JPS6271316A - High frequency step attenuator - Google Patents

Abstract

PURPOSE:To obtain a step attenuator using gone switch element and a simple control circuit by connecting a switching diode or a PIN diode in parallel with a resistor forming a bridge of a pi type resistance attenuation section and connecting respectively a resistor to an input/output section of the pi type circuit. CONSTITUTION:The pi type attenuator consist of resistors 105-107 and a diode 109 and resistors 104, 108 are resistors to improve the VSWR. As the diode 109, a high frequency switching diode or a PIN diode is used and the step attenuator is realized by the simple control whether or not a voltage is impressed to a control terminal 103. The diode id matched in two states of on/off sufficiently by connecting a resistor to the input/output of the pi type circuit. The fixed loss is increased more or less by the insertion of the resistor but since the VSWR characteristic is improved remarkably, the VSWR is not deteriorated even with multi-stage connection or the connection of other external circuit and the attenuation by the design value is realized with good reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a high frequency step attenuator that is applied to rice cake belts and is used for signal level adjustment or signal level control of wireless communication devices and signal generators. It is related to.

Conventional technology Step attenuators are circuits that are often used to adjust or control signal levels. Examples of conventionally used circuits are shown and explained in Figures 4 to 6. do.

FIG. 4 shows the most basic configuration, which is realized using two switches. Figure 4 ζ 401,
402 is an input and output terminal, 404 and 405 are switches, 406 is a fixed attenuator, and 403 is a switch.

Child control signal terminals are shown.

As is clear from FIG. 4, two switches 404,
Attenuator 40 is installed between input and output by switching 405 at the same time.
Since you can choose between inserting 6 and connecting directly,
The amount of attenuation 406 between input and output can be controlled. In this configuration, the switches 404 and 405 are mechanical switches of the same type as FLL+'J, and the attenuation amount 406 can be set accurately, the insertion loss of the switch is small, and the input/output V8 flow is good. It handles large amounts of power and has the best electrical characteristics of a step attenuator, such as scales, but it lacks reliability because it has mechanical contacts, and the control system consumes a lot of power because it drives a relay. It has drawbacks such as high cost and high cost.

In order to eliminate these drawbacks, T-type or π-type variable attenuators using PIN diodes whose resistance values can be electrically controlled have also been known. FIG. 5 shows an example of a π-type variable attenuator. In FIG. 5, 501 and 502 are input and output terminals, 503 and 504 are control terminals, and 505
507 is a PIN diode forming a π-type resistance attenuator, 508 to 511 are DC blocking capacitors, and 512 to 511 are DC blocking capacitors.
514 is an RFC (high frequency choke coil).

Problems to be Solved by the Invention Although this circuit is capable of controlling the current flowing through the PIN diodes 505 to 507 and continuously changing the amount of attenuation over a wide range,
Since it is necessary to control the control currents separately from the control currents 6, 505, and 507, the design of the attached control circuit is complicated, and adjustment is labor-intensive, resulting in high costs. In addition, an inverted attenuator using two diodes may be used to eliminate the number of elements, but in this case as well, the diodes need to be controlled separately, so the problem with the control circuit is essentially solved. Therefore, no cost reduction can be expected.

In view of the above-mentioned conventional drawbacks, the present invention aims to realize a step attenuator with a single switching element and a simple control circuit, thereby reducing the power consumption of the control circuit and the cost of the attenuator. be.

Means for Solving the Problem The present invention provides a switching diode in parallel with the resistor of the part forming the bridge of the π-type resistive attenuator.
By connecting a diode and connecting a resistor to the input and output parts of the π-type circuit to improve the input and output V♀ flooding, it becomes a basic step attenuator, and this circuit can be continuously connected in multiple stages to create a multi-step attenuator. The aim is to realize an attenuator at low cost.

Effect When a switching diode is connected in parallel to the bridge resistance of the π-type resistance attenuation section and the diode is set to 0N10FF, the effective resistance of the bridge section changes depending on the resistance of the diode when it is ON and the resistance when it is OFF. Of course, the amount of attenuation can also be changed. This is a well-known fact, but with this circuit alone, the attenuation can be designed to match the set value, but if it is designed so that the input and output are matched when the diode is ON, then when OF'l' In this case, the input/output matching deteriorates at the top. On the other hand, if the circuit is designed to be matched during "OFI", the matching during ON will deteriorate.For this reason, when this circuit is connected in cascade with an attenuator of the same configuration, it is different from that of other amplifiers, etc. When connecting to an external circuit, the matching state at ON and OFF, i.e. r
)vS~■ are extremely different, so the change in attenuation amount due to switching differs from the designed value, and it cannot be said to be a practical circuit.

In order to improve this ~'Sw'lt, in the present invention, the input and output of the π-type circuit (by connecting this resistor, sufficient matching can be achieved in the two states of the diode ON and 01"F). Although the fixed loss increases slightly by inserting this resistor, the vswrt characteristics are greatly improved, so even if you connect multiple stages or connect other external circuits, the VS
The deterioration of IA7R is small, and the amount of attenuation that matches the design value can be achieved with good reproducibility. Further, the number of elements can be realized with the minimum required number, and the control circuit is extremely simple because it only requires switching between 0N10FF.

Embodiment FIG. 1 is a circuit diagram of a high frequency step attenuator showing one of the most basic embodiments of the present invention.

In FIG. 1, 101 and 102 are input and output terminals, 103 is a control terminal, 10, 1 to 108 are resistors, and 10
9 is a switching diode, 110 and 111 are DC blocking capacitors, and 112 and 113 are high frequency choke coils (Y is also 12C). Resistance 105 ~]
07 (L-diode 109 constitutes a T-type attenuator, 1.04 and 108 are resistors (
be. The diode 109 may be a high-frequency switching diode or a PIN diode, and a step attenuator can be realized by simply controlling whether or not to apply a voltage to the control terminal 103.

Now, when the ON resistance of the diode 109 is 10Ω and the OFF resistance is about Ω, the value of each resistor 104 and 108 is 5Ω.
0゜Resistance 105, 107 is 120Ω, resistance 106 is 6
If 0Ω is selected, the input/output attenuation when ON is 5.2 dB and the input/output return loss is 13.3 dB, and the attenuation when OFF is 9.2 dB and return loss is 21.7 dB. In other words, step attenuation is 4 dB (9, 2 - 5, 2 = 4.0
), it is possible to realize an attenuator with a return loss of 18.3 dB or less. Since the input/output vswrt is 15 or less, changes in attenuation due to mismatching can be ignored even when connected in multiple stages or with an external circuit.

FIG. 2 shows a multi-step attenuator in which three stages of the basic attenuators shown in FIG. 1 are connected in cascade, and shows an example of a 3-bit (8-step switching) configuration.

In Fig. 2, 201 and 202 are input/output terminals, 20
3 to 205 are control terminals, 206 to 218 are resistors, 219
-221 are diodes, 223-228 are DC blocking capacitors, and 229-233 are RFCs.

Now, the control signals of the control terminals 203, 20-1, and 205 are C1, C2, and C3, and the attenuations controlled by the respective signals are 4dB, 8dB, and 16dB, and the total attenuation is 4n (n-0 to 7). )+dB. Similarly to the example in Figure 1, the diode is ON, 01
"l" resistance is 10Ω.

1 alternating current), in order to obtain the above attenuation amount, each resistance value is, for example, resistance 206: sΩ, resistance 207: 1
20Ω, resistance 208: 60Ω, resistance 209: 1
20Ω, resistance 210: I5Ω, resistance 211: 10
0Ω, resistance 212: 160Ω, resistance 213:100
Ω, resistance 214: 25Ω, resistance 21.5: 70
Ω, resistance 216: 730Ω, resistance 217: 70
Ω, resistance 218: It can be provided as 15Ω. When the diode is ON at 0 and OFl;', the attenuation amount for each signal is calculated by multiplying by 1, and the result is as shown in the table.

There is a fixed loss in the margin attenuation below, but the relative value is 4n±
This shows that switching in eight idB steps of 0.5 dB (n = 0 = 7) is possible.

FIG. 3 shows another embodiment of the invention.

As can be seen from the embodiments shown in Figs. 1 and 2, the step attenuator shown in Figs. 1 and 2 essentially has a fixed loss; FIG.

In Fig. 3, 301 and 302 are input/output terminals, 3o
3 is a control terminal, 304 is a step attenuator shown in FIGS. 1 and 2, and 305 is an amplifier. Amplifier 305 has its gain set to have a gain that compensates for the fixed loss of step attenuator 304.

This amplifier 305 needs to have the characteristics that its gain is flat (constant) over a wide band and its output level is large. If the output level is small, the step attenuator 3o4 (followed by the amplifier 305 must be connected; otherwise, the amplifier 305
In addition to not being able to obtain compensation gain by summing the output levels of

Effects of the Invention As described above, the present invention has the characteristics that the basic step attenuator includes only one switching element, the control circuit is simple, and the input/output VSWR is small. , a multi-stage configuration is easy and a multi-step attenuator can also be realized. Therefore, a highly accurate attenuator can be realized at low cost, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a high frequency step attenuator according to one embodiment of the present invention, FIGS. 2 and 3 are circuit diagrams of other embodiments of the same high frequency step attenuator, and FIGS. 4 and 5 are conventional circuit diagrams. FIG. 3 is a circuit diagram of an attenuator. 101, 201, 301...input terminal, 102, 2
02, 302...output terminal, 103, 203-205
, 303...control terminal, 109, 219-221...
Switching or PIN diodes, 104-108
, 206-218...Resistance. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2

Claims (3)

[Claims] (1) A switching or PIN diode is connected in parallel to the resistor forming the bridge part of the resistance attenuation section composed of a π-type circuit, and a resistor is connected in series to the input and output of the π-type circuit to perform input/output. High frequency step attenuator with terminals. (2) Attenuation amount is 2^n^-^1 (however, n=1, 2, 3
. . .) The high frequency step attenuator according to claim 1, characterized in that the high frequency step attenuator is constructed by cascade-connecting n unit attenuation sections set to differ by a factor of two times. (3) The high frequency step attenuator according to claim 1, characterized in that it is constructed by subsequently connecting an amplifier for loss compensation.