JPH03211902A - Mixer circuit for microwave - Google Patents

Abstract

PURPOSE:To facilitate the design of the constant for the input matching circuit with an extremely simple constitution while avoiding effect to a non-linear element and thereafter of an input matching circuit, by placing a filter for eliminating an intermediate frequency signal in a pre-stage of the non-linear element. CONSTITUTION:A filter 20 constituted as a distribution coupling circuit for passing a high frequency input signal 1 and a local oscillating signal 5 and eliminating an intermediate frequency signal to these signals is provided on a prestage of a non-linear element 4 for a fixer, so that an input side circuit can be regarded as a short circuit or almost a short-circuited load against the intermediate frequency signal, when looked from this non-linear element 4. In such a way, the filter 20 becomes a short circuit or a low impedance load against the intermediate frequency signal, the intermediate frequency signal is not transferred to an input matching circuit 12, and the design of the for constant the input matching circuit 12 and the filter 20 is facilitated extremely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a microwave mixer circuit used in the microwave band, such as a mixer circuit for a BS converter.

[Prior Art] Conventionally, a mixer circuit for a BS converter uses a nonlinear element such as a diode to obtain an intermediate frequency signal.

FIG. 5 shows a conventional example of a mixer circuit 10 using diodes.

In Fig. 5, 11°3~1 which is fully supplied to input terminal 1
High frequency No. 18 (microwave signal) of about 2.0 GHz is supplied to the first bandpass filter 3 via the input matching circuit 2.

This first band-pass filter 3 is a filter that blocks the passage of local oscillation signals (its frequency is 10.7 GHz) and image signals (its frequency is 9 to 10 GHz), and allows only high-frequency signals to pass. .

The high frequency signal that has passed through the first bandpass filter 3 is applied to a nonlinear element 4 using a diode.

Further, the local oscillation signal supplied to the input terminal 5 is supplied to the second band pass filter via the input matching circuit 6, and only the local oscillation signal is extracted.

The extracted local oscillation signal is applied to the above-mentioned nonlinear element 4 together with the high frequency signal.

Therefore, from this nonlinear element 4, the sum and difference (No. 8) of the high frequency signal and the local oscillation signal are obtained, and among these, the difference signal,
In other words, only the intermediate frequency signal can be shunted and output to the output terminal 9.
can be obtained.

When the mixer circuit 10 shown in FIG. 5 is constructed of microstrip lines, it becomes as shown in FIG. 7.

The input matching circuit 2.6 is composed of a microstrip line using an open-ended stub.

The bandpass filter 3.7 is composed of a 1/2 wavelength side-coupled filter using a microstrip line, and the output of the bandpass filter 3.7 is coupled by a short-circuited stub 11 at the tip.

The low-pass filter 8 is also composed of a microstrip line using an open-ended stub.

In the microphone n-wave layer mixer circuit 10 configured in this manner, as is clear from the configuration shown in FIG. 7, the electrical length when looking at the input side circuit from the input terminal a of the nonlinear element 4 is Since each input point of the pass filter 3.7 is reached, it becomes very long.

Therefore, with this configuration, although the input matching circuit 2.6 can be configured separately for high frequency signals and local oscillation signals, the input matching circuit 2.6 needs to match over a wide microwave band. This has drawbacks such as a complicated configuration of the input matching circuit 2.6.

The configuration shown in FIG. 6 solves this problem.

In the configuration shown in FIG. 6, instead of arranging the input matching circuit 2.6 at the input stage of the bandpass filter 3.7, the nonlinear element 4.
A common input matching circuit 12 is placed in front of the circuit.

FIG. 8 shows a specific example using a microstrip line.

According to this configuration, since the electrical length from the input connection point a of the nonlinear element 4 to the output terminal of the input matching circuit 12 is shortened, there is an advantage that wideband matching can be easily achieved.

[Problems to be Solved by the Invention] However, also in the mixer circuit 10 shown in FIG.
2a and an open-end stub 12b.

Therefore, the short-circuited stub 12a at the tip becomes L-type, and the open-ended stub 12b becomes C-type, so that the matching circuit 12 may act as a parallel resonant circuit for the intermediate frequency signal.

Then, when the input side circuit is viewed from the input side connection point a of the nonlinear element 4, there is a problem that it becomes a high impedance load for the intermediate frequency signal, making it difficult to configure the output side matching circuit. Were present.

Furthermore, there is a problem in that the design of the constants (resonance conditions) of the input matching circuit 12 becomes more difficult so that a parallel resonant circuit is not constructed for the intermediate frequency signal in the input side circuit.

