JPH05129950A - Pll frequency synthesizer - Google Patents

Abstract

PURPOSE:To realize an integrated PLL frequency synthesizer with the circuit configuration giving less effect onto a high frequency circuit. CONSTITUTION:The synthesizer is provided with a terminal 70a through which the high frequency circuit power supply voltage HFVcc of a comparatively high voltage is received and it is applied to a VCO 5, a terminal 70b through which a digital circuit power supply voltage SVcc is received and it is applied to a phase comparator circuit 3c or the like and a terminal 70c. Then the power supply voltage OSCVcc of a low voltage is received through the terminal 70c and fed to a basic oscillation circuit 2, etc., to attain a conventional operation, while undesired effect on a high frequency circuit 1 is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PLL frequency synthesizer, and more particularly to an electronic device used in audio equipment such as mini-components, radio-cassettes, televisions, video equipment such as CATT / TV, receiving devices such as cable broadcasting and radio. The present invention relates to an integrated PLL frequency synthesizer for a tuning tuner.

[0002]

2. Description of the Related Art A crystal oscillator is usually used for an oscillation circuit which generates an oscillation signal of an accurate frequency. However, the crystal oscillator is expensive and large in size. Therefore,
It is preferable that the number of types of oscillation signals required is small, but if a large number of oscillation signals are required, arranging the oscillation circuits by the number of oscillation signals is restricted in terms of cost and size. Even in such a case, it is rare that all the oscillation signals are used at the same time, and in most cases, a selected small number of oscillation signals are used. For example, in the generation of a local oscillation frequency signal for a frequency mixing circuit of an electronic tuning tuner, a large number of accurate oscillation signals of several tens or more different in frequency are required. Is one of.

Here, the PLL frequency synthesizer has one
In principle, it is possible to generate an oscillation signal having an arbitrary rational multiple frequency from two fundamental frequency signals. Therefore, it is often used for generation of such a local oscillation frequency signal, and the above-mentioned constraint is applied. It replaces the numerous oscillator circuits that require the accompanying crystal oscillator. This will be described below with reference to a specific example with reference to the drawings. FIG. 4 is a block diagram of an electronic tuning circuit using a conventional PLL frequency synthesizer. 1 is a high frequency circuit, 2 is a basic oscillation circuit, 3 is a synthesizer circuit, 4 is a low pass filter (hereinafter abbreviated as LPF), 5 is a voltage controlled oscillation circuit (hereinafter abbreviated as VCO), 6 is a microcomputer circuit (hereinafter, (Abbreviated as MPU).

The high frequency circuit 1 comprises a high frequency amplifier circuit 1a and a frequency mixing circuit 1b, and the AM received by the antenna is received.
An intermediate frequency signal of a specific frequency selected by mixing the local oscillation frequency signal FS with a high frequency wave such as a wave or FM wave is output. However, the latter half is not shown. Basic oscillator circuit 2
Is constructed using a crystal oscillator to generate a fundamental frequency signal FB having an accurate period. Synthesizer circuit 3
Includes a variable frequency dividing circuit 3a, a variable frequency dividing circuit 3b, and a phase comparison circuit 3c for comparing the phase and period of the signals frequency-divided by these. Further, a synthesizer control circuit is provided to receive control parameters and the like from the external MPU 6 and determine the frequency division ratio and the like in the frequency divider circuit according to the control parameters and the like.

The LPF4 and VCO5 are variable frequency divider 3
b, together with the phase comparison circuit 3c, form a feedback loop. Then, it receives the signal of the comparison result from the phase comparison circuit 3c and outputs its own so that the comparison result of the frequency-divided signal of the basic frequency signal FB and the frequency-divided signal of the local oscillation frequency signal FS becomes equal. The frequency of the local oscillation frequency signal FS which is a signal is increased or decreased. Although detailed configuration is omitted in the figure, the MPU 6 usually includes a microcomputer, an interface, etc., and sets necessary control parameters to the synthesizer circuit 3 and monitors the state thereof.

