JPH1065747A - Frequency modulated signal generator - Google Patents

Abstract

(57) [Problem] To provide a PLL frequency modulation (FSK) signal generation device that does not cause a data error on a receiving side. The invention relates to a frequency modulation (FSK) signal generator of PLL system, the control voltage of the voltage controlled oscillator when the transmission data is mark frequency f _Z is sampled and held, when the transmission data is space frequency f _A The control voltage sampled and held is changed by a predetermined amount and supplied to the voltage controlled oscillator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to frequency modulation (FS).
K: frequency shift keying)
More particularly, the present invention relates to a PLL frequency modulation (FSK) signal generator that does not cause a data error on the receiving side.

[0002]

2. Description of the Related Art Generally, frequency modulation (FSK: freq
On the transmitting side of a digital transmission system using the UHF (shift shift keying), a modulation signal generator for modulating transmission data is used. As the modulation signal generator, the oscillation frequency is modulated by shifting the oscillation frequency in an impulse manner. A frequency modulation (FSK) signal generating device is known. And PL in the conventional RF modem
As shown in FIG. 2, the L-type FSK signal generator includes a reference frequency generator 1, a 1 / M frequency divider 2 connected to the reference frequency generator 1, and a 1 / M frequency divider 2 , A low-pass filter (LPF) 4 connected to the phase comparator 3, a voltage-controlled oscillator (VCO) 5 connected to the low-pass filter 4, the voltage-controlled oscillator 5, It has a 1 / N divider 6 connected to the phase comparator 3 so that transmission data is supplied to the VCO 5 via a variable resistor 7 and a capacitance 8. The operation of the FSK signal generating device will be described. The frequency obtained by dividing the reference frequency from the reference frequency generator 1 by 1 / M is the same as the frequency obtained by dividing the FSK modulation output from the VCO 5 by 1 / N. 1 /
N and the values of N and M of the 1 / M frequency dividers 6 and 2 are set, and the outputs of the 1 / N frequency divider 6 and the 1 / M frequency divider 2 are compared in phase by the phase comparator 3 and VCO5 through LPF4
Control voltage. When the control voltage of the VCO 5 is changed in accordance with the transmission data, the frequency of the output of the VCO 5 changes and becomes the FSK modulation output. This FSK modulation output is transmitted on a transmission line or the like and received by the receiving side.

[0003]

However, the above-mentioned conventional FSK signal generator is of the PLL type, and the control voltage of the VCO 5 is the VCO 5, the 1 / N divider 6,
Since the control voltage is supplied by the loop of the phase comparison 3 and the LPF 4, even if a DC offset voltage is added to the control voltage, the control voltage returns to the original control voltage over time, and the control voltage is continuously reduced. I couldn't change it. Therefore when the transmission data is not changed from the start of transmission, that is, when either signal mark or space is continuously output, will be the center frequency F _o of is output after a predetermined time, or the mark on the receiving side There was a problem that a data error occurred because it was not possible to judge whether it was a space. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a frequency modulation (FSK) signal generation device of a PLL system that does not cause a data error on a receiving side.

[0004]

To achieve the above object, according to an aspect of the present invention, in the frequency modulation (FSK) signal generator of PLL system, the control voltage of the voltage controlled oscillator when the transmission data is mark frequency f _Z samples and holds, the transmission data is when the space frequency f _a, the sample hold control voltage by a predetermined amount change and supplying to the voltage controlled oscillator. Another feature of the present invention is a PLL type FSK signal generating device, which is means for sampling and holding a control voltage of a voltage controlled oscillator when transmission data is a space, and for sampling and holding when the transmission data is a mark. Means for changing the applied voltage by a predetermined amount and supplying the changed voltage to the voltage-controlled oscillator.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on illustrated embodiments. FIG. 1 is a block diagram of a frequency modulation (FSK) signal generator according to the present invention. As shown in FIG. 1, the FSK signal generator includes a reference frequency generator 1
A 1 / M frequency divider 2 connected to the reference frequency generator 1 and a phase comparator 3 connected to the 1 / M frequency divider 2
A low pass filter (LPF) 4 connected to the phase comparator 3, a sample hold (S / H) circuit 9 connected to the low pass filter 4, and an adder 10 connected to the sample hold circuit 9. And the adder 1
Switch 1 connected to a voltage source 12 of 0 and voltage _VA
1 and a voltage-controlled oscillator (V
CO) 5, the voltage-controlled oscillator 5 and the phase comparator 3
And a 1 / N frequency divider 6 connected to the sample and hold circuit 9 and the switch 11. The sample-and-hold circuit 9 becomes sampling state when the mark is transmission data, the space VCO5 outputs a signal of frequency F _Z when the control voltage V _Z, a signal of frequency F _A when the control voltage V _Z + V _A It is set to output.

