JPH063847B2 - Frequency modulator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention frequency-modulates a carrier wave with a binary data signal and a voice signal to respectively perform frequency shift keying signal (hereinafter, referred to as F
It is called SK signal. ) And a frequency modulation device capable of converting an audio signal into a frequency modulation signal.

[Prior Art] Conventionally, in the case where a carrier wave is directly frequency-modulated by a binary data signal and a voice signal and transmitted by a wireless line or a wired line, respectively, an FSK modulator and an analog frequency modulator (hereinafter referred to as a first conventional device). Called an example).

When both the binary data signal and the audio signal are transmitted as the FSK signal, the audio signal is analog-digital converted (hereinafter referred to as A / D conversion), and then the FSK signal is transmitted.
It is necessary to FSK-modulate the audio digital signal and the binary data signal using a modulator (hereinafter referred to as the second conventional example).

Further, when both the binary data signal and the voice signal are transmitted as analog frequency modulation signals, the binary data signal is converted into an analog signal within a voice band, and then a carrier wave is converted into an analog signal by using an analog frequency modulator. It is necessary to perform frequency modulation with an audio signal (hereinafter referred to as the third conventional example).

[Problems to be Solved by the Invention] Therefore, in the case where a carrier wave is frequency-modulated with a binary data signal and a voice signal and transmitted, as in the first conventional example, separate modulators are used, or Alternatively, as in the second and third conventional examples, an A / D conversion device or a conversion device for converting a binary data signal into an analog signal within the voice band is required, so that the circuit becomes complicated and the device becomes large. There was a problem that

An object of the present invention is to solve the above problems and to perform frequency modulation of a carrier wave with both a binary signal and a voice signal within a predetermined frequency band, and the circuit is simple as compared with the conventional example, and An object is to provide a frequency modulation device that can be downsized.

[Means for Solving Problems] A frequency modulation device according to the present invention includes a reactance modulation circuit that includes a variable capacitance diode and applies an input signal to the variable capacitance diode to perform frequency modulation. A first bias voltage when the reactance modulation circuit frequency-modulates within a predetermined frequency band when a value signal is applied to the variable capacitance diode, and the above when a predetermined audio signal is applied to the variable capacitance diode. A direct current power supply that generates a second bias voltage when the reactance modulation circuit frequency-modulates within a predetermined frequency band; and when the input signal is a binary signal, the first bias voltage causes the variable capacitance to change. The second signal is applied to the diode while the input signal is a voice signal.
Switching means for selectively switching the bias voltage to be applied to the variable capacitance diode.

[Operation] In the frequency modulation device configured as described above, the DC power supply is provided when the reactance modulation circuit performs frequency modulation within a predetermined frequency band when a predetermined binary signal is applied to the variable capacitance diode. A first bias voltage and a second bias voltage when the reactance modulation circuit frequency-modulates within a predetermined frequency band when a predetermined audio signal is applied to the variable capacitance diode are generated. The switching means applies the first bias voltage to the variable capacitance diode when the input signal is a binary signal, and the second bias voltage when the input signal is an audio signal. Is selectively switched so that the bias voltage is applied to the variable capacitance diode. Thereby, even if the input signal is a binary signal or a voice signal, the carrier wave can be frequency-modulated within a predetermined frequency band.

For example, the bias voltage of the variable capacitance diode of the reactance modulation circuit is the ground potential, + 2.5V, and + 5V.
, The modulation frequencies of the modulation circuit are f
It is assumed that they are 1, f0, and f2. For example, a binary data signal has an H level of + 5V and an L level of ground potential,
When the audio signal has a signal voltage of ± 2.5 V, the H level bias voltage is applied by the DC power supply when the carrier wave is modulated by the binary data signal, while the DC power supply is applied when the audio signal is modulated. Applies a bias voltage of + 2.5V.

At this time, by inputting the binary data signal,
The reactance modulation circuit can modulate the binary data signal to convert it into an FSK signal having frequencies f1 and f2. On the other hand, by inputting the audio signal, the reactance modulation circuit modulates the audio signal. It can be converted into an audio frequency modulation signal that changes between frequencies f1 and f2 with the frequency f0 as the center.
Therefore, both signals can be modulated within the frequency band between frequencies f1 and f2.