Under such a configuration, when the MPU 6 selects and determines one tuning frequency, the electronic tuning circuit of the above-mentioned feedback loop, that is, the PLL (phase lock loop), receives a parameter according to the selected tuning frequency. By the function, the local oscillation frequency signal FS having the correct frequency corresponding to the selection is generated from the fundamental frequency signal FB having the one correct frequency. In this way VCO5
The local oscillation frequency signal FS output from is sent to the frequency mixing circuit 1b, where it is used to select an intermediate frequency signal.

Since the PLL frequency synthesizer for generating the local oscillation frequency signal FS from the basic frequency signal FB is widely used in the electronic tuning tuner and the like as described above, the demand thereof is also great.
It is made into an IC and generally supplied. The target part of this IC is the basic oscillator circuit 2, the synthesizer circuit 3, the LPF.
4, a PLL frequency synthesizer circuit including VCO 5 and the like. However, crystal oscillators, capacitors with large capacitance, drive transistors with high-speed and large-drive capacity are ICs.
Since it cannot be converted, it will be externally attached. In the example of FIG. 4, electronic tuning P when the frequency mixing circuit 1b which is a part of the high frequency circuit 1 is further integrated in the same IC.
The LL frequency synthesizer IC7 is indicated by a broken line.

[0008]

In the circuit having such a configuration, the high frequency circuit 1 and the VCO 5 are required to have high speed and noise resistance, and thus require a relatively high power supply voltage HFVcc. If the power supply voltage HFVcc is low, the sensitivity and dynamic range are lowered, the selectivity is lowered, and interference easily occurs, so that 9V, 12V or the like is used. On the other hand, the synthesizer circuit 3 is a digital circuit, and usually has a power supply voltage SVcc of about 5V, which is the same as the power supply voltage MPUVcc for the MPU 6, due to the relationship such as matching with the external MPU 6.

Therefore, the electronic tuning PLL frequency synthesizer IC7 is provided with two power supply terminals 7a and 7b. And an electronically tuned PLL frequency synthesizer IC
7 receives the power supply voltage HFVcc from the outside through the terminal 7a and supplies it to the VCO 5 and the frequency mixing circuit 1b,
Further, it operates by receiving a power supply voltage SVcc from the outside through the terminal 7b and supplying it to the basic oscillation circuit 2 and the synthesizer circuit 3. However, since the PLL frequency synthesizer and the high frequency circuit are closely related to each other, the signal in the high frequency circuit and the local oscillation frequency signal FS are propagated through a long wiring from the viewpoint of noise resistance and the like. Since they are difficult, they are necessarily arranged close to each other, and in some cases, they may be partially mixed as described above.

Therefore, undesired influences due to radiation, sneaking, and the like are likely to be exerted on each other, and in particular, harmonic components from a fundamental oscillator circuit that rapidly and rapidly switches have a large influence on a high-frequency circuit. This is a problem because it causes an increase in tuning tuner development and design man-hours and a decrease in device performance and reliability. An object of the present invention is to solve the above-mentioned problems of the prior art, to realize a circuit configuration of a PLL frequency synthesizer having a small influence on a high frequency circuit, and to provide a high-performance electronic tuning PLL frequency synthesizer IC. It is to be.

[0011]

A PLL frequency synthesizer having the structure of the present invention that achieves the above object is a PL frequency synthesizer.
A basic oscillator circuit that constitutes L, a variable frequency divider circuit, a phase comparator circuit, a low-pass filter, and a voltage-controlled oscillator circuit are integrated in the IC, and the first, second, and third terminals are provided to generate the basic oscillator circuit. The fundamental frequency signal is divided by a first dividing ratio set externally, and the local oscillation frequency signal generated by the voltage controlled oscillator circuit is divided by a second dividing ratio set externally. Compare the frequency-divided signals of in the phase comparison circuit,
The local oscillation frequency signal for the high frequency circuit is generated by the PLL that controls the voltage controlled oscillation circuit so that the comparison results are equal, and the first power supply voltage from the outside via the first terminal is voltage controlled. An oscillator circuit (or the voltage-controlled oscillator circuit and the high-frequency circuit) is supplied, a second power supply voltage from the outside via a second terminal is supplied to the phase comparison circuit, and an external source via the third terminal is supplied. The third power supply voltage is supplied to the basic oscillation circuit.

A PLL frequency synthesizer having another structure of the present invention has a basic oscillator circuit, a variable frequency divider circuit, a phase comparator circuit, a low-pass filter and a voltage controlled oscillator circuit, which compose the PLL, integrated in an IC. The first oscillation frequency signal generated by the fundamental oscillation circuit is divided by the externally set first frequency division ratio to provide the local oscillation frequency signal generated by the voltage controlled oscillation circuit. A PLL that divides by a second dividing ratio set from the outside, compares these divided signals by a phase comparison circuit, and controls the voltage controlled oscillation circuit so that the comparison results are equal, The local oscillation frequency signal for a high frequency circuit is generated, and a first power supply voltage from the outside through a first terminal is supplied to the voltage controlled oscillation circuit (or the voltage controlled oscillation circuit and the high frequency circuit), First A second power supply voltage from the outside via the terminal of is supplied to the phase comparison circuit, a step-down circuit is built in between the second and third terminals, and a smoothing circuit is connected to the outside via the third terminal. , The voltage of the third terminal is supplied to the basic oscillation circuit as a third power supply voltage.

Further, a PLL frequency synthesizer having another structure of the present invention is such that a basic oscillating circuit, a variable frequency dividing circuit, a phase comparing circuit, a low-pass filter and a voltage controlled oscillating circuit which compose the PLL are integrated in an IC. First, second, third
And dividing the basic frequency signal generated by the basic oscillation circuit by a first frequency division ratio set from the outside, and the local oscillation frequency signal generated by the voltage controlled oscillation circuit from the second frequency ratio set from the outside. The local oscillation for the high frequency circuit is performed by a PLL that divides the divided signal by a frequency division ratio, compares the divided signals by a phase comparison circuit, and controls the voltage controlled oscillation circuit so that the comparison results become equal. A frequency signal is generated and a first power supply voltage from the outside via a first terminal is supplied to the voltage controlled oscillator circuit (or the voltage controlled oscillator circuit and the high frequency circuit), and first and second terminals are provided. A first smoothing circuit is connected to the outside via a second terminal and a first step-down circuit is provided between the first smoothing circuit and the second smoothing circuit. The second step-down voltage circuit is built in between the second and third terminals. To the outside through the terminal and supplies to the fundamental oscillation circuit voltage of the second third terminal is connected to the smoothing circuit as the third power supply voltage. However, in any of these configurations, the crystal oscillator, the capacitor having a large capacitance, the driving transistor having a high speed and a large driving capability, and the like cannot be integrated in the IC and are therefore externally attached.

[0014]

In the PLL frequency synthesizer of the present invention having such a configuration, different power supply voltages are supplied to the three terminals or generated by stepping down. And
These voltages are supplied to the voltage controlled oscillator circuit at one terminal being relatively high, for example, 9 to 12V for the high frequency circuit, and those at the other terminals are lower than that, for example, about 5V, and the phase It is supplied to the comparison circuit,
At another terminal is even lower, for example 3
It is about V and is supplied to the basic oscillation circuit.

Therefore, the local oscillation frequency signal output from the voltage controlled oscillator operating at the same power supply voltage as that of the high frequency circuit has good matching with the high frequency circuit, and the synthesizer circuit including the phase comparison circuit is for a normal digital circuit. Since it operates with the power supply voltage of the low-pass filter and the voltage-controlled oscillation circuit, it has good compatibility with the digital circuit that controls external control, and the voltage difference between the power-supply voltage of the synthesizer circuit and that of the voltage-controlled oscillation circuit is not large. Can also be driven. Furthermore, since the basic oscillator circuit oscillates under a power supply voltage that is lower than conventional ones, the energy level of the interfering waves dissipated during switching is small, and the power supply voltage difference with the synthesizer circuit is not large, so the basic oscillator circuit Is capable of working with synthesizer circuits. That is, the integrated-circuit PLL frequency synthesizer of the present invention can operate in the conventional manner and has a small undesired effect on the high frequency circuit.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the PLL frequency synthesizer having the structure of the present invention will be described below. FIG. 1 is a block diagram of an electronic tuning circuit as an embodiment to which the PLL frequency synthesizer is applied, and corresponds to FIG. 4 of a conventional example. Here, 1 is a high frequency circuit, 2 is a basic oscillation circuit, 3 is a synthesizer circuit, 4 is a low pass filter (LPF),
Reference numeral 5 is a voltage controlled oscillator (VCO), and 6 is a microcomputer circuit (MPU).

