JPS6350204A - High frequency oscillator with modulating circuit - Google Patents

Abstract

PURPOSE:To equalize degrees of modulations even if the oscillation frequency is switched, by connecting a modulating capacity to a half-wave resonance line between first and second voltage nodal points which are generated on the half-wave resonance line when the frequency is oscillated in first and second frequency bands respectively and changing the value of the modulating capacity in accordance with the level of a signal. CONSTITUTION:An impedance ZR of a microstrip line 8 is 0OMEGA and an equivalent capacity C is infinite at a voltage nodal point (a) for resonance to center frequency 815MHz of the low frequency band and at a voltage nodal point (b) for resonance to center frequency 860MHz of the high frequency band. The impedance ZR is increased according as going away from voltage nodal points (a) and (b). A point (c) where the impedance in first center frequency 815MHz and that in a second center frequency 860MHz are equal to each other exists between voltage nodal points (a) and (b). The equivalent capacity in the first center frequency and that in the second center frequency are approximately equal to each other at the point (c). Consequently, the degree of modulation in the first and second center frequencies are equal to each other if a frequency modulating variable capacity diode 14 and a capacitor 13 are connected to the series connection body point (c).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-frequency oscillator equipped with a modulation circuit used in wireless communication devices and the like.

[Conventional technology]

One of the methods for performing mutual wireless communication is a method in which transmission and reception are performed at r7gJ using two frequencies called transmitters and receivers.

For example, transmitting on a first frequency in the 806-825 M[Iz m] band and receiving on a second frequency in the 851-870 M[Iz band. In addition, for such communication parties,
It receives at a frequency of 1 and transmits at a second frequency. For this reason, in a wireless communication device using such a communication system, an oscillator that generates a carrier wave for transmission is configured to be able to oscillate at either frequency in two frequency bands. Further, as a modulation method, a method of controlling a resonant element of an oscillator with a signal voltage to obtain a frequency-modulated oscillation frequency is preferably used because the circuit is simple and can be made compact. FIG. 2 shows an example of a conventional high frequency oscillator circuit equipped with a modulation circuit used in such a wireless communication device.

In FIG. 2, 1 is an oscillation transistor,
A feedback capacitor 2.3 is connected between the collector and emitter and between the emitter and ground. Further, a half-wavelength resonant circuit 5 is connected to the collector via a coupling capacitor 4.

The half-wavelength resonant circuit 5 includes a microstrip line 8 connected to the coupling capacitor 4 at one end and terminated at a termination capacitor 6, and terminated at the other end at a termination capacitor 7. At the other end, a series connection of a capacitor 9 and a switching diode 10 is further connected in parallel with the terminating capacitor.
A series connection body of a capacitor 11 and a variable capacitance diode 12 and a series connection body of a capacitor 13 and a variable capacitance diode 14 are provided.

The switching diode 10 is controlled to be conductive or non-conductive by a switching signal input from the switching terminal 15, and when it is conductive, the capacitor 9 is differentially connected to the termination capacitor 7, and the half-wave resonant circuit 5 is connected. The resonant frequency of the half-wavelength resonant circuit becomes low, and when non-conducting, the capacitor 9 is electrically disconnected and the resonant frequency of the half-wavelength resonant circuit becomes high.

The interelectrode capacitance of the variable capacitance diode 12 is controlled by a control voltage applied to the frequency control terminal 16, and the resonant frequency of the flower wavelength resonant circuit 5 is changed. That is, the resonant frequency can be changed largely by the switching signal and small by the control voltage.

The voltage of the low frequency signal input from the modulation terminal 17 is applied to the variable capacitance diode 4 after being divided by resistors 18 and 19, and the interelectrode capacitance changes depending on the level of the low frequency signal. As a result, the oscillation frequency of the oscillator is frequency modulated by the low frequency signal.

In the figure, 20 is a power supply terminal, 21 to 24 are bias resistors, 25 is a grounding capacitor, 26 and n are choke coils, 28 is a current limiting resistor, and 29 to 32 are bypass capacitors.

[Problem that the invention seeks to solve]

In the oscillation circuit shown in FIG. 1, a termination capacitor 7, capacitors 9, 11, 13, . and variable capacitance diode 1
2. Let the combined capacitance of 14 be C, and the variable capacitance diode 14
If the capacitance change is ΔC, the degree of modulation is expressed by J. Furthermore, the value of ΔC changes only depending on the level of the low frequency signal and is not influenced by the resonance frequency 1. However, the value of C can be changed due to the change of the resonant frequency, and in particular can be changed significantly by the switching signal. Therefore, in a range where the resonant frequency is low, the value of C is large, and therefore the degree of modulation is decreased, and conversely, in a range where the resonant frequency is high, the value of C is small, and therefore, the degree of modulation is increased.

[Means for solving problems]

In order to solve the above-mentioned problems, a high-frequency oscillator equipped with a modulation circuit according to the present invention consists of an oscillation active element and a half-wavelength resonant line with one end of the line grounded by a resonant capacitor, and the value of the resonant capacitor is set to 2. A high-frequency device comprising a modulation circuit that oscillates in one of the first frequency band and the second frequency band by changing the type of frequency band, and modulates the frequency of the oscillated oscillation frequency according to the signal level. In the oscillator l, a first voltage node is generated on the half-wave resonant line when oscillating in the first frequency band, and a second voltage node is generated on the half-wave resonant line when oscillating in the second frequency band. A modulating capacitor is connected to the half-wavelength resonant line between the voltage node and the modulating capacitor, and the value of the modulating capacitor is changed in accordance with the level of the signal, thereby frequency modulating the oscillation frequency.

[Effect]

Between each voltage node on the half-wavelength resonant line in the two types of missed frequency bands, there is a point where the equivalent capacitance is the same in the two types of oscillation frequency bands, and the modulation capacitance is connected to this point. By doing so, the same modulation degree can be obtained at two types of oscillation frequencies.

[Example] Fig. 1 is a circuit diagram of an example of a high frequency oscillator equipped with a modulation circuit according to the present invention, and the third figure is an explanatory diagram of the resonant state of the resonant circuit. The present invention will be described in detail with reference to FIG. In FIG. 1, circuit elements that are the same as those in FIG. 2 are given the same reference numerals and redundant explanations will be omitted.

The difference in FIG. 1 from the conventional example shown in FIG. 2 is that the connection point of the series connection of the variable capacitance diode 14 and the capacitor 13 that modulates the oscillation frequency is provided in the middle of the microstrip line 8.

The connection point is approximately midway between the two voltage nodes a and b shown in FIG.

Voltage nodes a and b are voltage nodes generated in the micros) IJ tube line 8 due to resonance between the resonant circuits, a is the voltage node when it resonates with the center frequency of the low frequency band 815 M) Iz, and b is the high frequency Band center frequency 860 MH
z This is the voltage node when resonance occurs. At these voltage nodes a and b, the impedance ZR of the microstrip line 8 is OΩ, and the equivalent capacitance C is infinite from C=1/wZR. The impedance ZR increases as it moves away from voltage nodes a and b, and the impedance ZR increases as it moves away from voltage nodes a and b.
There is a point C where the impedance at the first center frequency 815■Z is equal to the impedance at the second center frequency 86 (+?vlHz).At point C, the equivalent capacitance at the first center frequency and the is approximately equal to the equivalent 81 at the center frequency of 2.

That is, in the circuit shown in FIG. 1, capacitor 9 is the terminating capacitor v9.
At the end, the capacitor 71 is connected in parallel or electrically disconnected, and the voltage node changes to point a or point A in FIG. Alternatively, no difference appears in the equivalent capacitance due to separation.

Therefore, by connecting the series connection body of the frequency modulating variable capacitance diode 14 and the capacitor 13 to the point cl, the degree of modulation at the first and second center frequencies increases.

In addition, in the above explanation, for convenience, the equivalent capacitance at point C was assumed to be equal at the two center frequencies, but strictly speaking, the difference is only the ratio of the two center frequencies, and in fact, the point where the equivalent capacitance is equal has a slightly higher voltage than the zero point. It exists near the node.

〔Effect of the invention〕

By connecting a modulation capacitor to a point with equal equivalent capacitance that exists between two voltage nodes that occur on a half-wavelength resonant line in the oscillation frequency band of two glazes, the level of the modulation signal can be maintained even when the oscillation frequency is switched. The modulation depth can be made equal without switching.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a high frequency oscillator showing an embodiment of the present invention, FIG. 2 is a circuit diagram of a conventional high frequency oscillator, and FIG. 3 is an explanatory diagram of voltage distribution in a half-wavelength resonant line. 1... Transistor 7.9.11.13... Capacitor 8... Half wavelength resonant line 10... Switching diode 12.14... Variable capacitance diode 17... Modulation terminal Patent applicant Alps Electric Co., Ltd. Figure 1

Claims (1)

[Claims] It consists of an oscillating active element and a half-wavelength resonant line with one end of the line grounded by a resonant capacitor, and by changing the value of the resonant capacitor, one of the first frequency band and the second frequency band can be set. A first voltage generated in the half-wave resonant line when oscillating in the first frequency band, in a high-frequency oscillator equipped with a modulation circuit that oscillates at a frequency and modulates the oscillation frequency according to a signal level, A modulating capacitor is connected to the half-wavelength resonant line between the node and a second voltage node that is generated in the half-wavelength resonant line when oscillating in the second frequency band, and the value of the modulating capacitor is set to A high-frequency oscillator equipped with a modulation circuit, characterized in that the oscillation frequency is modulated by changing the oscillation frequency according to a signal level.