JPH07231337A - Device and method for generating fsk signal - Google Patents

Abstract

PURPOSE:To generate an FSK signal with less interference between channels with a simple configuration by providing a variable frequency division ratio counter for generating the FSK signal by frequency-dividing a reference signal based on transmitting data while being connected with the output terminal of a reference signal generating part. CONSTITUTION:The output terminal of a reference signal generating part 1 is connected with a variable frequency division ratio counter 2. The variable frequency division ratio counter 2 generates the FSK signal by dividing the reference signal into two different frequencies based on the transmitting data and its output terminal is connected with a first frequency conversion part 3. The first frequency conversion part 3 is composed of a first local oscillating part 3a and a first mixing part 3b, and the output terminal of the first mixing part 3b is connected with a first bandpass filter 4. The output terminal of the first band pass filter 4 is connected with a second frequency conversion part 5. The second frequency conversion part 5 is composed of a second local oscillator part 5a and a second mixer part 5b for synthesizing a local oscillator frequency signal and the FSK signal, the output terminal of the mixer part 5b is connected with a second bandpass filter 4, and the output terminal of the filter 4 is used as the output terminal of this device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FSK signal generating device and an FSK signal generating method in an FSK type RF modem transmitting and receiving using a coaxial cable.

[0002]

2. Description of the Related Art As an FSK signal generator in an FSK type RF modem that transmits and receives frequency signals of several MHz to several hundred MHz using a coaxial cable, it is necessary to use two crystal oscillation circuits having different frequencies. , A frequency signal is generated and the signal is output by switching it with a switch. Fig. 2 shows the conventional FSK
It is a block diagram which shows the structure of a signal generator. In the figure, the crystal oscillating circuits 7 and 8 generate the required frequency signals, and their output terminals are connected to the switch 9. The switch 9 switches the connection state according to the content of data to be transmitted and outputs the FSK signal from the common terminal side. For example, when outputting an FSK signal having a center frequency of f ₀ and a frequency deviation of ± Δf, the oscillation frequency of each crystal oscillation circuit is the oscillation frequency of the crystal oscillation circuit 7 being f ₀ + Δf, the oscillation frequency of the crystal oscillation circuit 8. Was set to f ₀ −Δf, and this was switched by the switch 9 to generate the FSK signal.

However, in the conventional FSK signal generator as described above, the frequency bandwidth of the output FSK signal changes depending on the frequency deviation and the communication speed, and the higher the communication speed, the wider the frequency bandwidth. There was a problem that it interfered with the adjacent channel.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an F that can obtain an FSK signal with a relatively simple structure and generate an FSK signal with less interference between channels.
It is an object of the present invention to provide an SK signal generating device and method.

[0005]

SUMMARY OF THE INVENTION To achieve this object, an FSK signal generator according to the present invention connects a reference signal generating section for generating a signal of a reference frequency and an output end of the reference signal generating section based on transmission data. And a variable frequency division ratio counter for frequency-dividing the reference signal to generate an FSK signal, and a first frequency conversion circuit connected to the output side of the variable frequency division ratio counter for converting the frequency of the FSK signal.
The frequency conversion unit includes a first local oscillation unit that generates a signal of a local oscillation frequency and a first mixing unit that synthesizes the local oscillation frequency signal and the FSK signal. The output end is connected to a first bandpass filter for removing unnecessary frequencies, the output end of the first bandpass filter is connected to a second frequency conversion unit, and the output end of the second frequency conversion unit is connected to the first frequency conversion unit. It is connected to a two-band pass filter, and the output end of the band pass filter is configured to be the output end of the FSK signal generator, and the reference signal generator generates a reference signal having a frequency lower than the target FSK signal, The variable division ratio counter divides the reference signal into two different frequencies based on the transmission data to generate an FSK signal, and the FSK signal is generated by the first frequency conversion unit at an intermediate frequency higher than that of the reference signal. It was converted to the frequencies of interest FSK
An unnecessary frequency band of the signal is removed by a first bandpass filter, the FSk signal is further converted into a final high transmission frequency by a second frequency conversion unit, and a frequency band other than a desired frequency band is obtained by a second bandpass filter. Is eliminated, the frequency band is stabilized and an FSK signal that does not interfere with other channels can be output.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the embodiments shown in the drawings. FIG. 1 is a block diagram showing a configuration of an FSK signal generator according to the present invention. In FIG. 1, a reference signal generator 1 is for generating a signal of a reference frequency. The output terminal is connected to the variable division ratio counter 2. The variable frequency division ratio counter 2 divides the reference signal into two different frequencies based on transmission data to generate an FSK signal, the output end of which is connected to the first frequency conversion unit 3. There is. The first frequency conversion unit 3 includes a first local oscillation unit 3a that generates a signal of a local oscillation frequency and a first mixing unit 3b that synthesizes the local oscillation frequency signal and the FSK signal. The output end is connected to the first bandpass filter 4. The first bandpass filter 4 limits and outputs the frequency band of the FSK signal, and its output end is connected to the second frequency converter 5. The second frequency converter 5 is for converting the FSK signal converted to the intermediate frequency to a final higher transmission frequency, and the second frequency converter 5 is a second local part for generating a signal of a local oscillation frequency. It comprises an oscillating section 5a and a second mixing section 5b for synthesizing the local oscillation frequency signal and the FSK signal, and the output end of the second mixing section 5b is connected to the second bandpass filter 4. The second bandpass filter removes frequencies other than the desired frequency band, and this output end is used as the output end of the FSK signal generator.

