JP2007201708A - Wireless communication circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication circuit capable of lowering a maximum frequency of a local signal generating circuit, narrowing a frequency range to be set, facilitating the design of the local signal generating circuit thereby, and improving the immunity against variations in the characteristics due to a temperature change and the manufacturing yield. <P>SOLUTION: A first stage mixer 7 mixes a local signal whose frequency is divided into 1/4 with a received signal at 2.4 MHz band in the case of reception, second stage mixers (demodulators) 9, 10 mix the local signal whose frequency is halved with the mixed signal, the first stage mixes the local signal without any modification to the received signal at 5 GHz band, and the second stage mixes the local signal whose frequency is halved to the mixed signal. First stage mixers (modulators) 29, 30 mix the local signal whose frequency is halved with a baseband signal for the 2.4 GHz band in the case of transmission, a second stage mixer 31 mixes the local signal whose frequency is divided into 1/4 with the mixed signal, the first stage mixes the local signal whose frequency is halved with the baseband signal for the 5 GHz band, and the second stage mixes the local signal without any modification with the mixed signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a local signal generation circuit that uses two frequency bands for frequency conversion between radio communication signals in two different frequency bands, for example, radio communication signals in the 2.4 GHz band and 5 GHz band and a baseband signal. The present invention relates to a wireless communication circuit that uses a frequency divider, a mixer, and a modulator / modulator.

Wireless local area networks (wireless LANs) are based on IEEE (Institute of Electrical and Electronics Engineers) standards based on 802.11b / g (using 2.4 GHz band) and 802.11a (using 5 GHz band). An 802.11b standard using a 2.4 GHz band having a low frequency band and a low transmission rate has been widespread.
However, since the transmission rate is increased and other interfering radio waves (such as a microwave oven) are not present in the 5 GHz band, 802.11a using the 5 GHz band is also widespread. Also, although 2.4 GHz is used, 802.11g, which can exchange high-speed data at the same transmission rate as 802.11a, has become widespread, and at present, these three standards are divided according to use and location. It is like that. Therefore, a wireless communication circuit corresponding to these three standards (in terms of frequency, two frequency bands of 2.4 GHz and 5 GHz) is required.

Among such wireless communication circuits, a method of modulating / demodulating between a signal in the frequency band of 2.4 GHz band and 5 GHz band and a baseband signal has been reported (for example, see Patent Document 1). This method is shown in FIGS.
In this method, on the 2.4 GHz side shown in (a), a frequency twice the reception signal (4.824 GHz to 4.944 GHz) is generated by a local signal generation circuit (not shown) at the time of reception. The received signal is demodulated into a baseband signal by the mixer 101 using the circumferential signal (2.412 GHz to 2.472 GHz).

At the time of transmission shown in (c), a frequency (4.824 GHz to 4.944 GHz) twice as high as that of the transmission signal is generated by the local signal generation circuit, and the divided signal by 2 (2.412 to 2.472 GHz) is generated. The transmission signal is modulated by the mixer 102 from the baseband signal.
On the 5 GHz side shown in (b), at the time of reception, a 4/5 frequency (4.136 GHz to 4.266 GHz) of the received signal is generated by the local signal generation circuit, and the first mixer 102 performs down-conversion once. Baseband using a signal (1.034 GHz to 1.064 GHz) obtained by dividing the 4/5 frequency of the received signal generated by the local signal generation circuit by 4 in the second stage mixer (demodulator) 104. The signal is demodulated.

At the time of transmission shown in (d), a 4/5 frequency (4.136 GHz to 4.256 GHz) of the transmission signal is generated by the local signal generation circuit, and the baseband signal and the local signal are generated in the first-stage mixer. The signal generated by the generator circuit is up-converted by a signal divided by 4 (1.034 GHz to 1.064 GHz), and this signal is a signal (4/5 frequency of the transmission signal generated by the local signal generator circuit). (4.136 GHz to 4.256 GHz) is modulated by the second-stage mixer 106 and transmitted.
JP 2003-258661 A

  By the way, in the conventional wireless communication circuit, since the frequency conversion as described above is performed, it is necessary to increase the frequency generated by the local signal generation circuit to a maximum of 4.944 GHz, and the minimum frequency is 4.136 GHz. It is necessary to set the range as wide as 808 MHz. Thus, when the frequency generated by the local signal generation circuit is high and the frequency range is wide, the design of the local signal generation circuit becomes difficult, and the resistance to fluctuations in characteristics due to temperature changes is reduced and the manufacturing yield is reduced. There is a problem that decreases.

  The present invention has been made in view of such problems, and can reduce the maximum frequency of the local signal generation circuit and narrow the frequency range to be set, thereby designing the local signal generation circuit. It is an object of the present invention to provide a wireless communication circuit device that can be easily improved and can improve resistance to fluctuations in characteristics due to temperature changes and manufacturing yield.

  To achieve the above object, a radio communication circuit according to claim 1 of the present invention is a radio that performs frequency conversion between a radio communication signal and a baseband signal in two different first and second frequency bands. In the communication circuit, a signal generating means for generating a local signal of a predetermined frequency, and at the time of reception, in the first frequency band, the received signal is mixed with a signal obtained by dividing the local signal by 4 using a first-stage mixer. The mixed signal is mixed with a signal obtained by dividing the local signal by 2 in a second-stage demodulating mixer to form a baseband signal, and in the second frequency band, the received signal is transmitted to the received signal in the first-stage mixer. Receiving means for mixing the local signal as it is, mixing the mixed signal with the signal obtained by dividing the local signal by 2 using a demodulating mixer in the second stage, and converting it to a baseband signal; ,in front In the first frequency band, the baseband signal is mixed with a signal obtained by dividing the local signal by 2 using a first-stage modulation mixer, and the mixed signal is mixed with the local signal by 4 using a second-stage mixer. The frequency-divided signal is mixed into a transmission signal, and in the second frequency band, the baseband signal is mixed with the signal obtained by dividing the local signal by 2 using the first-stage modulation mixer, And a transmission means for performing frequency conversion to mix the local signal with the signal as it is by a second-stage mixer to obtain a transmission signal.

A wireless communication circuit according to claim 2 of the present invention is the wireless communication circuit according to claim 1, wherein the local frequency of the local signal is f _L , the frequency range is Δf _L, and the frequency range of the first frequency band is f _{Bl to} f _{If B2} and the frequency range of the second frequency band is f _{A1 to} f _A2 , the first expression of f _A1 = (3/2) × f _L − (3/4) × Δf _L and f _A2 = (3/2) × f _L + (3/4) × Δf _L second equation, f _B1 = (3/4) × f _L − (3/8) × Δf _L third equation, It is characterized in that the fourth equation of f _B2 = (3/4) × f _L + (3/8) × Δf _L is established.

  According to claim 3 of the present invention, in the wireless communication circuit according to claim 1 or 2, when the first frequency band is 2.4 GHz band and the second frequency band is 5 GHz band, the 2.4 GHz band is used. The band signal has a frequency range of 2.412 GHz to 2.484 GHz, the 5 GHz band has a frequency range of 4.9 GHz to 5.25 GHz, and the local signal has a frequency range of 3.216 to 3.5 GHz. The signal obtained by dividing the local signal by 2 takes a frequency range of 1.608 GHz to 1.75 GHz, and the signal obtained by dividing the local signal by 4 takes a frequency range of 804 MHz to 875 MHz.

According to a fourth aspect of the present invention, there is provided a radio communication circuit according to any one of the first to third aspects, wherein the modulation and demodulation mixers are quadrature modulation / demodulation mixers.
According to a fifth aspect of the present invention, in the wireless communication circuit according to any one of the first to fourth aspects, the first-stage mixer to which the received signal is input is an image rejection mixer. .

According to these configurations, the maximum frequency of the local signal generated by the signal generating means is suppressed to 3.5 GHz, the minimum frequency is 3.216 GHz, and the frequency range can be significantly suppressed to 284 MHz. Therefore, conversion of signals in the two frequency bands of the first frequency band, 2.4 GHz band and the second frequency band, 5 GHz band, to the conventional 4.136 GHz to 4.944 GHz (frequency range 808 MHz). In comparison, in the present invention, the maximum frequency can be reduced to 3.216 GHz to 3.5 GHz (frequency range 284 MHz), and the signal frequency in a narrow range can be generated. As a result, the design of the local signal generation circuit can be facilitated, and the tolerance to the variation in characteristics due to the temperature change and the manufacturing yield can be improved.
In addition, when using an image rejection mixer, the image interference wave component that causes degradation in reception quality during demodulation is removed from the desired wave component and image interference wave component mixed in the IF signal obtained by frequency conversion of the reception signal. Therefore, reception characteristics can be improved.

  As described above, according to the wireless communication circuit of the present invention, the maximum frequency of the local signal generation circuit can be lowered and the frequency range to be set can be narrowed, thereby facilitating the design of the local signal generation circuit. Therefore, there is an effect that it is possible to improve the tolerance to the variation in characteristics due to the temperature change and the manufacturing yield.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a main part of a wireless communication circuit according to an embodiment of the present invention.
The radio communication circuit shown in FIG. 1 is roughly divided into a reception unit RX1, a transmission unit TX1, and a local signal generation unit 38. The reception unit RX1 and the transmission unit TX1 are connected to the switch 17, 22 is connected.

  The receiving unit RX1 includes a 5 GHz band signal receiving terminal 1, a 2.4 GHz band signal receiving terminal 2, a 5 GHz band side low noise amplifier 3, a 2.4 GHz band side low noise amplifier 4, and a 5 GHz band side band pass filter 5. A 2.4 GHz band side band pass filter 6, a reception side mixer 7, a 2.4 GHz band and a 5 GHz band shared band pass filter 8, a reception in-phase signal duplexer 9, and a reception quadrature signal duplexer. The tuner 10, the reception in-phase signal low-pass filter 11, the reception quadrature signal low-pass filter 12, the reception in-phase baseband signal amplifier 13, the reception quadrature baseband signal amplifier 14, and the reception in-phase baseband signal output terminal 15 And a reception quadrature baseband signal output terminal 16.

  The transmission unit TX1 includes a transmission in-phase baseband signal input terminal 23, a transmission quadrature baseband signal input terminal 24, an in-phase baseband signal low-pass filter 25, an orthogonal baseband signal low-pass filter 26, and a transmission in-phase baseband signal. Gain control amplifier 27, transmission quadrature baseband signal gain control amplifier 28, transmission in-phase baseband signal modulator 29, transmission quadrature baseband signal modulator 30, transmission side mixer 31, and transmission 5 GHz signal Band-pass filter 32 for transmission, band-pass filter 33 for 2.4 GHz signal for transmission, high-frequency amplifier 34 for transmission 5 GHz signal, high-frequency amplifier 35 for transmission 2.4 GHz signal, output terminal 36 for transmission 5 GHz, and transmission 2. 4 GHz output terminal 37 is provided.

The local signal generator 38 includes a voltage-controlled oscillator 18a, a frequency divider 18b, a phase comparator 18c, a charge pump 18d, and a loop filter 18e. A circuit 20 and a reference signal input terminal 21 are provided.
In the receiving unit RX1, the input end of the 5 GHz band side low noise amplifier 3 is connected to the 5 GHz band signal receiving terminal 1, and the input end of the 5 GHz band side band pass filter 5 is connected to the output end of the 5 GHz band side low noise amplifier 3. Has been. The output end of the 5 GHz band side band pass filter 5 is connected to the first input end of the reception side mixer 7, and the output end of the reception side mixer is connected to the input end of the reception side shared band pass filter 8.

  The output of the reception-side shared bandpass filter 8 is connected to the input ends of the reception in-phase signal duplexer 9 and the reception quadrature signal duplexer 10, respectively. The output ends of the reception in-phase signal duplexer 9 and the reception quadrature signal duplexer 10 are connected to the input ends of the reception in-phase signal low pass filter 11 and the reception quadrature signal low pass filter 12, respectively. The output ends of the reception in-phase signal low-pass filter 11 and the reception quadrature signal low-pass filter 12 are connected to the input ends of the reception in-phase baseband signal amplifier 13 and the reception quadrature baseband signal amplifier 14, respectively.

Output terminals of the reception in-phase baseband signal amplifier 13 and the reception quadrature baseband signal amplifier 14 are connected to a reception in-phase baseband signal output terminal 15 and a reception quadrature baseband signal output terminal 16, respectively.
In the transmission unit TX1, a transmission in-phase baseband signal input terminal 23 and a transmission quadrature baseband signal input terminal 24 are connected to input terminals of an in-phase baseband signal low-pass filter 25 and an orthogonal baseband signal low-pass filter 26, respectively. . The output terminals of the in-phase baseband signal low-pass filter 25 and the quadrature baseband signal low-pass filter 26 are connected to the input terminals of the transmission in-phase baseband signal gain control amplifier 27 and the transmission quadrature baseband signal gain control amplifier 28, respectively. ing.

  The output terminals of the transmission in-phase baseband signal gain control amplifier 27 and the transmission quadrature baseband signal gain control amplifier 28 are the first inputs of the transmission in-phase baseband signal modulator 29 and the transmission quadrature baseband signal modulator 30, respectively. Connected to the end. The outputs of the transmission in-phase baseband signal modulator 29 and the transmission quadrature baseband signal modulator 30 are connected to the first input terminal of the transmission-side mixer 31, and the output terminal of the transmission-side mixer 3 is the transmission 5 GHz signal band. The pass filter 32 and the transmission 2.4 GHz signal band-pass filter 33 are connected to the input terminals.

  The output ends of the transmission 5 GHz signal band pass filter 32 and the transmission 2.4 GHz signal band pass filter 33 are connected to the input ends of the transmission 5 GHz signal high frequency amplifier 34 and the transmission 2.4 GHz signal high frequency amplifier 35, respectively. Yes. The output ends of the transmission 5 GHz signal high-frequency amplifier 34 and the transmission 2.4 GHz signal high-frequency amplifier 35 are connected to a transmission 5 GHz output terminal 36 and a transmission 2.4 GHz output terminal 37, respectively.

In the local signal generator 38, the reference signal terminal 21 is connected to the reference signal input terminal of the phase locked loop circuit 18, and the voltage controlled oscillator output that is the output terminal of the phase locked loop circuit 18 is connected to the input terminal of the divide-by-4 circuit 19. The input terminal of the divide-by-2 circuit 20, the first input terminal of the switch 17, and the first input terminal of the switch 22 are connected.
The output terminal of the divide-by-4 circuit 19 is connected to the second input terminal of the switch 17 and the second input terminal of the switch 22. The output end of the switch 17 is connected to the second input end of the reception side mixer 7, and the output end of the switch 22 is connected to the second input end of the transmission side mixer 31.

The in-phase signal output terminal of the divide-by-2 circuit 20 is connected to the second input terminal of the receiving common-mode signal duplexer 9 and the second input terminal of the transmission in-phase baseband signal modulator 29, and further divided by two. The quadrature signal output terminal of the circuit 20 is connected to the second input terminal of the reception quadrature signal duplexer 10 and the second input terminal of the transmission quadrature baseband signal modulator 30.
Next, the operation of the wireless communication circuit having such a configuration will be described. First, the operation during reception will be described.

  First, when a 2.4 GHz band signal is received, the received signal passes through the low noise amplifier 4 and the band pass filter 6 from the receiving terminal 2 and is input to the first input terminal of the receiving mixer 7. At this time, the switch 17 is set so that the output of the divide-by-4 circuit 19 is selected. When receiving a 2.4 GHz band signal, the phase-locked loop circuit 18 generates a signal in the frequency range of 3.216 GHz to 3.312 GHz, and accordingly, the divide-by-4 circuit 19 generates a signal in the frequency range of 804 MHz to 828 MHz. The divide-by-2 circuit 20 generates a signal having a frequency range of 1.608 GHz to 1.656 GHz.

  For this reason, the 804 MHz to 828 MHz signal from the divide-by-4 circuit 19 is input to the second input terminal of the reception-side mixer 7. The signal frequency-converted by the reception-side mixer 7 passes through the band-pass filter 8 and is input to the first input terminals of the reception in-phase signal duplexer 9 and the reception quadrature signal duplexer 10. The in-phase signal of 1.608 GHz to 1.656 GHz generated by the divide-by-2 circuit 20 is input to the second input terminal of the reception co-simultaneous signal double tone unit 9, and the second signal of the reception quadrature signal double tone unit 10 is received. An orthogonal signal of 1.608 GHz to 1.656 GHz generated by the divide-by-2 circuit 20 is input to the input terminal.

  A quadrature signal is a signal that is 90 degrees out of phase with the in-phase signal. The signal frequency-converted by the reception common-mode signal duplexer 9 passes through the reception common-mode signal low-pass filter 11, passes through the reception common-mode baseband signal amplifier 13, and is output to the reception common-mode baseband signal output terminal 15. . The signal frequency-converted by the reception quadrature signal duplexer 10 passes through the reception quadrature signal low-pass filter 12, passes through the reception quadrature baseband signal amplifier 14, and is output to the reception quadrature baseband signal output terminal 16.

The frequency of the signal generated by the phase locked loop circuit 18 is set according to the frequency of the received signal. When receiving a 5 GHz band signal, the received signal passes through the low noise amplifier 3 and the band pass filter 5 from the receiving terminal 1 and is input to the first input terminal of the receiving side mixer 7. At this time, the switch 17 is set so that the output of the phase locked loop circuit 18 is selected as it is. When receiving a 5 GHz band signal, the phase-locked loop circuit generates a signal in the frequency range of 3.267 GHz to 3.5 GHz, and accordingly, the divide-by-4 circuit 19 generates a signal in the frequency range of 816.75 MHz to 875 MHz. The divide-by-2 circuit 20 generates a signal having a frequency range of 1.6335 GHz to 1.75 GHz.
For this reason, a signal of 816.75 MHz to 875 MHz from the divide-by-4 circuit 19 is input to the second input terminal of the reception-side mixer 7. The signal frequency-converted by the reception-side mixer 7 passes through the band-pass filter 8 and is input to the first input terminals of the reception in-phase signal duplexer 9 and the reception quadrature signal duplexer 10.

  The in-phase signal of 1.6335 GHz to 1.75 GHz generated by the divide-by-2 circuit 20 is input to the second input terminal of the received common-mode signal double tone unit 9, and the second signal of the received quadrature signal double tone unit 10 is received. An orthogonal signal of 1.6335 GHz to 1.75 GHz generated by the divide-by-2 circuit 20 is input to the input terminal. A quadrature signal is a signal that is 90 degrees out of phase with the in-phase signal. The signal frequency-converted by the reception common-mode signal duplexer 9 passes through the reception common-mode signal low-pass filter 11, passes through the reception common-mode baseband signal amplifier 13, and is output to the reception common-mode baseband signal output terminal 15. . The signal frequency-converted by the reception quadrature signal duplexer 10 passes through the reception quadrature signal low-pass filter 12, passes through the reception quadrature baseband signal amplifier 14, and is output to the reception quadrature baseband signal output terminal 16. The frequency of the signal generated by the local signal generator 38 is set according to the frequency of the received signal.

Next, the operation at the time of transmission will be described.
First, when transmitting a 2.4 GHz band signal, the in-phase signal is input to the transmission in-phase baseband signal input terminal 23 and the quadrature signal is input to the transmission quadrature baseband signal input terminal 24. A quadrature signal is a signal that is 90 degrees out of phase with the in-phase signal. The signal input from the transmission in-phase baseband signal input terminal 23 passes through the in-phase baseband signal low-pass filter 25 and the transmission in-phase baseband signal gain control amplifier 27, and the first input of the transmission in-phase baseband signal modulator 29. Input at the end. The signal input from the transmission quadrature baseband signal input terminal 24 passes through the quadrature baseband signal low-pass filter 26 and the transmission quadrature baseband signal gain control amplifier 28, and passes through the first transmitter quadrature baseband signal modulator 30. Input to the input terminal.

  The in-phase signal output from the divide-by-2 circuit 20 is input to the second input terminal of the transmission in-phase baseband signal modulator 29, and the divide-by-two signal is input to the first input terminal of the transmission quadrature baseband signal modulator 30. An orthogonal signal output from the circuit 20 is input. At the time of 2.4 GHz band signal transmission, the phase-locked loop circuit 18 generates a signal in the frequency range of 3.216 GHz to 3.312 GHz, and accordingly, the divide-by-4 circuit 19 generates a signal in the frequency range of 804 MHz to 828 MHz. The divide-by-2 circuit 20 generates a signal having a frequency range of 1.608 GHz to 1.656 GHz.

The signals subjected to frequency conversion by the transmission in-phase baseband signal modulator 29 and the transmission quadrature baseband signal modulator 30 are added and input to the first input terminal of the transmission-side mixer 31. The output signal of the switch 22 is input to the second input terminal of the transmission-side mixer 31. At this time, the switch 22 is set so that the output of the divide-by-4 circuit 19 is selected.
The signal frequency-converted by the transmission side mixer 31 passes through the transmission 2.4 GHz signal band-pass filter 33 and the transmission 2.4 GHz signal high-frequency amplifier 35 and is output to the transmission 2.4 GHz output terminal 37.

  In 5 GHz band signal transmission, the in-phase signal is input to the transmission in-phase baseband signal input terminal 23, and the quadrature signal is input to the transmission quadrature baseband signal input terminal 24. A quadrature signal is a signal that is 90 degrees out of phase with the in-phase signal. The signal input from the transmission in-phase baseband signal input terminal 23 passes through the in-phase baseband signal low-pass filter 25 and the transmission in-phase baseband signal gain control amplifier 27, and the first input of the transmission in-phase baseband signal modulator 29. Input at the end.

  The signal input from the transmission quadrature baseband signal input terminal 24 passes through the quadrature baseband signal low-pass filter 26 and the transmission quadrature baseband signal gain control amplifier 28, and passes through the second signal of the transmission quadrature baseband signal modulator 30. 1 is input to the input terminal. The in-phase signal output from the divide-by-2 circuit 20 is input to the second input terminal of the transmission in-phase baseband signal modulator 29, and the divide-by-two signal is input to the first input terminal of the transmission quadrature baseband signal modulator 30. An orthogonal signal output from the circuit 20 is input.

  When transmitting a 5 GHz band signal, the phase-locked loop circuit 18 generates a signal having a frequency range of 3.267 GHz to 3.5 GHz, and accordingly, the divide-by-2 circuit 20 has a frequency range of 1.6335 GHz to 1.75 GHz. Generate a signal. The signals subjected to frequency conversion by the transmission in-phase baseband signal modulator 29 and the transmission quadrature baseband signal modulator 30 are added and input to the first input terminal of the transmission-side mixer 31.

The output signal of the switch 22 is input to the second input terminal of the transmission-side mixer 31. At this time, the switch 22 is set so that the output of the phase-locked loop circuit 18 is selected. The signal whose frequency is converted by the transmission-side mixer 31 passes through the transmission 5 GHz signal band-pass filter 32 and the transmission 5 GHz signal high-frequency amplifier 34 and is output to the transmission 5 GHz output terminal 36.
The frequency plan in this embodiment is shown in FIGS. 2A to 2D and will be described.

As shown in FIGS. 2A and 2C, at the time of transmission / reception of a 2.4 GHz band signal, a 2.412 GHz to 2.484 GHz signal is converted into a first-stage mixer 7, a second-stage mixer 9, The baseband signal is generated using a two-stage frequency conversion with 10.
This will be described on behalf of the receiving side in FIG. In this description, reference is also made to the frequency spectrum diagrams of FIGS. 3 (a) and 3 (b). In the first-stage mixer 7, a reception signal having a center frequency f0 at 2.412 GHz to 2.484 GHz is mixed with a first mixing signal having a center frequency of f0 / 3 from 804 MHz to 828 MHz. As a result, the received signal is frequency-converted to a signal having a center frequency of 2f0 / 3 with a frequency of 1.608 GHz to 1.656 GHz.

  The 1.608 GHz to 1.656 GHz signal after the frequency conversion is mixed by the second mixer 9 and 10 with the second mixing signal having a center frequency of 2f0 / 3 at 1.608 GHz to 1.656 GHz. As a result, a baseband signal is generated. However, the first and second mixing signals are signals obtained by dividing the signal generated by the phase-locked loop circuit 18 by 4 and 2, respectively.

Next, as shown in FIGS. 2B and 2D, when transmitting and receiving a 5 GHz band signal, a baseband signal is generated by using a two-stage frequency conversion of a signal of 4.9 GHz to 5.25 GHz. ing.
This will be described on behalf of the receiving side in FIG. In this description, reference is also made to the frequency spectrum diagrams of FIGS. 4 (a) and 4 (b). The mixer 7 at the first stage mixes a received signal having a center frequency of f0 at 4.9 GHz to 5.25 GHz with a first mixing signal having a center frequency of 3.267 MHz to 3.5 MHz and a center frequency of 2f0 / 3. As a result, the received signal is frequency-converted into a signal having a center frequency of f0 / 3 at 1.6335 GHz to 1.75 GHz.

  The 1.6335 GHz to 1 · 75 GHz signal after this frequency conversion is mixed by the second mixer 9 and 10 with the second mixing signal of 1.6335 GHz to 1 · 75 GHz and the center frequency 2f0 / 3. As a result, a baseband signal is generated. However, the first and second mixing signals are signals obtained by dividing the signal generated by the phase-locked loop circuit 18 by 2, respectively.

  As described above, according to the radio communication circuit of the present embodiment, the signal generated by the phase locked loop 18 of the local signal generator 38 in the mixer 7 at the first stage with respect to the 2.4 GHz band signal on the receiving side. The signal divided by 4 by the divide-by-4 circuit 19 is mixed, and the signal generated by the phase-locked loop 18 is divided by 2 in the second stage mixers (duplexer) 9 and 10 with respect to the mixed signal. A baseband signal is obtained by mixing the signals divided by 2 in the circuit 20.

The signal generated by the phase-locked loop 18 is mixed as it is with the first-stage mixer 7 with respect to the 5 GHz band signal on the receiving side, and the second-stage mixer (double tone) 9, 10, the baseband signal is obtained by mixing the signal generated by dividing the signal generated by the phase locked loop 18 by two.
In the 2.4 GHz band signal on the transmitting side, the baseband signal is mixed by the first-stage mixers (modulators) 29 and 30 with the frequency-divided signal generated by the phase-locked loop 18, and this mixed signal A high frequency signal in the 2.4 GHz band is obtained by mixing the signal obtained by dividing the output signal of the phase locked loop 18 by 4 with the mixer 31 in the second stage.

In the 5 GHz band signal on the transmission side, the baseband signal is mixed with the half-divided signal of the output signal of the phase locked loop 18 by the first-stage mixers (modulators) 29 and 30, and the mixed signal is Then, the second-stage mixer 31 mixes the output signal of the phase-locked loop 18 as it is to obtain a high-frequency signal in the 5 GHz band.
By adopting this configuration, the maximum frequency of the signal generated by the local signal generator 38 is suppressed to 3.5 GHz, the minimum frequency is 3.216 GHz, and the frequency range can be significantly suppressed to 284 MHz.

  Therefore, by performing the frequency conversion in this way, the conversion of signals in the two frequency bands of 2.4 GHz band and 5 GHz band was conventionally performed from 4.136 GHz to 4.944 GHz (frequency range 808 MHz). In the form of 3.216 GHz to 3.5 GHz (frequency range 284 MHz), the maximum frequency is low and can be covered by generation of a narrow range of signal frequencies, so the design of the local signal generation circuit can be facilitated, It is possible to improve the tolerance to the variation in characteristics due to the temperature change and the manufacturing yield.

In addition, as a modification of the wireless communication circuit of the above embodiment, a wireless communication circuit shown in FIG. 5 can be used.
That is, in the receiving unit RX2, the performance of reception characteristics can be improved by using the image rejection mixers 7 and 7A described later as the first receiving mixer on the 2.4 GHz band receiving side. . This means that when receiving the 2.4 GHz band, the signal frequency generated by the phase-locked loop circuit 18 is received by the quadrature dividing circuit 18 for the receiving-side mixers 7 and 7A, and two quadrant signals that are 90 degrees out of phase with each other. Because it can be easily generated.

  In addition, since the desired signal component and the image interference wave component are mixed in the signal (IF signal) obtained by frequency-converting the reception signal as described above, if the IF signal is demodulated as it is, reception quality such as reception sensitivity is received. Will deteriorate. For this reason, an image rejection mixer that can remove an image interference wave component from the IF signal is used as a mixer that converts the frequency of the received signal.

On the other hand, the 2.4 GHz band transmission side can be realized by preparing the mixer 31A in the second-stage mixer 31 and further preparing the modulators 29A and 30A in the first-stage modulator in the transmission unit TX2. Can do. At this time, when receiving a signal in the 5 GHz band, the reception-side mixer 7 and the transmission-side mixers 29A, 30A, and 31A are turned off during operation.
Furthermore, in the above description, the embodiment has been described with respect to two bands of 5 GHz band and 2.4 GHz band. However, the band is another two frequency bands satisfying the following relational expressions (1) to (4). For A (frequency range f _{A1 to} f _A2 ) and band B (frequency range f _{Bl to} f _B2 ), implementation can be performed as described below. However, band A corresponds to the 5 GHz band, and band B corresponds to the 2.4 GHz band.

f _A1 = (3/2) × f _L − (3/4) × Δf _L (1)
f _A2 = (3/2) × f _L + (3/4) × Δf _L (2)
f _B1 = (3/4) × f _L − (3/8) × Δf _L (3)
f _B2 = (3/4) × f _L + (3/8) × Δf _L (4)
For example, in FIG. 1, instead of two bands of 5 GHz band and 2.4 GHz band, band A (frequency range f _{A1 to} f _A2 ) and band B (frequency range f _Bl ) satisfying the above formulas (1) to (4) ˜f _B2 ) are received by the receiving unit RX. Further, it is assumed that the phase locked loop circuit 18 of the local signal generator 38 generates a signal having a center frequency f _L and a frequency range Δf _L.

In this case, for band B, the first-stage mixer 7 performs frequency conversion using the signal generated by the phase-locked loop circuit 18 by dividing it by 4 by the divide-by-4 circuit 19, and the second-stage demodulation. The mixers 9 and 10, which are the devices, perform frequency conversion in two stages such as frequency conversion using the signal obtained by frequency-dividing the generated signal by the frequency divider circuit 20.
On the other hand, for band A, the first-stage mixer 7 performs frequency conversion using the generated signal of the phase-locked loop circuit 18, and the second-stage demodulator mixers 9 and 10 convert the generated signal to 2 Frequency conversion is performed in two stages, such as frequency conversion using the frequency-divided circuit 202 signal.

Then, the center frequency f _L and frequency range Δf _{L of the} signal generated by the phase-locked loop circuit 18 at that time, the center frequencies and frequency ranges of the bands A and B (frequency ranges f _{A1 to} f _A2 and frequency ranges f _{Bl to} f _B2). ) So as to satisfy the relationships of the above formulas (1) to (4). The transmitter TX is the same as the receiver RX except that the demodulation process is a modulation process.

  The present invention is suitable for a wireless communication circuit, particularly a circuit for a wireless local area network.

It is a block diagram which shows the structure of the principal part of the radio | wireless communication circuit which concerns on embodiment of this invention. It is a figure for demonstrating the frequency conversion of the transmission-and-reception signal of 2.4 GHz band and 5 GHz band in the radio | wireless communication circuit which concerns on the said embodiment. It is a frequency spectrum figure at the time of frequency conversion in a 2.4 GHz band. It is a frequency spectrum figure at the time of frequency conversion in a 5 GHz band. It is a block diagram which shows the structure of the principal part of the radio | wireless communication circuit by the modification of the radio | wireless communication circuit which concerns on the said embodiment. It is a figure for demonstrating the frequency conversion of the transmission-and-reception signal of 2.4 GHz band and 5 GHz band in the conventional radio | wireless communication circuit.

Explanation of symbols

1 5 GHz band signal receiving terminal 2 2.4 GHz band signal receiving terminal 3 5 GHz band side low noise amplifier 4 2.4 GHz band side low noise amplifier 5 5 GHz band side band pass filter 6 2.4 GHz band side band pass filter 7 Reception side mixer 8 2.4 GHz band and 5 GHz band shared bandpass filter 9 Received in-phase signal duplexer 10 Received quadrature signal duplexer 11 Received inphase signal lowpass filter 12 Received orthogonal signal lowpass filter 13 Received inphase baseband signal Amplifier 14 Reception Quadrature Baseband Signal Amplifier 15 Reception In-phase Baseband Signal Output Terminal 16 Reception Quadrature Baseband Signal Output Terminal 17, 22 Switch 18 Phase Locked Loop Circuit 18a Voltage Control Oscillator 18b Frequency Divider 18c Phase Comparator 18d Charge Pump 18e Loop Filter 19 4 minutes Circuit 20 Divider circuit 21 Reference signal input terminal 23 Transmission in-phase baseband signal input terminal 24 Transmission quadrature baseband signal input terminal 25 Low-pass filter for in-phase baseband signal 26 Low-pass filter for quadrature baseband signal 27 For transmission in-phase baseband signal Gain control amplifier 28 Gain control amplifier for transmitting quadrature baseband signal 29 Transmitter in-phase baseband signal modulator 30 Transmitter quadrature baseband signal modulator 31 Transmitter mixer 32 Bandpass filter for transmitting 5 GHz signal 33 Transmitting for 2.4 GHz signal Bandpass filter 34 High-frequency amplifier for transmission 5 GHz signal 35 High-frequency amplifier for transmission 2.4 GHz signal 36 Output terminal for transmission 5 GHz 37 Output terminal for 2.4 GHz transmission 38 Local signal generator RX1, RX2 Receiver TX1, TX2 Shin part

Claims (5)

In a radio communication circuit that performs frequency conversion between a radio communication signal and a baseband signal in two different first and second frequency bands,
Signal generating means for generating a local signal of a predetermined frequency;
At the time of reception, in the first frequency band, the received signal is mixed with a signal obtained by dividing the local signal by 4 by a first-stage mixer, and the mixed signal is mixed with the local signal by a second-stage demodulation mixer. Is mixed into a baseband signal, and in the second frequency band, the received signal is mixed with the local signal as it is by the first-stage mixer, and the second-stage signal is mixed with the mixed signal. Receiving means for performing frequency conversion by mixing a signal obtained by dividing the local signal by 2 with a demodulating mixer into a baseband signal;
At the time of transmission, in the first frequency band, the baseband signal is mixed with a signal obtained by dividing the local signal by 2 using a first-stage modulation mixer, and the mixed signal is mixed with the second-stage mixer. A signal obtained by dividing a local signal by 4 is mixed to obtain a transmission signal. In the second frequency band, a baseband signal is mixed with a signal obtained by dividing the local signal by 2 using a first-stage modulation mixer, A radio communication circuit, comprising: a transmission means for performing frequency conversion by mixing the local signal with the mixed signal as it is by a second-stage mixer to obtain a transmission signal. Wherein the center frequency of the local signal frequency range in f _L and Delta] f _L, the frequency range of the first frequency band and f _Bl ~f _B2, the frequency range of the second frequency band and f _A1 ~f _A2 if you did this,
The first equation of f _A1 = (3/2) × f _L − (3/4) × Δf _L ,
a second equation of f _A2 = (3/2) × f _L + (3/4) × Δf _L ;
a third expression of f _B1 = (3/4) × f _L − (3/8) × Δf _L ;
The wireless communication circuit according to claim 1, wherein f _B2 = (3/4) × f _L + (3/8) × Δf _L is satisfied.   When the first frequency band is 2.4 GHz band and the second frequency band is 5 GHz band, the 2.4 GHz band signal ranges from 2.412 GHz to 2.484 GHz, and the 5 GHz band is The frequency range of 4.9 GHz to 5.25 GHz is taken, the local signal takes the frequency range of 3.216 to 3.5 GHz, and the signal obtained by dividing the local signal by 2 is 1.608 GHz to 1.75 GHz. The radio communication circuit according to claim 1 or 2, wherein a frequency range is taken and the signal obtained by dividing the local signal by 4 has a frequency range of 804 MHz to 875 MHz.   4. The wireless communication circuit according to claim 1, wherein the modulation and demodulation mixers are quadrature modulation / demodulation mixers.   The wireless communication circuit according to claim 1, wherein the first-stage mixer to which the received signal is input is an image rejection mixer.

Images