JPH10290173A - Radio reception circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain the reception circuit with excellent immunity against cross modulation distortion caused by nonlinearity of an amplifier at output of a transmission signal by reducing a current consumption of the amplifier of the reception circuit. SOLUTION: The reception circuit for a radio communication equipment provided with a variable current amplifier 4 causing high linearity due to increase in the current consumption is provided with an IF band matching circuit 11 to conduct matching with an IF band of the reception circuit over a wide band, an IF band detection circuit 13 that detects reception power at the IF band, and a comparator 14 that compares an output signal from the IF band detection circuit 11 with a reception power signal from a base band and outputs a detection signal when the output signal of the IF band detection circuit is higher than the reception power signal from the base band, and the comparator 14 provides an output of a control signal to increase the current consumption of the variable current amplifier 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving circuit of a communication device for transmitting and receiving radio frequency signals, and more particularly to a radio receiving circuit in which cross-modulation distortion may occur due to non-linearity of a receiving amplifier.

[0002]

2. Description of the Related Art In the case of a communication device terminal, it is necessary to reduce the power consumption of a battery in order to use it for a long time. Especially,
Since the amplifier of the receiving unit is activated even during standby, the effect of low power consumption by this amplifier is great. Therefore, it is necessary to adjust the bias current to minimize the current consumption as much as possible. By the way, in a communication system in which transmission and reception are performed at the same time, there is an intermodulation distortion problem. More specifically, when a transmission signal of the own device leaked to the receiving side for some reason and an interference wave signal present near the desired received wave input from the antenna are input to the receiving side amplifier, the amplifier Causes cross-modulation distortion. If this intermodulation distortion overlaps the frequency of the desired received wave, it becomes an interference wave and degrades the S / N ratio.
As a result, the sensitivity of the receiver is reduced.

[0003] As one conventional countermeasure against the above-mentioned problem, there is known a method using an amplifier for switching linearity. The above-mentioned cross-modulation distortion occurs only when the terminal of the communication device outputs a transmission wave. Therefore, there is no need to consider cross-modulation resistance characteristics when a transmission wave is not being output, such as in a standby mode. in short,
It would be advantageous if an amplifier with high linearity during transmission and low linearity during non-transmission could be obtained. Such an operation is possible in a receiving circuit using a conventional variable current amplifier.

FIG. 4 is a functional block diagram showing an example of a main configuration of a conventional receiving circuit using a variable current amplifier. In the reference numerals in the figure, 1 is an antenna, 2 is an antenna duplexer, 3 is a power supply, 4 is a variable current amplifier, and 5 is R
F band filter, 6 is a local oscillator, 7 is a frequency mixer,
Reference numeral 8 denotes an IF (intermediate frequency) bandpass filter, 9 denotes a demodulator / baseband processing circuit, and S1 denotes a transmission on / off control signal.

[0005] In the receiving circuit shown in FIG.
The linearity of the variable current amplifier 4 is switched based on the transmission on / off control signal S1 output from the baseband processing circuit 9. The operation at the time of reception is as follows. The desired reception wave input from the antenna 1 passes through the antenna duplexer 2 and is input to the variable current amplifier 4,
The signal is amplified by the variable current amplifier 4. Thereafter, the signal passes through the RF bandpass filter 5 and is frequency-converted by the frequency mixer 7 into an IF signal which is an intermediate frequency. The received signal converted to the IF frequency passes through an IF band filter 8 and is sent to a demodulator / baseband processing circuit 9, where the demodulator / baseband processing circuit 9 performs demodulation processing and performs necessary demodulation. The signal is extracted.

The variable current amplifier 4 is controlled by the transmission on / off control signal S1 extracted in this manner,
The mode can be switched to the high current mode only during transmission. The connection of the control system is indicated by a broken line. When the current consumption increases, the variable current amplifier 4 has high linearity because the bias point moves. With the above operation, it is possible to switch between the two states of emphasizing the cross-modulation resistance and emphasizing the low current consumption.

