JPH0897867A - Amplitude modulator - Google Patents

Abstract

PURPOSE: To obtain a monolithic IC-amplitude modulator where necessity for impressing large electric power on the piezoelectric oscillator of a surface acoustic wave resonator, etc., is not required, amplitude modulation is executed at high speed and a malfunction where a switch circuit part is being kept conductive in spite of a digital modulation input signal, what is called, signal omission does not occur. CONSTITUTION: An oscillation circuit part 1, the switch circuit part 4 and a power amplifier part 3 are formed inside the monolithic IC 10a of one chip. A system is constituted in such a way that the surface acoustic wave resonator 2 and an external power source 11 are connected to the oscillation circuit part 1, the power amplifier part 3 is connected to the oscillation circuit part 1 with the switch circuit part 1l and the external power source 11 and an external output terminal X1 are connected to the power amplifier part 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplitude modulator used for weak power or low power radio equipment for digital communication.

[0002]

2. Description of the Related Art Generally, weak or low power radio equipment is often portable, and therefore, it is desired that the amplitude modulator used in the radio equipment be small in size.
To meet such demands, an amplitude modulator has been studied in which an oscillating element such as a surface acoustic wave resonator used as an oscillating source and an IC in which other circuits are made into one chip monolithic are packaged in one. .

A conventional amplitude modulator will be described below with reference to the drawings.

FIG. 2 shows a block diagram of a conventional amplitude modulator 20. In the amplitude modulator 20, the oscillation circuit unit 1 and the switch circuit unit 4 are formed in the monolithic IC 20a of one chip, and the external power source 11 is connected to the oscillation circuit unit 1 via the switch circuit unit 4 so as to be external to the monolithic IC 20a. The arranged surface acoustic wave resonator 2 and the external output terminal X1 are connected to the oscillation circuit unit 1.

In the amplitude modulator 20 configured as described above, the switch circuit section 4 receives the digital modulation input signal as 1
The switch operates as a switch that conducts when, and becomes non-conductive when 0. The switch circuit unit 4 may be configured to be conductive when the digital modulation input signal is 0 and non-conductive when the digital modulation input signal is 1.

When the switch circuit section 4 is conducting,
Since power is supplied from the external power supply 11 to the oscillation circuit unit 1 and the surface acoustic wave resonator 2, the carrier wave is transmitted to the external output terminal X1.
When the switch circuit unit 4 is non-conducting, the external power source 11 causes the oscillator circuit unit 1 and the surface acoustic wave resonator 2 to
Is not supplied to the external output terminal X1
Do not output to. Digital amplitude modulation is performed by the above operation.

Here, in the conventional amplitude modulator 20, an antenna is directly connected to the external output terminal X1 for use. However, in such a configuration, it is necessary to oscillate a large amplitude in the oscillation circuit 1 in order to obtain a sufficient output. If a large amount of power is applied to the surface acoustic wave resonator 2 of the oscillation source in order to satisfy such requirements, there is a problem that the output signal is distorted or the surface acoustic wave resonator 2 is deteriorated or destroyed. Further, since the surface acoustic wave resonator 2 has a high Q value, it takes time to start / stop the oscillation of the surface acoustic wave resonator 2 depending on conduction / non-conduction between the external power source 11 and the oscillation circuit unit 1. There is also a problem that high-speed amplitude modulation cannot be performed.

FIG. 3 is a block diagram of another conventional amplitude modulator 30 proposed to solve the above-mentioned problems. The same or equivalent parts as those in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In FIG. 3, the oscillator circuit unit 1, the power amplifier unit 3, and the switch circuit unit 4 are formed in a monolithic IC 30a of one chip, and a surface acoustic wave resonator 2 and an external power source arranged outside the monolithic IC 30a. 11 is connected to the oscillation circuit unit 1, the power amplifier unit 3 is connected to the oscillation circuit unit 1, the external power source 11 is connected to the power amplifier unit 3, and the external output terminal X1 is connected via the switch circuit unit 4. It is connected to the power amplifier section 3.

In the thus constructed amplitude modulator 30, the carrier generated in the oscillation circuit section 1 and the surface acoustic wave resonator 2 is amplified in the power amplifier section 3 and then amplitude-modulated in the switch circuit section 4. And is output to the external output terminal X1.

At this time, since the carrier wave generated in the oscillation circuit section 1 and the surface acoustic wave resonator 2 is amplified by the power amplifier section 3, it is not necessary to oscillate a large amplitude in the oscillation circuit 1. Therefore, it is not necessary to apply a large electric power to the surface acoustic wave resonator 2 of the oscillation source, the output signal is not distorted, and the surface acoustic wave resonator 2 is not deteriorated or destroyed. Further, since the oscillation circuit unit 1 and the surface acoustic wave resonator 2 are constantly maintained in a state in which electric power is supplied from the external power source 11 to generate a carrier wave during amplitude modulation, the surface acoustic wave resonator 2 is oscillated. It does not take time to start / stop, and high-speed amplitude modulation can be maintained.

However, also in the amplitude modulator 30, since the input signal level from the power amplifier section 3 to the switch circuit section 4 is high, the switch circuit section 4 remains erroneous regardless of the digital modulation input signal. There was a problem that (light leakage) occurred.

[0013]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is not necessary to apply a large electric power to a piezoelectric oscillator such as a surface acoustic wave resonator.
It is another object of the present invention to provide a monolithic IC-type amplitude modulator that can perform high-speed amplitude modulation and does not cause the signal leakage.

