JPH084734Y2 - Multi-stage attenuator - Google Patents

Description

Field of the Invention The present invention relates to a signal change amount control circuit for controlling a change amount of a signal.

2. Description of the Related Art Conventionally, a multi-stage attenuator is known as a means for controlling a signal change amount by a remote method to obtain a desired signal level. As an example, Fig. 3 shows a three-stage attenuator, which has 0.1 dB steps, 1 dB steps, and 10 dB steps.
It has three attenuation stages connected in series with dB steps. As can be seen from the figure, four relays R _{1 to} R ₄ are used in the 10 dB step attenuation stage.
B, 20 dB (not shown), 40 dB (not shown), and 80 dB π-type attenuators are appropriately switched and connected according to the control signal. In other minute attenuation stages of 0.1 dB and 1 dB steps, analog switches are used instead of short-life relays.
S ₁ and S ₂ are used, so that 0 of the L-type attenuator is used.
One of ˜0.9 dB attenuation output and one of 0 to 9 dB attenuation output are switched and selected according to the control signal. In the stages using these analog switches, the output of those switches must be received with high impedance because of the current-resistance characteristics of the analog switches, and therefore buffer amplifiers BA ₁ and B ₁
A ₂ is provided.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the multi-stage attenuator having the above configuration, signal change amount control is performed using only the damping action. For this reason, the stage using the analog switch has a drawback in that it requires one amplifier only for the purpose of signal buffering, which increases the cost. Furthermore, amplifiers are a major source of noise generation, and circuit structures that must be used one for each of these stages are undesirable.

Therefore, an object of the present invention is to provide a signal change amount control circuit having a simple circuit configuration without the above-mentioned drawbacks.

Means and Actions for Solving the Problems To achieve the above-mentioned object, the signal change amount control circuit of the present invention, as shown in FIG. 1, has a first change amount control for an input signal as a first stage. A first change amount control variable attenuating means 10 for performing, and a second amplifying means 20 and a second change amount controlling means 22 for performing a second change amount control on an output signal from the means 10 as a second stage, Is equipped with. The differential amplification means 20 and the second change amount control means 22 constitute a variable gain control stage. The differential amplifying means 20 has a variable attenuating means at its non-inverting input terminal.
The output from the amplifying means 20 is connected to the inverting input terminal so as to receive the output from the amplifying means 20 via the second change amount controlling means 22. Further, if necessary, the third change amount control variable damping means 30 for performing the third change amount control may be provided.

In the control circuit of the present invention having such a configuration, the change amount control of at least two stages is performed by the combination of the damping action and the amplifying action, and further the second stage differential amplifying means 20 causes the first stage damping. The output from the means 10 is buffered and the variable amplification is performed. As a result, each variation control stage does not need an amplifier only for signal buffering.

When the attenuation control is performed by the signal change control circuit of FIG. 1, fixed attenuation means is provided at the position of the block 40 ', the block 40 ", or the block 40 shown by the dotted line in FIG. 1, for example. Then, the attenuation amount control circuit or the attenuator can be configured by attenuating only the amount amplified by the differential amplifying means 20.

Embodiment FIG. 2 shows a three-stage attenuator to which the variation control circuit of the present invention is applied. This attenuator is the first
The first change amount control variable attenuation means 10 of 1 dB step or change rate is used as a stage, and the differential amplification means 20 and
The second change amount control means 22 of 0.1 dB step is provided.
The differential amplification means 20 and the variation control means 22 constitute a 0.1 dB step variable gain amplification stage.

More specifically, the 1 dB step variable attenuating means 10 is an L-type attenuator 12 having a terminal connected between the input terminal 2 and the ground to generate an attenuation output of 0 dB to 9 dB in 1 dB steps.
And an analog switch AS ₁ that operates to select any one of these 0 dB to 9 dB attenuation outputs, and a driver 14 with a decoder that controls the switching operation of this switch AS ₁ .
It has. Signals D _{10 to} D input to this driver 14
Reference numeral ₁₃ is a binary signal representing an attenuation amount of 1 dB, and the driver with a decoder decodes this binary signal and outputs a control signal for switching and selecting the analog switch AS ₁ to the designated attenuation amount output terminal. appear. As a result, the analog switch AS ₁ passes the output of the designated attenuation amount on its output side.

In the next stage, the differential amplifying means 20 is connected to the non-inverting input terminal so as to receive the output from the analog switch AS ₁ , and a feedback is provided between the output of this amplifying means and the inverting input terminal. The circuit portion, that is, the 0.1 dB step second change amount control means 22 is connected, and constitutes the 0.1 dB step variable gain amplification stage as described above. This feedback circuit section is provided with a resistor R _F and an L-type attenuator 24 which are connected in series between the output of the amplifying means 20 and the ground, and further this L-type attenuator 24.
It has an analog switch AS ₂ which can be switched to any one of the output terminals labeled 0 dB to 0.9 dB and whose output side is connected to the inverting input terminal of the amplifying means 20. Analog switch AS ₂ is a driver with decoder, similar to switch AS ₁ .
Controlled by 26, it receives the decode output of the binary signals D _{01 to} D ₀₃ designating the amount of change of the digit of 0.1 dB as a switching control signal. For example, when the binary signal specifies a change amount of 0.2 dB, the analog switch AS ₂ is controlled to switch from the output terminal of the attenuator labeled 0 dB to the output terminal of 0.2 dB.

The gain of the amplifying means 20 connected as described above has a resistance value R _A including a resistor R _F connected between the inverting input terminal and the amplifier output, and between the inverting input terminal and ground. When the resistance value is R _B , it is expressed by (R _A + R _B ) / R _B. As you can see, the gain is greater than 1, and R _A / R _B
When the terminal with 0dB of the attenuator that maximizes is selected, the gain becomes maximum, and from that, 0.1dB, 0.2dB, ...
The gain decreases toward the 0.9 dB terminal, and an output attenuated by 0.1 dB, 0.2 dB, etc. is generated at the output of the amplifying means 20 with reference to the output when the 0 dB terminal is selected. Note that the gain is larger than 1 even when the 0.9 dB terminal that minimizes R _A / R _B is selected. In this way, the 0.1dB step variable amplification stage increases by a fixed ratio (that is, the gain when the 0dB terminal is selected) with respect to the received input, but the 0.1dB step 0 to 0.9dB change or attenuation output Can occur.

Variable attenuation means for controlling the third variation in 10 dB step at the final stage
30 is a circuit similar to the conventional relay type, 10 dB, 20 dB
(Not shown), 40 dB (not shown), and 80 dB π-type attenuators 32-34 are combined to obtain a specified amount of attenuation. Therefore, the four relays RS _{1 to} RS ₄ have their respective relay windings RW
Attenuation amount designation binary signal D _{20 to} D of 10 dB given to _{1 to} RW _4.
Connect an attenuator that is activated by ₂₃ , which results in the specified attenuation.

Next, the operation of the entire attenuator of FIG. 2 will be described. For example, to obtain an attenuation signal of 89.2 dB, analog switch AS ₁ is switched to connect to the 9 dB terminal of attenuator 12, analog switch AS ₂ is switched to the 0.2 dB terminal of attenuator 24, and relay RS ₄ Is activated 80 dB attenuator 3
4 is connected to the circuit. The amplifying means 20 connected to the output side of the analog switch AS ₁ buffers the output from the switch AS ₁ due to its high input impedance. This allows
It is possible to avoid the influence of the current-resistance characteristic of the analog switch AS ₁ . Further, this amplifying means acts as a variable amplifying means by feedback amount control, and generates a signal whose output is controlled by a change amount of 0.2 dB. This signal is attenuated by 80 dB by the next attenuation action by the attenuation means 30.

In this way, the output terminal 4 receives 1d
A signal that has undergone a change amount control of B step, 0.1 dB step, and 10 dB step can be obtained. The level of the output signal is not the amount of attenuation designated by the binary signal with respect to the level of the input signal because the amount of change is controlled by the amplifying action of the variable amplification stage. However, this can be calibrated by providing fixed damping means, a voltage divider, etc. in the output terminal 4 or in the attenuator circuit. For example, in the circuit shown in FIG. 2, a π-type attenuator or a series resistor is connected to the position of the dotted line block 40 ', a π-type attenuator is connected to the position of the dotted line block 40 ", or Block of 40
The calibration means can be provided by connecting a π-type attenuator or a resistance voltage divider at the position. As a result, the level of the output signal amplified by the amplifying action of the variable amplification stage can be attenuated so as to be the attenuation amount specified by the binary signal with respect to the input level. In addition, in the connection of the calibration means, since the attenuation amount is not variable but fixed, a buffer amplifier for buffering is not required, and therefore the number of amplifiers provided in the attenuator does not increase.

