JPH0220943A - Angle modulating circuit - Google Patents

Abstract

PURPOSE:To obtain an exact oscillation frequency of a voltage control oscillator by executing an input means, a waveform shaping means and a modulating means by a digital signal processing. CONSTITUTION:An output from a discriminating circuit 2 is supplied to a ROM filter 3 for bringing a square wave of a mark space of FSK to waveform shaping, output data from the ROM filter 3 is applied to a voltage control oscillator 4 of a digital processing format, and an output from the voltage control oscillator 4 of the digital signal processing format is supplied to a digital/analog(D/A) converter 5 and converted to an analog signal. In this case, the voltage control oscillator 4 is constituted so that the output data from the ROM filter 3, output data from a register 42 and an output from a setting device 44 are added by an adder 41. In such a way, said signal is set so that power of a desired frequency becomes maximum, and extracted as an FSK wave through a band pass filter 7 of an analog system. In such a way, an exact characteristic being near an ideal can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an angle modulation circuit suitable for limiting an occupied band.
More specifically, the present invention relates to a digital processing type angle modulation circuit.

(Prior art) For example, a conventional FSK modulation circuit supplies an FSK mark-space signal to a low-pass filter, attenuates unnecessary frequencies as a desired bandwidth, and applies the output of the low-pass filter as a limiting voltage to a voltage-controlled oscillator. , the output of a voltage controlled oscillator was modulated to obtain an FSK wave.

In addition, in amateur radio, etc., audio frequencies are keyed using FSK mark/space signals to generate audio frequency keying signals (AFSK signals).
There is also a configuration in which the AFSK signal is converted to a balanced modulator via a low-pass filter, a signal with a frequency of 5C is modulated by the AFSK signal, and an FSK wave is obtained via an SSB filter.

(Problem to be Solved by the Invention) However, in the former case of the above-mentioned conventional example, it is an analog system, and due to variations in elements, it is not possible to create a low-pass filter with accurate and identical characteristics. There was a problem that the oscillation frequency of the voltage controlled oscillator lacked accuracy.

In addition, when using the latter of the above conventional examples, there is a problem that two oscillators are required to generate the AFSK signal, and there is also a problem of noise countermeasures against noise generated by switching between the two oscillators. There is a problem that a balanced modulator for modulating the signal, an SSB filter, etc. are required. For this reason, there were problems in that the number of parts increased and the FSH waves were not of good quality.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a digital processing type angle modulation circuit with a narrow band and good stability.

(Means for Solving the Problems) In order to solve the above problems, the present invention is constructed as follows.

an input means for sampling and importing input binary information, and an input 2
A waveform shaping means of a digital signal processing method for obtaining an output corresponding to a response output when value information is passed through a low-pass filter, a modulation means of a digital signal processing method modulated by the output of the waveform shaping means, and a modulation means. digital/analog converting means for converting the output of the converter into an analog signal.

(effect) Input binary information is sampled by the input means.

Therefore, the high potential portion of the input binary information is sampled as the output from the input means. The waveform shaping means obtains an output from the input means corresponding to a response output when the input binary information is passed through the low-pass filter. Further, the waveform shaping means is performed using a digital signal processing method. In the output from the waveform shaping means, the high potential portion of the input binary information is sampled, and the envelope line is the same as when it is passed through a low-pass filter.

The output of the waveform shaping means is supplied to the modulation means and modulated,
converted to an analog signal.

However, since the waveform shaping means is performed by a digital signal processing method, the characteristics of the shoulder in the envelope line of the waveform shaping output are calculated digitally, so the characteristics may be more accurate than when realized by analog circuits. can do.

(Example) The present invention will be explained below using examples.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FSK mark (“1”) ・Space (“0”) information is output from the signal generator 8 at the sampling frequency 5
．． Accordingly, the sampling circuit 1 performs sampling. A discriminator 2 determines whether the FSK mark/space information sampled by the sampling circuit 1 has a high potential or a low potential. 3 is a ROM filter that stores digital values such that the step response becomes a Gaussian characteristic response by obtaining the rising and falling information of the FSK mark information, and shapes the square wave of the FSH mark space. be. Output from discrimination circuit 2 is ROM
The filter 3 is supplied with output data that has a Gaussian characteristic response at the rising and falling parts of the FSK mark information, and output data that has a constant response between the rising and falling parts in synchronization with the sampling of the sampling circuit 1. The readout output data from the ROM filter 3 is applied to the digital signal processing type voltage controlled oscillator 4, and the output from the digital signal processing type voltage controlled oscillator 4 is converted into digital/analog (D/A). 5 and converts it into an analog signal. Here, the voltage controlled oscillator 4 includes an adder 42, a register 4□ that delays the output of the adder 41, an adder 4. The output of is input as phase information,
It also includes a ROM 43 for sine wave conversion in which data corresponding to a sine wave is stored, and a setter 44 for setting the free-running frequency, and output data from the 120M filter 3, output data from the register 4□, and settings. The adder 41 is configured to add the outputs from the ROM 44.
Sine wave data discretized according to the output data from the filter 3 is output from the voltage controlled oscillator 4.

