JPH02223256A - Single frequency generating circuit - Google Patents

Abstract

PURPOSE:To transmit sub information of single frequency without using a narrow-band filter and also, without affecting on the transmission of main data by eliminating a component exceeding a prescribed frequency included in a control signal from a control signal generating means. CONSTITUTION:A single frequency generating circuit is provided with a control signal generator 1, a low-pass filter 2 to filter the control signal (a) from the control signal generator 1, a single sine wave oscillator 3 to output a single sine wave (g), and a multiplier 5 to input the sine wave (g) from the single sine wave oscillator 3 and the control signal (b) passing the low-pass filter 2 and outputs an output signal (c) to an output terminal 4 after multiplying those wave and signal. The signal (c) is outputted as the sine wave having the same frequency as that of the sine wave (g) from the single sine wave oscillator 3. Therefore, since a high frequency component by a leading edge part (h) held by the control signal (a) can be eliminated, no influence of the signal (c) is given on a main data signal. Thereby, it is possible to obtain a single frequency generation circuit to transmit the sub information without giving adverse influence on main data transmission.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a single frequency generation circuit for a modulation/demodulation device.

[Conventional technology]

Generally, sub information is transmitted simultaneously with a main data signal in a modulator/demodulator.

As one method for transmitting sub-information of a modem,
There is a method that uses a single frequency generation circuit that sends sub information depending on the presence or absence of a single frequency.

Conventionally, a single frequency generation circuit has 1. as shown in FIG.
Series control signal generator 20. It consisted of a single sine wave oscillator 21 and a narrow band filter 22.

The control signal generator 20 generates an ON/OFF control signal d and outputs it to the single sine wave oscillator 21, as shown in FIG. 7(a).

The single sine wave oscillator 21 generates a single sine wave e shown in FIG. 7(b) and outputs it to the narrow band filter 22.

The narrow band filter 22 is for removing high frequency components of the sine wave e from the single sine wave oscillator 21. The reason for providing the narrowband filter 22 is as follows. When the control signal d changes from OFF to ON or from ON to OFF, the rising or falling portion of the single sine wave e becomes like W in FIG. 7(b) and contains high frequency components. This high frequency component affects the main data signal. This is because it is necessary to remove high frequency components using the narrowband filter 22.

[Problems to be Solved by the Invention] The conventional single frequency generation circuit described above has the following drawbacks because it has a configuration in which the high frequency component of the sine wave e is removed by the narrow band filter 22.

If the narrowband filter 22 with steep characteristics is to be realized by digital signal processing, the poles of the transfer function of this filter 22 must be brought close to the unit circle on the Z plane. As a result, an unstable state called a so-called limit cycle may occur, which may adversely affect the main data signal. Furthermore, since the order becomes high, the S/N ratio deteriorates and the calculation process becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a single frequency generation circuit that transmits sub-information without adversely affecting main data transmission.

[Means to solve the problem]

The present invention provides a single frequency generation circuit that transmits sub information together with a main data signal by turning on and off a single frequency, comprising: a control signal generating means for generating an on/off control signal; and a control signal generating means for generating an on/off control signal; a removing means for removing components of a predetermined frequency or higher included in a control signal from the generating means; a generating means for generating a sine wave signal of a single frequency; and a control signal from the removing means and a sine wave signal from the generating means. Multiply the wave signal and
It is characterized by comprising a multiplication means for transmitting sub-information using an output signal generated by this multiplication.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a single frequency generation circuit according to an embodiment of the present invention.

The single frequency generation circuit includes a control signal generator 1, a low-pass filter 2 that filters the control signal a from the control signal generator 1, and a single sine wave oscillator 3 that outputs a single sine wave g. and a multiplier 5 which inputs the sine wave g from the single sine wave oscillator 3 and the control signal S passed through the low-pass filter 2, multiplies them, and outputs an output signal C to the output terminal 4. We are prepared.

