JP2014007618A - Wireless communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem of a wireless communication device that when a two-wave high frequency signal is generated, as a test signal, and inputted to a mixer circuit, and then secondary torsion is corrected by adjusting the parameters of the mixer circuit, circuit scale for generating the test signal increases thus increasing power consumption.SOLUTION: During a period when a high frequency signal 108 is not inputted to a frequency conversion unit 104, a DC test signal generation unit 107 generates a DC test signal 111, i.e., a DC signal for test, being inputted to the frequency conversion unit. The level of a DC component contained in an output signal from the frequency conversion unit 104, for the DC test signal 111 thus inputted, is detected in a detection unit 105. A control unit 106 controls the parameters of the frequency conversion unit 104 based on the level of a DC component thus detected.

Description

  The present invention relates to a wireless communication device used in a wireless communication system.

  As a wireless communication device used in a wireless communication system, for example, a direct conversion method is known as a device that meets the demands for downsizing, weight reduction, and cost reduction of the device. In such a direct conversion wireless communication apparatus, a received radio frequency (RF) signal and a local oscillator signal having the same frequency as the RF signal are mixed by a mixer circuit and directly converted into a baseband frequency. To demodulate the original signal.

  In a direct-conversion wireless communication apparatus, during reception, secondary distortion generated in the mixer circuit is mixed into a direct current (DC) component band, which is a desired wave band in the output of the mixer circuit, and reception quality is reduced. There was a problem of deteriorating.

  For example, in Patent Document 1, two high-frequency signals generated in a wireless communication apparatus are input to a mixer circuit as a test signal to detect a secondary distortion output level included in the mixer circuit output. The secondary distortion is reduced by controlling the bias of the mixer circuit according to the detected output level.

Japanese Patent No. 3672590

  However, in such a conventional wireless communication apparatus, it is necessary to separately provide a signal generation circuit having a transmitter and a mixer circuit in order to generate two high-frequency signals, which increases the circuit scale of the entire apparatus. However, there has been a problem that power consumption becomes high.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wireless communication apparatus that can achieve low power consumption with a small circuit scale.

  A wireless communication device according to the present invention includes a local signal generation unit that generates a local signal having the same frequency as an input high-frequency signal, and a frequency at which the input high-frequency signal is multiplied by the local signal and converted to a baseband signal A test signal generation unit that generates a test signal that is a DC signal for testing and inputs the test signal to the frequency conversion unit in a period in which the high-frequency signal is not input to the frequency conversion unit, and the input to the test signal A detection unit that detects a level of a DC component included in an output signal from the frequency conversion unit; and a control unit that controls a parameter of the frequency conversion unit based on the level of the DC component detected by the detection unit. It is characterized by that.

  According to the wireless communication apparatus of the present invention, since the DC signal is used as the test signal, the circuit scale for generating the test signal can be reduced, and the power consumption can be reduced.

1 is a diagram illustrating a configuration of a wireless communication device according to Embodiment 1. FIG. 5 is a flowchart of secondary distortion correction processing according to the first embodiment. FIG. 2 is a circuit diagram of a Gilbert cell mixer circuit according to the first embodiment. FIG. 3 is a circuit diagram of a DC test signal generator according to the first embodiment. FIG. 6 shows another configuration of the wireless communication apparatus according to the first embodiment. FIG. 6 shows another configuration of the wireless communication apparatus according to the first embodiment. FIG. 6 is a circuit diagram of a passive mixer circuit and a DC test signal generator according to the second embodiment.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a wireless communication apparatus according to the first embodiment. FIG. 2 is a flowchart of the secondary distortion correction process according to the first embodiment. FIG. 3 is a circuit diagram of a Gilbert cell mixer circuit according to the first embodiment. FIG. 4 is a circuit diagram of the DC test signal generator according to the first embodiment. FIG. 5 is a diagram illustrating another configuration of the wireless communication apparatus according to the first embodiment. FIG. 6 is a diagram illustrating another configuration of the wireless communication apparatus according to the first embodiment.