[0007]

As described in the prior art, there is known a receiving circuit which achieves both the cross-modulation resistance and the low current consumption, and uses only a transmission on / off control signal S1. The bias point is being switched. But,
In the case of this conventional receiving circuit, even when the desired received signal level is sufficiently high, the mode can be switched to the high current mode, which leads to a problem that the power consumption increases accordingly. Such a problem similarly occurs when the transmission power is small. Further, the same occurs when no interference wave exists at a frequency near the desired reception signal. It is an object of the present invention to improve the conventional receiving circuit shown in FIG. 4 and to further promote compatibility between a long battery life due to low current consumption and anti-cross modulation characteristics. More specifically, a receiver circuit that reduces current consumption in the amplifier of the receiver circuit and has excellent resistance to cross-modulation distortion caused by the nonlinearity of the amplifier when outputting a transmission signal. As an issue.

[0008]

According to the first aspect of the present invention, in a receiving circuit of a wireless communication apparatus provided with a variable current amplifier having a high linearity due to an increase in current consumption, the I of the receiving circuit is reduced.
An IF band matching circuit for matching the F band in a wide band, an IF band detection circuit for detecting the reception power in the IF band, and a comparison between the output signal of the IF band detection circuit and the reception power signal from the base band. And a comparator for outputting a detection signal when the output signal of the IF band detection circuit is larger than the received power signal from the baseband, and the comparator outputs a control signal for increasing the current consumption of the variable current amplifier.

According to a second aspect of the present invention, a transmission power signal is compared with a transmission threshold value, and when the transmission power signal is larger than the transmission threshold value, a transmission power comparator for outputting a detection signal; The thresholds are compared, and when the reception power signal is smaller than the reception threshold, a reception power comparator that outputs a detection signal, a detection signal of the transmission power comparator, a detection signal of the reception power comparator, and an IF band A logic circuit for inputting a detection signal of a comparator that outputs a detection signal when an output signal of the detection circuit is larger than a reception power signal from the baseband, and increasing a current consumption of the variable current amplifier by the logic circuit A control signal to be output is output.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment The first embodiment mainly corresponds to the invention of claim 1, but also relates to the invention of claim 2 described in the second embodiment. The invention of claim 1 is a basic invention. According to the present invention, the fact that the cross-modulation distortion actually affects the deterioration of the reception sensitivity is remarkable when the desired reception signal level is low and the transmission power is high. Does not exist, cross-modulation distortion does not occur in principle irrespective of the transmission power level and the reception power level. It is not necessary to switch the variable current amplifier to the high current mode only when there is an interference wave near the desired reception wave, and by setting it to the low current mode otherwise, It enables both cross-modulation resistance and low current consumption characteristics. In the first embodiment, the variable current amplifier 4 is provided with a desired reception signal in order to achieve both the anti-cross modulation characteristics and the low current consumption characteristics in order to achieve both the anti-cross modulation characteristics and the low current consumption characteristics. Only when there is an interfering wave near the target signal, the mode is switched to the large current mode and the bias point is moved to improve the linearity to improve the cross-modulation resistance, and when there is no interfering wave near the desired received signal. Is characterized in that it is driven with low power consumption in a low current mode (small current mode).

FIG. 1 is a functional block diagram showing an example of an embodiment of a main configuration of a linearity switching section of a radio receiving circuit of the present invention. The reference numerals in the figure are the same as those in FIG. 4, 11 is an IF band matching circuit, 12 is a directional coupler, 13 is a detector, 14 is a comparator, and 15 is a received power information signal generator.

The wireless receiving circuit shown in FIG. 1 includes an IF band matching circuit 11, a directional coupler 12, a detector 13, and a comparator 14 in addition to the wireless receiving circuit shown in FIG.
And a received power information signal generator 15.
The connection of the control system is indicated by a broken line as in FIG. The functions of each newly added unit are as follows. The IF band matching circuit 11 has a function of matching the IF (intermediate frequency) band of the wireless reception circuit in a wide band (see FIG. 2 described later). The directional coupler 12 has a function of extracting a part of the received power from the received signal output from the IF band matching circuit 11 and passing most of the remaining power. The detector 13 detects the reception power in the IF band extracted by the directional coupler 12. Comparator 14
Compares the output signal of the detector 13 with the received power signal of the baseband output from the demodulator / baseband processing circuit 9, and when the output signal of the detector 13 is larger than the received power signal from the baseband, By outputting a control signal, the current consumption of the variable current amplifier 4 is increased, and the bias point is moved to achieve high linearity. The above is the outline of the functions of each newly added unit.

