JP2006129161A - Radio receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio receiver which enables the current consumption thereof to be reduced while preventing deterioration in receiving sensitivity. <P>SOLUTION: The radio receiver is provided with: a filter 3a for extracting a desired signal and a channel signal adjacent to the desired signal from a received signal subjected to frequency downconversion by an RF front-end circuit 2a; a level judgment circuit 4a for detecting an output signal of the filter 3a, comparing the detection result with a reference level and judging whether the detection result exceeds the reference level; a BB processing part 7 for detecting or demodulating a signal level of the desired signal and judging whether the signal level exceeds a fixed value; and a control circuit 1a for controlling current caused to flow to the RF front-end circuit 2a and the gain of the RF front-end circuit 2a in accordance with respective judgment results of the level judgment circuit 4a and the BB processing part 7. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wireless reception device mounted on a mobile communication device.

  A wireless receiver mounted on a mobile communication device has a radio frequency (RF) front-end circuit that amplifies a received signal from an antenna and down-converts the received signal. In mobile communication devices, the radio wave condition is likely to change, and an adjacent channel signal wave having a larger electric field strength than the desired signal wave may be mixed. The adjacent channel signal can be removed to some extent by a filter connected between the RF front end circuit and the baseband (BB) processing unit (see, for example, Non-Patent Document 1). When the signal level of the desired signal is much smaller than that of the adjacent channel signal, the distortion generated by the adjacent channel signal reaches the band of the desired signal, so that the reception sensitivity of the wireless reception device is deteriorated. Therefore, it is necessary to improve the distortion characteristics by increasing the amount of current supplied to the RF front end circuit. On the other hand, when the signal level of the desired signal is higher than that of the adjacent channel signal, the current consumption does not increase because there is no need to improve the distortion characteristics.

However, in order to prevent the reception sensitivity from deteriorating, it is required to always keep the distortion characteristics of the RF front-end circuit good. In particular, when using a wireless receiver that employs the direct conversion method in an actual radio wave environment where interference waves exist, the distortion of the mixer in the RF front-end circuit compared to a wireless receiver that employs the superheterodyne method. Characteristics are a problem. Therefore, the supply current to the RF front end circuit is kept at the maximum and the current consumption increases. As a result, in a cellular phone terminal or the like whose current consumption is limited, the operable time such as the call time and the standby time is shortened.
Shin'ichiro Azuma and others, A Digital Terrestrial Television (ISDB-T) Tuner for Mobile Applications, International Solid State Circuit Conference (ISSC) 2004 Session (SESSION) 15 Wireless Consumer (WIRELESS CONSUMER) IC 15.6, (USA), Institute of Electrical and Electronics Engineers (IEEE), February 17, 2004

  The present invention provides a wireless receiver capable of reducing current consumption while preventing deterioration of reception sensitivity.

  One aspect of the present invention is: (a) a filter that extracts a desired signal and an adjacent channel signal of the desired signal from a received signal after frequency down-conversion by a high-frequency front-end circuit; (b) an output signal of the filter is detected; A level determination circuit that compares the detection result with a reference level and determines whether the detection result exceeds the reference level; (c) Whether the signal level exceeds a certain value by detecting or demodulating the signal level of the desired signal A baseband processing unit for determining; (d) a control circuit for controlling the current flowing through the high-frequency front-end circuit and the gain of the high-frequency front-end circuit in accordance with the determination results of the level determination circuit and the baseband processing unit. The gist of the invention is that it is a wireless receiving device.

  According to the present invention, it is possible to provide a wireless reception device capable of reducing current consumption while preventing deterioration of reception sensitivity.

  Next, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings in this embodiment, the same or similar parts are denoted by the same or similar reference numerals.

  As shown in FIG. 1, the radio receiver according to the embodiment of the present invention includes an antenna 8, a radio frequency (RF) front end circuit 2a, a first baseband (BB) filter 5a, a second BB filter 5b, and a first BB variable. A gain amplifier 6a, a second BB variable gain amplifier 6b, a BB processing unit 7, a filter 3a, a level determination circuit 4a, and a control circuit 1a are provided. Note that FIG. 1 illustrates a wireless reception apparatus that employs a direct conversion method. Here, the “RF front-end circuit” means a circuit that amplifies at least the reception signal from the antenna 8 and down-converts the frequency of the amplified reception signal. The filter 3a extracts the desired signal and the adjacent channel signal of the desired signal from the received signal after frequency down-conversion by the RF front-end circuit 2a. Here, the “adjacent channel signal” means an interference signal in a frequency band closest to the frequency band of the desired signal. The level determination circuit 4a detects the output signal of the filter 3a, compares the detection result with a reference level, and determines whether or not the detection result exceeds the reference level. The BB processing unit 7 detects or demodulates the signal level of the desired signal, and determines whether the signal level exceeds a certain value. The control circuit 1a controls the current flowing in the RF front end circuit 2a and the gain of the RF front end circuit 2a according to the determination results of the level determination circuit 4a and the BB processing unit 7.

  The RF front end circuit 2a includes, for example, a low noise amplifier (LNA) 21 connected to the antenna 8, an RF filter 22 connected to the LNA 21, and an orthogonal demodulator 20a. The quadrature demodulator 20a is connected to the demodulation amplifier 23 connected to the RF filter 22, the first mixer 24a and the second mixer 26a connected to the demodulation amplifier 23, and the first mixer 24a and the second mixer 26a. A phase shifter 25a and a local oscillator 27a connected to the phase shifter 25a. That is, in the example shown in FIG. 1, the RF front end circuit 2a compliant with the quadrature phase modulation (QPSK) system is shown. For example, a band pass filter (BPF) can be used as the RF filter 22. For example, a low-pass filter (LPF) can be used as the first BB filter 5a, the second BB filter 5b, and the filter 3a.

  A reception signal from the antenna 8 is amplified by the LNA 21 and transmitted to the RF filter 22. The RF filter 22 attenuates signal components other than the frequency band used for communication. The output signal of the RF filter 22 is amplified by the demodulation amplifier 23 and transmitted to the first mixer 24a and the second mixer 26a. The phase shifter 25a converts a local oscillation signal having a frequency equal to that of the reception signal into two local oscillation signals that are 90 ° out of phase. The first mixer 24a and the second mixer 26a respectively mix the output signal of the demodulation amplifier 23 and two local oscillation signals having a phase difference of 90 ° to generate a first BB signal I and a second BB signal Q, respectively.

  Here, as an index for evaluating the performance of the radio receiving apparatus, there are an intermodulation characteristic, an adjacent channel sensitivity suppression characteristic, and the like. The intermodulation characteristic defines the reception performance when an interference signal is input to the adjacent channel and the next adjacent channel, and the adjacent channel sensitivity suppression characteristic is reception when an interference signal is input to the adjacent channel as shown in FIG. Specify performance.

  When a high level interference signal is input to the adjacent channel, as shown in FIG. 3, the LNA 21, the demodulation amplifier 23, the first mixer 24a, the second mixer 26a, etc. shown in FIG. Distortion occurs in the inside. Therefore, suppression of distortion caused by adjacent channel interference waves is most important in preventing deterioration of reception sensitivity of the wireless reception device. The current flowing through the LNA 21, the demodulating amplifier 23, the first mixer 24a, the second mixer 26a, and the like is controlled by the reference current from the control circuit 1a. By increasing the current flowing through the LNA 21, the demodulating amplifier 23, the first mixer 24a, the second mixer 26a, and the like, the distortion characteristics are maintained well.

  Moreover, the filter 3a shown in FIG. 1 is connected to a connection node between the first mixer 24a and the first BB filter 5a, for example. Alternatively, the filter 3a may be connected to a connection node between the second mixer 26a and the second BB filter 5b. Since the frequency of the first BB signal I or the second BB signal Q is sufficiently reduced, the desired signal and the adjacent channel signal can be extracted with high accuracy by the filter 3a. The level determination circuit 4a has an input connected to the output of the filter 3a and detects the output signal of the filter 3a. As a result, the larger signal level of the desired signal and the adjacent channel signal is detected. The level determination circuit 4a determines whether the larger signal level of the desired signal and the adjacent channel signal is higher than the reference level.

