JP4483119B2 - High frequency oscillator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to a high frequency oscillator for a radio such as a cordless remote controller, a cordless telephone, and a mobile phone, and is a high frequency oscillator configured using a semiconductor integrated circuit in which an oscillation circuit is integrated on a semiconductor substrate. It relates to applications requiring N.
[0002]
[Prior art]
A conventional high-frequency transmitter will be described with reference to the drawings. FIG. 6 is a configuration diagram of a conventional high-frequency transmitter.
[0003]
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.
[0004]
An oscillation circuit 2 and a bias circuit 3 are built in the semiconductor integrated circuit 1. The input of the resonance circuit 2 is connected to a resonator connection terminal 7 that 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 gives a bias voltage.
[0005]
A resonator 4 configured outside the semiconductor is connected to the resonator connection terminal 7. The resonator 4 is a parallel resonator composed of 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]
[Problems to be solved by the invention]
However, the conventional high-frequency oscillator has a problem that the noise characteristics of the high-frequency output signal cannot be obtained sufficiently. Alternatively, it is necessary to provide the semiconductor integrated circuit 1 with the noise path terminal 14 for connecting the capacitor 6 for removing the noise of the bias circuit 3, which causes a cost increase.
[0007]
That is, the bias circuit 3 includes a constant current source circuit, a current mirror circuit, or the like, but the constant current circuit includes 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 capacitor is grounded from the bias circuit 3 through the noise path terminal 15 in an AC manner. This configuration requires a noise path terminal, and the number of terminals of the semiconductor integrated circuit 1 increases. Therefore, the cost has been increased due to the increase in the chip size of the semiconductor integrated circuit 1 and the increase in the number of pins of the package.
[0008]
[Means for Solving the Problems]
In order to solve the above-described conventional problems, a high-frequency oscillator according to the present invention includes an oscillation circuit configured in a semiconductor integrated circuit and a bias voltage of a resonator connection terminal of the oscillation circuit configured in the semiconductor integrated circuit. A bias circuit to be supplied, a resonator, an inductor, and a capacitor are provided, and the resonator connection terminal and the resonator are connected to each other. The resonator connection terminal is connected to the ground or a power supply through the inductor and the capacitor in series. The constant is set so that the combined impedance of the inductor and the capacitor is sufficiently low at the low frequency noise frequency included in the output of the bias circuit and sufficiently high at the oscillation frequency. It is what is done.
[0009]
And since it is grounded via a series connection of an inductor and a capacitor, 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 can be obtained. . Further, there is no increase in terminals such as noise path terminals.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
According to a first 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, A capacitor and a switch, the resonator connecting terminal and the resonator are connected, and the resonator connecting terminal is connected to a ground or a power source through the inductor, the capacitor and the switch in series, Constants are set so that the combined impedance of the inductor and the capacitor is sufficiently low at the low frequency noise frequency included in the output of the bias circuit and sufficiently high at the oscillation frequency. The switch is turned on or off. In addition, since the ground 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 in the off state can be shortened, and the noise characteristics of the oscillation output signal can be improved by turning it on thereafter.
[0012]
In the second invention, in particular, the switch according to the first aspect is configured in a semiconductor integrated circuit. And since the switch is provided in the semiconductor integrated circuit, there is no increase in external parts. In addition, since the switch is controlled in the semiconductor integrated circuit, wiring or the like is not required.
[0013]
According to a third 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 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, and the input terminal is connected in parallel to the semiconductor integrated circuit via the first capacitor and the switch. Connected to the configured resonator connection terminal, the resonator connection terminal and the resonator are connected, and the resonator connection terminal is connected to the ground or the power supply through the inductor and the second capacitor in series. a configuration, ten at the frequency of the low frequency noise combined impedance of the said inductor second capacitor is included in the output of the bias circuit In which the constant is set to be sufficiently high impedance at a low impedance oscillation frequency. In addition, it is possible to achieve both rising characteristics and noise characteristics with a configuration that does not require an external switch and does not increase the number of terminals.
[0014]
In the fourth invention , a resistor is used in place of the inductor in any one of the first to third inventions . And it can be made low-cost.
[0015]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0016]
Example 1
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.
[0017]
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.
[0018]
An oscillation circuit 2 and a bias circuit 3 are built in the semiconductor integrated circuit 1. The input of the resonance circuit 2 is connected to a resonator connection terminal 7 that 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 gives a bias voltage.
[0019]
A resonator 4 configured outside the semiconductor is connected to the resonator connection terminal 7. The resonator 4 is a parallel resonator composed of 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.
[0020]
The resonator connection terminal is grounded via the inductor 5 and the 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. As a result, a component of several hundred kHz or less, which is low frequency noise of the bias circuit, is attenuated. At this time, since the inductor has a large impedance at a transmission frequency of 400 MHz, the combined impedance becomes large, and the high frequency component is hardly attenuated.
[0021]
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 with a small noise component can be obtained.
[0022]
The configuration of this embodiment suppresses the influence of the low frequency noise component generated when the demodulator circuit, the logic circuit, etc. are built in the semiconductor integrated circuit 1 in addition to the low frequency noise generated from the bias circuit on the oscillator. It is also effective. Therefore, since a voltage is not excited in the wiring structure by the high frequency signal in the semiconductor integrated circuit 1, a large isolation can be obtained.
