JPH02216940A - Modulator - Google Patents

Abstract

PURPOSE:To attain the digital amplitude modulation at a high speed by setting the final-stage transistor of a power amplifier to the conductive/nonconductive states in accordance with the digital modulation signal. CONSTITUTION:An integrated circuit contains an oscillation circuit 6 and a power amplifier circuit 7, and a piezoelectric element 2 like a surface acoustic element, etc., is connected to the circuit 6. Then the final-stage transistor 10 of the circuit 7 is set to the conductive/nonconductive states in accordance with the digital modulation input signal. Thus the modulation of amplitude is carried out. Thus the necessary output voltage is obtained via the circuit 7 and at the same time the amplitude is modulated. Thus it is not required to perform the oscillation of a large amplitude via the circuit 6. Then the modulation of amplitude is attained without stopping the oscillation, and the power consumption is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a digital amplitude modulator that can be used as a transmitter for weak radio equipment or low power radio equipment.

(Prior Art) Conventionally, in order to simplify the circuit in weak-power radio equipment or low-power radio equipment, an antenna is directly connected to the output of an oscillation circuit having a modulation function, and the modulator is used as a transmitter as it is. However, in such a configuration, it is necessary for the oscillation circuit to oscillate with a large amplitude in order to obtain output power. Therefore, a large amount of electric power is also applied to the piezoelectric element used as an oscillation source, and in the case of "j &evil", there is a problem that the piezoelectric element is destroyed. Furthermore, these modulators achieved digital amplitude modulation by oscillating when the digital modulation input signal was "1" and stopping the oscillation when the input signal was "1".However, the Q value of the piezoelectric element Since the oscillation is high, it takes time to start and stop oscillation, and there is a problem that high-speed modulation cannot be performed.

Furthermore, since most of the above-mentioned wireless devices are portable, it has been desired that the modulators be made smaller as well. Therefore, in recent years, piezoelectric element chips such as surface acoustic wave elements used as oscillation sources,
Modulators or transmitters in which an IC chip on which other circuits are integrated are mounted in the same package are being considered.

In this case, even if the route is somewhat complicated, it can be made extremely compact by integration, so that a single oscillation circuit modulation circuit and a power amplifier circuit can be provided independently. But 1
There was a problem in that power consumption was large due to the increase in the number of circuit elements.

(Problems to be Solved by the Invention) As described above, conventional modulators have the problem of applying large power to the surface acoustic wave element and the problem of not being able to perform high-speed modulation. Furthermore, a modulator using a piezoelectric element chip such as a surface acoustic wave element and an IC chip also has the problem of high power consumption.

The present invention attempts to solve these problems, and its purpose is to: 1) avoid applying large amounts of power to piezoelectric elements such as surface acoustic wave elements, perform high-speed modulation, and use them as transmitters with low power consumption; The present invention seeks to provide a digital amplitude modulator.

[Structure of the Invention] (Means for Solving the Problems) The present invention connects a piezoelectric element such as a surface acoustic wave element to the oscillation circuit of an integrated circuit having an oscillation circuit and a power amplifier circuit, and Amplitude modulation is performed by making the final stage transistor in the circuit conductive/non-conductive depending on the digital modulation input signal.

(Function) With the above configuration, the present invention obtains the necessary output power in the power amplifier section and performs amplitude modulation. Therefore, it is not necessary to perform large amplitude oscillation with one oscillation circuit. Amplitude modulation can be performed without stopping one oscillation. Furthermore, since the final stage transistor, which requires the largest current consumption in the circuit, is turned on only when necessary, power consumption is small.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

173rd! ! I is a circuit configuration diagram according to an embodiment of the present invention.

In FIG. 1, an integrated circuit 1 is comprised of an oscillation circuit 6 and a power amplifier 7 connected to its output via a coupling capacitor 8.