  Further, the first BB variable gain amplifier 6 a is connected between the first BB filter 5 a and the BB processing unit 7. The second BB variable gain amplifier 6 b is connected between the second BB filter 5 b and the BB processing unit 7. The first BB filter 5a extracts the frequency band component of the desired signal from the first BB signal I and transmits it to the first BB variable gain amplifier 6a. The second BB filter 5b extracts the frequency band component of the desired signal from the second BB signal Q and transmits it to the second BB variable gain amplifier 6b. The gain of the first BB variable gain amplifier 6a is controlled by the BB processing unit 7 and amplifies the output signal of the first BB filter 5a. The gain of the second BB variable gain amplifier 6b is controlled by the BB processing unit 7 and amplifies the output signal of the second BB filter 5b.

  Accordingly, the desired signal components of the first BB signal I and the second BB signal Q are mainly input to the BB processing unit 7. The BB processing unit 7 demodulates a desired signal and controls each circuit shown in FIG. Further, the BB processing unit 7 detects the signal level of the desired signal and determines whether or not the signal level of the desired signal exceeds a certain value.

  Further, the control circuit 1a shown in FIG. 1 selects one of the three operation modes shown in FIGS. 4A and 4B based on the determination results of the level determination circuit 4a and the BB processing unit 7, respectively. select. The “normal mode” is a mode in which the gain of the RF front end circuit 2a is controlled to a high gain and the RF front end circuit 2a is operated with a low current consumption. The “low distortion mode” is an operation mode in which the gain of the RF front end circuit 2a is controlled to a high gain, and the current consumption of the RF front end circuit 2a is increased. The “low gain mode” is a mode in which the gain of the RF front end circuit 2a is controlled to a high gain and the RF front end circuit 2a is operated with a low current consumption.

  As an example, if the reference level set in the level determination circuit 4a and the constant value set in the BB processing unit 7 are A [dBmmW], both the desired signal and the adjacent channel signal shown in FIG. Is smaller, the control circuit 1a operates the RF front end circuit 2a in the normal mode.

  On the other hand, as shown in FIG. 6, when the desired signal is larger than A [dBmm] and the adjacent channel signal is smaller than A [dBmm], the control circuit 1a selects the low gain mode. That is, if the gain of the RF front end circuit 2a is increased, distortion due to saturation of the desired signal occurs, and therefore it is desirable to operate the RF front end circuit 2a with a low gain. Further, since it is not necessary to suppress the distortion generated by the adjacent channel signal, the control circuit 1a operates the RF front end circuit 2a with low current consumption.

  Furthermore, as shown in FIG. 7, when the desired signal is smaller than A [dBmm] and the adjacent channel signal is larger than A [dBmm], the control circuit 1a selects the low distortion mode. This is for amplifying the signal level of the desired signal and suppressing distortion generated by the adjacent channel signal. As shown in FIG. 8, when both the desired signal and the adjacent channel signal are larger than A [dBmmW], the low gain mode is selected.

  As described above, in the low gain mode, the gain of the RF front end circuit 2a is controlled to a low gain. As an example, when the desired signal level in the received signal received by the antenna 8 shown in FIG. 1 is higher than the noise level, the power of the desired signal level and the noise level transitions as shown in FIG. On the other hand, FIG. 10 shows the transition of the desired signal level, the noise level, and the adjacent channel signal level when the desired signal level in the received signal received by the antenna 8 is smaller than the adjacent channel signal level. 9 (a) and 10 (a) show the output power of the antenna 8, FIGS. 9 (b) and 10 (b) show the output power of the LNA 21, and FIG. 9 (c) and FIG. 10 (c). 9D shows the output power of the RF filter 202, FIGS. 9D and 10D show the output power of the quadrature demodulator 20a, and FIGS. 9E and 10E show the first BB filter 5a and the The output power of the 2BB filter 5b is shown, and FIGS. 9 (f) and 10 (f) show the output powers of the first BB variable gain amplifier 6a and the second BB variable gain amplifier 6b.

  In FIG. 9, since the desired signal level is larger than the noise level, the first BB variable gain amplifier 6a and the second BB as shown in FIG. 9 (f) can be obtained even if the LNA 21 has a low gain as shown in FIG. 9 (b). A good signal-to-noise (S / N) ratio can be secured with the output power of the variable gain amplifier 6b. On the other hand, in FIG. 10E, the first BB filter 5a and the second BB filter 5b reduce the signal level of the adjacent channel signal. However, as shown in FIG. 10B, the desired signal level is not amplified because the LNA 21 has a low gain, and as shown in FIG. 10F, the first BB variable gain amplifier 6a and the second BB variable gain amplifier 6b. A sufficient S / N ratio cannot be secured with the output power of. Thus, when the adjacent channel signal level shown in FIG. 10 is larger than the desired signal level, the low gain mode cannot be adopted.

  Further, the control circuit 1 a shown in FIG. 1 includes a gain control circuit 11, a current control circuit 12, and a current supply circuit 13. The gain control circuit 11 has an input connected to the BB processing unit 7 and an output connected to the RF front end circuit 2 a and the current control circuit 12. The output of the current control circuit 12 is connected to the input of the current supply circuit 13. The output of the current supply circuit 13 is connected to the RF front end circuit 2a.

  The current supply circuit 13 supplies a current to the RF front end circuit 2a. The current control circuit 12 increases the current when it is determined that the detection result exceeds the reference level, and decreases the current when it is determined that the detection result is lower than the reference level. The gain control circuit 11 decreases the gain and current when it is determined that the signal level exceeds a certain value, and increases the gain when it is determined that the signal level is equal to or less than the certain value.

  Next, the operation of the wireless reception apparatus according to the embodiment of the present invention will be described with reference to the flowchart shown in FIG.

  (A) At the start of the operation in step S11, the control circuit 1a shown in FIG. 1 operates the RF front end circuit 2a in the normal mode. That is, the current control circuit 12 controls the supply current of the current supply circuit 13 to a low level as shown in FIG. Further, as shown in FIG. 4A, the gain control circuit 11 controls the gain of the RF front end circuit 2a to a high level.

  (B) In step S12, the level determination circuit 4a shown in FIG. 1 determines whether the signal level of either the desired signal or the adjacent channel signal exceeds the reference level. If it is determined that the signal level of either the desired signal or the adjacent channel signal exceeds the reference level, the process proceeds to step S13. On the other hand, if it is determined that the signal level of either the desired signal or the adjacent channel signal does not exceed the reference level, the process returns to step S11 and the normal mode is maintained.

  (C) In step S13, the control circuit 1a operates the RF front end circuit 2a in the low distortion mode. Specifically, when it is reported from the level determination circuit 4a to the current control circuit 12 that the signal level of any one of the desired signal and the adjacent channel signal exceeds the reference level, the current control circuit 12 is switched to FIG. ), The supply current of the current supply circuit 13 is increased. Further, as shown in FIG. 4A, the gain of the RF front end circuit 2a is maintained at a high level. When the gain of the RF front end circuit 2a is maintained at a high level and the current consumption shifts to a high level, the process proceeds to step S14.

  (D) In step 14, the BB processing unit 7 shown in FIG. 1 determines whether or not the signal level of the desired signal exceeds a certain value. Since the input to the BB processing unit 7 is mainly the desired signal component in the first BB signal I and the second BB signal Q, the BB processing unit 7 can detect the signal level of the desired signal. If it is determined that the signal level of the desired signal exceeds a certain value, the process proceeds to step S15. On the other hand, when it is determined that the signal level of the desired signal does not exceed a certain value, the process proceeds to step S16, and the low distortion mode is maintained.

  (E) In step S15, the control circuit 1a operates the RF front end circuit 2a in the low gain mode. Specifically, when it is reported from the BB processing unit 7 to the gain control circuit 11 that the signal level of the desired signal exceeds a certain value, the gain control circuit 11 The gain of the front end circuit 2a is controlled to a low gain. When the gain of the RF front end circuit 2a is controlled to a low gain, the current control circuit 12 operates the RF front end circuit 2a with low power consumption, as shown in FIG. 4B. When the gain and current consumption of the RF front end circuit 2a shift to a low level, the process proceeds to step S17.

  (F) In step S17, the level determination circuit 4a determines whether or not the signal levels of the desired signal and the adjacent channel signal are both equal to or lower than the reference level. If it is determined that the signal level of both the desired signal and the adjacent channel signal is below the reference level, the process returns to step S11 and shifts to the normal mode.

  Thus, the control circuit 1a increases the current consumption of the RF front end circuit 2a only when the desired signal is small and the adjacent channel signal is large. That is, the control circuit 1a operates the RF front end circuit 2a with low power consumption except when the desired signal is small and the adjacent channel signal is large. Therefore, according to the embodiment of the present invention, it is possible to provide a radio receiver capable of reducing the average current consumption of the RF front-end circuit 2a to about ½ while keeping the specifications of adjacent channel sensitivity suppression good. .

(First modification)
As shown in FIG. 12 as a first modification of the embodiment of the present invention, the filter 3b, the level determination circuit 4b, and the control circuit 1b may be mounted on a radio reception apparatus adopting a superheterodyne method. . That is, the filter 3b is connected to a connection node between the RF front end circuit 2b and the intermediate frequency (IF) signal processing circuit 9a. The filter 3b, the level determination circuit 4b, and the control circuit 1b operate in the same manner as the filter 3a, the level determination circuit 4a, and the control circuit 1a shown in FIG.

  The RF front-end circuit 2 b includes an LNA 21 connected to the antenna 8, a first BPF (image removal filter) 202 connected to the LNA 21, a mixer 204 connected to the first BPF 202, and a first BPF connected to the mixer 204. 1 oscillator 203. A configuration in which a BPF is further connected between the antenna 8 and the LNA 21 may be employed. The IF signal processing circuit 9a includes a second BPF (channel selection filter) 91a connected to the mixer 204, and an IF amplifier 92 connected to the second BPF 91a. The quadrature demodulator 20b is connected to the first mixer 24b and the second mixer 26b connected to the IF amplifier 92, the phase shifter 25b connected to the first mixer 24b and the second mixer 26b, and the phase shifter 25b. The second oscillator 27b is provided.

  Further, the received signal from the antenna 8 is amplified by the LNA 21 and transmitted to the first BPF 202. The first BPF 202 removes unnecessary spurious signals other than a predetermined band from the amplified received signal and transmits the result to the mixer 204. The mixer 204 generates an IF signal by mixing the output signal of the first BPF 202 and the oscillation signal from the first oscillator 203. The second BPF 91 a removes unnecessary spurious components other than the predetermined band from the IF signal and supplies the IF signal to the IF amplifier 92. The IF amplifier 92 amplifies the output signal of the second BPF 91a and supplies it to the quadrature demodulator 20b. The quadrature demodulator 20 b generates a first BB signal I and a second BB signal Q from the output signal of the IF amplifier 92.

  As described above, the current consumption can be reduced while preventing the reception sensitivity from deteriorating also in the radio reception apparatus adopting the superheterodyne system shown in FIG.

(Second modification)
As shown in FIG. 13 as a second modification of the embodiment of the present invention, the filter 3c, the level determination circuit 4c, and the control circuit 1b may be mounted on a radio reception apparatus adopting a superheterodyne method. . However, the point that the filter 3c is connected to the output of the quadrature demodulator 20b is different from FIG. Moreover, the point from which the 1st BB filter 10a and the 2nd BB filter 10b are connected between the orthogonal demodulator 20b and the BB process part 7 differs from FIG. The filter 3c, the level determination circuit 4c, and the control circuit 1b operate in the same manner as the filter 3a, the level determination circuit 4a, and the control circuit 1a illustrated in FIG. Other configurations are the same as those in FIG.

  When the second BPF 91b is not a channel selection filter but passes a nearby frequency band including the desired signal and an adjacent channel, the first BB filter 10a and the first BB filter 10a for extracting the desired signal between the quadrature demodulator 20b and the BB processing unit 7 A 2BB filter 10b is provided. Therefore, since the filter 3c extracts the desired signal and the adjacent channel signal from the first BB signal I or the second BB signal Q having a low frequency, the signal levels of the desired signal and the adjacent channel signal can be determined with higher accuracy than in FIG. .

(Other embodiments)
As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the above-described embodiment, the radio reception apparatus corresponding to the communication system adopting the QPSK system has been described as an example, but the present invention is not limited to the orthogonal modulation system. That is, any communication method may be used as long as the modulation signal includes an amplitude component and has a plurality of frequency channels in the system band.

  Each circuit other than the antenna 8 and the BB processing unit 7 shown in FIG. 1 can be monolithically integrated on the same semiconductor substrate and configured as a semiconductor integrated circuit. The same applies to FIGS. 12 and 13.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

It is a circuit block diagram which shows the structure of the radio | wireless receiver which concerns on embodiment of this invention. It is a schematic diagram which shows an example of the received signal of the radio | wireless receiver which concerns on embodiment of this invention. It is a schematic diagram which shows an example in case distortion arises in the received signal of the radio | wireless receiver which concerns on embodiment of this invention. It is a schematic diagram which shows the operation mode of the radio | wireless receiver which concerns on embodiment of this invention. It is a schematic diagram which shows an example of the relationship between the desired signal and adjacent channel signal in the received signal of the radio | wireless receiver which concerns on embodiment of this invention. It is a schematic diagram which shows an example of the relationship between the desired signal and adjacent channel signal in the received signal of the radio | wireless receiver which concerns on embodiment of this invention. It is a schematic diagram which shows an example of the relationship between the desired signal and adjacent channel signal in the received signal of the radio | wireless receiver which concerns on embodiment of this invention. It is a schematic diagram which shows an example of the relationship between the desired signal and adjacent channel signal in the received signal of the radio | wireless receiver which concerns on embodiment of this invention. It is a graph which shows the mode of the change of the signal level of each signal at the time of the low gain mode of the radio | wireless receiver which concerns on embodiment of this invention. It is a graph which shows the mode of the change of the signal level of each signal at the time of the low gain mode of the radio | wireless receiver which concerns on embodiment of this invention. It is a flowchart which shows the outline | summary of operation | movement of the control circuit which concerns on embodiment of this invention. It is a circuit block diagram which shows the structure of the radio | wireless receiver which concerns on the 1st modification of embodiment of this invention. It is a circuit block diagram which shows the structure of the radio | wireless receiver which concerns on the 2nd modification of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b ... Control circuit 2a, 2b ... High frequency (RF) front end circuit 3a-3c ... Filter 4a-4c ... Level determination circuit 7 ... Baseband (BB) processing part 11 ... Gain control circuit 12 ... Current control circuit 13 ... Current supply circuit

Claims (5)

A filter that extracts a desired signal and an adjacent channel signal of the desired signal from a received signal after frequency down-conversion by a high-frequency front-end circuit;
A level determination circuit that detects an output signal of the filter, compares a detection result with a reference level, and determines whether the detection result exceeds the reference level;
A baseband processing unit that detects or demodulates the signal level of the desired signal and determines whether or not the signal level exceeds a certain value;
A control circuit that controls a current flowing through the high-frequency front-end circuit and a gain of the high-frequency front-end circuit according to a determination result of each of the level determination circuit and the baseband processing unit. Wireless receiver.   The radio reception apparatus according to claim 1, wherein distortion characteristics of the high-frequency front-end circuit are controlled by the current.   The control circuit controls the gain to a high gain and decreases the current when the detection result is equal to or lower than the reference level and the signal level is determined to be equal to or lower than the predetermined value. The wireless receiver according to claim 2, wherein   The control circuit controls the gain to a high gain and increases the current when the detection result exceeds the reference level and the signal level is determined to be equal to or less than the predetermined value. The wireless receiver according to claim 2.   The control circuit controls the gain to a low gain and decreases the current when it is determined that the detection result exceeds the reference level and the signal level exceeds the fixed value. The wireless receiver according to claim 2.

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