KR100259915B1 - Dual agc amp control apparatus with analog and digital agc loop - Google Patents

Abstract

PURPOSE: A double automatic gain controller through an analog and a digital loops is provided to doubly implement an analog automatic gain control amplifier and a digital automatic gain control amplifier. CONSTITUTION: An RF(Radio Frequency) signal received from an antenna(211) is transceived through a duplexer(213). The RF signal is amplified by a low noise amplifier(213). A band filtering is performed to the amplified signal through an RF image filter(214). The signal is downed as an intermediate frequency through a down converter(215). The band filtering is performed to the signal through an intermediate frequency filter(217). An input signal is inputted to the first automatic gain control amplifier(218a) via the intermediate frequency filter(217). A dynamic range of the inputted signal is reduced as much as a determined level. The second automatic gain control amplifier(218b) has a new input dynamic range. An initial input signal is inputted to a demodulator(219) through the second automatic gain control amplifier(218b). The input signal is inputted to a receiving signal level indicating circuit. The receiving signal level indicating circuit generates a voltage capable of controlling the second automatic gain control amplifier as digital numerical data. The digital numerical data is converted into a corresponding analog signal, and inputted to a control terminal, The second automatic gain control amplifier(218b) uses the control voltage as a bias voltage, and controls a level of the current input signal to output the controlled level to the demodulator(219).

Description

Dual automatic gain control device through analog and digital loop

The present invention relates to an automatic gain control apparatus, and more particularly, to a dual automatic gain control apparatus through analog and digital loops of a mobile communication receiver.

The general automatic gain control amplifier is described as follows.

Automatic gain control refers to controlling gain so that the output magnitude is always kept constant regardless of the amplitude of the input signal. In addition, the magnitude required for the output is a value required for a demodulator of the receiver. Also, receiver design typically requires a lot of input dynamic range.

The receiver according to the prior art will now be described in detail.

1 is a block diagram of a receiver according to the prior art.

Referring to FIG. 1, a radio frequency (RF) signal transmitted to the air through a radio from an antenna of a transmitter is first received through an antenna ANT 111. The RF signal is variable in size depending on the distance and the position of the antenna. In theory, the RF POWER is typically squared over a distance when the positions of the transmitting antenna and the receiving antenna are located in a line of light. It becomes to be. Thus, in the case of the CDMA terminal currently in use, there is a difference in size from -106Bm to -20dBm at minimum. In such a case, the input dynamic range is almost 86dB (106dBm-20dBm). The RF signal passing through the reception antenna 111 is separated into a transmission signal and a reception signal while passing through the duplexer 112. The duplexer 112 is a type of filter having a transmission frequency band and a reception frequency band as a pass band. The signal passed through the duplexer 112 passes through a low noise amplifier (LNA) 113, where the amplified RF signal is passed through a down converter 115 through an RF image filter RF BPF 114. Is entered. Here, the RF signal is mixed with the frequency of the local oscillator 116 and down to an intermediate frequency (IF). The intermediate frequency IF signal is input to an intermediate frequency filter IF BPF 117. In the path up to now, the range of the maximum and minimum values of the received signal is maintained as it is, and there is only a slight variation in size. The IF signal band-filtered by the intermediate frequency filter 117 is input to an automatic gain control amplifier (AGC AMP) 118.

Herein, the operation of the automatic gain control amplifier will be described with reference to the accompanying drawings.

The signal input to the automatic gain control amplifier 118 has a gain that varies from minimum to maximum according to the control voltage Vcontrol. For example, in the case of 211 of FIG. 2, the gain is -43 dB when the control voltage is low, and 43 dB when the control voltage is high. On the contrary, in the case of 212, the gain has 43dB when the control voltage is low and -43dB when the control voltage is high. The former method is called a positive control method, and the latter method is called a negative control method. That is, the positive control method is a method in which the gain increases when the control voltage increases, and the sub-control method is a method in which the gain decreases when the control voltage increases. In general, the method applied to the system is the positive control method in the case of 211 of FIG.

Referring back to FIG. 1, the automatic gain control amplifier has a minimum gain when the input is at a maximum value, and has a maximum gain when the input is at a minimum value. The IF signal passed through the auto gain control amplifier is input to an analog / digital converter (ADC) 120 through a demodulator 119 and converted into a digital signal.

In addition, the digital circuit controller 120 includes a circuit unit (received signal strength indicator; referred to as a received signal level indicator below RSSI) for determining the magnitude of the input signal, the voltage is different depending on the size of the input signal in the received signal level indicator Is applied to the automatic gain control amplifier 118 so that a signal of a constant magnitude is always input to the demodulator 119.

However, such a receiver has the following problems.

First, if the input dynamic range is wide, the output level should be constant by having a minimum gain when a large input comes in. This operation works inversely (convergence is needed but divergence occurs when using feedback. .) Large inputs sometimes go to larger levels.

Second, when the gain of the automatic gain control amplifier is largely changed in the gain, the output level must be constant. However, the output level fluctuates according to the ripple of the control voltage. In this case, if the demodulator goes beyond the limit of the desired level, a problem arises in restoring the signal. (Mainly, Amplitude Modulation Error occurs.)

Third, the control of the automatic gain control amplifier passes through the entire stage of the receiver and controls again due to the feedback effect. If the time taken to pass through the receiver stage and at least the time taken from the digital control circuit is long, the incoming signal passes. The following control can occur, in which case a part of data cannot be demodulated.

Accordingly, an object of the present invention is to provide an apparatus capable of effectively obtaining a constant reception level by implementing an amplifier for gain control in a receiver of a mobile communication system as an analog automatic gain control amplifier and a digital automatic gain control amplifier.

In order to achieve the above object, a reception level control apparatus of a mobile communication system receiver includes an analog automatic gain control amplifier which reduces an input dynamic range of a received signal to a predetermined size through its feedback, and an input dynamic range reduced to the predetermined size. The digital auto gain control amplifier is configured to double the gain control to obtain the final received signal level.

1 is a block diagram of a receiver having a general automatic gain control amplifier according to the prior art.

FIG. 2 is a graph illustrating gain characteristics according to a control voltage of an automatic gain control amplifier in FIG. 1. FIG.

3 is a block diagram of a receiver having a dual automatic gain control apparatus according to an embodiment of the present invention.

4 is a graph illustrating a convergence process of an input dynamic range according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, in adding the reference numerals to the components of each drawing, the same components have the same reference numerals as much as possible even if displayed on different drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

3 shows a configuration of a receiver used in a mobile communication system according to an embodiment of the present invention.

The receiver includes an antenna (ANT) 211, a duplexer 212, a low noise amplifier 213, an RF image filter (RF BPF; 214), a down converter (MIXER; 215), a local oscillator (216), an intermediate frequency. Filter (IF BPF) 217, primary automatic gain control amplifier 218a (analog automatic gain control amplifier), secondary automatic gain control amplifier 218b (digital automatic gain control amplifier), demodulator 219, digital circuit controller ( 220). Here, the digital circuit controller 220 measures a magnitude of a received signal and converts a received signal level indicating unit (RSSI) for applying a control voltage to the secondary automatic gain control amplifier and a digital control voltage into an analog electrical signal. Digital / analog converter and the like.

Referring to FIG. 3, first, an RF signal received by the antenna 211 is transmitted / received through the duplexer 213 and amplified by the low noise amplifier 113. The amplified signal is band-pass filtered through the RF image filter 214 and then down-converted to an intermediate frequency through the down-converter 215 and band-filtered by the intermediate frequency filter 217. Up to this point, the operation is the same as in the prior art, but there is a change in the magnitude of the input signal, but the dynamic range is maintained between the maximum and minimum values of the input signal level.

The input signal is input to the primary automatic gain control amplifier 218a via the intermediate frequency filter 217. The dynamic range of the input signal is reduced by a predetermined level by giving an analog feedback in advance. In the present embodiment, the body feedback range is set to ± 13dB, and assuming that the input dynamic range is ± 43dB as shown in FIG. 1, the numerical results are described as follows. In other words, the maximum input value of -106dBm has a gain of + 13dB and has a value of -93dBm, and the minimum input value of -20dBm has a gain of -13dB and a new gain level of -33dBm.

As a result, the secondary automatic gain control amplifier 218b of FIG. 3 has a new input dynamic range, which is represented numerically as -33dBm to -93dBm and has a range of ± 30dB. What is new here is that the value of the highest level that can be applied to the secondary automatic gain control amplifier 218b is -33dBm adjusted by -13dB from -20dBm. The level becomes the largest input level of FIG. 3 which is instantaneously inputted before reaching the steady state, which is a low level value compared to the highest value of the input dynamic range of the prior art, so that the input condition can be more relaxed. That is, the width of the dynamic range input to the automatic gain control amplifier can be reduced rather than the prior art. In other words, the margin of the input condition can be increased when designing the system. Of course, the output condition of the secondary automatic gain control amplifier 218b of Figure 3 is the same as in the prior art.

