JP2003243929A - Voltage-controlled oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a voltage-controlled oscillator for realizing downsizing, a low cost and improvement of noise immunity. <P>SOLUTION: The output stage of an oscillator circuit having an unbalanced signal output is provided with a balun circuit for balance conversion. The balun circuit adopts a tri-plate strip line conductor structure and is configured on a plane of one layer 20c in a mount board 20 of the oscillator circuit. Further, the balun circuit utilizes odd mode electric field coupling between two parallel lines 51, 52. Through the above configuration, external noise, external induction coupling, and radiation or the like can reliably be prevented without the need of a particular shield mechanism. Moreover, by forming the balun circuit on the board 2c in the multi-layered board 20, the mount of other circuit components (or a circuit pattern 21) can be made in common so as to avoid a VCO module itself from being upsized, which is a problem of mount of the balun circuit, thereby downsizing an apparatus having the voltage-controlled oscillator mounted. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage controlled oscillator suitable for use in small portable devices such as wireless communication devices and mobile phones.

[0002]

2. Description of the Related Art Conventionally, a voltage controlled oscillator (VCO) module having a single unbalanced high frequency output requires a balanced two-terminal output (generally, in the case of a high frequency, unnecessary radiation from a high frequency circuit is required). In order to suppress the effect of external noise on the RF circuit and the high frequency circuit, the unbalanced signal from the oscillator is used after being converted to a balanced signal. In this case, a chip ceramic laminated transformer coupling type balun component is added to the outside of the VCO module. Alternatively, a method of incorporating this chip balun component in the VCO module has been adopted.

[0003]

By the way, in the case of a laminated transformer coupling type balun component, the primary / secondary coupling method generally uses a multilayer laminated structure of an electromagnetic M coupling transformer type line loop. The size is structurally not negligible for small mobile devices such as mobile phones. Also,
In the case of patterning by M coupling, it is necessary to form a mutual inductance between the primary pattern and the secondary pattern, and stack the layers in multiple layers with a ceramic insulating layer between the primary pattern and the secondary pattern to form an independent component. However, in such a configuration, the number of layers is increased and the shape is enlarged correspondingly, resulting in high cost.

From the above, when adding balun parts to a small portable device or the like having a limited mounting area, in the structure using an external substrate, the size of the external substrate is a constraint for downsizing, and in addition, the chip balun is used. However, since it is a coupled coil structure and is susceptible to external noise, a shield mechanism for blocking noise is also required. Further, in the structure to be mounted inside the VCO module, the increase in the height and area of the VCO module is a constraint for downsizing.

As disclosed in Japanese Unexamined Patent Publication No. 2001-185951, there is a structure in which a VCO substrate is composed of a ceramic multilayer laminated substrate and a balun circuit conductor pattern is built in the same substrate. Even if the ceramic multilayer substrate is used, the cost will be significantly higher than that of a normal resin-based material substrate.

According to the present invention, a balun circuit is integrally formed on a predetermined one layer of an oscillator circuit board having a multi-layer structure, so that the voltage control can be made compact, low in price and improved in noise resistance. The purpose is to provide an oscillator.

[0007]

That is, a voltage controlled oscillator according to a first aspect of the present invention is configured by providing a balun circuit for balance conversion in an output stage of an oscillator circuit having an unbalanced signal output, and the balun. The circuit is characterized in that it has a triplate strip line conductor structure and is formed on the same plane in one layer in the mounting substrate of the oscillation circuit. In this way, by constructing the oscillation circuit board in multiple layers and adopting the triplate strip line structure in which the balun circuit is mounted between the ground conductor surfaces of the upper and lower two layers, a conventional shield mechanism is provided. External noise, without using
External inductive coupling and radiation can be reliably prevented. Further, by forming this balun circuit on the same substrate in the multi-layer substrate, it is possible to share mounting with other circuit elements (or circuit patterns), and it is possible to avoid increasing the size of the VCO module itself due to mounting of the balun circuit. Therefore, the size of the device can be reduced.

The invention described in claim 2 is the same as claim 1.
In the voltage controlled oscillator according to, the balun circuit is
It is characterized by being configured by odd-mode electric field coupling of parallel two lines. When balanced two lines are arranged close to each other in a high frequency circuit, coupling occurs between the lines. There are two modes of combination, even mode and odd mode,
The present invention proposes a balun circuit that actively utilizes such coupling between lines, particularly by odd mode coupling. Since the balanced two-line pattern (balloon pattern) forming the balun circuit can be easily formed on the same plane, it is not limited by the expensive ceramic multilayer laminated substrate required for the conventional multilayer laminated coil transformer coupling and is inexpensive. A resin-based material substrate can be used, and a significant cost reduction can be achieved.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the voltage controlled oscillator according to the present invention will be described below with reference to FIGS.

FIG. 1 shows the circuit configuration of the voltage controlled oscillator according to this embodiment. According to FIG. 1, this voltage controlled oscillator 1 (VCO 1) comprises a resonant circuit 2 that determines the oscillation frequency.
An oscillation circuit 3 for continuing oscillation at the oscillation frequency set by the resonance circuit 2, a buffer output circuit 4, an unbalanced-balanced conversion balun circuit 5, and the like.

Here, the resonance circuit 2 has a control voltage Vc.
Is input, and strip line SP, capacitor C1,
It has a resonance part composed of C3, a varicap diode Cv, etc., and the resonance frequency of this resonance part determines the oscillation frequency of the voltage controlled oscillator output. Incidentally, the inductance of the strip line SP is L, and the capacitors C1 and C3 are
And the combined capacitance of the varicap diode Cv is C, the resonance frequency F of the resonance part is F = 1 / 2π√LC. Therefore, by changing the input control voltage Vc and adjusting the capacitance of the varicap diode Cv, the VCO1
The oscillation output frequency of can be controlled arbitrarily.

The oscillation circuit 3 includes an oscillation transistor Q1.
And connecting capacitors C4 and C5 between the base and GND of the oscillating transistor Q1 to form a feedback loop of an oscillating signal, and connecting the resonance circuit 2 to the base side of the oscillating transistor Q1 via a coupling capacitor C2. By connecting them, a Colpitts type oscillation circuit is constructed.

The output circuit 4 comprises an output transistor Q2 cascade-connected to the collector of the oscillation transistor Q1, power-amplifies the oscillation signal from the oscillation circuit 2, and outputs a single unbalanced oscillation output from the collector side. Output.

The resistor R4 is a resistor for current control for controlling the operating current (DC current) of the oscillation transistor Q1 and the output transistor Q2 connected in cascade. Further, the voltage division of the bias circuit by the bias resistors R1, R2 and R3 connected in series to the power supply voltage Vcc is supplied as a DC bias voltage to the bases of the transistors Q1 and Q2 forming the oscillator circuit 3 and the output circuit 4, respectively. The power of the oscillation output is suitably controlled by the resistor 4 and the bias voltage.

The balun circuit 5 includes an output transistor Q.
A circuit for achieving impedance matching of the unbalanced oscillation output output from the two collectors.
Obtain UTN and OUT P.

Although not shown, conventionally, because of impedance matching between the output transistor and a single unbalanced oscillation output,
Output transistor Q2 collector, output resonance circuit, and C
(Capacity) or M (electromagnetic) coupled impedance conversion circuit was used to obtain unbalanced output, and an unbalanced-balanced output balun circuit was added to obtain balanced oscillation output.
According to the present invention, the output matching circuit is formed by integrating the output resonance circuit and the balun circuit having terminals for balanced oscillation output.

That is, in this embodiment, the balun circuit 5 has a primary side line 51 having ground potentials at the center points a and b, respectively.
A parallel output resonance circuit (equivalently formed by a λ / 2 resonance line) is formed by the balanced two lines of the secondary side line 52 and the capacitors C6 and C7 connected in parallel to these lines. The electric field is coupled in the mode. The balanced double lines 51 and 52 are specifically configured by a conductor pattern formed in a strip shape on a multilayer substrate, which will be described later. The balun circuit 5 is made the same by utilizing the electric field coupling by the odd mode. It can be easily constructed on a plane.

FIG. 5 shows a structure of a multi-layer substrate 20 forming a module of the VCO 1, and each layer uses an inexpensive resin material substrate.

In the figure, the upper surface of the uppermost layer indicated by reference numeral 20a is a component mounting surface, and each electronic component element P constituting the VCO 1
(Surface mounting chip parts such as resistors, capacitors, transistors, and varicap diodes) are mounted.

