JP4780909B2 - ALC circuit and radar apparatus using the same - Google Patents

Description

  The present invention relates to an ALC (Auto Level Control) circuit of a variable amplifier used in, for example, a radar apparatus.

  In the conventional ALC circuit of the variable amplifier, in order to converge the output of the variable amplifier to a certain reference value, the output value is compared with the reference value, and if the output value is less than the reference value, the output control signal of the variable amplifier is increased. The variable amplifier is controlled to increase the output value and decrease the output value when the output value exceeds the reference value. (For example, refer to Patent Document 1).

JP 2002-32119 A (FIG. 1)

  In general, the input / output characteristics of a variable amplifier are a region where the output increases linearly (linear characteristic region) as the input or output control signal increases, a region where the output increases but is not linear (saturation characteristic region), and It has an area where the output drops (supersaturation characteristic area). It is known that these characteristic regions change depending on the frequency of the signal targeted by the variable amplifier.

  In the conventional variable amplifier ALC circuit, as described above, the output value is simply increased if the output value of the variable amplifier is less than or equal to the reference value, and the output value is decreased if it exceeds the reference value. Therefore, when the variable amplifier enters the supersaturation characteristic region where the output is attenuated in an attempt to increase the output at a certain control stage, if the output value at that time is below the reference value, the output of the variable amplifier is further increased. Increase the output control signal of the variable amplifier. However, since the variable amplifier is in the supersaturation characteristic region, even if the output control signal is increased, the output of the variable amplifier does not increase. On the other hand, the variable amplifier decreases and deviates from the reference value, and the ALC operation cannot be performed normally. was there.

For example, in a radar device that captures a target, the S / N ratio (signal-to-noise ratio) at the time of reception needs to be maintained at a certain level or higher. Therefore, when the target is far away, the output power should be raised to the performance limit. There is.
In particular, radar devices for on-board use are required to be smaller, lighter, and of course lower in cost, and there is a limit to the performance of components used for variable amplifiers. In such a situation, when the frequency range of the signal to be used is wide (for example, several GHz to several tens GHz, etc.), it may enter the supersaturation characteristic region depending on the restriction of the frequency characteristics of the parts to be used. Has become apparent.

  The present invention has been made to solve the above-described problems, and an ALC circuit capable of normally performing an ALC operation even if it has a supersaturation characteristic depending on the frequency range of a signal targeted by a variable amplifier. Is to provide.

An ALC circuit according to the present invention amplifies an input signal according to an output control signal and outputs the amplified signal as an output signal, a reference value determined to keep the level of the output signal within a certain range, and the output A signal level comparator that compares a signal level and outputs a comparison result indicating a magnitude relationship between the level of the output signal and the reference value, and the comparison result indicates that the level of the output signal is smaller than the reference value. A control value having a value for increasing the level of the output signal is output if it is indicated, and a control value having a value for decreasing the level of the output signal is output if the level of the output signal is greater than the reference value. The control value is compared with a set value set as an upper limit at which the output characteristic of the variable amplifier does not become an oversaturated characteristic, and the control value is set to the set value. The control value if the value below, if the control value is equal to or greater than the set value and a signal selector for outputting the set value as the output control signal for the variable amplifier, is output from the control circuit the The maximum output value of the control value is P, and the control value of the (n) th control stage in the control circuit is
(N) control value = (n-1) control value + P / 2 ⁿ
And when the control circuit wants to increase the level of the output signal as the control value of the (n + 1) th control stage,
(N + 1) th control value = nth control value + P / 2 ^{n + 1}
If you want to reduce the level of the output signal,
(N + 1) th control value = nth control value−P / 2 ^{n + 1}
(Here, n is an integer of 1 or more, and the 0th control value is 0.)
Is output .

  According to the present invention, the ALC operation can always be normally performed even with a variable amplifier having a supersaturation characteristic depending on the frequency range of the target signal.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an ALC circuit according to Embodiment 1 of the present invention. The variable amplifier 1 receives the input signal 11 and outputs a signal amplified by the output control signal 13. The signal distributor 2 branches a part of the output of the variable amplifier 1 and the signal level detector 3 detects the magnitude. The signal level comparator 4 compares the output of the signal level detector 3 with a reference value 5 that is a preset target value of the output signal 12, and controls if the output of the signal level detector 3 is less than the reference value 5. An instruction to increase the output of the variable amplifier 1 (hereinafter referred to as “+ instruction”) is output to the circuit 6, and an output attenuation instruction (hereinafter referred to as “− instruction”) is output when the reference value 5 is exceeded.

