JPS60112306A - Electronic attanuator - Google Patents

Abstract

PURPOSE:To attain a simplified AGC circuit having a large amount of attenuation over a wide range by arranging four PIN diodes into two L-shaped circuits in terms of DC with addition of a drive circuit to each circuit and producing a DC bias corresponding to a prescribed control signal to actuate said drive circuit. CONSTITUTION:DC preventing capacitors 13-15 are provided between an input terminal 11 and an output terminal 12, and the 1st and 2nd PIN diodes D1 and D2 are connected in series to each other and in terms of a high frequency. An electronic attenuator contains a DC arm part including the diode D1 and D2 and a parallel arm part containing the 3rd PIN diode D3 which is earthed via a capacitor 16 and in terms of a high frequency and the 4th PIN diode D4 which is earthed via a capacitor 17 in terms of a high frequency. The high frequency resistance Rd of each of diodes D1-D4 is decided by the bias currents sent from drive circuits 23 and 24 which drive the diodes D1 and D3 and well as D2 and D4 independently of each other and in terms of DC. The resistance Rd is controlled by an AGC signal which is applied to each drive circuit. Therefore a high frequency signal supplied to an input terminal 11 is delivered through the terminal 12 after undergoing the control of attenuation with the AGC signal.

Description

TECHNICAL FIELD The present invention relates to an electronic attenuator using all PIN diodes, and particularly to an electronic attenuator suitable for UHF and 5) JF band frequency signal attenuation control.

BACKGROUND TECHNOLOGY In general television tuners, the RF increase is 1i stage.
G and c are applied and the high frequency signal to the input terminal fluctuates? It's in control. For example, the operating point of the RFF width element is completely changed and the AGO is driven in a forward or reverse manner.
AGO consisting of one or three diodes in E-type connection, making full use of the Roku-R8 characteristics of PIN diodes.
A circuit was also installed. However, in these AGO circuits, the high frequency signal becomes high and when it reaches the Ul (F band), sufficient attenuation cannot be obtained. Even in the case of a circuit, the amount of attenuation is 2 GHz in the UHF band.
5dB.

It is about 16 dB at 2 GHz, and 3° dB at 2 GHz is required for a BS tuner used in a satellite broadcast receiving system]
3, it was not possible to complete the entire culm. In addition, the drive bias circuit using the E-type diode is complicated and it is difficult to perform satisfactory control. Circuit proposals were requested.

DISCLOSURE OF THE INVENTION Accordingly, the present invention has been proposed in view of the above, and it is an object thereof to provide a new and improved electronic attenuator that utilizes two or more P-N diodes between input and output terminals. .

According to the present invention, two or more P-type N diodes are connected in series between a high-frequency signal input terminal and an output terminal, and a series arm of two or more P-type N diodes is connected in series at high frequency, and a parallel P-type N diode is connected in series at high frequency on each terminal side. Direct current bias from the drive circuit with all arms, all parallel arms? An electronic attenuator is disclosed. Preferably, first and second P-type N diodes are connected in series between the input terminal and the output terminal, the first P-type N diode on the input side and the third P-type N diode inserted in the W ground IJI, and the output. A 40th PIN diode inserted between the second PIN diode on the side and the ground, a first drive circuit that applies bias to the first and third PIN diodes, and a bias applied to the second and 40th PIN diodes. The configuration includes all the second drive circuits, and the direct current signals generated by each drive circuit are used to connect input and output terminals. A Umako attenuator is provided that controls the total attenuation of high frequency signals passing through. Here, the four PIN diodes basically function in the same way as an E-type resistor attenuator, and are equivalent to a π-type attenuator using three resistors, and the amount of attenuation depends on each resistance value. can be determined. In particular, the four P-N diodes are
Each of the L-shaped circuits '#6' has a total drive circuit, and generates and operates a DC bias according to a predetermined control signal.

The electronic attenuator according to the present invention can be applied to the configuration of a π-type attenuator as well as the configuration of a π-type attenuator, and is suitable for U1 (at 1 to 2 GHz in the F band high frequency range) in a BS tuner. It provides a large amount of attenuation and is extremely practical for this type of AGO circuit). Particularly, the present invention is noteworthy in that it was able to obtain the entire attenuation amount of 30 dB at 2 GHz1.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings in comparison with a conventional circuit.

FIG. 1 shows a conventional attenuator using P/N/diodes. In this attenuator, three P-type N-diodes (4) to (6) are inserted in a π-type circuit between the input terminal (1) and the output terminal (2) via a DC blocking capacitor (3). No input from the drive circuit (W) to this evening image.
All damping control is performed by the input. Drive circuit (7)
consists of a transistor (8) whose drive is controlled by the voltage at the B terminal and signals from the AGO and % terminals, and the resistance of the diodes (4) to (6) is changed by the output current of the transistor (8). Automatic attenuation control is performed in accordance with the AGO signal of the high frequency signal. However, in such a circuit configuration, the IGH2c high frequency signal is 256. B, 20Hz (1
) Attenuation amount of 16d,B for high IAJ wave signal? I know I'll get it.

