JPH03280645A - data phase modulation circuit - Google Patents

Abstract

PURPOSE:To make no adjustment of a data phase modulation circuit by providing a phase inversion circuit and a carrier changeover circuit or the like and switching two carriers whose phases are inverted to each other based on a data signal so as to apply phase modulation. CONSTITUTION:The circuit is provided with an oscillation circuit 1 oscillating a 1st carrier, a phase inverting circuit 9 inverting the phase of the 1st carrier to form a 2nd carrier, a carrier changeover circuit 10 selecting the 1st carrier or the 2nd carrier based on a level of a data signal to form a modulation signal and a changeover circuit 8 sending the modulation signal outputted from the carrier changeover circuit 10 for a data transmission period only in response to a modulation wave transmission control signal. Then the two carriers whose phases are inverted to each other are formed, the modulation signal is formed by selecting any of the carriers based on the level of the data signal and the modulation signal is sent for the data transmission period only in response to the modulation wave transmission signal. Thus, no adjustment of the level of the data signal is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a data phase modulation circuit for a CATV terminal converter used in a CATV system that performs bidirectional data communications.

2. Description of the Related Art As a conventional data phase modulation circuit for the CATV terminal converter, there is a data phase modulation circuit that modulates a carrier wave with a data signal using a double balanced modulation circuit.

A conventional data phase modulation circuit for a bidirectional CATV converter will be described below with reference to the drawings.

FIG. 7 is a block diagram showing the circuit configuration of a conventional data phase modulation circuit.

A conventional data phase modulation circuit includes a carrier wave oscillation circuit 1 that oscillates a carrier wave a, a level adjustment circuit 3 that adjusts the level of a data signal input from a data input terminal 2, and a carrier wave a.
a double balanced modulation circuit 4 which applies amplitude modulation to the data signal C adjusted by the level adjustment circuit and outputs a modulation signal d;
An amplifier circuit 5 that amplifies the modulated signal d, and a modulated wave sending control signal e inputted from the modulated wave sending control signal input terminal 7.
The switching circuit 8 outputs the modulated signal d amplified by the amplifier circuit 5 to the output terminal 7 as a modulated wave output signal f only during the data transmission period.

The operation of the data phase modulation circuit having the above configuration will be explained with reference to the operational waveform diagram of FIG. 8.

The carrier wave a oscillated by the carrier wave oscillation circuit 1 is input to the double balanced modulation circuit 4. On the other hand, the data signal inputted from the data input terminal 2 is inputted to the double balanced modulation circuit 4 via the level adjustment circuit 3. The double balanced modulation circuit 4 applies 200% amplitude modulation to the carrier wave a using the data signal C adjusted by the level adjustment circuit 3, and outputs a modulation signal d.

As shown in FIG. 8, the phase of the carrier wave of the modulation signal d is inverted in response to the low level and high level of the data signal S. After the modulation signal d is amplified by the amplifier circuit 5, it is sent to the switching circuit 8.
is input to. The switching circuit 8 outputs the modulated signal as the modulated wave output signal f to the output terminal 7 only during the data transmission period in response to the modulated wave output control signal e inputted from the modulated wave output control signal input terminal 6.

Problems to be Solved by the Invention However, in the conventional circuit configuration, it was necessary to adjust the level of the data signal so that the modulation signal d was 200% amplitude modulated in the double-balanced modulation circuit 4 that performs data modulation.

FIG. 9 shows waveforms when the amplitude modulation of the double-balanced modulation circuit 4 is misadjusted and when normal 200% amplitude modulation is performed, and the problem will be explained by comparing these waveforms.

In FIG. 9, g is a data signal demodulated from a normal modulation signal d, d' is a modulation signal when amplitude modulation is out of adjustment, and g' is the demodulated data signal.

As can be seen from FIG. 9, the data signal g can be demodulated faithfully to the original data signal from the 200% modulation signal d, but the demodulated data signal It was not possible to reproduce as faithfully as g', which caused data errors.

The present invention is intended to solve the above-mentioned problems, and aims to provide a data phase modulation circuit in which the level of a data signal is not adjusted due to the circuit configuration.