Further, an electronic tuning PL shown by a broken line
The L frequency synthesizer IC 70 is a PL including a basic oscillator circuit 2, a synthesizer circuit 3, an LPF 4, and a VCO 5.
The L frequency synthesizer circuit is provided in one IC. However, crystal oscillators, high-capacity capacitors, high-speed, high-driving drive transistors, etc.
Since it cannot be converted to C, it is externally attached (in the figure, a capacitor is shown as a typical example). In addition, in the example of FIG.
Similar to the conventional example, the frequency mixing circuit 1b which is a part of the high frequency circuit 1 is also integrated in the same IC. However, the number of power supply terminals of the IC is increasing, and there are three kinds of power supply voltages HFVcc, SVcc, OSCVcc supplied from the outside.
It is provided with three terminals 70a, 70b, 70c for receiving.

The high frequency circuit 1 has an AM received by the antenna.
Of the high frequency amplifier circuit 1a for amplifying the high frequency and the high frequency amplifier circuit 1a for selecting the intermediate frequency signal. The frequency mixing circuit 1b that mixes the local oscillation frequency signal FS with the output is provided. Then, as the power supply voltage, a power supply voltage H of usually 9 V to 12 V is used.
It operates by receiving FVcc. The basic oscillating circuit 2 is configured by using a crystal oscillator, and generates a basic frequency signal FB having an accurate cycle which is hardly affected by temperature changes and aging changes due to its function. Since the basic oscillation circuit 2 operates by receiving the power supply voltage OSCVcc of about 3V as a power supply voltage, noise energy at the time of switching is small and interference to the high frequency circuit 1 is small.

The synthesizer circuit 3 has a fundamental frequency signal F
A variable frequency dividing circuit 3a for frequency-dividing B, a variable frequency dividing circuit 3b for frequency-dividing the local oscillation frequency signal FS, and a phase comparison circuit 3c for comparing the phase and period of these frequency-divided signals are provided. .. Furthermore, with a synthesizer control circuit,
The control parameters and the like from the external MPU 6 are received, and the frequency division ratios and the like in the frequency dividing circuits 3a and 3b are determined accordingly. The power supply voltage is usually about 5V
Since it operates by receiving cc, it has the same power supply voltage MPUVcc
Of the power supply voltage HFVcc and the power supply voltage OSCVcc, the difference between these voltages is small and the basic oscillator circuit 2 and the LPF4 and VCO5 can cooperate with each other.

The LPF 4 receives the comparison result signal from the phase comparison circuit 3c, removes undesired components on the high frequency side, and generates a control signal to the voltage controlled oscillation circuit 5. The VCO 5 outputs its own local oscillation signal according to the control signal from the LPF 4, that is, according to the comparison result of the frequency-divided signal of the fundamental frequency signal FB and the frequency-divided signal of the local oscillation frequency signal FS. The frequency of the frequency signal FS is increased or decreased so that the comparison results are equal. As a power supply voltage, the high-frequency circuit 1 receives the same power-supply voltage HFVcc as the power-supply voltage and operates, so that it has good compatibility with the high-frequency circuit 1 and therefore does not deteriorate the performance of the high-frequency circuit.

Although the detailed structure of the MPU 6 is omitted in the figure, it is usually equipped with a microcomputer and the like, and also performs input by the operation of the device and output for display, etc. The ratio or the like is set in the synthesizer circuit 3, and its state, for example, whether or not the PLL is locked is monitored. As the power supply voltage, the power supply voltage MPUVcc of about 5V which is the same as the normal power supply voltage SVcc
Receives and operates.

