JP2002335182A - Digital signal-receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide high-quality reception characteristic by a method where the influence of a secondary strain characteristic generated due to leakage of a transmitted signal from a transmission part is reduced, in a reception part of a direct conversion system. SOLUTION: Calibration means for a DC bias is installed at the input of a direct conversion mixer; and the DC bias is calibrated in advance, so that it corresponds to reception level and to a threshold level which is installed at transmitted power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a CDMA (Code Diode).
vision Multiple Access) receiver, for example, DS
(Direct Spread) -CDMA / FDD (Frequency Divisio
The present invention relates to a method and apparatus for performing stable reception in the (n Duplex) system.

[0002]

2. Description of the Related Art In 2000, as a next-generation mobile phone system, a universal mobile phone system was adopted.
MHz and transmission rate of 2000 bps
000 (International Mobil Tel
communication System) and ITU (International Teleco)
standardization work has been carried out in the Union. Several schemes have been proposed for IMT-2000, and a scheme called W-CDMA is one of them. The spread spectrum system applied to W-CDMA is a direct spread system (DS), and switching between an uplink channel and a downlink channel is separated by frequency in the FDD system. Therefore, there is no TDMA transmission / reception switching, and continuous reception or continuous transmission. Is performed. Various multimedia services are scheduled for IMT-2000, and miniaturization, weight reduction, and cost reduction of mobile receivers are required. In particular, miniaturization of the high-frequency part of the receiver has become important. Among them, the direct conversion method has attracted attention. FIG. 7 shows a configuration example of a mobile terminal using a direct conversion method in a receiving unit. In FIG. 7, 100 is an antenna, 1
01 is a duplexer, 102 is a low noise amplifier, 103,
104 is a frequency conversion circuit (direct conversion mixer), 109 is a local oscillator, 110 is a 90 ° phase shifter,
105 and 106 are baseband LPFs, 107 and 108
Is a baseband variable gain amplifier, 109 is a digital demodulation, 113 is a receiving unit, 201 is a power amplifier, 202 is a transmitting unit, 900 is a gain control terminal of a preamplifier, and 902 is a gain control terminal of a baseband variable gain amplifier. . In this embodiment, only the main functional units are shown, and peripheral circuit blocks for system control and the like and blocks after data processing are omitted. The modulated signal input from the antenna 100 is pre-amplified by the pre-amplifier 102, and the direct conversion mixers 103 and 104, the local oscillators 109 and 9
The signal is converted into a quadrature baseband signal by a 0 ° phase shifter 110, a desired signal band is extracted by baseband filters 105 and 106, and the baseband variable gain amplifiers 107 and 1 are extracted.
08, gain control is performed, and demodulation, despreading, and the like are performed by the digital demodulation 109 to obtain data and a clock signal. 3Gp
p (3rd Generation Partnernersh
DS-CDMA / FDD from IP Project) standard
In this system, 16 slots are transmitted with 10 mS as one frame, transmission power is controlled for each slot, and a guard time period of 25 μS × 2 as shown in FIG.
Reference numeral 9 controls the gain of the low-noise amplifier 102 and the baseband variable gain amplifiers 107 and 108 according to the reception level at the slot interval of the received signal or at the frame interval. In the direct conversion method, since the high-frequency signal is directly converted to the baseband frequency by the direct conversion mixers 103 and 104, there is no intermediate frequency. Therefore, the first mixer and the filter for removing the image are unnecessary, and the size can be reduced.

[0003]

As a general drawback of the direct conversion system, it is known that attention must be paid to the two-distortion characteristic. As an example of this, RF
MICROELECTRONICS, Prentic
e Hall PTR (1998) at p136. In W-CDMA, transmission and reception are performed simultaneously by continuous reception and continuous transmission, so that the transmission signal of the terminal itself becomes an interference wave during reception. Generally, where the received signal is low,
Since the transmission power is also expected to be high, a maximum interference wave occurs at the minimum reception sensitivity. According to the 3Gpp standard, the minimum receiving sensitivity is about -117 dBm, and the maximum of the transmission power is +21 dBm (class 4). The reception signal and the transmission signal are separated by the duplexer 101. The isolation between the transmission input port and the reception output port of the duplexer 101 is about 50 dB,
A transmission signal having a maximum of about −30 dBm leaks to the reception output port side. Therefore, at the minimum receiving sensitivity, about -117d
A desired signal of Bm and an interference signal of about -30 dBm are input to a direct conversion type receiving unit. The variable gain type low noise amplifier 102 arranged at the input of the receiving unit
At the minimum receiving sensitivity, a high gain is selected to obtain a good noise characteristic and a required amplitude, and a high IIP2 (second order intercept point) characteristic is required for the direct conversion mixer. When the reception signal level increases, the gain of the low noise amplifier is selected to be low, so that the requirement of the IIP2 characteristic of the direct conversion mixer also decreases. The distortion characteristic of the direct conversion mixer has a problem that a sufficient IIP2 cannot be obtained due to an imbalance of the input bias due to manufacturing variations or the like.

[0004] The object of the present invention is to pay attention to this point, and the DS-
It is an object of the present invention to provide a method and an apparatus for performing stable reception even in the CDMA / FDD system even when continuous reception and digitally controlled AGC are used.

[0005]

In order to solve the above problems, the present invention provides a means for adjusting a parameter of an input bias of a direct conversion mixer, a means for detecting a reception signal level, and a transmission signal level of a transmission unit. For controlling the input bias parameter of the direct conversion mixer according to the reception signal level and the transmission signal level. The input bias parameter is controlled by setting a threshold value for the reception signal level and the transmission signal level, and controlling the input bias parameter of the direct conversion mixer when the reception signal level is lower than the threshold value and the transmission signal level is higher than the threshold value. Further, the reception signal level is associated with the gain control of the low noise amplifier, and the parameter of the input bias of the direct conversion mixer is controlled when the gain of the low noise amplifier is equal to or higher than a threshold and the transmission signal level is equal to or higher than the threshold. The variable gain of the low noise amplifier is a step type for switching between high gain and low gain, and the parameter of the input bias of the direct conversion mixer is controlled when the gain of the low noise amplifier is high and the transmission signal level is equal to or higher than a threshold. The timing for performing the control is based on the slot or frame period of the received signal. When the low-noise amplifier has a low gain and the transmission signal level is equal to or higher than the threshold, the low-noise amplifier is switched to the high gain by the direct conversion. This is performed after parameter control of the input bias of the mixer is completed. Also,
The switching of the transmission signal level to the threshold or more when the low noise amplifier has a high gain and the transmission signal level is equal to or less than the threshold is performed after the parameter control of the input bias of the direct conversion mixer is completed.

A low-noise amplifier, a local oscillator for generating a local oscillation signal substantially equal to the center frequency of the received signal, a low-noise amplifier, first and second direct conversion mixers, and a direct conversion mixer The size of the receiver can be reduced by integrating the function of controlling the input bias parameter of the direct conversion mixer with a control signal by providing means for adjusting the input bias parameter.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a communication terminal according to an embodiment of the present invention. In the figure, the same numbers as those in the other figures indicate the same functional blocks, 120 and 121 are bias calibration means, system means, 300 is system control means, 901 is a bias calibration control signal, 903 is a gain control signal of a power amplifier. , 904 are control signals for digital demodulation. A general system control unit 300 and control signals to the receiving unit 113 and the transmitting unit 202 are omitted. The system control means 300 detects the gain state of the low-noise amplifier of the receiving unit and the transmission power state of the power amplifier based on the gain control signal 903 of the power amplifier 201 and the control signal 904 of the digital demodulation, and the bias calibration control signal 904 And controls the bias calibration means 120 and 121 to control the offset voltage of the input bias of the direct conversion mixer. The bias calibration control signal 904 is a bidirectional signal for reading an input bias offset voltage and writing an input bias adjustment. In the system control, a threshold is provided for the reception signal level and the transmission signal level. When the reception signal level from the digital demodulation 109 is equal to or less than the threshold and the transmission signal level of the power amplifier 201 is equal to or greater than the threshold, the bias calibration means 120 and 121 are used. Then, the offset voltage of the input bias is read by the bias calibration control signal 904, and then the data for adjusting the input bias is written in the direction to cancel the offset. Also, instead of the received signal level threshold, the gain of the low noise amplifier
The same effect can be obtained by setting (or AGC voltage) as a threshold value and controlling the input bias parameter of the direct conversion mixer when the gain of the low noise amplifier is equal to or greater than the threshold value and the transmission signal level is equal to or greater than the threshold value. .

FIG. 2 shows a bias calibration means 1.
It is a figure showing the example of 20 and 121. In the figure, the same numbers as those in the other figures indicate the same functional blocks, 300 and 319 are bias circuits, 301, 302, 303, 305, 306,
311, 312, 321, 322, 323, 324, 3
25, 326 are resistors, 307 and 327 are DACs, 308
And 328 are ADCs, 313, 314, 315, 316,
317 and 318 are transistors constituting a direct conversion mixer. The basic bias of the direct conversion 103 and 104 is the bias circuit 1
And 319 of the bias circuit 2 and generate the transistors 313 and 31 of the direct conversion mixer.
4,315,316,317,318. Also, the bias circuit 300 and the bias circuit 2
319 output the DACs 307 and 327 and the ADC3
08 and 328 are connected, the offset voltage of the bias circuit is detected by 308 of ADC1 and 328 of ADC2, and the cancellation of the offset voltage is generated by DACs 307 and 327, and resistors 301 and 302, 303, 304 and 321 322, 324, and 323 are superposed on the basic bias voltage.

FIG. 3 is a flowchart of the gain control of the low-noise amplifier of the present invention, and FIG. 4 is a flowchart of the output control of the transmitting section of the present invention. The control is performed based on the slot or frame period of the received signal.
In the embodiment of the present invention, when the low-noise amplifier has a high gain and the transmission signal level is lower than the threshold (401) and the transmission signal level is switched above the threshold (408), the parameter control of the input bias of the direct conversion mixer ends. This is performed later (406). In the embodiment of FIG. 4, when the low-noise amplifier is switched to the high-gain state with the low-noise amplifier having a low gain and the transmission signal level being equal to or higher than the threshold value (508), the parameter control of the input bias of the direct conversion mixer is completed. (506).

FIG. 5 is a block diagram showing another embodiment of the present invention. In the figure, the same numbers as those in the other figures indicate the same functional blocks, 122a and 122b indicate low-gain low-noise amplifiers, 102a and 102b indicate high-gain low-noise amplifiers, and the duplexer 101 outputs a balanced signal. Input to two sets of low noise amplifiers. The low-noise amplifier is configured to switch between high gain and low gain, and is a block configuration example selected by the gain control signal 900.

FIG. 6 shows a configuration suitable for IC integration by providing system control inside the IC in the IC implementation of the present invention, which is effective for downsizing the receiver.

[0013]

According to the present invention, there are provided means for adjusting a parameter of an input bias of a direct conversion mixer, means for detecting a reception signal level, and means for detecting a transmission signal level of a transmission unit. Level and
By controlling the input bias parameters of the direct conversion mixer in accordance with the transmission signal level, the input bias balance accuracy can be improved, and II
P2 characteristics can be improved.

The input bias parameter is controlled by setting a threshold value for the reception signal level and the transmission signal level. When the reception signal level is lower than the threshold value and the transmission signal level is higher than the threshold value, the input bias of the direct conversion mixer is controlled. The parameters are controlled, the received signal level is related to the gain control of the low-noise amplifier, and the variable gain of the low-noise amplifier is a step type for switching between high gain and low gain, thereby simplifying the control conditions.

The control is performed based on the slot or frame period of the received signal, and the low-noise amplifier is switched to the high gain when the low-noise amplifier has a low gain and the transmission signal level is equal to or higher than the threshold value. Is performed after the input bias parameter control is completed, and the switching of the transmission signal level to the threshold or more in a state where the low noise amplifier has a high gain and the transmission signal level is below the threshold is performed after the input bias parameter control is completed. By doing so, a malfunction can be prevented.

A low-noise amplifier, a local oscillator for generating a local oscillation signal substantially orthogonal to the center frequency of the received signal, a low-noise amplifier, first and second direct-conversion mixers, and a direct-conversion mixer The receiver can be miniaturized by providing a means for adjusting the input bias parameter and integrating the function of controlling the input bias parameter of the direct conversion mixer with a control signal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a communication terminal according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a bias calibration unit used in the present invention.

FIG. 3 is a flowchart of gain control of the low noise amplifier of the present invention.

FIG. 4 is a flowchart of output control of a transmission unit according to the present invention.

