JPH07122913A - Reverse phase distribution circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a reverse phase distribution type circuit using a small slot line in a microwave band of about X band or less. [Structure] The conductors 7 and 8 and the common conductor 9 constitute slot lines 10, 11 and 12. Two outputs of opposite phases due to the phase difference between the drain 2 and the source 3 are connected to the conductors 7 and 8. The ground conductors 13 and 14 are connected to the common conductor 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is suitable for a monolithic microwave integrated circuit (MMIC) which is used at a relatively low frequency of microwaves, particularly about 10 GHz (X band) or less, which makes it difficult to miniaturize the circuit. The present invention relates to an improvement of an antiphase distribution circuit using slot lines.

[0002]

2. Description of the Related Art A negative phase distribution circuit is a very important and basic circuit having various applications in the microwave band.

FIG. 2 is a block diagram of a balanced mixer, which is one application example of the anti-phase distribution circuit. The carrier wave applied to the port 25 is distributed in anti-phase by the anti-phase distribution circuit 26 and is applied to the two field effect transistors (FETs) 29 and 30 through the combining circuits 27 and 28. Further, the intermediate frequency signal applied to the port 31 is also distributed in anti-phase by the anti-phase distribution circuit 32, is added to the carrier wave by the composition circuits 27 and 28, and is added to the FETs 29 and 30. The characteristic of the balanced mixer is that the output side of the element produces frequency components of the sum and difference of the carrier wave and the intermediate frequency due to the non-linearity of the FET, and the carrier wave component does not leak to the output terminal.

For this operation, accurate anti-phase distribution characteristics in the anti-phase distribution circuit are important. Hybrid coils are often used at frequencies as low as several tens of MHz, but in the microwave band, such hybrid coils cannot be used and are not suitable for IC construction. Also, in the microwave amplifier, the distribution characteristic of the differential amplifier suitable for IC is not exactly opposite phase in the microwave band due to the influence of the phase rotation due to the stray capacitance of the active element.

Therefore, in the microwave band, an antiphase distribution circuit using a microstrip line as shown in FIG. 3 is often used. This circuit is called a rat race type and is generated by a quarter wavelength line and a quarter wavelength line. When an input is given to the port 40, outputs whose phases are different by 180 ° are obtained from the ports 41 and 42.

FIG. 4 is a plan view of an example of an antiphase distribution circuit using a slot line. The conductors 45 and 46 are arranged to face each other, the conductor 47 is arranged to face the conductors 45 and 46, and the slot line 5 is arranged in the gap between the conductors.
0, 51, 52 are configured. When the input is applied to the slot line 50, the phase is changed from the slot lines 51 and 52 to 18
Outputs different by 0 ° are obtained. Since this circuit uses a series T-branch of a slot line, it can be accurately distributed by 180 ° and has a wide band, and various balanced circuits using this circuit have been proposed.

[0007]

The circuit shown in FIG.
It is often used because it can be easily configured. However, since it uses a quarter-wave line, it has a limited operating band, and has a large circuit size. It was virtually impossible to apply.

Further, in the circuit of FIG. 4, downsizing cannot be realized in the X band and below for the following reasons. In an actual circuit, there are other circuits in the periphery, and in consideration of connection with other circuits, the circuit needs to be surrounded by a so-called ground conductor. In the slot line,
Since the electric field is concentrated in the slot part and no electric field is generated in a place far away from the slot part, when the frequency of about 20 GHz or higher is very high, the conductor width to the connection point with the ground plane of the external circuit is It may be narrow, but it needs to be extremely wide at about 10 GHz or less.

FIG. 5 shows an example of a prototype pattern for experimentally examining how much the ground conductor width S should be made. The conductors 63, 60, 64 and 64, 61, 65 form the first and second coplanar lines, respectively, and the air bridges 70, 71 are ground conductors 63 and 64, respectively.
The common potential is used for 64 and 65 to ensure the operation as a coplanar line. The conductors 64 and 66 form the slot line 62. Further, the conductors 67 and 68 respectively connect the ground conductors 63 and 65 of the coplanar line and the conductor 66 forming the slot line. The signal input from the first coplanar line passes through the slot line via the mode conversion unit 72, and further, the mode conversion unit 73
Is output from the second coplanar line via. Conductor 6
In the absence of 7,68, the mode conversion is almost complete and the signal is transmitted with almost no attenuation. However, conductors 67, 6 for surrounding the periphery with a ground conductor
When 8 is present, the signal is attenuated. Mode converter 7
An experiment was conducted on the relationship between the transmission loss and the distance S from 2 (73) to the connecting conductor 67 (68).

FIG. 6 shows the measurement result. As shown in the figure, when the insertion loss due to the insertion of the distribution circuit is 3 dB or less, S is 3 GHz, 10 GhZ, 20 G.
In Hz, 0.8 mm, 0.5 mm,
It must be 0.3 mm or more. Therefore, it is necessary to take S sufficiently wide in the low frequency region.
It had the drawback that it could not be miniaturized.