Next, the operation of the FSK signal generator will be described. First, the case of transmitting the transmission data of f _Z (mark frequency) as the first state, the transmission data f _A
On the condition that the state of (space frequency) is not long-term continuous, the switch 11 is OFF state when the transmission data is f _Z (mark frequency), the sample hold circuit 9 is a sample state, the 1 / N frequency divider 6 The 1 / N frequency divider 6 and the 1 / N frequency divider 6 are used so that the 1 / N frequency obtained when _fZ (mark frequency) is input to the reference frequency and the 1 / M frequency obtained by dividing the reference frequency by the 1 / M frequency divider 2 become the same. N and M of 1 / M frequency divider 2
Set the value of Thereby, this 1 / N frequency divider 6
The output frequency of the 1 / M frequency divider 2 is compared with the output frequency of the 1 / M frequency divider 2, the output of which passes through the LPF 4, the sample hold circuit 9 and the adder 10, and becomes the control voltage of the VCO 5,
The frequency of the VCO 5 is controlled. Here, the VC
Frequency O5 is f _Z (mark frequency) high control voltage for lowering the frequency if more movement, f _Z (mark frequency) if lower than the result of the control voltage in the direction of increasing the frequency moves, the output frequency of the VCO5 Becomes _fZ (mark frequency).

[0007] Next, when the transmission data is f _A (space frequency), the sample hold circuit 9 when the transmission data becomes HOLD state holds the voltage V _Z when the mark (the mark frequency F _Z) at the same time, Switch 11 is O
The state becomes the N state. Then, the adder 10 calculates the voltage V _Z of the sample hold circuit 9 and the voltage V _A from the voltage source 12.
And this is used as the control voltage. This control voltage V _Z +
Since V _A is input to VCO 5, the output frequency of VCO 5 becomes F _A (space frequency). By configuring as above, even when the transmission data is such as not to change from the start of the transmission, the output frequency of the VCO5 becomes possible to output only f _Z (mark frequency) or f _A (space frequency), f _O (Center frequency) is not output, and the mark and space can be correctly determined on the receiving side. The present invention relates to a PLL type FSK signal generator, comprising: means for sampling and holding a control voltage of a voltage controlled oscillator when transmission data is a space; and means for storing the sampled and held voltage when the transmission data is a mark. Means for supplying the voltage-controlled oscillator with a constant change.

[0008]

According to the present invention, or as described, f _Z (mark frequency) transmit the data as a reference of frequency f _Z
The control voltage of the VCO at (mark frequency) is sampled and held, and when the transmission data is f _A (space frequency), the control voltage sampled and held is changed by a predetermined amount and applied to the VCO. , F _O (center frequency), and no data error occurs on the receiving side.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a frequency modulation (FSK) signal generator according to the present invention.

FIG. 2 is a configuration diagram of a conventional FSK signal generator.

[Explanation of symbols]

1: Reference frequency generator, 2: 1 / M
Frequency divider, 3 ... phase comparator, 4
... low-pass filter (LPF), 5 ... voltage-controlled oscillator (VCO), 6 ... 1 / N frequency divider, 7 ... variable resistor, 8 ... capacitance,
9: sample-and-hold circuit, 10: adder, 11: switch, 12 ...
Voltage source,

Claims (2)

[Claims] 1. An FSK signal generating apparatus of a PLL system, comprising: a means for sampling and holding a control voltage of a voltage controlled oscillator when transmission data is a mark; and a means for sampling and holding the voltage when the transmission data is a space. Means for changing the amount by a predetermined amount and supplying the voltage-controlled oscillator to the voltage-controlled oscillator. 2. A PLL FSK signal generating device, comprising: means for sampling and holding a control voltage of a voltage controlled oscillator when transmission data is a space; and converting the sampled and held voltage when the transmission data is a mark. Means for changing the amount by a predetermined amount and supplying the voltage-controlled oscillator to the voltage-controlled oscillator.