The analog signal output from the D/A converter 5 is cut into a predetermined pulse width by an analog switch 6, set so that the power of a desired frequency is maximized, and extracted as a PSK wave via a bandpass filter 7. . The bandpass filter 7 is an analog type filter.

In one embodiment of the present invention described above, the FSK mark
The space information is as shown in FIG. 2(A), and is sampled by the sampling circuit 1 at a sampling frequency 58. Therefore, the output of the sampling circuit 1 is as shown in FIG. 2(B). The output from the sampling circuit 1 shown in FIG. 2(B) is supplied to a discrimination circuit 2, which discriminates whether the output from the sampling circuit 1 is at a high potential or a low potential.

The output from the discrimination circuit 2 is supplied to the ROM filter 3,
The ROM filter 3 obtains information about the rising edge of the FSK mark information by starting the supply of the output from the discrimination circuit 2, and obtains information about the falling edge of the FSX mark information by once the supply of the output from the discrimination circuit 2 is terminated. Output data in which the step response approaches IF I F+ sequentially from tt OIt is read out from the discrimination circuit 2, that is, at each sampling, and thereafter, the output data of IT I 11 is read out for each discrimination output from the discrimination circuit 2. Data is read out, and output data whose step response sequentially reaches IT O11 from ff I IF due to falling information is read out every sampling. Therefore, the output data from the ROM filter 3 is schematically shown in FIG. 2(C). Here, the a-b section is 910 Ff ~ It I IF
The interval in which the output data of is read, b - c is 1'
The section in which the output data of IIt is read and the section following C is a section in which data is read out with addressing in the opposite direction to the section a-b.

On the other hand, the voltage controlled oscillator 4 uses the data from the adder 41 input to the ROM 4:l as phase information, and the data stored in the ROM 43 is output. Therefore, the voltage controlled oscillator 4
cooperates with the D/A converter 5 so that the input data is input to the IF O1.
When it is 1, the oscillation output of the FSK space frequency is
When the input data is t I IT, the oscillation output of the mark frequency is output, and when the input data is between tt Ort and Ff I IT, the oscillation output is output between the frequency of the space corresponding to the data read from the ROM filter 3 and the frequency of the mark. Generates a frequency output.

Both ends of the above-mentioned frequency output from the D/A converter 5 are cut off by an analog switch 6 so that the power of the desired frequency is maximized, and unnecessary frequency components are removed through a bandpass filter 7. removed and output.

In addition, although the case of the FSK modulator which obtains a PSK wave using the voltage controlled oscillator 4 was illustrated above, if a phase modulator is used instead of the voltage controlled oscillator 4, a band-limited PSK wave can be obtained.

(Effects of the Invention) As explained above, according to the present invention, the main parts, that is, the input means, the waveform shaping means, and the modulation means can be performed by digital signal processing, so they can be configured with a microprocessor or a dedicated integrated circuit, and are small. and high performance.

In addition, the waveform shaping means converts the input binary information into equivalent low-pass filter characteristics such as Gaussian characteristics, and since these characteristics are obtained by digital signal processing, data calculated by a computer can be used, and analog circuits It is possible to achieve more accurate characteristics that are closer to the ideal than when realized using

In addition, since the equivalent low-pass filter characteristics described above can be made into ideal characteristics, the output PSK wave,
The occupied bandwidth of the waves can also be limited to a targeted bandwidth.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 2 is a waveform diagram for explaining the operation of one embodiment of the present invention. 1... Sampling circuit, 2... Discrimination circuit, 3...
ROM filter, 4... Digital signal processing type voltage controlled oscillator, 5... D/A converter, 6... Analog switch, 7... Band pass filter, 8...
signal generator.

Claims (3)

[Claims] (1) an input means for sampling and capturing input binary information;
a digital signal processing waveform shaping means for obtaining an output corresponding to a response output when input binary information is passed through a low-pass filter; a digital signal processing modulation means modulating the output of the waveform shaping means; An angle modulation circuit comprising: digital/analog conversion means for converting the output of the modulation means into an analog signal. (2) The angle modulation circuit according to claim 1, wherein the modulation means is a voltage controlled oscillation means. (3) The angle modulation circuit according to claim 1, wherein the modulation means is a phase modulation means.