JP4804033B2 - High frequency equalizer - Google Patents

Description

  The present invention relates to a high frequency equalizer including a filter circuit, and more particularly to a high frequency equalizer including a gmC filter whose filter characteristics are determined by a conductance component gm and a capacitor capacitance C.

  Conventionally, in a disk device for reproducing a recording medium such as an optical disk or a magnetic disk, a high-frequency signal converted into data from a signal read from the recording medium or a servo signal for performing servo control is selectively passed. Equipped with a high frequency equalizer. This high frequency equalizer is composed of a multi-order equiripple filter (equilibrium filter) using a plurality of gmC filters whose filter characteristics are set by a conductance component gm and a capacitor capacitance C, and passes a signal of a target frequency. What is to be provided is provided.

The filter characteristic of the gmC filter that is a part of the equi-ripple filter serving as the high-frequency equalizer is determined by the conductance component gm by the traversal conductance amplifier (hereinafter referred to as “gm amplifier”) and the capacitance value C by the capacitor. Is. As such a gmC filter composed of a gm amplifier and a capacitor, a first-order gmC amplifier having an integration circuit between an output terminal and a non-inverting input terminal of the gm amplifier and a buffer at the output terminal is provided. (Patent Document 1).
JP 2003-188682 A

  The high-frequency equalizer configured by the gmC filter is configured as a one-chip semiconductor integrated circuit device, but the conductance component gm and the capacitor capacitance C vary from chip to chip. Therefore, since the time constant due to the conductance component gm and the capacitor capacitance C also varies, the characteristics of the high frequency equalizer vary, and the yield as a product deteriorates. For this reason, conventionally, a reference external clock is always input to the high-frequency equalizer, and the time constant is adjusted according to the conditions under which the high-frequency equalizer is used. However, since an external clock for always adjusting the time constant is input, the power consumption increases and the circuit scale also increases.

  In view of such a problem, an object of the present invention is to provide a high-frequency equalizer capable of adjusting a time constant by adding a simple configuration.

  In order to achieve the above object, a high frequency equalizer according to the present invention is a high frequency equalizer including a gmC filter based on a conductance component and a capacitor capacity, and a current source that supplies current to the gmC filter. A measurement gmC filter for measuring a time constant having a component and a capacitor capacity is provided. A pulse is given to the measurement gmC filter from the outside, and a voltage value output from the measurement gmC filter by the pulse is provided. Accordingly, the current value from the current source is set.

  In such a high-frequency equalizer, the current source is connected to the gmC filter, a first constant current source that supplies a current having a reference current value, and a current that flows to the gmC filter by the first constant current source. A second constant current source connected to the first constant current source to reduce the value, and a first constant current source to increase a current value flowing through the gmC filter by the first constant current source. A third constant current source; a first switch connected between the first constant current source and the second constant current source; and a connection between the first constant current source and the third constant current source. And when the measurement gmC filter is measured to have a large time constant, the first switch is turned on and the measurement gmC filter is measured to have a small time constant. When the second It may be as to turn ON the switch.

  At this time, a plurality of the second constant current sources are provided, the second constant current sources are connected in parallel, a plurality of the third constant current sources are provided, and the third constant current sources are connected in parallel. A plurality of the first and second switches may be connected to the second and third constant current sources, respectively.

  The switch may be a fuse, and the first and second switches may be turned off by being physically cut. The switch may be a copper wire pattern. The first and second switches may be turned on by connecting them.

  The current value from the current source may be set by inputting a control signal indicating the current value flowing from the current source from the outside. At this time, the control signal may be stored externally as a digital signal, and the first and second switches may be ON / OFF controlled.

  Also, a digital signal control signal indicating a current value flowing from the current source input from the outside may be converted into an analog signal and supplied to the current source. At this time, the control signal is stored externally as a digital signal. The current value may be controlled by a voltage value of an analog signal converted from the control signal.

  In these high-frequency equalizers, the measurement gmC filter includes a traversal conductance amplifier to which a predetermined voltage is input, and a capacitor having one end connected to the output terminal of the traversal conductance amplifier and a DC voltage applied to the other end. And a switch that is turned off when one end is connected to a connection node between the traversal conductance amplifier and the capacitor and the DC voltage is applied to the other end and a reference pulse is applied thereto, and the reference pulse The current value from the current source may be set by the voltage appearing at the connection node between the traversal conductance amplifier and the capacitor when.

  According to the present invention, by providing the measurement gmC filter, the time constant of the gmC filter can be measured based on the voltage value output from the measurement gmC filter. And based on the measured gmC filter, the electric current value of a current source can be set and the target time constant can be given to a gmC filter. Thus, according to the present invention, the time constant of the gmC filter can be measured and the time constant can be easily adjusted by adding a simple configuration called a measurement gmC filter.

<First Embodiment>
A first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an internal configuration of a high-frequency equalizer and a time-constant adjusting device that adjusts the time constant of the high-frequency equalizer according to the present embodiment.

  As shown in FIG. 1, the high-frequency equalizer 1 of the present embodiment includes an input terminal IN1 to which a high-frequency signal is input, and a slave equiripple that passes a target frequency signal from the high-frequency signal input from the input terminal IN1. A filter 11, a variable current source 12 for setting a current value to be supplied to the equiripple filter 11, an input terminal IN2 to which a reference pulse given at the time constant adjustment is input, and an input terminal IN2 A master equiripple filter 13 that operates by a pulse signal, an output terminal OUT1 that outputs a signal that has passed through the equiripple filter 11, and an output terminal OUT2 that outputs a signal generated by the equiripple filter 13 are provided.

  Further, as shown in FIG. 1, the time constant adjusting device 2 includes an input terminal IN3 to which a signal output from the output terminal OUT2 of the high frequency equalizer 1 is input, a variable voltage source 21 capable of switching a voltage value, A comparator 22 that compares the signal from the equiripple filter 13 input from the input terminal IN3 with the voltage value from the variable voltage source 21, and the voltage value from the variable voltage source 21 are switched and given from the comparator 22. The current value setting unit 23 that sets the current value of the variable current source 12 according to the received signal, the oscillator 24 that generates a reference pulse to be supplied to the equiripple filter 13, and the current value set by the current setting unit 23 are notified to the operator. And an output terminal OUT3 that outputs a reference pulse from the oscillator 24.

  When configured in this manner, the equiripple filter 11 further includes a secondary filter composed of gm amplifiers 111 and 112, capacitors C1 and C2, an inversion amplifier 113 with a gain α, and a buffer 114, as shown in FIG. Filter 11a, a primary filter 11b composed of gm amplifier 115, capacitor C3 and buffer 116, and a secondary filter 11c composed of gm amplifiers 117 and 118, capacitors C4, C5 and buffer 119 are connected in series. A fifth-order equiripple filter is used. The gm amplifiers 111, 112, 115, 117, and 118 are connected to the variable current source 12 (see FIG. 1), and a current set by the variable current source 12 flows.

  At this time, in the filter 11a, the non-inverting input terminal of the gm amplifier 111 is connected to the input terminal IN1, the other end of the capacitor C1 whose one end is grounded to the output terminal of the gm amplifier 111, and the non-inverting input terminal of the gm amplifier 112. Connected. Further, the input side of the buffer 114 and one end of the capacitor C2 are connected to the output terminal of the gm amplifier 112, and the inverting input terminals of the gm amplifiers 111 and 112 are connected to the output side of the buffer 114. The inverting amplifier 113 has an input side connected to the non-inverting input terminal of the gm amplifier 111 and an output side connected to the other end of the capacitor C2.

  In the filter 11b, the non-inverting input terminal of the gm amplifier 115 is connected to the output side of the buffer 114 of the filter 11a, and the other end of the capacitor C3 whose one end is grounded to the output terminal of the gm amplifier 115 and the buffer 116. The input side is connected, and the inverting input terminal of the gm amplifier 115 is connected to the output side of the buffer 116. Further, in the filter 11c, the non-inverting input terminal of the gm amplifier 117 is connected to the output side of the buffer 116 of the filter 11b, and the other end of the capacitor C4 whose one end is grounded to the output terminal of the gm amplifier 117 and the gm amplifier 118. The non-inverting input terminal is connected. The input terminal of the buffer 119 and the other end of the capacitor C5 whose one end is grounded are connected to the output terminal of the gm amplifier 118, and the inverting input terminals of the gm amplifiers 117 and 118 are connected to the output side of the buffer 119.

  Further, as shown in FIG. 2B, the equiripple filter 13 has a switch SW whose one end is turned on and off by a reference pulse, and an output terminal connected to the other end of the switch SW and a non-switching end. A gm amplifier 131 to which a predetermined DC voltage is applied between the inverting input terminal and the inverting input terminal, and a capacitor C6 having one end connected to the output terminal of the gm amplifier 131 and the other end grounded. The output terminal OUT2 is connected to a connection node between the output terminal of the gm amplifier 131 and the capacitor C6. That is, the gm amplifier 131 and the capacitor C6 constitute a first-order gm filter. At this time, the switch SW is turned on when the reference pulse from the input terminal IN2 is low, and the switch SW is turned off when the reference pulse from the input terminal IN2 is high.

  The operation for adjusting the time constant of the high-frequency equalizer 1 configured as described above will be described below. First, as shown in FIG. 1, the output terminal OUT3 and the input terminal IN3 of the time constant adjusting device 2 are connected to the input terminal IN2 and the output terminal OUT2 of the high-frequency equalizer 1, respectively. After the current value setting unit 23 sets the voltage value generated by the variable voltage source 21 to a voltage value VTH higher than the voltage value of the signal input to the input terminal IN3 when the time constant of the target range is obtained. The oscillator 24 outputs a reference pulse that is high for a predetermined period t.

  When the high reference pulse from the oscillator 24 is input to IN2 of the high-frequency equalizer 1, the switch SW is turned off in the equiripple filter 13, so that the capacitor C6 is charged. Therefore, since the switch SW is ON until just before the high reference pulse is input, the voltage value of the output terminal OUT2 whose output is the ground voltage (0) becomes as shown in FIG. It rises according to a time constant gm / C determined by the conductance component gm by the gm amplifier 131 and the capacitance value C by the capacitor C6.

  When the reference pulse from the oscillator 24 becomes low, the switch SW is turned on and the output terminal OUT2 is grounded, and the voltage appearing at the output terminal OUT2 is reduced to the ground voltage (0) as shown in FIG. At this time, the voltage appearing at the output terminal OUT2 is input to the input terminal IN3 of the time constant adjusting device 2, and the voltage of the signal output from the equal ripple filter 13 is compared with the voltage value VTH by the comparator 22. When the voltage of the signal output from the equiripple filter 13 is higher than the voltage value VTH, the signal is higher than that of the comparator 22, and conversely, when the voltage of the signal output from the equiripple filter 13 is lower than the voltage value VTH, It becomes low from the comparator 22.

  The current value setting unit 23 determines that the time constant gm / C is larger than the target range and out of the target range when the signal supplied from the comparator 22 becomes high. When the given signal never goes high, it is determined that the time constant gm / C is below the target range. Thereafter, when the reference pulse goes low from the oscillator 24, when it is determined that the time constant gm / C is larger than the target range, the current value by the variable current source 12 is smaller than the preset current value I. A control signal that is set to be I-KI is output. Then, in the notification unit 25, an output such as a display indicating that the current value I-KI is set is output to the worker, and the time constant adjustment operation is terminated.

  On the other hand, when it is determined that the time constant gm / C is less than or equal to the target range, the voltage value generated by the variable voltage source 21 is the signal input to the input terminal IN3 when the time constant in the target range is obtained. After setting the voltage value VTL lower than the voltage value, the oscillator 24 is again made to output a reference pulse that is high for a predetermined period t. As in the case where the first reference pulse is given, in the high frequency equalizer 1, while the reference pulse is high, the voltage of the signal output from the equiripple filter 13 is changed to the ground voltage (0) as shown in FIG. ), The reference pulse goes low, and falls to the ground voltage (0).

  At this time, the voltage appearing at the output terminal OUT2 is input to the input terminal IN3 of the time constant adjusting device 2, and the voltage of the signal output from the equal ripple filter 13 is compared with the voltage value VTL by the comparator 22. When the voltage of the signal output from the equiripple filter 13 is higher than the voltage value VTL, it becomes higher than that of the comparator 22, and conversely, when the voltage of the signal output from the equiripple filter 13 is lower than the voltage value VTL, It becomes low from the comparator 22.

  Unlike the case where the first reference pulse is given, the current value setting unit 23 judges that the time constant gm / C is within the target range when the signal given from the comparator 22 becomes high. On the contrary, when the signal supplied from the comparator 22 does not become high, it is determined that the time constant gm / C is smaller than the target range and out of the target range. Thereafter, when the reference pulse becomes low from the oscillator 24, if it is determined that the time constant gm / C is smaller than the target range, the current value by the variable current source 12 is larger than the preset current value I. A control signal that is set to be I + KI is output. Then, in the notification unit 25, an output such as a display indicating that the current value is set to I + KI is made to notify the operator, and the time constant adjustment operation is ended. On the other hand, when it is determined that the time constant gm / C is within the target range, a control signal that keeps the current value I set in advance is output, and then the current value I is set in the notification unit 25. When an output such as a display indicating the above is made, the operator is notified and the time constant adjustment operation is terminated.

  In such an operation, when the voltage of the signal output from the equiripple filter 13 is increased by the reference pulse, as shown in FIG. 4A, until the reference pulse becomes high and time t elapses. When the voltage value becomes higher than VTH, when the first reference pulse is output from the oscillator 24, a signal that becomes high from the comparator 22 is output to the current value setting unit 23. Then, after the first reference pulse becomes low, a control signal is given from the current value setting unit 23 to the variable current source 12, and the current value flowing through the equal ripple cover 11 is set to the current value I-KI.

  When the voltage of the signal output from the equiripple filter 13 is increased by each reference pulse, as shown in FIG. 4C, the voltage value is increased until the time t elapses when the reference pulse becomes high. If it is not higher than VTL, a signal that goes low from the comparator 22 remains output to the current value setting unit 23 when the first and second reference pulses are output from the oscillator 24. After the second reference pulse becomes low, a control signal is supplied from the current value setting unit 23 to the variable current source 12, and the current value flowing through the equal ripple filter 11 is set to the current value I + KI.

  Further, when the voltage of the signal output from the equal ripple filter 13 is increased by each reference pulse, as shown in FIG. 4B, the voltage value is changed until the time t elapses when the reference pulse becomes high. In the case of VTL or more and VTH or less, when the first reference pulse is output from the oscillator, the low signal remains output to the current value setting unit 23, and the second reference pulse is output from the oscillator 24. Is output from the comparator 22 to the current value setting unit 23. Then, after the second reference pulse becomes low, a control signal is given to the variable current source 12 from the current value setting unit 23, and the current value flowing through the equal ripple filter 11 is set to the current value I.

  By operating in this manner, the variable current is set such that a current value corresponding to the time constant of each gmC filter constituting the slave equiripple filter 11 flows based on the output signal of the master equiripple filter 13. A current value by the source 12 is set. That is, when the time constant gm / C becomes larger than the target range, the current value I-KI is set. When the time constant gm / C becomes smaller than the target range, the current value I + KI is set, and the time constant gm / C falls within the target range. When C is present, the current value by the variable current source 12 is selected and set from three values so that the current value I is set.

  When the current value set by the variable current source 12 is set in the current value setting unit 23 in this way, the current value set by the notification unit 25 is notified to the operator. The current value to be set is confirmed, and the variable current source 12 is set. As shown in FIG. 5, the variable current source 12 is connected to a constant current source 121 having one end connected to the equiripple filter 11 and the other end grounded, and a connection node between the constant current source 121 and the equiripple filter 11. One end is connected to the other end of the switch SW1, SW2, one end is connected to the other end of the switch SW1, and the other end of the switch SW2 is connected to the other end of the switch SW2. And a constant current source 123 whose other end is grounded. Then, the current value I flows through the constant current source 121, and the current value KI flows through the constant current sources 122 and 123.

  Therefore, when the notification unit 122 notifies that the current value I−KI is set, the operator sets the switch SW1 to be ON and the switch SW2 to be OFF, and the notification unit 122 sets the current value to I + KI. When it is notified that the switch SW1 is turned OFF and the switch SW2 is turned ON by the operator, and the notification unit 122 notifies that the current value I is set, the operator switches the switch SW1 to OFF. Both SW1 and SW2 are set to be OFF.

  At this time, when fuses are used as the switches SW1 and SW2, electrical disconnection is performed by physically cutting the fuses corresponding to the switches to be turned off. In addition, when the switches SW1 and SW2 are electrically connected and turned on by pattern wiring, electrical connection is performed by physically connecting the portions corresponding to the switches to be turned on by pattern wiring. . Further, jumper switches may be used as the switches SW1 and SW2.

