JP2011015112A - Radio receiver - Google Patents

Abstract

In a direct conversion reception system in an FDD system, a radio technology capable of obtaining a required interference-resistant performance without a reception BPF is provided at low cost.
In a radio apparatus 100 of a direct conversion reception system, two or more reception mixers (first and second reception mixers 50, 50) having different second-order distortion performance (IP2 performance) are provided in order to improve anti-interference performance. 60), a booster circuit 40 that generates a high power supply voltage for realizing a (high IP2) reception mixer (second reception mixer 60) with high second-order distortion performance, and a reception mixer that switches between the reception mixers (50, 60) And a DSP 37 as switching control means. The DSP 37 switches the reception mixer according to the local station transmission output.
[Selection] Figure 3

Description

  The present invention relates to a radio receiver, and more particularly to a radio receiver using a direct conversion reception method in an FDD (frequency division duplex) method.

  In a broadband wireless system represented by WCDMA (Wideband Code Division Multiple Access), a configuration of a wireless device adopting a direct conversion reception method capable of an inexpensive circuit configuration is generalized. However, in the duplex system based on the FDD (Frequency Division Duplex) system, the self-station transmission carrier leak affects the reception performance (interference immunity performance), and there is a problem of how to avoid it.

  FIG. 1 shows a general configuration of a conventional WCDMA direct conversion reception system. FIG. 2 (a) is a diagram showing a process of deteriorating sensitivity due to second-order distortion when another interference wave (blocker) is input to the receiver in the state where the local station transmission carrier leak exists. . FIG. 2B is a diagram showing an interference generation product due to one-wave interference wave (blocker), which is one of the interference interferences that are problematic in the direct conversion reception system.

  As shown in FIG. 2A, when an interference wave (blocker) is input to the receiver at the same time as the desired wave in the local station transmission state, the wideband modulated local station transmission carrier leak is detected by envelope detection at the reception mixer. As a result, distortion that falls into the baseband band occurs, resulting in deterioration of sensitivity. Further, as shown in FIG. 2B, when a high level interference wave (blocker) is input to the receiving mixer together with the desired wave, distortion occurs due to the non-linearity of the receiving mixer, and in particular, the interference wave (blocker) is generated. In the case of a modulated wave, a distortion component is generated in the baseband band (DC to low frequency band) by envelope detection, and sensitivity deterioration occurs. Conventionally, in order to avoid interference, a countermeasure is generally taken by increasing the secondary distortion performance (IP2) of the receiving mixer.

  Originally, it is necessary to reduce the distortion of the reception mixer (high IP2) and suppress the occurrence of distortion, but in reality, it is difficult to improve the reception mixer due to restrictions such as current consumption. Therefore, in general, a filter for sufficiently attenuating the local transmission carrier leak is inserted. The required attenuation is performed by DUP (duplexer) transmission to reception isolation, and DUP isolation deficiency is compensated by reception BPF (bandpass filter) to suppress the level of distortion at the reception mixer. Has been. As a technique for reducing the influence of the secondary distortion characteristics, there is a technique disclosed in Patent Document 1. In the technique disclosed in Patent Document 1, DC bias calibration means is provided at the input section of the direct conversion mixer, and the DC bias is calibrated in advance in accordance with the threshold values provided for the reception level and transmission power. .

JP 2002-335182 A

  By the way, in the countermeasure of FIG. 2A, there is a problem that the reception BPF is required in addition to the DUP, resulting in high cost. Further, in the countermeasure of FIG. 2B, it is actually difficult to obtain the required performance due to restrictions such as current consumption and power supply voltage. Therefore, in the field of narrow-band radio systems such as commercial radios, the double superheterodyne reception system has become the mainstream, and the circuit scale constituting it is large, making it difficult to reduce costs. In the technique disclosed in Patent Document 1, the secondary distortion can be improved by adjusting the imbalance of the input bias. However, since the technique is not a technique for dealing with the local transmission carrier leak, the local transmission carrier leak is dealt with. In order to do so, there is a problem that a reception BPF is required.

  The present invention has been made in view of such a situation, and an object of the present invention is to provide, at a low cost, a radio technology capable of obtaining a required interference resistance performance without a reception BPF in a direct conversion reception system in the FDD system.

  An apparatus according to the present invention is a direct conversion radio receiver, and includes a plurality of reception mixers having different distortion performances and a control unit that switches the reception mixers.

  According to the present invention, it is possible to provide, at a low cost, a radio technology that can obtain the required interference resistance without receiving BPF in the direct conversion reception method in the FDD method.

It is a functional block diagram of the general radio | wireless machine of a direct conversion reception system based on a prior art. It is the figure which showed the process of the sensitivity degradation by the secondary distortion when the interference wave (blocker) based on a prior art is input into the receiver. It is a functional block diagram of the radio device of a direct conversion reception system concerning an embodiment. It is the figure which showed the receiving system paying attention to the signal path | route which the 1st receiving mixer based on embodiment is selected. It is the figure which showed the receiving system paying attention to the signal path | route which the 2nd receiving mixer based on embodiment is selected.

  Next, modes for carrying out the present invention (hereinafter, simply referred to as “embodiments”) will be specifically described with reference to the drawings. The embodiment described below relates to a technique for improving interference resistance in a direct conversion reception system, and the configuration thereof includes two or more reception mixers (low IP2, high IP2) having different second-order distortion performance (IP2 performance). Etc.) and a booster circuit that generates a high power supply voltage for realizing a reception mixer with high second-order distortion performance (high IP2), and a reception mixer switching control unit that switches the reception mixer to achieve the required anti-interference performance. ing. In the first embodiment, the reception mixer is switched in accordance with the local station transmission output, and in the second embodiment, the reception mixer is switched in accordance with the detection of the interference block.

<First Embodiment>
FIG. 3 is a functional block diagram illustrating a schematic configuration of the wireless device 100 that operates according to the direct conversion reception method according to the present embodiment. The radio apparatus 100 includes a transmission system 110, a reception system 120, and a DUP (duplexer) 10, and a transmission signal to be transmitted from an antenna and a reception signal received by the antenna are separated by the DUP 10.

  The transmission system 110 includes a BPF (Band Pass Filter) 22, a PA (Power Amplifier) 24, and an isolator 26. The BPF 22 performs band limitation processing on the signal acquired from the orthogonal transformer and outputs the result to the PA 24. The PA 24 amplifies the signal that has passed through the BPF 22 and outputs the amplified signal to the isolator 26. The isolator 26 outputs the signal from the PA 24 while blocking the signal from the DUP 10.

  The reception system 120 includes an LNA (Low Noise Amplifier) 31, a front switch 32, a first reception mixer 50, a second reception mixer 60, a rear switch 33, an LPF (Low Pass Filter; 34 a) from the upstream side (DUP 10 side). 34b), VGA (Variable Gain Amplifiers; 35a, 35b), AD (Analog / Digital Converters; 36a, 36b), DSP (Digital Signal Processor) 37, booster circuit 40 and local oscillator 55. Note that the first reception mixer 50 and the second reception mixer 60 have different distortion characteristics, and either one is selectively used.

  The LNA 31 selects and amplifies the input signal (high frequency signal) and outputs it to the pre-stage switch 32. At this time, the amplified signal is branched to the first and second paths 91 and 92. The signals of the first and second paths 91 and 92 are converted into quadrature baseband signals by the first reception mixer 50 and the phase shifter 52 or the second reception mixer 60 and the phase shifter 62.

  Here, the first receiving mixer 50 has a relatively low second-order distortion performance as compared with the second receiving mixer 60. The first reception mixer 50 includes a first low-output frequency conversion circuit 51a and a second low-output frequency conversion circuit 51b.

