JP2000068769A - Signal processing device - Google Patents

Abstract

(57) [Problem] To provide a signal processing device capable of obtaining a large dynamic range of the entire device despite using a signal processing block having a small dynamic range. The signal processing device detects a first gain control block for controlling a gain of an input signal, a signal processing block provided at a stage subsequent to the gain control block, and an energy of an output signal of the signal processing block. An energy detection block for controlling a gain change amount of the gain control block depending on the detection amount, wherein the first gain control block compresses the amplitude of the input signal so as to correspond to the dynamic range of the signal processing block. Then, this is input to the signal processing block.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal processing device for processing a received signal, and more particularly to a signal processing device integrally formed by an LSI and including an automatic gain control circuit (hereinafter abbreviated as an AGC circuit).

[0002]

2. Description of the Related Art An AGC circuit is a circuit for detecting the intensity of a received signal (input signal) and compressing the amplitude to a fixed or narrower range to form an output signal. The form is well known. FIG. 1 shows such an A
As an example of a signal processing device including a GC circuit, a receiving device used for a mobile phone will be described. In FIG. 1, 1 is a bandpass filter, 2 is a gain control block, and 3 is an energy detection block.

In this device, a signal input from an input terminal 5 is filtered by an AGC circuit 4 comprising a gain control block 2 and an energy detection block 3 after an out-of-band noise is removed by a band-pass filter 1. The gain is controlled so that the signal has The signal thus gain-controlled is input to, for example, a demodulation circuit (not shown) via the output terminal 6, and necessary information is extracted.

In the apparatus shown in FIG. 1, since the band-pass filter 1 is located before the gain control block 2, it is assumed that a band-pass filter having a large dynamic range is used.

[0005]

Conventionally, bandpass filters have been used as external components of LSIs. However, in recent years, in order to reduce the cost and volume of various electronic devices, there has been a tendency to incorporate various external components into the LSI and integrate them. In particular, in mobile phones, there is a great demand for reduction in volume, and for that purpose, it is absolutely necessary to integrate a bandpass filter inside the LSI.

However, the bandpass filter is
If you try to build it in, it has to be an active circuit using an amplifier etc., whereas it was a passive circuit in the past,
Its dynamic range is smaller than that of a band-pass filter of an external component. Therefore, there is a need for a signal processing device capable of obtaining a large dynamic range of the entire device despite the use of a bandpass filter having a small dynamic range. The configuration shown in FIG. 2 is conceivable as such a signal processing device.

That is, the apparatus shown in FIG. 2 is characterized in that a band-pass filter 1 is arranged at a stage subsequent to an AGC circuit 4 comprising a gain control block 2 and an energy detection block 3. In this device, by providing the AGC circuit 4 in the preceding stage of the band-pass filter 1, the dynamic range of the input signal is compressed to an extent that matches the dynamic range of the band-pass filter 1, and this is input to the band-pass filter 1. Can be. Therefore, even if the dynamic range of the bandpass filter 1 itself is small, the dynamic range of the entire device can be widened.

However, in the signal processing device having the arrangement shown in FIG. 2, when an input signal contains an interfering wave, the AGC circuit 4 performs gain control including the interfering wave. 1 causes a serious problem that interference between a desired wave to be extracted and an interfering wave occurs, and the waveform of the desired wave is distorted. For example, PDC (Pers
onal Digital Cellular)
Although the frequency is used at intervals of 25 kHz, the receiver receives only one of the waves and converts it into an audio signal.
All other signals at 25 kHz intervals are treated as interfering waves.
Therefore, the interference wave may be larger than the desired reception wave.

The band-pass filter is provided to attenuate such an interference wave of the input signal and extract only a desired wave. However, in the receiver having the configuration shown in FIG. 2, since the AGC circuit 4 including the gain control block 2 and the energy detection block 3 is disposed in front of the band-pass filter 1, an input wave including an interference wave is generated. The gain is controlled by the AGC circuit 4.