The initial input signal is passed through the secondary automatic gain control amplifier 218b as it is and is input to the demodulator 219. In this case, since there is no value fed back from the digital circuit controller 220, the input signal is input to the received signal level indicating circuit RSSI. The received signal level indicating circuit generates digital voltage data that can control the secondary automatic gain control amplifier according to the magnitude of the input signal, and this value is obtained through a digital / analog converter (D / A converter). The signal is converted into an analog signal and input to the control voltage Vcontrol terminal of the secondary automatic gain control amplifier 218b. The secondary automatic gain control amplifier 218b receiving the control voltage adjusts the current input signal using the control voltage as a bias voltage and outputs the level to the demodulator 219.

The difference from the prior art here is that the input dynamic range to be processed in the secondary automatic gain control amplifier is adjusted in advance by the primary automatic gain amplifier 118a of FIG. 3, so that the range (width) to be processed is reduced. . Therefore, if the secondary automatic gain control amplifier 218b adjusts the gain again from the adjusted value, a more stable level can be made.

When the above-described embodiment is represented graphically, it is as shown in FIG. 4.

4a shows the initial input dynamic range input to the primary automatic gain control amplifier 218a. Numerically, it ranges from -106dBm to -20dBm, representing 86dB (± 43dB). 4b shows a form in which gain is primarily adjusted while passing through the first automatic gain control amplifier 218a. In the present embodiment, since the analog automatic gain amplifier 218a adjusts gain of ± 13 dB, the signal input to the secondary automatic gain control amplifier 218b via the primary automatic gain control amplifier 218a is therefore input. The dynamic range is from -93dBm to -33dBm with gain adjustment of ± 13dB over the original input range, such as 4b. 4c shows the form in which the input signal converges to a predetermined level while the input signal passes through the secondary automatic gain control amplifier 218b. That is, the signal input from the intermediate frequency filter 217 is amplified or attenuated to a predetermined level while passing through the primary automatic gain control amplifier 218a and the secondary automatic gain control amplifier 218b and input to the demodulator 219. do.

Here is a numerical example to help better understanding.

If the control voltage condition of FIG. 1 (prior art) adjusts the dynamic range of ± 43 dB from 0.5 V to 2.5 V, the ΔdB / ΔV (change in gain that must be responded per unit voltage) reaches almost 43 dB. . However, this is not the case in the secondary automatic gain control amplifier 218b of FIG. 3 (invention). That is, since the analog self-feedback is performed in front of the second automatic gain control amplifier 218b in advance, ΔdB / ΔV is reduced to 30dB if the conditions of the control voltage are the same. This can be adjusted by the automatic gain control amplifier 118 of FIG. 1 when the number of branches that the received signal level indicating circuit RSSI included in the digital circuit controller 220 can generate is 256 (assuming 8 bits of expression bits). This means that the variable width of the minimum condition of the RSSI is greater than the variable width of the minimum condition of the secondary automatic gain control amplifier 218b of FIG. 3. This can be explained by dividing the input signal level into a convergent process by increasing the width in the process of converging the predetermined signal level to a predetermined level and by converging by decreasing the width. If the convergence is made with a smaller width, the output level of the automatic gain control amplifier in the steady state will be much more stable.

As described above, in the present invention, in a system having a wide dynamic range, a gain adjustment for delivering a constant level input signal to a demodulator is performed in advance by analog gain adjustment and the RSSI (receive signal level indicating circuit of the digital circuit controller) is controlled. You can adjust the level more precisely by adjusting the range of. This can also reduce other error rates in the size demodulation that may occur in the demodulator. And the stability of the convergence will also be better (the stability of the convergence is treated the same as the stability of the whole system) and the reverse divergence that has been addressed by the problems of the prior art reduces the conditions that the automatic gain control amplifier has to deal with. As can be much improved.

Claims (3)

In the reception level control apparatus of a mobile communication system receiver, An analog automatic gain control amplifier that reduces the input dynamic range of the received signal to a predetermined size through its own feedback, and performs gain adjustment again on the input dynamic range reduced to the predetermined size to obtain a final received signal level to be obtained. Dual automatic gain control device through analog and digital loop, characterized in that the dual configuration of the digital automatic gain control amplifier. In the reception level control apparatus of a mobile communication system receiver, An analog automatic gain control amplifier for gain adjustment of the received signal passing through the intermediate frequency filter by analog self feedback; Analog and digital, characterized in that it consists of a digital automatic gain control amplifier for controlling the gain of the signal primarily adjusted by the analog automatic gain control amplifier to a predetermined level according to the control voltage applied from the digital circuit control unit to pass to the demodulator. Dual automatic gain control device through loop. The method of claim 1, The digital circuit controller, A reception signal level indicating unit for generating a digital control data corresponding to a control voltage to be applied to the digital automatic gain control amplifier according to a signal size input from the demodulator; And at least a digital / analog converter converting the digital numerical data generated from the received signal level indicating unit into an analog electrical signal and applying the same to the digital automatic gain control amplifier. Device.

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