The control signal generator 1 is for generating an ON/OFF control signal a. The control signal a generated by this control signal generator 1 is as shown in FIG. 2(a).
This is a signal that has a rectangular waveform when the horizontal axis is the time axis and the vertical axis is the amplitude.

That is, it is a rectangular wave with a sharp rise at 08 o'clock and a high frequency component.

The low-pass filter 2 is a filter with a cutoff frequency fc. Therefore, the spectrum of pass frequencies of the low-pass filter 2 is from DC to fc. That is, single sine wave oscillator 3
Let f be the single sine wave oscillation frequency from , then the spectrum of the low-pass filter 2 is limited from f, -fe to f, +fc. Also, the main data transmission frequency band is f,
~f2, the cutoff frequency fc is set to satisfy rx fiefs fc as shown in FIG.

The single sine wave oscillator 3 outputs a single sine wave g to the multiplier 5. Although the sine wave g is not shown, the control signal a
It is a sine wave of a single frequency f3 having an amplitude of , and an amplitude of -.

The multiplier 5 inputs the control signal from the low-pass filter 2 and the sine wave g from the single sine wave oscillator 3, and multiplies these control signals and the sine wave g to produce a signal C ( 2(C)) is outputted to the output terminal 4.

Next, the operation exhibited by the single frequency generation circuit of this embodiment will be explained.

The control signal generator 1 outputs a rectangular wave control signal a having high frequency components. This control signal a is fs
fz>fs Cutoff frequency f set to fc
The control signal is passed through a low-pass filter 2 having an angle of c, and is output from the low-pass filter 2 as a control signal with a blunted rising edge.

On the other hand, the single sine wave oscillator 3 outputs a sine wave g of a single frequency r3 having an amplitude equal to that of the control signal a and an amplitude equal to that of the control signal a.

Control signal from low pass filter 2 and single sine wave oscillator 3
The sine wave g from is input to the multiplier 5 and is multiplied by the multiplier 5. The multiplier 5 outputs a signal C obtained as a result of the multiplication toward the output terminal 4.

The signal C has the same frequency f as the sine wave g from the single sine wave oscillator 3, as shown in FIG. 2(c).

It is output as a sine wave with . Therefore, since the high frequency component due to the rising edge of the control signal a has been removed, this signal C does not affect the main data signal.

FIG. 3 is a block diagram showing another embodiment of the invention. As mentioned earlier, the single frequency generation circuit of this embodiment transmits sub information with or without a single frequency (switching) at the same time as the main data signal during digital signal processing in a modulation/demodulation device. . This single frequency generation circuit includes a sine wave oscillator 1 that generates a sine wave i.
1, a control signal generator 12 that generates an on/off control signal j, a counter 13 that performs a counting operation for a certain period of time in synchronization with the rise and fall of the control signal j, and from the counter 13. an address generator 14 which takes the count value of , and outputs an address; an 80M section 15, which takes the address from the address generator 14 as an address input, and outputs an amplitude value corresponding to each address; The multiplier 16 multiplies the amplitude value of the sine wave i by the sine wave i from the sine wave oscillator 11.

Next, the operation of a single frequency generation circuit with this configuration is as follows.
This will be explained with reference to FIG. 4, which shows the time characteristics.

The control signal j output from the control signal generator 12 changes rapidly at the rising edge and at the falling edge. When this control signal j is passed through, for example, a low-pass filter 2 shown in FIG. 1, a response signal m shown in FIG. 4 is obtained. Time T is the transient response of this waveform.

A portion of time T2 is sampled at a period sufficiently shorter than this transient response. Then, the amplitude values obtained at each sampling point are converted into digital data and stored in the 80M section 15 from address to address L. -For example, L
0.1 is stored in each address.

Further, the sine wave oscillator 11 oscillates a single frequency sine wave i having a frequency r3. Then, the oscillated sine wave i is output to the multiplier 16.

In such a state, the control signal generator 12 generates an on/off control signal j when transmitting sub information.
generate. The counter 13 starts operating in synchronization with the rise of the control signal j. If the number of addresses from address No. to address L in the 80M section 15 is M, then M is M=L.
It can be expressed as −. This M is counted up by the count value C of the counter 13 and the count value C is sent to the address generator 14.

The address generator 14 generates 80 on the basis of the count value C.
The address N of the M unit 15 is designated and output to the 80M unit 15. The 80M unit 15 takes out the amplitude value corresponding to the address N and outputs it to the multiplier 16.

Here, for example, if the number M of addresses from address to L in the 80M section 15 is set to M=L-=100, the count value C changes in synchronization with the rising edge of the control signal i.
Count up from 0 to 10100 (=, R
The OM unit 5 inputs +C to the address N= from the address generator 14.
address is specified. N=L (=+100
), the counter 13 stops operating. At this time, the count value C of the counter 13 remains set to C=100.

Then, until the next falling edge of the control signal comes, 80M
The unit 15 always receives the address N=L from the address generator 14.
(N=+100=L) address is specified.

Then, the counter 13 starts operating in synchronization with the fall of the control signal j. Here, if M = L- = 100 as in the previous example, the count value C is C = 10
Count down from 0 (=M) to O, and count down to 8
The 0M section 15 receives the address N=+ from the address generator 14.
C's address is specified.

When N=K (=+O), the operation of the counter 13 is stopped and the count value C remains set to C=0. Then, until the rise of the next control signal j, R
The OM unit 15 always receives the address N= from the address generator 14.
The address of K (N=+0-K) is specified.

Further, when the control signal i is in the "off" state, the address generator 14 always outputs the address of the address to the ROM section 15. Counter 13 does not operate.

The multiplier 16 uses the amplitude value of the ROM section 15 and the sine wave i of the sine wave oscillator 11 regardless of the on/off state of the control signal j.
Multiply by As a result, a sinusoidal output signal n from which high frequency components have been removed is obtained.

At this time, if the cutoff frequency of the waveform of the transient response signal m shown in FIG. 5 is fc, the frequency components included in the sine wave after multiplication are limited from DC to fc. That is, if the oscillation frequency of the sine wave oscillator 11 is r, the frequency spectrum of the sine wave after multiplication is f, -fc
If the main transmission band is set from fl to 12 as shown in Fig. 5, then fz<fi
By setting fc, high frequency components are removed and do not affect the main data signal.

〔Effect of the invention〕

As explained above, the present invention enables transmission of sub-information at a single frequency without affecting the main data transmission, without using a conventional single frequency generation circuit (unstable, high-order narrowband filter). There is an effect that can be done.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a single frequency generation circuit according to an embodiment of the present invention, and FIGS. 2(a) to (C) show control signals and sub information generated in the single frequency generation circuit of FIG. FIG. 3 is a block diagram of a single frequency generation circuit according to another embodiment of the present invention, and FIG. 4 is a diagram showing the time characteristics of a signal. FIG. Figure 5 shows the frequency spectrum of the main data signal and the sub information signal output from the single frequency generation circuit of Figures 1 and 3. Figure 6 is a block diagram showing a conventional single frequency generation circuit, and Figure 7 shows the time characteristics when a single sine wave is turned on and off by a control signal in the single frequency generation circuit of Figure 6. FIG. l... Control signal generator 2... Low pass filter 3... Single sine wave oscillator 5... Multiplier output 1 Figure □ Between time and q

Claims (1)

[Claims] (1) A single frequency generation circuit that transmits sub information along with a main data signal at a single frequency on and off, comprising a control signal generation means for generating an on and off control signal, and the control signal generation circuit. a removing means for removing a component of a predetermined frequency or higher included in a control signal from the means; a generating means for generating a sine wave signal of a single frequency; a control signal from the removing means and a sine wave from the generating means; Multiply the signal and
and multiplication means for transmitting sub-information using an output signal generated by this multiplication.