JP2005101964A - High frequency multiple oscillation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem of a conventional crystal oscillation circuit of a 185 MHz band that the target spurious characteristic of -40dB or below cannot be obtained when an amplifier circuit comprising a common collector amplifier circuit and a buffer circuit apply a multi-stage multiple amplification to an output frequency of the crystal oscillation circuit for an impedance matching purpose between stages to be going to obtain a high frequency oscillation output of 700 MHz band. <P>SOLUTION: A π type impedance matching circuit 108a configured with a series circuit of a high pass filter 201 and a low pass filter 202 and whose characteristics are composed is additionally connected to an impedance conversion circuit 109 of prior arts, an impedance matching circuit 108 composing a capacitor C21 of the π type impedance matching circuit 108a and a capacitor C18 of the impedance conversion circuit 109 is used for an output circuit of a high frequency multiple amplifier circuit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to an oscillation circuit, and more particularly to a high-frequency multiplication oscillation circuit having excellent spurious characteristics.

As the transmission speed of the information communication infrastructure increases, the demand for higher frequency for the oscillator that is the clock frequency source is becoming stronger. In order to obtain a high-frequency oscillation output of 200 MHz or higher in a crystal oscillator with high frequency stability, a PLL oscillation circuit, an overtone oscillation circuit, a multiplication circuit, or the like is generally used.
Among these various oscillation circuits, a PLL oscillation circuit using a voltage-controlled handshake (hereinafter referred to as VCO) feeds back an output signal of a VCO that oscillates in a desired high frequency region, and has an internal reference with high frequency stability. By comparing the phase with a signal (crystal oscillator or the like), the stability of the high frequency output is maintained.
Since the output signal of the phase comparator provided inside contains a large amount of alternating current components, a loop filter is required to remove frequency components in unnecessary regions. However, outside the loop filter band, the PLL oscillation circuit The phase noise characteristic is deteriorated.
On the other hand, in the case of a voltage-controlled crystal oscillator using an overtone oscillation circuit (hereinafter referred to as VCXO), the frequency variable sensitivity deteriorates in proportion to the square of the overtone order, so the frequency control range should be widened. It becomes difficult.

Therefore, it can be said that VCXO using a multiplication method is most suitable for widening the frequency control range and obtaining good phase noise characteristics. In the VCXO of the multiplication method, a SAW filter using a SAW filter has recently been proposed as a frequency selection means for selecting a desired high-frequency component. However, considering the degree of freedom of design change and cost, the SAW filter It is more advantageous to adopt a frequency selection circuit using a coil and a contentor than to a circuit.

There is a VCXO disclosed in Japanese Patent Application No. 2003-111156 as a conventional example of a VCXO by a multiplication method using a coil and a capacitor as a frequency selection circuit.
FIG. 4 is an electric circuit diagram showing the VCXO disclosed in the same issue again. As shown in the figure, this VCXO is based on an output signal of the Colpitts crystal oscillation circuit 101, a frequency selection circuit 102 which is a resonance circuit of an inductor L1 and a capacitor C3, and a frequency selection circuit which is a resonance circuit of an inductor L2 and a capacitor C5. 103, only the desired frequency is extracted, impedance matching is performed by the next collector grounded amplifier circuit 104, the output level is increased by the next grounded emitter amplifier circuit 105, and the resonance circuit of the inductor L3 and the capacitor C9. A desired frequency extracted by a frequency selection circuit 106 and a frequency selection circuit 107 which is a resonance circuit of an inductor L4 and a capacitor C11 is output from an OUT terminal via an impedance conversion circuit 109.

The Colpitts-type crystal oscillation circuit 101 has a base bias circuit composed of resistors R1 and R2 connected to the base of the oscillation transistor Ql, and a fixed capacitor C1 constituting a part of the chair capacity between the base and the ground, A series circuit with C2 is connected, and further, a connection midpoint of this series circuit and the emitter of the transistor Q1 are connected, and an emitter resistor R3 is connected.
Further, the base of the transistor Q1 is connected to one end of the crystal resonator Y1, and the other end is grounded.

The grounded collector amplifier circuit 104 has a base bias circuit composed of resistors R4 and R5 connected to the base of the transistor Q2 and an emitter resistor R6 connected between the emitter and the ground, and has a high input impedance and a low output. An impedance matching circuit having an impedance is formed.

The grounded-emitter amplifier circuit 105 has a base bias circuit composed of resistors R7 and R8 connected to the base of the amplifying transistor Q3, and a bias resistor R9 and a bypass capacitor C8 connected between the emitter of the transistor Q3 and the ground. It is grounded at a high frequency and functions as a so-called buffer circuit.

The impedance conversion circuit 109 is connected to a series circuit of fixed capacitors C17 and C18 in parallel with the inductor L5. By taking out the output from the connection middle point of the series circuit, the impedance conversion circuit 109 has an impedance with the output end side at a desired frequency. Adjustments are made to ensure matching.

Capacitors C4, C6, C7, C10, and Cl2 are coupling capacitors, and are set to a small value so that the circuits are loosely coupled to suppress the influence between the circuits in a desired high frequency band as much as possible. The power source Vcc is grounded at a high frequency by a fixed capacitor C16.
Japanese Patent Application No. 2003-11156

However, the circuit shown in FIG. 4 has a circuit configuration corresponding to an oscillation output in the 600 MHz band, and uses a 185 MHz crystal resonator in the oscillation stage in the same circuit configuration in response to the demand for higher frequency for the oscillator. An oscillation circuit that multiplies this oscillation frequency by 4 and outputs an output frequency of 740 MHz is composed of circuit components shown in the circuit constant table of FIG. 5, and its spurious characteristics are measured.
The result was −32 dB as shown in the spurious characteristic diagram of FIG. That is, the circuit configuration shown in FIG. 4 has a problem that it is difficult to configure a target oscillation circuit that is a 700 MHz band oscillation circuit and has a spurious rejection rate of −40 dB or less.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a high-frequency multiplier oscillation circuit that can obtain excellent spurious characteristics with a simple circuit configuration.

In order to solve the above-described problem, in claim 1, a high-frequency multiplication oscillation circuit that obtains a high-frequency output signal of a desired frequency by a multi-stage multiplication amplification circuit, and a series circuit of a high-pass filter circuit and a low-pass filter circuit in an output section By adding the above, the impedance matching between the high-frequency multiplier oscillation circuit and the load circuit is performed to improve the spurious characteristics.
According to a second aspect of the present invention, in the high frequency multiplied oscillation circuit according to the first aspect, the high frequency multiplied oscillation circuit is used for impedance matching between an oscillation stage using a piezoelectric vibrator having a resonance frequency of 180 MHz and between the stages. A high frequency multiplying oscillation circuit configured by a grounded collector amplifier circuit and a buffer circuit, which multiplies the oscillation stage output by 4 and outputs a signal having an output frequency of 700 MHz band.

In the crystal oscillation circuit of the present invention, an impedance matching circuit composed of a series circuit of a high-pass filter circuit and a low-pass filter circuit is added to the output part of the conventional high-frequency multiplication oscillation circuit, thereby the high-frequency multiplication oscillation circuit and the load circuit For example, in an oscillation circuit that obtains a 740 MHz oscillation output by multiplying the 185 MHz oscillation circuit output by four, a spurious elimination characteristic of −40 dB is obtained. Improvement results were obtained.
As a result, the present oscillation circuit has a great effect in providing an oscillator having a predetermined spurious characteristic with a simple circuit with respect to a crystal oscillator with higher frequency.

Hereinafter, the present invention will be described based on embodiments shown in the drawings. 1A and 1B are diagrams showing an embodiment of a 470 MHz high frequency multiplication oscillator according to the present invention. FIG. 1A is an electric circuit diagram, and FIG. 1B is a circuit constant table of the circuit.
As shown in FIG. 5A, this oscillation circuit includes a Colpitts crystal oscillation circuit 101, frequency selection circuits 102 and 103, a grounded collector amplification circuit 104, a grounded emitter amplification circuit 105, a frequency selection circuit 106, 107 and an impedance matching circuit 108.
The functional operation of the Colpitts crystal oscillation circuit 101, frequency selection circuits 102 and 103, grounded collector amplification circuit 104, grounded emitter amplification circuit 105, and frequency selection circuits 106 and 107 of this oscillation circuit is the same as that of the conventional oscillation circuit shown in FIG. This is the same as the functional operation of each component with the same reference numeral. The impedance matching circuit 108 is configured as described below as a feature of the oscillation circuit of the present invention.
Therefore, the description of the common parts with FIG. 4 is omitted, and the functional operation of the impedance matching circuit 108 will be mainly described.

FIG. 2 is a circuit diagram illustrating the configuration of the impedance matching circuit 108.
As shown in FIG. 4A, the basic configuration of the impedance matching circuit 108 is the same as the impedance conversion circuit 109 of FIG. 4 except that it includes a high-pass filter 201 including a capacitor C21 and an inductor L21, an inductor L22, and a capacitor C22. The circuit configuration is such that an impedance matching circuit 108a configured by a series circuit with the low-pass filter 202 is connected.
The high-pass filter 201 forms a matching circuit in which impedance matching is established between the output impedance at the output (OUT) end of FIG. 4 and a reference impedance, and the low-pass filter 202 is configured to match the reference impedance and the oscillation circuit. A matching circuit having impedance matching with the load impedance is formed.
The high-pass filter 201 and the low-pass filter 202 synthesize the inductors L21 and L22 so that only a predetermined frequency band shown in FIG. 2B passes through the capacitors C21 and 22 and the inductor L23. Type impedance matching circuit 108a.

The impedance matching circuit 108a is connected to the output terminal of the impedance conversion circuit 109 in FIG. 4A, and the capacitor C18 of the impedance conversion circuit 109 and the capacitor C21 of the additional impedance matching circuit 108a are synthesized. This circuit is the impedance matching circuit 108 of FIG.
With the above configuration, impedance matching between the oscillation circuit and the load can be performed with high accuracy, and spurious can be more reliably removed.

FIG. 3 is a spurious characteristic diagram of FIG. 1B showing a high frequency multiplication oscillation circuit that obtains an oscillation output of 740 MHz by multiplying the oscillation circuit output by 4 using a crystal resonator having a resonance frequency of 185 MHz.
As shown in the figure, a spurious removal characteristic of −40.8 dB was obtained, and an improvement result of about 9 dB was obtained as compared with the spurious characteristic diagram of the conventional circuit (spurious removal rate −32 dB).
Therefore, it can be seen that the impedance matching circuit 108 of FIG. 1 configured based on the π-type impedance matching circuit 108a has an extremely excellent spurious elimination effect in the high-frequency multiplication circuit.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one example of embodiment of the high frequency multiplication oscillator concerning this invention, (a) is an electrical circuit diagram, (b) is a circuit constant table | surface of the circuit. FIG. 6 is a circuit diagram illustrating a configuration of an impedance conversion circuit 108. The spurious characteristic figure in the high frequency multiplication oscillator concerning this invention. The electric circuit diagram which reprinted VCXO disclosed by Japanese Patent Application No. 2003-111156 as a prior art example. The circuit constant table | surface of the 740 MHz oscillation circuit by the circuit structure of FIG. The spurious characteristic figure in 740MHzVCXO by the circuit structure of a prior art example.

Explanation of symbols

101 ··· Colpitts crystal oscillation circuit, 102, 103 · · frequency selection circuit,
104 .. Grounded collector amplifier circuit 105.. Grounded emitter amplifier circuit
106, 107 ... Frequency selection circuit 108, 108a Impedance matching circuit
109 .. Impedance conversion circuit,
C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C21, C22, capacitors,
L1, L2, L3, L4, L5, L6, L21, L22, L23 .. Inductor,
Q1, Q2, Q3 ... Transistors
R1, R2, R3, R4, R5, R6, R7, R8, R9 ... Resistance, Y1 ... Crystal oscillator

Claims (2)

A high-frequency multiplication oscillation circuit that obtains a high-frequency output signal of a desired frequency by a multi-stage multiplication amplification circuit,
A high-frequency multiplication oscillation circuit characterized by adding a series circuit of a high-pass filter circuit and a low-pass filter circuit to the output unit to achieve impedance matching between the high-frequency multiplication oscillation circuit and the load circuit and thereby improving spurious characteristics . The high-frequency multiplying oscillator circuit includes an oscillation stage using a piezoelectric vibrator having a resonance frequency of 180 MHz, a grounded collector amplifier circuit for impedance matching between the stages, and a buffer circuit, and multiplies the output of the oscillation stage by four. 2. The high frequency multiplication oscillator according to claim 1, wherein the high frequency multiplication oscillation circuit outputs a signal having an output frequency of 700 MHz band.

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