WO2012133516A1 - 受信回路およびそのフィルタリング方法 - Google Patents
受信回路およびそのフィルタリング方法 Download PDFInfo
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- WO2012133516A1 WO2012133516A1 PCT/JP2012/058106 JP2012058106W WO2012133516A1 WO 2012133516 A1 WO2012133516 A1 WO 2012133516A1 JP 2012058106 W JP2012058106 W JP 2012058106W WO 2012133516 A1 WO2012133516 A1 WO 2012133516A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/10—Frequency-modulated carrier systems, i.e. using frequency-shift keying
- H04L27/14—Demodulator circuits; Receiver circuits
- H04L27/144—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements
- H04L27/148—Demodulator circuits; Receiver circuits with demodulation using spectral properties of the received signal, e.g. by using frequency selective- or frequency sensitive elements using filters, including PLL-type filters
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
- H04B1/26—Circuits for superheterodyne receivers
- H04B1/28—Circuits for superheterodyne receivers the receiver comprising at least one semiconductor device having three or more electrodes
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- the present invention is based on the priority claim of Japanese Patent Application No. 2011-069489 (filed on Mar. 28, 2011), the entire contents of the same application are incorporated and described herein by reference. It shall be.
- the present invention relates to a receiving circuit and a filtering method, and more particularly to a receiving circuit corresponding to a plurality of wireless standards and a filtering method thereof.
- wireless integrated circuits such as digital terrestrial television broadcasting and wireless local area networks (LANs) are mounted on portable terminals.
- the carrier frequency of terrestrial digital television broadcasting is 862 MHz or less
- the signal bandwidth is 8 MHz
- the carrier frequency of wireless LAN is 5 GHz or less
- the signal bandwidth is 40 MHz or less
- most major wireless standards are 5 GHz or less of carrier frequency
- the bandwidth is 100 MHz or less.
- Non-Patent Documents 1 and 2 a wireless standard having a carrier frequency of 5 GHz or less and a signal bandwidth of 100 MHz or less
- compliance with a plurality of standards is in progress (for example, Non-Patent Documents 1 and 2).
- a communication standard using ultra-wide band such as UWB or millimeter wave
- the frequency of a signal to be handled is high, and it is difficult to cope with a general-purpose circuit. Therefore, as shown in FIG. 11, a plurality of signal processing systems are juxtaposed as shown in FIG. 11 in order to realize a reception IC that can meet the wireless standard using ultra-wide band such as UWB in addition to digital terrestrial television broadcasting and wireless LAN. Configuration is realistic.
- the receiving apparatus of FIG. 11 is configured of a first receiving system 110a that handles a specific ultra-wideband wireless standard and a second receiving system 110b that handles major wireless standards such as a wireless LAN.
- the first reception system 110a is, for example, a reception system dedicated to UWB, and a band used in UWB is selected in advance by a band selection filter outside the IC.
- the second receiving system 110b is a general-purpose receiving system capable of supporting a wireless standard having, for example, a carrier frequency of 5 GHz or less and a signal bandwidth of 100 MHz or less, and the band of 5 GHz or less is outside the IC in advance. Is selected by the band selection filter of
- a radio frequency (RF) signal is input to a low noise amplifier (LNA) 103a in the IC via the antenna 101a and the band selection filter 102a.
- LNA low noise amplifier
- orthogonal demodulation is performed simultaneously with frequency conversion to the baseband (Baseband: BB), and channel selection filters 105a and 105b and variable gain amplifiers (VGA) 106a and 106b are further added.
- Signal processing such as filtering and amplitude adjustment is performed. Thereafter, they are converted into digital signals by analog-to-digital converters (ADCs) 107a and 107b, respectively, and various digital processes are performed by the digital baseband unit 109.
- ADCs analog-to-digital converters
- the second reception system 110b is different from the first reception system 110a in that the RF filter 108 is inserted at the rear stage of the LNA 103b.
- the first reception system 110a for example, jamming signals outside the band used for UWB are eliminated in advance, while in the second reception system 110b, various carrier frequencies of 5 GHz or less are used. It is due to the signal being input. That is, in order to avoid interference in the circuit in the subsequent stage, an RF filter 108 that passes only the signal of the desired carrier frequency is required.
- Patent Document 1 discloses an intermediate frequency generation method of a wireless unit in a TDMA communication method or a TDD communication method.
- a first mixer with a first station frequency signal is provided on one side of a common band pass filter for transmission and reception, and a second mixer with a second station frequency signal is provided on the other side.
- said 3rd mixer While providing, while providing the 3rd mixer by 2nd station origin frequency signal in the other side of said common band pass filter, providing the 4th mixer with 1st station origin frequency signal in 1 side, said 3rd mixer Is configured to mix the same frequency signal as the second local oscillation frequency signal and the second intermediate frequency signal, and the transmission signal is transmitted to the first intermediate frequency between the common band pass filter and the fourth mixer.
- a quadrature modulator that modulates by a signal is inserted.
- the conventional receiving apparatus has a problem that the area of the circuit is increased, which leads to an increase in cost. That is, in the reception circuit integrated in the IC, a total of three types of channel selection filters 105a and 105b of the first reception system, an RF filter 108 of the second reception system, and channel selection filters 105c and 105d are included. is necessary.
- the filter circuit uses a large number of passive elements such as capacitances, resulting in a large area. The area is not negligible with respect to the area of the entire receiving apparatus.
- An object of the present invention is to provide a small-area receiving circuit and its filtering method.
- a receiver circuit converts a first signal of a first frequency input from the outside into a frequency and outputs the first signal, and the first mixer outputs the first signal.
- a first selector for selecting either a signal or a second signal of a second frequency input from the outside, and a filter for removing a predetermined frequency band of the signal selected by the first selector
- a second selector for selecting an output to the outside or an output to a circuit at a later stage of the signal whose frequency band has been removed, and frequency-converting and outputting the signal output by the second selector.
- a second mixer which is a circuit of the latter stage, the second frequency being equal to the carrier frequency of the radio signal.
- a receiver circuit includes: a first mixer for frequency-converting and outputting a first component of a first signal of a first frequency input from the outside; Either a second mixer that frequency-converts and outputs a second component of the signal, or a first component of the frequency-converted first signal, or a second signal of a second frequency externally input
- a first selector for selecting one of the two, a second selector for selecting one of the second component of the first signal subjected to frequency conversion, and the second signal, and the first selector
- a first filter for removing the first frequency band of the signal selected by the second filter, a second filter for removing the second frequency band of the signal selected by the second selector, and the first frequency band Output of the signal from which the An output by the third selector to be selected, a fourth selector to select the output of the signal from which the second frequency band has been removed, to the outside or to the circuit of the subsequent stage, and the third selector
- a third mixer and a fourth mixer which are circuits
- a filtering method is a filtering method of a signal in a receiving circuit, which is obtained by frequency converting a signal that is externally input and whose frequency is a first frequency.
- a signal or a second signal input from the outside and having a second frequency equal to the carrier frequency of the radio signal is selected, a predetermined frequency band of the selected signal is removed, and the frequency band is selected. It selects and outputs whether the signal from which is removed is output to the outside or frequency converted and output to the outside.
- the chip area can be reduced.
- FIG. 2 is a diagram showing the configuration of a receiving circuit according to the first embodiment of the present invention.
- BRIEF DESCRIPTION OF THE DRAWINGS The circuit diagram which shows an example of the mixer of the 1st Embodiment of this invention.
- FIG. 2 is a circuit diagram showing an example of a selector according to the first embodiment of the present invention.
- FIG. 7 is a diagram showing the configuration of a receiving circuit according to a second embodiment of the present invention.
- a receiver circuit includes a first mixer (10 in FIG. 1) that frequency-converts and outputs a first signal of a first frequency input from the outside, and a first mixer Selected by the first selector (11 in FIG. 1) for selecting either the signal output by the signal or the second signal of the second frequency input from the outside, and the first selector A filter (12 in FIG. 1) that removes a predetermined frequency band of the signal, and a second selector (FIG. 1) that selects an output to the outside of the signal whose frequency band has been removed or an output to a subsequent circuit. 13) and a second mixer (14 in FIG. 1), which is a circuit of a subsequent stage, frequency-converts and outputs the signal output by the second selector, and the second frequency is Equal to the carrier frequency.
- the filter may function as an input and an output with respect to the first and second selectors, respectively.
- the frequency band may be determined according to which of the first and second signals the signal selected by the first selector is frequency converted.
- a receiver circuit frequency-converts and outputs a first component of a first signal of a first frequency input from the outside, and a first mixer (60 in FIG. 6)
- a second mixer (61 in FIG. 6) for frequency-converting and outputting a second component of the first signal, a first component of the first signal subjected to frequency-conversion, or a first input from the outside
- a first selector (62 in FIG. 6) for selecting any one of the second signals of two frequencies, and either the second component of the first frequency-converted signal or the second signal
- a second selector (63 in FIG. 6) which selects one, a first filter (64 in FIG.
- the fourth selector which selects the output to the outside or the output of the circuit in the subsequent stage, and the signal output by the third selector or the signal output by the fourth selector It is provided with a third mixer (68 in FIG. 6) and a fourth mixer (69 in FIG. 6) which are circuits of the latter stage that perform frequency conversion.
- the first frequency band is determined according to whether the signal selected by the first selector is the signal output from the first mixer or the second signal, and the second frequency band May be determined according to which of the signal output by the second mixer and the second signal the signal selected by the second selector is.
- the receiver circuit further includes a first switch (80 in FIG. 8) that enables the second signal to be input to the third mixer and the fourth mixer, and the third mixer and the fourth mixer One of the two signals, the signal output by the third selector, and the signal output by the fourth selector may be frequency-converted.
- a first switch 80 in FIG. 8 that enables the second signal to be input to the third mixer and the fourth mixer, and the third mixer and the fourth mixer
- One of the two signals, the signal output by the third selector, and the signal output by the fourth selector may be frequency-converted.
- either the signal output from the first mixer (60 in FIG. 9) or the signal output from the third mixer (68 in FIG. 9) is input to the third filter (70 in FIG. 9)
- the second selector (63a in FIG. 10) is any of the second component of the frequency-converted first signal, the second signal, and the signal output by the first filter. It is also possible to select one of the signals.
- the chip area can be suppressed by combining the channel selection filter of the first reception system and the RF filter of the second reception system into one in the conventional configuration. Further, the frequency of the local oscillator can be lowered and power consumption of the drive circuit and the like can be suppressed by adopting a reception method in which frequency conversion is performed a plurality of times in accordance with a corresponding wireless standard.
- FIG. 1 shows the configuration of a receiving circuit according to a first embodiment of the present invention.
- the receiver circuit of this embodiment frequency-converts and outputs the first signal IN1 of the first frequency input from the outside, and the signal output by the mixer 10 or the second signal input from the outside ,
- a filter 12 for removing a predetermined frequency band of the signal selected by the selector 11, and an external component of the signal from which the frequency band has been removed.
- a selector 13 for selecting either the output to the signal OUT1 or the output to the mixer 14 and the mixer 14 for frequency-converting the signal output by the selector 13 and outputting it as a signal OUT2.
- the mixer 10 corresponds to a first mixer
- the selector 11 corresponds to a first selector
- the selector 13 corresponds to a second selector
- the mixer 14 corresponds to a second mixer.
- the signal bandwidth of UWB is 528 MHz.
- the reception method is a direct conversion method in which the RF signal is directly converted to baseband, and the pass bandwidth of the filter 12 is 264 MHz, which is half the signal bandwidth.
- the selector 11 selects the signal output from the mixer 10, and the selector 13 is set to select the output as the signal OUT1 to the outside.
- the input UWB signal IN 1 is frequency-converted by the mixer 10 and input to the filter 12 via the selector 11.
- the filter 12 operates as a channel selection filter and suppresses disturbance waves of adjacent channels.
- the filter 12 outputs only the desired channel signal as the signal OUT1 through the selector 13.
- the carrier frequency is 230 MHz and the passband width is 8 MHz.
- the reception method is a direct conversion method, and the pass bandwidth of the filter 12 is 264 MHz as described above.
- the selector 11 selects the second signal IN 2, and the selector 13 is set to select the output to the mixer 14.
- the input digital terrestrial television broadcast signal is input to the filter 12 through the selector 11.
- the filter 12 operates as an RF filter that selects only a signal of a predetermined carrier frequency, and outputs a desired signal to the mixer 14 via the selector 13.
- the band of the filter 12 is wide with respect to the carrier frequency, but in the RF filter, it is not necessary to suppress even an interference signal close to the carrier frequency, so this deviation is not a problem.
- the desired signal is frequency-converted by the mixer 14 and then output to the outside as a signal OUT2.
- the filter 12 serves as both a channel selection filter in the UWB receiver and an RF filter in the terrestrial digital television broadcast receiver, and one filter, which conventionally required two filters, is used. It can be put together. That is, it is possible to obtain an effect that the chip area can be suppressed as compared with the prior art.
- the receiving circuit of this embodiment can cope with not only the direct conversion method but also the dual conversion method in which frequency conversion is performed twice.
- the operation of the dual conversion system will be described by way of an example in which a signal of a wireless LAN with a carrier frequency of 4980 MHz and a signal bandwidth of 20 MHz is received as the first signal IN1.
- the selector 11 selects the signal from the mixer 10 and the selector 13 is set to select the output to the mixer 14.
- the input signal of the wireless LAN is input to the mixer 10 as the first signal IN 1, frequency-converted to an intermediate frequency band, and input to the filter 12 via the selector 11.
- interference signals outside the intermediate frequency band are suppressed.
- the signal output from the filter 12 is output to the mixer 14 via the selector 13, and after being frequency-converted from the intermediate frequency to the baseband by the mixer 14, the signal is output to the outside as a signal OUT2.
- the frequency of the local oscillation signal used in the mixer 10 can be suppressed to a low level as compared with the direct conversion system. Therefore, the power consumption of the drive circuit operating at the local oscillation frequency of the mixer 10 can be suppressed.
- the local oscillation frequency used in mixer 14 is equal to the intermediate frequency and sufficiently lower than the carrier frequency, the power consumption of the drive circuit operating at the local oscillation frequency in mixer 14 can be ignored. Therefore, by adopting the dual conversion method, it is possible to reduce the power consumption of the entire receiving apparatus as compared to the direct conversion method.
- frequency conversion may be performed by a digital circuit, and only interference wave removal may be performed.
- a digital circuit receiving a terrestrial digital audio broadcast signal having a carrier frequency of 90 MHz and a signal bandwidth of 430 kHz as the second signal IN2.
- the selector 11 selects the second signal IN2, and the selector 13 is set to select an output to the outside as the signal OUT1.
- the input terrestrial digital audio broadcast signal is input to the filter 12 through the selector 11 as the second signal IN2.
- the filter 12 suppresses unnecessary interference signals.
- the signal output from the filter 12 is output to the outside as a signal OUT1 through the selector 13.
- the 90 MHz band radio signal is converted from an analog signal to a digital signal externally, and various data processing such as demodulation is performed.
- the filter 12 functions as an anti-aliasing filter that removes an interference signal at a frequency higher than the Nyquist band of the analog-to-digital converter at the subsequent stage.
- the processing such as frequency conversion, interference signal removal, and amplitude adjustment is all performed by digital signal processing, and these processing can be performed with higher accuracy as compared with the case of analog processing.
- the signal processing content can be flexibly changed. That is, this system can flexibly cope with a plurality of wireless standards having relatively low radio frequencies.
- the filter 12 is preferably a variable filter whose bandwidth is variable according to whether the signal input from the selector 11 is the first signal IN1 or the second signal IN2. Also, it may be a variable filter whose characteristics such as low pass, band pass, high pass, and band elimination can be changed according to the corresponding wireless standard and communication environment.
- the intermediate frequency it is preferable to select the intermediate frequency so that the ratio of the local oscillation frequency in the mixer 10 to the local oscillation frequency in the mixer 14 becomes an integer when operating in the dual conversion system.
- local oscillation signals of the mixers 10 and 14 can be easily generated by performing integer division on the basis of a single local oscillation signal.
- the ratio of the local oscillation frequency in the mixer 10 to the local oscillation frequency in the mixer 14 is preferably a power of two.
- 1: 2 or 1: 4 is optimal. This makes it possible to greatly simplify the circuit configuration since a simple two-frequency divider can be used.
- the mixer 10 (14) includes NMOS transistors Q1 to Q6 and resistance elements R1 and R2.
- the sources are commonly connected to the drains of the NMOS transistor Q1, the respective gates are connected to the port B, and the differential pairs are connected to the power supply via the respective resistive elements R1 and R2.
- sources are commonly connected to the drain of the NMOS transistor Q2, their gates are connected to the port B in opposite phase, and their drains are connected to the power supply through the resistance elements R1 and R2. Construct a differential pair.
- the drains of the NMOS transistors Q3 and Q5 are commonly the one end of the port C, and the drains of the NMOS transistors Q4 and Q6 are the other end of the port C in common.
- the sources of the MOS transistors Q1 and Q2 are grounded, and their gates are connected to the port A.
- the mixer 10 (14) having such a configuration is called a Gilbert cell mixer that mixes differential signals of the ports A and B and outputs the result to the port C as a differential signal, and is generally used in an RF circuit.
- the received RF signal and the local oscillation signal are differentially input to ports A and B, respectively, and the baseband signal is differentially output from port C.
- the mixer 10 (14) includes NMOS transistors Q11 to Q14.
- the NMOS transistor Q11 has a source connected to one end of the port A, a gate connected to one end of the port B, and a drain connected to one end of the port C.
- the NMOS transistor Q12 has a source connected to the other end of the port A, a gate connected to one end of the port B, and a drain connected to the other end of the port C.
- the source is connected to the other end of the port A, the gate is connected to the other end of the port B, and the drain is connected to one end of the port C.
- the NMOS transistor Q14 has a source connected to one end of the port A, a gate connected to the other end of the port B, and a drain connected to the other end of the port C.
- the mixer 10 (14) having such a configuration is a passive mixer that mixes the differential signals of the ports A (C) and B and outputs the mixed signal to the port C (A) as a differential signal. It has the advantage of high linearity.
- the input or output signals of ports A, B and C are the same as in FIG.
- the selector 11 (13) is composed of an inverting element (inverter) INV and transfer gates TG1 and TG2 using an NMOS transistor and a PMOS transistor, and shows only one of the pair corresponding to the differential signal.
- the selector 11 (13) is composed of an inverting element (inverter) INV and transfer gates TG1 and TG2 using an NMOS transistor and a PMOS transistor, and shows only one of the pair corresponding to the differential signal.
- INV inverting element
- the transfer gate TG1 includes an NMOS transistor Q21 and a PMOS transistor Q22 which commonly connect the drain and the source.
- the respective sources of the NMOS transistor Q21 and the PMOS transistor Q22 are connected to the port A1, and the respective drains are connected to the port B1.
- the transfer gate TG2 includes an NMOS transistor Q23 and a PMOS transistor Q24 which commonly connect the drain and the source.
- the sources of the NMOS transistor Q23 and the PMOS transistor Q24 are connected to the port A0, and the drains thereof are connected to the port B1.
- the gates of the NMOS transistor Q21 and the PMOS transistor Q24 are connected to the port C1, and the gates of the PMOS transistor Q22 and the NMOS transistor Q23 are connected to the output of the inverting element INV which inverts the logic value of the port C1.
- the transfer gate TG1 when the voltage at the port C1 is at low level, the transfer gate TG1 becomes conductive, the transfer gate TG2 becomes open, and between the port A0 and the port B1 Short circuit condition.
- the transfer gate TG1 when the voltage of the port C1 is at high level, the transfer gate TG1 is in the open state, the transfer gate TG2 is in the conductive state, and the port A1 and the port B1 are shorted.
- Such selectors 11 (13) are provided corresponding to each of the differential signals. If it is necessary to operate selector 11 (13) so as not to select any of ports A0 and A1, add a logic circuit (not shown) for controlling transfer gates TG1 and TG2 to be open simultaneously. Configure to Further, by arranging three or more sets of transfer gates and controlling each with separate signals, it is possible to configure a selector that selects one path from three or more paths.
- the filter 12 is an active filter including operational amplifiers OP1 and OP2, capacitive elements C2 to C5, and resistive elements R6 to R13.
- the operational amplifier OP1 connects the capacitive element C2 and the resistive element R9 in parallel between the non-inverted output end and the non-inverted input end, and connects the capacitive element C3 and the resistive element R10 in parallel between the inverted output end and the inverted input end
- the non-inverting input end is connected to one end of the input port IN via the resistive element R6, and the inverting input end is connected to the other end of the input port IN via the resistive element R7.
- the capacitive element C4 is connected between the non-inverted output end and the non-inverted input end
- the capacitive element C5 is connected between the inverted output end and the inverted input end
- the non-inverted input end is a resistive element It is connected to the inverting output terminal of the operational amplifier OP1 through R12
- the inverting input terminal is connected to the non-inverting output terminal of the operational amplifier OP1 through the resistance element R13
- the non-inversion output terminal is the operational amplifier through the resistance element R8 Connected to the non-inverted input end of OP1 and connected the inverted output end to the inverted input end of the operational amplifier OP1 via the resistance element R11, the non-inverted output end and the inverted output end to one end and the other end of the output port OUT respectively Connecting.
- the filter 12 having such a configuration is a second-order low-pass filter that passes the low frequency band of the differential signal of the input port IN and outputs it to the output port OUT as a differential signal.
- the pass bandwidth can be changed.
- a Gm-C filter using a voltage-current converter and a capacitor, an LC filter using an inductor and a capacitor, and the like can also be used. In either case, the pass band width can be changed by controlling the element values (voltage current conversion gain, inductance, capacitance value).
- FIG. 6 shows the configuration of a receiving circuit according to the second embodiment of the present invention.
- the receiver circuit of this embodiment frequency-converts and outputs the first component of the first signal IN1 of the first frequency input from the outside, and the second component of the first signal has a frequency A mixer 61 for converting and outputting, and a selector 62 for selecting any one of the first component of the frequency-converted first signal IN1 or the second signal IN2 of the second frequency input from the outside.
- a selector 63 for selecting one of the first component of the first signal subjected to frequency conversion and the second signal, and removing the first frequency band of the signal selected by the selector 62.
- the filter 64 the filter 65 for removing the second frequency band of the signal selected by the selector 63, the output of the signal from which the first frequency band has been removed, to the outside as the signal OUT1, or to the subsequent circuit
- mixers 68 and 69 which are circuits of the latter stage that frequency-converts and outputs.
- Mixers 68 and 69 respectively output signals OUT2 and OUT4 to the outside.
- the mixers 60, 61, 68 and 69 correspond to the first, second, third and fourth mixers, respectively, and the selectors 62, 63, 66 and 67 correspond to the first, second and the third, respectively.
- the filters 64 and 65 correspond to the first and second filters, respectively.
- the stop bands of the filters 64 and 65 correspond to the first and second frequency bands, respectively.
- the receiver circuit of this embodiment performs orthogonal demodulation at the same time as frequency conversion by using local oscillation signals whose frequencies are mutually equal and the phases are mutually different by 90 degrees in the mixers 60 and 61, and the I-phase is used as the first component.
- the baseband signal of the component of (In-phase) and the component of Q phase (Quadrature-phase) as a second component is obtained.
- baseband signals of I phase and Q phase are obtained as the signals OUT 2 and OUT 4.
- both of the filters 64 and 65 can be used in parallel or only one of them can be used. Specifically, if both of the selectors 62 and 63 select the second signal IN2 and both the selectors 66 and 67 select the output to the mixers 68 and 69, the filters 64 and 65 are arranged in parallel. As a result, the noise is lower than when only one of the filters is used. In this state, if the selectors 63 and 67 are opened, only the filter 64 is used and the circuit of the filter 65 can be cut off. That is, power consumption can be reduced as compared to the case where both filters are used.
- the mixers 60 and 61 perform frequency conversion to an intermediate frequency without performing quadrature demodulation, and the mixers 68 and 69 simultaneously perform quadrature demodulation on the intermediate frequency. It is also possible to perform frequency conversion from to baseband.
- the selectors 62 and 63 select the outputs from the mixers 60 and 61, respectively, and the selectors 66 and 67 are set to select the outputs to the mixers 68 and 69, respectively.
- the mixers 60 and 61 use a common local oscillation signal, and the mixers 68 and 69 use local oscillation signals whose phases are different by 90 degrees.
- I-phase and Q-phase baseband signals are obtained as the signals OUT2 and OUT4, respectively.
- the filters 64 and 65 are variable filters whose bandwidth is variable according to whether the input signal is the first signal IN1 or the second signal IN2. Also, it may be a variable filter whose characteristics such as low pass, band pass, high pass, and band elimination can be changed according to the corresponding wireless standard and communication environment.
- the intermediate frequency it is preferable to select the intermediate frequency so that the ratio of the local oscillation frequency in the mixers 60 and 61 to the local oscillation frequency in the mixers 68 and 69 is an integer when operating in the dual conversion system.
- local oscillation signals of the mixers 68 and 69 and the mixers 68 and 69 can be easily generated by performing integer division on the basis of a single local oscillation signal.
- the ratio of the local oscillation frequency in the mixers 60 and 61 to the local oscillation frequency in the mixers 68 and 69 is a power of two. In particular, 1: 2 or 1: 4 is optimal. This makes it possible to greatly simplify the circuit configuration since a simple two-frequency divider can be used.
- FIG. 7 shows the configuration of a receiving circuit according to a third embodiment of the present invention.
- the receiving circuit of this embodiment is different from the receiving circuit of the second embodiment in that filters 70 and 71 are added to the subsequent stages of the mixers 68 and 69, respectively.
- the filters 70 and 71 correspond to the third and fourth filters, respectively, and the stop bands of the filters 70 and 71 correspond to the third and fourth frequency bands, respectively.
- the receiving circuit of this embodiment for example, when receiving the first signal IN1, channel selection is performed by the filters 64 and 65, and when receiving the second signal IN2, the interference waves are removed by the filters 64 and 65, and the filter Channel selection can be performed at 70 and 71.
- channel selection can be performed by the filters 70 and 71.
- filters 70 and 71 have complex bands capable of suppressing an image signal. It may be a pass filter.
- FIG. 8 shows the configuration of a receiving circuit according to a fourth embodiment of the present invention.
- the receiving circuit of this embodiment differs from the receiving circuit of the second embodiment in that a switch 80 is added to the path where the second signal IN2 is input to the mixers 68 and 69.
- the switch 80 corresponds to a first switch.
- the mixer 68 frequency-converts the signal selected by the selector 66 or the second signal IN 2 input via the switch 80, and the mixer 69 selects the signal selected by the selector 67 or the switch 80. Frequency-converts the second signal IN2 input via the
- the receiving circuit of this embodiment can simultaneously receive both the first signal IN1 and the second signal IN2. That is, selectors 62 and 63 are set to select the signals of mixers 60 and 61, selectors 66 and 67 select the output to the outside, and switch 80 is in the conductive state. At this time, the I-phase component of the first signal IN1 is output to the outside as a signal OUT1 through the mixer 60, the selector 62, the filter 64, and the selector 66, and the Q-phase component of the first signal IN1 is a mixer It is outputted to the outside as a signal OUT3 through the selector 61, the selector 63, the filter 65 and the selector 67.
- the I-phase component of the second signal IN2 is output to the outside as the signal OUT2 through the switch 80 and the mixer 68, and the Q-phase component of the second signal IN2 is output through the switch 80 and the mixer 69. It is output to the outside as a signal OUT4.
- I- and Q-phase basebands are obtained for each of the first and second signals IN1 and IN2. That is, simultaneous reception can be performed for a plurality of wireless standards such as UWB and terrestrial digital broadcasting.
- the operation when the switch 80 is in the open state is similar to that of the second embodiment.
- FIG. 9 shows the configuration of a receiving circuit according to a fifth embodiment of the present invention.
- the receiving circuit of this embodiment is, compared with the third embodiment, a selector 90 which selects and outputs either the output of the mixer 60 or the output of the mixer 68, the output of the mixer 61, or the mixer The difference is that a selector 91 for selecting and outputting one of the 69 outputs is added.
- the selectors 90 and 91 correspond to the fifth and sixth selectors, respectively.
- the selectors 62, 63 select the second signal IN2 or open for any path, and the selectors 90, 91 are set to select the outputs of the mixers 60, 61, respectively.
- the first signal IN1 is frequency-converted to the baseband by the mixers 60 and 61 and simultaneously orthogonally demodulated, and then output to the filters 70 and 71 through the selectors 90 and 91, respectively.
- the receiver circuit of this embodiment is effective when the carrier frequency is high but the signal bandwidth is narrow, and power consumption can be reduced by blocking the circuits of the filters 64 and 65 and the mixers 68 and 69 which are not used. be able to.
- FIG. 10 shows the configuration of a receiving circuit according to a sixth embodiment of the present invention.
- the receiving circuit of this embodiment differs from the second embodiment in that the selector 63 is replaced with a selector 63a.
- the selector 63 a selects one of the three signals of the output of the mixer 61, the second signal IN 2, and the output of the filter 64, and outputs the selected one to the filter 65.
- the selector 62 selects the second signal IN2
- the selector 66 is open, and the selector 63a is connected to the output of the filter 64
- the selector 67 is set to be connected to the mixers 68, 69.
- the filters 64 and 65 are cascaded, the order of the filters is doubled and steeper cutoff characteristics can be obtained. That is, even in the condition where a larger disturbing signal is present, the disturbing signal can be sufficiently suppressed and only the desired signal can be received.
- the selector 62 selects the output of the mixer 60
- the selector 66 is in the open state
- the selector 63a is connected to the output of the filter 64
- the first signal IN1 can also be received.
- the selector 67 selects the output to the mixers 68 and 69, and the mixers 68 and 69 perform quadrature demodulation in a dual conversion scheme.
- the selector 67 needs to select an output to the outside to perform quadrature demodulation on the outside.
- the operation when the selector 63a selects the mixer 61 or the second signal IN2 is similar to that of the second embodiment.
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Abstract
Description
本発明は、日本国特許出願:特願2011-069489号(2011年03月28日出願)の優先権主張に基づくものであり、同出願の全記載内容は引用をもって本書に組み込み記載されているものとする。
本発明は、受信回路およびフィルタリング方法に関し、特に複数の無線規格に対応する受信回路およびそのフィルタリング方法に関する。
図1に、本発明の第1の実施形態である受信回路の構成を示す。本実施形態の受信回路は、外部から入力された第1の周波数の第1の信号IN1を周波数変換して出力するミキサ10と、ミキサ10によって出力された信号、または外部から入力された第2の周波数の第2の信号IN2のいずれか一方を選択する選択器11と、選択器11によって選択された信号の所定の周波数帯域を除去するフィルタ12と、周波数帯域が除去された信号の、外部へ信号OUT1として出力、またはミキサ14への出力のいずれか一方を選択する選択器13と、選択器13によって出力された信号を周波数変換して信号OUT2として出力するミキサ14を備える。なお、ミキサ10が第1のミキサ、選択器11が第1の選択器、選択器13が第2の選択器、ミキサ14が第2のミキサに対応する。
図6に、本発明の第2の実施形態に係る受信回路の構成を示す。本実施形態の受信回路は、外部から入力された第1の周波数の第1の信号IN1の第1の成分を周波数変換して出力するミキサ60と、第1の信号の第2の成分を周波数変換して出力するミキサ61と、周波数変換された第1の信号IN1の第1の成分、または外部から入力された第2の周波数の第2の信号IN2のいずれか一方を選択する選択器62と、周波数変換された第1の信号の第1の成分、または第2の信号のいずれか一方を選択する選択器63と、選択器62によって選択された信号の第1の周波数帯域を除去するフィルタ64と、選択器63によって選択された信号の第2の周波数帯域を除去するフィルタ65と、第1の周波数帯域が除去された信号の、信号OUT1として外部への出力、または後段の回路への出力を選択する選択器66と、第2の周波数帯域が除去された信号の、信号OUT3として外部への出力、または後段の回路への出力を選択する選択器67と、選択器66および67によって出力された信号を周波数変換して出力する、後段の回路であるミキサ68および69を備える。ミキサ68および69は、それぞれ信号OUT2、OUT4を外部に出力する。
図7に、本発明の第3の実施形態である受信回路の構成を示す。本実施形態の受信回路は、第2の実施形態の受信回路と比較して、ミキサ68、69の後段に、それぞれフィルタ70、71を追加した点が異なる。フィルタ70、71は、それぞれ第3、第4のフィルタに対応し、フィルタ70、71の阻止帯域は、それぞれ第3、第4の周波数帯域に対応する。本実施形態の受信回路では、例えば、第1の信号IN1の受信時には、フィルタ64、65でチャネル選択を行い、第2の信号IN2の受信時には、フィルタ64、65で妨害波を除去し、フィルタ70、71でチャネル選択を行うことができる。同様にデュアルコンバージョン方式でも、フィルタ70、71でチャネル選択を行うことができる。
図8に、本発明の第4の実施形態である受信回路の構成を示す。本実施形態の受信回路は、第2の実施形態の受信回路と比較して、第2の信号IN2がミキサ68、69に入力される経路に開閉器80を追加した点が異なる。ここで、開閉器80は、第1の開閉器に対応する。また、ミキサ68は、選択器66によって選択された信号または開閉器80を介して入力される第2の信号IN2を周波数変換し、ミキサ69は、選択器67によって選択された信号または開閉器80を介して入力される第2の信号IN2を周波数変換する。
図9に、本発明の第5の実施形態である受信回路の構成を示す。本実施形態の受信回路は、第3の実施形態と比較して、ミキサ60の出力か、ミキサ68の出力のいずれか一方を選択して出力する選択器90と、ミキサ61の出力か、ミキサ69の出力のいずれか一方を選択して出力する選択器91とを追加した点が異なる。選択器90、91は、それぞれ第5、第6の選択器に対応する。
図10に、本発明の第6の実施形態である受信回路の構成を示す。本実施形態の受信回路は、第2の実施形態と比較して、選択器63を選択器63aに置き換えた点が異なる。選択器63aは、ミキサ61の出力、第2の信号IN2、フィルタ64の出力の3つの信号のうちのいずれか1つを選択し、フィルタ65に出力する。本実施形態の受信回路は、第2の信号IN2の受信時に、選択器62は第2の信号IN2を選択し、選択器66は開放状態とし、選択器63aはフィルタ64の出力に接続し、選択器67はミキサ68、69に接続するように設定する。これによって、フィルタ64、65が縦続接続されるため、フィルタの次数が倍になり、より急峻な遮断特性を得ることができる。すなわち、より大きな妨害信号が存在する条件においても、妨害信号を十分抑圧し、所望信号のみを受信することができる。
11、13、62、63、63a、66、67、90、91 選択器
12、64、65、70、71 フィルタ
80 開閉器
C2~C5 容量素子
INV 反転素子
OP1、OP2 演算増幅器
Q1~Q6、Q11~Q14、Q21、Q23 NMOSトランジスタ
Q22、Q24 PMOSトランジスタ
R1、R2、R6~R13 抵抗素子
TG1、TG2 トランスファゲート
Claims (10)
- 外部から入力された第1の周波数の第1の信号を周波数変換して出力する第1のミキサと、
前記第1のミキサによって出力された信号、または外部から入力された第2の周波数の第2の信号のいずれか一方を選択する第1の選択器と、
前記第1の選択器によって選択された信号の所定の周波数帯域を除去するフィルタと、
前記周波数帯域が除去された信号の、外部への出力、または後段の回路への出力を選択する第2の選択器と、
前記第2の選択器によって選択された信号を周波数変換して出力する、前記後段の回路である第2のミキサと、
を備え、
前記第2の周波数は、無線信号の搬送波周波数に等しいことを特徴とする受信回路。 - 前記フィルタは、前記第1および第2の選択器に対して、それぞれ入力側および出力側として機能することを特徴とする請求項1記載の受信回路。
- 前記周波数帯域は、前記第1の選択器によって選択された信号が、前記周波数変換された前記第1の信号および前記第2の信号のいずれであるかに従って決定されることを特徴とする請求項1または2記載の受信回路。
- 外部から入力された第1の周波数の第1の信号の第1の成分を周波数変換して出力する第1のミキサと、
前記第1の信号の第2の成分を周波数変換して出力する第2のミキサと、
前記周波数変換された前記第1の信号の第1の成分、または外部から入力された第2の周波数の第2の信号のいずれか一方を選択する第1の選択器と、
前記周波数変換された前記第1の信号の第2の成分、または前記第2の信号のいずれか一方を選択する第2の選択器と、
前記第1の選択器によって選択された信号の第1の周波数帯域を除去する第1のフィルタと、
前記第2の選択器によって選択された信号の第2の周波数帯域を除去する第2のフィルタと、
前記第1の周波数帯域が除去された信号の、外部への出力、または後段の回路への出力を選択する第3の選択器と、
前記第2の周波数帯域が除去された信号の、外部への出力、または前記後段の回路への出力を選択する第4の選択器と、
前記第3の選択器によって出力された信号または前記第4の選択器によって出力された信号を周波数変換する、前記後段の回路である第3のミキサおよび第4のミキサと、
を備えることを特徴とする受信回路。 - 前記第1の周波数帯域は、前記第1の選択器によって選択された信号が、前記第1のミキサが出力する信号および前記第2の信号のいずれであるかに従って決定され、
前記第2の周波数帯域は、前記第2の選択器によって選択された信号が、前記第2のミキサが出力する信号および前記第2の信号のいずれであるかに従って決定されることを特徴とする請求項4記載の受信回路。 - 前記第3のミキサが出力する信号の第3の周波数帯域を除去する第3のフィルタと、
前記第4のミキサが出力する信号の第4の周波数帯域を除去する第4のフィルタと、
をさらに備えることを特徴とする請求項4または5に記載の受信回路。 - 前記第2の信号を前記第3のミキサおよび前記第4のミキサに入力可能とする第1の開閉器をさらに備え、
前記第3のミキサおよび前記第4のミキサは、前記第2の信号と、前記第3の選択器によって出力された信号と、前記第4の選択器によって出力された信号とのいずれかの信号を周波数変換することを特徴とする請求項4乃至6のいずれか一項に記載の受信回路。 - 前記第1のミキサが出力する信号または前記第3のミキサが出力する信号のいずれか一方を前記第3のフィルタに入力可能とする第5の選択器と、
前記第2のミキサが出力する信号または前記第4のミキサが出力する信号のいずれか一方を前記第4のフィルタに入力可能とする第6の選択器と、
をさらに備えることを特徴とする請求項4乃至7のいずれか一項に記載の受信回路。 - 前記第2の選択器は、前記周波数変換された前記第1の信号の第2の成分と、前記第2の信号と、前記第1のフィルタによって出力された信号とのいずれかの信号を選択することを特徴とする請求項1乃至8のいずれか一項に記載の受信回路。
- 受信回路における信号のフィルタリング方法であって、
外部から入力され、周波数が第1の周波数である信号を周波数変換して得られる第1の信号、または、外部から入力され、無線信号の搬送波周波数に等しい第2の周波数である第2の信号の、いずれか一方を選択し、
前記選択された信号の所定の周波数帯域を除去し、
前記周波数帯域が除去された信号を、外部へ出力するか、または周波数変換して外部へ出力するかを選択して出力することを特徴とするフィルタリング方法。
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