JP2004128863A - Radio communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable maintenance of high communication quality by restraining variations of impedance in a mixer circuit of a receiving part at the time of a strong electric field and restraining deterioration of receiving property. <P>SOLUTION: The receiving part 14 of a radio communication apparatus is constituted by installing a low noise amplifier 21, a first mixer 22, a band path filter 23, a gain control amplifier 24, a second mixer 25, a band pass filter 26 and a receiving intensity detecting circuit 27. In the receiving intensity detecting circuit 27, received electric field level by RSSI is detected, and an RSSI signal 31 is output to a control unit 18. The control unit 18 detects signal level of the RSSI signal 31, generates a gain control signal 32 corresponding to the received electric field level, and supplies the signal 32 to the gain control amplifier 24. By using the gain control signal 32, gain control of the gain control amplifier 24 is performed. In the time of a strong electric filed wherein received electric field level becomes at least a prescribed value, level of an input signal to the second mixer 25 is restrained, so that saturation is prevented. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless communication device such as a wireless telephone that performs voice communication and data communication.
[0002]
[Prior art]
2. Description of the Related Art In recent years, wireless telephones using wireless communication such as mobile phones and cordless telephones have become widespread, and these wireless telephones have become capable of not only voice communication but also data communication. The transmission quality of a signal is improved to improve the communication quality of voice communication and data communication, and high-speed and large-capacity data transfer is enabled. With the improvement in the performance of wireless communication devices such as wireless telephones, particularly, digital cordless telephones and the like are frequently used at home, so that the reception electric field level frequently occurs.
[0003]
FIG. 3 is a block diagram showing a configuration example of a conventional wireless communication device such as a wireless telephone. This wireless communication device includes a receiving unit 104, a transmitting unit 105, a synthesizer unit 106, and a baseband processing unit 107. The reception signal received by the antenna 101 passes through only a specific frequency band in the band-pass filter 102, and is input to the reception unit 104 via the transmission / reception switch 103. In the receiving unit 104, a received signal in a radio frequency (RF) band is amplified by a low noise amplifier 110, and then mixed with a first local oscillation signal from a first PLL 108 of a synthesizer unit 106 by a first mixer 111 to obtain a first intermediate frequency signal. The frequency is converted to the first IF signal in the (first IF) band. After that, only the specific frequency band is passed through the band-pass filter 112, mixed with the second local oscillation signal from the second PLL 109 of the synthesizer unit 106 by the second mixer 113 and the second IF signal of the second intermediate frequency (second IF) band After the frequency conversion, the bandpass filter 114 passes only a specific frequency band, and the IF amplifier circuit 115 amplifies the second IF signal. Then, the output of the receiving unit 104 is input to the signal processing unit 107, where various signal processing such as demodulation processing to a baseband signal is performed, and received data is generated.
[0004]
In such a wireless communication device, the second mixer 113 of the receiving unit 104 is saturated when the received electric field level is higher than a predetermined value. When such a saturation phenomenon occurs, the input impedance of the second mixer 113 fluctuates, the matching with the band-pass filter 112 at the preceding stage is broken, and the BER (Bit Error Rate) characteristic of the reception characteristic is deteriorated. As a result, the received signal quality may be degraded.
[0005]
As a technique for preventing the deterioration of the transmission quality at the time of a strong electric field, for example, when the electric field strength of a received signal is equal to or more than a specified value, that is, when a strong input signal is received, a transmission / reception changeover switch is set even at the time of reception. There has been proposed a mobile radio device in which input control is performed so as to switch to the circuit side of the above, and a reception system circuit unit corresponding to a wide reception intensity range can be operated under optimum conditions within a linear region (for example, Patent Document 1). 1).
[0006]
[Patent Document 1]
Japanese Patent No. 3198894
[Problems to be solved by the invention]
As described above, in the conventional wireless communication apparatus as shown in FIG. 3, in the case of a strong electric field having a reception electric field level equal to or higher than a predetermined value, the second mixer of the reception section is saturated to cause impedance fluctuation, and There is a problem that characteristics are deteriorated.
[0008]
The prior art described in the above-mentioned Patent Document 1 suppresses an input signal level to a receiving system by obtaining an attenuation amount by an isolation characteristic of a transmission / reception changeover switch in order to prevent deterioration of transmission quality at a strong electric field. It is. However, to prevent the influence due to the impedance fluctuation of the second mixer of the receiving unit, to operate the receiving system under the optimum condition in detail corresponding to a wider receiving intensity range, and to suppress the deterioration of the receiving characteristic, it is necessary to use a transmission / reception switch or the like. It is difficult to realize only by the switching operation of the switch.
[0009]
The present invention has been made to solve the above-described problems, and an object of the present invention is to suppress impedance fluctuations in a mixer circuit of a receiving unit at the time of a strong electric field, suppress deterioration of reception characteristics, and maintain high communication quality. To provide a possible wireless communication device.
[0010]
[Means for Solving the Problems]
A wireless communication device according to the present invention is a wireless communication device including a reception unit including a mixer circuit that performs frequency conversion by mixing a reception signal received by a transmission / reception antenna and an oscillation signal generated by a synthesizer unit. A reception intensity detection unit that detects a reception signal intensity in the reception unit; a signal level adjustment unit that is provided upstream of the mixer circuit and adjusts an input signal level to the mixer circuit; A control unit for controlling a gain in the signal level adjusting unit according to a signal strength.
[0011]
According to the above configuration, by adjusting the input signal level to the mixer circuit by the signal level adjustment unit, for example, the input signal level to the mixer circuit is suppressed at the time of a strong electric field in which the received signal strength is equal to or more than the predetermined value. And the mixer circuit can be prevented from becoming saturated. This makes it possible to suppress impedance fluctuations in the mixer circuit, suppress deterioration of the reception characteristics, and always maintain stable communication quality.
[0012]
The receiving unit may include, as the mixer circuit, a first mixer that converts a received signal in a radio frequency band into a first intermediate frequency band, and a frequency converter that converts the signal in the first intermediate frequency band into a second intermediate frequency band. A second mixer for detecting the reception electric field level as the reception signal strength, wherein the signal level adjustment section is provided in front of the second mixer, When the electric field level is higher than or equal to a predetermined value, the level of the input signal to the second mixer is suppressed.
[0013]
According to the above configuration, the signal level adjuster suppresses the input signal level to the second mixer during a strong electric field in which the received electric field level is equal to or more than the predetermined value, thereby suppressing the fluctuation of the input impedance in the second mixer. It is possible to suppress deterioration of reception characteristics such as BER characteristics and maintain high communication quality.
[0014]
Further, the control unit supplies a gain control signal having a different signal voltage level to the signal level adjustment unit depending on whether the received signal strength is equal to or more than a predetermined value, and controls a gain in the signal level adjustment unit. And
[0015]
According to the above configuration, the control unit supplies a gain control signal having a different signal voltage level to the signal level adjusting unit depending on whether the received signal strength is equal to or greater than a predetermined value. The gain control of the adjustment unit becomes possible, and the input signal level can be adjusted so that the mixer circuit does not become saturated.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a wireless communication device according to an embodiment of the present invention. In the present embodiment, a configuration example when applied to a wireless telephone such as a digital cordless telephone is shown.
[0017]
The wireless communication apparatus according to the present embodiment includes a transmission / reception antenna 11 for transmitting / receiving a radio wave, a bandpass filter 12 for passing a specific frequency band, a transmission / reception switch 13 for appropriately switching between a transmission system and a reception system, a reception unit 14, a transmission unit 15, A synthesizer section 16 for generating an oscillation signal used for frequency conversion in the receiving section 14 and the transmitting section 15; a baseband processing section 17 for performing various signal processing such as baseband signal modulation / demodulation processing; and control for performing signal level control in the receiving section 14 It comprises a part 18.
[0018]
The synthesizer unit 16 includes a first PLL 19 that generates a first local oscillation signal LS1 from the reference signal frequency of the oscillator, and a second PLL 20 that generates a second local oscillation signal LS2 from the reference signal frequency of the oscillator.
[0019]
The receiving unit 14 performs a frequency conversion by mixing a low noise amplifier (LNA) 21 for amplifying a reception signal in a radio frequency (RF) band, an output signal of the low noise amplifier 21 and a first local oscillation signal LS1 from the first PLL 19. A first mixer 22 that generates sum and difference frequencies, and a SAW that obtains a first IF signal in a first intermediate frequency (first IF) band by passing only the sum or difference frequency components from the output of the first mixer 22. (Surface Acoustic Wave: surface acoustic wave) A band-pass filter 23 composed of a filter or the like, and a gain control amplifier 24 functioning as a signal level adjusting unit, the output signal level of which can be controlled by changing the gain by a gain control signal. ing.
[0020]
Further, the receiving unit 14 performs frequency conversion by mixing the output signal of the gain control amplifier 24 and the second local oscillation signal LS2 from the second PLL 20, and generates a sum and difference frequencies, A band-pass filter 26 composed of a ceramic filter or the like that obtains a second IF signal in a second intermediate frequency (second IF) band by passing only the sum or difference frequency components from the output of the two mixers 25, and amplifies the second IF signal. Also provided is a reception intensity detection circuit 27 that functions as a reception intensity detection unit that detects a reception electric field level by an RSSI (Receiver Signal Strength Indicator) and outputs an RSSI signal.
[0021]
The control unit 18 outputs a gain control signal 32 based on the RSSI signal 31 indicating the reception electric field level output from the reception intensity detection circuit 27 and inputs the gain control signal 32 to the gain control amplifier 24, so that the second mixer 25 It is configured to control an input signal level.
[0022]
Next, an operation at the time of reception in the wireless communication device of the present embodiment will be described. The reception signal received by the transmission / reception antenna 11 passes through only a specific frequency band in the band-pass filter 12, and is input to the reception unit 14 via the transmission / reception switch 13. In the receiving unit 14, after the received signal is amplified by the low noise amplifier 21, the received signal is mixed by the first mixer 22 with the first local oscillation signal from the first PLL 19 of the synthesizer unit 16 and frequency-converted into a sum and difference frequency signal. . Then, only the sum or difference frequency band is passed through the band pass filter 23 to extract the first IF signal. Next, after the signal level is controlled by the gain control amplifier 24, the signal is mixed by the second mixer 25 with the second local oscillation signal from the second PLL 20 of the synthesizer unit 16 and frequency-converted into a sum and difference frequency signal. Then, only the sum or difference frequency band is passed through the band-pass filter 26, and the second IF signal is extracted. After that, the second IF signal is amplified by the reception intensity detection circuit 27 and input to the baseband processing unit 17. The baseband processing unit 17 performs various signal processes such as a demodulation process from the second IF signal to a baseband signal, and generates received data.
[0023]
In the reception intensity detection circuit 27, RSSI is detected as a reception electric field level, and an RSSI signal is input to the control unit 18. The control unit 18 generates a gain control signal 32 in accordance with the signal level of the RSSI signal 31, and controls the gain of the gain control amplifier 24 using the gain control signal 32, thereby reducing the input signal level to the second mixer 25. Control.
[0024]
FIG. 2 is a block diagram illustrating a configuration example of the control unit 18 in the wireless communication device according to the present embodiment. The control unit 18 includes an RSSI determination circuit 41 that determines the signal level of the RSSI signal 31, selection switches 42 and 43 that are turned on and off according to the determination result of the RSSI determination circuit 41, and resistance elements R1 and R2 that divide a predetermined voltage Vc. , R3.
[0025]
In the control unit 18 having such a configuration, the RSSI determination circuit 41 determines the signal level of the RSSI signal 31 input from the reception intensity detection circuit 27, and when the reception electric field level is equal to or higher than a predetermined value, for example, 600 dBμV or higher, the control signal A is output to the selection switch 42. On the other hand, when the reception electric field level is lower than the predetermined value, for example, lower than 600 dBμV, the control signal B is output to the selection switch 43. As a result, either the selection switch 42 or 43 is turned on, and the gain control signal 32 having a different signal voltage level according to the received electric field level is supplied to the gain control amplifier 24. It is also possible to output a gain control signal having a signal voltage level of three or more values by increasing the number of selection switches and resistance elements, or to omit the resistance element R3 and to reduce the reception electric field level below a predetermined value. A 0 V gain control signal may be output.
[0026]
The gain control amplifier 24 variably controls the amplification gain of the first IF signal input to the second mixer 25 according to the voltage value of the gain control signal 32. For example, when the received electric field level becomes equal to or higher than a predetermined value, the gain is reduced based on the gain control signal 32 to suppress the signal level of the first IF signal input to the second mixer 25.
[0027]
By the function of the gain control amplifier 24, the input signal level to the second mixer 25 is appropriately adjusted even when the received electric field level is a strong electric field equal to or more than a predetermined value, thereby preventing a saturation state. At this time, the input signal level of the second mixer 25 is adjusted according to the reception electric field level so that the second mixer 25 always operates under the optimum condition in the linear region. As a result, load fluctuations seen from the bandpass filter 23 side are suppressed, and impedance fluctuations of the receiving system at the time of a strong electric field can be suppressed. Therefore, signal quality deterioration such as deterioration of BER characteristics of reception characteristics can be prevented, and received signal quality can be prevented. Can be maintained at or above a predetermined level.
[0028]
It should be noted that the present invention is not limited to the above-described embodiment at all, and can be implemented in various modes without departing from the gist thereof. For example, the configuration of the control unit 18 that controls the gain of the gain control amplifier 24 can be variously modified as long as it can output a gain control signal whose voltage is varied according to the received signal strength.
[0029]
【The invention's effect】
As described above, according to the present invention, in a wireless telephone or the like, it is possible to suppress a variation in impedance in a mixer circuit of a receiving unit at the time of a strong electric field, suppress deterioration of reception characteristics, and maintain high communication quality. Equipment can be provided.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a wireless communication device according to an embodiment of the present invention; FIG. 2 is a block diagram illustrating a configuration example of a control unit in the wireless communication device according to the embodiment; Block diagram showing a configuration example of a wireless communication device such as a wireless communication device.
Reference Signs List 11 transmission / reception antenna 12 band-pass filter 13 transmission / reception changeover switch 14 reception unit 15 transmission unit 16 synthesizer unit 17 baseband processing unit 18 control unit 19 first PLL
20 Second PLL
21 low noise amplifier 22 first mixer 23 band pass filter (SAW filter)
24 Gain control amplifier 25 Second mixer 26 Bandpass filter (ceramic filter)
27 Reception strength detection circuit 41 RSSI judgment circuit 42, 43 selection switch

Claims (3)

A wireless communication device including a reception unit having a mixer circuit that performs frequency conversion by mixing a reception signal received by a transmission / reception antenna and an oscillation signal generated by a synthesizer unit,
A reception strength detection unit that detects a reception signal strength in the reception unit,
A signal level adjusting unit provided at a preceding stage of the mixer circuit and adjusting an input signal level to the mixer circuit;
A control unit that controls a gain in the signal level adjustment unit according to the detected received signal strength,
A wireless communication device comprising: The receiver includes, as the mixer circuit, a first mixer that frequency-converts a received signal in a radio frequency band to a first intermediate frequency band, and a second mixer that frequency-converts the signal in the first intermediate frequency band to a second intermediate frequency band. With two mixers,
The reception strength detection unit detects a reception electric field level as the reception signal strength,
The signal level adjuster is provided in a stage preceding the second mixer, and suppresses an input signal level to the second mixer when a strong electric field in which the reception electric field level is equal to or higher than a predetermined value. The wireless communication device according to claim 1. The control unit supplies a gain control signal having a different signal voltage level to the signal level adjustment unit depending on whether or not the received signal strength is equal to or more than a predetermined value, and controls a gain in the signal level adjustment unit. The wireless communication device according to claim 1.

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