Although one embodiment of the present invention has been described above, the following modifications can be made in this embodiment. First, in the above-described embodiment, in order to minimize the distortion due to the amplifier characteristics and perform more accurate change amount control, the change amount control in the minimum step of 0.1 dB is connected to the second change amount control means 22. The differential amplifying means 20, that is, the amplifying action is used. However, it is also possible to perform the 0.1 dB minimum step control by the first change amount control variable attenuator 10 and perform the 1 dB step control in the variable amplification stage. Second, a π-type attenuator can be used instead of the L-type attenuator. Third, the resistance values of the attenuators 12, 24 can be modified as appropriate to provide other changing step patterns. The same applies to the attenuators 32-34. The binary signal may be modified accordingly. 1
For example, from 0dB in 0.8dB steps in the first stage 10
Change the attenuator 12 to generate an attenuating output up to 5.6 dB, and in the second stage 20 and 22 in 0.1 dB steps from 0 dB to 0 dB.
Modify attenuator 24 to produce eight outputs up to 7 dB, and in stage three 30, add four attenuators 32-34 respectively.
Attenuation amounts of 6.4 dB, 12.8 dB, 25.6 dB and 51.2 dB can be given. In this case, the control signal is 2
8 bits D _{0 to} D ₇ are used to control the amount of change of the second stage with D _{0 to} D ₂ , control of the first stage with D _{3 to} D ₅ , and D ₆ and D ₇
Controls the amount of change in the third stage.

Effect According to the signal change amount control circuit of the present invention described in detail above, since the amplifying action is used for the signal change amount control, only the purpose of the signal buffering like the circuit using only the conventional damping action is used. No amplifier is needed. In the present invention, the amplifier to be used controls the amount of change in addition to buffering the signal, so that the amplifier can be used more effectively. Also, the number of amplifiers can be reduced compared to the conventional one,
There are advantages of cost reduction and noise reduction.

[Brief description of drawings]

FIG. 1 is a block diagram showing the basic configuration of the present invention. FIG. 2 is a circuit diagram of a three-stage attenuator which is an embodiment of the present invention. FIG. 3 is a circuit diagram showing an example of a conventional three-stage attenuator. (Explanation of Codes) 10: First change amount control variable attenuating means 20: Differential amplifying means 22: Second change amount controlling means 30: Third change amount controlling variable attenuating means

Claims (2)

[Scope of utility model registration request] 1. A first attenuation stage that attenuates with a series of attenuation amounts of a first group having a first attenuation amount step pattern, and an attenuation amount step in the first attenuation amount step pattern have different sizes. A second attenuation stage for performing attenuation with a series of attenuation amounts of a second group having a second attenuation amount step pattern having an attenuation amount step, and the attenuation amount steps of the first and second attenuation amount step patterns A third attenuation stage for performing attenuation with a series of attenuation amounts of a third group having a third attenuation step pattern having attenuation steps of different magnitudes;
A multi-stage attenuator for attenuating an input signal received at an input terminal (2) to generate an attenuated output signal at an output terminal (4), and (b) a first attenuating stage for configuring the first attenuating stage. 1. A change amount control variable attenuating means (10), wherein the first change amount control variable attenuating means is a) connected to the input terminal (2), and changes the magnitude of an input received by the input terminal. An attenuator (12) for determining a series of rate of change of the first group of 1 or less, each of which corresponds to the amount of attenuation of the first group, and b) one of the rate of change of the first group. Switch means (AS1, 14) for changing the magnitude of the input at the selected rate of change and generating this as the first output at the output of the first variable attenuating means. Including the first variation control variable damping means (1
0), and (b) variable amplification means (20, 22), a) a difference having a non-inverting input terminal for receiving the first output, an inverting input terminal, and an output terminal for generating a second output. A dynamic amplifying means (20), and b) is connected between the output terminal and the inverting input terminal of the differential amplifying means, and changes the magnitude of the input to be received by a second group larger than one. An attenuator (24, _RF ) that determines a series of change rates and one change rate of the change rates of the second group are selected, and the magnitude of the first output is changed by the selected change rate. And a second change amount control means (22) including switch means (AS2, 26) for generating this at the output terminal as the second output, and the variable amplification means (20, 22) and c) third variation control variable damping means (30) for constituting the third damping stage, wherein Connected to receive a force, the attenuation amount of the third group in one of the respective matched 1 following the third series of the rate of change of the second
The third variation control variable attenuation means (30), which changes the magnitude of the output and generates the third output, and d) the second amplification in combination with the variable amplification means. At least one in the output terminal of the multistage attenuator or in the circuit of the multistage attenuator to form an attenuation stage
Fixed attenuating means (40 ', 40 ", 40) provided at a position, wherein the rate of change of the second group of the variable amplifying means is equal to or less than 1 which respectively corresponds to the attenuation of the second group. Fixed damping means (4
0 ', 40 ", 40), and a multi-stage attenuator. 2. A multi-stage attenuator according to claim 1, wherein the attenuation amount step of the attenuation amount of the first group is larger than the attenuation amount step of the attenuation amount of the second group, and A multi-stage attenuator characterized in that the attenuation amount of the three groups is smaller than the attenuation amount step.