  In the present embodiment, as described above, when the first reference pulse is generated, it is compared with the voltage value VTH, and when the second reference pulse is generated, it is compared with the voltage value VTL. However, it may be compared with the voltage value VTL when the first reference pulse is generated and compared with the voltage value VTH when the second reference pulse is generated. At this time, when the first reference pulse is generated and the signal from the comparator 22 remains low until the time t elapses when the reference pulse becomes high, the current of the variable constant current source 12 When the value is set to the current value I-KI and the operation ends, and when it is confirmed that the signal from the comparator 22 is switched to high, a second reference pulse is generated.

  In the present embodiment, the comparator 22 in the time constant adjusting device 2 is one, and the voltage values VTH and VTL are switched by the variable voltage source 21, but as shown in FIG. Comparators 22a and 22b to which voltage values VTH and VTL from 21b are respectively provided are provided, and the current value of the variable current source 12 may be set by one reference pulse. At this time, the comparators 22a and 22b are connected to the input terminal IN3, respectively, and the output from the equal ripple filter 13 is input, and the comparison results of the comparators 22a and 22b are given to the current setting unit 23. Then, the current setting unit 23 makes a determination similar to that when the first reference pulse in the above operation is given from the output from the comparator 22a, and also in the above operation from the output from the comparator 22b. The current value of the variable current source 12 is set by performing the same determination as when the second reference pulse is given.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a block diagram showing an internal configuration of the high-frequency equalizer and the time constant adjusting device for adjusting the time constant of the high-frequency equalizer according to the present embodiment. In the configuration of FIG. 7, portions used for the same purpose as the configuration of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 7, the high-frequency equalizer 1a of the present embodiment has an input terminal IN4 to which a control signal for setting the current value of the variable current source 12 is input, and an input terminal IN4 in the configuration of the high-frequency equalizer 1 in FIG. A D / A converter 14 for converting a control signal input from the input signal into an analog signal is added. Further, the time constant adjusting device 2a of the present embodiment is different from the configuration of the time constant adjusting device 2 of FIG. 1 in that the signal input to the input terminal IN3 is a digital signal instead of the variable voltage source 21 and the comparator 22. An A / D converter 26 for converting to a current value is provided, and an output terminal OUT4 for outputting a signal indicating the current value set by the current setting unit 23 is added.

  Furthermore, in the present embodiment, a signal from the output terminal OUT4 of the time constant adjusting device 2a is input to the control device 3 provided in an electronic device such as a disk device in which the high frequency equalizer 1a is installed, and the memory ( The current value set by the current setting unit 23 is stored in (not shown). The control device 3 designates the current value of the variable current source 12 in the high-frequency equalizer 1a by giving a control signal, which is a digital signal representing the current value stored in the memory, to the input terminal IN4 of the high-frequency equalizer 1a. Similarly to the first embodiment, the equiripple filters 11 and 13 of the high-frequency equalizer 1a are configured as shown in FIGS. 2A and 2B, respectively, and the oscillator 24 of the time constant adjusting device 2a has a time t. Generate a reference pulse that goes high for a while.

  When configured in this manner, in the present embodiment, the current setting unit 23 sets the current value by outputting the reference pulse from the oscillator 24 only once in the time constant adjusting device 2a. At this time, the high frequency equalizer 1a to which the reference pulse from the oscillator 24 is input to the input terminal IN2 turns off the switch SW of the equiripple filter 13 when the reference pulse becomes high, as in the first embodiment. Thus, the capacitor C6 is charged, and the voltage of the signal output from the equal ripple filter 13 via the output terminal OUT2 rises. When the reference pulse becomes low after the time t has elapsed, the voltage of the signal output from the equiripple filter 13 via the output terminal OUT2 falls to the ground voltage (0).

  The signal from the equiripple filter 13 changing in this way is input to the A / D converter 26 via the input terminal IN3 of the time constant adjusting device 2a. This A / D converter 26 converts the signal input from the input terminal IN 3 into a digital signal in synchronization with the falling from the high pulse to the low pulse in the reference pulse of the oscillator 24 and inputs it to the current value setting unit 23. To do. In the current value setting unit 23, the output value of the equiripple filter 13 when the time t has elapsed since the reference pulse became high is confirmed by the digital signal supplied from the A / D converter 26.