[Embodiment] FIG. 1 is a circuit diagram of an FSK signal and audio frequency modulator according to an embodiment of the present invention.

This modulator uses a reactance modulation circuit 4 using a variable capacitance diode D, and switches the bias voltage of the variable capacitance diode D in accordance with a binary data signal and an audio signal to be modulated to frequency modulate a carrier wave with each signal. It is characterized by that.

In FIG. 1, the FSK signal input terminal 1 is connected to the a side of the changeover switch 3, the audio signal input terminal 2 is connected to the b side of the changeover switch 3, and is connected to the ground via the resistor R1. The common side of the change-over switch 3 is connected to the cathode of the variable capacitance diode D of the reactance modulation circuit 4 via the choke coil L1, and is connected to the DC power source Vcc of + 5V, for example, via the resistor R2.
Connected to.

The anode of the diode D is connected to ground, and the cathode of the diode D is further connected to one end of the crystal oscillator X. The other end of the crystal oscillator X is connected to the base of an NPN transistor Q via a series circuit of a resistor R3 and a coil L2. A capacitor C1 is connected between the base and emitter of the transistor Q, and the emitter of the transistor Q is connected to the ground via a bias setting circuit of the transistor Q which is composed of a series circuit of a resistor R4 and a capacitor C2. A resistor R5 is connected between the base and collector of the transistor Q, and the base of the transistor Q is a resistor 6
In addition, it is connected to the ground via a series circuit of the resistor R7 and the thermistor TH. The circuit composed of the resistors R6 and R7 and the thermistor TH constitutes a temperature compensation circuit of the reactance modulation circuit.

The collector of the transistor Q is connected to the midpoint of the primary side of the output transformer TR, and both ends of the primary side of the transformer TR are connected in parallel with a parallel circuit of a resistor R8 and a capacitor C3. One end of the primary side of the transformer TR is connected to the ground via a high frequency bypass capacitor C4 and is also connected to a DC power source Vcc via a resistor R9. On the other hand, one end of the secondary side of the transformer TR is connected to the modulation signal output terminal 5, and the other end of the secondary side of the transformer TR is connected to the ground.

Therefore, in FIG. 1, the variable capacitance diode D,
The crystal oscillator X, the transistor Q, and their peripheral circuits are used to configure the reactance modulation circuit 4 that frequency-modulates the voltage applied across the variable-capacitance diode D and outputs the frequency-modulated signal to the output terminal 5. is doing.

In the modulator configured as described above, for example, +5
When modulating with a binary data signal having two values of V and ground potential and converting into a FSK signal, the selector switch 3 is switched to the a side. At this time, the bias of the variable capacitance diode D is set by the DC power supply Vcc connected through the resistor R2, and the potential of the cathode of the diode D becomes about + 5V. Then, when the binary data signal is input through the input terminal 1, the binary data signal is applied to both ends of the diode D through the side a of the changeover switch 3 and the choke coil L1. Signal voltage of (+5
The voltage across the diode D changes in accordance with V or the ground potential), which changes the capacitance of the diode D, and as a result, the modulation frequency f of the reactance modulation circuit 4 is as shown in FIG. Then, the frequency becomes f1 or f2. Therefore, the FSK signal having the frequency f1 or f2 that changes according to the signal voltage of the input binary data signal is output to the output terminal 5.

On the other hand, when frequency modulation is performed with the audio signal, the changeover switch 3 is changed over to the b side. At this time, the bias of the variable-capacitance diode D is such that the voltage of the DC power supply Vcc is
For example, the bias voltage divided by 2 is set to + 2.5V. Then, when the audio signal is input through the input terminal 2, the audio signal is applied to both ends of the diode D through the b side of the changeover switch 3 and the choke coil L1, and the voltage across the diode is equal to the above. A bias voltage of 2.5 V is centered and changes according to the signal voltage of the audio signal, which changes the capacitance of the diode D. As a result, for example, when the audio signal changes by ± 2.5 V, The modulation frequency f of the reactance modulation circuit 4 is the second
As shown in the figure, it changes between frequencies f1 and f2 around the frequency f0. Therefore, the frequencies f1 and f are centered around the frequency f0 according to the signal voltage of the input audio signal.
The audio frequency modulation signal that changes between 2 is output to the output terminal 5.