[0010] Therefore, depending on the frequency of the interfering waves, the interfering waves may interfere with each other and cause intermodulation distortion in the frequency band of the desired wave. For example, 550kHz, 650kHz
May interfere with each other to produce an interference wave of 450 kHz. The interference wave and the desired wave of 450 kHz are combined to generate signal distortion, but this distortion cannot be removed by the bandpass filter 1 because it exists in the passband.

As described above, if the AGC circuit is arranged before the signal processing block such as the band-pass filter, signal distortion that cannot be removed by the subsequent signal processing block occurs, and the signal processing capability of this device is increased. A situation occurs that significantly lowers SUMMARY OF THE INVENTION The present invention has been made to solve the above-described drawbacks of the conventional device, and can incorporate a signal processing block and a gain control block into one LSI without causing significant signal distortion to an input signal. A possible signal processing device and an LSI incorporating the device are provided.

[0012]

An object of the present invention is to provide a first gain control block for controlling the gain of an input signal, a signal processing block provided after the gain control block, and an energy of an output signal of the signal processing block. And an energy detection block for automatically controlling the gain change amount of the gain control block depending on the detection amount.

In this signal processing device, the dynamic range of the input signal is compressed by the gain control block so as to be adapted to the dynamic range of the signal processing block, and is then input to the signal processing block. Therefore, even if the dynamic range of the signal processing block itself is small, the dynamic range of the entire device can be widened. Further, since the automatic gain control is performed by detecting the energy of the output signal of the signal processing block, the signal to be gain controlled does not include an interference wave, and as a result, the gain control of only the signal wave to be processed is performed. Can be performed accurately.

[0014]

FIG. 3 is a block diagram showing the principle of the present invention. As shown in the figure, the apparatus of the present invention is characterized in that a signal processing block 10 which is, for example, an active band-pass filter is disposed between a gain control block 20 such as an electronic volume and an energy detection block 30. . Reference numeral 50 denotes an input terminal of a received signal, and reference numeral 60 denotes an output terminal. These circuits are built in one LSI 100.

The signal processing block 10 includes LS
The above-mentioned active band-pass filter or low-pass filter whose dynamic range is necessarily smaller than that of externally mounted components in order to be built in I is applied, and a high-pass filter or the like is also applicable. As described above, the apparatus of the present invention is characterized in that the signal processing block 10 is disposed between the gain control block 20 and the energy detection block 30.

As a result, the energy detection block 30 detects the amplitude of the signal after the signal processing by the signal processing block 10 and controls the gain control block 20 disposed in the preceding stage of the signal processing block 10 to perform the detection. Since the gain control of the signal wave thus performed is performed, the signal subjected to the automatic gain control is not affected by the interference wave, and the above-described intermodulation distortion or the like does not occur.

Therefore, even if a built-in band-pass filter having a smaller dynamic range than an external band-pass filter is used as a signal processing block, only a desired wave can be obtained while maintaining a large dynamic range of the entire apparatus. Automatic gain control can be performed to a constant amplitude without signal distortion. FIG. 4 shows the first embodiment of the present invention.
1 is a block diagram showing a configuration of a signal processing device suitable as, for example, a receiver of a mobile phone. In the figure, reference numerals 21 and 22 denote first and second controlled by digital codes.
, 11 denotes a built-in band-pass filter, 31 denotes an energy detection circuit, and 70 denotes a demodulation circuit. Reference numerals 50 and 60 'denote input / output terminals, and these constituent elements 21, 11, 22, 31 and 70
Are incorporated in one LSI 101.

The energy detection circuit 31 is composed of two comparators 32 and 33 having different reference values VRH and VRL, and a logic circuit 34. The energy detection circuit 31 may be, for example, a type of circuit that detects a peak value of a detection signal. FIG. 5 shows how each of the reference values VRH and VRL is selected according to the amplitude of the input signal. As shown in the figure, the reference value VRH is a reference value set so as to perform control for lowering the gain by the automatic gain control circuit when the amplitude of the input signal exceeds this value, and the reference value VRL is the amplitude of the input signal. Is less than or equal to this value, it is a value set to perform control to increase the gain by the automatic gain circuit.

