JP2002314332A - High frequency oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain satisfactory noise characteristics in a high frequency oscillator built in an integrated circuit. SOLUTION: This high frequency oscillator is provided with an oscillation circuit 2 and a bias circuit 3 built in a semiconductor integrated circuit 1, a resonator 4, an inductor 5 and a capacitor 6, and a resonator connection terminal 7 is grounded through the inductor 5 and the capacitor 6 serially. Then, the low frequency noise components of the bias circuit 3 can be attenuated without attenuating the signal of an oscillation frequency and an oscillation output signal of low noise can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency oscillator for a radio equipment such as a cordless remote controller, a cordless telephone, a portable telephone, etc. ,
The present invention relates to an application requiring a high C / N in an output signal.

[0002]

2. Description of the Related Art A conventional high-frequency oscillator will be described with reference to the drawings. FIG. 6 is a configuration diagram of a conventional high-frequency oscillator.

In FIG. 6, 1 is a semiconductor integrated circuit, 2 is an oscillation circuit, 3 is a bias circuit, 4 is a resonator, 6 is a capacitor, 7 is a resonator connection terminal, 8 is an oscillation output terminal, and 15 is a noise path terminal. is there.

An oscillation circuit 2 and a bias circuit 3 are built in a semiconductor integrated circuit 1. The input of the resonance circuit 2 is connected to a resonator connection terminal 7 which is an external connection terminal of the semiconductor integrated circuit 1. Here, the output of the bias circuit 3 is connected to the input of the oscillation circuit 2, that is, to the resonator connection terminal 7, and provides a bias voltage.

A resonator 4 formed outside the semiconductor is connected to the resonator connection terminal 7. The resonator 4 is a parallel resonator including an inductor and a capacitor. The oscillation circuit 2 oscillates at a frequency determined by the resonance frequency of the resonator 4, and a high-frequency signal is output from the oscillation output terminal 8.

[0006]

However, the conventional high-frequency oscillator has a problem that the noise characteristics of the high-frequency output signal cannot be sufficiently obtained. Alternatively, it is necessary to provide a noise path terminal 14 for connecting the capacitor 6 for removing noise of the bias circuit 3 to the semiconductor integrated circuit 1, which has caused a cost increase.

That is, the bias circuit 3 is composed of a constant current source circuit, a current mirror circuit, and the like, and the constant current circuit contains low frequency noise of several kHz to several hundred kHz. When this noise is applied to the oscillation circuit, a noise component is superimposed on the oscillation output and output from the oscillation output terminal 8. Alternatively, in order to remove the low-frequency noise, the bias circuit 3 is AC grounded through a noise path terminal 15 by a capacitor. In this configuration, a terminal for a noise path is required, and the number of terminals of the semiconductor integrated circuit 1 increases. Therefore, the cost has increased due to an increase in the chip size of the semiconductor integrated circuit 1 and an increase in the number of pins of the package.

[0008]

In order to solve the above-mentioned conventional problems, a high-frequency oscillator according to the present invention comprises an oscillation circuit formed in a semiconductor integrated circuit and an oscillation circuit formed in the semiconductor integrated circuit. A bias circuit that supplies a bias voltage of a resonator connection terminal, a resonator, an inductor, and a capacitor, wherein the resonator connection terminal is connected to the resonator, and the resonator connection terminal is connected to the inductor and the capacitor. Are connected in series to ground or a power supply, and the combined impedance of the inductor and the capacitor is a sufficiently low impedance at the frequency of low-frequency noise included in the output of the bias circuit, and is sufficiently low at the oscillation frequency. The constant is set so that the impedance becomes high.

[0010] Since the inductor and the capacitor are grounded through a series connection, the low frequency noise component of the bias circuit can be attenuated without attenuating the oscillation frequency signal, and a low noise oscillation output signal is obtained. be able to. Also, there is no increase in terminals such as noise path terminals.

[0010]

1 is a block diagram showing a configuration of an oscillation circuit provided in a semiconductor integrated circuit according to a first embodiment of the present invention; A circuit, a resonator, an inductor, and a capacitor, wherein the resonator connection terminal is connected to the resonator, and the resonator connection terminal is connected to a ground or a power supply via the inductor and the capacitor in series. A constant is set so that the combined impedance of the inductor and the capacitor is sufficiently low at the frequency of low-frequency noise included in the output of the bias circuit and sufficiently high at the oscillation frequency. It is. And
Since it is grounded through the series connection of the inductor and the capacitor, the low frequency noise component of the bias circuit can be attenuated without attenuating the signal of the oscillation frequency, and a low noise oscillation output signal can be obtained. Also, there is no increase in terminals such as noise path terminals.

According to a second aspect of the present invention, there is provided an oscillation circuit configured in a semiconductor integrated circuit, a bias circuit configured in the semiconductor integrated circuit for supplying a bias voltage of a resonator connection terminal of the oscillation circuit, A resonator, an inductor,
Comprising a capacitor and a switch, connecting the resonator connection terminal and the resonator, wherein the resonator connection terminal is connected to a ground or a power supply through the inductor, the capacitor and the switch in series, A constant is set so that the combined impedance of the inductor and the capacitor is sufficiently low at the frequency of low-frequency noise included in the output of the bias circuit and sufficiently high at the oscillation frequency, and the switch is set according to the operation state. Is turned on or off. Then, since the grounding of the series connection of the inductance and the capacitor is turned on and off by the switch, the rise time when the power is turned on can be shortened in the off state, and the noise characteristic of the oscillation output signal can be improved by turning it on thereafter.

[0012] The invention described in claim 3 is particularly preferable in claim 2.
The described switch is configured in a semiconductor integrated circuit. Since the switch is provided in the semiconductor integrated circuit, there is no increase in external components. In addition, since the switch is controlled in the semiconductor integrated circuit, wiring such as wiring is not required.

According to a fourth aspect of the present invention, there is provided an oscillation circuit formed in a semiconductor integrated circuit, a bias circuit formed in the semiconductor integrated circuit for supplying a bias voltage of an input terminal of the oscillation circuit, and the semiconductor device. A first capacitor and a switch configured in an integrated circuit, a resonator, an inductor, and a second capacitor, wherein the input terminal is connected to the first capacitor and the switch connected in parallel through the switch. Connected to a resonator connection terminal configured in the semiconductor integrated circuit, connects the resonator connection terminal to the resonator, and connects the resonator connection terminal to ground or a power supply via the inductor and the capacitor in series Wherein the combined impedance of the inductor and the capacitor corresponds to the frequency of low-frequency noise included in the output of the bias circuit. In a sufficiently low impedance oscillation frequency have one in which a constant so that a sufficiently high impedance is set. In addition, a rising characteristic and a noise characteristic can be compatible with a configuration in which an external switch is not required and the number of terminals is not increased.

The invention described in claim 5 is particularly advantageous in claim 1.
Or a resistor is used in place of the inductor described in any one of (4) to (4). Then, the cost can be reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a high-frequency oscillator according to a first embodiment of the present invention. The integrated circuit of this embodiment will be described with reference to FIG.

In FIG. 1, 1 is a semiconductor integrated circuit, 2 is an oscillation circuit, 3 is a bias circuit, 4 is a resonator, 5 is an inductor, 6 is a capacitor, 7 is a resonator connection terminal, and 8 is an oscillation output terminal. .

An oscillation circuit 2 and a bias circuit 3 are built in a semiconductor integrated circuit 1. The input of the resonance circuit 2 is connected to a resonator connection terminal 7 which is an external connection terminal of the semiconductor integrated circuit 1. Here, the output of the bias circuit 3 is connected to the input of the oscillation circuit 2, that is, to the resonator connection terminal 7, and provides a bias voltage.

The resonator 4 formed outside the semiconductor is connected to the resonator connection terminal 7. The resonator 4 is a parallel resonator including an inductor and a capacitor. The oscillation circuit 2 oscillates at a frequency determined by the resonance frequency of the resonator 4, and a high-frequency signal is output from the oscillation output terminal 8.

The resonator connection terminal is grounded via an inductor 5 and a coil 6. Here, the constant is set so that the combined impedance of the inductor 5 and the capacitor 6 is sufficiently low at the frequency of the low-frequency noise included in the output of the bias circuit 3 and sufficiently high at the oscillation frequency. In this embodiment, the inductor is 470 nH and the capacitor is 0.022 uF. This attenuates the low-frequency noise component of the bias circuit of several hundred kHz or less. At this time, since the inductor has a large impedance at the transmission frequency of 400 MHz, the combined impedance becomes large, and the high frequency component is hardly attenuated.

As described above, since it is not necessary to provide a noise path terminal and low frequency noise can be attenuated, a high frequency transmission output signal having a small noise component can be obtained.

In this embodiment, in addition to the low-frequency noise generated from the bias circuit, a low-frequency noise component generated when a demodulation circuit or a logic circuit is incorporated in the semiconductor integrated circuit 1 is given to the oscillator. It is also effective in reducing the effects. Therefore, a voltage is not excited in the wiring structure by a high-frequency signal in the semiconductor integrated circuit 1, so that a large isolation can be obtained.

(Embodiment 2) FIG. 2 is a configuration diagram of a high-frequency oscillator according to Embodiment 2 of the present invention. In FIG. 2, 9 is a switch. The same components as those in FIG. 1 are denoted by the same reference numerals.

A feature of the present invention resides in that, in addition to the inductor 5 and the capacitor 6, a ground is further connected in series via a switch 9.

It is desirable that the capacitor 6 has a large capacitance in order to reliably attenuate low-frequency low-frequency noise. However, when the capacitance of the capacitor 6 is very large, the rise time of the circuit may be extended. That is, it is necessary to charge the capacitor 6 with the current from the bias circuit 3 when the power is turned on. However, since the bias circuit is composed of a constant current source, the capacitor 6 can be charged in a short time.
Cannot be charged. Therefore, when the power is turned on, the switch 9
Turn off and start up fast. At this point, an operation that needs to be completed in a short time, such as a carrier sense operation, is performed. By turning on the switch 9 when there is carrier sense, the output signal quality of the high-frequency oscillator is improved, so that anti-jamming wave characteristics and the like are improved, and a stable receiving operation can be performed.

The on and off timings of the switches may be set arbitrarily according to the operating conditions of the radio.

The present embodiment is characterized in that the rise time of the circuit and the quality of the high-frequency output signal are compatible.

(Embodiment 3) FIG. 3 is a configuration diagram of a high-frequency oscillator according to Embodiment 3 of the present invention. In FIG. 3, reference numeral 11 denotes a switch terminal. The same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.

A feature of the present invention resides in that the switch 9 is built in the semiconductor integrated circuit 1. And inductor 5
And a capacitor 6 connected in series to a switch terminal 11 which is an external connection terminal of the semiconductor integrated circuit 1 and grounded through a switch 9 in the semiconductor integrated circuit.

As described above, since the switch is provided in the semiconductor integrated circuit, there is a feature that the number of external components does not increase. Further, since the switch is controlled in the semiconductor integrated circuit, wiring such as wiring is not required as compared with the case where the switch is provided outside, and the high-frequency oscillator can be made compact.

(Embodiment 4) FIG. 4 is a configuration diagram of a high-frequency oscillator according to Embodiment 4 of the present invention. In FIG. 4, 12 is a second capacitor, and 13 is an input terminal. The same components as those in FIGS. 1, 2 and 3 are denoted by the same reference numerals.

The feature of the present invention lies in that not only the rise time of the circuit and the quality of the high-frequency output signal are compatible, but also a terminal for noise attenuation is not required.

The second capacitor 12 and the switch 9 are connected in parallel to the input terminal 13 of the oscillation circuit 2, and the other ends of the second capacitor 12 and the switch 9 are connected to the resonator connection terminal 7.

Here, the capacitance of the second capacitor has a value that provides a sufficiently high impedance at the frequency of low-frequency noise of the bias circuit. However, the value is larger than the capacity of the DC cut capacitor inserted between the resonator 4 and the resonator connection terminal 7.

At the start of the circuit, the switch 9 is turned off. At this time, the bias voltage is divided by the capacitor 6 and the second capacitor 12, but most of the voltage is applied between the electrodes of the second capacitor.
The charging current to 2 is small. Therefore, charging can be completed in a short time. In this state, an operation that needs to be performed at a high speed, such as a carrier sense operation, is performed. Next, the signal quality of the oscillation output can be improved by turning on the switch 9, so that the receiving operation can be stably performed.

As described above, both the rise time of the circuit and the quality of the high-frequency output signal are compatible, and a terminal for noise attenuation is not required.

(Embodiment 5) FIG. 5 is a configuration diagram of a high-frequency oscillator according to Embodiment 5 of the present invention. In FIG. 5, reference numeral 14 denotes a resistor. The same components as those in FIG. 1 are denoted by the same reference numerals.

A feature of the present invention is that a resistor is used instead of an inductor. A similar effect can be obtained by using a resistor because of the difference in impedance between the high-frequency signal and the low-frequency signal. In other words, at a high frequency signal frequency, if the impedance is sufficiently large with respect to 50Ω, there is no influence such as attenuation. For example, for a 1 kΩ resistor, the loss is 0.3 dB. On the other hand, at the frequency of low-frequency noise, the signal can be attenuated with an impedance smaller than 10 kΩ. Therefore, for example, if the resistance is set to 1 kΩ, the attenuation of low-frequency noise can be obtained at about 20 dB with little attenuation of high-frequency signals.

As described above, the cost can be reduced by using the resistor instead of the inductor.

Further, since the resistor can be easily incorporated in the semiconductor integrated circuit, a configuration in which only a capacitor is externally provided is possible. Thus, the size and cost of the circuit can be reduced.

[0041]

As is apparent from the above description, according to the high-frequency oscillator of the present invention, since the grounding is performed through the series connection of the inductor and the capacitor, the low frequency of the bias circuit can be obtained without attenuating the oscillation frequency signal. There is an effect that the frequency noise component can be attenuated and a low-noise oscillation output signal can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a high-frequency oscillator according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a high-frequency oscillator according to a second embodiment of the present invention.

FIG. 3 is a circuit diagram of a high-frequency oscillator according to a third embodiment of the present invention.

FIG. 4 is a circuit diagram of a high-frequency oscillator according to a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram of a high-frequency oscillator according to a fifth embodiment of the present invention.

FIG. 6 is a circuit diagram of a conventional high-frequency oscillator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor integrated circuit 2 Oscillation circuit 3 Bias circuit 4 Resonator 5 Inductor 6 Capacitor 7 Resonator connection terminal 8 Oscillation output terminal 9 Switch 11 Switch terminal 12 Second capacitor 13 Input terminal 14 Resistance 15 Noise path terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J081 AA03 CC30 CC43 DD03 DD21 DD25 EE02 EE03 FF02 FF09 FF11 FF17 FF21 FF23 FF24 FF25 LL01 MM01

Claims (5)

[Claims] An oscillation circuit configured in the semiconductor integrated circuit; a bias circuit configured in the semiconductor integrated circuit to supply a bias voltage of a resonator connection terminal of the oscillation circuit; a resonator; an inductor; A capacitor is provided, the resonator connection terminal is connected to the resonator, and the resonator connection terminal is configured to be connected to a ground or a power supply through the inductor and the capacitor in series. A high-frequency oscillator whose constant is set such that the combined impedance is sufficiently low at the frequency of low-frequency noise included in the output of the bias circuit and sufficiently high at the oscillation frequency. 2. An oscillation circuit formed in a semiconductor integrated circuit, a bias circuit formed in the semiconductor integrated circuit and supplying a bias voltage of a resonator connection terminal of the oscillation circuit, a resonator, an inductor, Comprising a capacitor and a switch, connecting the resonator connection terminal and the resonator, wherein the resonator connection terminal is connected to a ground or a power supply through the inductor, the capacitor and the switch in series, A constant is set so that the combined impedance of the inductor and the capacitor is sufficiently low at the frequency of low-frequency noise included in the output of the bias circuit and sufficiently high at the oscillation frequency, and the switch is set according to the operation state. A high frequency oscillator that turns on or off. 3. The high-frequency oscillator according to claim 2, wherein the switch is formed in a semiconductor integrated circuit. 4. An oscillation circuit configured in the semiconductor integrated circuit, a bias circuit configured in the semiconductor integrated circuit for supplying a bias voltage of an input terminal of the oscillation circuit, and configured in the semiconductor integrated circuit. A first capacitor and a switch; a resonator; an inductor; and a second capacitor, wherein the input terminal is configured in the semiconductor integrated circuit via the first capacitor and the switch connected in parallel. Connected to the resonator connection terminal, the resonator connection terminal and the resonator are connected, and the resonator connection terminal is connected to a ground or a power supply through the inductor and the capacitor in series, An impedance in which the combined impedance of the inductor and the capacitor is sufficiently low at the frequency of low-frequency noise included in the output of the bias circuit. A high-frequency oscillator whose constant is set so that the impedance is sufficiently high at the oscillation frequency. 5. The high-frequency oscillator according to claim 1, wherein a resistor is used in place of the inductor.