Furthermore, the power amplifier 7 supplies a bias voltage and current to a transistor 10 whose collector is connected to the output terminal 5, whose base is connected to the capacitor 8, and whose emitter is grounded via a resistor 11, and to the base of the transistor 10. The bias circuit 9 includes a bias circuit 9 and a bias circuit 9. This bias circuit 9 has a function of not supplying an output, that is, bias voltage/current, when the digital modulation signal inputted from the modulation input terminal 4 is "O", but supplies it when the digital modulation signal is "L". Note that power is supplied to the first oscillation circuit 6 and the power amplifier 7 from a power supply terminal (not shown).

Furthermore, a surface acoustic wave resonator 2 is connected to the oscillation circuit 6 of the integrated circuit 1 via a bonding wire 3. The integrated circuit 1 and the surface acoustic wave resonator 2 are mounted in the same envelope in the form of a chip (meaning that they are placed on the same substrate plane).

The above configuration forms a digital amplitude modulator that can be used as a transmitter. When using the circuit shown in Figure 1 as a transmitter, a loop antenna, etc. is connected to the power supply and output terminals via a matching circuit. 5 as a load. Also.

When the circuit shown in FIG. 1 is used as a digital amplitude modulator, a suitable load such as a resistor is connected between the power supply and the output terminal 5.

The operation will be explained below.

In FIG. 1, an oscillation circuit 6 oscillates at the resonant frequency of the surface acoustic wave resonator 2, and its output signal is input to a power amplifier 7. When the digital modulation signal input from the modulation input terminal 4 is "1", the bias voltage and current are supplied from the bias circuit 9 to the base of the transistor IO, so the transistor 10 operates as an amplification element.
Amplify the output signal of the oscillation circuit 6 input to the base,
It is output from the output terminal 5 connected to the collector. At this time.

A current flows through the collector of the transistor 10 from the power supply through the load, and this current is normally the largest current in the circuit in order to supply sufficient power to the load.

Next, when the digital modulation signal is "O", no bias voltage or current is supplied from the bias circuit 7, so the transistor 10 does not operate as an amplifying element, and no current flows through the collector.

The output signal of the oscillation circuit 6 is not amplified, and no signal is output from the output terminal 5.

As described above, according to this embodiment, digital amplitude modulation is realized by making the transistor 10 conductive/non-conductive in accordance with the digital modulation signal. Therefore, extremely high-speed modulation can be performed. This is because the transistor IO, through which the most current flows, is only conductive when necessary.

Current consumption can be reduced. Also, modulation and amplification are performed by power amplifier 7.

The oscillation circuit 6 can oscillate with an amplitude suitable for the surface acoustic wave resonator 2, and there is no need to stop oscillation.Furthermore, the chip of the integrated circuit 1 and the chip of the surface acoustic wave resonator 2 are placed in the same enclosure. Since it is mounted inside the container, it can be made extremely compact.

This invention is not limited to the above embodiments, but can be implemented with various modifications.

Next, another embodiment of the invention will be described with reference to FIG.

FIG. 2 is a circuit configuration diagram according to another embodiment of the present invention.

In this embodiment, a transistor 10 has a collector connected to the output terminal 5 through the collector-emitter of a transistor 15, a base directly connected to the output of the oscillation circuit, and an emitter connected to the ground through a resistor 11.

A power amplifier is configured by a bias circuit 14 that supplies a bias voltage and current to the base of the transistor 15. The bias circuit 14 is similar to the above embodiment,
It has a function of turning on/off the output according to the digital modulation signal input from the modulation input terminal 4. power supply,
The operation of this embodiment will now be described with respect to the zero-order load, which is the same as in the above embodiment.

First, when the digital modulation signal is "1".

A bias voltage and current are supplied to the base of the transistor 15, and the transistor 15 becomes conductive between its collector and emitter. A bias voltage and current are supplied from the oscillation circuit 6 to the base of the transistor 10, and an output signal from the oscillation circuit 6 is input. Therefore, the transistor 10 operates as an amplifying element, amplifies the output signal of the first oscillation circuit 6, and outputs it from the output terminal 5 via the collector-emitter of the transistor 15 which is in a conductive state.

