JPS5972206A - Mixer circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises a strip line using a dielectric substrate. The present invention relates to a mixer circuit using a so-called microwave integrated circuit (hereinafter referred to as MIC circuit) system or a system configured using coaxial lines.

The mixer circuit inputs a received input signal (frequency fs) and a local oscillation signal (frequency fl) and outputs an intermediate frequency signal having a frequency fi (=Ifs fil) which is the difference between these two signal frequencies.

FIG. 1 is a block diagram of one configuration example of a mixer circuit, and a received human input signal is input from a terminal 1-1'. The reception input side filter circuit 11 passes the reception input signal and exhibits an almost open impedance characteristic for the local oscillation signal. The local oscillation side filter circuit 12 passes the local oscillation signal and exhibits almost open impedance characteristics for the received input signal. Also, intermediate frequency output side filter circuit 1
5 passes an intermediate frequency signal and exhibits a short-circuit impedance characteristic for a received input signal and a local oscillation signal. Also, there is a short circuit in terms of direct current.

The DC feedback circuit 16 exhibits a nearly open impedance characteristic with respect to the received input signal and the local oscillation signal, is short-circuited in terms of DC, and constitutes a feedback circuit for the bias DC current of the mixer diode.

The impedance characteristics of the reception input filter circuit, local oscillation filter circuit, and DC feedback circuit for intermediate frequency signals are all required to have a value close to a short circuit, or the combined parallel admittance is required to have a value close to a short circuit.

The received input signal inputted from the terminal l-1' is sent to the mixer diode 14 .
The intermediate station M"-'J
II"7"()L"5' Terminal 2 via 0 path 15
-2', the intermediate frequency signal is output.

Now, in such a mixer circuit, in order for the intermediate frequency signal generated at the mixer diode 14 to be efficiently output to the intermediate frequency signal output terminal 2-2', the mixer diode 14 must be High frequency side, that is, the first
From terminal a-a' in the figure to reception input end filter circuit 1
1. Local oscillation side filter circuit 12 and DC feedback circuit 1
I looked at the circuit side including 6. The parallel admittance must be short-circuited.

However, depending on the filter circuits etc. actually used in the circuit, the optimal required characteristics for each filter circuit as described above cannot be fully satisfied, and the parallel admittance cannot be almost short-circuited. Due to the resonance, a frequency point exhibiting an open admittance may exist in the used intermediate frequency signal band. At such frequencies, the high frequency side end a-a' of the mixer diode 14
Since the impedance between the mixer and the mixer becomes an open impedance even though it should be short-circuited, a steep conversion loss characteristic deterioration (trap phenomenon) occurs in the output frequency characteristic of the mixer circuit at the above frequency.

For example, FIG. 2 shows an implementation example of the mixer circuit shown in the block diagram of FIG. 1, and only the center conductor side is shown.
22 is a local oscillator side filter circuit, 23 is a local oscillator, 2
4 is a mixer diode, 25 is an intermediate frequency output side filter circuit, 26 is a DC feedback circuit, and 2 is an intermediate frequency output terminal.

The admittance when looking at the high frequency side from point a in Figure 2 is
It is represented by a parallel circuit of three admittances: admittance Y1 seen from the reception input side filter circuit 21 side, admittance Y2 seen from the local oscillation side filter circuit 22 side, and admittance Y6 seen from the DC feedback circuit 26 side from the point.

Now, if we use filter circuits of each type as shown in Figure 2, the admittance Y is the electrical connection between point a and the local oscillation side filter circuit so that it is almost open in the received input signal band. Physical distancing will be determined. However, since the intermediate frequency signal is generally at a sufficiently low frequency compared to the received human signal, this physical distance is sufficiently short compared to the quarter wavelength of the intermediate frequency signal, and therefore the intermediate frequency signal The above admittance Y2 in the band
becomes capacitive. In order to short-circuit this admittance Y2 to the intermediate frequency signal, the above physical distance must be set to 1/4 wavelength, which is quite large and impractical. . Similarly a
The admittance Y6 when looking at the DC feedback circuit 26 from the point is
Since the DC feedback circuit is a grounded stub circuit with a line length of about a quarter wavelength for the received human power signal and local oscillation signal, it becomes inductive in the intermediate frequency signal band. Further, the admittance Y1 seen from the same point a toward the receiving input fill circuit side changes variously depending on the input circuit connected to the terminal 1 for the intermediate frequency signal.

Therefore, these admittances Y1. The sum of Y, , and Y6 may become zero at a certain frequency because each value has various frequency characteristics, and this occurs within the intermediate frequency signal band, resulting in a characteristic that includes a trap circuit. .

Furthermore, even if a filter circuit of a type other than that shown in Fig. 2 is used for each filter circuit in Fig. 1, the impedance characteristics of the filter circuit itself at each input end will be different in the intermediate frequency signal band. Most of them have a reactance close to an open circuit or a short circuit, and in either case, the trap phenomenon described above may occur.

The present invention aims to eliminate such a trap phenomenon within an intermediate frequency signal band.

