JP4641285B2 - Microwave amplifier - Google Patents

Description

  The present invention relates to a microwave amplifier used in microwaves and millimeter waves.

  A conventional microwave amplifier will be described with reference to the drawings. FIG. 5 is a diagram showing a configuration of a conventional microwave amplifier (see, for example, Patent Document 1).

  In FIG. 5, a conventional microwave amplifier has a gate connected to an input terminal 2, a drain connected to an output terminal 3, a source grounded, and a FET connected to the gate of the FET 1. A bias circuit 4 is provided.

  The bias circuit 4 is provided with a quarter wavelength transmission line 41, a quarter wavelength open stub 42, a resistor 43, a capacitor 44, and a bias power supply terminal 45 for applying a bias.

  Since the 1/4 wavelength open stub 42 constituting the bias circuit 4 has an electrical length of 1/4 wavelength, the connection point between the 1/4 wavelength transmission line 41 and the 1/4 wavelength open stub 42 is at the frequency used. It becomes a short circuit point. Since the front end of the quarter wavelength transmission line 41 is a short circuit point, the impedance when the quarter wavelength transmission line 41 side is viewed from the input terminal 2 is opened at the frequency to be used. At the frequency used, the impedance viewed from the bias circuit 4 side is open, and no signal flows to the bias circuit 4 side. A signal input from the input terminal 2 does not flow to the bias circuit 4 but is input to the FET 1, and a signal amplified by the FET 1 is output from the output terminal 3. The bias circuit 4 can apply a direct current bias without losing the input signal at the frequency used. At a frequency other than the frequency to be used, especially at a low frequency, a signal input from the input terminal 2 flows to the bias circuit 4 and is consumed by the resistor 43. As a result, the resistor 43 acts to stabilize the FET 1 at a frequency other than the frequency to be used.

JP-A-3-192801

In the conventional microwave amplifier as described above, a DC bias can be applied and a signal can be amplified without giving a loss at a frequency to be used. However, the conventional microwave amplifier bias circuit 4 cannot realize a circuit with a small loss in a wide band. The center frequency F _C of the frequency band of the _amplifier, the upper limit frequency F _H, the lower limit frequency and F _L. Quarter-wave transmission line 41 and the quarter-wave open stub 42, the electrical length of a quarter wavelength at _{F C.} The bias circuit 4, 1/4 is constituted by a wavelength transmission line 41 and the quarter-wave open stub 42, the impedance in anticipation bias circuit 4 in _{F C} is in the open, and open the _{F H} or _{F L} Don't be. Thus, signal F _H or F _L is the input from the input terminal 2, part of the input signal flows into the bias circuit 4. Connection point of the quarter-wave transmission line 41 and the quarter-wave open stub 42, because not a short-circuit point in _{F H} or _{F L,} signal yelling flow through the bias circuit 4, a 1/4-wave transmission line 41 As a result, it is consumed by the resistor 43, resulting in a loss. When the loss of the bias circuit 4 increases the noise figure of the amplifier (hereinafter, abbreviated as NF) is so degraded, it can be seen that NF is deteriorated in F _H or F _L in the conventional microwave amplifier. As described above, the conventional microwave amplifier has a problem that it is difficult to reduce the loss of the bias circuit in a wide band and it is difficult to realize an amplifier having a good NF in the wide band.

  In addition, when the circuit shown in FIG. 5 is actually manufactured, since the connection point between the quarter wavelength transmission line 41 and the quarter wavelength open stub 42 has a physical size, it is difficult to make a complete short-circuit point. Since a signal slightly flows through the resistor 43 and a loss occurs, there is a problem that the NF of the amplifier deteriorates.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a microwave amplifier having a small bias circuit loss in a wide band and good noise characteristics.

Microwave amplifier according to the present invention is connected to the input terminal to the gate, the micro with is connected to the output terminal to the drain and the field effect transistor and a source is grounded, and a bias circuit connected to the gate a wave amplifier, the bias circuit, the gate end connected 1/16 or more wavelengths, one end of the first transmission line of less than 1/4-wavelength, the other end of the first heat transmission line There and a quarter-wave open stub that is connected, and a resistor having one end connected to the other end of the first heat transmission lines, 1/16 wavelength more than one to the other end of the resistor is connected, 1 / 4 wavelength or less of the second transmission line, wherein one end to the other end of the second heat transmission line is connected, a first capacitor whose other end is grounded, the other end of the second transmission line the Connected to a connection point between one end of the first capacitor It is intended to include a bias power supply terminal for applying a bias.

  The microwave amplifier according to the present invention has an effect that the loss of the bias circuit is small in a wide band and the noise characteristic is good.

Embodiment 1 FIG.
A microwave amplifier according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a diagram showing a circuit configuration of a microwave amplifier according to Embodiment 1 of the present invention. In the following, in each figure, the same reference numerals indicate the same or corresponding parts.

  1, the microwave amplifier according to the first embodiment includes a field effect transistor (FET) 1 having an input terminal 2 connected to a gate, an output terminal 3 connected to a drain, and a source grounded, and an FET 1. A bias circuit 4 connected to the gate is provided.

The bias circuit 4 is 1/16 or more wavelengths, a 1/4-wavelength transmission lines (first heat transmission lines) 41, 1/4 wavelength open stub 42, and resistor 43, 1/16 or more wavelengths, 1 / 4 wavelength or less of the transmission line and the (second heat transmission lines) 46, a capacitor (first capacitor) 44, and a bias power supply terminal 45 for applying a bias is provided.

  Next, the operation of the microwave amplifier according to the first embodiment will be described with reference to the drawings. FIG. 2 is a diagram showing frequency characteristics of the minimum noise figure (NFmin) of the microwave amplifier according to Embodiment 1 of the present invention and the conventional microwave amplifier.

The center frequency F _C of the frequency band of the _amplifier, the upper limit frequency F _H, the lower limit frequency and F _L. The ¼ wavelength open stub 42 has an electrical length of ¼ wavelength at the center frequency F _C. It is assumed that the transmission line 46 is sufficiently short-circuited in the use frequency band by the capacitor 44. When the impedance anticipation of resistor 43 side of the bias circuit 4 and Z _A, the impedance Z _A is represented by the following formula.

Here, R is the resistance value of the resistor 43, Z _C is the characteristic impedance of the transmission line 46, λ _C is one wavelength at the center frequency F _C , and θ is the electrical length. The transmission line 46 between the resistor 43 and the capacitor 44 can be increased impedance Z _A by loading. In particular, the impedance Z _A when an electrical length of the transmission line 46 is quarter wavelength becomes open, the signal is not crowded flows to the resistor 43 side.

In the microwave amplifier according to the first embodiment, a short-circuit point is formed at the center frequency F _C by the ¼ wavelength open stub 42 of the bias circuit 4 as in the conventional microwave amplifier. There is no loss. Therefore, the NF of the amplifier does not deteriorate. In the upper limit frequency F _H, the lower limit frequency F _L, but the connection point of the transmission line 41 and the quarter-wave open stub 42 is not a short-circuit point, since the impedance Z _A in anticipation of the resistor 43 side by the transmission line 46 can be sufficiently high The signal hardly flows through the resistor 43, and the loss is small. Therefore, it is possible to obtain the upper limit frequency _{F H,} the better the amplifier even the NF at the lower limit frequency _{F L.}

  Similarly, when the circuit shown in FIG. 1 is actually manufactured, an amplifier with good NF is obtained even if a complete short-circuit point cannot be obtained at the connection point between the transmission line 41 and the quarter-wave open stub 42 due to physical restrictions. be able to.

  As can be seen from FIG. 2, the amplifier (solid line) of the present invention has a better NF in a wide band than the conventional amplifier (broken line).

Embodiment 2. FIG.
A microwave amplifier according to Embodiment 2 of the present invention will be described with reference to FIG. FIG. 3 is a diagram showing a circuit configuration of the microwave amplifier according to the second embodiment of the present invention.

  In FIG. 3, the bias circuit 4 is provided with a radial stub 47 instead of the quarter-wave open stub 42.

  By using the radial stub 47, a short-circuit point can be formed in a wide band at the connection point between the radial stub 47 and the transmission line 41. The operation and action of the microwave amplifier according to the second embodiment are the same as those of the first embodiment.

Embodiment 3 FIG.
A microwave amplifier according to Embodiment 3 of the present invention will be described with reference to FIG. FIG. 4 is a diagram showing a circuit configuration of a microwave amplifier according to the third embodiment of the present invention.

  In FIG. 4, the bias circuit 4 is provided with a capacitor (second capacitor) 48 instead of the quarter wavelength open stub 42.

The value of the capacitor 48 is determined so as to be short-circuited at the center frequency F _C. By using the capacitor 48 instead of the quarter-wave open stub 42, a short-circuit point is created at the connection point between the capacitor 48 and the transmission line 41. The operation and action of the microwave amplifier according to the third embodiment are the same as those in the first embodiment.

It is a figure which shows the circuit structure of the microwave amplifier which concerns on Embodiment 1 of this invention. It is a figure which shows the frequency characteristic of the minimum noise figure (NFmin) of the microwave amplifier which concerns on Embodiment 1 of this invention, and the conventional microwave amplifier. It is a figure which shows the circuit structure of the microwave amplifier which concerns on Embodiment 2 of this invention. It is a figure which shows the circuit structure of the microwave amplifier which concerns on Embodiment 3 of this invention. It is a figure which shows the structure of the conventional microwave amplifier.

Explanation of symbols

  1 field effect transistor, 2 input terminals, 3 output terminals, 4 bias circuit, 41 1/4 wavelength transmission line, 42 1/4 wavelength open stub, 43 resistor, 44 capacitor, 45 bias power supply terminal, 46 1/4 wavelength transmission Line, 47 radial stub, 48 capacitors.

Claims (3)

Is connected to the input terminal to the gate, is connected to the output terminal to the drain, and a source and a field effect transistor which is grounded, the microwave amplifier and a bias circuit connected to said gate,
The bias circuit includes:
A first transmission line having one end connected to the gate and having a wavelength of 1/16 wavelength or more and ¼ wavelength or less ;
1/4 wavelength open stub having one end connected to the other end of the first heat transmission line,
A resistor having one end connected to the other end of the first heat transmission line,
A second transmission line of 1/16 wavelength or more and 1/4 wavelength or less connected at one end to the other end of the resistor;
One end to the other end of the second heat transmission line is connected, the first capacitor whose other end is grounded,
A microwave amplifier, comprising: a bias power supply terminal for applying a bias, connected to a connection point between the other end of the second transmission line and one end of the first capacitor . The bias circuit includes:
Wherein instead of the quarter-wave open stub, a microwave amplifier according to claim 1, characterized in that it comprises a radial stub end to the other end of the first heat transmission line is connected. The bias circuit includes:
Wherein instead of the quarter-wave open stub, the one end to the other end of the first heat transmission line is connected, the micro according to claim 1, wherein the other end, characterized in that it comprises a second capacitor which is grounded Wave amplifier.

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