Next, the operation of the radio receiving circuit shown in FIG. 1 during reception will be described. In the wireless receiving circuit of FIG. 1 as well, the desired received wave input from the antenna 1 passes through the antenna duplexer 2 and is input to the variable current amplifier 4,
The signal is amplified by the variable current amplifier 4. Thereafter, the signal passes through the RF bandpass filter 5 and is frequency-converted by the frequency mixer 7 to the intermediate frequency IF. The configuration and operation up to this point
This is the same as FIG. The received signal converted to IF (intermediate frequency) in this way is sent to the IF band matching circuit 11 newly added in FIG. Here, the IF band matching circuit 11 will be described.

FIG. 2 is a diagram for explaining the pass characteristics of the IF band matching circuit 11. In the figure, the horizontal axis indicates the frequency of the IF band, the vertical axis indicates the amount of passed signal (dB), f0 is the intermediate frequency (the center frequency of the IF), fH is the upward frequency band near the IF, and fL is the lower frequency band near the IF. Indicates the directional frequency band.

In general, the IF band filter 8 has a very narrow band pass characteristic in order to pass only a desired reception signal converted into an intermediate frequency (a frequency band near the IF centered at f0 in FIG. 2). Have. On the other hand, the IF band matching circuit 11 added to FIG. 1 has a wider bandpass characteristic than the IF band filter 8 as shown in FIG. Therefore, components near the received signal converted into the intermediate frequency f0 (frequency bands fH and fL existing in both the upper and lower directions of the frequency band near IF in FIG. 2) are also passed. IF band matching circuit 1 having this wide band pass characteristic
1 is given to the directional coupler 12 of the next stage. The directional coupler 12 divides the input received signal and outputs a part of the power to the detector 13, but acts to output most of the remaining power to the IF band filter 8.

A part of the power output to the detector 13 is an output of the IF band matching circuit 11 having a wide band pass characteristic, and includes a desired reception signal (frequency band near the IF) and a frequency band in both the upper and lower directions. There is a possibility that both reception components corresponding to fH and fL (frequency band components fH and fL are interference waves and do not always exist) are included. Also, it is divided by the directional coupler 12,
The received signal that has passed through the IF band filter 8 is sent to a demodulator / baseband processing circuit 9 in the same manner as in FIG. 4 to perform demodulation processing and extract necessary signals. The demodulator / baseband processing circuit 9 detects the reception power of the desired reception wave in the baseband. The received power is only the power of the desired received wave, and the received power in the baseband is output to the received power information signal generator 15.

By performing such an operation,
From the reception power information signal generator 15, information on the reception level of the reception power in the baseband (referred to as a first reception level) is obtained. On the other hand, the reception output detected by the detector 13 includes the baseband reception signal and the reception signals included in the upper and lower frequency bands fH and fL as described with reference to FIG. there is a possibility. Therefore, from the detector 13, information on the reception levels (referred to as second reception levels) of two reception powers, that is, the reception power of the baseband and the reception power included in the frequency bands fH and fL in the upper and lower sides thereof. Is obtained.

Therefore, the first reception level (reception level of the reception power in the baseband) output from the reception power information signal generator 15 and the second reception level (two reception levels) output from the detector 13 And a power reception level). If there is no interfering wave near the desired received wave, the first received level and the second received level should be equal, and therefore they match.
In practice, it is unavoidable that some detection error occurs, so that both are almost equal. In this state, the comparator 14 outputs the detection signal of “L (low level)”. I do. This “L” (level) signal is, for example, an output signal of logic “0”.

On the other hand, when an interference wave exists near the desired reception wave, the second reception level is higher than the first reception level. Comparator 14 generates an "H (high level)" detection signal when an interference wave exists near the desired reception wave and the second reception level is higher than the first reception level. This “H” (level) signal is an output signal such as a logic “1” or several volts.
The output of the comparator 14 is supplied to the variable current amplifier 4, and when the detection signal is "L" (level), the output is switched to the low current mode in which low power consumption is emphasized.
When the level is "H" (level), the mode is switched to the large current mode in which the anti-cross modulation characteristic is emphasized, and the linearity of the amplifier is improved.

As described above, in the radio receiving circuit of the present invention, when an interfering wave exists near the desired received wave, the linearity of the variable current amplifier 4 is improved to improve the cross-modulation resistance, and conversely. When there is no interference wave near the desired reception wave, the power consumption is kept low. Therefore, as compared with the receiving circuit of FIG. 4 described in the conventional example, it is possible to more efficiently achieve a longer battery life due to lower current consumption and anti-cross modulation characteristics. In FIG. 1, in order to facilitate understanding of the operation principle of the present invention, an IF band matching circuit 1 is shown.
1 and the frequency mixer 7 are configured as separate blocks, but it is an easy matter in design to include the IF band matching circuit 11 as a part of the frequency mixer 7. However, the present invention is not limited to the case of FIG.

Second Embodiment This second embodiment corresponds to the invention of claim 2, but also relates to the invention of claim 1 described in the first embodiment. And it corresponds to an improved invention. In the first embodiment, the variable current amplifier 4 is set to the large current mode only when an interference wave is present in the vicinity of the desired reception signal in order to achieve both the anti-cross modulation characteristic and the low current consumption characteristic. By switching and moving the bias point, the linearity is improved to improve the cross-modulation resistance, and when there is no interference wave near the desired received signal, the case of driving with low power consumption in the low current mode will be described. did.

In the second embodiment, a radio receiving circuit is provided together with a transmitter to constitute one communication device. In the second embodiment, the wireless receiving circuit provided with the transmitter can achieve both the anti-cross modulation characteristic and the low current consumption characteristic, transmit with relatively large transmission power, and perform desired reception. Only when the power of the wave is relatively small, and only when there is an interference wave near the desired reception wave, by switching to the large current mode and moving the bias point, the cross-modulation resistance characteristic by high linearity is improved, All other cases are characterized in that they are driven with low power consumption in the low current mode.

FIG. 3 is a functional block diagram showing an example of the second embodiment of the main configuration of the linearity switching section of the radio receiving circuit of the present invention. The reference numerals in the figure are the same as those in FIG.
2 is a transmission power comparator, 23 is a transmission power information signal generator,
Reference numeral 24 denotes a transmission power threshold holding unit, reference numeral 25 denotes a reception power comparator, and reference numeral 26 denotes a reception power threshold holding unit.

As described above, the radio receiving circuit shown in FIG. 3 is provided with a transmitter to constitute a communication device. Therefore, in order to achieve both the anti-cross-modulation characteristic and the low current consumption characteristic, It is also necessary to consider the transmission power of the communication device. In the wireless receiving circuit shown in FIG. 3, the three-input logic circuit 21, the transmission power comparator 22,
The difference is that a transmission power information signal generator 23, a transmission power threshold holding unit 24, a reception power comparator 25, and a reception power threshold holding unit 26 are further added. In FIG. 3, the operation for detecting the presence or absence of an interfering wave near the desired received wave is basically the same as that in FIG. 1 described in the first embodiment.

The functions and operations of each unit newly added in FIG. 3 are as follows. Although the order is not specified, the threshold of the transmission power level is set in advance in the transmission power threshold holding unit 24. In FIG. 3, the demodulator / baseband processing circuit 9 has a function of outputting a signal related to transmission power information, and the signal related to the transmission power information is given to the transmission power information signal generator 23 and transmitted. A power information signal is generated. The transmission power comparator 22 includes a transmission power information signal provided from the transmission power information signal generator 23,
The transmission power level is compared with the threshold of the transmission power level held in the transmission power threshold holding unit 24. When the former transmission power information signal is larger, the comparison result is output as “H”.

