JPS6130764B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a double-balanced mixer equipped with a MIC (microwave integrated circuit), which can be used to mix a high frequency signal and a local oscillation frequency to extract an intermediate frequency. .

The one shown in Figure 1 is known as a conventional MIC double-balanced mixer. Here, the dotted line line is a slot line formed by a groove formed in the ground conductor provided on the back side of the dielectric substrate, and the solid line line is a slot line formed by a groove formed in the ground conductor provided on the front side of the dielectric substrate. The black box, which is a lip line and is designated by the reference number 10, is a 180° hybrid circuit based on MIC-based Magic T.

In the double-balanced mixer shown in FIG. 1, the signal frequency and local frequency are applied to ports 1 and 2, respectively, and after being combined in magic T10, the signals are applied to mixer diode 6 through distribution slot lines 7 and 8, and then The frequencies pass through the slot line 5, are converted to the microstrip line 9 by the short-circuit conductor 11 connecting the front side and the back side, are combined, and are taken out to the output port.

In this way, the slot line 5 and the microstrip line 9 are coupled by the shorting conductor 11, and the hole of the shorting conductor is located at a position approximately 1/4 wavelength from the mixer diode 6. Figure 3 is a detailed diagram of the short-circuit conductor 11, where 20 is a dielectric substrate, 2
1 is a ground conductor, and microstrip line 9
and a conductor 21 constituting the slot line 5 are short-circuited by a short-circuit conductor 11. If the position of the hole in the shorting conductor is slightly shifted, the isolation between ports 1 and 2 and the isolation from ports 1 and 2 to port 4 will deteriorate, and the frequency will increase, causing the line of the slot line 5 to deteriorate. As the length becomes shorter, it becomes more difficult to manufacture the shorting conductor 11 with high precision.

Therefore, with this circuit configuration, it is difficult to increase the frequency of the MIC mixer.

Therefore, an object of the present invention is to provide a MIC double-balanced mixer that improves the above-mentioned drawbacks of the conventional technology, and combines high-frequency signals inputted from two first input/output ports, and combines high-frequency signals inputted from two first input/output ports. a hybrid circuit that outputs to the second input/output port;
A pair of slot lines that have one end connected to the input/output port of the slot line, a pair of coplanar lines that share a common ground conductor with the slot line that is connected to the other end of these slot lines, and the center conductor of these coplanar lines. and an output section consisting of one coplanar line, and two diodes of the same polarity are connected from the center conductor of the coplanar line to the ground conductor at the joint part of one slot line and the coplanar line, and the other slot line is connected to the ground conductor. At the joint between the line and the coplanar line, two diodes of the same polarity are connected from the center conductor of the coplanar line to the ground conductor so that the polarity is opposite to that of the two diodes,
This MIC double-balanced mixer outputs an intermediate frequency signal from the output section by short-circuiting a pair of coplanar lines and a diode line using a shorting wire at a location approximately one-quarter wavelength away from the diode position. Examples will be described below with reference to the drawings.

FIG. 2 shows an example of the configuration of a double-balanced mixer according to the present invention, in which the dotted line line is a slot line formed by a groove formed in a ground conductor provided on the back side of a dielectric substrate, and the solid line conductor is a slot line formed by a groove formed in a ground conductor provided on the back side of a dielectric substrate. This figure shows a microstrip line formed by a conductor placed opposite a ground conductor on the front side of the board. Reference numeral 10 is a 180° hybrid circuit made of Magic T MIC. In Figure 2, 1, 2 and 4 are input/output ports, 3 is a microstrip line,
6 is a mixer diode, 7 and 8 are slot lines,
12 and 14 are coplanar lines, and 13 is a shorting piece made of gold wire or gold ribbon for connecting between the ground conductors of the coplanar lines. A coplanar line is a line in which the central conductor of a pair of slot lines placed close to each other is the center conductor, and the conductors at both ends are ground conductors.

High frequency input from ports 1 and 2 is Magic T1
After being combined with 0, it is applied to mixer diode 6 through slot lines 7 and 8. Since the output phases of the slot line 7 and the slot line 8 are shifted by 180 degrees, the two sets of mixer diodes 6 are also provided with opposite polarities. As a result, the intermediate frequency signal passes through the coplanar line 14 to the coplanar line 12.
The signals are added in phase and taken out from the intermediate frequency output port 4. That is, when the mixer diodes 6 are connected with the polarity shown in FIG. 2, the local oscillation voltage applied to each mixer diode 6 is V _LO cosω _LO t, and the received high frequency signal voltage is V _RF
If cosω _RF t, four mixer diodes 6
The current i(t) that is mixed due to the nonlinearity of , in-phase combined in the coplanar line 12, and taken out to the output port 4 is as follows, assuming that the local oscillation signal is sufficiently larger than the high frequency signal.

i(t)=4αi _S V _RF I ₁ (αV _LO cos(ω _Lp −ω _RF )t}+4αi _S V _RF I ₁ (αV _LO )cos
{(α _LO ) cos {(ω _LO +ω _RF )t}+4αi _S V _RF I ₃ (αV _LO ) cos {(3ω _LO +ω _RF )t}+... Here, i _S is the reverse saturation current of the mixer diode 6 , α is the nonlinear coefficient of current and voltage of the mixer diode 6 (expressed as i=i _S {e×p(αV)−1}), and Im is the modified Bessel function of the first kind and mth order. be. Therefore, the desired intermediate frequency component 4αi _S V _RF I ₁ (αV _L
O ) cos {(ω _LO −ω _RF )t} is retrieved. The shorting conductor 13 is used to combine the coplanar lines 14 in parallel, and also provides short-circuiting conditions for the high frequency signals branched at the slot series branching section, making the coplanar line 14 approximately one-quarter wavelength. This gives an open condition at high frequencies to the impedance seen on the intermediate frequency side from the mixer diode. As a result, the high frequency signal and local oscillation signal that should pass through the mixer diode 6 do not appear at the output port 4. The production of circuits using such gold wires and the like can be realized with higher precision than conventional drilling, etc., and it is also possible to design circuits that eliminate the influence of the gold wires and the like.
For example, since the wire becomes an inductance, the line length of the coplanar line 14 can be determined by taking this into consideration.

As described above, by using a coplanar line using a short-circuited conductor such as a wire, the conventional drilling process is unnecessary, and a double-balanced mixer with excellent characteristics in a high frequency band can be obtained.

FIG. 4 is a detailed view of the shorting piece 13, in which 20 is a dielectric substrate, 21 is a grounding conductor provided on the back side, 14 is a coplanar line formed by making a groove in the grounding conductor, and 13 is a coplanar line. It is a short-circuiting piece that short-circuits the conductors at both ends of the .

As explained above, the MIC double-balanced mixer of the present invention eliminates the intermediate frequency synthesis circuit using drilling and newly configures the intermediate frequency synthesis circuit with a coplanar line using a shorting piece such as a wire. There is an advantage that a mixer with excellent characteristics can be obtained in a higher frequency band.

[Brief explanation of the drawing]

Figure 1 shows an example of the configuration of a conventional MIC double-balanced mixer, and Figure 2 shows an MIC according to the present invention.
FIG. 3 is a detailed view of the shorting conductor portion in FIG. 1, and FIG. 4 is a detailed view of the shorting piece portion in FIG. 2. 1, 2, 4; input/output port, 3, 9; microstrip line, 5, 7, 8; slot line,
6; mixer diode, 10; MIC magic T, 11; shorting conductor (eyelet), 12, 14; coplanar line, 13; shorting piece (wire).

Claims (1)

[Claims] 1. A hybrid circuit that combines high-frequency signals input from two first input/output ports and outputs the synthesized signal to two other second input/output ports, and a pair of slots with one end connected to the second input/output ports. railroad tracks and
It has a pair of coplanar lines which are connected to the other ends of these slot lines and have a common ground conductor with the slot image path, and an output section which combines the center conductors of these coplanar lines to form one coplanar line. At the joint between the slot line and the coplanar line, two diodes of the same polarity are connected from the center conductor of the coplanar line to the ground conductor, and at the joint between the other slot line and the coplanar line, two diodes are connected from the center conductor of the coplanar line to the ground conductor. Two diodes of the same polarity are connected to the ground conductor so that the polarity is opposite to that of the two diodes, and the pair of coplanar lines is connected approximately 44 degrees from the position of the diodes.
1. A MIC double-balanced mixer, characterized in that an intermediate frequency signal is output from the output section by short-circuiting using a short-circuit wire at a portion separated by one-tenth of a wavelength.