JPS5847081B2 - Waveguide transistor amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transistor amplifier using a rectangular waveguide.

Transistors that operate using microwaves have made remarkable progress, and recently it has become possible to realize transistors that have low noise characteristics in the X band or higher.

That is, Si bipolar transistors are capable of low-noise amplification in the C-band of about 1, while GaAs field-effect transistors are now capable of low-noise amplification in the X-band and above.

When constructing a microwave receiver, a low noise amplifier is provided upstream of a reception mixer in order to lower the noise figure of the receiver.

Conventionally, parametric amplifiers, tunnel diode amplifiers, and the like have been available as low-noise amplifiers that can be implemented in the X band or higher.

However, parametric amplifiers require an excitation source that is much higher than the signal frequency, require a circulator because they are reflective progressive amplifiers, and require various measures to stabilize the gain. The drawbacks were that the device was quite large and complex, and the price was high.

Furthermore, since the tunnel diode amplifier is a reflective progressive amplifier, it has disadvantages such as requiring a circulator and having a low saturation output.

Under these circumstances, there has been a demand for a solid-state low-noise amplifier having features such as simple configuration, stability, small size, and low cost.

On the other hand, improvements in the performance of Schottky and mixer diodes using GaAs have made it possible to achieve a noise figure of 4.5 dB or less in the It's here.

However, if a low-noise amplifier with a simple configuration and lower noise than a mixer can be realized, the performance of the receiver can be further improved.

Transistor amplifiers have been considered as low-noise amplifiers that satisfy the above requirements, and various attempts have been made.

In general, the input aperture of a microwave receiver that operates in the X band or above is often composed of guided sound, and it is desirable that the input aperture of a low-noise amplifier is also a waveguide.

A block diagram of a conventional waveguide transistor amplifier is shown in FIG.

In Figure 1, 1 is the signal input aperture, 2 is the signal output aperture,
3 is a coaxial connector 1; 4 is a coaxial connector 2; 5 is a coaxial waveguide converter; and 6 is a MIC transistor amplifier.

A signal entering through the signal input aperture 1 is once converted from the waveguide mode to the coaxial mode by the coaxial waveguide converter 5, and then guided to the MIC transistor amplifier 6, where it is amplified and output from the signal output aperture 2.

Noise figure NF of a transistor amplifier with such a configuration
sys is the loss of the single-axis microstrip converter and the loss NF1 (dB) of the input matching circuit composed of the microstrip line at the first-stage transistor input terminal 1: the noise figure after the first-stage transistor.

For the X band and above, the values of Ll and L2 are not so small that they can be ignored, and it is extremely difficult to construct an amplifier with sufficiently low noise using the waveguide transistor amplifier configured as shown in Figure 1. there were.

Furthermore, the presence of a coaxial connector between the coaxial waveguide converter 5 and the MIC transistor amplifier 6 poses a problem in terms of miniaturization.

In order to eliminate these drawbacks, the present invention provides a coaxial waveguide converter with a special structure in which a transistor is mounted on the coaxial/cowave tube conversion section, and will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of this invention.

FIG. 3 is a sectional view of FIG. 2.

In Figure 2, 7 is a metal plate, 8 is a bias terminal, 9 is a first stage transistor, 10 is an input terminal of the first stage transistor,
11 is an output terminal of the first stage transistor, and 12 is a ground terminal of the first stage transistor.

In the sectional view of FIG. 3, 13 is a dielectric thin plate, and 14 is a ceramic substrate.

As shown in FIG. 2, a metal plate 7 is installed at the center of the H-plane of the rectangular waveguide parallel to the E-plane, and one end of the metal plate 7 is formed by a dielectric thin plate 13 forming a high-frequency bypass capacitor as shown in FIG.

The other end of the metal plate 7 is the input terminal 1 of the first stage transistor 9
Connected to 0.

Matching of the input circuit can be achieved by selecting the shape button of the metal plate 7 and the distance from the metal plate 7 to the short-circuited end 1 of the rectangular waveguide.

A microwave circuit constructed by inserting a metal plate parallel to the E-plane in the center of the H-plane of a rectangular waveguide is called a three-dimensional planar circuit, and has recently been put into practical use in filters, mixers, etc.

A normal ceramic substrate 14 is used after the first stage transistor.
A MIC transistor amplifier 6 configured as shown in FIG.

As described above, according to the present invention, since the transistor is directly connected to the input waveguide circuit having a three-dimensional planar circuit structure, Ll in equation (1) is significantly reduced.

Furthermore, since the first stage transistor is directly connected to the input waveguide circuit, L2 in Option 1) does not exist.

Therefore, it is possible to construct a waveguide type low-noise transistor amplifier with a simple configuration without impairing the low-noise characteristics of the first-stage transistor.

Although the case where the metal plate 7 has a rectangular shape has been described above, the present invention is not limited to this, and the metal plate may have a tapered shape.

Alternatively, it may be a metal plate with a broadband matching circuit added thereto.

Furthermore, although the structure in which the short-circuit end of the waveguide is separated from the metal plate 7 has been described above, the metal plate 7 may have a short-circuit mechanism.

As described above, in the waveguide type transistor amplifier according to the present invention, since the first stage transistor is directly connected to the input waveguide circuit having a three-dimensional planar circuit structure, the loss of the input circuit in the first stage transistor 1 can be reduced. There is an advantage that a waveguide type transistor amplifier having a simple structure and low noise characteristics can be constructed.

[Brief explanation of drawings]

Figure 1 is a configuration diagram of a conventional waveguide transistor amplifier.
FIG. 2 is a block diagram of a waveguide transistor amplifier of the present invention, and FIG. 3 is a sectional view of FIG. 2. In the figure, 1 is a signal input opening, 2 is a signal output opening, 3.4 is a coaxial connector, 5 is a coaxial waveguide converter, 6 is an MIC transistor amplifier, 7 is a metal plate, 9 is a first stage transistor, and 13 is a It is a dielectric thin plate. In the figures, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1. In a waveguide type transistor amplifier whose signal input aperture is composed of a rectangular waveguide, the rectangular waveguide is structured so that it can be divided into two at the E plane in the center of the H plane, and there is a A waveguide transistor amplifier characterized in that one end of a metal plate parallel to the E plane is provided via a dielectric thin plate, and the other end of the metal plate is connected to an input terminal of a first stage transistor.