When the amplitude of the input signal is between the reference value VRH and the reference value VRL, it is considered that the amplitude is within an appropriate range, and the gain is not changed. Logic circuit 34
Determines from the outputs of the comparators 32 and 33 where the amplitude level of the signal is with respect to each of the reference values VRH and VRL, and outputs the determination signal to the electronic volumes 21 and 22. The electronic volumes 21 and 22 execute gain control based on the output of the logic circuit 34 as shown in FIG.

In this embodiment, first and second electronic volumes 21 and 22 are provided before and after the band-pass filter 11. Generally, the band-pass filter 11 has a large delay. Therefore, the electronic volume 21 provided in front of the band-pass filter 11 needs to be controlled late so as not to oscillate. On the other hand, since the second electronic volume 22 is located after the band-pass filter 11, it is not necessary to delay the control.

Therefore, the gain control is repeated between the energy detection circuit 31 and the second electronic volume 22 at a high speed, an integrated value of the control amount is calculated and fed back to the first electronic volume 21, and the gain is obtained. Control processing can be performed. This allows high-speed gain control while keeping the effect of the delay of the bandpass filter 11 to a minimum.

In the apparatus shown in FIG. 4, a circuit for calculating the integrated value of the timer and the control amount of the second electronic volume 22, and the gain of the electronic volume 22 in which the calculated value is set in advance are provided in the electronic circuit 34. And outputs a signal for controlling the gain of the first electronic volume 21 based on the comparison value. Note that such a circuit can be actually configured by appropriately programming an electronic circuit.

FIG. 6 is a simplified flowchart showing the operation of the electronic circuit. As shown in the figure, in the first control step S1, the gain of the electronic volume 22 is automatically adjusted between the energy detection circuit 31 and the second electronic volume 22 so that the amplitude of the output of the electronic volume 22 becomes constant. Control. At this time, the convergence value of the gain of the second electronic volume 22 is set to _GE in advance. Further, the gain of the first electronic volume 21 is also set appropriately in advance.

Next, in the second control step S2, the energy is
Between the power detection circuit 31 and the second electronic volume 22.
The dynamic gain control is repeated N times, and the average value G of the gain at that time is obtained._av
Ask for. That is, G_av= (G₁+ G_Two... + G_N) /
Calculate N. G₁, G _Two... G_NIs an electronic volume
3 shows the gain value of each time of the automatic gain control in the room 22.

Next, in the control step S3, the obtained G
_av is compared with the convergence value G _E of the gain of the second electronic volume 22. 1) When G _av <G _E , control is performed to lower the gain of the first electronic volume 21. G _av <G _E means that G _av = G
Considering that the input amplitude of the band-pass filter 11 is appropriate at the time of _E , the control for lowering the gain between the second electronic volume 22 and the energy detection circuit 31 is performed. This means that the amplitude of the applied signal is too large. Therefore, the gain of the first electronic volume 21 is reduced and the band-pass filter 11
Is converged more quickly to a constant value.

[0026] 2) When G _av = G _E does not change the gain of the first electronic volume 21. In this state, it is considered that the amplitude of the input signal is within an appropriate range. 3) when G _av> G _E performs processing to increase the gain of the first electronic volume 21. This is because the configuration between the second electronic volume 22 and the energy detection circuit 31 in the state of G _av > G _E is considered considering that the input amplitude of the band-pass filter 11 is appropriate when G _av = G _E. Since the automatic gain control circuit performs the control to increase the gain, that is, the amplitude of the input signal is too small, the gain of the first electronic volume 21 is increased, and the gain of the band-pass filter 11 is increased. The output reaches a certain amplitude value more quickly.

FIG. 7 is a timing chart of the first, second, and third controls S1, S2S3 when N is 5. As described above, the gain is controlled by the second electronic volume 22 at a high speed, and the average value of the control amount is fed back to the first electronic volume 21 to control the gain amount. It is possible to execute the gain control of the input signal more effectively and quickly by avoiding the problem caused by the delay of the pass filter.