  The control circuit 6 outputs a control value 14 calculated by a predetermined calculation described later in accordance with a + instruction or − instruction from the signal level comparator 4 in a state where the ALC operation instruction signal 15 is valid. The signal selector 8 compares the control value 14 from the control circuit 6 with the set value 7 and selects the smaller one to obtain the output control signal 13 for the variable amplifier 1.

FIG. 2 is a diagram showing the vicinity of the output characteristic curve of the variable amplifier 1 changing from a linear characteristic region to a saturation characteristic region, and further to a supersaturation characteristic region. This is the magnitude of the output control signal 13 for controlling. For example, the output signal 12 of the output control signal 13 to the X _A when taking an input signal 11 value becomes Y _A. When performing ALC operation the reference value was _{Y CE} in this state, _{Y A} increases the control signal 13 so as to increase the output signal 12 is smaller than the _{Y CE.} However, the output signal 12 increases as the control signal 13 increases, but the increase gradually slows down, indicating that the output becomes a supersaturated characteristic region where the output decreases from point D.

  Next, the operation will be described. In the following description, it is assumed that the variable amplifier 1 has a characteristic that the output increases as the output control signal 13 increases. In FIG. 1, when a certain reference value 5 and an ALC operation instruction signal 15 are given, this ALC circuit performs an ALC operation for adjusting the output signal 12 to the given reference value 5. Since the distribution ratio of the distributor 2 is always constant, it goes without saying that the magnitude detected by the signal level detector 3 corresponds to the magnitude of the output signal 12. Therefore, comparing the output of the signal level detector 3 with the reference value 5 by the signal level comparator 4 is nothing other than comparing the output signal 12 with the reference value 5.

Now, assume that a state in which a certain control stage is completed is point A in FIG. Since the output value YA at the point _A is smaller than the reference value _YCE , the signal level comparator 4 in FIG. The control circuit 6 outputs a control value 14 calculated in accordance with the + instruction. The control value 14 is obtained by adding a value calculated by a predetermined calculation as described later to the control value at the point A. . Since the positional relationship between the current point A and the reference value C in FIG. 2 is not included in the calculation of the control value 14, the value to be added depends on the difference between the points E and A on the X axis in FIG. When it becomes a large value, the control value 14 calculated is greater than the point E in the supersaturated characteristic area, for example becomes X _B. Since the conventional ALC circuit is controlled by the point B, point B as shown in FIG. 2 for a value smaller than the reference value Y _CE, in the signal level comparator 4 is also the next control step + instruction is made, further It will move away from the reference value.

However, in the present invention, the signal selector 8 compares the control value 14 with the set value 7 and selects the smaller one as the output control signal 13. Here, when set to any value in the range of X _CE in Figure 2 as a set value 7, when the control value 14 as described above is X _B are outputs X _B is less than set value 7, signal selector 8 The control signal 13 is selected and input to the variable amplifier 1. As a result, the output when the set value 7 is used as a control input is any one of points C to E on the characteristic curve of FIG.

In this range, since the reference value _YCE is exceeded, the signal level comparator 4 gives a − instruction in the next control stage, and the control circuit 6 performs a calculation according to the − instruction and outputs a control value 14. As described above, in the control circuit 6, even when the variable amplifier 1 enters the supersaturation characteristic region due to the control value 14 output at a certain control stage and the actual output decreases to become the reference value 5 or less, the output control signal 13 is output. By setting the value corresponding to a value exceeding the reference value 5, it is possible to perform the ALC operation as if it does not have supersaturation characteristics, and it is possible to reliably converge to the reference value.

A method for obtaining the set value 7 will be described below. As described above, the set value of 7 but may be set to any value in the range of X _CE of FIG. 2, since the reference value Y _CE is different in some cases to use, for example, radar equipment, also changes X _CE. However, the maximum value of the output used in the radar device is naturally determined as a specification. Since the point at which the variable amplifier saturates (point D in FIG. 2) can be obtained in advance by a characteristic test, the value between the maximum output value and the point D may be set as the set value 7. It is impossible to produce an output larger than the point D, and the maximum value of the output is determined below the point D.

The control value 14 output by the control circuit 6 can be converged to the reference value 5 by calculating, for example, as follows.
Let P be the dynamic range of the output of the control circuit 6 (the maximum output width that can be output). When the ALC operation instruction 15 is input to the control circuit 6, the control circuit 6 outputs P / 2 as the first control value (initial value) of the control value 14. The variable amplifier 1 outputs corresponding to this value and is compared with the reference value 5 by the signal level comparator 4 via the signal distributor 2 and the signal level detector 3. Control is performed according to the comparison result, but a control value at a certain control stage (this is referred to as an nth control value)
(N-1) control value + P / 2 ⁿ (1)
The (n + 1) th control value when there is a + instruction from the signal level comparator 4 is
(N-1) control value + P / 2 ⁿ + P / 2 ^{n + 1} ... (2)
Alternatively, the (n + 1) th control value when the signal level comparator 4 gives a − instruction is
(N-1) control value + P / 2 ^{n + 1} (3)
And However, n is an integer equal to or greater than 1, and the 0th control value is 0. Naturally, the ALC operation ends when the output signal 12 converges to the reference value 5.

The meaning of the above formula is as follows.
First, as described above, the initial value (first control value) for performing the ALC operation is P / 2 from equation (1), where n = 1. This is half the dynamic range of the output of the control circuit 6. Assuming that this is an initial value, when the output of the variable amplifier 1 is increased next time, the second control value is as follows from the equation (2):
2nd control value = 0th control value + P / 2 + P / 4
= P / 2 + P / 4 (because the 0th control value = 0)
It becomes. That is, half of the initial value is added.
If the reference value 5 is set to a value corresponding to P, the control for increasing the output of the variable amplifier 1 is continued, and the control value is
P / 2 + P / 4 + P / 8 + P / 16 +... P / 2 ⁿ
And eventually converge to P. This situation is shown in FIG.

Further, when the reference value 5 is set to be equal to or less than the value corresponding to P, when the value of the output signal 12 exceeds the reference value 5 and the output of the variable amplifier 1 needs to be attenuated on the way, As shown in the drawing, instead of P / 2 ⁿ added when control exceeding the reference value 5 is performed, a half value P / 2 ^{n + 1} is added and a comparison operation is performed. The reason why P / 2 is set as the initial value is that the output value 12 and the reference value 5 of the variable amplifier 1 are not determined. Therefore, it is most reasonable to set the intermediate value first and start the convergence calculation. Because there is. Of course, it goes without saying that the dynamic ranges of the output unit of the control circuit 6, the input / output unit of the signal selector 8, and the input unit of the output control signal 13 of the variable amplifier 1 are designed with consistency.
The above calculation method is called a successive approximation calculation method and is used as a basic calculation method for A / D conversion and D / A conversion, and further detailed description is omitted.

  According to the first embodiment, the ALC operation can always be normally performed even with a variable amplifier having a supersaturation characteristic depending on the frequency range of the target signal.

Embodiment 2. FIG.
In the first embodiment, the signals and operations in the control circuit 6 and the signal selector 8 have been described as analog signals and analog operations, but may be realized by digital signals and digital operations. The embodiment will be described with reference to FIG.
In FIG. 4, the control circuit 6 outputs a control value 14 as a digital value based on an instruction from the signal level comparator 4. The signal selector 8 compares the control value 14 from the control circuit 6 with the set value 7, selects the smaller one, and outputs it to the D / A converter 9 as a digital value. The D / A converter 9 inputs an output control signal 13 obtained by converting the digital signal from the signal selector 8 into an analog signal to the variable amplifier 1.

Next, the operation will be described with respect to differences from the first embodiment. When the ALC operation instruction 15 is input, the control circuit 6 outputs 2 ^m−1 as an initial value (first control value). Here, m represents the number of bits of the D / A converter 9. When the number of bits of the D / A converter is m, the dynamic range of the output of the D / A converter 9 is represented by 2 ^m −1. For example, in the case of a 4-bit D / A converter, the dynamic range is 2 ⁴ −1 = 15, that is, (1111). In this case, 2 ^4-1 = 2 ³ = 8 is a value close to 7.5 which is half of 15. Therefore, 2 ^m-1 corresponds to approximately half of the dynamic range.