Therefore, the present invention solves these conventional problems, and facilitates the design of the input matching circuit by preventing the input matching circuit 12 from acting as a parallel resonant circuit for intermediate frequency signals. be.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a distributed coupling circuit that passes high-frequency Jinkai No. 8 and local oscillation signals and blocks intermediate frequency signals for these signals. A filter configured as follows is installed before the mixer nonlinear element, and when the input side circuit is viewed from this nonlinear element, this input side circuit can be regarded as a short circuit or a load close to a short circuit with respect to intermediate frequency No. 48. It is characterized by the fact that

[Function 1] The filter 20 provided between the manual matching circuit 12 and the nonlinear element 4 is a band pass filter or a high pass filter that passes high frequency signals and local oscillation signals and blocks intermediate frequency signals. be done.

By providing such a filter 20 on the input side of the nonlinear element 4, the filter 20 becomes a short circuit or a low impedance load for intermediate frequency signals. Therefore, the design of the filter 20 and the design of the input matching circuit 12 provided before the filter 20 are facilitated.

[Example] Next, an example of a microwave mixer circuit according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the basic configuration of this invention, and this invention follows the circuit configuration shown in FIG. 6. In contrast to the configuration shown in FIG. 4, a filter 20 is provided between the two.

This filter 20 is a band pass filter or a high pass filter that passes the high frequency signal and the local oscillation signal and blocks the intermediate station'a signal.

When such a filter 20 is used, the filter 20 has a short circuit or low impedance characteristic for the intermediate frequency signal, and does not act as a parallel resonant circuit for the intermediate frequency signal No. 18.

Therefore, this intermediate station? The Il signal is not transmitted to the input matching circuit 12 side.

Therefore, constant design of the input matching circuit 12 and the filter 20 becomes very easy.

FIG. 2 shows a specific example of the invention.

In the figure, first and second bandpass filters 3.7
Both can be constructed from a 1/2 wavelength side-coupled filter of a microstrip line, and the input matching circuit 12 is constructed from a microstrip line using an open-ended stub.

The filter 20 includes an open-end stub 21 using a 1/4 wavelength distributed coupling line, and a short-circuiting stub 22 using a distributed coupling line for image frequency shorting.

Since the tip short-circuit stub 22 is for image frequency short-circuit, its length is set to 1.1 = 2 nλim. However, nλim is one wavelength of the image frequency, n
is a natural number.

With this configuration, when the input side circuit is viewed from the input side connection point a of the nonlinear element 4, its electrical length becomes extremely short. Furthermore, when looking at the input side circuit from the input side connection point a, the filter 20 is the only load on the intermediate frequency signal. If the signal is sufficiently small, the circuit can be easily constructed so that the filter 20 can be considered to be almost a short circuit with respect to the intermediate frequency signal.

FIG. 3 shows a second embodiment of the invention.

In this example, a bandpass filter is used as the filter 20, and can be configured with short-circuited stubs 23 and 22 using quarter-wavelength distributed coupling lines. The rest of the configuration is the same as that in FIG. 2.

FIG. 4 shows a third embodiment of the invention.

In this example, the first bandpass filter 3 is composed of a dielectric resonator 30 and microstrip lines 31 and 32 arranged to sandwich the dielectric resonator 30. Second
The bandpass filter 7 also has a dielectric resonance @M35 and a microstrip line 36.3 arranged to sandwich this.
7 is used.

Even if such a dielectric resonator is used, it can be configured as a filter that passes a predetermined No. 18 band.

The other configurations are the same as in FIG. 2.

Note that although a 1/4 wavelength distribution coupling line is used as the filter 20, it is also easy to use something other than this.

[Effects of the Invention] As explained above, according to the configuration of the present invention, an extremely simple configuration in which a filter for blocking an intermediate frequency signal is disposed before a nonlinear element, and a filter that blocks an intermediate frequency signal is provided after the nonlinear element of the input matching circuit. Since the influence can be reduced, there are practical benefits such as easier constant design of the input matching circuit.

In addition, the 1/4 wavelength distribution coupled line has the function of an impedance converter in addition to the function of a bandpass filter, and has a low characteristic impedance line that is difficult to construct with a single microstrip line in high frequency bands. can be configured. Therefore, since such an impedance conversion function can be utilized, the input matching circuit can be configured more easily.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an example of a microwave mixer circuit according to the present invention, Figs. 2 to 4 are microwave circuit diagrams showing specific examples thereof, and Figs. 5 and 6 are conventional microwave mixer circuits. FIGS. 7 and 8 are microwave circuit diagrams of the mixer circuit. 3, 7 ・ 4 ・ 8 ・ 12 ・ 20 ・ 21 ・ 22, 23 ・ 30, 35 ・ Bandpass filter, nonlinear element, low pass filter, input matching circuit, filter, open end stub, shorted end stub, dielectric body resonator

Claims (1)

[Claims] (1) A filter configured as a distributed coupling circuit that passes high frequency input signals and local oscillation signals and blocks intermediate frequency signals for these signals is provided in front of the mixer nonlinear element, and from this nonlinear element A microwave mixer circuit characterized in that when looking at an input side circuit, this input side circuit can be regarded as a short circuit or a load close to a short circuit with respect to an intermediate frequency signal.