On the other hand, the reception power threshold value holding unit 26
A threshold of the reception power level is set in advance from the reception signal level of the desired reception wave. The reception power comparator 25 compares the reception power information signal provided from the reception power information signal generator 15 of FIG. 1 with the threshold of the reception power level held in the reception power threshold holding unit 26. If the received power information signal is smaller, the comparison result is output as "H". The three-input logic circuit 21 is provided with outputs from a total of three comparators: a transmission power comparator 22, a reception power comparator 25, and the comparator 14 in FIG.
Note that the comparator 14 outputs the comparison result as “H” when an interference wave exists near the desired reception wave (when the second reception level is higher than the first reception level). Therefore, the three-input logic circuit 21 outputs 3 only when the signals of these three comparators 22, 25, and 14 are all "H".
The AND condition is satisfied, and the output becomes “H”.

When the three-and-condition is satisfied, transmission is performed at a relatively large transmission power (when the transmission power information signal is larger), and the reception power is relatively small (the reception power information signal is smaller). And when there is an interference wave near the desired reception wave. When the 3-and condition is satisfied, the output from the 3-input logic circuit 21
The variable current amplifier 4 is driven in a large current mode. As a result, the linearity of the variable current amplifier 4 is improved, and the cross-modulation resistance is emphasized. In all other cases, the output of the three-input logic circuit 21 is "L", the variable current amplifier 4 is driven in the low current mode, and low power consumption is emphasized. When the above operation is considered in terms of time, the rate at which the variable current amplifier 4 is driven in the large current mode can be reduced, and as a result, battery consumption can be saved due to low power consumption.

[0028]

According to the first aspect of the present invention, the linearity of the amplifier is improved only when an interference wave exists in a frequency band near the desired reception wave. Therefore,
In terms of time average, it is possible to satisfy both the anti-cross-modulation distortion characteristics and the low power consumption characteristics while minimizing the increase in current consumption.

According to a second aspect of the present invention, in the wireless receiving circuit of the first aspect, the transmission power is relatively large and the reception power is relatively small by using the transmission power information signal and the reception power information signal. The linearity of the amplifier is improved only when an interference wave exists in the vicinity. Therefore, in addition to the effect of the wireless receiving circuit of claim 1,
When viewed on a time average, it is possible to further suppress an increase in current consumption.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating an example of an embodiment of a main configuration of a linearity switching unit of a wireless reception circuit according to the present invention.

FIG. 2 is a diagram illustrating a pass characteristic of an IF band matching circuit 11;

FIG. 3 is a functional block diagram illustrating an example of a second embodiment of a main configuration of a linearity switching unit of the wireless reception circuit of the present invention.

FIG. 4 is a functional block diagram showing an example of a configuration of a main part of a conventional receiving circuit using a variable current amplifier.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 antenna 2 antenna duplexer 3 power supply 4 variable current amplifier 5 RF band filter 6 local oscillator 7 frequency mixer 8 IF band filter 9 demodulator / baseband Processing circuit, 11 ... IF band matching circuit,
12 directional coupler, 13 detector, 14 comparator, 1
5 ... received power information signal generator, 21 ... 3-input logic circuit,
Reference numeral 22: transmission power comparator, 23: transmission power information signal generator, 24: transmission power threshold holding unit, 25: reception power comparator, 26: reception power threshold holding unit

Claims (2)

[Claims] 1. A receiving circuit of a wireless communication apparatus including a variable current amplifier having high linearity due to an increase in current consumption, wherein an IF band matching circuit for matching an IF (intermediate frequency) band of the receiving circuit in a wide band. And an IF band detection circuit for detecting the reception power in the IF band; and comparing the output signal of the IF band detection circuit with the reception power signal from the baseband, wherein the output signal of the IF band detection circuit is When it is larger than the received power signal from baseband,
And a comparator for outputting a detection signal, wherein the comparator outputs a control signal for increasing current consumption of the variable current amplifier. 2. A transmission power signal is compared with a transmission threshold value.
When the transmission power signal is greater than the transmission threshold,
A transmission power comparator that outputs a detection signal, a reception power signal that compares a reception power signal with a reception threshold value, and outputs a detection signal when the reception power signal is smaller than the reception threshold value; The detection signal of the power comparator, the detection signal of the reception power comparator, and the detection signal of the comparator that outputs the detection signal when the output signal of the IF band detection circuit is larger than the reception power signal from the baseband. The radio receiving circuit according to claim 1, further comprising a logic circuit configured to output a control signal for increasing current consumption of the variable current amplifier.