JPH11127034A - Single-balanced mixer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need to constitute a DC return choke specially and to make the single-balanced mixer small-sized by composing an RF matching circuit of short stubs and microstrip lines. SOLUTION: The RF matching circuit 5 is composed of the short stubs 55 and 57 and microstrip lines 52 and 54 and then functions as a matching circuit, which becomes equivalent to the DC connections of diodes 6a and 6b with the ground, so that this circuit functions as a return circuit for a current generated when the diodes 6a and 6b operate. The short stubs 55 and 57 are part of the RF matching circuit 5 and exerts no adverse high-frequency influence on the circuit. Therefore, the RF matching circuit 5 consisting of the short stubs 55 and 57 and microstrip lines 52 and 54 has the same function with a DC return choke 9, which need not be constituted. Consequently, the single- balanced mixer is made small-sized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single balanced mixer used in a microwave band, and more particularly to a single balanced mixer composed of diodes.

[0002]

2. Description of the Related Art Single balanced mixers composed of diodes are well known in the art. FIG. 3 shows an example of a conventional single-balanced mixer used in the microwave band.

In the conventional single balanced mixer shown in FIG. 3, a first port is an RF port 1 to which a radio frequency signal (RF signal) is supplied, and a second port is an LO port to which a local oscillation output is supplied. The third port is a port 3a, 3b for an intermediate frequency signal for transmitting a composite signal output of the input RF signal and the input local oscillation output, and the third port is input from the RF port 1 and the LO port 2. A hybrid circuit 4 that divides the divided power into two at a phase difference of 90 ° or 180 ° and outputs the divided power from ports 3a and 3b for intermediate frequency signals, and an open stub 51 supplied with an output from port 3a for intermediate frequency signals. Microstrip line 5
2 and a port 3 for an intermediate frequency signal
b, and a matching circuit composed of an open stub 53 and a microstrip line 54 to which an output from the b is supplied, and a hybrid circuit 4 and diodes 6a and 6b described later.
An RF matching circuit 5a for impedance matching between the diodes, diodes 6a and 6b for frequency conversion, a capacitance 8 for short-circuiting a signal in an RF band transmitted from a cathode of the diode 6a and an anode of the diode 6b to the ground, An IF matching circuit 7 for impedance matching between the diodes 6a and 6b and the capacitance 8 and the IF port 3, and diodes 6a and 6b
(Hereinafter, the diode operates) means that when signals of two different frequencies are input to the diodes, the frequency is converted by the nonlinear characteristics of the diodes 6a and 6b, and the difference between the sum and the difference of the frequencies of the input signals is mainly determined. A DC return choke 9 which functions as a return circuit for the current generated when the current having a frequency component is generated (connects the diodes 6a and 6b to the ground in a DC manner).
It is composed of

[0004] The DC return choke 9 includes a diode 6
The purpose is to connect a and 6b to the ground in a DC manner. If the circuit is not affected at high frequencies, it may be connected to any part on the circuit of the single balanced mixer. To avoid affecting the signal,
Connected to LO port 2 with large amplitude.

If the wavelength of the RF signal is degenerated by the dielectric constant of the dielectric substrate on which the single-balanced mixer is formed and the width and length of the microstrip line, that is, the guide wavelength for the so-called RF signal is λg. ,
The capacitance 8 can be replaced by an open stub having a length λg / 4 or a radial stub having a radius λg / 4.

When a signal of frequency f1 is input to RF port 1 and a signal of frequency f2 is input to LO port 2,
The frequency is converted by the nonlinear characteristics of the diodes 6a and 6b, and a signal having a frequency | f1-f2 | is mainly output to the IF port 3. On the other hand, when the signal of the frequency f2 is input to the LO port 2 and the signal of the frequency f3 is input to the IF port 3, the frequency is converted by the nonlinear characteristics of the diodes 6a and 6b, and the frequency f2 + f3,
And a signal of frequency f2-f3 is output.

[0007]

In the conventional single-balanced mixer as described above, the open stub is different from the designed position when the position of the through hole and the length of the microstrip line are different from the design position like the short stub. Since there is no need to analyze the shift of the phase, that is, the phase shift due to the so-called via hole, the RF matching circuit is configured by the open stub and the microstrip line.

However, in the case of the above-described conventional single-balanced mixer configuration, if there is no DC return choke, both ends of the diode used in the single-balanced mixer become DC open and the diode does not operate. However, there is a problem that frequency conversion, which is a basic function, cannot be performed.

Therefore, there is a problem that a DC return choke is required separately, which is not suitable for downsizing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a miniaturized single-balanced mixer that does not require a DC return choke conventionally required.

[0011]

SUMMARY OF THE INVENTION A single balanced mixer according to the present invention comprises an RF port to which a radio frequency signal is supplied, an LO port to which a local oscillation output is supplied, and an input radio frequency signal. A hybrid circuit having an intermediate frequency signal port for transmitting a composite signal output with the generated local oscillation output, a diode for performing frequency conversion by receiving an output signal from the intermediate frequency signal port, a hybrid circuit and a diode An RF matching circuit for impedance matching between the diode, a capacitance for short-circuiting a radio frequency band signal transmitted from an output terminal of the diode to the ground, and an impedance matching between the diode, the capacitance, and the IF port. In a single balanced mixer composed of an IF matching circuit and an RF matching circuit, Characterized by being composed of a Yotosutabu and the microstrip line.

[0012] The single balanced mixer of the present invention has an R
Because the F matching circuit is composed of short stubs and microstrip lines, it functions as a matching circuit,
This is equivalent to connecting the diode to the ground by a short stub, and also functions as a return circuit for the current generated when the diode operates. The size of the balanced mixer can be reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a single balanced mixer according to the present invention will be described with reference to embodiments.