  Then, according to the output value of the equiripple filter 13, the current value of the variable current value 12 is set in the range of I-KI or more and I + KI or less, and a signal indicating the set current value is output from the output terminal OUT4 to the control device 3. Then, the operation in the time constant adjusting device 2a is finished. Further, in the control device 3, when a signal indicating the current value of the variable current value 12 is given from the current value setting unit 23 of the time constant adjusting device 2 a, it is stored in a memory (not shown) in the control device 3.

  At this time, when the output voltage value from the equal ripple filter 13 becomes Vo, a time constant that becomes the center of the target range is obtained, and this output voltage value Vo is set as a reference value. When the output voltage value from the equal ripple filter 13 is confirmed to be V from the digital signal given to the current value setting unit 23 from the A / D converter 26, the current value setting unit 23 A difference V−Vo between the output voltage V from the ripple filter 13 and the reference value Vo is obtained. When the difference V-Vo is equal to or greater than KV, the current value of the variable current value 12 is set to I-KI. When the difference V-Vo is equal to or less than -KV, the current value of the variable current value 12 is set to I + KI. Set to. Further, when the difference V-Vo becomes a value between -KV and KV, the current value of the variable current value 12 is set to I-KI * (V-Vo) / KV.

  In this manner, the electronic device operates in a state where the signal representing the current value set by the current value setting unit 23 is stored in the memory of the control device 3. At this time, a signal indicating the current value stored in the memory is read from the control device 3 and is supplied to the high frequency equalizer 1a as a control signal. Then, in the high frequency equalizer 1a, a control signal which is a digital signal from the control device 3 is supplied to the D / A converter 14 via the input terminal IN4 and converted into an analog signal. When the analog signal converted by the D / A converter 14 is supplied to the variable current source 12, the voltage control of the variable current source 12 is performed based on the voltage value of the analog signal, and the current value from the variable current source 12 is changed. It is determined.

  That is, the signal indicating the current value initially set by the time constant adjusting device 2a is always stored in the memory of the control device 3, and the control signal based on the stored signal is sent from the control device 3 to the high frequency equalizer 1a. As a result, the time constant of the equiripple filter 11 is set. Therefore, the high-frequency equalizer 1a always obtains a target time constant by causing the variable current source 12 to flow a current having a current value set by receiving a control signal from the control device 3.

  In the present embodiment, the D / A converter 14 is provided in the high-frequency equalizer 1 a and the voltage of the variable current source 12 is controlled by the output from the D / A converter 14. May be composed of a plurality of constant current sources and switches as shown in FIG. 8, and the D / A converter 14 may be omitted. The variable current source 12 shown in FIG. 8 includes a constant current source 121 through which a constant current value I flows, similarly to the variable current source 12 shown in FIG. 6, and one end at a connection node between the constant current source 121 and the equal ripple filter 11. Are connected to the other ends of the switches SW1-1 to SW1-n, SW2-1 to SW2-n, and the switches SW1-1 to SW1-n and SW2-1 to SW2-n. Current sources 122-1 to 122-n, 123-1 to 123-n.

At this time, the power supply voltage is applied to the other ends of the constant current sources 122-1 to 122-n, and the other ends of the constant current sources 123-1 to 123-n are grounded. A constant current having a current value KI / 2 ^k flows through each of the constant current sources 122-k and 123-k (k is a natural number of 1 ≦ k ≦ n). With this configuration, when each of the switches SW1-1 to SW1-n is ON / OFF controlled, each of the constant current sources 121-1 to 121-n flows into the constant current source 120. Therefore, the variable current source 12 A current value I−C × KI (C is 0 ≦ C ≦ 1) to be given to the equal ripple filter 11 is set. Further, when each of the switches SW2-1 to SW2-n is ON / OFF controlled, the constant current sources 122-1 to 122-n flow from the equiripple filter 11 to the equiripple filter 11 by the variable current source 12. The current value I + C × KI (C is 0 ≦ C ≦ 1) is set.

  Therefore, when an n + 1 bit control signal to which a digit indicating ± is added from the control device 3 is given to the high frequency equalizer 1a, when the digit indicating 1 bit indicates “−”, the remaining n bit digits are used. When the digit indicating 1 ± of “+” indicates “+”, the remaining n bits are applied to the switches SW2-1 to SW2-n. In this way, the switches SW1-1 to SW1-n and SW2-1 to SW2-n are ON / OFF controlled by the control signal that is a digital signal, and the current value is set.