[0023]
(Example 2)
FIG. 2 is a configuration diagram of the high-frequency transmitter according to the second embodiment of the present invention. In FIG. 2, 9 is a switch. In addition, the same components as those in FIG.
[0024]
A feature of the present invention resides in that a ground is connected in series via a switch 9 in addition to the inductor 5 and the capacitor 6.
[0025]
It is desirable that the capacitor 6 has a large capacity in order to reliably attenuate low frequency low frequency noise. However, if 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, but the capacitor 6 cannot be charged in a short time because the bias circuit is composed of a constant current source. Therefore, when the power is turned on, the switch 9 is turned off to start up at high speed. At this point, an operation that needs to be completed in a short time, such as a carrier sense operation, is performed. If the switch 9 is turned on when there is carrier sense, the output signal quality of the high-frequency oscillator is improved, so that the anti-jamming wave characteristics and the like can be improved and a stable reception operation can be performed.
[0026]
Note that the on / off timing of the switch may be arbitrarily set according to the operating conditions of the radio.
[0027]
This embodiment is characterized in that both the circuit rise time and the quality of the high-frequency output signal can be achieved.
[0028]
(Example 3)
FIG. 3 is a configuration diagram of a high-frequency transmitter according to Embodiment 3 of the present invention. In FIG. 3, 11 is a switch terminal. The same components as those in FIGS. 1 and 2 are denoted by the same reference numerals.
[0029]
A feature of the present invention resides in that the switch 9 is built in the semiconductor integrated circuit 1. The inductor 5 and the capacitor 6 are connected in series from a switch terminal 11 which is an external connection terminal of the semiconductor integrated circuit 1 through a switch 9 in the semiconductor integrated circuit.
[0030]
As described above, since a switch is provided in the semiconductor integrated circuit, there is a feature that there is no increase in external parts. Further, since the switch is controlled in the semiconductor integrated circuit, it is not necessary to route wiring or the like as compared with the case where the switch is provided outside, and the high-frequency oscillator can be configured in a small size.
[0031]
Example 4
FIG. 4 is a configuration diagram of a high-frequency transmitter 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 given the same reference numerals.
[0032]
The feature of the present invention is that the rise time of the circuit and the quality of the high-frequency output signal are compatible, and a noise attenuation terminal is unnecessary.
[0033]
A second capacitor 12 and a 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.
[0034]
Here, the capacitance of the second capacitor is a value that provides a sufficiently high impedance at the low-frequency noise frequency 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.
[0035]
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 since most of the voltage is applied between the electrodes of the second capacitor, the charging current to the capacitor 12 is small. Therefore, charging can be completed in a short time. In this state, an operation that needs to be performed at high speed such as a carrier sense operation is performed. Next, since the signal quality of the oscillation output can be improved by turning on the switch 9, the reception operation can be performed stably.
[0036]
As described above, both the circuit rise time and the quality of the high-frequency output signal are compatible, and a noise attenuating terminal is unnecessary.
[0037]
(Example 5)
FIG. 5 is a configuration diagram of a high-frequency transmitter according to a fifth embodiment of the present invention. In FIG. 5, 14 is a resistor. Also, the same components as those in FIG.
[0038]
A feature of the present invention is that a resistor is used instead of an inductor. A similar effect can be obtained even if a resistor is used because of the difference in impedance between the high-frequency signal and the low-frequency signal. That is, at the high frequency signal frequency, if the impedance is sufficiently large with respect to 50Ω, there is no influence such as attenuation. For example, with a resistance of 1 kΩ, the loss is 0.3 dB. On the other hand, at a frequency of low frequency noise, a signal can be attenuated with an impedance smaller than 10 kΩ. Therefore, for example, if the resistance value is set to 1 kΩ, the attenuation of the low frequency noise can be obtained about 20 dB with almost no attenuation of the high frequency signal.
[0039]
Thus, the cost can be reduced by using a resistor instead of the inductor.
[0040]
In addition, since the resistor can be easily incorporated in the semiconductor integrated circuit, a configuration in which only the capacitor is externally attached is possible. As a result, the circuit can be reduced in size and cost.
[0041]
【The invention's effect】
As is clear from the above description, according to the high frequency oscillator of the present invention, since it is grounded via a series connection of an inductor and a capacitor, the low frequency noise component of the bias circuit is attenuated without attenuating the oscillation frequency signal. Therefore, there is an effect that 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. 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. Explanation】
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

Claims (4)

  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, a capacitor, and a switch; The resonator connection terminal and the resonator are connected, and the resonator connection terminal is connected to a ground or a power source through the inductor, the capacitor, and a switch in series, and the inductor and the capacitor The constant is set so 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, and the switch is turned on or off depending on the operating state. High frequency oscillator. 2. The high frequency oscillator according to claim 1 , wherein the switch is configured in a semiconductor integrated circuit. An oscillation circuit configured in a 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; a first capacitor configured in the semiconductor integrated circuit; A resonator, a resonator, an inductor, and a second capacitor, the input terminal being connected in parallel to the first capacitor and the resonator connecting terminal configured in the semiconductor integrated circuit via the switch The resonator connection terminal and the resonator are connected to each other, and the resonator connection terminal is connected to a ground or a power source through the inductor and the second capacitor in series, and It said second sufficiently low impedance at the frequency of the low frequency noise combined impedance of the capacitor is included in the output of the bias circuit Scan a and the high-frequency oscillator constant is set to be sufficiently high impedance at the oscillation frequency. 4. The high frequency oscillator according to claim 1 , wherein a resistor is used instead of the inductor.

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