JPH0124442B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a mixer circuit that uses a high frequency signal as a received signal and that outputs an intermediate frequency signal that is a frequency component of the difference between the high frequency signal and a local oscillation signal, and in particular, This invention relates to a mixer circuit using a microwave integrated circuit (MIC) whose basic configuration is a strip line or microstrip line.

Conventional configuration and its problems Figure 1 shows a configuration example of a conventional MIC mixer circuit using a mixer diode as a frequency mixing element. Here, the high frequency signal input from the high frequency signal input terminal 1 propagates through the main line 2 and is applied to the mixer diode 3. The local oscillation signal inputted from the terminal 4 is coupled to the main line 2 at high frequency, passes through the local oscillation band-pass filter 5 that selectively passes only the local oscillation signal, and is applied to the mixer diode 3. Reference numeral 6 denotes a low-pass filter, which takes out intermediate frequency signals and at the same time short-circuits terminal A of mixer diode 3 at high frequencies for high frequency signals and local oscillation signals. 7 is an intermediate frequency signal output terminal from which an intermediate frequency signal generated by the mixer diode 3 is taken out. Reference numeral 8 denotes an image rejection filter that exhibits a pass characteristic for high frequency signals but suppresses image signals, and is composed of a plurality of open-ended stubs. 9 is an intermediate frequency signal blocking circuit that exhibits a pass characteristic for high frequency signals but exhibits an open impedance for intermediate frequency signals, in which two open terminated strip lines pass high frequency signals from the open ends of the open terminated strip lines. It consists of a 1/4 wavelength line-coupled interdigital DC blocking circuit distributed over a length of approximately 1/4 wavelength (1/4λ _s ), and terminal B of mixer diode 3 is short-circuited at high frequency by an intermediate frequency signal. As shown, the distance between the mixer diode 3 and the intermediate frequency signal blocking circuit 9 is approximately 1/4 of the intermediate frequency signal.
The length is chosen to be the wavelength (1/4λ _if ).

In the conventional configuration example shown in FIG. 1, the intermediate frequency signal blocking circuit 9 is placed on the input side of the image blocking filter 8, so the distance between the mixer diode 3 and the intermediate frequency signal blocking circuit 9 is equal to the distance between the image blocking circuit 9 and the image blocking circuit 9. The distance cannot be made shorter than the distance between the input end of the filter 8 and the mixer diode 3. Therefore, the frequency range of the intermediate frequency of the mixer circuit is limited so that the distance between the input end of the image rejection filter 8 and the mixer diode 3 must be set higher than the frequency corresponding to 1/4 wavelength. This not only limits the selection of the intermediate frequency, but also imposes restrictions on the installation position, configuration, and dimensions of the image rejection filter 8 in a mixer circuit in which the intermediate frequency is determined.

Furthermore, if an attempt is made to increase the number of stubs constituting the image blocking filter 8 in order to improve the filter characteristics, the dimensions of the image blocking filter 8 will become longer, and the usable range of intermediate frequencies will be increasingly restricted to a lower direction. It had some flaws.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a mixer circuit that can eliminate restrictions on the use range of intermediate frequencies, that is, restrictions on the installation position, configuration, and dimensions of the image rejection filter.

