JPS59198011A - Balance mixer circuit - Google Patents

Abstract

PURPOSE:To decrease the coupling between an RF signal terminal and a local oscillating signal terminal by providing the local oscillating signal terminal to a position in the inside of a region surrounded by a microstrip line and also having an identical distance from two mixer diodes. CONSTITUTION:The local oscillating input terminal 2 is positioned in the inside of a closed loop line 31 of a branch line type hybrid circuit 30 and on a line segment A-A' having an identical distance in a straight line from the two mixer diodes 6. A local oscillating circuit 10 is provided to a ground conductor side of a board 11 and its output terminal is connected to the terminal 2 via a hole made to a part corresponding to the terminal 2. Since the coupling between the lines of the RF input terminal 1 and the terminal 2 is reduced considerably because of the presence of the line 31 in between in this way and since the local oscillating power irradiated from the terminal 2 to the diodes 6 directly is shared equally, the balance operation of the mixer is not disturbed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a frequency mixing circuit using a planar circuit such as a microstrip line, and in particular to a balanced mixer using a hybrid composed of microstrip connections. Regarding circuits.

[Technical background of the invention and its problems]

Generally, when forming a mixer in the microwave band, R
A balanced mixer using a hybrid circuit is recommended because it is easy to match the impedance with the external circuit at one F-terminal terminal, and the isolation gap between the RF terminal and the local oscillation terminal can be easily increased in principle. Many circuits are used.

Conventionally, balanced mixer circuits using microstrip lines mainly include branch line hybrid circuits 3a and 3b formed in the patterns shown in Fig. 1(a) and (b), or branch line type hybrid circuits 3a and 3b formed in the patterns shown in Fig. The rat race hybrid circuit 3c shown has been used. In both of these cases, the signal input to the A terminal appears at the C and D terminals with a frequency level of 1/2,
It has the characteristic that no signal appears at the B terminal. Similarly, the signal input to the B terminal also appears at the C and D terminals with a frequency level of IA, and A
No signal appears at the terminal. Therefore, it is necessary to input the RF multiplied signal to the A terminal, the local oscillation signal to the B terminal, and the C
Connect one mixer diode to the terminal and the D terminal in opposite directions, and connect the two output terminals of those mixer diodes to one
Together, they constituted a balanced mixer circuit. FIG. 2 shows the configuration of a balanced mixer circuit using a no-brid circuit. 1 is an RF signal input terminal, 2 is a local oscillation signal input terminal.

3 is a hybrid circuit, and 6 is a mixer diode.

Reference numeral 8 indicates a low frequency f-wave device, and reference numeral 9 indicates an IF signal output signal.

Hereinafter, when referring to the same thing, the same number will be used in each figure.

FIG. 3 shows a balanced mixer circuit using a branch line type hybrid circuit as a conventional example. In FIG. 3, 4 is a stub circuit for shorting the IF signal to which the output terminal line 4o of the branch line type hybrid circuit 3 is connected, 5 is a grounding conductor, 7 is an open stub for shorting the R'F signal, and 8 is a stub circuit for shorting the IF signal. Low frequency f wave device, 9 is IF signal output terminal, 10
11 is a local oscillation circuit built into the case, and 11 is a board on which a mixer circuit is mounted. The RF multiplied signal input from the input terminal line 1 and the local oscillation signal input from the input terminal line 2 are applied to the mixer diode 6 via the branch line type hybrid circuit 3, and the difference signal between the RF multiplied signal and the local oscillation signal is generated. IF multiplied signal I 'F signal' signal output terminal 9
taken from.

However, in the pattern shape of the conventional branch line type hybrid circuit or rat race type hybrid circuit, each terminal line is all provided outside the area surrounded by micro strips and lip lines, and input terminals to which different signals are applied. In addition to coupling between the line of input terminal 1 and the line of input terminal 2, there is also a coupling between the two mixer diodes from input terminal 2, which receives a local oscillation signal that is extremely large in power compared to the RF multiplied signal applied to input terminal 1. There was a problem in that the radiation of the local oscillation signal had an adverse effect on the balance mixer.

[Purpose of the invention]

It is an object of the present invention to reduce the coupling between the input terminal line to which the RF multiplied signal of a conventional balanced mixer circuit is input and the input terminal line to which the local oscillation signal is injected, and to reduce the coupling from the local oscillation signal terminal to the mixer diode. The objective is to improve the performance of the balanced mixer circuit by equalizing the local radiated power.

Another purpose is to suppress the radiation of local oscillation output itself.

[Summary of the invention]

The present invention locates the local oscillation signal terminal of a branch line type hybrid circuit or a rat race type no-blit circuit of a balanced mixer circuit at a location within an area surrounded by a microstrip line and at an equal distance from two mixer diodes. It is characterized by the fact that it has been established.

〔Effect of the invention〕

According to the present invention, the coupling between the RF signal terminal and the local oscillation signal terminal of the balanced mixer circuit can be reduced, and the balance mixer circuit performance is improved by equalizing the local oscillation radiation power from the local oscillation signal terminal to the mixer diode. In addition, the radiation of the local oscillation output itself can be suppressed.

Furthermore, as a secondary effect, by installing the local oscillation circuit on the back surface of the substrate, it is possible to reduce the area occupied by the pattern of the mixer circuit.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows an embodiment of the present invention.

The parts with the same numbers as in the conventional example shown in FIG. So, the straight line distance between the two mixer diodes 6 is equal, and the line segment A-A in FIG.
'It is a point located on the ground. '1: The local oscillation circuit 10 embedded in the case is provided on the ground conductor side of the board 11, and its oscillation output terminal is connected to the local oscillation input of the branch line type hybrid circuit 30 on the forbidden plate pattern. It is connected to the local oscillation input terminal 2 through a hole drilled in a portion corresponding to the terminal 2. In this structure, the coupling between the lines of the RF input terminal l and the local oscillation input terminal 2 is greatly reduced due to the presence of the closed loop line 31 of the VC branch line type hybrid circuit 30, and at the same time Since the local '44fi power directly radiated from the oscillation input terminal 2 to the X mixer diode 6 is evenly divided, the balance operation of the mixer is not disturbed. Further, since the closed loop line 31 of the branch line hybrid circuit 30 shields the local oscillation input terminal 2 from external circuits, the radiation of the oscillation output itself is suppressed.

Further, according to the present invention, the local oscillation circuit 10 is connected to the substrate 11.
By providing it on the grounding body side, it is possible to significantly reduce the required board surface clearance compared to the conventional method. In this way, the present invention provides a branch line type hybrid circuit 3.
By changing the position of the 00 local oscillation input terminal 2, the performance of the mixer circuit can be improved, and at the same time, the circuit can be made smaller by reducing the board area.

FIG. 5 is a diagram showing an example in which the present invention is implemented in a omnidirectional branch line type hybrid circuit 32, and FIG. 6 is a diagram showing an example in which the present invention is implemented in a rat race type hybrid circuit 33.

[Brief explanation of drawings]

Figure 1 is a pattern diagram of a hybrid circuit used in a conventional balanced mixer circuit, Figure 2 is a block diagram of a balanced mixer circuit, and Figure 3 is a diagram of a conventional balanced mixer circuit using a hybrid circuit. Circuit configuration diagram, 4th
The figure is a block diagram of a balanced mixer circuit according to one embodiment of the present invention, and FIGS. 5 and 6 are block diagrams showing other embodiments of the present invention. 1...RF signal input terminal line, 2...Local oscillation signal input terminal, fitting, 6...Mixer diode)', 10-
... Local oscillation circuit, 11... Board, 30, 32.33
... No-event circuit, 31... Closed loop line, 40-1. Output terminal line. Representative Patent Attorney Noriyuki Chika (and 1 other person) 49 Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) A closed loop line, a first input terminal line radially connected to the outer periphery of the closed loop line, and a first input terminal line. Second
and a second input terminal line located inside the closed loop line and connected to the inner periphery of the closed loop line. are connected in common, and the other end is connected to the first. two frequency mixing elements respectively connected to the second output terminal line; A balanced mixer circuit that supplies first and second input signals to each of the second input terminal lines and obtains a frequency conversion output from a common connection end of the two frequency mixing elements. (2) The balanced mixer circuit according to claim 1, wherein the second input terminal line located inside the closed loop line is equidistant from the two frequency mixing elements. (3) The first input signal is an RF multiplied signal, the second input signal is a local oscillation signal output from a local oscillation circuit, and the local oscillation circuit is installed on the back side of the board. A balanced mixer circuit according to claim 1.