  The wireless communication apparatus includes an input terminal 101, a mixer 102, a local transmitter 103, a mixer circuit (frequency converter) 104, a detector 105, a controller 106, and a DC test signal generator (test signal generator). Part) 107 and an output terminal 110.

  An RF signal 108 that is a high-frequency signal received by an antenna (not shown in FIG. 1) is input to the input terminal 101.

  The mixer 102 is connected to the input terminal 101, the DC test signal generator 107, and the mixer circuit 104. When the RF signal 108 is input from the input terminal 101, the mixer 102 outputs the RF signal 108 to the mixer circuit 104.

  The local oscillator 103 is connected to the mixer circuit 104, generates a local signal 109 having the same frequency as the RF signal 108, and outputs the local signal 109 to the mixer circuit 104. Note that the frequency of the local signal 109 does not have to be exactly the same as the frequency of the RF signal 108 and may be slightly different.

  The mixer circuit 104 is connected to the mixer 102, the local oscillator 103, the output terminal 110, the detection unit 105, and the signal processing unit 106. When the RF signal 108 is input from the input terminal 101 via the mixer 102, the mixer circuit 104 performs frequency conversion (down conversion) on the RF signal 108 using the local signal 109 and outputs a baseband signal. That is, the mixer circuit 104 multiplies the RF signal 108 by the local signal 109 and converts the frequency into a baseband signal.

  Further, when the DC test signal 111 which is a DC signal as a DC current (or DC voltage) is input from the DC test signal generation unit 107 via the mixer 102, the mixer circuit 104 uses the local signal 109 to generate a frequency. Convert and output test output signal. The DC test signal 111 is a test signal for testing to cause the mixer circuit 104 to generate secondary distortion on a trial basis.

  The mixer circuit 104 has a voltage value when the RF signal 108 is not input from the input terminal 101 and the DC test signal is not input from the DC test signal generator 107, that is, when only the local signal 109 is input. Is output as a DC offset. The mixer circuit 104 may remove and output frequency components other than DC components, or may be removed by providing an LPF (Low Pass Filter) at the subsequent stage of the mixer circuit 104.

  The detection unit 105 is connected to the mixer circuit 104, the signal processing unit 106, and the output terminal 110, and is realized by, for example, an ADC (Analog Digital Converter). The detection unit 105 detects the DC offset output from the mixer circuit 104 and outputs the detected value to the control unit 106. Further, the detection unit 105 detects the secondary distortion included in the test output signal output from the mixer circuit 104, that is, the level value of the DC component, and outputs the detected value to the control unit 106.

  The control unit 106 is connected to the detection unit 105, the mixer circuit 104, and the detection unit 105, and is realized by, for example, a digital circuit. When the DC offset value is input from the detection unit 105, the control unit 106 instructs the DC test signal generation unit 107 to be activated. When the level value of the DC component included in the test output signal is input from the detection unit 105, the control unit 106 controls the parameters of the mixer circuit 104 to adjust the secondary distortion amount, that is, performs the secondary distortion correction process. Do. In addition, when the secondary distortion correction process is completed, the control unit 106 instructs the DC test signal generation unit 107 to stop. Details of the secondary distortion correction processing will be described later.

  The DC test signal generator 107 is connected to the signal processor 106 and the mixer 102 and generates (generates) a DC current or a DC voltage. When a start instruction is issued from the signal processing unit 106, the DC test signal generation unit 107 inputs a DC current or a DC voltage as a DC test signal 111 to the mixer circuit 104 via the mixer 102.

  Next, the operation of the first embodiment of the present invention will be described with reference to FIGS.

  First, processing when the wireless communication apparatus receives a desired signal from the outside will be described. In this case, the RF signal 108 is input from the input terminal 101 to the mixer circuit 104, and the mixer circuit 104 down-converts as described above, and outputs a baseband signal from the output terminal 110. At this time, the detection unit 105, the signal processing unit 106, and the DC test signal generation unit 107 do not operate.

  Next, the operation of the secondary distortion correction process will be described. The secondary distortion correction process is performed during a period when the wireless communication apparatus does not receive a desired signal from the outside. Therefore, the RF signal 108 is not input to the mixer circuit 104 during the secondary distortion correction process. Note that the local signal 109 is input to the mixer circuit 104 even during the secondary distortion correction process. When the RF signal 108 and the DC test signal 111 are not input to the mixer circuit 104 and the local signal 109 is input, the mixer circuit 104 outputs a DC offset (step S1). The detection unit 105 detects the DC offset and outputs the value to the control unit 106.

  The control unit 106 stores the DC offset value as the reference value Vref (step S2). In addition, the control unit 106 instructs to activate the DC test signal generation unit 107 (step S3).

  The DC test signal generator 107 that has received the activation instruction from the controller 106 generates a DC test signal 111 and inputs it to the mixer circuit 104 via the mixer 102 (step S4).

  When the DC test signal 111 is input from the DC test signal generator 107, the mixer circuit 104 performs frequency conversion processing and outputs a test output signal. The detection unit 105 detects the secondary distortion included in the test output signal and outputs it to the control unit 106 (step S5). That is, the detection unit 105 takes in the DC component level value of the test output signal and outputs it to the detected value control unit 106. At this time, since the detection unit 105 only needs to capture the level value of the DC component of the test output signal, there is no need to provide a bandpass filter in the previous stage or subsequent stage of the detection unit 105, reducing the circuit scale and reducing power consumption. can do.

  When the level value of the DC component of the test output signal is input, the control unit 106 sets the count to 1 (step S6) and controls the parameters of the mixer circuit 104. Here, as a parameter control method, for example, the bias voltage of each transistor of the transistor pair of the mixer circuit 104 may be changed, or the value is changed using the phase difference and amplitude difference of the local signal input of the mixer circuit 104 as parameters. You may let them. Further, the value may be changed using the load resistance as a parameter. Moreover, you may change the value combining these. That is, the control unit 106 minimizes the secondary distortion by changing the parameter values of the mixer circuit 104. Hereinafter, as a parameter control of the mixer circuit 104, a method of changing the bias voltage of the mixer circuit 104 will be described as an example. Although detailed description will be given later, in the mixer circuit 104 shown in FIG. 3, the voltage to the NMOS (negative channel metal oxide semiconductor) pair (309a and 309b, 309c and 309d) is a bias voltage, and the resistors 307a and 307b are loaded. The resistor and the differential local input terminal 311 correspond to local signal input locations.

  The control unit 106 shifts the bias voltage of the mixer circuit 104 from the initial value X0 by a predetermined value X1. The detection unit 105 takes in Vim2 (X1) which is the level value of the DC component of the test output signal, which is the output from the mixer circuit 104 at that time, and outputs it to the control unit 106 (step S7).

  The control unit 106 calculates the difference between the absolute values of the Vref value stored in step S2 and the Vim2 (X1) value (step S8). Next, if the calculated Vim2 (X1) is the minimum value, the control unit 106 stores the value X1 as the minimum value Xmin (step S9). Here, since it is the first loop, the control unit 106 stores X1 as Xmin, but a preset initial value may be set as Xmin.

  If the count value has not reached the total number of trials N (step S10-No), the control unit 106 updates the count (step S11), shifts the bias voltage from X0 by a predetermined value X2, and operates from step S7 to step S9. repeat. If the absolute value difference between the Vref value and the Vim2 (X2) value is smaller than the absolute value difference between the Vref value and the Vim2 (X1) value in step S9, the control unit 106 sets X2 as Xmin. Update.

  In this case, it can be said that the DC component of the secondary distortion is smaller when the bias voltage of the mixer circuit 104 is shifted by X2 from the initial value X0 than when the bias voltage is shifted by X1. Note that Vref is first captured in step S2 in order to distinguish between the DC component included in the secondary distortion of the mixer circuit 104 and the DC offset that the mixer circuit 104 originally has.

  When the processing from step S7 to step S11 is repeated and the count value reaches the total number of trials N (step S10-Yes), the control unit 106 shifts the bias voltage of the mixer circuit 104 by Xmin from the initial value X0. It is fixed (set) as it is (step S12). Then, the control unit 106 instructs to stop the DC test signal generation unit 107, and the DC test signal 107 is not input to the mixer circuit 104 (step S13). Thus, the secondary distortion correction process is completed.

  In addition, although the process from said step S6 to step S12 was demonstrated as a method of changing the bias voltage of the mixer circuit 104 here, it is not limited to this process. For example, the control unit 106 does not update the value of Xmin based on the difference between the absolute values of Vref and Vim2 (Xi), but stores all Xi tried N times, of which Vref Xi that has the smallest difference in absolute value between Vim2 and Vim2 (Xi) may be selected.

  Further, the control unit 106 may perform control so as to determine the amount of change in the bias voltage based on the difference from the target value. For example, when the bias voltage is changed in the positive direction in a certain step (i = c) and the difference between the absolute values of Vref and Vim2 (Xc) becomes large, the bias is applied in the next step (i = c + 1). Control such as greatly changing the voltage in the negative direction may be performed. By doing so, it becomes possible to speed up the convergence of the absolute value difference between Vref and Vim2 to the minimum value.

  Next, the operation at the circuit level will be described with reference to FIGS.

  The mixer circuit 104 shown in FIG. 3 is a so-called Gilbert cell type mixer circuit. In FIG. 3, an RF signal is input to a differential input terminal 312, and includes a pseudo differential pair 314 having NMOSs 308a and 308b, a switch stage 313 having NMOSs 309a, 309b, 309c, and 309d, and load resistors 307a and 307b. The baseband signal is output from the differential output terminal 310.

  The local signal is input from the differential local input terminal 311 and drives the switch stage 313 via the buffers 301a and 301b, the capacitors 302a and 302b, and the resistors 303a and 303b. Note that DC voltage sources 304 and 305 are connected to the resistors 303a and 303b, and a power supply terminal 306 is connected to the load resistors 307a and 307b.

  As an example of the secondary distortion correction processing, the method in which the control unit 106 controls the bias voltage of the mixer circuit 104 has been described as described above. Specifically, the control unit 106 (not shown in FIG. 3) An instruction is given to the DC voltage source 304. Then, the voltage of the DC voltage source 304 generates a potential difference in the gate bias of the NMOS pair (309a and 309b and 309c and 309d) in the switch stage 313. That is, the DC voltage source 304 corresponds to intentionally adding a differential mismatch to the switch stage 313.

  By generating the gate bias potential difference, the threshold value of the gate potential for turning on / off the NMOS 309 is shifted. As a result, the ON / OFF timings of the NMOS pairs (309a and 309b and 309c and 309d) are offset in a complementary manner, and the duty ratio is adjusted.

  In this way, the secondary distortion amount of the mixer circuit 104 is adjusted by intentionally adding a differential mismatch and adjusting the duty ratio.

  In FIG. 4, a DC test signal generator having resistors 403 a and 403 b, a variable current source 404, and a DC voltage source 407 is provided between the differential input terminal 405 to which the RF signal 108 is input and the mixer circuit 402. 408 is connected.

  During the secondary distortion correction processing period, the RF signal is not input from the differential input terminal 405 to the mixer circuit 402, and the DC test signal is input from the variable current source 404 of the DC test signal generator 408. The mixer circuit 402 mixes the input DC test signal and the local signal input from the local oscillator 401 and outputs a test output signal to the differential output terminal 406.