Under such a structure, when the tuning frequency is selected in the MPU 6, the electronic tuning circuit starts from the fundamental frequency signal FB having one accurate frequency and locally oscillates at the correct frequency corresponding to the selection. The frequency signal FS can be generated. More specifically, when the tuning frequency is selected in the MPU 6 and one frequency is determined, the control parameter corresponding to the selected frequency is set in the synthesizer circuit 3. As a result, the frequency division ratios of the variable frequency dividing circuits 3a and 3b are determined. In this state, the frequency of the local oscillation frequency signal FS is controlled by the feedback loop formed by the variable frequency dividing circuit 3b, the phase comparison circuit 3c, the LPF 4, and the VCO 5, and the ratio of the frequency division ratio from the fundamental frequency signal FB of the accurate frequency is controlled. Local oscillation frequency signal F having a frequency that exactly follows
S is generated. Basic frequency signal FB is 10.24 MH
As a specific numerical example of z, when 16.27 MHz is desired for the local oscillation frequency signal FS, frequency division ratios 2048 and 3254 are set in the variable frequency dividing circuits 3a and 3b, respectively, and when 16.725 MHz is desired. Variable frequency divider 3
The frequency division ratios 2048 and 3345 may be set to a and 3b, respectively.

The local oscillation frequency signal FS thus output from the VCO 5 is sent to the frequency mixing circuit 1b, mixed with the amplified high frequency therein, and used for selecting the intermediate frequency signal. Therefore, the electronic tuning circuit using the electronic tuning PLL frequency synthesizer IC 70 of the present invention can perform the same signal processing as the conventional one, and moreover, the interference wave from the basic oscillation circuit 2 to the high frequency circuit 1 is generated. The performance is improved by the reduced amount. It is not necessary to operate all the elements of the synthesizer circuit 3 at the power supply voltage SVcc. For example, the variable frequency dividing circuit 3a and the like have the same power supply voltage OSCVcc as the basic oscillation circuit 2.
The same effect can be obtained by operating with.

An embodiment of another structure of the present invention is shown in FIG. 2. The difference from the embodiment of FIG. 1 is that a smoothing circuit composed of a capacitor Cc or the like is externally connected via a terminal 70c. That is, the IC has a step-down circuit including a resistor Rc and the like between the terminals 70b and 70c. With such a configuration, the power supply voltage OS in the embodiment of FIG.
Since a power supply voltage equivalent to CVcc is supplied to the basic oscillation circuit 2 and the like via the terminal 70c, its function and effect are exactly the same as those in the above-mentioned embodiment.

An embodiment of another structure of the present invention is shown in FIG. 3, but the difference from the embodiment of FIG. 1 is that a smoothing circuit composed of a capacitor Cb or the like is externally connected via a terminal 70b. And a capacitor Cc to the outside through the terminal 70c.
Is connected between the terminals 70a and 70b, a step-down circuit including a resistor Rb is provided in the IC between the terminals 70a and 70b, and I is connected between the terminals 70b and 70c.
It is to have a step-down circuit composed of a resistor Rc and the like in C.

With such a configuration, a power supply voltage equivalent to the power supply voltage SVcc in the embodiment of FIG. 1 is supplied to the synthesizer circuit 3 etc. via the terminal 70b, and a power supply voltage equivalent to the power supply voltage OSCVcc is applied to the terminal 70c. Since it is supplied to the basic oscillation circuit 2 and the like via the same, the effects are the same as those in the above-described embodiment. It should be noted that a reference voltage generating circuit composed of a Zener diode or the like is built in the IC in parallel with the built-in step-down circuit or the external smoothing circuit in the above-described other configuration or another configuration example, or at the terminal 70.
It may be connected to the outside via b and 70c.

[0027]

As is apparent from the above description, in the PLL frequency synthesizer of the present invention, the power supply voltage of the basic oscillation circuit that switches at high speed and steeply is lowered to lower its operation level to reduce radiation and radiation. It is possible to suppress an interfering wave due to a harmonic component that causes an undesired influence due to wraparound and the like. As a result, it is possible to provide a high-performance electronic tuning PLL frequency synthesizer IC by realizing a PLL frequency synthesizer with a small influence on the high frequency circuit, and to shorten the electronic tuning tuner development and design man-hours and improve the device performance and reliability. Can also contribute.

[Brief description of drawings]

FIG. 1 is a block diagram of an electronic tuning circuit as an embodiment using a PLL frequency synthesizer having a configuration of the present invention.

FIG. 2 is a block diagram of an electronic tuning circuit as another embodiment using a PLL frequency synthesizer having another structure of the present invention.

FIG. 3 is a block diagram of an electronic tuning circuit as another embodiment using a PLL frequency synthesizer having another structure of the present invention.

FIG. 4 is a block diagram of an electronic tuning circuit using a conventional PLL frequency synthesizer.

[Explanation of Codes] 1 ... High Frequency Circuit 2 ... Basic Oscillation Circuit 3 ... Synthesizer Circuit 4 ... Low Pass Filter Circuit 5 ... Voltage Control Oscillation Circuit 6 ... Microcomputer Circuit 7 ... Electronic Tuning PLL Frequency Synthesizer IC 70 ... Electronic Tuning PLL Frequency Synthesizer IC FB ... Basic frequency signal FS ... Local oscillation frequency signal

Claims (3)

[Claims] 1. A basic frequency signal generated by a basic oscillator circuit is divided by a first frequency division ratio set externally, and a local oscillation frequency signal generated by a voltage controlled oscillator circuit is externally set by a second frequency divider. The local oscillation for the high frequency circuit is performed by a PLL that divides the divided signal by a frequency division ratio, compares the divided signals by a phase comparison circuit, and controls the voltage controlled oscillation circuit so that the comparison results become equal. In an integrated PLL frequency synthesizer that generates a frequency signal, the first, second, and third terminals are provided, and the first power supply voltage from the outside via the first terminal is applied to the voltage controlled oscillation circuit (or , The voltage controlled oscillator circuit and the high frequency circuit), and supplies a second power supply voltage from the outside through a second terminal, which is lower than the first power supply voltage, to the phase comparison circuit, Lower than voltage, third A PLL frequency synthesizer characterized by supplying a third power supply voltage from the outside via a terminal to the basic oscillation circuit. 2. A basic frequency signal generated by a basic oscillation circuit is divided by a first frequency division ratio externally set, and a local oscillation frequency signal generated by a voltage controlled oscillation circuit is second externally set. The local oscillation for the high frequency circuit is performed by a PLL that divides the divided signal by a frequency division ratio, compares the divided signals by a phase comparison circuit, and controls the voltage controlled oscillation circuit so that the comparison results become equal. In an integrated PLL frequency synthesizer that generates a frequency signal, the first, second, and third terminals are provided, and the first power supply voltage from the outside via the first terminal is applied to the voltage controlled oscillation circuit (or , The voltage controlled oscillator circuit and the high frequency circuit) and supplies a second power supply voltage from the outside through a second terminal, which is lower than the first power supply voltage, to the phase comparison circuit, A step-down circuit between the 3 terminals A PLL frequency synthesizer which is built-in, has a smoothing circuit connected to the outside through a third terminal, and supplies the voltage of the third terminal as a third power supply voltage to the basic oscillation circuit. 3. A basic frequency signal generated by a basic oscillator circuit is divided by a first frequency division ratio externally set, and a local oscillation frequency signal generated by a voltage controlled oscillator circuit is second externally set. The local oscillation for the high frequency circuit is performed by a PLL that divides the divided signal by a frequency division ratio, compares the divided signals by a phase comparison circuit, and controls the voltage controlled oscillation circuit so that the comparison results become equal. In an integrated PLL frequency synthesizer that generates a frequency signal, the first, second, and third terminals are provided, and the first power supply voltage from the outside via the first terminal is applied to the voltage controlled oscillation circuit (or , The voltage-controlled oscillator circuit and the high-frequency circuit), and the first step-down circuit is built in between the first and second terminals.
The first smoothing circuit is connected to the outside through the terminal of the second terminal, the voltage of the second terminal is supplied to the phase comparator circuit as the second power supply voltage, and the second step-down circuit is provided between the second and third terminals. And a second smoothing circuit connected to the outside through a third terminal, and the voltage at the third terminal is supplied to the basic oscillation circuit as a third power supply voltage.