JP2000244352A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To unnecessitate making the characteristics of a detecting means for detecting an amplitude value matching the characteristics of a variable amplifier for amplifying a received signal in a receiver for controlling the amplitude of the received signal to be a prescribed value. SOLUTION: The variable amplifier 1 amplifies the received signal; the detecting means 2 detects a voltage proportional to the amplitude of the signal amplified by the amplifier 1; a comparing means 3 compares the detected voltage by the means 2 with a reference voltage for attaining the target value and outputs the comparison result as a digital value. A feedback control means reduces the gain of the amplifier 1 when the absolute value of the detected voltage is larger than that of the reference voltage based on the digital value but increases the gain of the amplifier 1 when the absolute value of the detected voltage is smaller than that of the reference voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver for controlling an amplitude value of a received signal to a predetermined target value, and more particularly to a detecting means for detecting a voltage value proportional to the amplitude value of the received signal amplified by a variable amplifier. When the feedback control means performs feedback control of the gain of the variable amplifier based on the comparison result between the detected voltage value and the reference voltage value, for example, the input amplitude value of the detection means versus the detected voltage value characteristic and the control voltage value of the variable amplifier The present invention relates to a receiver that does not need to match the gain characteristic.

[0002]

2. Description of the Related Art For example, a radio receiver receives a signal transmitted by radio from a radio transmitter. In wireless communication, for example, when the distance between the wireless transmitter and the wireless receiver fluctuates, or when fading occurs,
The level of the wireless signal received by the wireless receiver is likely to fluctuate. For this reason, a wireless receiver is provided with, for example, an automatic gain control circuit, and the level of the received signal is controlled to a constant level by the circuit.

FIG. 4 shows a configuration example of an automatic gain control circuit provided in a radio receiver, and an operation example of the automatic gain control circuit will be described. This automatic gain control circuit is configured using a feedforward loop. First, a received signal is input to the variable gain amplifier 23, and a part of the received signal is input to the RSSI detection circuit 21.

Next, the RSSI detection circuit 21 outputs a DC voltage value proportional to the power level of the input signal to the control circuit 22.
Output to FIG. 5 shows the power level (input signal level) of the signal input to the RSSI detection circuit 21 and the RSSI of the signal.
3 shows an example of a relationship (input signal level vs. DC detection voltage value characteristic) with a DC voltage value (DC detection voltage value) output from the I detection circuit 21. Note that the horizontal axis of the graph shown in FIG. 7 indicates the input signal level [dBm], and the vertical axis indicates the DC detection voltage value [V].

Next, the control circuit 22 outputs a DC control voltage value based on the DC voltage value input from the RSSI detection circuit 21 to the gain control terminal of the variable gain amplifier 23, so that the amplitude value of the amplified received signal is reduced. The gain of the variable gain amplifier 23 is feed-forward controlled so as to reach a predetermined target value. Then, the variable gain amplifier 23 amplifies the input received signal with a gain controlled by the control circuit 22 and outputs the amplified signal.

FIG. 6 shows an example of the relationship between the DC control voltage value (control voltage value) input to the gain control terminal of the variable gain amplifier 23 and the gain of the variable gain amplifier 23 (control voltage value-gain characteristic). Is shown. Note that the horizontal axis of the graph shown in FIG. 7 indicates the control voltage value [V], and the vertical axis indicates the gain.

The control circuit 22 controls the amplitude of a signal output from, for example, the variable gain amplifier 23 so as to always be a certain target value, and realizes such control. Therefore, the input signal level of the RSSI detection circuit 21 versus the DC detection voltage value characteristic and the variable gain amplifier 2
The DC control voltage value obtained by matching the control voltage value to the gain characteristic of No. 3 is output to the variable gain amplifier 23. That is, in the automatic gain control circuit described above, the detection processing by the RSSI detection circuit 21, the control processing by the control circuit 22, and the amplification processing by the variable gain amplifier 23 are performed in parallel. It is necessary to determine the DC control voltage value to be output to the variable gain amplifier 23 in consideration of both the characteristics and the characteristics of the variable gain amplifier 23.

