JPS6046883B2 - balanced mixer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a MIC parallist mixer that is capable of observing rectified currents of two mixer diodes.

As a circuit for observing the rectified current of a diode in a MIC (microwave integrated circuit) pararist mixer, the one shown in FIG. 1 has conventionally been used.

That is, 1 is an input terminal for a high frequency signal, 2 is an input terminal for a high frequency local oscillation signal, 3 is a hybrid coupler that divides each of the high frequency signal and local oscillation signal supplied to the first and second input terminals into two; 4 and 5 are mixer diodes, and 6 and 7 are low-pass filters that block high frequency signals and pass intermediate frequency signals generated by the mixer diodes. 8, 9
10 is a coupling capacitor that allows the intermediate frequency signal to pass; 10 is an output terminal for the intermediate frequency signal; 11 and 12 are intermediate frequency chokes that block the intermediate frequency signal; and 13 and 14 are monitor terminals provided to observe the rectified current of the mixer. and ammeter 1
5 is connected to both terminals.

16 is a high frequency choke.

In the circuit shown in Fig. 1, the rectified current of the mixer diode generated by applying the local oscillator input from the local oscillator input terminal 2 is as follows: Mixer diode 4 - Hybrid coupler 3 - Mixer diode 5 - Low pass filter (LPF) 7 - Intermediate frequency choke (IFC) 12-Ammeter 15-IFCII-LPF
6, the rectified current can be observed by the ammeter 15 connected to the monitor terminal. However, in this method, an ammeter 1 is connected between monitor terminals 13 and 14.
If an external circuit such as No. 5 is not connected, it will not operate as a mixer, and if an ammeter with a large internal resistance is used, it becomes difficult for rectified current to flow, resulting in a deterioration of the noise figure. The present invention was made in view of the above-mentioned drawbacks, and it is possible to monitor the rectified current of the diode in a balanced mixer, and it can operate as a mixer even when an external circuit for monitoring the rectified current is not connected. The purpose is to provide a balanced mixer that

In the balanced mixer according to the present invention, the output terminals of the two low-pass filters are connected via a resistor, so not only can the rectified current of the diode be observed with an ammeter or the like connected to the monitor terminal, but also A further feature is that the mixer operates as a normal mixer even when no ammeter or the like is connected to the monitor terminal.

Examples of the present invention will be described below.

FIG. 2 shows an embodiment of a balanced mixer according to the present invention. 21 and 22 are input terminals of a 90-wire hybrid coupler 23; for example, 21 is a high frequency signal input terminal, and 22 is a high frequency local oscillation input terminal.

Mixer diodes 24 and 25 LPFs 26 and 27 and intermediate frequency coupling capacitors 28 and 29 are connected to the output of the hybrid coupler 23, respectively, and the outputs of these intermediate frequency coupling capacitors 28 and 29 are connected to an intermediate frequency output terminal 30. The intermediate frequency output sides of the LPFs 26 and 27 are connected to monitor terminals 33 and 34 via intermediate frequency chokes 31 and 32 using inductors. Furthermore, LPF2
The intermediate frequency output sides of 6 and 27 are connected to each other via a resistor 35. The hybrid coupler 23 is grounded, for example, near the local oscillator input terminal 22 via a high frequency choke 36. Generally, a matching circuit is inserted between the hybrid coupler and the diode, but it is omitted in FIG. 2 for simplicity. In a balanced mixer with such a configuration, the mixer diode rectification current generated by local power is
It flows through the path of mixer diode 24 - hybrid coupler 23 - PF27 on mixer diode 25 - PF26 on resistor 35.

Therefore, this mixer operates regardless of the presence or absence of an external circuit connected to the monitor terminal. Note that if the resistance value of the resistor 35 is selected to be an appropriate value, for example, 10Ω, the noise figure of the mixer will not be degraded. FIG. 3 shows a configuration example in which a meter 37 is connected between the monitor terminals 33 and 34 of the balanced mixer shown in FIG. 2 to monitor the rectified current of the mixer diode.

In this case, it is not necessarily necessary to ground the local input terminal 22 via the high frequency choke 36. meter 37
If the meter 37 is a voltmeter, the current is determined by the voltage generated across the resistor 35, and if the meter 37 is an ammeter, the current is determined by the ratio of the internal resistance of the ammeter to the resistance value of the resistor 35. The rectified current can be observed by flowing through the ammeter, and it can be determined whether the mixer diodes 24 and 25 are operating normally. If a voltmeter with a large input resistance is used as the meter 37, a resistor whose value is about the same as the internal resistance of the voltmeter may be used in place of the intermediate frequency chokes 31 and 32.

Mixer diode 2 in the balanced mixer in Figure 2
Another configuration example for monitoring the rectified currents of 4 and 25 is shown in FIG.

That is, the monitor terminals 33 and 34 are connected to the meters 38 and 39, respectively.
Ground through. Then, the rectified current of the mixer diode 24 is as follows: mixer diode 24 - hybrid coupler 23 - RFC36 - ground dielectric - meter 38 - IFC3
The first path of the upper PF 26 and the mixer diode 24-
Hybrid coupler 23-RFC36-grounded derivative-
Meter 39-1F'C32 - Resistor 35 Upper PF26 2nd
The flow is divided into two routes. At this time, the ratio of current flow to the first and second paths is determined by the internal resistances of the meters 38 and 39 and the value of the resistor 35. Incidentally, for this connection, it is necessary to ground the local oscillator input terminal 22 via the high frequency choke 36. Similarly, the rectified current flowing through the mixer diode 25 also flows through the meter 39's path meter 38 and the resistor 35.
The flow is divided into two routes, and this division ratio is determined by the meter 39.
, 38 and the value of the resistor 35.

Therefore, the resistance value of the resistor 35 is large, and the meter 38,3
If the internal resistance of 9 is sufficiently small, the rectified current of mixer diode 24 can be monitored by meter 38, and the rectified current of mixer diode 25 can be monitored by meter 39 at the same time. Furthermore, 1
When using two meters, if the monitor terminal 34 is grounded and the monitor terminal 33 is grounded through this meter, the rectified current of the mixer diode 24 is controlled. If grounded, the rectified current of the mixer diode 25 can be monitored.

In this case, one and the same meter may be used as the meters 19 and 20, and accurate relative measurement is possible regardless of differences in the characteristics of the individual meters. Furthermore, in the circuit shown in FIG. 4, if a voltmeter is used as the meter 38 and the monitor terminal 34 is grounded, the rectified current of the mixer diode 24 flows through the resistor 35, so that a rectified current is generated across the resistor 35. The voltage can be observed with a voltmeter 38.

Similarly, a voltmeter is used as the meter 39 and the monitor terminal 3
3 is grounded, the rectified current of the mixer diode 25 flows through the resistor 35, so the voltage generated across the resistor 35 can be observed by the meter 39. That is, it becomes possible to independently monitor the rectified current of mixer diode 24 or 25. Next, a circuit pattern of a more specific embodiment in which the balanced mixer of the embodiment of the present invention shown in FIG.
As shown in the figure.

Numbers 41-56 correspond to numbers 21-36 in FIG.
43 is a branch line type 900 hybrid coupler,
48, 49 are chip capacitors or MOS capacitors,
51 and 52 are intermediate frequency chokes using spiral coils, and 55 is a chip resistor or thin film resistor, all of which are formed on a dielectric substrate with a ground conductor provided on the back surface.

In the balanced mixer shown in FIG. 2, the connection point between the intermediate frequency coupling capacitors 28 and 29 and the intermediate frequency output terminal 3
0, or if the input side of the device connected to the outside of this intermediate frequency output terminal 30 has a DC blocking function, short-circuit either of the intermediate frequency coupling capacitors 28 and 29. It also works as a balanced mixer. That is, when connecting the output terminals of the low-pass filters 26 and 27 to the intermediate frequency output terminal 30, if at least one of the connections is made through a capacitor, rectified current can be blocked. Furthermore, when a thin wire coil is used as an inductor, a resistance component is generated at the same time as inductance.

If this resistance reaches a magnitude of about several ohms, an inductor may be used as the resistor 35. In this case as well, a resistor is connected between the output terminals of the low-pass filters 26 and 27 because of the above-mentioned resistance. FIG. 6 shows a circuit configuration of another embodiment of the present invention.

In the figure, numbers 61 to 76 are number 21 in Figure 2.
- Corresponds to 36. In this embodiment, an inductor is provided at the position of the resistor 35. Intermediate frequency chokes 71 and 72
and a resistor 75 are connected in series as shown. and,
Monitor terminals 73 and 74 are taken out from the connection point between intermediate frequency choke 71 and resistor 75 and the connection point between resistor 75 and intermediate frequency choke 72, respectively. In this embodiment as well, the mixer diode can be operated without connecting an external meter. Furthermore, by connecting an external meter between the monitor terminals 73 and 74, the rectified current of the mixer diode can be monitored. Note that when an intermediate frequency amplifier is directly connected after the balanced mixer of the present invention, the intermediate frequency signal output terminal of the present invention is connected to the input terminal of an amplification element such as a transistor FET used in the first stage of the amplifier. It will be the same.

As explained above, according to the present invention, a resistor is connected between the output terminals of the low-pass filter, and the rectified current flows through this resistor, so the mixer operates normally even if a meter etc. is not connected to the monitor terminal. can be operated.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a conventional balanced mixer, Fig. 2 is a circuit diagram of a balanced mixer according to an embodiment of the present invention, and Figs. 3 and 4 are a circuit diagram of a conventional balanced mixer. A diagram showing a method for measuring rectified current of a diode, FIG. 5 is a diagram showing a circuit pattern in which the circuit of FIG. It is a configuration diagram. 3, 23, 43...Hybrid coupler, 4,
5, 24, 25, 44, 45, 64, 65... mixer diode, 6, 7, 26, 27, 46, 47, 66,
67...Low pass filter (LPF), 13,1
4, 33, 34, 53, 54, ノ73, 74...
・Monitor terminal, 35, 55, 75...resistance.

Claims (1)

[Claims] 1 A hybrid coupler whose first and second input terminals are respectively supplied with a high frequency signal and a high frequency local oscillation signal, and a mixer diode which is connected to the first and second output terminals of this coupler so as to be oriented in different directions. , a low-pass filter connected to each of these mixer diodes,
a resistor connected between the output terminals of these filters, an intermediate frequency signal output terminal connected to the output terminal of the low-pass filter via at least one capacitor, and each of the output terminals of the low-pass filter. A balanced mixer comprising: a monitor terminal connected to the mixer via a resistor or an inductor.