A ground conductor pattern GND1 is formed on almost the entire upper surface of the intermediate layer indicated by reference numeral 20b.

Further, on the upper surface of the lowermost layer shown by the reference numeral 20c, a pattern 21 constituting the above-mentioned resonance circuit (2) such as a strip line (SP) and a power supply system line is formed, and on the same substrate. A balanced two-line pattern (balloon pattern) composed of a primary-side line 51 and a secondary-side line 52 that form the balun circuit 5 is formed on the output side of the secondary-side line 52. And O
UT P is formed. In addition, reference numeral a and reference numeral b
Indicates the center point of each line 51, 52. 3 and 4 show pattern examples of the balanced double lines 51 and 52. FIG. 3 shows a balanced double line having a short line length, and FIG. 4 shows a balanced line pattern having a long line length. There are two lines. The line length of each pattern is determined according to the oscillation frequency of the VCO 1, and the VC with a high oscillation frequency is used.
For O1, the balun pattern of FIG. 3 is used, and when the oscillation frequency is relatively low, the balun pattern of FIG. 4 may be used.

A ground conductor pattern GND2 is formed on almost the entire back surface of the substrate 20c, and these three layers 20a, 20b, and 20c are laminated to form the ground conductor pattern GND2, as shown in the sectional view of FIG. The balun circuit 5 (that is, the balanced two-line pattern 51, 52) has two upper and lower layers.
A triplate strip line structure arranged between the GND conductor planes of 0b and 20c is constructed. The shield effect makes it possible to reliably prevent external noise, external inductive coupling, radiation, and the like.

Further, in the conventional unbalanced-balanced balun circuit, the output resonance circuit is individually required. However, the balun circuit of the present invention can share the output resonance circuit, and unnecessary electric Insertion loss is reduced and VCO
The size of the module can be avoided.

[0024]

As described above, according to the present invention as set forth in claim 1, a balun circuit for balance conversion is provided in the output stage of the oscillator circuit, and the balun circuit has a triplate strip line conductor structure. Since it is configured to be formed on one and the same plane in the mounting substrate, it is possible to reliably prevent external noise, external inductive coupling, radiation, etc. without using a conventional shield mechanism. Further, by forming this balun circuit on the same substrate in the multi-layer substrate, it is possible to share mounting with other circuit elements (or circuit patterns), and it is possible to avoid increasing the size of the VCO module itself due to mounting of the balun circuit. It is possible to miniaturize the motherboard of a small portable device such as a wireless communication device, a mobile phone, etc. in which the voltage controlled oscillator is incorporated.

According to the present invention as defined in claim 2,
Since the balun circuit is configured by the odd-mode electric field coupling of the parallel two lines, the balun pattern can be easily formed on one layer within the same plane in the multilayer substrate, and as described above, other circuit elements (or circuit patterns) can be formed. ) Can be shared with the implementation. By adopting such an integrated built-in structure, it is possible to use an inexpensive resin-based material substrate without being restricted by the expensive ceramic multi-layer laminated substrate required for the conventional multi-layer laminated coil transformer coupling, resulting in a significant cost reduction. Can be down.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a voltage controlled oscillator according to the present invention.

FIG. 2 is a cross-sectional view of a multilayer substrate that constitutes the voltage controlled oscillator module of the present invention.

FIG. 3 is a diagram showing a balloon pattern.

FIG. 4 is a view showing a balloon pattern different from that in FIG.

FIG. 5 is an exploded perspective view of a multilayer substrate that constitutes the voltage controlled oscillator module of the present invention.

[Explanation of symbols]

1 Voltage controlled oscillator (VCO) 2 resonance circuit 3 oscillator circuits 4 output circuits 5 balun circuit

Claims (2)

[Claims] 1. A balun circuit for balanced conversion is provided at an output stage of an oscillator circuit having an unbalanced signal output, and the balun circuit has a triplate strip line conductor structure, and the balun circuit has a triplate strip line conductor structure. A voltage-controlled oscillator characterized in that it is formed on one and the same plane in a mounting substrate. 2. The voltage controlled oscillator according to claim 1, wherein the balun circuit is configured by an odd mode electric field coupling of parallel two lines.