  In the first embodiment, the variable current source 12 may be configured as shown in FIG. At this time, it is assumed that the switches SW1-1 to SW1-n and SW2-1 to SWn-n are configured by fuses, and the reference pulse is generated and is electrically changed according to the current value confirmed by the time constant adjusting device. The switch to be cut may be confirmed, and the fuse corresponding to the confirmed switch may be physically cut. Conversely, a portion corresponding to the electrically connected switch may be pattern-wired.

These are block diagrams which show the internal structure of the high frequency equalizer and time constant adjustment apparatus of 1st Embodiment. These are circuit diagrams which show the structure of ripple filters, such as a master and a slave. These are the figures which show the output of the equiripple filter used as the master to which the reference pulse was input. These are the figures which show the output of the equiripple filter used as the master to which the reference pulse was input. These are figures which show one structural example of a variable current source. These are figures which show another example of a connection of the time constant adjustment apparatus with respect to the high frequency equalizer of 1st Embodiment. These are block diagrams which show the internal structure of the high frequency equalizer and time constant adjustment apparatus of 2nd Embodiment. These are figures which show another structural example of a variable current source.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1a High frequency equalizer 2,2a Time constant adjustment apparatus 3 Control apparatus

Claims (6)

In a high frequency equalizer comprising: a gmC filter based on a conductance component and a capacitor capacity; and a current source that supplies a current to the gmC filter.
A measurement gmC filter for measuring a time constant having a conductance component and a capacitor capacity constituting the gmC filter;
A variable voltage source;
A comparator to which the output voltage of the measurement gmC filter and the output voltage of the variable voltage source are input;
A current value setting unit to which the output voltage of the comparator is input;
With
The current value setting unit includes:
The output voltage of the variable voltage source is set to a first voltage value higher than the voltage value when the time constant of the target range of the gmC filter is obtained, and the output voltage of the measurement gmC filter is set to the first voltage value. Determining whether or not
The output voltage of the variable voltage source is set to a second voltage value lower than the voltage value when the time constant of the target range of the gmC filter is obtained, and the output voltage of the measurement gmC filter is set to the second voltage value. Determining whether or not
To determine whether or not the time constant of the gmC filter is within a target range, and set a current value from the current source according to the determination result. The current source is
A first constant current source connected to the gmC filter and for supplying a current having a reference current value;
A second constant current source connected to the first constant current source to reduce a current value flowing through the gmC filter by the first constant current source;
A third constant current source connected to the first constant current source to increase a current value flowing through the gmC filter by the first constant current source;
A first switch connected between the first constant current source and the second constant current source;
A second switch connected between the first constant current source and the third constant current source;
With
When the time constant of the measurement gmC filter is measured to be larger than the target range, the first switch is turned on and the second switch is turned off.
When it is measured that the time constant of the measurement gmC filter is smaller than the target range, the second switch is turned on and the first switch is turned off,
2. The high-frequency equalizer according to claim 1, wherein when the time constant of the measurement gmC filter is measured to be within a target range, both the first switch and the second switch are turned off. A plurality of the second constant current sources are provided and each of the second constant current sources is connected in parallel.
A plurality of the third constant current sources are provided and each of the third constant current sources is connected in parallel.
The high-frequency equalizer according to claim 2, wherein a plurality of the first and second switches are connected to the plurality of second and third constant current sources, respectively.   4. The high frequency equalizer according to claim 2, wherein the switch is a fuse.   The high frequency according to any one of claims 1 to 3, wherein a current value from the current source is set by inputting a control signal indicating a current value flowing from the current source from the outside. equalizer.   The measurement gmC filter is
  A traversal conductance amplifier to which a predetermined voltage is input;
  A capacitor having one end connected to the output terminal of the traversal conductance amplifier and a DC voltage applied to the other end;
  One end is connected to a connection node between the traversal conductance amplifier and the capacitor, the DC voltage is applied to the other end, and a switch that is turned off when a reference pulse is applied;
  With
  6. The current value from the current source is set by a voltage appearing at a connection node between the traversal conductance amplifier and the capacitor when the reference pulse is given. The high frequency equalizer according to crab.

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