Means for Solving the Problems In order to solve the above problems, the data phase modulation circuit of the first invention includes an oscillation circuit that oscillates a first carrier wave, and a second carrier wave that inverts the phase of the first carrier wave. a carrier wave switching circuit that switches the first carrier wave and the second carrier wave depending on the level of the data signal to form a converted signal; and a carrier wave switching circuit that converts the modulated signal output from the carrier wave switching circuit into a modulated wave. It consists of a switching circuit that transmits data only during the data transmission period in response to a transmission control signal.

Furthermore, a second invention includes an oscillation circuit that oscillates a carrier wave, a switching circuit that transmits the carrier wave only during a data transmission period according to a carrier wave transmission control signal, and a carrier wave output from the switching circuit that is input as a first carrier wave. and a phase inversion circuit that inverts the phase of the first carrier wave to form a second carrier wave, and a carrier wave switching circuit that switches the first carrier wave and the second carrier wave depending on the level of the data signal to form a modulated signal. It is composed of circuits.

Effect: With the configurations of the first and second inventions, two carrier waves with inverted phases are formed, these carrier waves are switched depending on the level of the data signal to form a modulated signal, and data is sent out in accordance with the modulated wave sending signal. Only rililI is sent. Therefore, the need for level adjustment of the circuit as in the conventional circuit is eliminated, and the circuit configuration is simplified compared to the conventional circuit.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. Components that are the same as those of the conventional example shown in FIG. 7 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 is a block diagram of a data phase modulation circuit showing one embodiment of the present invention.

The data phase modulation circuit of the present invention includes a carrier wave oscillation circuit 1, a phase inversion circuit 9 which inputs a carrier wave a and forms a second carrier wave l by inverting the phase of the carrier wave a by 180 degrees, a first carrier wave a and a first carrier wave a. The carrier wave switching circuit 10 inputs a carrier wave l of 2 and forms a modulated signal n by switching according to the level of the data signal S, and a switching circuit 8 inputs the modulated signal n.

Eleven data phase modulation circuits having the above configuration will be explained with reference to the operating waveform diagrams of FIGS. 2 and 3.

The first carrier wave a output from the carrier wave oscillation circuit 1 is input to the carrier wave switching circuit 10, and the first carrier wave a is input to the phase inversion circuit 9, and as shown in FIG.
A second carrier wave l whose phase is inverted by 1800 is formed and output to the carrier wave switching circuit 10. Carrier wave switching circuit 1
The first carrier wave a and the second carrier wave l that are input to the carrier wave 0 are switched as shown in FIG. n is output. The modulated signal n is input to the switching circuit 8, and the switching circuit 8 is connected only during the data transmission period, that is, while the control signal e is at a high level, by the modulated wave transmission control signal e inputted from the modulated wave transmission control signal input terminal 6. state, and outputs the modulated signal n to the output terminal 7 as a modulated wave output signal f, as shown in FIG.

FIG. 4 shows a specific circuit example of the block diagram of FIG. 1.

The phase inversion circuit 9 is composed of an inverter 11, and the carrier switching circuit 10 is composed of an inverter 12 which inputs the data signal.
, a two-man NA that inputs the first carrier wave a and the data signal
An ND gate 13, a two-man NAND gate 14 that receives the second carrier wave l and the output signal of the inverter 12, and an output signal of the two-man NAND gate 13 and a two-man NAND
The switching circuit 8 is composed of a two-man powered NAND gate 15 which receives the output signal of the D gate 14 as an input, and the switching circuit 8 comprises a two-man powered NAND gate 16 which receives a modulation signal n and a modulated wave transmission control signal e as input.

The operation of the circuit shown in FIG. 4 will be explained.

The first carrier wave a oscillated by the carrier wave oscillation circuit 1 is input to the two-man NAND gate 13 of the carrier wave switching circuit 10, and the first carrier wave a is further input to the inverter 11, where the phase is inverted and becomes the second carrier wave l. The carrier wave switching circuit 10
The signal is input to the two-man NAND gate 14. On the other hand, the data signal is a two-man NAND gate 1 of the carrier switching circuit 1o.
3, and further input to the inverter 12 of the carrier wave switching circuit 0, and after being inverted, the 2-manufactured NAND gate 1
4 is input. The two-man NAND gate 13 outputs the first carrier wave a while the data signal is at a high level, and
The manual NAND gate 14 outputs the second carrier wave l while the data signal is at a low level. In the two-man NAND gate 15, the first carrier wave a of the data signal Suga high level and the second carrier wave l of the data signal Suga low level are combined and output as a modulation signal n, which is then switched. circuit 8
The signal is input to the two-man NAND gate 16. On the other hand, the harmonic transmission control signal e is the two-man power NAND gate 1 of the switching circuit 8.
6, and outputs the modulated wave signal f only while the control signal C is at a high level.

In this way, by transferring the second signal using the phase inverting circuit 9 and outputting it, it is possible to perform phase modulation, and there is no need for level adjustment to the data signal, making it possible to eliminate the need for adjustment. Furthermore, it is possible to provide an inexpensive and stable data phase modulation circuit that can be easily constructed using general-purpose logic elements.

Next, another embodiment of the present invention will be described based on the block diagram of FIG.

The data phase modulation circuit shown in FIG. 5 is obtained by connecting the switching circuit 8 of FIG. 1, the phase inverting circuit 9, and the carrier switching circuit 10 in reverse order. The operation will be explained below with reference to the operation waveform diagram in FIG.

The carrier wave a output from the carrier wave oscillation circuit 1 is input to the switching circuit 8. On the other hand, carrier wave transmission control signal input terminal 6
The carrier wave transmission control signal C input from the carrier wave a is also input to the switching circuit 8, and as shown in FIG. It is output as a carrier wave t. 1st
The carrier wave t is input to the carrier wave switching circuit 10, and the first carrier wave t
The carrier wave t is input to the phase inversion circuit 9, and is input to the carrier wave switching circuit 10 as a second carrier wave U whose phase is inverted by 180° as shown in FIG. Carrier wave switching circuit 10
As shown in FIG. 6, when the data signal b input from the data input terminal 2 is at the high level, the first carrier wave is switched to the second carrier wave U when the level is t10-, and the modulated wave is output. A signal f is obtained.

In the other embodiment shown in FIG. 5, as in the embodiment shown in FIG. 1, it is possible to eliminate level adjustment and provide an inexpensive and stable data phase modulation circuit.

Effects of the Invention As described above, according to the present invention, by performing phase modulation by switching two phase-inverted carrier waves using a data signal, it is possible to eliminate the need for adjustment of a data phase modulation circuit, and to use mainly general-purpose logic elements. This can be realized with a simple circuit configuration using a simple circuit configuration, and it is possible to provide an inexpensive and stable phase modulation circuit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a data phase modulation circuit showing an embodiment of the present invention, FIGS. 2 and 3 are signal waveform diagrams of each part of FIG. 1, and FIG. 4 is a data phase modulation circuit of FIG. 1. 5 is a block diagram of a data phase modulation circuit showing another embodiment of the present invention, FIG. 6 is a signal waveform diagram of each part of the fifth factor,
The 7th prisoner is a block diagram of a conventional data phase modulation circuit, and the 8th prisoner is a block diagram of a conventional data phase modulation circuit.
The cause is shown in the signal waveform diagram of each part in FIG. 7, and FIG. 9 is a signal waveform diagram for explaining the conventional problem. l...Carrier wave oscillation circuit, 2...Data input terminal, 6
...Modulated wave sending control signal input terminal, 7...Output terminal, 8...Switching circuit, 9...Phase inversion circuit, 10...
・Carrier wave switching circuit, a, t... (first) carrier wave, b
...Data signal, e...Modulated wave transmission control signal, f.
...Modulated wave output signal, 1. u...second carrier wave, n...
...Modulation signal.

Claims (1)

[Claims] 1. A data phase modulation circuit for a CATV terminal converter that performs bidirectional data communication, which includes an oscillation circuit that oscillates a first carrier wave, and a second carrier wave that inverts the phase of the first carrier wave. a phase inversion circuit that forms a second carrier wave, a carrier switching circuit that switches the first carrier wave and the second carrier wave depending on the level of a data signal to form a modulated signal, and a modulated signal output from the carrier switching circuit. A data phase modulation circuit consisting of a switching circuit that transmits data only during the data transmission period according to a modulated wave transmission control signal. 2. A data phase modulation circuit for a CATV terminal converter that performs bidirectional data communication, including an oscillation circuit that oscillates a carrier wave, a switching circuit that transmits the carrier wave only during a data transmission period according to a carrier wave transmission control signal, and the a phase inversion circuit that inputs the carrier wave output from the switching circuit as a first carrier wave and inverts the phase of the first carrier wave to form a second carrier wave; A data phase modulation circuit consisting of a carrier switching circuit that switches depending on the level of the data signal to form a modulated signal.