JPH04361415A - Power variable attenuator - Google Patents

Abstract

PURPOSE:To attenuate power continuously without production of heat. CONSTITUTION:A distribution circuit bisects an input power to be outputted as power signals P1, P2. A variable phase shift circuit 2 gives a phase shift designated by a control signal S to the power P2. A synthesis circuit 3 synthesizes an output power P3 of the variable phase shift circuit 2 and the bisected other power P2 in terms of vector and the result is outputted as an output power Po.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to variable power attenuators.

0002

2. Description of the Related Art A conventional power variable attenuator has a plurality of attenuation circuits formed of resistors and having different amounts of attenuation, and the attenuation circuits are selected so as to obtain a predetermined amount of attenuation.

0003

The conventional variable power attenuator described above uses a resistor to consume and attenuate power, so when attenuating a large amount of power, care must be taken to prevent the resistor from burning out. Another problem is that it is difficult to continuously vary the amount of attenuation.

An object of the present invention is to provide a variable power attenuator that can continuously attenuate power without generating heat.

[0005]

[Means for Solving the Problems] The variable power attenuator of the present invention includes a distribution circuit that divides input power into two, and a variable power attenuator that provides a specified amount of phase shift to one of the two power divided by the distribution circuit. The variable phase shift circuit includes a phase shift circuit, and a synthesis circuit that performs vector synthesis of the output power of the variable phase shift circuit and the other power divided into two by the distribution circuit.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, which includes a distribution circuit 1 that divides input power into two and outputs it as power P1 and P2, and one power P1 that is divided into two by the distribution circuit 1. A variable phase shift circuit 2 that provides a specified amount of phase shift to
and the other electric power P2 divided into two by the distribution circuit, and a combining circuit 3 that performs vector synthesis of the electric power P2 and the other electric power P2 divided into two by the distribution circuit, and outputs the resultant as electric power Po.

Here, the variable phase shift circuit 2 can continuously provide a phase shift of an amount specified by the control signal S. Also, the electric power P1, P divided into two by the distribution circuit 1
2 has a power that is 1/2 of the input power Pi and is in the same phase.

FIG. 2 is a vector diagram for explaining the operation. Now, when the phase shift amount of the variable phase shift circuit 2 is 0, the power P3 is in the same phase as the power P1, and therefore the output power Po vector-combined by the combining circuit 3 is as shown in FIG.
As shown in a), the power is the same as the input power Pi.

When the amount of phase shift of the variable phase shift circuit 2 is θ, as shown in FIG. 2(b), the power P3 and the power P1 are vector-combined with a phase difference θ to form the output power Po.
The input power Pi can be attenuated.

When the phase shift amount of the variable phase shift circuit 2 is 180°, as shown in FIG. 2(c), the power P3 and the power P1 are
The phase is opposite to that, and the output power Po is zero.

In this way, the amount of attenuation can be varied from 0 to infinity depending on the amount of phase shift of the variable phase shift circuit 2.

[0013]

[Effects of the Invention] As explained above, the present invention divides the input power into two parts, gives a phase shift to one of the two divided powers, and vector-combines it with the other divided power, which is different from the conventional one. The amount of attenuation can be changed continuously from 0 to infinity without generating heat.

[Brief explanation of the drawing]

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

FIG. 2 is a vector diagram for explaining the operation of this embodiment.

[Explanation of symbols]

1 Distribution circuit 2. Variable phase shift circuit 3. Synthesis circuit

Claims (1)

[Claims] Claim 1: A distribution circuit that divides input power into two parts, a variable phase shift circuit that provides a specified amount of phase shift for one of the two parts of the power divided by the distribution circuit, and an output power of the variable phase shift circuit. A variable power attenuator, comprising: a combination circuit for vector-synthesizing the power and the other power divided into two by the distribution circuit.