The signal selector 8 selects the smaller one of the control value 14 and the set value 7 of the control circuit 6 and outputs it to the D / A converter 9. The D / A converter 9 converts the input digital value into an analog value and inputs it to the variable amplifier 1 as the output control signal 13. The subsequent operation is the same as that of the first embodiment, but when a + instruction is issued to the control circuit 6 from the comparison result in the signal level comparator 4, the control circuit 6 sets the next control value (second control value) as A value (2 ^m−1 +2 ^m−2 ) obtained by adding half (2 ^m−2 ) to the first control value (2 ^m−1 ), or in the case of − instruction, the first control value (2 ^m−1) 2 ^m−2 , which is half of the above), is output as a control value.

Thereafter, the control operation is continued, and the control value of the nth control stage (this is referred to as the nth control value)
((N-1) control value) +2 ^m-n
When the output level is to be increased as the (n + 1) th control value,
((N−1) th control value) +2 ^m−n +2 ^m−n−1
If you want to reduce the output level,
((N-1) control value) +2 ^m-n-1
It can be expressed as. However, n is 1 or more, is an integer of n ≦ m, and the 0th control value is 0. That is, the control value of n = 1 is an initial value and is 2 ^{m−1 as} described above.
Since the operations of the signal distributor 2, the signal level detector 3, the signal level comparator 4, and the signal selector 8 and the control operation in the supersaturation characteristic region of the variable amplifier are the same as those in the first embodiment, the description thereof is omitted here.

  According to the second embodiment, depending on the frequency range of the target signal, even a variable amplifier having a supersaturation characteristic can always perform the ALC operation normally, and the signals in the control circuit 6 and the signal selector 8 In addition, since the calculation is realized digitally, a highly reliable ALC circuit with little secular change can be obtained.

Embodiment 3 FIG.
In the first and second embodiments, it is necessary to set the preset value 7 in advance and store it in a dip switch or memory, and the third embodiment that can be automatically set will be described with reference to FIG.
FIG. 5 is a block diagram showing the third embodiment. When the input / output characteristic sampling instruction 16 is validated, the control circuit 6 outputs that fact to the signal selector 8 and the counter 10. Then, the counter 10 starts a count operation so as to sequentially increase from the initial value 0 and outputs the count value to the signal selector 8, and the signal selector 8 selects the signal from the counter 10 and selects the D / A converter. Output to 9. At this time, the update time of the count value is longer than the response time until the result of the signal level comparator 4 is output from the D / A converter 9 to the control circuit 6. The reason for this is to ensure that the control result obtained by the output counter value is input to the control circuit 6. The reference value 5 is set to the maximum output value determined by the specification as described above.

The count operation is continued while the output of the variable amplifier 1 is below the reference value 5, that is, while the + instruction is received from the signal level comparator 4, but when the -instruction is detected, that is, the variable amplifier 1 When the output 12 exceeds the reference value 5, the counter 10 holds the counter value at that time and sets it as the set value. This setting value is any as long as between the range X _CE of point C ~E points in FIG. 2 as described in the first embodiment may be a set value counter value when it exceeds the reference value 5 That is reasonable. The count width of the counter value may be determined sufficiently finely so as not to exceed the point E when the output signal 12 exceeds the reference value 5. After the set value is detected, the control circuit 6 invalidates the input / output characteristics collection instruction to the signal selector 8 and the counter 10, and when the ALC operation signal 15 is input thereafter, each of the above-described embodiments. The ALC operation described in (1) is performed.

The input / output characteristic sampling operation described above is the same as the ALC operation in the sense that the output signal is increased toward the reference value, except that the output control signal 13 is finely set with the counter value and naturally takes a lot of time. Is.
In the above description, the initial value of the counter is set to 0, but any value smaller than the point C in FIG. 2 may be used, and it may be determined in consideration of variations in the input / output characteristics of the ALC circuit.

Further, the counter output is input to the signal selector 8 and the counter value is forcibly selected by the signal selector 8. However, the counter output is directly selected by switching the input of the D / A converter 9. You may make it input into the D / A converter 9. FIG.
Furthermore, although the case where the counter value of the counter 10 is a digital value is shown in the above example, the counter value can be applied to the analog circuit shown in the first embodiment by outputting the counter value as an analog value. is there. In that case, the D / A converter 9 is unnecessary.

According to the third embodiment, even when the supersaturation characteristic region changes due to aging, temperature change, parts change, etc., the ALC circuit that can easily reset the set value by the input / output characteristic sampling instruction is provided. Obtainable.
As described in the above embodiments, the ALC circuit of the present invention can always perform the ALC operation normally in a variable amplifier having a supersaturation characteristic. However, depending on conditions, for example, the frequency range of the target signal Depending on the case, even if the supersaturation characteristic is not exhibited, there is no adverse effect.

It is a block diagram of an ALC circuit showing Embodiment 1 of the present invention. It is a figure which shows the input / output characteristic of the variable amplifier of Embodiment 1 of this invention. It is a figure which shows the change of the control value of Embodiment 1 of this invention. It is a block diagram of the ALC circuit which shows Embodiment 2 of this invention. It is a block diagram of the ALC circuit which shows Embodiment 3 of this invention.

Explanation of symbols

1 variable amplifier, 2 signal distributor, 3 signal level detector, 4 signal level comparator, 5 reference value, 6 control circuit, 7 set value, 8 signal selector, 9 D / A converter, 10 counter, 11 input signal , 12 output signal, 13 output control signal, 14 control value, 15 ALC operation instruction, 16 input / output characteristic sampling instruction.

Claims (4)

A variable amplifier that amplifies an input signal according to an output control signal and outputs the amplified signal as an output signal;
A signal level for comparing a reference value determined to keep the level of the output signal within a certain range with the level of the output signal and outputting a comparison result indicating a magnitude relationship between the level of the output signal and the reference value Comparator,
When the comparison result indicates that the level of the output signal is lower than the reference value, a control value having a value for increasing the level of the output signal is indicated, and when the level of the output signal is higher than the reference value Is a control circuit for outputting a control value having a value for decreasing the level of the output signal,
The control value is compared with a set value set as an upper limit at which the output characteristic of the variable amplifier does not become an oversaturation characteristic. When the control value is less than or equal to the set value, the control value is set, and the control value is the set value. In the above case, a signal selector that outputs the set value as the output control signal for the variable amplifier,
The maximum output value of the control value output from the control circuit is P, and the control value of the (n) th control stage in the control circuit is
(N) control value = (n-1) control value + P / 2 ⁿ
age,
As the control value of the (n + 1) th control stage, the control circuit
If you want to increase the level of the output signal,
(N + 1) th control value = nth control value + P / 2 ^{n + 1}
If you want to reduce the level of the output signal,
(N + 1) th control value = nth control value−P / 2 ^{n + 1}
(Here, n is an integer of 1 or more, and the 0th control value is 0.)
Output,
An ALC circuit characterized by the above. A variable amplifier that amplifies an input signal according to an output control signal and outputs the amplified signal as an output signal;
A signal level for comparing a reference value determined to keep the level of the output signal within a certain range with the level of the output signal and outputting a comparison result indicating a magnitude relationship between the level of the output signal and the reference value Comparator,
When the comparison result indicates that the level of the output signal is lower than the reference value, a control value having a value for increasing the level of the output signal is indicated, and when the level of the output signal is higher than the reference value Is a control circuit for outputting a control value having a value for decreasing the level of the output signal,
The control value is compared with a set value set as an upper limit at which the output characteristic of the variable amplifier does not become an oversaturation characteristic. When the control value is less than or equal to the set value, the control value is set, and the control value is the set value. In the above case, a signal selector that outputs the set value as the output control signal for the variable amplifier,
The control value output from the control circuit and the output control signal output from the signal selector are digital values,
A D / A converter for converting the output control signal into an analog value;
Assuming that the number of bits of the D / A converter is m, the control value of the (n) th control stage in the control circuit is:
(N) control value = (n−1) control value + 2 ^m−n
And
As the control value of the (n + 1) th control stage, the control circuit
If you want to increase the level of the output signal,
(N + 1) th control value = (n) control value + 2 ^m−n−1
If you want to reduce the level of the output signal,
(N + 1) th control value = (n) control value−2 ^m−n−1
(Here, 1 ≦ n ≦ m, and the first (1) control value is 2 ^m−1 .)
Output,
An ALC circuit characterized by the above. It has a counter that starts counting from the initial value 0 and outputs a counter value.
The signal selector outputs the counter value as the output control signal;
The counter sequentially updates the level of the output signal output from the variable amplifier in accordance with the output control signal and the reference value with an update time larger than a response time until the comparison result is output to the control circuit. Increase the counter value,
The control circuit sets the counter value when the level of the output signal exceeds the reference value as the set value,
The ALC circuit according to any one of claims 1 and 2. A radar apparatus using the ALC circuit according to claim 1.

Images