Structure of the Invention In the present invention, the distance between the plurality of stubs or the plurality of resonators coupled to the main line and forming the image rejection filter is approximately 1/4 wavelength (1/4λ _s ) or more of the high frequency signal. Taking advantage of the fact that the 1/4 wavelength line-coupled interdigital DC blocking circuit has a broadband pass characteristic, the 1/4 wavelength line-coupled interdigital DC blocking circuit is configured as an image blocking filter. The distance between the mixer diode and the 1/4 wavelength line-coupled interdigital DC blocking circuit, which is an intermediate frequency signal blocking circuit, is set between the stubs to be used or between the resonators, and the distance between the mixer diode and the 1/4 wavelength line-coupled interdigital DC blocking circuit, which is an intermediate frequency signal blocking circuit, is determined by the intermediate frequency usage range and the installation of an image blocking filter. This allows for free selection without being restricted by position, configuration, or dimensions.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows an embodiment of the present invention. Here, the same parts as in FIG. 1 are given the same numbers and explained.
A high frequency signal input from the high frequency signal input terminal 1 propagates through the main line 2 and is applied to the mixer diode 3. The local oscillation signal inputted from the terminal 4 is coupled to the main line 2 at high frequency, passes through a local oscillation bandpass filter 5 that selectively passes only the local oscillation signal, and is applied to the mixer diode 3. Reference numeral 6 denotes a low-pass filter which takes out the intermediate frequency signal and at the same time short-circuits the terminal A of the mixer diode 3 in terms of high frequency for high frequency signals and local oscillation signals. 7 is an intermediate frequency signal output terminal from which an intermediate frequency signal generated by the mixer diode 3 is taken out. 8
is an image rejection filter that exhibits a pass characteristic for high frequency signals but suppresses image signals, and is composed of a plurality of open-ended stubs. 9 is an intermediate frequency signal blocking circuit that exhibits a pass characteristic for high frequency signals but exhibits an open impedance for intermediate frequency signals, in which two open-ended strip lines pass through the high frequency signal from the open end of the open terminated strip line. It is composed of a 1/4 wavelength line-coupled interdigital DC blocking circuit that is distributed and coupled over a length of approximately 1/4 wavelength (1/4λ _s ), and is connected to the main line 2 between the open-terminated stubs that constitute the image blocking filter 8. It is set in. Furthermore, the distance between the mixer diode 3 and the intermediate frequency signal blocking circuit 9 is approximately 1/4 wavelength (1/4λ _if ) of the intermediate frequency signal so that the terminal B of the mixer diode 3 is short-circuited at the intermediate frequency. chosen for its length. In addition, the above mixer diode 3
Even if the distance between the intermediate frequency signal blocking circuit 9 and the intermediate frequency signal blocking circuit 9 is set to an odd number multiple of a quarter wavelength of the intermediate frequency signal, the same operation as described above will be obtained in terms of high frequency.

In this embodiment, the selection of the distance from the mixer diode 3 of the intermediate frequency signal blocking circuit 9 is not limited by the presence of the image blocking filter 8, and the mixer circuit can be constructed even under conditions of high frequency use as an intermediate frequency. . In addition, independent of the dimensions and installation position of the image blocking filter 8, the distance between the mixer diode 3 and the intermediate frequency signal blocking circuit 9 is adjusted to correspond to the usage range of the intermediate frequency, and is set to approximately 1/4 wavelength of the intermediate frequency signal (λ _if ), the dimensions of the image blocking filter 8, the installation position of the image blocking filter 8, and the intermediate frequency
The two conditions can be selected independently of each other, and
The frequency usage conditions for the intermediate frequency are not limited to the dimensions or installation position of the image blocking filter 8.
Moreover, the size of the mixer circuit can be definitely shortened by 1/4λ _s .

FIG. 3 shows another embodiment of the present invention, and the same parts as in FIG. 2 are given the same numbers and will be explained. 10 is an open-ended low-pass filter,
It is connected to the main line 2 on the mixer diode 3 side near the intermediate frequency signal blocking circuit 9, and the distance from the open end of the low-pass filter 10 to the mixer diode 3 is such that the terminal B of the mixer diode 3 is short-circuited with the intermediate frequency signal. Approximately 1/4 wavelength of the intermediate frequency signal (
The length is chosen to be 1/4λ _if ). Other than that, the second
It has the same configuration as the figure.

The embodiment shown in FIG. 3 is particularly effective under frequency conditions where the length of the 1/4 wavelength (1/4λ _if ) of the intermediate frequency is slightly longer than the distance from the input end of the image rejection filter 8 to the mixer diode 3. can be,
In FIG. 1, the intermediate frequency signal blocking circuit 9, which was provided on the main line 2 between the image blocking filter 8 and the high frequency signal input terminal 1, is now provided inside the image blocking filter 8, so the size of the mixer circuit is reduced. At the same time, this has the effect of improving the performance of the mixer circuit by reducing the propagation loss of high frequency signals through the main line 2.

FIG. 4 shows yet another embodiment of the present invention, in which the same parts as in FIG. 2 are given the same numbers and will be described. Reference numeral 11 denotes an image rejection filter, which is constructed by connecting 1/2 wavelength strip line resonators 12 and 12' that resonate at the image frequency in parallel to the main line 2 over a 1/4 wavelength length, and the strip line resonator 12 and 12' are approximately 1/2 wavelength (1/2
They are arranged at intervals of λ _n ; λ _n is the wavelength of the image frequency). Reference numeral 9 denotes an intermediate frequency signal blocking circuit composed of a 1/4 wavelength line-coupled interdigital DC blocking circuit, which is provided on the main line 2 between the 1/2 wavelength stripline resonators 12 and 12', and mixer diode 3. The mixer diode 3 is provided at a position approximately 1/4 wavelength (1/4 wavelength λ _if ) away from the mixer diode 3 in order to short-circuit the terminal B at the intermediate frequency in a high frequency manner. Other than that, the configuration is exactly the same as in FIG. Note that, as in the embodiment shown in FIG. 2, the distance between the mixer diode 3 and the intermediate frequency signal blocking circuit 9 may be set to an odd number multiple of 1/4 wavelength of the intermediate frequency signal.

In the embodiment shown in FIG. 4, as in the embodiment shown in FIG. 2, the selection of the intermediate frequency, the installation position of the image blocking filter 11, and the dimensions of the image blocking filter can be determined independently. becomes easier. Also, the size of the mixer circuit can definitely be shortened by 1/4λ _s .

Effect of the invention According to the present invention, the following effects can be obtained.

(1) A mixer circuit can be easily configured even under conditions of use of a higher intermediate frequency than conventional ones.

(2) Since there are no restrictions on the installation position and dimensions of the image blocking filter, the design of the image blocking filter becomes easier.

(3) The size of the mixer circuit can be shortened by 1/4λ _s , and the performance of the mixer circuit is improved by reducing the propagation loss of high-frequency signals.

(4) Since the intermediate frequency can be selected almost independently of the design of the image rejection filter, the range of usage conditions for the intermediate frequency of the mixer circuit is widened.

[Brief explanation of drawings]

FIG. 1 is a pattern diagram of a conventional mixer circuit using an MIC, and FIGS. 2, 3, and 4 are pattern diagrams of mixer circuits according to other embodiments of the present invention, respectively. 1...High frequency signal input terminal, 2...Main line, 3
...Mixer diode, 4...Terminal, 5...Band pass filter, 6...Low pass filter, 7...
Intermediate frequency signal output terminal, 8... Image blocking filter, 9... Intermediate frequency signal blocking circuit, 10... Low pass filter.

Claims (1)

[Scope of Claims] 1. A main line connecting a high frequency signal input terminal and one end of a frequency mixing element to transmit a high frequency signal to the frequency mixing element, and means for applying a local oscillation signal to the frequency mixing element; a filter that is connected to the other end of the frequency mixing element and extracts an intermediate frequency signal that is a frequency component of the difference between the high frequency signal and the local oscillation signal; An intermediate frequency signal blocking circuit exhibiting an open impedance for frequency signals, and means for short-circuiting one end of the frequency mixing element to ground in a high frequency manner with an intermediate frequency signal, and straddling the intermediate frequency signal blocking circuit. A mixer circuit characterized in that an image signal blocking filter is provided on the main line. 2. The mixer circuit according to claim 1, wherein the distance from the intermediate frequency signal blocking circuit to the frequency mixing element is set to a length of 1/4 wavelength of the intermediate frequency signal. 3 The image signal blocking filter is composed of a plurality of open-ended stubs having a line length of approximately 1/4 wavelength of the image frequency, and the intermediate frequency signal blocking circuit is composed of a 1/4 wavelength line-coupled interdigital DC blocking circuit. A mixer circuit according to claim 1, characterized in that: 4. The image signal blocking filter is constructed by connecting a plurality of 1/2 wavelength strip line resonators that resonate at the image frequency in parallel to the main line over a 1/4 wavelength length, and the above 1/2 wavelength strip line resonator at least about 1/2 of the image frequency
2. The mixer circuit according to claim 1, wherein the intermediate frequency signal blocking circuit is constructed of a 1/4 wavelength line-coupled interdigital DC blocking circuit arranged at intervals equal to the length of a wavelength. 5 A main line that connects a high frequency signal input terminal and one end of the frequency mixing element to transmit a high frequency signal to the frequency mixing element, means for applying a local oscillation signal to the frequency mixing element, and other parts of the frequency mixing element. A filter is connected to the end and takes out an intermediate frequency signal which is the frequency component of the difference between the high frequency signal and the local oscillation signal, and a filter is provided on the main line and exhibits a pass characteristic for high frequency signals but not for intermediate frequency signals. an intermediate frequency signal blocking circuit exhibiting open impedance; and means for short-circuiting one end of the frequency mixing element to ground in a high frequency manner with an intermediate frequency signal; A low-pass filter with an open end is connected to the main line on the frequency mixing element side, provided on the main line and near the intermediate frequency signal blocking circuit, and the distance from the open end of this low-pass filter to the frequency mixing element is A mixer circuit characterized in that the length of the intermediate frequency signal is 1/4 of the wavelength of the intermediate frequency signal. 6 The image signal blocking filter is composed of a plurality of open-ended stubs having a line length of about 1/4 wavelength of the image frequency, and the intermediate frequency signal blocking circuit is composed of a 1/4 wavelength line-coupled interdigital DC blocking circuit. The mixer circuit according to claim 5, characterized in that: