JPH10163786A - Attenuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an attenuator with which an insertion loss is more reduced. SOLUTION: Between a high frequency input terminal RF IN and a high frequency output terminal RF OUT, a serial resonance circuit 1 of inductor L1 and L2 and a capacitor C1 is connected. A parallel resonance circuit 2 of the inductor L1, capacitor C2 and diode D1 and a parallel resonance circuit 3 of the inductor L2, capacitor C3 and diode D2 are connected. A control terminal CONT is connected through resistors R1 and R2. The high frequency input terminal RF IN and high frequency output terminal RF OUT are grounded through the serial circuit of a diode D3 for matching and a resistor R3 or the serial circuit of a diode D4 and resistor R4 and the capacitor C1 is grounded through a diode D5 for signal shunt and a diode D6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a low insertion loss attenuator.

[0002]

2. Description of the Related Art In recent years, for example, an attenuator having a small insertion loss has been used for a mobile communication device such as an automobile telephone or a portable telephone.

[0003] Conventionally, as an attenuator of this kind of power loss, for example, a configuration described in Japanese Patent Application Laid-Open No. 6-152301 is known.

Japanese Patent Application Laid-Open No. 6-152301 discloses that
The four PIN diodes are connected in a π-type, and a high-frequency choke coil is connected to the control terminal side of the PIN diodes and the ground wiring. The high-frequency choke coil has a very small impedance with respect to the DC component, and the PIN diode is driven at a low voltage. Therefore, the attenuator can be driven at a low voltage and the insertion loss can be reduced.

[0005]

However, in the configuration described in Japanese Patent Application Laid-Open No. 6-152301, the PIN
Although the diode can be driven at a low voltage, there is a problem that the reduction of the high-frequency resistance of the diode is limited.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an attenuator with lower insertion loss.

[0007]

According to a first aspect of the present invention, there is provided an attenuator having a series resonance circuit of an inductor and a capacitor connected between input and output terminals. Loss can be achieved.

[0008] The attenuator according to the second aspect is the first aspect of the invention.
The attenuator described above includes a parallel resonance circuit formed with an inductor and a capacitor, and attenuates an RF signal in a required frequency band by the parallel resonance.

A third aspect of the present invention provides an attenuator.
The attenuator described includes a diode connected in the parallel resonance circuit to control resonance, and the Q value of the parallel resonance can be controlled by the diode, resulting in appropriate attenuation.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the attenuator of the present invention will be described below with reference to a variable voltage control type attenuator shown in the drawings.

FIG. 1 is a circuit diagram showing an attenuator according to an embodiment of the present invention. A series resonance circuit of an inductor L1, a capacitor C1 as a capacitor, and an inductor L2 is provided between a high frequency input terminal RF IN and a high frequency output terminal RF OUT. 1 is connected. A series circuit of a capacitor C2 and a diode D1 for controlling parallel resonance is connected in parallel with the inductor L1 to form a parallel resonance circuit 2, and a capacitor C3 and a diode for controlling parallel resonance in parallel with the inductor L2. The parallel resonance circuit 3 is formed by connecting the series circuits of D2.

A resistor R1 is connected to a connection point between the capacitor C2 and the diode D1, a resistor R2 is connected to a connection point between the capacitor C3 and the diode D2, and a control terminal CONT is formed at a connection point between the resistors R1 and R2. Have been.

Further, the high frequency input terminal RF IN is grounded via a series circuit of a matching diode D3 and a resistor R3, and the high frequency output terminal RF OUT is grounded via a series circuit of a matching diode D4 and a resistor R4. One end of the capacitor C1 is grounded via a signal shunt diode D5, and the other end is also grounded via a signal shunt diode D6.

Next, the operation of the above embodiment will be described.

First, when a control current is supplied from the control terminal CONT, a series resonance occurs in the series resonance circuit 1 of the inductor L1, the capacitor C1, and the inductor L2 according to the control current, and a parallel resonance of the inductor L1, the capacitor C2, and the diode D1 occurs. The circuit 2 resonates in parallel, the inductor L2, the capacitor C3, and the diode D2 resonate in parallel. The high frequency input from the high frequency input terminal RF IN is attenuated by a predetermined amount, and the high frequency output terminal
Output from RF OUT.

Further, since only the series resonance circuit 1 of the inductor L1, the capacitor C1 and the inductor L2 is connected between the high-frequency input terminal RF IN and the high-frequency output terminal RF OUT, when a diode or the like is connected. In comparison, the insertion loss can be greatly reduced.

Note that the diodes D1 to D6 of the above embodiment
Is P according to the insertion loss or attenuation level.
Any of an IN diode, a PN junction diode, a Schottky diode, or the like can be used, and the connection is not limited to the above-described embodiment, and may be a π type or a T type.

[0018]

According to the attenuator of the first aspect,
By providing a series resonance circuit of an inductor and a capacitor connected between the input and output terminals, a series resonance circuit is formed between the input and output terminals, and low insertion loss can be achieved.

According to the attenuator according to the second aspect, in addition to the attenuator according to the first aspect, a parallel resonance circuit formed together with any one of an inductor and a capacitor is provided, so that a required frequency is attenuated by parallel resonance. it can.

According to the attenuator according to the third aspect, in addition to the attenuator according to the second aspect, since a diode connected to the parallel resonance circuit and controlling resonance is provided, the Q value of the parallel resonance can be controlled by the diode. Can be attenuated appropriately.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an attenuator according to the present invention.

FIG. 2 is a graph showing a relationship between frequency, attenuation, and bias current.

[Explanation of symbols]

 1. Series resonant circuit 2, 3 Parallel resonant circuit C1 Capacitors D1, D2 Diode L1, L2 Inductor

Claims (3)

[Claims] 1. An attenuator comprising: a series resonance circuit of an inductor and a capacitor connected between an input / output terminal. 2. The attenuator according to claim 1, further comprising a parallel resonance circuit formed together with the inductor and the capacitor. 3. The attenuator according to claim 2, further comprising a diode connected in the parallel resonance circuit to control resonance.