FIG. 1 is a circuit diagram showing a configuration of a single balanced mixer according to an embodiment of the present invention.

In the single balanced mixer according to one embodiment of the present invention shown in FIG. 1, the first port is an RF port 1 to which an RF signal is supplied, and the second port is supplied with a local oscillation output. The third port is an intermediate frequency signal port 3a, 3b for transmitting a composite signal output of the input RF signal and the input local oscillation output.
A hybrid circuit 4 that divides the power input from the RF port 1 and the LO port 2 into two at a phase difference of 90 ° or 180 ° and outputs the power from the intermediate frequency signal ports 3a and 3b; A matching circuit 151 including a short stub 55 and a microstrip line 52 for impedance matching between the output terminal of the diode 3a and the diode 6a, and impedance matching between the diode 6b and the output terminal of the intermediate frequency signal port 3b. An RF matching circuit 5 configured by a matching circuit 152 including a short stub 57 and a microstrip line 54 for performing impedance matching between the hybrid circuit 4 and the diodes 6a and 6b, and a hybrid circuit via the matching circuit 5 4. Frequency conversion of output from ports 3a and 3b for intermediate frequency signal A diode 6a and 6b to perform,
A capacitance 8 for short-circuiting an RF band signal transmitted from the cathode of the diode 6a and the anode of the diode 6b to the ground, and diodes 6a, 6
b and an IF matching circuit 7 for impedance matching between the capacitance 8 and the IF port 3.

As described above, the single balanced mixer according to the embodiment of the present invention shown in FIG. 1 has the open stub 51, the microstrip line 52, and the open stub in the conventional single balanced mixer shown in FIG. R consisting of 53 and microstrip line 54
Instead of the F matching circuit 5a, an RF matching circuit 5 including a matching circuit 151 including a short stub 55 and a microstrip line 52 and a matching circuit 152 including a short stub 57 and a microstrip line 54 are used.

Here, assuming that the guide wavelength in the RF signal is λg, the capacitance 8 can be replaced by an open stub having a length λg / 4 or a radial stub having a radius λg / 4.

As described above, the RF matching circuit 5 is connected to the short stubs 55 and 57 and the microstrip lines 52 and 54.
And functions as a matching circuit, and at the same time, is equivalent to connecting the diodes 6a and 6b to the ground in a DC manner, and also functions as a return circuit of a current generated when the diodes 6a and 6b operate. I do. The DC return choke must not affect the circuit at high frequencies, but the short stubs 55 and 57
Needless to say, it is a part of the F matching circuit 5 and does not adversely affect the circuit at high frequencies.

Therefore, the RF matching circuit 5 composed of the short stubs 55 and 57 and the microstrip lines 52 and 54 has the same function as the DC return choke 9 and does not need to configure the DC return choke 9. Disappears.

As a result, the size of the single balanced mixer according to one embodiment of the present invention is reduced.

Further, by making adjustments in the design stage based on simulations or the like, phase shift due to via holes can be eliminated.

Next, a specific configuration of the single balanced mixer according to one embodiment of the present invention will be described.

FIG. 2 is a circuit diagram showing a specific configuration of a single balanced mixer according to an embodiment of the present invention. As the hybrid circuit 4, a 180 ° hybrid circuit 4a is used, and as the capacitance 8, a radius λg /
No. 4 radial stub 8a is used.

In the single balanced mixer having the specific configuration according to the embodiment of the present invention, the RF matching circuit 5 has the same function as the DC return choke 9, and the DC return choke 9 needs to be configured. Is eliminated, and the size of the single balanced mixer is reduced.

[0025]

As described above, the single balanced mixer according to the present invention comprises an RF matching circuit comprising a short stub and a microstrip line.
Since the RF matching circuit also functions as a DC return choke, there is no need to separately configure a DC return choke, and the effect of reducing the size of the single balanced mixer can be obtained.

Further, in designing a monolithic microwave IC circuit, an effect that the chip area can be reduced can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a single balanced mixer according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific configuration of a single balanced mixer according to one embodiment of the present invention.

FIG. 3 is a circuit diagram of a conventional single balanced mixer.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 RF port 2 LO port 3 IF port 4 Hybrid circuit 5 RF matching circuit 6a, 6b Diode 7 IF matching circuit 8 Capacitance 52, 54 Microstrip line 55, 57 Short stub 151, 152 ... Matching circuit

Claims (3)

[Claims] 1. A composite signal output of an RF port to which a radio frequency signal is supplied, an LO port to which a local oscillation output is supplied, and an input radio frequency signal and an input local oscillation output. A hybrid circuit having an intermediate frequency signal port, a diode that performs frequency conversion by receiving an output signal from the intermediate frequency signal port, and an RF matching circuit that performs impedance matching between the hybrid circuit and the diode; In a single balanced mixer composed of a capacitance for short-circuiting a signal in a radio frequency band transmitted from an output terminal of a diode to a ground, and an IF matching circuit for impedance matching between the diode, the capacitance, and an IF port. The RF matching circuit is composed of a short stub and a microstrip line. Single balanced mixer, characterized in that. 2. The single-balanced mixer according to claim 1, wherein the capacitance is constituted by a radial stub having a radius of λg / 4, where λg is the guide wavelength at the radio frequency. 3. The single-balanced mixer according to claim 1, wherein the capacitance is constituted by an open stub having a length of λg / 4, where λg is the guide wavelength at the radio frequency.