In the desired reception band of 1.40H2 to 2 GHz, it was extremely difficult to obtain a total attenuation of 30d8.

Figure 2 shows an electronic IT system according to the present invention that eliminates all the drawbacks of Figure 1.
It is a two-attenuator, and includes first and second P-type N diodes (1 and 2) connected in a high-frequency KM series with a DC blocking capacitor (1) interposed between the input terminal (11) and the output terminal (12).
Dl) (Dl) (Dl) DC arm part including all of the input terminal side, one end is fully connected to the input terminal side P N diode)" (DI), and the other end is all connected to the third capacitor (16), which is grounded at high frequency. P engineering N
One end is connected to the diode (Dl) and the second P-N diode (Dl) on the output terminal side, and the other end? Capacitor (17
) The fourth P-type N diode (
D4) Parallel arm portion including all the above-mentioned four P-type N diodes (Dl) to (D4) Drive means (2) using an AGO signal that biases all of them. Drive means (2)
One is the common At]O terminal C and the second drive circuit f23) connected to the drive power supply terminal (22).
24) and two diodes (DI) (Dl) or (Dl) (D4) connected in an L shape, respectively, and AG
Apply the full bias according to the O signal. Each drive circuit (
23) (24) n each transistor (Trl)
(Tr2) is a DC drive circuit that includes all resistors and choke coils, and the high frequency resistance (■ a-Ra characteristics) of the diode that occurs in response to the diode bias current flowing into each P-type N diode (Dl) to (D4). It is used to control the amount of attenuation of high-frequency signals.

The characteristics of the present invention are that the total resistance values (R1) to (R3) in the fF type resistance attenuator shown in FIG.
It is obtained by ~(D4), and is the component of resistance value (R2)? The operation will be explained as replacing two diodes (DI) (D2) connected in series. Here, the high frequency resistance (Rd) id of each P etdiode (Dl) to (D4)
, the P-type 1q diode (DI) (D3) and the PIN diode (D2) (D4) are determined by the bias current from the drive circuit ["3) +24) in Figure 2, which cuts off and drives each of the PIN diodes (D2) (D4). , AG to each drive circuit
It is controlled by the O signal. Therefore, the high frequency signal input to the input terminal Q is attenuated by the AGO signal and output terminal (
] → can be derived from the formula.

The amount of attenuation at this time is about 30 dB up to 2GH2 in the specific circuit of the present invention, and compared to the conventional circuit shown in FIG. 1, the B circuit uses transistors as active elements. Did you use a large AGO current? It is preferable to use FIT to obtain EL.

The haa signal is used in a reverse format, but an inverter can be added to it to create a forward format. As yet another specific example, the attenuation circuit of the present invention using the diode connection method can be formed as the entire basic configuration of a π-type resistive attenuator using the f equivalent circuit shown in FIGS. 5 to 7. That is, the three resistance values (R4) of the π-type resistance attenuator in FIG.
~(R6) can be considered as a direct current with the ε blocking capacitor (C1) all intervening, as shown in FIG.
It is clear that it can be constructed by Dl) to (D4) and a DC blocking capacitor (01). Specifically, P in Figure 2
The connection direction of the XN diodes (Dl) to (D4) may be changed, and the operation can be explained as the overall basic configuration of a π-type resistive attenuator.

In particular, since the present invention is intended to increase the attenuation of the series arm portion between the input and output terminals, direct current is applied to two or more series-connected P/N diodes under a common driver circuit. It is only necessary to apply it to the base, and various modifications are possible.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional E-type P-N diode attenuator.
Fig. 2 is a circuit diagram of the electronic attenuator of the present invention, Fig. 3 is a circuit diagram of the π-type resistive attenuator explained in Fig. 2, Fig. 4 is a high frequency equivalent circuit diagram of Fig. 2, and Fig. 5 is an illustration of the FIG. 6 is a modified circuit diagram of FIG. 5, and FIG. 7 is a high frequency equivalent circuit diagram of a specific example of the present invention. (IX)-・ Input terminal (12)・ Output terminal (13) (14) (IQ (]F+) (17)・
・・DC blocking capacitor (2 → (24) ・Drive circuit (Trl) (“rr2) −,,) transistor (DI)
(D2) (D3)<D4)... P-type N diode Patented I Jidai Kansai NEC Co., Ltd. Figure 1 AC3C Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1) A series arm in which two or more P-type N diodes are connected in series at high frequency between an input terminal and an output terminal, and a P-type N diode connected in series at high frequency on each side of the input and output terminals; Parallel arm connected to ground? DC bias is applied to the P-type N diode in the series arm through all the P-type N diodes in the parallel arm. Have you tried controlling the total attenuation of the input signal? Features: Electronic attenuator. 2) The series arm includes a first (1) P-type N diode, a DC blocking capacitor, and a second P-type N diode, and the parallel arm includes a third P-type N diode connected to the first drive circuit.
A fourth P-N diode connected to a diode and a second drive circuit, the attenuation degree being controlled by DC signals generated by the first and second drive circuits. electronic attenuator.