FIG. 3 shows a specific embodiment of the present invention, in which intermediate frequency trap removal circuits 37 and 38 are connected to the mixer circuit of FIG. It is provided at an appropriate position on the main line 39.

The intermediate frequency trap removal circuits 87 and 88 are both parallel stub circuits having a line length equal to an odd multiple of a quarter wavelength of the received input signal and/or local oscillation signal, and have their ends grounded. For local oscillation signals, it exhibits an open admittance characteristic, and the intermediate frequency trap removal circuit has almost no effect in the reception input signal band and the local oscillation signal band. on the other hand,
Since the admittance characteristic of the intermediate frequency trap removal circuit in the intermediate frequency signal band shows inductivity close to a short circuit, the admittance when looking at the local oscillation side filter circuit 22 and reception input end filter circuit 21 side from point a in FIG. By appropriately selecting the positions where the intermediate frequency trap removal circuits 37 and 38 are provided, both can be made inductive.

At this time, the admittance characteristics of the current feedback circuit 26 viewed from the point a will all exhibit inductive properties, and it is possible to avoid the occurrence of the parallel resonance phenomenon due to inductive and capacitive admittance as described above. . Also, depending on the admittance characteristics of each filter circuit and current feedback circuit viewed from point a, even if only one of the intermediate frequency trap removal circuits 37 and 38 is provided, the frequency of the parallel resonance may be removed outside the used intermediate frequency signal band. You can also do that.

FIG. 4 is a block configuration diagram of a mixer circuit in a diagonal form as shown in FIG. 1. FIG. 5 is one specific example of the mixer circuit shown in the block diagram of FIG. 4, and shows only the center conductor side of the burnt strip line.

41.51 shows a nearly open impedance characteristic for the local oscillation signal, and a receiving input end filter circuit that passes the received input signal; 42.52 shows a nearly open impedance characteristic for the received input signal. 43.53 is a local oscillator, 44.54 is a mixer diode with one end grounded, 45.55 is a filter circuit on the local oscillation side that passes the local oscillation signal, and 45.55 blocks the receiving human power signal and the local oscillation signal, and passes the intermediate frequency signal. This is an intermediate frequency output side filter circuit that passes through.

In the case of this type of mixer circuit, the mixer diode 54.
from the terminal point a connected to the main line 69 of the local oscillation side filter circuit 52 or the reception input side filter circuit 51
If the admittance characteristic observed falls within the intermediate frequency signal band and shows a short-circuit admittance, that is, one of the filter circuits has an open admittance at its input end, and the Either the electrical length is approximately equal to an odd multiple of 1/4 wavelength of the intermediate frequency signal, or the filter circuit has approximately a short circuit admittance at its input end, and from its input end to the mixer diode end a. When the electrical length of the intermediate frequency signal is close to an integral multiple of a half wavelength of the intermediate frequency signal, the above-mentioned trap phenomenon occurs at a certain frequency within the intermediate frequency signal band.

In such a case, as shown in Fig. 6, the end of the main line 69 should be grounded at an appropriate position on the side of the filter circuit that causes the short-circuit admittance at the mixer diode terminal a, that is, on the receiving input side in Fig. 6. By connecting quarter-wavelength lines or odd-numbered multiple-length lines (stub circuits) 67 in parallel, the admittance seen from the mixer diode terminal a toward the filter circuit side can be made almost open in the intermediate frequency signal band. This can eliminate the trapping phenomenon.

In the circuit of the present invention, the receiving human power signal band and Also, the characteristics in the intermediate frequency signal band can be adjusted without changing the characteristics in the local oscillation signal, and the trap phenomenon in the intermediate frequency signal band caused by resonance or short circuit on the high frequency circuit side as described above can be eliminated. I can do it.

[Brief explanation of drawings]

Figures 1 and 4 are conventional examples of mixer circuits, Figures 2 and 5 are block diagrams of mixer circuits corresponding to Figures 1 and 4, respectively, and Figures 3 and 6 are according to the present invention. FIG. 3 is a block configuration diagram of an embodiment of the mixer circuit of FIG. In the figure, 1 is the reception input terminal, 11, 21, 41.51 is the reception input side filter circuit, 12, 22, 42.52 is the local transmission side filter circuit, 13.23, 43.53
is a local oscillator, 14.24, 44.54 is a mixer Φ diode, 15, 25, 45.55 is an intermediate frequency output side filter circuit, 2 is an intermediate frequency signal output terminal, 37°3
8.67 is a stub circuit, and 39.69 is a main line. 2' Figure 1 Figure 12 Figure 7r3

Claims (1)

[Claims] It is composed of an intermediate frequency multiplier signal input section, a local oscillation signal input section, a mixer diode, an intermediate frequency signal output section, etc. It inputs a reception input signal and a local oscillation signal, and generates an intermediate frequency signal having a frequency that is the difference between these two signals. In the output mixer circuit,
Either one or both of the received signal input section and the local oscillation signal input section is connected to a parallel squib having a line length approximately an odd number multiple of a quarter wavelength of the receiving human power signal or local oscillation signal used and whose tip is grounded. A mixer circuit characterized in that a circuit is provided at an appropriate position on the main line.