JP2007258944A - Radio communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system with a signal measurement circuit for carrying out reception operation control and band use state discrimination. <P>SOLUTION: The radio communication system includes the signal measurement circuit for detecting the strength of received first and second signals with a first band or a second band narrower than the first band. At an initial setting including time of power application, a first selection circuit selects the first signal with the first band or below, and a second selection circuit selects the second signal with the second band or below. When no first and second signals exist, a first mode is selected wherein the signal is transmitted/received with the first band or below. When the first signal exists and no second signal exists, a second mode is selected wherein the signal is transmitted/received with the second band or below. When both the first and second signals exist, a third mode is selected wherein the signal transmission/reception is stopped. In the signal transmission/reception, the strength of the first and second signals is detected corresponding to the first or second mode to form a gain control signal of first and second variable gain amplifier circuits. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication system, particularly to a wireless LAN, and relates to a technique that is effective when used for a device having a function of confirming that another system does not use the same band before transmission.

In order to quickly detect adjacent channel signal interference in the superheterodyne receiver, an IF filter corresponding to each of the desired channel and its lower adjacent channel and upper adjacent channel is provided, and an electric field strength detector is provided for each, Japanese Patent Application Laid-Open No. 9-27759 proposes a technique for simultaneously and independently determining the degree of interference between a lower adjacent channel signal and an upper channel signal with respect to a desired channel signal. Further, the received signal levels in a plurality of different frequency bands are detected by the two electric field strength detection means, and the filter control signal formed by the baseband filter control means according to the presence or absence of the adjacent wave is changed to the I low-pass filter and the Q Japanese Patent Laid-Open No. 2000-49875 proposes a low-pass filter that can be switched and controlled by switching to a low-pass filter.
Japanese Patent Laid-Open No. 9-27759 JP 2000-49875 A

  For example, in a 5 GHz wireless LAN, in order to share a frequency with another system such as a radar, it is obliged to confirm that the other system does not use the same band before transmission. In Bluetooth, the frequency is scanned in advance to check the usage status. When this is applied to the 5 GHz wireless LAN described above, it is necessary to pull in the PLL by matching the frequency synthesizer to each channel, and in particular, the PLL pull-in time loss reduces the communication efficiency. Therefore, if an IF filter is provided in accordance with each band as in Patent Document 1 and the determination is made independently at the same time, the circuit scale becomes large.

  An object of the present invention is to provide a wireless communication system including a signal measurement circuit that performs reception operation control and band usage status determination. The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  The outline of a typical invention among the inventions disclosed in the present application will be briefly described as follows. The high frequency first signal and the second signal in the first band or narrower second band received by the antenna are amplified by the high frequency amplifier circuit, down-converted by the frequency conversion circuit, and the first variable gain amplifier circuit and second Amplification is performed by a variable gain amplifier circuit. The intensity of the first signal and the second signal is detected by a signal measurement circuit. In the initial setting including when the power is turned on, the signal measurement circuit selects the first signal below the first band in the first selection circuit, and selects the second signal below the second band in the second selection circuit. When the first and second signals do not exist, the first mode in which signal transmission / reception operation is performed in the first band or less is set, the first signal exists, and the second signal does not exist in the second band or less. In some cases, a second mode in which a signal transmission / reception operation in the second band or lower is performed, and a third mode in which the signal transmission / reception operation is stopped when the first and second signals are present. During the signal transmission / reception operation, the first and second signal intensities are detected corresponding to the first or second mode to form gain control signals for the first and second variable gain amplifier circuits.

  The signal measuring circuit can be shared for batch determination of band usage status determination and strength determination in reception operation.

  FIG. 1 shows a block diagram of an embodiment of a wireless LAN RF processing unit (high frequency IC) and baseband processing unit (baseband LSI) suitable for application of the present invention. In the figure, components other than the RF processing unit 41 and the baseband processing unit 42 are omitted. In an actual wireless LAN, the transmission amplifier 40 is configured as a module (power module) on an insulating substrate such as a ceramic substrate together with an impedance matching circuit and a filter for removing harmonics. Although not particularly limited, the circuit for forming the high frequency IC (41) is formed on one semiconductor substrate such as SiGe, and the baseband LSI (42) is a circuit using CMOS on one semiconductor substrate such as silicon. It is formed.

  With the above configuration, the RF processing unit 41 can easily obtain an operation speed for performing up-conversion and down-conversion operations, and the baseband processing unit 42 can operate with low power consumption. In addition, a bandpass filter that removes unnecessary waves from the received signal is provided between the antenna 1 and the RF processing unit 41. In the case where two antennas are provided via a switch, a bandpass filter is provided between the switch and the RF processing unit 41. This band-pass filter is not a narrow band filter such as a SAW filter, but may be a filter having a bandwidth such as 5 GHz composed of a capacitive element and an inductor element. The bandpass filter is configured as a module (front end module) on an insulating substrate separate from the power module. These modules, the RF processing unit (high frequency IC) 41, and the baseband processing unit (baseband LSI) 42 are mounted on one printed wiring board to constitute a wireless LAN.

  The transmission / reception operation in the wireless LAN of this embodiment is as follows. The received signal is received from the receiving antenna 1, amplified by an LNA (low noise amplifier) 4, and converted into a baseband signal by the mixers 7a and 7b. After that, the LPF / PGA 11a, 11b removes the interference signal and amplifies the target signal to an appropriate level, and transmits the I, / I (22), Q, / Q (23) signals separately to the baseband processing unit. Then, the signal is demodulated by a demodulation circuit 39 via ADCs (analog / digital conversion circuits) 50a and 50b. A baseband signal is generated from the modulation circuit 33 by the modulation circuit 33, passes through the transmission baseband LPFs 31a and 31b via DACs (digital / analog conversion circuits) 51a and 51b, and is frequency-converted to the target RF frequency by the transmission mixer 30. Then, it is amplified by the transmission amplifier 40 and transmitted from the transmission antenna 28.

  The reception level adjustment operation during the reception operation is as follows. An AGC (Automatic Gain Control 1) is used as a mechanism for adjusting the level of the receiving side I and Q baseband signals. A signal measurement circuit (RSSI) 12 is used for signal level measurement for this purpose. The RSSI 12 outputs the outputs 26 and 27 of the mixers 7a and 7b after removing interference signals, performing logarithmic compression of the detection and signal level values. The signal measurement circuit 12 is used to determine the band usage status.

  The output of the signal measurement circuit (RSSI) 12 is analog / digital converted by the ADC 49 and sent to the control circuit 14. The control circuit generates the gain setting value time division data 18 based on the result at the time of the reception operation, and the LPF / PGA 11a, 11b of the LPF / PGA 11a, 11b through the gain control circuit 24 so that the I and Q signal levels become the target level. Control the gain. Thus, gain adjustment is performed so that the input level to the ADCs 50a and 50b of the baseband processing unit 42 is optimized during the reception operation. Further, at the time of initial setting including when the power is turned on, the gain control circuit 24 determines the data 18 received from the control circuit 14 as a mode control signal, and sets the reception mode to wide band or narrow band or reception stop.

  FIG. 2 is a block diagram showing an embodiment of the signal measuring circuit according to the present invention. The signal measurement circuit 12 of this embodiment includes the following circuit blocks. The reception signal 26 down-converted by the mixer 7a of FIG. 1 is input to the I-side low-pass filter (hereinafter referred to as I-LPF) 100. Here, the adjacent signal or non-adjacent signal is removed from the received signal, and the target signal I is extracted. The reception signal 27 down-converted by the mixer 7b in FIG. 1 is input to the Q-side low-pass filter (hereinafter referred to as Q-LPF) 101. Here, the adjacent signal or non-adjacent signal is removed from the received signal, and the target signal Q is extracted. The extracted target signals I and Q are amplified and detected by the I detection circuit 102 and the Q detection circuit 103, respectively.

  The detection output 110 of the I detection circuit 102 and the detection output 111 of the Q detection circuit 103 are added by the analog adder circuit 104 to obtain a detection signal 113 of the reception level during the reception operation. Further, the two signals of the detection output 110 and the detection output 111 are input to a determination circuit 105 for determining whether there is a signal in another system at the time of initial setting including when the power is turned on. The determination circuit 105 includes a decoder DEC that determines one of the three modes from the combination of the two signals 110 and 111, and an encoder ENC that converts the determination result into a ternary signal 112. The output signal of the adder circuit 104 and the output signal 112 of the determination circuit 105 are selectively transmitted as an output signal OUT by a signal selection circuit 106 such as a multiplexer (MPX).

  The signal determination circuit 12 is controlled by a control signal 21 formed by the control circuit 24. Of the control signal 21, the signals 107 and 108 set the I-LPF 100 and the Q-LPF 101 to the same cut-off frequency f1 or f2 corresponding to the set channel during the reception operation. Of the control signal 21, the signals 107 and 108 are set so that the cut-off frequencies are different for the two channels at the initial setting including when the power is turned on. For example, the signal 107 sets the I-LPF 100 to a cut-off frequency f1 corresponding to band 1 described later, and the signal 108 sets the Q-LPF 101 to a cut-off frequency f2 corresponding to band 2 described later. Of the control signals 21, the signal 109 controls the signal selection circuit 106, selects the output signal 113 of the addition circuit 104 during a reception operation, and outputs the output signal 112 of the determination circuit 105 during initial setting including when the power is turned on. Select.

  FIG. 3 shows a circuit diagram of one embodiment of the determination circuit 105 of FIG. 4 to 6 are characteristic diagrams for explaining the operation. The detection output 110 is supplied to one input terminal (+) of the voltage comparison circuit 200. The determination level 205 is supplied to the other input terminal (−) of the voltage comparison circuit 200. The detection output 111 is supplied to one input terminal (+) of the voltage comparison circuit 201. The determination level 205 is supplied to the other input terminal (−) of the voltage comparison circuit 201. The determination level 205 is a predetermined level for determining whether or not the detection outputs 110 and 111 are present. Three modes are determined by a combination of the output signals of the voltage comparison circuits 100 and 101.

  That is, the first mode is when the output signals of the voltage comparison circuits 200 and 201 are both at the low level because there is no signal generated by the other system in the band 1 and the band 2 as shown in the characteristic diagram of FIG. In the second mode, as shown in the characteristic diagram of FIG. 5, there is a signal generated by another system in the band 1, there is no signal in the band 2, and the output signal of the voltage comparison circuit 200 is at a high level. This is when the output signal 201 is at a low level. The third mode is when there is a signal generated by another system in band 2 as shown in FIG. 6, and the output signals of the voltage comparison circuits 200 and 201 are both at a high level. At this time, since the I-LPF 100 passes the signal of the band 2, the output signal of the voltage comparison circuit 200 is also at a high level. Therefore, there is no mode in which the output signal of the voltage comparison circuit 200 is low and the output signal of the voltage comparison circuit 201 is high.

  The adder circuit 204 performs an analog addition operation of adding the output signals of the voltage comparison circuits 200 and 201. The adder circuit 204 forms a low level + low level in the first mode, forms a high level + low level in the second mode, and forms a high level + high level 2 in the third mode. Form a double high level. That is, when the low level is 0V and the high level is 1V, the adder circuit 204 generates a ternary signal 112 of 0V in the first mode, 1V in the second mode, and 2V in the second mode.

  7 to 10 are explanatory diagrams of the operation of the wireless LAN according to the present invention. FIG. 7 shows a WLAN channel arrangement. FIG. 8 shows a band setting example of the RSSI filter (I-LPF, Q-LPF in FIG. 2). By selecting band 1 and band 2 as shown in the figure, the usage status of the own channel and the adjacent channel can be monitored by the output of the encoder ENC in FIG. When the output level of the encoder ENC is 1V, since one of the adjacent channels is in use, communication using only the own channel is performed as shown in FIG. When the output of the encoder ENC is 0V, both adjacent channels are free, so communication is performed with a bandwidth twice as large as the normal channel bandwidth as shown in FIG. By performing such broadband communication, the amount of communication data per hour can be increased.

  For example, when the adjacent channel usage state is detected using RSSI as in the case of Bluetooth, in the case of the channel arrangement as shown in FIG. 7, a total of three RF frequencies for each of the self channel and the adjacent channel are used. Setting is required and it takes time to pull in the PLL each time. However, the RSSI I-LPF and Q-LPQ frequencies can be determined by one detection only by making the frequencies f1 corresponding to the band 1 and f2 corresponding to the band 2 different. Further, since it is not necessary to re-draw the PLL, it is possible to shift to the communication operation without taking time from the detection of the usage state. As described above, by using the band 1 and the band 2 for the actual communication bands such as the adjacent channel and the self channel, it is possible to detect the use status of the self channel and the adjacent channel at a time. The subsequent communication bandwidth can be selected in a short time.

  In this embodiment, a large part of the circuit scale, such as an LPF or a detection circuit that determines the usage status of the adjacent channel, uses the function already possessed as the RSSI 12 for the reception operation as it is. The increase is limited to an increase in a small circuit as shown in FIG.

  The control circuit 14 in FIG. 1 outputs a processor for executing a program, a program memory for storing a program, a data memory for temporarily storing a program execution result, an input port for receiving an output from the RSSI 12, and a signal for controlling the outside Output ports, and a bus that connects each of those modules. The control circuit 14 controls the operation of the entire system such as reception system gain control and transmission system circuit adjustment including control at the time of initial setting including power-on using the RSSI 12 as described above.

  FIG. 11 is a flowchart for explaining an embodiment of the operation at the time of initial setting including the time of turning on the power. Such operation control is performed by the following steps (1) to (12) according to a program stored in the program memory.

In step (1), the I-side LPF is set to band 1 (wide band), and the Q-side LPF is set to band 2 (narrow band).
In step (2), a timer for a signal detection period is started.
In step (3), H (high level) of the I-side comparator output is determined.
In step (4), the broadband detection flag is set to 1 if it is determined as H in step (3).
In step (5), if it is determined to be L in step (3), H (high level) of the Q-side comparator output is determined.
In step (6), if it is determined H in step (5), the narrow band detection flag is set to 1.
In step (7), it is determined as L in step (5) above, or when step (6) is completed, it is determined whether the signal detection timer is ended (END). When the signal detection timer does not expire, the process returns to step (3).
In step (8), it is determined whether the narrowband signal detection flag is 1.
In step (9), when the narrowband signal detection flag is 0, it is determined whether or not the wideband signal detection flag is 1.
In step (10), when the narrowband signal detection flag is 1 in step (8), communication on the channel is stopped.
In step (11), communication is started in a narrow band when the wideband signal detection flag is 1 in step (9).
In step (12), when the broadband signal detection flag is 0 in step (9), communication is started in a wide band.

  FIG. 12 is a block diagram showing another embodiment of the signal measuring circuit according to the present invention. The signal measurement circuit 12 of this embodiment is directed to the case where there are more N channels of two or more systems. By setting individual cut-off frequencies for the LPFs provided corresponding to these channels, the channel usage status can be determined in a lump for the N channels as well.

  Although the invention made by the inventor has been specifically described based on the above embodiment, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the invention. For example, the I-LPF, Q-LPF, and N-LPF provided in the signal determination circuit 12 can be replaced with a band-pass filter (BPF) in addition to the low-pass filter as described above. The channel usage status is detected in the short time as described above, so that the channel can be used efficiently by detecting at the start of transmission / reception operation in a wireless LAN, for example, when the power is turned on. Also good. The present invention can be widely used in wireless communication systems.

FIG. 3 is a block diagram showing an embodiment of a wireless LAN RF processing unit and baseband processing unit suitable for applying the present invention. It is a block diagram which shows one Example of the signal measurement circuit based on this invention. FIG. 3 is a circuit diagram illustrating an example of a determination circuit 105 in FIG. 2. FIG. 3 is a characteristic diagram for explaining the operation of the signal measurement circuit of FIG. 2. FIG. 3 is a characteristic diagram for explaining the operation of the signal measurement circuit of FIG. 2. FIG. 3 is a characteristic diagram for explaining the operation of the signal measurement circuit of FIG. 2. It is explanatory drawing of operation | movement of the wireless LAN which concerns on this invention. It is explanatory drawing of operation | movement of the wireless LAN which concerns on this invention. It is explanatory drawing of operation | movement of the wireless LAN which concerns on this invention. It is explanatory drawing of operation | movement of the wireless LAN which concerns on this invention. It is a flowchart for demonstrating operation | movement of one Example at the time of the initial setting including the time of power activation of the signal measurement circuit which concerns on this invention. It is a block diagram which shows another Example of the signal measurement circuit based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reception antenna, 4 ... LNA, 7a, 7b ... Mixer, 11a, 11b ... LPF / PGA, 12 ... Signal measurement circuit, 14 ... Control circuit, 17 ... PGA gain setting value data, 18 ... Gain setting value time division data & Clock, 20 ... Gain control signal, 22 ... I, / I signal, 23 ... Q, / Q signal, 28 ... Transmission antenna, 30 ... Transmission mixer, 39 ... Demodulation circuit, 40 ... Transmission amplifier, 41 ... RF processing section 42 ... baseband processing unit, 49, 50a, 50b ... ADC, 51a, 51b ... DAC,
DESCRIPTION OF SYMBOLS 100 ... I-LPF, 101 ... Q-LPF, 102 ... I detection circuit, 103 ... Q detection circuit, 104, 204 ... Adder circuit, 105 ... Determination circuit, 106 ... Signal selection circuit, 200, 201 ... Voltage comparison circuit

Claims (7)

A high-frequency amplifier circuit that amplifies the first and second high-frequency signals in the first band or narrower second band received by the antenna;
A frequency conversion circuit for down-converting each of the high-frequency first signal and the second signal amplified by the high-frequency amplifier circuit;
A first variable gain amplifying circuit and a second variable gain amplifying circuit for amplifying the first signal and the second signal output by down-conversion by the frequency conversion circuit, respectively;
A signal measurement circuit for detecting the intensity of the received first signal and second signal,
The signal measurement circuit is
During initial settings including when the power is turned on,
Selecting the first signal below the first band using a first selection circuit;
Selecting the second signal below the second band using a second selection circuit;
A first mode for performing signal transmission and reception operations in the first band and below when the first signal is not detected and does not exist in the first band and below and no second signal is detected in the second band and below. Set,
Setting a second mode for performing signal transmission and reception operations below the second band when the first signal is detected below the first band and no second signal is detected below the second band; Setting a third mode for stopping signal transmission and reception operations below the second band when the first signal is detected below the first band and the second signal is detected below the second band; During signal transmission and reception operations,
Wireless communication for selecting a first signal and a second signal corresponding to the set first or second mode, detecting the strength thereof, and forming a gain control signal for the first and second variable gain amplifier circuits system. In claim 1,
The wireless communication system, wherein the first signal is an I signal and the second signal is a Q signal. In claim 2,
The wireless communication system, wherein the first selection circuit and the second selection circuit include a variable filter that allows the signal in the first band or the second band to pass according to a control signal. In claim 3,
The first selection circuit is a first variable low-pass filter that receives an I signal,
The second selection circuit is a second variable low-pass filter that receives a Q signal,
A first detection circuit for receiving an output signal of the first variable low-pass filter;
A second detection circuit for receiving an output signal of the second variable low-pass filter;
An addition circuit for adding the output signals of the first detection circuit and the second detection circuit;
A determination circuit which receives the output signal of the first detection circuit and the output signal of the second detection circuit and forms a detection signal corresponding to the first mode to the third mode;
A radio communication system further comprising a signal selection circuit that selects and outputs an output signal of the addition circuit or the determination circuit. In claim 4,
The determination circuit is
A first voltage comparison circuit for receiving an output signal of the first detection circuit and a determination level;
A second voltage comparison circuit receiving the output signal of the second detection circuit and the determination level;
A wireless communication system comprising: an analog adder circuit that adds the output voltage of the first voltage comparison circuit and the output voltage of the second voltage comparison circuit to form a multilevel signal. In claim 5,
A radio communication system in which signal transmission and reception operations in the first mode have a wider bandwidth than signal transmission and reception operations in the second mode. In claim 1,
The wireless communication system is a wireless LAN system, and the wireless LAN system is formed on one semiconductor substrate.

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