JPS6228090Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a balanced amplifier, particularly to a balanced circuit with a bias circuit.

A balanced amplifier consists of one 90° power equal division circuit, for example, a 90° hybrid and a pair of amplifier circuits, and one
It consists of a 90° power combining circuit, has good input/output impedance over a wide band, and has low loss on the input side 90° hybrid, so it is widely used as a low-noise, wide-band preamplifier. be. However, in recent years, bias circuits for auxiliary equipment have been built into this balance amplifier, thereby making the auxiliary equipment smaller and simpler. This is because it is simple and effective to use the power of the balanced amplifier as the power source for the bias circuit for external equipment.

However, with such a configuration, as will be explained in detail later, the input impedance of the input terminal will be significantly degraded, degrading the aforementioned good characteristics of the balanced amplifier itself, and a circuit to compensate for this will be required. Providing this would have disadvantages in other respects, and was by no means desirable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a balanced amplifier with a bias circuit that does not impair its characteristics as a balanced amplifier even when a bias circuit for external equipment is connected.

According to the present invention, a 90° power dividing circuit, a pair of amplifiers each receiving the two outputs of the 90° power dividing circuit as inputs, and a 90° power combining circuit receiving the outputs of the pair of amplifiers as inputs. In the balanced amplifier with a bias circuit, which is formed by adding a bias circuit for supplying to an external device to a balanced amplifier having a bias circuit, the bias circuit is connected to at least one side of the input and output of the pair of amplifiers. A balanced amplifier with a bias circuit is obtained, which is characterized in that it is connected to an equipment bias circuit.

Next, a detailed explanation will be given with reference to the drawings.

FIG. 1 is a block diagram showing an example of the circuit configuration of a conventional balanced amplifier with a bias circuit for external equipment. In Figure 1, 1 is the input terminal, 2 is the input side 90° hybrid (90° equal power division circuit) with one side of this input terminal terminated with 50Ω, 3 and 4 are amplifiers with the same characteristics, and 5 is one side of the output terminal. 6 is a bias circuit for external equipment consisting of an inductor L, a bypass capacitor C, and a resistor R, and 7 is an output terminal. When the external device bias circuit 6 is connected to the input terminal 1 of the input side 90° hybrid 2 in this way, the input impedance of the input terminal 1 will be significantly degraded, so the advantage of the balanced configuration, which has good input impedance characteristics over a wide band, will be reduced. It was damaged.
In order to compensate for this input impedance deterioration, it has been proposed to add a new matching circuit before the bias circuit, but from the viewpoint of shape, size, weight, loss, and complexity of matching,
There is little versatility, and the benefits as a balanced amplifier are further reduced.

FIG. 2 shows a block diagram of the circuit configuration of an embodiment of the present invention. Components in FIG. 2 in the same positions and having the same functions as those in FIG. 1 are indicated by adding 10 to the reference numerals in FIG. In Fig. 2, the two output terminals of the input side 90° hybrid 12 and the two input terminals of the two amplifiers 13 and 14 with the same characteristics have the same function as 6 in Fig. 1. However, bias circuits 18 and 19 for external equipment, which are located in completely different locations, are separately connected to the two signal paths. And 15 is a 90° hybrid on the output side. Therefore, the transmission characteristics of both signal paths are exactly the same, and it is possible to supply a bias to the external equipment connected to the input terminal 11 and obtain a good input impedance. If one of the external device bias circuits is not used, connect a dummy load to it.

FIG. 3 is a block diagram showing the circuit configuration of another embodiment of the present invention. Components of this circuit having the same locations and functions as in FIG. 2 are given the same reference numerals. The difference between the balanced amplifier in Figure 3 and the one in Figure 2 is that
External device bias circuits 21 and 22 are also added to the output sides of amplifiers 13 and 14, respectively.
As a result, bias can be supplied not only to the input side but also to external equipment connected to the output terminal 17, and a good output impedance can be obtained. The other points are the same as those shown in FIG.

As is clear from the above two embodiments, it goes without saying that in the present invention, the bias circuit for external equipment may be provided only on the output side of the amplifier. Also, as the power equal division circuit 12, instead of a 90° hybrid, a 90° power divider is used that equally divides one signal into two signals having a phase difference of 90°, and these are used in opposite directions90.゜Power combiner,
It can be used in place of the 90° hybrid shown in 15.

As explained above, in the balanced amplifier with a bias circuit according to the present invention, bias can be supplied to external equipment connected to the input terminal or the output terminal without impairing good input/output impedance characteristics and low noise characteristics. Can be done.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an example of the circuit configuration of a conventional balanced amplifier with bias circuit.
The figure is a block diagram showing the circuit structure of one embodiment of the present invention, and FIG. 3 is a block diagram showing the circuit structure of another embodiment of the present invention. Symbol explanation: 11 is input terminal, 12 is input side 90
゜hybrid (90゜equal power division circuit), 13 and 14 are amplifiers, 15 is output side 90゜hybrid (90゜power combining circuit), 17 is output terminal, 18, 1
9, 21 and 22 represent bias circuits for external equipment, respectively.

Claims (1)

[Scope of utility model registration request] A balanced type that has a 90° power dividing circuit, a pair of amplifiers each receiving the two outputs of the 90° power dividing circuit, and a 90° power combining circuit receiving the outputs of the pair of amplifiers as inputs. In a balanced amplifier with a bias circuit, which is formed by adding a bias circuit to an amplifier to supply external equipment, the bias circuit includes a pair of bias circuits for the external equipment on at least one side of the input and output of the pair of amplifiers. A balanced amplifier with a bias circuit characterized by connecting circuits.