 and the control signal input part of the voltage controlled oscillator 14. The configuration includes an adder circuit 17 that adds to the control signal of the voltage controlled oscillator 14 output from the detector 12. In this embodiment, the adder circuit 17 is inserted between the low-pass filter 13 and the voltage-controlled oscillator 14.

In the phase-locked oscillator circuit having such a configuration, the oscillation frequency is changed by an external control voltage, and when the oscillation frequency approaches an integral multiple of the reference signal frequency, the sampling phase detector I2 pulls in the phase, resulting in a synchronized state. At this time, if the synchronization pull-in range of the phase-locked loop is designed to be, for example, twice the reference signal frequency or less, it is possible to set the oscillation frequency so that synchronization does not occur at frequencies other than the reference signal frequency.

The external control voltage VC supplied to the input terminal 16 can be provided by preparing a plurality of circuits that resistively divide one power supply voltage and switching between them. In addition, read-only memory (ROM) and digital/analog (D
A) The external control voltage V, can be controlled by a converter as well.

Note that the addition circuit 17 is not limited to one that performs an addition operation, but may also be one that performs a subtraction operation, and the external control voltage supplied to the input terminal 16 may be either a positive or negative voltage.

FIG. 2 is a block diagram showing the configuration of a second embodiment of the present invention.

This embodiment shows a configuration in which an adder circuit 17 is inserted between the sampling phase detector 12 and the low-pass filter 13.

Note that the operation is exactly the same as that of the first embodiment.

FIG. 3 is a diagram showing the configuration of a third embodiment of the present invention.

In this embodiment, the voltage controlled oscillator 14' has two control input ports; one control input port receives the output of the sampling phase detector 12 via the low-pass filter 13, and the other control input port receives the output of the sampling phase detector 12 via the low-pass filter 13. ■ External control voltage on the port.

The configuration is to incorporate.

Note that, similarly to the voltage controlled oscillator 14', a circuit section for adding the external control voltage V may be provided to the low-pass filter 13 or the sampling phase detector 12.

[Effects of the Invention] As described above, the present invention can make the oscillation frequency variable in a phase synchronized oscillation circuit using a sampling phase detector.

In other words, in a microwave band frequency synthesizer, there is no need to use a fixed frequency divider, so 5? % signal can be set high. Therefore, the noise characteristics can be improved and the design of the loop filter can be facilitated.

Furthermore, the present invention does not require the use of complex circuits such as a dual modulus prescaler, and can realize a phase-locked oscillator circuit (frequency synthesizer) that can vary the oscillation frequency with a simple circuit configuration, reducing the number of elements and power consumption. Improvements can be made.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of a second embodiment of the present invention. FIG. 3 is a block diagram showing the configuration of a second embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of a conventional phase-locked oscillation circuit with variable oscillation frequency. 11... Input terminal, 12... Sampling phase detector, 13... Low pass filter (LPF), 14.1
4'... Voltage controlled oscillator (VCO), 15... Output terminal, 16... Input terminal, 17... Addition circuit, 41
...Input terminal, 42...Phase comparator, 43...Low pass filter (LPF), 44...Voltage controlled oscillator (VCO), 45...Output terminal, 46...Variable component Peripheral organs.

Claims (1)

[Claims] (1) A sampling phase detector into which a reference signal is input to one input terminal; a low-pass filter that removes high-frequency components from the output signal of this sampling phase detector; a voltage controlled oscillator whose oscillation frequency is set using the output signal of the sampling phase detector as a control signal, and whose oscillator output is feedback-connected to the other input terminal of the sampling phase detector, the voltage controlled oscillator synchronized with the reference signal; In a phase-locked oscillator circuit that generates an oscillator output, an external control voltage that sets the oscillation frequency of the voltage-controlled oscillator is connected to the voltage between the output of the sampling phase detector and the control signal input of the voltage-controlled oscillator. A phase synchronized oscillation circuit characterized by comprising means for adding to or subtracting from a control signal of a controlled oscillator.