FIG. 5 is a block diagram showing a communication terminal according to another embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration in which system control is provided inside an IC of the present invention.

FIG. 7 is a block diagram of a communication terminal having a conventional direct conversion type receiving unit.

FIG. 8 is a diagram illustrating a relationship between DS-WCDMA / FDD frames, slots, and changes in transmission power.

[Explanation of symbols]

102: Low noise amplifier, 103, 104: Direct conversion mixer, 109: Local oscillator, 110: 9
0 ° phase shifter, 105, 106... Baseband LPF, 1
07, 108: baseband amplifier, 109: digital demodulation, 110: data processing, 111: level detection, 11
2. Frame / slot timing control, 113 receiving unit, 121 calibration, 201 power amplifier, 202 transmitting unit, 900 gain control terminal of low noise amplifier, 901 calibration signal terminal, 903
Baseband amplifier gain control terminal

Continued on the front page F term (reference) 5K011 DA01 DA03 DA05 DA12 DA13 DA21 EA03 FA09 GA05 GA06 JA01 KA04 KA14 5K052 AA14 BB02 BB07 CC06 DD01 EE13 FF11 GG26

Claims (9)

[Claims] 1. A digital signal receiving apparatus for transmitting and receiving a digitally modulated high frequency signal, comprising: frequency converting means for converting the frequency of a received signal; means for adjusting an input bias parameter of the frequency converting means; Means for detecting a signal level; and means for detecting a transmission signal level, wherein a parameter of an input bias of the frequency conversion means is controlled in accordance with the reception signal level and the transmission signal level. Digital signal receiving device. 2. A digital signal receiving apparatus for transmitting and receiving a digitally modulated high frequency signal, comprising: a low noise amplifier; a local oscillator for generating a local oscillation signal substantially equal to a center frequency of the received signal; A second frequency conversion unit, a unit for adjusting a parameter of an input bias of the frequency conversion unit, a unit for detecting a reception signal level, and a unit for detecting a transmission signal level of a transmission unit; And controlling a parameter of an input bias of the frequency conversion means in accordance with the transmission signal level. 3. The apparatus according to claim 1, wherein a threshold is provided for the reception signal level and the transmission signal level, and the parameter of the input bias of the frequency conversion means is controlled when the reception signal level is lower than the threshold and the transmission signal level is higher than the threshold. The digital signal receiving device according to claim 2. 4. The low noise amplifier is a variable gain amplifier,
The gain is controlled according to the reception signal level, and a threshold is provided for the gain of the low noise amplifier and the transmission signal level. When the gain of the low noise amplifier is equal to or higher than the threshold and the transmission signal level is equal to or higher than the threshold, the frequency conversion means is controlled. 4. The digital signal receiving device according to claim 2, wherein a parameter of an input bias is controlled. 5. The low-noise amplifier is a step-type variable gain amplifier for switching between high gain and low gain, wherein high gain and low gain are selected in accordance with a received signal level, and the gain of the low noise amplifier and the transmission signal are selected. 4. A parameter according to claim 2, wherein a threshold is provided for the level, and the parameter of the input bias of the frequency conversion means is controlled when the gain of the low noise amplifier is high and the transmission signal level is equal to or higher than the threshold. Digital signal receiver. 6. The digital signal receiving apparatus according to claim 2, wherein the parameter control of the input bias of the frequency conversion means is performed based on a slot or frame period of a received signal. . 7. The switching of the low-noise amplifier to a high gain in a state where the low-noise amplifier has a low gain and the transmission signal level is equal to or higher than a threshold value is performed after the parameter control of the input bias of the frequency conversion means is completed. The digital signal receiving device according to any one of claims 2 to 6, wherein 8. The switching of the transmission signal level above the threshold value when the low noise amplifier has a high gain and the transmission signal level is below the threshold value is performed after the parameter control of the input bias of the frequency conversion means is completed. Claims 2 to 6
The digital signal receiving device according to any one of the above. 9. A low-noise amplifier, a local oscillator for generating a local oscillation signal substantially orthogonal to the center frequency of a received signal, first and second frequency conversion means, and input bias parameters of the frequency conversion means. An integrated circuit for a digital signal receiving apparatus, comprising: means for adjusting the input bias of the frequency conversion means by a control signal.