As described above, in the case of modulating with the binary data signal and converting into the FSK signal, the bias voltage of the diode D is set to, for example, + 5V, while in the case of frequency modulating with the audio signal, the voltage of the DC power supply Vcc is resistor R1. And R2 to divide the bias voltage of the diode D to + 2.5V, for example.
Setting each signal to a frequency f1
Alternatively, it can be converted into an FSK signal having f2 and an audio frequency modulation signal centered on the frequency f0 and varying between the frequencies f1 and f2. That is, by changing the bias voltage of the diode D as described above, the modulation frequency of the audio frequency modulation signal is included in the range of the modulation frequency of the FSK signal, so that both signals are efficiently transmitted in a predetermined transmission band. Can be transmitted to.

As described in detail above, there are advantages that the FSK signal and audio frequency modulator can be configured with a simple circuit as compared with the conventional example, and can be downsized as compared with the conventional example.

Other Embodiments FIG. 3 is a circuit diagram showing a modification of the FSK signal and voice frequency modulator.

In FIG. 3, a DC power supply Vcc is connected to a constant voltage integrated circuit 6, and a voltage output terminal of the circuit 6 is connected to an input end of a reactance modulation circuit 4 via a resistor R2 and a choke coil L1 and a voltage variable. It is connected to the ground via a resistance R0. The two predetermined connection points of the resistor R0 are connected to the a side and the b side of the changeover switch 7, which is changed over in conjunction with the changeover switch 3. The common side of the switch 7 is connected to the voltage adjusting terminal of the constant voltage integrated circuit 6.

With the above-described configuration, the bias voltage applied to the variable capacitance diode D of the reactance modulation circuit 4 is supplied from the constant voltage integrated circuit 6 that switches and outputs the predetermined voltage in conjunction with the changeover switch 3. You can

In the above embodiments, the bias voltage of the variable capacitance diode D is set as described above for each of the above signals, but the present invention is not limited to this, and the bias voltage is within the operating range of the diode D and The modulation frequency of each signal may be arbitrarily set so as to be included in a predetermined transmission band.

[Effects of the Invention] As described in detail above, according to the present invention, a reactance modulation circuit that includes a variable capacitance diode, applies an input signal to the variable capacitance diode to perform frequency modulation, and a predetermined binary signal. Is applied to the variable capacitance diode, the first bias voltage when the reactance modulation circuit performs frequency modulation within a predetermined frequency band, and the reactance modulation when a predetermined audio signal is applied to the variable capacitance diode. A direct current power supply for generating a second bias voltage when the circuit frequency-modulates within a predetermined frequency band; and the first when the input signal is a binary signal.
The bias voltage is applied to the variable capacitance diode while the input signal is an audio signal, the second bias voltage is selectively applied to the variable capacitance diode. Prepare

Therefore, the carrier wave can be frequency-modulated within a predetermined frequency band by both the binary signal and the audio signal, and
It is possible to provide a frequency modulator which has a simpler circuit and can be downsized as compared with the conventional example.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of an FSK signal and audio signal frequency modulator which is an embodiment of the present invention, and FIG. 2 is a voltage and modulation of a variable capacitance diode of a reactance modulator circuit of FIG. FIG. 3 is a circuit diagram showing a modification of the FSK signal and audio signal frequency modulator, showing a relationship with frequency. 1 ... Binary data signal input terminal, 2 ... Audio signal input terminal, 3 ... Changeover switch, 4 ... Reactance modulation circuit, 5 ... Signal output terminal, R1, R2 ... Resistor, Vcc ... DC power supply, D ... Variable capacitance diode.

Claims (1)

[Claims] 1. A reactance modulation circuit comprising a variable capacitance diode, for applying an input signal to the variable capacitance diode to perform frequency modulation, and the reactance when a predetermined binary signal is applied to the variable capacitance diode. A first bias voltage when the modulation circuit frequency-modulates within a predetermined frequency band, and a case where the reactance modulation circuit frequency-modulates within a predetermined frequency band when a predetermined audio signal is applied to the variable capacitance diode. And a DC power source for generating a second bias voltage of the variable bias diode, and the first bias voltage is applied to the variable capacitance diode when the input signal is a binary signal, while the input signal is a voice signal. When it is a signal, the second
And a switching means for selectively switching so that the bias voltage is applied to the variable capacitance diode.