[0008]

However, for example, in the conventional automatic gain control circuit of the radio receiver as shown in FIG. 4, when controlling the gain of the variable gain amplifier 23 as described above, the RSSI detection circuit is used. It is necessary to accurately match the input signal level vs. DC detection voltage value characteristic of the variable gain amplifier 21 with the control voltage value vs. gain characteristic of the variable gain amplifier 23. If the matching is displaced, the amplitude value of the amplified received signal is reduced. There was a problem that it was impossible to accurately control the target value.

Here, in order to achieve the above-mentioned matching, R
It is desirable that both the input signal level vs. DC detection voltage value characteristic of the SSI detection circuit 21 and the control voltage value vs. gain characteristic of the variable gain amplifier 23 are linear characteristics. For example, as shown in FIG. The characteristic of the RSSI detection circuit 21 is such that the DC detection voltage value is always saturated when the input signal level is low or high. For this reason, it is very difficult to accurately match the relatively linear characteristic of the variable gain amplifier 23 with the characteristic of the RSSI detection circuit 21 as shown in FIG. 6, for example. Gain control has not been realized.

In order to accurately control the amplitude value of the amplified received signal as described above, it is necessary to accurately match the characteristics of the RSSI detection circuit 21 and the characteristics of the variable gain amplifier 23. However, there is a problem that the automatic gain control range cannot be expanded only by connecting the variable gain amplifiers 23 in multiple stages. The present invention has been made to solve such a conventional problem. When controlling the amplitude value of a received signal to a predetermined target value, for example, it is necessary to match characteristics as shown in the above-described conventional example. The aim is to provide a receiver without.

[0011]

In order to achieve the above object, the receiver according to the present invention controls the amplitude value of a received signal to a predetermined target value as follows. That is, the variable amplifier amplifies the received signal, the detection means detects a voltage value proportional to the amplitude value of the signal amplified by the variable amplifier, and the comparison means detects the voltage value detected by the detection means and a reference at which the target value is achieved. A voltage value is compared with a digital value (for example, “1 value” when “the detected voltage value is larger”,
When the detected voltage value is smaller, the value is output as “0 value”. When the absolute value of the detected voltage value is larger than the absolute value of the reference voltage value based on the digital value, the feedback control means changes the value. While the gain of the amplifier is reduced, if the absolute value of the detected voltage value is smaller than the absolute value of the reference voltage value, the gain of the variable amplifier is increased to increase the amplitude value of the amplified received signal to a constant target value, for example. Control to a value.

Here, as described above, the detecting means has a characteristic of outputting a voltage value proportional to the amplitude value of the input signal, for example. The coefficient of the proportional relationship may be a positive value or a negative value. In any case, as the amplitude of the signal amplified by the variable amplifier increases, the detection voltage increases. The absolute value of the value increases. Further, the feedback control means outputs the control value in a level range in which the gain of the variable amplifier can be controlled to the variable amplifier based on, for example, the control value (for example, control voltage value) of the variable amplifier versus the gain characteristic. Controls the gain of the amplifier.

As described above, in the configuration of the present invention, for example, although it is necessary to independently consider the characteristics of the detecting means and the characteristics of the variable amplifier, it is not necessary to match these characteristics. That is, in the present invention, as described above, the result of comparison by the comparing means is output to the feedback control means as a digital value, and the feedback control means performs feedback control based on the digital value. Even if the characteristics of the variable amplifier and the variable amplifier are set independently of each other, the accuracy of the feedback control does not deteriorate.

Therefore, in the present invention, it is not necessary to ensure the matching of the characteristics as shown in the above-mentioned conventional example, so that it becomes very easy to accurately control the amplitude value of the received signal to the target value. Further, since it is not necessary to ensure characteristic matching as described above, the automatic gain control range can be easily expanded by, for example, connecting variable amplifiers in multiple stages.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of an automatic gain control circuit provided in a wireless receiver according to one embodiment of the present invention. Since the main part of the present invention relates to a configuration for controlling the amplitude value of the received signal to a predetermined target value, illustration and description of other components of the radio receiver are omitted in this example.

The automatic gain control circuit shown in FIG. 1 is configured using a feedback loop. The automatic gain control circuit includes a variable gain amplifier 1 for amplifying a signal,
An AC amplitude detection circuit 2 for detecting an amplitude value of an AC signal as a voltage value, a comparison circuit 3 for comparing two voltage values, an up / down counter 4 for increasing / decreasing a count value,
A digital-analog converter 5 for converting a digital value to an analog value is provided.

The variable gain amplifier 1 has a function of inputting a signal (AC signal) received by the radio receiver, amplifying the received signal, and outputting the amplified signal. The gain of the amplification process by the variable gain amplifier 1 is controlled by a voltage value input to a gain control terminal of the variable gain amplifier 1 as described later. Also, in the automatic gain control circuit of this example,
An object of the present invention is to always control the amplitude value of a signal (amplified reception signal) output from the variable gain amplifier 1 to a certain target value. In this example, a variable amplifier that amplifies a received signal is configured by the variable gain amplifier 1 described above.

The AC amplitude detection circuit 2 receives, for example, a part of the signal output from the variable gain amplifier 1 and converts the AC amplitude value of the signal into a DC voltage value proportional to the AC amplitude value. It has a function of outputting a value to the comparison circuit 3 as a detection voltage value. FIG. 2 shows an AC amplitude detection circuit 2
The AC amplitude detection circuit 2 has a configuration of 2
It is composed of one resistor R1, R2, one diode D, and one capacitor C.

In the circuit shown in FIG.
2 and a capacitor C are connected to the output terminal of the diode D, and a signal (AC input signal) input from the variable gain amplifier 1 passes through the resistor R1 and the diode D, and is proportional to the amplitude value of the input signal. The output DC voltage value (DC output signal) is output to the comparison circuit 3.

In this embodiment, the AC amplitude detection circuit 2 detects the voltage value proportional to the amplitude value of the input signal as described above, thereby detecting the voltage value proportional to the amplitude value of the signal amplified by the variable amplifier. Detecting means for performing the detection.
In this example, a case where the proportional coefficient between the amplitude value of the signal input to the AC amplitude detection circuit 2 and the voltage value output corresponding to the amplitude value is a positive value will be described as an example.

The comparison circuit 3 compares the magnitude of a detection voltage value input from the AC amplitude detection circuit 2 with a predetermined reference voltage value. If the detection voltage value is larger than the reference voltage value, the comparison circuit 3 goes to a high (Hi) level. While a voltage value (for example, a voltage value of 5V or a voltage value of 3V) is output to the up / down counter 4, if the detected voltage value is smaller than the reference voltage value, the voltage is low (Lo).
It has a function of outputting a level voltage value (for example, a voltage value of 0 V) to the up / down counter 4.

Here, as the reference voltage value, a value that achieves the target value of the above-described automatic gain control circuit of the present embodiment is set. A value is set such that the target value is achieved when the voltage value matches the reference voltage value.

FIG. 3 shows an example of the configuration of the comparison circuit 3. The comparison circuit 3 includes one comparator 11. In the comparator 11 shown in the figure, a detection voltage value (input signal) output from the AC amplitude detection circuit 2
And a reference voltage value, and outputs a high-level or low-level voltage value (output signal) to the up / down counter 4 based on the comparison result of these voltage values.

In this embodiment, the comparing circuit 3 compares the two voltage values and outputs the comparison result as a digital value (high-level voltage value or low-level voltage value) as described above. And a comparison means for comparing the detected voltage value with the reference voltage value at which the target value is achieved and outputting a comparison result as a digital value. Note that the comparison circuit 3 of this example outputs a high-level voltage value when the detected voltage value is larger than the reference voltage value, and outputs a low-level voltage value when the detected voltage value is smaller than the reference voltage value. However, for example, the high level and the low level can be used in reverse.