FIG. 8 shows the energy detector 30 shown in FIG.
FIG. 9 is a circuit diagram of another embodiment, and FIG. 9 is a state transition diagram for explaining the operation of the circuit of FIG. In this embodiment, the gain change amount in the energy detection block 300 is binary (G
a, Gb, | Ga |> | Gb |), and the gain change amount for the gain control block 20 is made variable depending on the detection amount of the energy detection block 300.

The configuration of the circuit shown in FIG.
The operation will be described with reference to FIGS. First of all
In the circuit of the embodiment, as shown in FIG.
And V ₁, V_Two, V_ThreeAnd V_Four(V₁> V_Two> V_Three>
V_Four) Are set. Each of these
The threshold is appropriately selected by the selector 35, and the first,
Introduced to the reference input terminals (-) of the second comparators 36 and 37.
Have been. To the comparison input terminals (+) of the comparators 36 and 37
Is a signal input through the band-pass filter 10
You. 38 and 39 are hold circuits, which are comparators for a certain period.
Monitor the outputs of 36 and 37 and when the output changes to 1
Only the circuit that holds that value. In addition, hold
The outputs D1 and D0 of the circuits 38 and 39 are input to the logic circuit 340.
Is forced.

Each of the states A, B,
C, and the threshold voltages V ₁ , V ₂ ,
FIG. 10A shows the relationship between V ₃ and V _{4 and} the selected state. FIG. 10B shows a combination of 1 and 0 in the outputs D1 and D0 of the hold circuits 38 and 39, a state of the amplitude of the input signal determined by the combination, and a gain change amount in the state. .

In the circuit shown in FIG.
7 is connected to the threshold V ₃ via the selector 35.
And V ₄ and are connected, that is, if the state A is selected, the amplitude of the signal input to the energy detection block 30 is less than the threshold V _4, D1, D0
Are both 0. Therefore, based on the determination information of FIG. 10B, the logic circuit 340 determines that the amplitude of the input signal is in the state A.
Is determined to be “below”, the gain is increased by the gain change amount Ga, and the signal amplitude is expanded.

On the other hand if the amplitude of the signal input to the energy detection block 30 is less than the threshold value V ₄ higher V ₃ D
1 is 0 and D0 is 1. Based on the determination information in FIG. 10B, the logic circuit 340 determines that the amplitude of the input signal is “middle” between the state A and the state B, and determines the amount of change in the gain. + Gb
By changing the threshold value to one corresponding to the state B while changing the gain as (<Ga), the state is changed from A to B
Change to

Furthermore, if the amplitude of the signal input to the energy detection block 30 is the threshold value V ₃ or more, without changing the gain (amount of change = 0), a state change only the threshold Change from A to B. Hereinafter, also in the state B and the state C, the state and the gain are changed according to the state transition diagram of FIG. 9 and the determination information of FIG. 10B. When the state and the gain are changed, the circuit 340 becomes the hold circuits 38 and 39.
Is reset to “0”.

As described above, efficient gain control can be achieved by appropriately selecting two types of gain change amounts, large and small, depending on the detection amount in the energy detection block 30. As shown in FIG. 11, the signal processing apparatus 100a of the present invention having the basic configuration shown in FIG.
It is also possible to incorporate them into the 100. Further, as shown in FIG. 12, the signal processing device 100 of the present invention is
By incorporating the SI into the mobile phone receiver 110, a mobile phone with a small volume can be realized.

[0035]

As described above with reference to the embodiments, according to the present invention, in a signal processing device provided with an automatic gain control circuit, a gain control block is arranged before a signal processing block, and the signal processing Since the gain control is performed on the signal detected from the output terminal of the block, the interference wave included in the input wave is sufficiently attenuated in the signal subjected to the automatic gain control. Therefore, unlike a conventional signal processing device in which a signal processing block is arranged at a subsequent stage of an automatic gain control circuit, a signal to be processed does not include signal distortion due to an interference wave. Further, since the signal processing block is arranged between the gain control block and the energy detection block, the dynamic range of the entire apparatus can be increased even if the dynamic range of the signal processing block is small. Therefore, the effect of the device of the present invention is great when incorporated in an LSI.

[Brief description of the drawings]

FIG. 1 is a block diagram of a conventional signal processing device including an AGC circuit.

FIG. 2 is a block diagram of a signal processing device having an improved configuration for incorporating the device of FIG. 1 into an LSI.

FIG. 3 is a block diagram showing a basic configuration of a signal processing device according to the present invention.

FIG. 4 is a block diagram showing a first embodiment of the signal processing circuit of the present invention.

FIG. 5 is a diagram for explaining the operation of the device shown in FIG. 4;

FIG. 6 is a flowchart for explaining the operation of the apparatus shown in FIG. 4;

FIG. 7 is a timing chart for explaining the operation of the device shown in FIG. 4;

FIG. 8 is a diagram showing a circuit configuration of an energy detection block according to a second embodiment of the present invention.

FIG. 9 is a state transition diagram for explaining the operation of the circuit shown in FIG. 8;

FIG. 10 is a diagram provided for describing the operation of the circuit illustrated in FIG. 8;

11 is a diagram showing a device in which the signal processing devices shown in FIG. 3 are cascaded and incorporated in an LSI.

FIG. 12 is a diagram showing a state where the signal processing device of the present invention is incorporated in a receiver of a mobile phone.

[Explanation of symbols]

 1, 10, 11 band-pass filter 2, 20 gain control block 3, 30, 300 energy detection block 4, AGC circuit 5, 50 input terminal 6, 60, 60 'output terminal 21, first electron Volume 22 Second electronic volume 31 Energy detection circuit 32, 33, 36, 37 Comparator 34, 340 Logic circuit 35 Selector 100, 101 LSI

 ────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kazuaki Oishi 4-1-1, Kamidadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term in Fujitsu Limited (reference) 5J029 AA01 BA05 CA01 CA03 CA07 CA09 CA13 EA02 FA02 5J030 BA03 BB04 BC02 BC03 BC07 BC08 BC10

Claims (11)

[Claims] 1. A first gain control block for controlling a gain of an input signal, a signal processing block provided at a stage subsequent to the gain control block, and an energy of an output signal of the signal processing block is detected, and the detected amount is determined. An energy detection block for automatically controlling a gain change amount of the gain control block. 2. The signal processing device according to claim 1, wherein the signal processing block is one of a band-pass filter, a low-pass filter, and a high-pass filter. 3. The signal processing device according to claim 1, wherein a second gain control block is provided between the signal processing block and the energy detection block. 4. The energy detection block controls a gain change amount of the first gain control block according to a value obtained by calculating an integral value of a control amount in the second gain control block. The signal processing device according to claim 3. 5. The calculation of the integral value of the controlled variable is performed by the second
The gain control is performed by taking an average value of control amounts in a plurality of gain controls in the gain control block.
The signal processing device according to claim 1. 6. The apparatus according to claim 1, wherein at least one of said first and second gain control blocks is an electronic volume controlled by a digital code.
The signal processing device according to claim 1. 7. The first or first and second gain control blocks, wherein the energy detection block selects one of at least two types of gain change amounts depending on an amplitude level of an output of the signal processing block. The signal processing device according to claim 1, wherein a gain of the signal processing device is controlled. 8. The energy detection block according to claim 1, wherein a peak value of an output of the signal processing block is detected to control a gain of the first or first and second gain control blocks. The signal processing device according to any one of claims 1 to 7. 9. The signal processing apparatus according to claim 1, wherein the first gain control block, the signal processing block, and the energy detection block are cascade-connected in a plurality of stages. 10. The first gain control block, signal processing block, and energy detection block are one LSI
The signal processing device according to claim 1, wherein the signal processing device is incorporated therein. 11. A receiving device for a mobile phone, comprising the signal processing device according to claim 1.