  As described above, according to the first embodiment of the present invention, the DC test signal 111 that is a direct current signal is used as a test signal for causing the mixer circuit 104 to experimentally generate the secondary distortion. In order to generate a DC test signal, it is only necessary to provide a simple DC test signal generation unit 107, the circuit scale of the entire wireless communication apparatus can be reduced, and power consumption can be reduced.

  Further, since the DC test signal 111 input to the mixer circuit 104 is a direct current signal, the DC component included in the test output signal of the mixer circuit 104 may be detected as a secondary distortion, and the detection unit 105 can be detected with high accuracy. This eliminates the need for a device and eliminates the need for a band-pass filter for capturing a specific frequency, so that the circuit scale can be reduced and power consumption can be reduced.

  1 has been described by way of example of the configuration shown in FIG. 1 as a wireless communication device, but as shown in FIG. 5, a low-pass filter 112 provided at a subsequent stage of the mixer circuit 104 and removes high-frequency components of a signal, and a low-pass filter 112 may be configured to include a variable gain amplifier 113 that is provided at the subsequent stage of 112 and that makes the output level of the input signal constant. By doing so, components in the band other than the low frequency band including the DC component included in the test output signal of the mixer circuit 104 can be removed or attenuated, so that the detection unit 105 can detect the level of the DC component included in the input signal. The value can be detected with high accuracy. Note that, in the configuration of the wireless communication apparatus illustrated in FIG. 5, portions corresponding to the configuration illustrated in FIG. 1 are denoted by the same reference numerals as those in FIG.

  As shown in FIG. 6, in addition to the low-pass filter 112 and the variable gain amplifier 113, an ADC 114 provided after the variable gain amplifier 113 for converting an analog signal into a digital signal and a demodulation process provided after the ADC 114 are performed. The structure provided with the demodulation part 115 may be sufficient. Note that, in the configuration of the wireless communication apparatus illustrated in FIG. 6, portions corresponding to the configuration illustrated in FIG. 1 or FIG. 5 are denoted by the same reference numerals as those in FIG.

  Note that the second-order distortion correction processing of the wireless communication device described so far can also be applied to a low-IF (Intermediate Frequency) wireless communication device. In an environment where the interference wave bandwidth is wide, there is a high possibility that the second-order distortion leaks into the desired wave bandwidth. This is particularly effective in LTE (Long Term Evolution) having a wide bandwidth of the order of MHz.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to the drawings. FIG. 7 is a circuit diagram of a passive mixer circuit and a DC test signal generator according to the second embodiment.

  The wireless communication apparatus according to the second embodiment is different from the first embodiment in that the mixer circuit 104 in FIG. 1, FIG. 5, or FIG. 6 is a passive mixer circuit shown in FIG. Since the configuration of the wireless communication device other than the mixer circuit 104 is the same as that of the first embodiment, the same reference numerals as those in FIG.

  The RF signal is input from the differential input terminal 701, is subjected to voltage / current conversion by the transconductance stage 712, and unnecessary DC components are removed or attenuated by the capacitor 704a. In the passive mixer circuit, the secondary distortion DC component generated in the transconductance stage 712 is removed by the capacitor 704a, so that the secondary distortion performance of the entire wireless communication apparatus can be improved.

  The local signal is input from the differential local input terminal 703 and drives the switch stage 709 via the capacitor 704b. The signal frequency-converted by the switch stage 709 is subjected to current / voltage conversion by a transimpedance stage 713 having resistors 710 a and 710 b and a differential operational amplifier 711, and is output from a differential output terminal 702.

  The DC test signal generation unit 714 includes resistors 705c and 705d, a variable current source 706, and a DC voltage source 708a. The DC test signal is transmitted between the capacitor 704a and the switch stage 709 from the variable current source 706. Supply directly. By doing so, the DC test signal is not removed by the capacitor 704a, and high secondary distortion performance as described above can be realized.

  A resistor 705b, a variable current source 707, a resistor 705a, and a DC voltage source 708 are connected to the switch stage 709, and the control unit 106 not shown in FIG. The amount of secondary distortion is adjusted by changing the bias voltage of each transistor of the transistor pair. As described above, the value may be changed using the phase difference and amplitude difference of the local signal input of the mixer circuit 104 as parameters, or the value may be changed using the load resistance as a parameter. Moreover, you may change the value combining these.

  As described above, according to the second embodiment of the present invention, a DC test signal that is a direct current signal is used as a test signal for generating secondary distortion on a trial basis in mixer circuit 104. In order to generate the DC test signal, it is only necessary to provide a simple DC test signal generation unit 714, and the circuit scale of the entire wireless communication apparatus can be reduced, and the power consumption can be reduced.

  Further, since the DC test signal input to the mixer circuit 104 is a DC signal, the DC component included in the test output signal of the mixer circuit 104 may be detected as a secondary distortion. And a band-pass filter for taking in a specific frequency is not necessary, so that the circuit scale can be reduced and the power consumption can be reduced.

  Further, since the DC component of the second order distortion generated in the transconductance stage 712 of the mixer circuit 104 is removed by the capacitor 704a provided in the subsequent stage of the transconductance stage 712, the second order as the entire wireless communication apparatus. Strain performance can be improved. Further, since there is no bias current of the transistor of the switch stage 709, the influence of flicker noise can be reduced.

  101 input terminal, 102 mixer, 103 local oscillator, 104 mixer circuit, 105 detector, 106 DC test signal generator, 108 RF signal, 109 local signal, 110 output terminal, 111 DC test signal, 112 low-pass filter, 113 variable Gain amplifier, 114 ADC, 115 demodulator, 301a-301b buffer circuit, 302a-302b capacity, 303a-303b resistance, 304 DC voltage source, 305 DC voltage source, 306 power supply terminal, 307a-307b resistance, 308a-308b NMOS, 309a to 309d NMOS, 310 differential output terminal, 311 differential local input terminal, 312 differential input terminal, 313 switch stage, 314 pseudo differential pair, 401 capacitance, 402 mixer circuit, 403a to 403b 404, variable current source, 405 differential input terminal, 406 differential output terminal, 407 DC voltage source, 408 DC test signal generator, 701 differential input terminal, 702 differential output terminal, 703 differential local input terminal, 704a to 704b capacitance, 705a to 705d resistance, 706 variable current source, 707 variable current source, 708a to 708b DC voltage source, 709 switch stage, 710a to b resistance, 711 differential operational amplifier, 712 transconductance stage, 713 transimpedance stage 714 DC test signal generator

Claims (6)

A local signal generator that generates a local signal having the same frequency as the input high-frequency signal;
A frequency converter that multiplies the input high-frequency signal by the local signal to convert it to a baseband signal;
A test signal generation unit that generates a test signal that is a DC signal for testing and inputs the test signal to the frequency conversion unit in a period in which the high-frequency signal is not input to the frequency conversion unit;
A detection unit that detects a level of a DC component included in an output signal from the frequency conversion unit with respect to the input test signal;
A wireless communication apparatus comprising: a control unit that controls a parameter of the frequency conversion unit based on a level of the DC component detected by the detection unit. The detection unit detects a DC offset output from the frequency conversion unit when the high-frequency signal and the test signal are not input to the frequency conversion unit,
The radio communication apparatus according to claim 1, wherein the control unit controls the parameter so as to reduce a difference in absolute value between the DC offset and the level of the DC component.   The wireless communication apparatus according to claim 1, wherein the control unit controls a bias voltage of the frequency conversion unit as control of a parameter of the frequency conversion unit.   The frequency converter is a passive mixer circuit in which a filter for attenuating a direct current component of a signal is provided before the test signal is input. Wireless communication device.   The radio communication apparatus according to claim 1, wherein the frequency conversion unit is a Gilbert cell type mixer circuit.   6. A low-pass filter provided at a subsequent stage of the frequency conversion unit and passing a low frequency band including at least a direct current component in the output signal from the frequency conversion unit. A wireless communication device according to 1.

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