JPS6163116A - Variable attenuator - Google Patents

Abstract

PURPOSE:To attain miniaturization and variable attenuation by means of an electric signal by changing the combination of resistor arrays by means of a digital signal to attenuate an analog signal inputted to a reference voltage input terminal of a D/A converter. CONSTITUTION:An analog signal is inputted to a reference voltage input terminal Vref of the D/A converter 3, a digital signal is inputted from a digital signal input section and latched by a data latch section 4. A prescribed switch of switches SW1-SWN is switched by the value of latched data to change the combination of the resistor array 5, the current amount weighted in binary is controlled to change the attenuation. The attenuated analog signal is inputted from an output terminal OUT to an operational amplifier 6, converted into a voltage and then outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable attenuator used in a PCM terminal station, etc., and more particularly, to a variable attenuator whose attenuation amount can be varied by an electrical signal.

As digital communication networks become more diverse and sophisticated, the demand for flexible PCM transmission is increasing.

Accordingly, there is a need for a centralized management system that manages many PCM terminal devices collectively instead of managing and operating the PCM terminal devices individually.

For this purpose, it is necessary to perform isolation control using electrical signals for each function of the PCM terminal equipment.

In addition, each component of the device must not only be controllable by electrical signals, but must also satisfy requirements such as space saving.

Therefore, there is a demand for a variable attenuator that is small and can be varied by electrical signals.

[Prior art and problems to be solved by the invention] FIG. 2 is a circuit diagram of a conventional variable attenuator.

1 in the figure shows an attenuator group composed of a thick film resistor array,
2.2-1 to 2-1O indicate switching terminals.

Attenuator group 1 consisting of a thick film resistor array shown in Fig. 2
A conventional variable attenuator configured with switching terminals 2.2-1 to 2-10 is small, but in order to change the amount of attenuation, it is necessary to This has to be done by cutting or connecting parts, and there is a problem that it cannot be changed by electrical signals.

[Means for solving problems]

The above problem can be solved by inputting an analog signal to the reference voltage input terminal of the digital-to-analog converter, and using the digital signal to attenuate the analog signal to an arbitrary level by changing the combination of the resistor strings of this digital-to-analog converter. This problem is solved by the variable attenuator of the present invention.

[Effect]

The present invention provides an operation in which a digital-to-analog converter (hereinafter referred to as a D/A converter) weights a reference voltage by changing the combination of resistor strings according to an input digital signal, and outputs it as an analog signal. In this case, an analog signal is inputted from a reference voltage input terminal, and the combination of the resistor strings is changed using a digital signal, and this analog signal is attenuated to an arbitrary level and output.

Therefore, the amount of attenuation can be varied by an electric signal, and since this D/A converter can be constructed using a single-layer chip carrier IC, it can be made extremely compact.

〔Example〕

FIG. 1 is a block diagram showing the configuration of a variable attenuator according to an embodiment of the present invention.

In the figure, 3 is a D/A converter, 4 is a data latch section, 5 is a resistor string, 6 is an operational amplifier, and SWI to SWN are switches.

In FIG. 1, the reference voltage input terminal Vre of the D/A converter 3
An analog signal is input to f, and an 8-bit digital signal, for example, is input from the digital signal input section, and the data latch section 4 latches the data. By switching the switch and changing the combination of the resistor strings 5, the amount of attenuation is changed by controlling the binary weighted current amount, and the attenuated analog signal is input to the operational amplifier 6 from the output terminal OUT, and the voltage is Convert to quantity and output.

Note that the operational amplifier 6 corrects the reference amount so that a through state is realized when all the switches 5WI-3WN are switched to the dotted line side.

In this way, the amount of attenuation can be varied by the electric signal, and there is no deterioration of the AC characteristics of the input signal and output signal, and the D
Since the /A converter 3 can be constructed using a leadless chip carrier IC, it can be made extremely compact.

This time, we used an 8-bit D/A converter to create a variable attenuator from 0 to 16 db with variable steps of 0.5 db, mounted it on a PCM terminal equipment, measured the transmission characteristics, and found that it met the standard for PCM terminal equipment. However, good characteristics were obtained.

〔Effect of the invention〕

As described in detail above, the present invention has the advantage of providing a small variable attenuator that is capable of varying the amount of attenuation using an electrical signal.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a variable attenuator according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional variable attenuator. In the figure, 1 is an attenuator group, 2.2-1 to 1-10 are switching terminals, 3 is a digital-to-analog converter, 4 is a data launch section, 5 is a resistor string, 6 is an operational amplifier, and SWI to SWN are switches shows.

Claims (1)

[Claims] An analog signal is input to the reference voltage input terminal of a digital-to-analog converter, and the analog signal is attenuated to an arbitrary level by changing the combination of resistors in the digital-to-analog converter using the digital signal. A variable attenuator featuring: