JP2008278397A - Reception apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reception apparatus in which current consumption is reduced by using a low-pass filter in which current consumption is reduced and a filter order is low when hopping to a frequency band to which an interference signal is not proximate, and switching to and using a low-pass filter, synchronously to frequency hopping, in which current consumption is much and a filter order is high, when frequency-hopping to a frequency band to which an interference signal is close. <P>SOLUTION: By frequency allocation, a frequency band to which an interference wave is close and a frequency band to which an interference wave is not close are generated. A reception apparatus of the present invention comprises a low-pass filter/amplifier for each frequency band and in response to switching a reception frequency band. A controller 21 switches these low-pass filters/amplifiers to avoid using a low-pass filter with a high order in a frequency band on which an interference wave hardly rides, thereby suppressing power consumption. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a receiving apparatus that receives a signal subjected to frequency hopping after frequency conversion.

  In recent years, UWB (Ultra Wide Band) has attracted attention as a wireless communication system that realizes short-distance high-speed wireless transmission, and industry association WiMedia Alliance is promoting an MB-OFDM UWB system.

  FIG. 3 shows the frequency allocation of the MB-OFDM method defined by the WiMedia Alliance. As shown in the figure, band group # 1 consisting of bands # 1 to # 3 having center frequencies of 3432 MHz, 3960 MHz, and 4488 MHz, and bands # 4 to # 6 having center frequencies of 5016 MHz, 5548 MHz, and 6027 MHz, respectively. Band group # 2, band group # 4 consisting of bands # 7 to # 9 with center frequencies of 6600 MHz, 7128 MHz and 7656 MHz, and band group # 4 consisting of bands # 10 to # 12 with center frequencies of 8184 MHz, 8712 MHz and 9240 MHz And band group # 5 including bands # 13 and # 14 having center frequencies of 9768 MHz and 10296 MHz. Of these, the WiMedia standard requires that three bands of band group # 1 be used.

  On the other hand, band # 1 is allocated as a frequency band for radio astronomy, and at present, it is difficult to use this band. Therefore, it is limited to use of band # 2 and band # 3 in Japan.

  FIG. 4 shows an interference wave close to band group # 1. When data transmission is performed by hopping band # 1, band # 2, and band # 3, the 4900 MHz-5000 MHz band WLAN system is the interference signal closest to band # 3. The 4900 MHz-5000 MHz band was standardized for use in Japan as IEEE 802.11j in December 2004 and is used. At present, it cannot be said that the use of this band # 3 is ensured. When a high-speed wireless LAN signal having a center frequency of 4920 MHz and a frequency channel width of 20 MHz is generated at the timing of frequency hopping to band # 3 of band group # 1, the center frequency is 432 MHz (= 4920 MHz-4488 MHz) at the mixer output, There is a possibility that a proximity interference signal having a frequency channel width of 20 MHz is generated.

  Certainly, even when only band # 2 is used, the communication speed can be secured as a UWB system. However, when three bands are used, a communication distance of about 10 m can be secured, whereas in a situation where only one band can be used, the communicable distance can be maintained at 4 m. Therefore, the use of band # 3 is inevitable for securing a communicable distance.

  FIG. 5 shows a configuration example of a receiver used in the MB-OFDM UWB system disclosed in Japanese Patent Laid-Open No. 2006-203686 (hereinafter referred to as Patent Document 1). The receiver of Patent Document 1 employs a direct conversion method in which a local signal having the same frequency as the center frequency of the received signal is multiplied and converted directly into a baseband signal. However, each frequency band to be subjected to frequency hopping is used. Are arranged in parallel, and a high-pass filter unit for switching connection of the capacitors in synchronization with frequency hopping is provided to remove the DC offset.

Japanese Patent Laid-Open No. 2000-31161 (hereinafter referred to as Patent Document 2) also shows a method of changing the attenuation while maintaining the passband characteristics of the mobile terminal with respect to the used frequency band substantially the same. ing. That is, the attenuation pole of the filter is determined by at least one of the capacitor and the inductor, and the attenuation amount is varied by changing the capacitor and the inductance.
JP 2006-203686 A JP 2000-31161 A

  As described above, in a wireless communication system in which a plurality of frequency bands are frequency hopped, there may be a frequency band in which an interference signal is close and a frequency band in which the interference signal is not close.

  FIG. 6 shows the frequency characteristics of the low-pass filter required when the above-described high-speed wireless LAN signal having the center frequency of 4920 MHz and the frequency channel width of 20 MHz is generated at the timing of frequency hopping in band # 2 and band # 3. FIG. The frequency bandwidth of the baseband UWB signal is 264 MHz, and a high-performance low-pass filter with high current consumption and high order is necessary to remove the proximity interference signal of 432 MHz. On the other hand, when a high-speed wireless LAN signal is generated at the timing of hopping to band # 2, an interference signal having a center frequency of 960 MHz (4920 MHz-3960 MHz) is generated at the mixer output. When the 432 MHz interference signal and the 960 MHz interference signal generated at the timing of hopping to band # 3 and band # 2 are attenuated by the same signal level, the filter characteristics are attenuated to characteristics (1) and (2), respectively. The amounts are attenuation amounts (1) and (2), respectively. As can be seen from this, the comparison of attenuation amounts is attenuation amount (1)> attenuation amount (2), and therefore, there is no need for a high-performance low-pass filter at the timing of hopping to band # 2.

  As can be seen from this, when the desired signal and the interference signal are close to each other, a high-performance low-pass filter that consumes a large amount of current and has a high filter order is necessary. On the other hand, when there is no interfering signal, or when the desired signal and the interfering signal are not close, such a high-performance low-pass filter is not necessary.

  In the circuit of Patent Document 1 including one type of high-performance low-pass filter, this high-performance low-pass filter becomes overspec when demodulating a signal that has been frequency hopped into a frequency band in which no disturbing signal is close.

  Further, the use environment in the invention described in Patent Document 2 considers the use of a single frequency band, and does not assume frequent change of the band such as frequency hopping. Frequent changes in the capacitor and inductance settings are problematic in terms of followability.

  The present invention has been made in view of these circumstances, and when hopping is performed in a frequency band where the disturbing signal is not close, a low-pass filter with a low filter order with low current consumption is used, and the disturbing signal is close. It is an object of the present invention to provide a receiving device that reduces current consumption by using a low-pass filter having a high filter order and a high-order filter in synchronization with frequency hopping when frequency hopping is performed in a certain frequency band. .

  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.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  A receiving apparatus according to the present invention includes a first local signal generator and a mixer circuit that perform demodulation in a first frequency band that is less affected by an interference wave, and a first receiving circuit that includes a first low-pass filter that removes high-frequency components. A second local signal generator and a mixer circuit for demodulating a second frequency band affected by an interference wave due to the allocation of the frequency band, and a second receiving circuit having a second low-pass filter for removing high-frequency components Including a first receiving circuit and a second receiving circuit for performing communication while switching, wherein the order of the first low-pass filter is smaller than the order of the second low-pass filter. And

  The receiving device further includes a control device, and the control device switches between the first frequency band and the second frequency band at a predetermined period.

  Further, in this receiving device, the control device waits for the transition of the first low-pass filter to the steady state and starts using the first frequency band, and waits for the transition of the second low-pass filter to the steady state, It may be characterized by starting use.

  In this receiving device, the control device cuts off the power supply of the second low-pass filter in synchronization with the use of the first frequency band, and cuts off the power supply of the first low-pass filter in synchronization with the use of the second frequency band. It may be characterized by.

  It is also included in the range that the communication method of this receiving apparatus is UWB (Ultra Wide Band).

  The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

  According to the present invention, a high-performance low-pass filter with a high filter order is used when the presence of an interference signal is predicted in the adjacent frequency band in advance, and the filter order is reduced when no interference signal is expected in the adjacent frequency band. By receiving a desired signal using a low-pass filter, it is possible to supply a receiving apparatus suitable for the use environment and a wireless communication system using the receiving apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of a UWB direct conversion receiver according to the present invention. In the following description, it is assumed that communication is performed using only band # 2 and band # 3 of band group # 1.

  The receiving apparatus includes an antenna 1, a band pass filter 2, an LNA (low noise amplifier) 3, a multiband local signal source 4, mixers 5 and 6, a power source 7, and an LPF / PGA (low pass filter / programmable gain amplifier) 8. 9, 10, 11, ADC (analog / digital converter) 12, 13, BB-PHY (baseband signal processing unit) 14, LPF / PGA power switches 15, 16, received signal switches 17, 18, 19, 20 and a controller 21.

  The antenna 1 is a device for receiving a UWB RF radio signal.

  The band pass filter 2 is a filter for passing only a certain band of a signal received by the antenna 1 for noise removal.

  An LNA (low noise amplifier) 3 is an amplifier for amplifying a received signal and obtaining a signal strength that can withstand decoding. The signal processing from here is separated into an I component and a Q component, and demodulation processing is performed for each.

  The multiband local signal source 4 generates local signals of band # 2 and # 3 having center frequencies of 3960 MHz and 4488 MHz, and synchronizes with the frequency hopping to generate a local signal whose phase is shifted by 90 degrees. Generate. In this embodiment, the multiband local signal source is expressed as one circuit, but there is no problem even if a local signal generation source is provided for each frequency.

  The mixer 5 is a circuit for mixing the local signal from the multiband local signal source 4 with the I component signal. Similarly, the mixer 6 is a circuit that mixes the local signal from the multiband local signal source 4 with the Q component signal. As described above, the phase of the output signal from the multiband local signal source 4 is 90 degrees for the I component and the Q component.

  The power supply 7 is a power supply module for operating each LPF / PGA.

  The LPF / PGA is a circuit that amplifies the remaining low frequency components after removing the high frequency components of the output of the mixer with a low pass filter. Of these, LPF / PGA8 includes a filter used for the I component of band # 3, and LPF / PGA9 includes a filter having an nth order filter order used for the I component of band # 2. Similarly, the LPF / PGA 10 includes a filter used for the Q component of band # 3, and the LPF / PGA 11 includes a filter having an n-th order filter order used for the Q component of band # 2. That is, LPF / PGA 8 and LPF / PGA 10 are used simultaneously for band # 3. In addition, LPF / PGA 9 and LPF / PGA 11 are used simultaneously for band # 2.

  The ADC (analog / digital converter) is a converter that converts the signal amplified by the LPF / PGA 11 into a digital signal. The ADC 12 is for the I component, and the ADC 13 is for the Q component.

  The BB-PHY (baseband signal processing unit) 14 is a digital signal processing unit that converts a digital signal extracted by each ADC into a significant format and demodulates it. The receiving device uses this data in an application or the like.

  In UWB which uses only one out of two bands, it is not preferable in terms of power consumption to always operate all LPF / PGA. Therefore, low power consumption is realized by operating only one of the LPF / PGA power switches 15 and 16 for the band # 2 or the band # 3.

  The reception signal switches 17, 18, 19, and 20 prevent the generation of noise by sending reception signals only to the operating LPF / PGA.

  The controller 21 is a circuit that controls the operation of the multiband local signal source 4, LPF / PGA power switches 15 and 16, and switches 17, 18, 19, and 20. The operation of this controller is described below.

  FIG. 2 is a timing chart according to the embodiment of the present invention.

  As described above, band # 2 and band # 3 are subjected to alternative processing. Therefore, if the corresponding LPF / PGA is operated only during reception of each band, it contributes to power saving. However, each low-pass filter requires time from power-on until it settles in a steady state. As described above, filters having different orders are used for the band # 2 and the band # 3, and it is conceivable that the time until the steady state is reached is different.

  Therefore, when operating each LPF / PGA, the time to the steady state is assumed in advance, and the power is turned on ahead of the timing of T2 [nSec] or T3 [nSec] frequency hopping. On the other hand, the reception signal switches 17, 18, 19, and 20, which are switches of the input signal line of the reception signal, switch on / off at the timing of frequency hopping. That is, the transition to the steady state is completed before the controller 21 performs frequency hopping.

  In this way, the number of uses per unit time of the LPF / PGA 8 and LPF / PGA 10 which are high-performance low-pass filters having a high filter order can be reduced, and current consumption can be reduced.

  Needless to say, switching of the frequency of the local signal from the multiband local signal source 4 is performed at the timing of frequency hopping.

  In the above, it is assumed that band # 2 and band # 3 are used. However, if band # 1 is used, it is necessary to increase the circuit configuration for that purpose. That is, there are only four LPF / PGAs when using two bands, but there are six LPF / PGAs when the configuration is based on the use of three bands. Similarly, the number of LPF / PGA power switches is increased from two to three, and the number of received signal switches is increased from four to six. However, such an extension of the circuit can be easily conceived by those skilled in the art, and is omitted here.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. Needless to say.

  A communication method involving frequency hopping, specifically, use in a receiving apparatus such as UWB or cdma2000 can be considered. In particular, UWB has a different frequency allocation for each country, and the presence / absence of a signal that can be an interfering wave is also different.

It is a block diagram showing the circuit structure of the receiver concerning embodiment of this invention. It is a timing chart in connection with embodiment of this invention. It is a figure showing the frequency allocation of the MB-OFDM system prescribed | regulated by WiMedia Alliance. It is a figure for demonstrating the jamming wave which adjoins the band # 3 of MB-OFDM system. It is a block diagram showing the circuit structure of the receiver concerning a prior art. FIG. 10 is a characteristic diagram showing frequency characteristics of a low-pass filter required when a high-speed wireless LAN signal is generated at a timing when frequency hopping is performed in band # 2 and band # 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Antenna, 2 ... Band pass filter, 3 ... LNA (low noise amplifier),
4 ... multiband local signal source, 5, 6 ... mixer, 7 ... power supply,
8, 9, 10, 11 ... LPF / PGA
(Low-pass filter / programmable gain amplifier),
12, 13 ... ADC (analog-digital converter),
14 ... BB-PHY (baseband signal processing unit),
15, 16 ... LPF / PGA power switch,
17, 18, 19, 20 ... received signal switch, 21 ... controller

Claims (5)

A first receiving circuit having a first low-pass filter for removing at least a high-frequency component;
A second receiving circuit having a second low-pass filter for removing at least high-frequency components;
A communication method receiving apparatus for performing communication while switching between the first receiving circuit and the second receiving circuit,
The receiving apparatus, wherein the order of the first low-pass filter is smaller than the order of the second low-pass filter.   The receiving device according to claim 1, further comprising a control device, wherein the control device switches between the first frequency band and the second frequency band at a predetermined period.   3. The receiving device according to claim 2, wherein the control device waits for the steady state transition of the first low-pass filter to start using the first frequency band, and waits for the steady state transition of the second low-pass filter. And starting to use the second frequency band.   3. The receiving device according to claim 2, wherein the control device disconnects the power source of the second low-pass filter in synchronization with the use of the first frequency band, and the control device synchronizes with the use of the second frequency band. A receiving apparatus characterized by cutting off the power supply of the first low-pass filter.   5. The receiving apparatus according to claim 1, wherein the communication method is UWB (Ultra Wide Band).

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