JPS5816815B2 - Broadband cable transmitter/receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wideband cable transmission system that efficiently and economically transmits low frequency band signals and high frequency band signals of different frequency bands using the same communication cable. The present invention relates to a signal transmitting/receiving device that is capable of transmitting signals separated into balanced image frequency components and unbalanced high frequency components, or receiving and reproducing separated signals.

Conventionally, to transmit signals, balanced cables have been used in low frequency bands, and coaxial cables have been used in high frequency bands.

Recently, however, a broadband cable transmission system has been proposed that simultaneously transmits data using a balanced cable and a coaxial cable.

That is, in this transmission system, in the broadband cable shown in FIG. 1, core wires 1 and 2 are arranged in parallel, and these core wires 1 and 2 constitute a balanced cable.
As a result, signals in the low frequency band are transmitted, and a coaxial cable is constructed by using the insulated core wires 1 and 2 as an inner conductor and the pipe-shaped conductor 3 covering it as the outer conductor, and transmits signals in the high frequency band. Transmit.

The conductor 3 acts as a thin conductor for the balanced cable.

In such broadband cable transmission systems, low-frequency P-wave filters, high-frequency filters, and (isolated) transformers are used as signal transmitting and receiving devices to appropriately separate or combine low-frequency band signals or high-frequency band signals. Appropriate combinations of these have already been proposed.

However, in this conventional transmitter/receiver, it is extremely difficult to realize a transformer that can transmit wide-band signals that have components near DC, such as baseband videophone signals. Complications are inevitable.

The present invention introduces a circuit that can obtain in-phase output and anti-phase output, such as a differential amplifier, and an all-pass circuit.
This system removes restrictions on the fractional band of the signal to be transmitted and simplifies the circuit, and the drawings from FIG. 2 onwards will be described in detail.

FIG. 2 shows an embodiment of the present invention, in which 4 is a converter, 5 is a signal source, 6 and 7 are input terminals, 8 is a differential amplifier, 9 is an in-phase output terminal, 10 is an output terminal, and 11 is an inverse Phase output terminal, 12
is an all-pass circuit, and 13.14 is an output terminal.

In this invention, for one broadband input signal having a continuous spectrum, the low frequency component is converted from a balanced type to a balanced type system, and the high frequency component is converted from a balanced type to a coaxial type system as shown in Fig. 2. A conversion device 4 constructed of a differential amplifier and an all-pass circuit shown in FIG. 1 is used.

Here, the all-pass circuit is a known circuit in which the phase is opposite to the high frequency component of the input signal, and the phase is the same as the low frequency component of the input signal.

In FIG. 2, the low frequency component of the signal from the wideband input signal source 5 is output from the input terminals 6 and 7 through the in-phase output terminal 9 of the differential amplifier 8 to the output terminal 10 in the same phase with respect to the input. From the negative phase output terminal 11 of the differential amplifier 8 to the all-pass circuit 12, for example, the transmission coefficient is (α-Jω)/α+jω)
The signal passes through the primary circuit as it is and is output to the output terminal 13 in a phase opposite to the input.

Therefore, the low frequency component of the input signal is transmitted to the insulated core wires 1 and 2 connected to the output terminal 10.13 in a balanced mode (pair cable transmission system).

On the other hand, the high frequency component of the signal source 5 is outputted from the input terminal 6°7 through the in-phase output terminal 9 of the differential amplifier 8 to the output terminal 10 in the same phase with respect to the input, and is further outputted from the in-phase output terminal 11 of the differential amplifier 8. The signal then passes through the all-pass circuit 12, has its phase inverted, and is output to the output terminal 13.

Therefore, the output terminal 13 and the output terminal 10 are output in the same phase, and therefore the high frequency component of the signal is transmitted between the output terminal 14 and the output terminal 10.13. system).

When the converter 4 is applied to a receiving device, one of the input terminals 6 and 7 of the differential amplifier 8 is connected to the terminal 10 and the other is connected to the all-pass circuit 12. In other words, only the direction of the amplifier 8 in FIG. 2 is reversed. By doing so, a wideband signal can be obtained from the output terminals 9 and 11.

In the device of the present invention, the higher the all-pass circuit is used as the all-pass circuit, the lower the frequency component whose phase rotation becomes in-phase;
The boundary characteristics with the high-frequency component whose phase rotation is opposite to each other become clear, and the band in which both coaxial transmission and balanced transmission are performed becomes narrower.

As explained above, since the present invention does not use a transformer, there is no restriction on the fractional band by the transformer, and wideband transmission becomes possible.

Further, the circuit configuration is simplified since a p-wave device for frequency component separation is not particularly required, and the terminal station for the balanced type/coaxial type common cable can therefore be simplified accordingly.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of a broadband cable to which the present invention is applied;
FIG. 2 is a connection diagram showing an example of the transmitting side of the transmitting/receiving apparatus according to the present invention. 1.2... Insulated core wire, 3... External conductor, 4... Conversion device, 8... Differential amplifier, 12...・All-pass circuit.

Claims (1)

[Claims] 1 Balanced transmission is performed by the above two insulated core wires of a broadband cable consisting of two parallel insulated core wires and an outer conductor centered on these, and unbalanced transmission is performed by the above insulated core wires and the above outer conductor. In a transmitting/receiving device for wideband transmission, a first differential amplifier is provided on the transmitting device side, a signal source is connected between a pair of input terminals of the first differential amplifier, and one output terminal of the first differential amplifier and the second differential amplifier are connected to each other. The other output terminal of the first differential amplifier is connected to one side of the main insulated core wire, and the other output terminal of the first differential amplifier is connected to a first range where the phase rotation is in the same phase in the low frequency band component and the phase rotation is in opposite phase in the high frequency band component. It is connected to the other of the two insulated core wires through a pass circuit, the common terminal of the first all-pass circuit is connected to the external conductor, and a second differential amplifier is provided on the receiver side. One input terminal of the second differential amplifier is connected to one of the two insulated core wires, and the other input terminal of the second differential amplifier has the same phase rotation in the low frequency band component and the high frequency band The component is connected to the other of the two insulated core wires via a second all-pass circuit whose phase rotation is opposite in phase, and a common terminal of the second all-pass circuit is connected to the external conductor. A wideband cable transmitting/receiving device characterized in that low frequency band components can be transmitted in a balanced mode using the wideband cable, and high frequency band components can be transmitted in an unbalanced mode.