The object of the present invention is to solve the above problems, and
An object of the present invention is to provide an antiphase distribution circuit using a small slot line in a relatively low microwave band below a band.

[0012]

Means for Solving the Problems Two outputs forming an input line of a series T-branch circuit of a slot line are connected to two outputs of an anti-phase distribution circuit composed of lumped constant elements, and a ground conductor of each circuit is connected. Connect to each other.

[0013]

According to the present invention, the insertion loss caused by reducing the width of the ground conductor of the slot line is compensated by the output of the anti-phase distribution circuit formed by the lumped element, and the deterioration amount of the anti-phase distribution characteristic by the latter is compensated. Can be suppressed by the anti-phase distribution circuit configured by the slot line that is the balanced line.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1A is a plan view of an embodiment of the present invention. FIG. 1B is an equivalent circuit diagram of FIG. F
The two outputs of the quasi-opposite phase distribution circuit using the phase difference between the drain and the source of ET are connected to the two conductors of the slot line, respectively, and the slot line is output with the antiphase T branch. Two conductors 7 and 8 arranged to face each other,
The slot line 10 is formed by the slots between the conductors 7 and 8 and between the conductors 7 and 8 and the common conductor 9 that are formed by the common conductor 9 that is arranged to face this and is grounded.
11 and 12 are formed. The negative phase distribution circuit is FET
It utilizes the phase difference between the drain and the source. The drain 2 is connected to the conductor 7, and the source 3 is connected to the conductor 8. The gate 1 is connected to a terminal 15 described later, the drain 2 and the source 3 are connected to ground conductors 13 and 14 via resistors 5 and 6, respectively, and the ground conductors 13 and 14 are connected to connection conductors 21 and 22. And is connected to the common conductor 9.

Reference numerals 15, 16 and 17 are input / output terminals formed by coplanar lines, and reference numerals 18, 19 and 20 are air bridges.

For simplicity, the output of the terminal 16 is the wave (amplitude a) transmitted by the output between the ground conductor 13 and the drain 2.
And a wave (amplitude b) by the reverse phase distribution of the slot line, that is, a combination of waves from the slot line 11, and assuming that the phase at the terminal 17 is the reference phase, the voltage V at the terminal 16 is expressed by the following equation. It is represented by.

[0017]

[Equation 1]

Here, Δθ indicates a deviation from 180 ° that occurs because it is a quasi-opposite phase distribution circuit.

From the equation (1), the output V is

[0020]

[Equation 2]

Here,

[0022]

[Equation 3]

Is the deviation from the reverse phase distribution characteristic. As a simple example, the deviation from the anti-phase distribution characteristic will be calculated for the following three cases.

(1) When a = 0, that is, when the connection conductors 21 and 22 are not provided without considering the connection with the external circuit as shown in the conventional example of FIG. 4, In this case, A = b.phi. = 0, and an ideal anti-phase distribution circuit is formed only by the slot line.

(2) When Δθ = 0, this corresponds to the case where the quasi-antiphase distribution circuit is an ideal distribution circuit, A = a + b φ = 0, and A is the sum of a and b.

(3) In the non-ideal case described above, for example, when a = b, that is, when the intensities of the waves from the respective paths are equal and Δθ exists, φ = Δθ / 2, and the quasi-antiphase distribution circuit. The phase error Δθ of is reduced by half.
Further miniaturization is possible by devising the pattern so that the value of a is as small as possible compared to b.

[0027]

As described above, according to the present invention, by combining the quasi-antiphase distribution circuit and the slot line, the phase error of the quasi-antiphase distribution circuit can be reduced and the X band which has been difficult in the past. It becomes possible to miniaturize the anti-phase distribution circuit of the slot line at the low frequency of the following microwaves.

[Brief description of drawings]

FIG. 1A is a plan view of an embodiment of the present invention,
(B) is the equivalent circuit diagram.

FIG. 2 is a block diagram of a conventional balanced mixer.

FIG. 3 is a plan view of a rat race type circuit.

FIG. 4 is a plan view of an example of a conventional slot line.

FIG. 5 is a pattern diagram for examining frequency characteristics of a slot line.

FIG. 6 is a graph of characteristics of a slot line according to a ground conductor width.

[Explanation of symbols]

 1 gate 2 drain 3 source 5,6 resistance 7,8 conductor 9 common conductor 10,11,12 slot line 13,14 ground conductor 15,16,17 terminal 18,19,20 air bridge 21,22 connection conductor

Claims (1)

[Claims] 1. An input line is formed in a gap between a first conductor pattern and a second conductor pattern, and is formed in a gap between a third common conductor pattern, the first conductor pattern and the second conductor pattern. The slot-line series T-branch circuit forming two output lines, the anti-phase distributor circuit formed of lumped constant elements, and the two outputs of the anti-phase distributor circuit are the input parts of the series T-branch circuit, respectively. A reverse phase comprising means for connecting to the first conductor pattern and the second conductor pattern, and means for connecting the ground conductor of the negative phase distribution circuit to the third common conductor pattern of the series T branch. Distribution circuit.