The FSK signal generator configured as described above operates as follows. That is, the reference signal generator 1 generates the reference signal f ₀ . The reference signal f ₀ is set to several tens of M so that the variable frequency division ratio counter 2 in the next stage can be configured by a digital IC.
The frequency is set to a comparatively low frequency of Hz or less and a frequency of several hundred times the communication speed in order to reduce code distortion. The variable frequency division ratio counter 2, which receives the reference signal f ₀ and the transmission data, divides the frequency division ratio of the reference signal f ₀ into 1 / n or 1 based on the data content of the transmission data.
/ M by changing the outputs of the FSK signal to frequency shift the difference between f ₀ · 1 / n and f ₀ · 1 / m. The variable frequency division ratio counter 2 can be constructed by an inexpensive digital IC by setting the reference signal f ₀ to the above-mentioned frequency. The first frequency converter 3 inputs the FSK signal,
This is converted to an intermediate frequency. Where f ₀ is several tens of MHz
If it is the following, the frequency of the FSK signal output from the variable frequency division ratio counter 2 is several MHz or less. The FSK
The signal is input to the first bandpass filter 4, and the first bandpass filter 4 performs the FSK by frequency conversion or the like.
Eliminate unnecessary frequencies mixed in the signal. The FSK signal that has passed through the first bandpass filter 4 is input to the second frequency converter 5. The second frequency converter 5 converts the input FSK signal into a final high transmission frequency and outputs it. The FSK signal is input to the second bandpass filter 6, and an unnecessary frequency of the FSK signal is removed to generate an FSK signal with a stable frequency band, and this is output as a final FSK signal.

[0008]

The present invention is constructed and operates as described above, so that the frequency band is stable irrespective of the communication speed and does not interfere with other channels.
It can output a signal. Further, by setting the reference signal to the low frequency as described above, the variable frequency division ratio counter can be configured by an inexpensive digital IC, so that the cost of the device can be kept low.

[0009]

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an FSK signal generator according to the present invention.

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

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reference signal generation part 2 ... Variable frequency division ratio counter 3 ... 1st frequency conversion part 3a ... 1st
Mixing part 3b ... 1st local oscillation part 4 ... 1st bandpass filter 5 ... 2nd frequency conversion part 5a ... 2nd
Mixing unit 5b ... Second local oscillation unit 6 ... Second bandpass filter 7,8 ... Crystal oscillator 9 ... Switch

Claims (2)

[Claims] 1. A reference signal generator for generating a signal of a reference frequency, and a variable frequency division ratio for connecting to an output end of the reference signal generator and dividing the reference signal based on transmission data to generate an FSK signal. A counter, a first frequency converter connected to an output terminal of the variable frequency division ratio counter for converting the FSK signal to an intermediate frequency, and the first frequency converter for generating a signal of a local oscillation frequency. Section and a first mixing section for synthesizing the local oscillation frequency signal and the FSK signal, the output terminal of the first mixing section being the output terminal of the first frequency converting section, and the output terminal of the first frequency converting section. A first bandpass filter for removing unnecessary frequencies of the FSK signal by connecting to the first bandpass filter,
The output end of the bandpass filter is connected to the second frequency conversion unit, and the second frequency conversion unit generates a signal of the local oscillation frequency, the second local oscillation unit, the local oscillation frequency signal and the F
A second mixing unit for synthesizing the SK signal, the output end of the second mixing unit is used as the output end of the second frequency conversion unit, and the output end of the second frequency conversion unit removes unnecessary frequencies. FSK signal generator configured to be connected to the bandpass filter of No. 1 and the output end of the second bandpass filter to be the output end of the FSK signal generator. 2. A reference signal generator generates a reference signal having a frequency lower than that of a target FSK signal, and a variable frequency division ratio counter divides the reference signal into two different frequencies based on transmission data. An FSK signal is generated, the FSK signal is converted into an intermediate frequency FSK signal by a first frequency conversion unit, and an unnecessary frequency band of the FSK signal is removed by a first bandpass filter.
An FSK signal generation method for generating a desired FSK signal by converting an SK signal to a final high transmission frequency by a second frequency conversion unit and removing an unnecessary frequency band by a second bandpass filter.