  Similar to the first reception mixer 50, the second reception mixer 60 includes a first high-output frequency conversion circuit 61a and a second high-output frequency conversion circuit 61b. The second receiving mixer 60 has a relatively high second-order distortion performance as compared with the first receiving mixer 50. In order to realize this characteristic, a power supply voltage of 3V is boosted to 6V by the booster circuit 40 and supplied to the second reception mixer 60. By adopting such a configuration, the second receiving mixer 60 is low enough to obtain a desired anti-interference performance even when the local transmission output is high with a sufficient dynamic range and current supply. Has second-order distortion (high IP2) performance.

  The pre-stage switch 32 includes a first pre-stage switch 32a of the first path 91 and a second pre-stage switch 32b of the second path 92, and a signal from the LNA 31 is input to each. The first front-stage switch 32a selects and outputs the signal from the LNA 31 by selecting either the first low-output frequency converter circuit 51a or the first high-output frequency converter circuit 61a. Further, the second pre-stage switch 32b selects and outputs the signal from the LNA 31 by selecting either the second low output frequency conversion circuit 51b or the second high output frequency conversion circuit 61b.

  The rear switch 33 includes a first rear switch 33a and a second rear switch 33b. The first post-stage switch 33a selects either the first low-output frequency converter circuit 51a or the first high-output frequency converter circuit 61a and outputs the selected signal to the LPF 34a. Similarly, the second post-stage switch 33b selects either the second low output frequency conversion circuit 51b or the second high output frequency conversion circuit 61b and outputs the selected low output frequency to the LPF 34b.

  The LPFs 34a and 34b filter desired signal bands in the respective paths (91 and 92) and output the filtered signal bands to the VGAs 35a and 35b. The VGAs 35a and 35b are baseband variable gain adjusting means and perform gain control. The ADs 36 a and 36 b perform AD conversion on the signals whose gains are controlled by the VGAs 35 a and 35 b and output the signals to the DSP 37.

  The DSP 37 performs demodulation processing, despreading processing, and the like to obtain a data signal and a clock signal. Further, the DSP 37 controls the operations of the front-stage switch 32 and the rear-stage switch 33 so that the first reception mixer 50 is in a state where the local station transmission output is low (hereinafter referred to as “low output state”) during standby and during communication. And the second reception mixer 60 is selected in a state where the local station transmission output is high during communication (hereinafter referred to as “high output state”).

  More specifically, as shown in FIG. 4, in the low output state, the DSP 37 is connected to the first low output frequency conversion circuit 51a with respect to the first front switch 32a and the first rear switch 33a. The control signal is output as follows. Similarly, the DSP 37 outputs a control signal to the second front-stage switch 32b and the second rear-stage switch 33b so as to be connected to the second low-output frequency conversion circuit 51b. That is, as a path through which a signal flows from the upstream side to the downstream side, the LNA 31, the first front-stage switch 32a, the first low-output frequency conversion circuit 51a, the first rear-stage switch 33a, the path 91a through which the signal flows through the LPF 34a, and the LNA 31 A path 92a through which a signal flows is formed through the second pre-stage switch 32b, the second low-output frequency conversion circuit 51b, the second post-stage switch 33b, and the LPF 34b. 4 and FIG. 5 described later show the reception system 120 of the wireless device 100, and a part of the configuration and reference numerals are omitted.

  On the other hand, in the high output state, as shown in FIG. 5, the DSP 37 controls the first front-stage switch 32a and the first rear-stage switch 33a to connect to the first high-output frequency conversion circuit 61a. Is output. Similarly, the DSP 37 outputs a control signal to the second front-stage switch 32b and the second rear-stage switch 33b so as to be connected to the second high-output frequency conversion circuit 61b. That is, as a path through which the signal flows from the upstream side to the downstream side, the LNA 31, the first front-stage switch 32a, the first high-output frequency conversion circuit 61a, the first rear-stage switch 33a, and the path 91b through which the LPF 34a flows, and the LNA 31 A path 92b through which a signal flows is formed through the second pre-stage switch 32b, the second high-output frequency conversion circuit 61b, the second post-stage switch 33b, and the LPF 34b.

  According to the wireless device 100 having the above configuration, the first reception mixer 50 (51a, 51b) is selected in the low output state in which the local station transmission output is low during standby reception and communication, thereby reducing power consumption. It is operated in the current mode of operation. Further, in communication and when the local station transmission output is high, the DSP 37 switches the reception mixer from the first reception mixer 50 to the second reception mixer 60 (61a, 61b). As described above, the second reception mixer 60 has a low second-order distortion characteristic as compared with the first reception mixer 50, and therefore, it is possible to ensure desired interference resistance performance. Further, when the local station transmission output becomes low during communication or when standby reception is performed, the DSP 37 switches the reception mixer to the first reception mixer 50 and shifts to the operation mode with low current consumption. In this way, it is possible to switch the reception mixer in a timely manner in accordance with the transmission output of the local station and to operate so as to ensure the required anti-interference performance, and to optimize power consumption. Further, it is possible to obtain the required anti-interference performance without providing a receiving BPF, and it is possible to provide a wireless device at a low cost.

<Second Embodiment>
The wireless device 100 according to the present embodiment can be realized with the same configuration as the wireless device 100 of the first embodiment. The difference is in the receiving mixer switching condition. In this embodiment, the receiving mixer (50, 60) is switched according to the interference block detected by the DSP 37. In the present embodiment, as shown mainly in FIG. 2B, it is assumed that when a high-level interference wave (blocker) is input to the reception mixer together with the desired wave, the performance improvement of the second-order distortion is realized. is doing.

  Therefore, in the wireless device 100, the DSP 37 determines the presence or absence of an interference wave (blocker), and selects the first reception mixer 50 when determining that there is no interference wave. As a result, it is operated in an operation mode with low current consumption. On the other hand, if the DSP 37 determines that a high-level interference wave (blocker) has appeared, the DSP 37 switches to the second reception mixer 60 (61a, 61b) as the reception mixer to be operated, thereby reducing the distortion, thereby improving the communication state. Hold.

  Further, the DSP 37 detects the interference wave at the appropriate time, and when the interference wave (blocker) disappears or when it is determined that the interference wave level is low, the first reception mixer 50 (51a) as the reception mixer to be operated. , 51b) to shift to an operation mode with low current consumption. In this way, only when a high level interference wave (blocker) appears, the reception mixer having a high distortion performance is selected to maintain communication.

  According to the present embodiment, as in the first embodiment, it is possible to adopt a direct conversion reception method even in a narrowband wireless system, and a wireless device can be provided at low cost.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of these components, and such modifications are also within the scope of the present invention. For example, in the above-described embodiment, two types of reception mixers that are symmetrical to each other are used. However, the present invention is not limited to this, and the reception mixers may be provided so as to have three or more types of distortion characteristics.

The features of the present embodiment are summarized as follows.
The wireless receiver according to the present embodiment is a direct-conversion-type wireless receiver, and includes a plurality of reception mixers having different distortion performances and control means for switching the reception mixers.
The control means switches the reception mixer according to the local station transmission output.
The control means selects a reception mixer with good distortion characteristics when the local station transmission output is high.
The control means switches the reception mixer according to the detection of the interference block.
The control means selects a reception mixer with good distortion characteristics when the detected interference block is large.
Further, the BPF for filtering the carrier leak of the local station transmission output is not provided in the previous stage of the reception mixer.

100 wireless device 110 transmission system 120 reception system 10 DUP
32 Pre-stage switch 32a First pre-stage switch 32b Second pre-stage switch 33 Rear stage switch 33a First rear stage switch 33b Second rear stage switch 37 DSP
40 Booster circuit 50 First reception mixer 51a First low output frequency conversion circuit 51b Second low output frequency conversion circuit 52, 62 Phase shifter 60 Second reception mixer 61a First high output frequency conversion circuit 61b 2High-frequency output frequency conversion circuit

Claims (1)

A direct conversion wireless receiver,
Multiple receiving mixers with different distortion performance,
And a control means for switching the receiving mixer.

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