The up / down counter 4 has a function of increasing (increasing) or decreasing (decreasing) the count value in synchronization with a clock timing inputted from an external digital clock, for example. In this example, while the count value is decreased when the voltage value input from the comparison circuit 3 is at a high level,
It has a function of increasing the count value when the voltage value is at a low level. The up / down counter 4 has a function of outputting the count value which goes up / down in this way to the digital-analog converter 5.

The digital-analog converter 5 performs a digital-analog conversion of the count value input from the up / down counter 4 to an analog DC voltage value, and outputs the analog DC voltage value to the gain control terminal of the variable gain amplifier 1. have. Note that the analog DC voltage value has, for example, a level range in which the gain of the variable gain amplifier 1 can be controlled (for example, an upper limit value and a lower limit value are set based on a control voltage value-gain characteristic of the variable gain amplifier 1). ) Is adjusted.

Here, in this embodiment, the configuration is such that the voltage value output to the gain control terminal of the variable gain control amplifier 1 and the gain of the variable gain amplifier 1 increase as the count value of the up / down counter 4 increases. Used. That is, in the up-down counter 4 of this example, when the detected voltage value is larger than the reference voltage value, the feedback control is performed to decrease the gain of the variable gain amplifier 1 by decreasing the count value, while the detected voltage value is lower than the reference voltage value. When the voltage value is smaller than the voltage value, feedback control for increasing the gain of the variable gain amplifier 1 by increasing the count value is performed.

In this embodiment, the up / down counter 4 controls the gain of the variable gain amplifier 1 based on the voltage value from the comparison circuit 3 as described above, so that it is based on the digital value output from the comparison means. If the absolute value of the detected voltage value is larger than the absolute value of the reference voltage value, the gain of the variable amplifier is decreased.If the absolute value of the detected voltage value is smaller than the absolute value of the reference voltage value, the gain of the variable amplifier is decreased. Feedback control means for increasing the size is provided.

With the above configuration, in the radio receiver of this embodiment, the AC amplitude detection circuit 2 detects a voltage value proportional to the amplitude value of the reception signal amplified by the variable gain amplifier 1, and the comparison circuit 3 detects the detected voltage value. The value is compared with the reference voltage value, and the up / down counter 4 feedback-controls the gain of the variable gain amplifier 1 based on the comparison result,
For example, the amplitude value of the amplified received signal can always be controlled to a constant target value.

Therefore, in the radio receiver of this embodiment, a digital value indicating whether the amplitude value of the signal output from the variable gain amplifier 1 is larger or smaller than the target value is always output from the comparison circuit 3 to the up / down counter 4. Since the up / down counter 4 always performs feedback control of the gain of the variable gain amplifier 1 so as to achieve the target value based on the digital value, for example, a level at which the gain of the variable gain amplifier 1 can be controlled. If the voltage value in the range is adjusted so as to be output from the digital-to-analog converter 5, the amplitude value of the amplified received signal can be accurately controlled to the target value.

For this reason, in the radio receiver of this embodiment, for example, the relationship between the amplitude value of the signal input to the AC amplitude detection circuit 2 and the voltage value output from the AC amplitude detection circuit 2 (input amplitude value versus It is possible to independently set the relationship (control voltage value vs. gain characteristic) between the control voltage value input to the gain control terminal of the variable gain amplifier 1 and the gain of the variable gain amplifier 1 (control voltage value characteristic). Yes, there is no need to match these properties.

As described above, in the radio receiver of this embodiment, it is not necessary to ensure the matching of the characteristics as shown in the above-mentioned conventional example, so that it is very difficult to accurately control the amplitude value of the received signal to the target value. Will be easier. Further, in the wireless receiver of this example, since it is not necessary to ensure the matching of the characteristics as described above, the automatic gain control range can be easily expanded by, for example, cascading variable amplifiers.