[0014]

In order to achieve the above object, an amplitude modulator according to the present invention includes an oscillation circuit section, a power amplifier section, and a piezoelectric oscillator electrically connected to the oscillation circuit section. And a switch circuit section that is in a conducting state or a non-conducting state according to a digital modulation input signal is connected between the oscillation circuit section and the power amplifier section to perform amplitude modulation. It is characterized by doing.

Further, the oscillation circuit section, the power amplifier section, and the switch circuit section are formed in a monolithic IC of one chip.

[0016]

According to the amplitude modulator having the above construction, the carrier wave is amplified by the power amplifier section. Further, the oscillation circuit section and the surface acoustic wave resonator are always maintained in a state of generating a carrier wave during amplitude modulation. Further, since the switch circuit section is connected between the oscillation circuit section and the power amplifier section, malfunction (signal leakage) of the switch circuit section does not occur.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an amplitude modulator according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an amplitude modulator according to an embodiment of the present invention. The same or equivalent parts as those in FIGS. 2 and 3 are designated by the same reference numerals, and the description thereof will be omitted.

According to the present invention, as shown in FIG. 1, the oscillation circuit section 1, the switch circuit section 4, and the power amplifier section 3 are formed in a monolithic IC 10a of one chip, and a monolithic I
The surface acoustic wave resonator 2 and the external power source 11 arranged outside the C10a are connected to the oscillation circuit unit 1, and the power amplifier unit 3 is connected to the oscillation circuit unit 1 via the switch circuit unit 4,
The external power supply 11 and the external output terminal X1 are connected to the power amplifier section 3
Connected to.

In the thus constructed amplitude modulator 10, the carrier wave generated in the oscillation circuit section 1 and the surface acoustic wave resonator 2 is amplitude-modulated in the switch circuit section 4 and then amplified in the power amplifier section 3. Is output to the external output terminal X1.

At this time, the carrier wave generated in the oscillator circuit section 1 and the surface acoustic wave resonator 2 is connected to the switch circuit section 4 between the oscillator circuit section 1 and the power amplifier section 3, so that the power amplifier section. The amplitude is modulated by the switch circuit unit 4 before being amplified by 3. Therefore, the level of the input signal from the oscillation circuit unit 1 to the switch circuit unit 4 is small, so that the above-mentioned signal leakage does not occur. In addition, since the carrier wave generated in the oscillation circuit unit 1 and the surface acoustic wave resonator 2 is amplified by the power amplifier unit 3, it is not necessary to oscillate a large amplitude in the oscillation circuit unit 1. Therefore, since it is not necessary to apply a large electric power to the surface acoustic wave resonator 2 of the oscillation source, the output signal is not distorted, and the surface acoustic wave resonator 2 is not generated.
There is no deterioration or destruction of. Further, since the oscillation circuit unit 1 and the surface acoustic wave resonator 2 are constantly maintained in a state in which electric power is supplied from the external power source 11 to generate a carrier wave during amplitude modulation, the surface acoustic wave resonator 2 is oscillated. Start / stop does not take time, and high-speed amplitude modulation is always performed.

Although the surface acoustic wave resonator is used in the amplitude modulator of this embodiment, other piezoelectric resonators may be used instead.

Further, the switch circuit section of the amplitude modulator of this embodiment can be formed without any problem as long as it can be formed in the same process as the oscillation circuit section and the power amplifier section when forming a monolithic IC. , A diode or the like.

[0024]

As described above, according to the amplitude modulator of the present invention, a large amount of power is applied to a piezoelectric oscillator such as a surface acoustic wave resonator by amplifying a carrier wave in a power amplifier section. There is no need for it, there is no distortion in the output signal, and there is no deterioration or destruction of the surface acoustic wave resonator. Further, the oscillation circuit section and the surface acoustic wave resonator are
At the time of amplitude modulation, power is always supplied from the external power supply to maintain the state of generating a carrier wave, so it does not take time to start / stop the oscillation of the surface acoustic wave resonator.
High-speed amplitude modulation is always performed. Further, by connecting the switch circuit section between the oscillator circuit section and the power amplifier section, the carrier wave generated in the oscillator circuit section and the surface acoustic wave resonator is switched to the switch circuit section before being amplified by the power amplifier section. Amplitude is modulated by. Therefore, since the input signal level from the oscillation circuit section to the switch circuit section becomes small, the malfunction (signal leakage) in which the switch circuit section remains conductive regardless of the digital modulation input signal does not occur, and good characteristics can be obtained. The amplitude modulator can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an amplitude modulator of the present invention.

FIG. 2 is a configuration diagram of a conventional amplitude modulator.

FIG. 3 is a configuration diagram of another conventional amplitude modulator.

[Explanation of symbols]

 1 Oscillation Circuit Section 2 Surface Acoustic Wave Resonator 3 Power Amplifier Section 4 Switch Circuit Section 10 Amplitude Modulator 10a Monolithic IC 11 External Power Supply X1 External Output Terminal

Claims (2)

[Claims] 1. An oscillation circuit section, a power amplifier section, and a piezoelectric oscillator electrically connected to the oscillation circuit section,
Between the oscillation circuit unit and the power amplifier unit, a switch circuit unit that is in one of a conducting state and a non-conducting state according to a digital modulation input signal is connected to perform amplitude modulation. And an amplitude modulator. 2. The amplitude modulator according to claim 1, wherein the oscillation circuit section, the power amplifier section, and the switch circuit section are formed in a monolithic IC of one chip.