When the digital modulation signal is “0”, bias circuit 1
Since the bias voltage and current are not supplied from 4, the transistor 15 becomes non-conductive, and no current flows to the collector of the transistor 10. Therefore, the output signal of the oscillation circuit 6 is not amplified, and the signal is output from the output terminal 5. Not done.

In the embodiment of FIG. 1, if the parasitic capacitance between the corephtal base of transistor 10 is large, transistor lO
Although there is a possibility that the output signal of the oscillation circuit 6 leaks to the output terminal 5 via the above-mentioned parasitic capacitance even when the transistor IO is non-conducting, in the embodiment shown in FIG. Since the transistor 15 is connected to the transistor 15, such leakage signals can be made extremely small. It is also suitable for integrated circuits because it eliminates the need for coupling capacitors.

Next, another embodiment of the present invention will be described with reference to FIG.

FIG. 3 is a circuit configuration diagram showing another embodiment of the present invention.

In this embodiment, a preamplifier is connected to the input section of the power amplifier of the embodiment of FIG.

If sufficient amplification cannot be obtained only by amplification by the transistor 10, such a configuration may be used.

Similarly, 4v4 is a circuit configuration diagram showing an embodiment in which a preamplifier is connected to the input section of the power amplifier shown in FIG.

In the above embodiments and modified examples, a one-port surface acoustic wave resonator is illustrated as a piezoelectric element used as one oscillation source, but the present invention is not limited to this, and a two-port surface acoustic wave resonator is used. 1 surface acoustic wave delay line, 1 surface acoustic wave filter, or a crystal oscillator may be used.

In all the embodiments and modifications, the resistor 11 can be omitted. Further, a capacitor for bypassing high frequency current may be connected in parallel with the resistor 11.

Further, although it is preferable that the chip of the integrated circuit 1 and the piezoelectric element chip such as the surface acoustic wave element 2 be mounted on the same outer hilt, it is of course possible to mount them on separate envelopes.

The embodiments and modifications of this invention have been described above, but
In short, the present invention can be modified and implemented in various ways without departing from the gist thereof.

〔Effect of the invention〕

As explained above, according to the present invention, digital amplitude modulation is realized by making the final stage transistor of the power amplifier conductive/non-conductive according to the digital modulation signal, and extremely high-speed modulation can be performed. Since the final stage transistor through which the most current flows in one circuit is turned on only when necessary, power consumption can be reduced.

In addition, since amplification and modulation to obtain the necessary output power are performed by a power amplifier, the first oscillation circuit can oscillate with an amplitude suitable for piezoelectric elements such as surface acoustic wave elements. There is no danger of destroying the piezoelectric element of the device, and furthermore, since the integrated circuit chip and the surface acoustic wave chip are mounted in the same envelope, it can be made extremely compact.

FIGS. 2 to 4 are circuit configuration diagrams showing other embodiments of the present invention.

1... Integrated circuit 2... Surface acoustic wave element 3
...Bonding wire 4...Modulation input terminal 5...Output terminal 6...
Oscillation circuit? , 13.16.18...Power amplifier 8...
・Coupling capacitor 9, I4...Bias circuit 10.15...Transistor 11...Resistor 17...Additional amplifier agent Patent attorney Noriyuki Chika Yudo Kikuo Takehana Figure 1, Figure 2 figure

Claims (1)

[Scope of Claims] An integrated circuit including at least an oscillation circuit and a power amplifier circuit, and a piezoelectric element electrically connected to the oscillation circuit of the integrated circuit, and a final stage transistor in the power amplifier circuit. A modulator that performs amplitude modulation by entering either a conductive state or a non-conductive state depending on a digitally modulated signal.