Further, for example, in the automatic gain control circuit shown in FIG. 4 according to the conventional example, since the RSSI detection circuit 21 is used, when the input signal level-DC detection voltage value characteristic is high input level and low input level, Although the saturation occurs, the radio receiver of this example uses the AC amplitude detection circuit 2 having a relatively linear input amplitude value-detection voltage value characteristic, so that high-precision feedback is performed. It is preferable because control can be realized.

Here, the feedback processing performed by the receiver according to the present invention may be, for example, a configuration in which the processor is controlled by executing a control program in a hardware resource including a processor and a memory. Also, for example, each functional unit for executing the processing may be configured as an independent hardware circuit.

Further, the receiver according to the present invention has a TD
Although it can be applied to fields using various communication systems such as the MA system, the FDMA system, and the CDMA system, controlling the amplitude value of a received signal to a constant target value by a receiver requires a plurality of different spreading methods. This is particularly important in wireless communication using a CDMA system in which carriers are multiplexed by codes. This is because the CDMA receiver demodulates the despread data corresponding to the spread code based on, for example, the timing at which the correlation peak between the received signal and the desired spread code is detected. This is because if the value fluctuates due to fading or the like, the correlation peak cannot be accurately detected.

In the radio communication using the CDMA system, since a signal spread over a wide band by a spread code is communicated, a signal component corresponding to each spread code in the received signal becomes small, and the amplitude value of the received signal becomes large. Amplification may be required. Therefore, it is very effective that the variable gain amplifier is connected in multiple stages and the automatic gain control range is easily expanded as in the receiver according to the present invention,
For example, when a communication method requiring a large dynamic range such as the W-CDMA method is used, a particularly great effect can be obtained.

The receiver according to the present invention can be applied to various devices such as a base station and a mobile station, and is not limited to a device having only a signal receiving function. The present invention is also applicable to a communication device having a function of transmitting and receiving signals. Further, the receiver according to the present invention can be applied to, for example, a device that receives a signal by wire.

[0038]

As described above, according to the receiver of the present invention, when controlling the amplitude value of a received signal to a predetermined target value, the detecting means is proportional to the amplitude value of the received signal amplified by the variable amplifier. A voltage value to be detected, the comparing means outputs a comparison result between the detected voltage value and the reference voltage value as a digital value, and the feedback control means feedback-controls the gain of the variable amplifier based on the digital value. For example, it is not necessary to match the input amplitude value-to-detection voltage value characteristic of the detecting means with the control voltage-value-gain characteristic of the variable amplifier, thereby making it possible to expand the automatic gain control range by, for example, using multiple stages of variable amplifiers. It will be easier.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an automatic gain control circuit provided in a receiver according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of an AC amplitude detection circuit.

FIG. 3 is a diagram illustrating a configuration example of a comparison circuit.

FIG. 4 is a diagram illustrating a configuration example of an automatic gain control circuit provided in a receiver according to a conventional example.

FIG. 5 is a diagram illustrating an example of input / output characteristics of an RSSI detection circuit.

FIG. 6 is a diagram illustrating an example of characteristics of a variable gain amplifier.

[Explanation of symbols]

1. Variable gain amplifier 2. AC amplitude detection circuit
3 ··· Comparison circuit, 4 ·· Up / down counter, 5 ·
Digital-analog converter, R1, R2, resistance
D diode, C capacitor, 11 comparator,

Claims (1)

[Claims] 1. A receiver for controlling an amplitude value of a received signal to a predetermined target value, a variable amplifier for amplifying the received signal, and a detecting means for detecting a voltage value proportional to the amplitude value of the signal amplified by the variable amplifier. Comparing means for comparing a detection voltage value detected by the detection means with a reference voltage value at which the target value is achieved, and outputting a comparison result as a digital value; and an absolute value of the detection voltage value based on the digital value. Feedback control means for decreasing the gain of the variable amplifier when the absolute value of the voltage value is larger than the absolute value of the variable amplifier, and increasing the gain of the variable amplifier when the absolute value of the detected voltage value is smaller than the absolute value of the reference voltage value; A receiver comprising: