JPS585011A - Mixing circuit - Google Patents

Abstract

PURPOSE:To exactly execute a short circuit even in case when frequency of an intermediate frequency signal is high, by providing an intermediate frequency signal obstructing circuit on a main line, also utilizing the line length of the main line, and short-circuiting a loading point of a mixer diode, as high frequency. CONSTITUTION:A high frequency signal inputted from a high frequency signal input terminal 1, and a local oscillating signal inputted from a local oscillating signal input terminal 2 are propagated through a main line 3 through intermediate frequency signal obstructing circuits 8, 10, respectively, are applied to a mixer diode 4, and an intermediate frequency signal is fetched from an intermediate frequency signal output terminal 6 through a low-pass filter 5. In the vicinity of the intermediate frequency signal obstructing circuits 8, 10 showing open- circuit impedance against the intermediate frequency signal, low-pass filters 9, 11 whose terminal has been open-circuited are connected in parallel to the main line 3, a distance between its open-circuit terminal and the mixer diode 4 is selected to 1/4 wavelength of the intermediate frequency signal, and a terminal B of the mixer diode 4 is short-circuited by the intermediate frequency signal, as high frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the realization of a method for connecting a diode loading point at an intermediate frequency signal frequency of a mixer circuit using a microwave integrated circuit having a strip line or a microstrip line as its basic structure, and particularly relates to a method for connecting a diode at an intermediate frequency signal frequency. This provides a method for shorting the diode loading point when the signal frequency is high.

In the conventional mixer circuit 3 using a microwave integrated circuit, a circuit as shown in FIG. 1 was used as a method of short-circuiting a diode loading point at an intermediate frequency signal frequency. In FIG. 1, a high frequency signal input from a high frequency signal input terminal 1 and a local oscillation signal input from a local oscillation signal input terminal 2 propagate through a main line 3 and are applied to a mixer diode 4. Reference numeral 6 denotes a low-pass filter that extracts an intermediate frequency signal, which is the same wave frequency component of the difference between the high frequency signal and the local oscillation signal, from the intermediate frequency signal output terminal 6, and at the same time outputs a mixer for the high frequency signal and the local oscillation signal.・Diode 4
The length provided to short-circuit the terminals in a high-frequency manner consists of an open-ended stub at the wavelength (2) of a high-frequency signal or a local oscillation signal, and a series inductance. 7 is an intermediate frequency signal shorting circuit for shorting the terminal B of the mixer diode 4 to the intermediate frequency signal, which connects the μ wavelength (7) line with high characteristic impedance and the wavelength-terminated open stub with low characteristic impedance. This is a low-pass filter consisting of a terminal short-circuited to ground.

In the conventional intermediate frequency signal shorting circuit 7 using a low-pass filter whose terminal end is short-circuited to ground, there was no problem when the intermediate frequency signal frequency was relatively low, but as the intermediate frequency signal frequency became higher, Therefore, the impedance of the intermediate frequency signal short circuit 7 can no longer be ignored, and it is no longer considered a short circuit. At this time, the impedance of the intermediate frequency signal short circuit 7 exhibits the characteristics of an interface circuit having a certain finite size. Since this intermediate frequency signal short circuit 7 is connected in series with the mixer diode 4 when viewed from the intermediate frequency signal output terminal 6, as the impedance of the intermediate frequency signal short circuit 7 increases,
The matching bandwidth from the intermediate frequency signal side is limited, which ultimately limits the bandwidth of the mixer circuit. At the same time, since the main line 3 is connected to the terminal B of the mixer diode 4, when the impedance of the intermediate frequency signal short circuit 7 increases, the main line 3
Depending on the state of the circuits connected to the high frequency signal input terminal 1 side and the local oscillation signal input terminal 2 side of ' The disadvantage was that the performance of the mixer circuit deteriorated due to a mismatch in the output impedance of the intermediate frequency signal.

In order to reduce the impedance of the intermediate frequency signal short circuit 7 in order to alleviate this drawback, the dimensions of the intermediate frequency signal short circuit 7 may be shortened, or the intermediate frequency signal short circuit 7 may be shortened in size.
One possible method is to widen the width of the strip line that makes up the line to lower the characteristic impedance of the line, but if the dimensions are shortened or the line width is widened, the intermediate frequency signal short circuit 7 will propagate through the main line 3. The influence on high frequency signals and local oscillation signals can no longer be ignored, resulting in new problems such as greatly disturbing the line impedance of the main line 3 and increasing propagation loss.Disadvantage 25 (O) The purpose of the present invention is to This method eliminates the drawbacks of the main line by installing an intermediate frequency signal blocking circuit in series with the main line that exhibits pass characteristics for high frequency signals and local oscillation signals, but exhibits open impedance for intermediate frequency signals. By using the line length of the main line to short-circuit the loading point of the mixer diode in a high frequency manner, the loading point of the mixer diode can be short-circuited even when the intermediate frequency signal frequency is high. .

Embodiments of the present invention will be sequentially described below. FIG. 2 shows one embodiment of the present invention, and the same parts as in FIG. 1 are given the same numbers and will be explained. The high frequency signal input from the high frequency signal input terminal 1 and the local oscillation signal input from the local oscillation signal input terminal 2 are respectively propagated through the main line 3 and applied to the mixer diode 4. Reference numeral 6 denotes a low-pass filter, which is provided to extract the intermediate frequency signal from the intermediate frequency signal output terminal 6 and at the same time short-circuit the terminals of the mixer diode 4 for high frequency signals and local oscillation signals. The length is one wavelength (!-) of a high frequency signal or local oscillation signal
It consists of an open-ended stub and a series inductor 4 4 capance. Reference numeral 8 denotes an intermediate frequency signal blocking circuit that exhibits a pass characteristic for high frequency signals but exhibits an open impedance for intermediate frequency signals. A low-pass filter 9 with an open end is connected in parallel to the main line 3, and a mixer/
The distance to the diode 4 is selected to be one wavelength of the intermediate station wave λIF signal ←7-). 1o is an intermediate frequency signal blocking circuit that exhibits a pass characteristic for local oscillation signals but exhibits an open impedance for intermediate frequency signals. A bandpass filter 11 is connected in parallel to the main line 3,
The distance from the open end of the low-pass filter 11 to the mixer diode 4 is selected as one wavelength (-!L!-) of the intermediate frequency signal.

In the embodiment of FIG. 2, intermediate frequency signal blocking circuits 8 and 10
Both exhibit open impedance for intermediate frequency signals, and the distance from mixer diode 4 to the open ends of low-pass filters 9 and 11 is selected to be the length of one wavelength of the intermediate frequency signal. , mixer diode 4
Terminal B of is short-circuited with an intermediate frequency signal for high frequency purposes.

Therefore, even if the intermediate frequency signal frequency is high, the diode loading point can be reliably short-circuited. Furthermore, since the intermediate frequency signal blocking circuits 8 and 10 are provided in series with the main line 3, the short-circuited state of the diode loading point B is prevented from occurring from the circuit connected to the high frequency signal input terminal 1 or the local oscillation signal input terminal 2 side. The effects can be eliminated.

FIG. 3 shows another embodiment of the present invention, which is basically a second embodiment of the present invention.
Although it is the same as the embodiment shown in the figure, in the embodiment shown in FIG. The intermediate frequency signal blocking circuit 8 is removed, and only the intermediate frequency signal blocking circuit 10 is provided, which exhibits a pass characteristic for local oscillation signals but exhibits an open impedance for intermediate frequency signals. This is different from the embodiment shown in FIG.

Also in the embodiment of FIG. 3, the intermediate frequency signal blocking circuit 10
shows an open impedance for intermediate frequency signals,
Moreover, from the mixer diode 4 to the low pass filter 1
Since the distance to the open end of 1 is selected to be the length of one wavelength of the intermediate frequency signal, the terminal B of the mi9vex diode 4 is short-circuited at high frequency by the intermediate frequency signal. Therefore, even if the intermediate frequency signal frequency is high, the diode loading point is a! It can actually cause a short circuit. Moreover, what about the diode loading point B? 1! Since it is actually short-circuited, the influence from the circuit connected to the high-frequency signal input terminal 1 side can be greatly reduced. Furthermore, since no intermediate frequency signal blocking circuit is provided on the main line 3 on the high frequency signal input terminal 1 side, there is no insertion loss of high frequency signals due to the intermediate @wave signal blocking circuit.

FIG. 4 shows a specific method of configuring the intermediate frequency signal blocking circuits 8, 1o in the embodiment of the present invention. Figure 4a
is an i-wavelength line-coupled interdigital DC blocking circuit,
Two open-ended IJ tube lines are distributed coupled over the length of approximately one wavelength (a) of a high-frequency signal or local oscillation λ signal from the open end. Alternatively, it has low insertion loss for local oscillation signals and exhibits band-pass filter characteristics over a wide band. However, the capacitance between gears due to the coupling gap of two open-ended 1° trip lines that are distributed coupled is:
For example, the high frequency signal @ wave number is 126 [normally 0,1 at z
pF or less, and even if the inter-gear capacitance is 0.1 p1, when the intermediate frequency signal frequency is 1 GHz, the impedance indicated by the inter-gear capacitance is approximately 1.6 Ω, which is close to the open impedance.

Figure 4 shows a bandpass filter using a half-wavelength strip line resonator. By selecting the length of the half-wavelength strip line resonator for a high-frequency signal or local oscillation signal 1 λ - wavelength (i) K, it is possible to transmit a high-frequency signal or It exhibits a pass characteristic for local oscillation signals, but because one end of the line is open for intermediate frequency signals, it operates as an intermediate frequency signal blocking circuit and exhibits open impedance.

FIG. 6 shows still another embodiment of the present invention, which is a somewhat modified version of the mixer circuit in the embodiment of FIG. 3, in which the circuit shown in FIG. 4 is used as the intermediate frequency signal blocking circuit 10. The high frequency signal input from the high frequency signal input terminal 1 is transmitted to the main line 3.
is propagated to mixer 11, -, , and applied to diode 4. On the other hand, the local oscillation signal input from the local oscillation signal input terminal 2 is applied to the mixer diode 4 via the local oscillation signal band-pass filter 12 coupled to the main line 3 in a high-8f manner. The intermediate quantity wave signal generated by the mixer diode 4 is then passed through a low-pass filter 6.
The signal is taken out from the intermediate frequency signal output terminal 6 via the intermediate frequency signal output terminal 6. The main line 3, which is closer to the local oscillation signal input terminal 2 than the mixer diode 4, has an open end.
4 Low-pass filter 1 with an open end in parallel with the main line 3
1 is connected, and the distance from the open end of the low-pass filter 11 to the mixer diode I''4 is selected as one wavelength (7) of the intermediate λIF same-wave signal, and the main wavelength of the local signal band-pass filter 12 is selected. The position of the high frequency coupling point C is selected so that the impedance viewed from the high frequency coupling point C to the line 3 to the open end side of the main line 3 becomes open due to the local oscillation signal.

Therefore, the terminal B of the mixer diode 4 is short-circuited in a high frequency manner by the intermediate quantity wave signal. Therefore, even if the intermediate frequency signal amount and wave number are high, the diode loading point can be reliably short-circuited. Moreover, since the diode loading point B is reliably short-circuited, the influence from the circuit connected to the high frequency signal input terminal 1 side can be extremely reduced. moreover,
Since no intermediate frequency signal blocking circuit is provided on the main line 3 on the high frequency signal input terminal 1 side, there is no insertion loss of high frequency signals due to the intermediate frequency signal blocking circuit.

As explained above, in the present invention, an intermediate same-wave signal blocking circuit is provided on the main line, which exhibits a pass characteristic for high-frequency signals or local oscillation signals, but exhibits an open impedance for middle-frequency signals. A low-pass filter with an open end is connected near the same wave signal blocking circuit, and a mixer is connected from the open end of the low-pass filter with an open end.
By choosing the distance to the diode to be the length of one wavelength of the intermediate signal, the loading point of the mixer diode is
, which causes a high-frequency short circuit with the same wave signal. Therefore, even when the intermediate frequency signal amount and wave number are high, the diode loading point can be reliably short-circuited. In addition, since the intermediate frequency signal blocking circuit is provided in series with the main line, it reduces the influence of the short-circuit condition at the diode loading point from the circuit connected to the high frequency signal input terminal or local oscillation signal input terminal side. It can be done or removed. In addition,
This improves the performance of mixer circuits.

[Brief explanation of the drawing]

FIG. 1 is a pattern diagram of a conventional mixer circuit using a microwave integrated circuit, FIG. 2 is a pattern diagram of a mixer circuit according to an embodiment of the present invention, and FIG. 3 is a pattern diagram of a mixer circuit according to another embodiment of the present invention. FIG. 4 is a pattern diagram of a concrete configuration circuit of the intermediate frequency signal blocking circuit in the embodiment shown in FIGS. FIG. 6 is a pattern diagram of a mixer circuit according to still another embodiment of the present invention. 1... High frequency signal input terminal, 2... Local oscillation signal input terminal, 3... Main line, 4...
...Mixer diode, 6...Low pass filter, 6...Intermediate frequency signal output terminal, 8,
10 Town, intermediate frequency signal blocking circuit, 9, 11...
・Low pass filter. Name of agent: Patent attorney Toshio Nakao and 1 other person11
Figure 13 Figure 114 Figure 5

Claims (2)

[Claims] (1) One end of a mixer diode is connected to a main line composed of a strip line or a microstrip line, and a high frequency signal is transmitted from one end of the main line, and a local oscillation signal is transmitted from the other end of the main line to the mixer diode. In a mixer circuit using a microwave integrated circuit configured to apply a signal to a diode F and take out an intermediate same wave signal, which is a frequency component of the difference between a high frequency signal and a local oscillation signal, from the other end of the mixer diode, A low-pass filter with an open end is connected in parallel to the main line to at least one end side or the other end side of the main line, and a low-pass filter with an open end is connected to the mixer diode. The distance is selected to be % wavelength length of the intermediate same wave signal, and the distance is set on the main line near the connection point of the main line and the open-ended low-pass filter and on the input side of the high frequency signal or local oscillation signal. A mixer circuit characterized in that an intermediate frequency signal blocking circuit is provided in series with the main line, which exhibits a pass characteristic for high frequency signals or local oscillation signals, but exhibits open impedance for intermediate same wave signals. . (2) As an intermediate same-wave signal blocking circuit, it is composed of a long-wavelength line-coupled interdigital DC blocking circuit that is distributed-coupled over a length of approximately μ wavelength of a high-frequency signal or local oscillation signal from the open end of two terminals. A mixer circuit according to claim 1, characterized in that: