JPH11177447A - Receiver with multi-rate transmission function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify an IF filter of the receiver and to improve a phase noise characteristic of a synthesizer. SOLUTION: This receiver is provided with a frequency conversion means 2 that coverts a received high frequency signal into an intermediate frequency signal, a first filter means 4 connecting with an output terminal of the means 2, an orthogonal demodulation means 6 connecting with an output terminal of the means 2, a second liter means 7 connecting with an output terminal of the means 6, and an A/D converter means 8 connecting with an output terminal of the means 7. The receiver conducts communication through the use of signals with plural bands. The first filter means 4 has a band-pass filter 40 that passes a band width equivalent to at least a sum of signals with the widest band width and signals with the narrowest band width among plural hand signals received via the frequency conversion means 2. Characteristics of base- band filters of the second filter means 7 are made variable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a receiver, and more particularly, to a receiver having a multi-rate transmission function for performing communication in a plurality of bandwidths.

[0002]

2. Description of the Related Art In recent years, with the spread of mobile communication systems,
Demand for mobile communication terminals is increasing. At the same time, communication contents which used to be only voice communication in the past have been diversified to transmission by data and facsimile, and further to image communication. In order to cope with these diversified communication contents, it is necessary to add a multi-rate transmission function to the system. That is, this is a function that realizes efficient transmission of various data by making the bandwidth variable.

Conventionally, this type of receiver has been configured as shown in FIG. In FIG. 21, the receiver includes, for example, a frequency conversion means 2 for converting a frequency of a signal received by the antenna 1 or the like, a synthesizer 3 for outputting a predetermined frequency to the frequency conversion means 2, a first to n-th intermediate frequencies Filter (hereinafter referred to as IF filter if necessary) 4
a first filter means 4 having a to 4n in multiple stages;
Switch 5A provided in front of first filter means 4
And a switching means 5 including a switch 5B provided at a subsequent stage, and first and second switches provided at a subsequent stage of the switch 5B.
Demodulation means 6 having quadrature demodulators 6a and 6b
Second filter means 7 having first and second baseband filters 7a and 7b;
A / D converter 8 having A / D converters 8a and 8b, output terminals 9A and 9B, and switches 5A and 5B
And a system band switching signal generation unit 10 for supplying a system band switching signal to the second filter unit 7.

Next, the basic operation of a conventional receiver will be described with reference to the drawings.

[0005] The high-frequency signal input to the frequency conversion means 2 is converted into an intermediate frequency signal (hereinafter referred to as an IF signal) having a predetermined frequency by the frequency conversion means 2 and output. An intermediate frequency (hereinafter referred to as I
F) is input to any of the IF filters 4a to 4n. Here, IF filters 4a to 4n
Are provided for each of a plurality of bandwidth types of the transmitted signal. The IF filters 4a to 4a
n is configured to be switched to any one by switch switching means 5 controlled by a system band switching signal.

[0006] The IF signal filtered by any one of the filters 4a, 4b, 4c or 4n of the first filter means 4 switched by the switching means 5 is input to the quadrature demodulation means 6, where the IF signal is filtered. The signals are converted into I-channel and Q-channel baseband signals and output.

[0007] The output signal of the quadrature demodulation means 6 is input to a second filter means comprising baseband filters 7a and 7b. The baseband filters 7a and 7b are low-pass filters whose cutoff frequency can be changed by a switching signal output from the system band switching signal generating means 10. The baseband signal filtered by the second filter 7 is input to the first and second A / D converters 8a and 8b of the A / D converter 8, and is converted from an analog signal to a digital signal. . Thereafter, the digital signal is output through output terminals 9a and 9b and demodulated by a demodulator (not shown).

[0008] The synthesizer 3 oscillates a local oscillation frequency such that the center frequency of the desired signal included in the input signal is frequency-converted so as to match the predetermined IF signal frequency. Is supplied to the frequency conversion means 2. At this time, the oscillation frequency of the synthesizer 3 is controlled by a control signal (not shown). In other words, the oscillation frequency f _LO of the synthesizer 3 is, for example, a frequency of a difference f _RF −f _IF between the center frequency f _{RF of the} desired signal and a predetermined frequency f _IF of the IF signal.

When signals of a plurality of transmission rates are received by using the conventional receiver having the above-mentioned configuration, first, (1) the first filter means 4 is switched by the switch means 58 using the system band switch signal. Switching to a filter suitable for a desired bandwidth among the IF filters 4a to 4n, (2) changing the bandwidth of the baseband filters 7a and 7b of the second filter means 7 to an appropriate value, and (3) The synthesizer 3 oscillates the above-mentioned local oscillation frequency.

The above operation will be described below with reference to specific numbers. Assume that the system bandwidth can be selected from a minimum bandwidth and a bandwidth that is an integral multiple of the minimum bandwidth. For example, the system bandwidth is 5 MHz, 10 MHz
z, 20 MHz. Carrier frequency is 2GH
FIG. 22 shows a state in which the z band and the system bandwidth are set to 60 MHz, and signals of the plurality of bandwidths are allocated.

The configuration of a conventional receiver whose IF is designed at 200 MHz is as follows. Assuming that the first filter means 4 has a wider bandwidth in the order of the IF filters 4a, 4b and 4c, the IF filter 4a has a bandwidth of 5 MHz.
And a center frequency of 200 MHz and an IF filter 4b having a bandwidth of 10 MHz and a center frequency of 200 MHz and an IF filter 4b.
c is a bandpass filter having a bandwidth of 20 MHz and a center frequency of 200 MHz. IF filter 4a
FIG. 23 (a) shows the respective frequency characteristics of FIG.
(B) and (c).

Next, the operation when receiving a plurality of rates will be described. First, when a signal having a center frequency of 200 MHz is received at the time of transmission at the maximum bandwidth of 20 MHz, (1) first, the first filter means 4 is switched by the switching means 5.
Is switched to the third IF filter 4c, (2) the cutoff frequency of the second filter means 7 is set to 10 MHz, respectively, and (3) the oscillation frequency of the synthesizer 3 is 2000 MHz which is the center frequency of the input signal and IF. 200M
Hz, that is, 1800 MHz. By operating as described above, a signal having a center frequency of 2000 MHz and a bandwidth of 20 MHz is received. The frequency characteristic of the third IF filter 4c at this time is as shown in FIG. The frequency characteristics of the baseband filters 7a and 7b of the second filter means 7 are as shown in FIG.

When a signal having a center frequency of 1972.5 MHz is received during transmission at the minimum bandwidth of 5 MHz, (1) the switching means 5 controls the IF of the first filter means.
Switching to the filter 4a, (2) the cutoff frequency of the baseband filters 7a, 7b of the second filter means 7 is set to 2.5 MHz, and (3) the oscillation frequency of the synthesizer 3 is set to 1972.5 MHz which is the center frequency of the input signal. And I
The difference from 200 MHz which is F, ie, 1772.5M
Hz. By operating as described above, a signal having a center frequency of 1972.5 MHz and a bandwidth of 5 MHz is received. The frequency characteristic of the IF filter 4a at this time is shown in FIG.
3 (a). The frequency characteristics of the baseband filters 7a and 7b are as shown in FIG.

Although the description of other cases is omitted here, the first filter means 4 including the multistage IF filters 4aA to 4n and the baseband filters 7a and 7n
b) by switching the bandwidth of the second filter means 7 including b, and setting the oscillation frequency of the synthesizer 3 to a frequency at which the desired signal just coincides with the IF frequency, thereby receiving by the same configuration operation as described above. Are the same.

As described above, this type of conventional receiver is compatible with multi-rate transmission by changing the bandwidth of the IF filter and the baseband filter and the oscillation frequency of the synthesizer according to the control signal. .

In a receiver used for a mobile communication terminal or the like, the IF filter is usually constituted by a passive filter. A typical IF filter is a surface acoustic wave (SA).
W-Surface Acoustic Wave-) is used.
This type of filter is not suitable for miniaturization because the operating frequency is determined by its physical size. However, in the above-mentioned receiver, it is necessary to prepare IF filters for a plurality of transmission rates. For example, when the system uses four types of transmission bandwidths, it is necessary to prepare a total of four IF filters. As described above, if filters are provided in multiple stages, a plurality of filters are required, and the circuit configuration of the filter means cannot be integrated. Therefore, it becomes a serious obstacle to downsizing the equipment.

In a system in which a required bandwidth is selected from the minimum bandwidth and a bandwidth that is an integral multiple of the minimum bandwidth as described above, the frequency interval of the carrier of the received signal is 1/1 / the minimum bandwidth. Therefore, the synthesizer 6 needs to have a function of oscillating at a frequency interval of 最小 of the minimum bandwidth. For example, in the above example, the synthesizer 6 needs to have a function of oscillating at a frequency interval of 2.5 MHz, which is 1/2 of the narrowest bandwidth of 5 MHz. Generally, in a synthesizer, the smaller the oscillation frequency interval is with respect to the center frequency of the oscillation frequency range, the more the phase noise characteristic is deteriorated. Therefore, the synthesizer used for the receiver having the multi-rate transmission function, even when the bandwidth of the signal to be processed is the widest, will function in a state where the phase noise characteristic is deteriorated, and the reception characteristic is deteriorated. Had the problem of getting lost.

[0018]

SUMMARY OF THE INVENTION A receiver having a multi-rate transmission function according to the present invention has been made in order to eliminate the above problem, and the first filter means is constituted by one intermediate frequency filter. Accordingly, it is an object of the present invention to provide a receiver having a multi-rate transmission function which can be integrated and can simplify the configuration, and has a low manufacturing cost.

The oscillation frequency interval of the synthesizer is
Since it is necessary to set the interval when the bandwidth is narrowest, there is a problem that the phase noise characteristic is poor.
Accordingly, it is an object of the present invention to eliminate this problem and to provide a receiver having a multi-rate transmission function with a wide oscillation frequency interval of a synthesizer.

[0020]

According to a first aspect of the present invention, there is provided a receiver having a multi-rate transmission function for converting a received high-frequency signal into an intermediate frequency. First filter means connected to the output end of the means, quadrature demodulation means connected to the output end of the first filter means, and second filter means connected to the output end of the quadrature demodulator. A / D conversion means connected to the output terminal of the second filter means and having a multi-rate transmission function used in a wireless communication system for performing communication using signals of a plurality of bandwidths. In the above, the first filter means may reduce the bandwidth of each of the widest bandwidth signal and the narrowest bandwidth signal among the plurality of bandwidth signals supplied via the frequency conversion means. It is characterized in that it comprises a single band-pass filter capable of passing a band width corresponding to Kutomo sum.

According to a second aspect of the present invention, there is provided the receiver having the multi-rate transmission function according to the first aspect, wherein the frequency conversion means performs communication using a signal having the widest bandwidth. Functioning as a low-pass filter having a cut-off frequency wider than the bandwidth passed by the first filter means and including the frequency of the widest bandwidth signal, and communicating using the narrowest bandwidth signal Is performed, it functions as a band-pass filter having a bandwidth including the bandwidth for communication.

According to a third aspect of the present invention, there is provided the receiver having the multi-rate transmission function according to the first aspect, further comprising a synthesizer for generating a local signal having a predetermined frequency and supplying the local signal to the frequency converting means. The frequency interval of the local signal generated by the synthesizer is at least twice the bandwidth of the narrowest bandwidth signal.

According to a fourth aspect of the present invention, there is provided a receiver having a multi-rate transmission function, comprising: frequency conversion means for converting a received high-frequency signal into an intermediate frequency; and first filter means connected to an output terminal of the frequency conversion means. A quadrature demodulator connected to the output of the first filter; a second filter connected to the output of the quadrature demodulator; and an output connected to the output of the second filter. A / D conversion means having a multi-rate transmission function used in a wireless communication system for performing communication using signals of a plurality of bandwidths, wherein the first filter means comprises: Of the plurality of bandwidth signals supplied via the at least the bandwidth of the widest bandwidth signal as at least its pass bandwidth, and the bandwidth of the widest bandwidth signal Transmit frequency, is characterized by comprising the first one of the bandpass filter is controlled to be the center frequency of the pass bandwidth of the filter means.

A receiver having a multi-rate transmission function according to claim 5. The receiver according to claim 4,
When communication is performed using a signal having the widest bandwidth, the second filter means is constituted by a low-pass filter having a cutoff frequency set so as to include a half band of the bandwidth, When performing communication using a signal of a narrower bandwidth than the signal of the widest bandwidth,
It is characterized in that the second filter means is constituted by a band-pass filter that passes a bandwidth including the bandwidth.

A receiver having a multi-rate transmission function according to claim 6 is the receiver according to claim 1 or 4, wherein the second filter means is arranged in accordance with a bandwidth used for communication. It is characterized by being constituted by a low-pass filter whose cutoff frequency is selected.

A receiver having a multi-rate transmission function according to claim 7 is the receiver according to claim 6, wherein the second filter means includes a switched capacitor filter, and the cut-off frequency of the low-pass filter. Is determined by the cut-off frequency of the switched capacitor filter.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of a receiver having a multi-rate transmission function according to the present invention will be described in detail with reference to FIGS. First,
A receiver having a multi-rate transmission function according to the first embodiment will be described with reference to FIG. Note that, in a system that performs communication with a plurality of bandwidths to which the receiver according to the first embodiment is applied, the plurality of transmission bandwidths used is a minimum transmission bandwidth Δf1 and a bandwidth that is an integral multiple thereof. is there.

FIG. 1 is a block diagram showing a configuration of a receiver having a multi-rate transmission function according to a first embodiment of the present invention. In FIG. 1, a receiver includes a radio frequency signal or the like input from an antenna 1. Frequency converting means 2 for converting the frequency of the high-frequency signal, a synthesizer 3 for supplying a local oscillation signal of a predetermined frequency to the frequency converting means 2, and one intermediate frequency (hereinafter, IF-Intermediate Frequency-)
First filter means 4 constituted by filter 40
A quadrature demodulation means 6 comprising first and second quadrature demodulators 6a and 6b for demodulating an in-phase (I) component and a quadrature (Q) component of the output of the first filter means 4, respectively; First and second passing the base frequency of
Filter means 7 comprising baseband filters 7a and 7b, and A / D conversion means comprising first and second A / D converters 8a and 8b for converting analog signals of respective components into digital signals. 8, and a system band switching signal generation unit 7 that outputs a system band switching signal to the second filter unit 7. Components other than the configuration of the first filter means 4 are the same as those in FIG.
1 has the same functions as those of the components of the conventional receiver described using FIG.

Here, the center frequencies that can be taken by the band of the desired signal input via the antenna 1 are represented by f _RF1 and f _RF2.
,..., F _RFn (n is an integer and f _RF1 <f _RF2 <
... <f _RFn ). In this case, assuming that the narrowest transmission bandwidth is Δf1, the difference between adjacent center frequencies among the possible center frequencies of the desired signal input from the antenna is の of the narrowest transmission bandwidth Δf1. That is, "f
_{RF (i + 1) -fRFi} = .DELTA.f1 / 2 (i is an integer) ". Further, a predetermined intermediate frequency (IF) is defined as _fIF, and an oscillation frequency generated by the synthesizer 3 is defined as fIF.
_{LO1, f LO2, ..., f} LOm (m is an integer, f
_LO1 and _{<f LO2 <... <f LOm} ).

The parts having the functions characteristic of the first embodiment will be described below. First, the intermediate frequency (IF) filter 40 constituting the first filter means 4 is a band-pass filter having the sum of the widest bandwidth and the narrowest bandwidth among a plurality of transmission bandwidths. Further, the baseband filter 7 constituting the second filter means 7
A and 7b are the same as the conventional receiver in that the frequency characteristics are made variable by the control signal, but the characteristics of the conventional receiver are always low-pass characteristics by changing the cutoff frequency by the control signal. Was. In contrast, the first
As the baseband filter in the receiver according to the embodiment, a filter that can change a filter type such as a low-pass characteristic and a band-pass characteristic at the same time as the cutoff frequency is used.

Further, in the first embodiment of the present invention, by controlling the synthesizer 3 as follows, f _{LO (i + 1)} −f _LOi = 2Δf ₁ (i is an integer) and the oscillation frequency of the synthesizer 3 Is twice the narrowest transmission bandwidth.

As shown in FIG. 2, the lowest local frequency f _LO1 generated in the synthesizer 3 is represented by f _LO1 = f _RF1
−f _IF . At this time, when the bandwidth of the desired signal is the narrowest band, the oscillation frequency of the synthesizer 3 is such that the center frequency of the output desired signal of the frequency conversion unit 2 matches the predetermined IF frequency, or Controlled to offset by the frequency of the narrowest bandwidth,
Also, if the bandwidth of the desired signal is a wider band,
The oscillation frequency of the synthesizer 3 is controlled such that the center frequency of the output signal of the frequency conversion means 2 is offset from a predetermined IF frequency by a frequency which is 1/2 of the narrowest bandwidth Δf1 of the transmission bandwidth.

Next, the operation of the receiver having the multi-rate transmission function according to the second embodiment as a first example of the first embodiment of the present invention will be described.

The high-frequency signal f input to the frequency converter 1
The RF is converted into an IF signal by the frequency conversion unit 2 and output. The output IF signal of the frequency conversion unit 2 is input to the IF filter 40. At this time, the frequency conversion means 2
In the above, the input high-frequency signal f _RF is, as described above, the center frequency of the frequency-converted desired signal at the output of the frequency conversion means 2 shifted from the predetermined IF frequency f _IF by the local signal supplied from the synthesizer 6. Since the band of the IF filter 40 is set to have the sum of the widest bandwidth and the narrowest bandwidth,
The band is limited without removing the desired signal component. The IF signal band-limited by the IF filter 40 is input to the quadrature demodulation means 6 and converted into I-channel and Q-channel baseband signals by the first and second quadrature demodulators 6a and 6b and output. Output signals of the quadrature demodulators 6a and 6b are input to first and second baseband filters 7a and 7b. The baseband filters 7a and 7b can change the low-pass / band-pass characteristics and the cutoff frequency thereof by using the switching signal generated by the system band switching signal generating means 10.

The baseband signals band-limited by the baseband filters 7a and 7b are first and second A / Ds.
The signals are input to the converters 8a and 8b and converted into digital signals. Thereafter, the digital signal is demodulated by a demodulator (not shown). As described above, according to the configuration of the present invention, the frequency interval of the local signal oscillated by the synthesizer 6 is １ ／ of the narrowest transmission bandwidth in the related art, but is twice the narrowest transmission bandwidth. 4 times as large as Therefore, the phase noise characteristics of the synthesizer 3 can be reduced, and a receiver having a multi-rate transmission function with good reception characteristics can be realized.

Hereinafter, the receiver according to the second embodiment will be described with specific numbers. The system assumed here is the same as the system described in the conventional receiver. That is, the bandwidth of the system is 5 MHz, 10 MH
z, 20 MHz, and the carrier frequency is 2 GHz
It is assumed that the band and the system bandwidth are 60 MHz, and signals are allocated, for example, as shown in FIG.

Further, as shown in FIG.
_Is the lowest frequency of f _LO1 = f _RF3 −f _IF and f _{LO (i + 1)}
If −f _LOi = 2Δf 1 is selected, the interval becomes 10 MHz, and the oscillation frequency that can be output from the synthesizer 3 is 177.
7.5 MHz, 1787.5 MHz, 1979.5 MH
z, 1807.5 MHz, 1817.5 MHz, 182
It becomes 7.5 MHz.

The intermediate frequency (IF) is set to 200 MHz like the conventional receiver, but the IF filter 40 is different from the conventional 20 MHz, and the bandwidth is the maximum transmission bandwidth of the system of 20 MHz and the minimum transmission bandwidth of 5 MHz. A bandpass filter having a sum of 25 MHz and a center frequency of 200 MHz is used. The local oscillation frequency supplied to the quadrature demodulator 6 is set to, for example, the lower limit frequency of the pass band of the IF filter 40, that is, 187.5 MHz.

The operation when receiving a plurality of rates will be described. First, when a signal having a center frequency of 2000 MHz is received during transmission of the maximum bandwidth of 20 MHz, the synthesizer 3 is selected to output a local oscillation signal of 1797.5 MHz. As a result, the IF signal output from the frequency conversion means 2 is as shown in FIG. 4, and the baseband signal is as shown in FIG. Here, the characteristic of the baseband filter 4 is set to a center frequency of 15 MHz and a bandwidth of 10 MHz.
If a bandpass filter of MHz is used, the output of the baseband filter 4 is as shown in FIG. By operating in this manner, the center frequency is 2000 MHz and the bandwidth is 20 MHz.
The signal of z is received.

When the center frequency of the signal having the maximum bandwidth of 20 MHz is 1995 MHz, the IF signal output from the frequency converter 1 is as shown in FIG. 7, and the baseband signal is as shown in FIG. Therefore, if the characteristics of the baseband filters 7a and 7b are a bandpass filter having a center frequency of 10 MHz and a bandwidth of 20 MHz, the outputs of the baseband filters 7a and 7b are as shown in FIG. By operating in this manner, the center frequency 199
A signal of 5 MHz and a bandwidth of 20 MHz will be received.

Next, the case where the transmission bandwidth is 10 MHz will be described. For example, when a signal having a carrier wave of 2025 MHz is received, the frequency of the local oscillation signal transmitted from the synthesizer 3 is selected to be 1827.5 MHz.

As a result, the IF signal output from the frequency conversion means 2 is as shown in FIG. 10, and the baseband signal is as shown in FIG. Here, the baseband filters 7a and 7b in the second filter means 7
Is a band-pass filter with a center frequency of 10 MHz and a bandwidth of 10 MHz, the baseband filter 7a,
The output of 7b is as shown in FIG. By operating as described above, the center frequency is 2025 MHz and the bandwidth is 10 M
Hz signal is received.

In this case, as shown in FIG. 10, signals of other systems are mixed in the band of the IF filter 40.
When the power of the signal of the other system to be mixed in is extremely large, distortion may be generated in the baseband filter unit of the quadrature demodulation unit 6 or the second filter unit 7. Therefore, the local oscillation frequency of the synthesizer 3 is set to 1817. By setting the frequency to 0.5 MHz, signals from other systems can be prevented from being mixed as shown in FIG. At this time, although not shown, the characteristics of the baseband filters 7a and 7b may be a bandpass filter having a center frequency of 20 MHz and a bandwidth of 10 MHz. By operating as described above, a signal having a center frequency of 2025 MHz and a bandwidth of 10 MHz can be received.

Next, a case where a signal having a transmission bandwidth of 5 MHz is received will be described. For example, if the carrier is 1987.
When receiving a signal of 5 MHz, the local oscillation frequency at which the synthesizer 3 oscillates is 1787.5 MHz. In this case, since the local oscillation frequency is 1787.5 MHz, the carrier frequency of the desired signal is converted to 200 MHz. Since the local oscillation frequency applied to the quadrature demodulation means 6 is set at 187.5 MHz,
Has a center frequency of 12.5 MHz as shown in FIG.
At z, the signal has a bandwidth of 5 MHz. At this time, the baseband filters 7a and 7b of the second filter means 7 are bandpass filters having a center frequency of 12.5 MHz and a bandwidth of 5 MHz so that the system band switching signal generating means 1 can be used.
It is set by a switching signal supplied from 0. As described above, by operating, the center frequency is 1987.5 MHz,
A signal having a bandwidth of 5 MHz can be received.

As described above, the interval between the oscillating frequencies of the synthesizer 3 is the half of the conventional narrowest transmission bandwidth, but the maximum bandwidth of the IF filter is transmitted as in the present invention. By setting the bandwidth to be equal to or greater than the sum of the bandwidth and the minimum transmission bandwidth, the oscillation frequency interval of the synthesizer 3 can be expanded to twice the narrowest transmission bandwidth, and can be quadrupled compared to the conventional one. Therefore, the phase noise characteristics of the synthesizer 3 can be reduced, and a receiver having a multi-rate transmission function with good reception characteristics can be realized.

In the first and second embodiments, since the local oscillation frequency applied to the quadrature demodulation means 6 is fixed at 187.5 MHz, it is necessary to change the bandwidth and center frequency of the baseband filter in the band pass. There was,
As in the receiver according to the third embodiment shown in FIG. 15, the local oscillation frequency is set to 195 MHz, 197.5 MHz, 200 MHz, and 20 using the synthesizer 11 and the phase shifter 12.
By giving 2.5MHz and 2.5MHz interval,
As shown in FIGS. 16 (a), (b) and (c), the low-frequency components of the frequency-converted signal are cut by the output of the quadrature demodulation means 6 in correspondence with the respective transmission bandwidths of 20 MHz, 10 MHz and 5 MHz. A low-pass characteristic may be provided, and a band-pass characteristic may not be provided.

In the synthesizer 11, the same as the conventional 2.5
Although it is necessary to oscillate at a frequency interval of 2 MHz, the synthesizer 11 operates at a frequency of 2.
Oscillation may be performed at intervals of 5 MHz, so that phase noise characteristics can be reduced, and a receiver having a multi-rate transmission function with good reception characteristics can be realized.

At this time, the base band filter is 20M
A low-pass filter having a cutoff frequency of about 1/2 of each transmission bandwidth of Hz, 10 MHz and 5 MHz may be used. This low-pass filter includes, for example, an aliasing distortion removal filter 13 and a switched capacitor filter (SCF) 14 as shown in FIG. 17, so that a clock frequency applied to the SCF 14 is selected by a system band switching signal. , And the cutoff frequency can be easily selected. Note that the aliasing removal filter 1
The cutoff frequency of 3 may be set in accordance with the maximum transmission bandwidth (in this case, 10 MHz), or may be switched by a system band switching signal.

Next, a fourth embodiment as a second specific example of the first embodiment will be described. In this specific example, the center frequency when the bandwidth is 20 MHz is 1980 MHz 2000 MHz 2020 MHz as shown in FIG. 18A, and when the bandwidth is narrower than that, the center frequency is 20 MHz.
As shown in FIG. 18 (b), the system allocated in such a way as to be sandwiched in the middle of the case of FIG. As shown in FIG. 18C, when the bandwidth is 5 MHz, the center frequency is 1972.5 MHz 1977.5 MHz 1982.5 MHz 1987.5 MHz 1992.5 MHz 1997.5 MHz 2002.5 MHz 2007.5 MHz 2012.5 MHz 2017. Assume a system assigned 5 MHz 2022.5 MHz 2027.5 MHz. In this case,
The bandwidth of the IF filter 2 is equal to or larger than the maximum transmission bandwidth, for example, 20 MHz, the local oscillation frequency applied to the quadrature demodulator 3 is 200 MHz, and the frequencies that can be output from the synthesizer 6 are 1780 MHz, 1800 MHz, 1820 MHz.
MHz, and the oscillation frequency of the synthesizer 6 is controlled so as to coincide with the center frequency of the widest channel containing the desired signal.

The operation of the fourth embodiment will be specifically described below. If you want to receive the widest bandwidth signal,
The frequency conversion unit and the quadrature demodulation unit perform frequency conversion so that the center frequency of the desired signal becomes 0 Hz, and receive the baseband signal by quadrature demodulation.
In this case, the operation is the same as that of the conventional receiver. When the band is narrower than that, the frequency conversion is performed using a local oscillation frequency such that the center frequency of the channel having the widest bandwidth including the desired band is converted to 0 Hz by the frequency conversion means and the quadrature demodulation means. In addition, unnecessary signal components are cut and demodulated by setting the characteristics of the baseband filter to band-pass characteristics that allow only a desired signal to pass.

First, when a signal having a center frequency of 1980 MHz is received during transmission of the maximum bandwidth of 20 MHz, the characteristic of the baseband filter 7 is a low-pass filter having a cut-off frequency of 10 MHz, and the oscillation frequency of the synthesizer 3 is determined by the input signal. 1980 MH which is the center frequency
The difference between z and the 200 MHz IF, ie, 1780
MHz. At this time, the frequency characteristics of the baseband filters 7a and 7b of the second filter means 7 are as shown in FIG.
It is the same as that shown in FIG.

Next, a case where the transmission bandwidth is 10 MHz will be described. For example, when the carrier receives a signal of 1985 MHz, the synthesizer 3 performs the same operation as in the case of 178 MHz.
0 MHz. This is a big difference from the conventional receiver. In this case, since the local oscillation frequency is 1780 MHz, the carrier frequency of the desired signal is frequency-converted to 205 MHz, so that the output of the quadrature demodulator 6 has a center frequency of 5 MHz.
z is a bandpass signal having a bandwidth of 10 MHz. At this time, the baseband filters 7a and 7b
It is set by a system band switching signal so as to be a bandpass filter having a bandwidth of 10 MHz and a bandwidth of 10 MHz.

Next, a case where the transmission bandwidth is 5 MHz will be described. For example, when the carrier receives a signal of 1987.5 MHz, the synthesizer 3 operates in the same manner as described above.
80 MHz. In this case, the local oscillation frequency is 178
Since it is 0 MHz, the carrier frequency of the desired signal is 207.5 M
Since the frequency is converted to Hz, the output of the orthogonal demodulation means 6 is a bandpass signal having a center frequency of 7.5 MHz and a bandwidth of 5 MHz. At this time, the baseband filter 4 is set by the system band switching signal 7 so as to be a bandpass filter having a center frequency of 7.5 MHz and a bandwidth of 5 MHz.

As described above, more generally, when a signal having the widest bandwidth is received, the frequency conversion is performed so that the center frequency becomes 0 Hz. When the bandwidth is narrower than that, the frequency conversion is performed. The frequency conversion is performed using a local oscillation frequency such that the center frequency of the channel having the widest bandwidth that includes the band is converted to 0 Hz, and the characteristics of the baseband filter are changed to band-pass characteristics that allow only the desired signal to pass. Thus, unnecessary signal components are cut and demodulated. As a result, in a receiver that receives signals of a plurality of bandwidths, it is possible to increase the oscillation frequency interval of the synthesizer without increasing the number of IF filters. Therefore, the phase noise characteristics of the synthesizer 3 can be reduced, and a receiver having a multi-rate transmission function with good reception characteristics can be realized.

Next, a fifth embodiment of the present invention will be described with reference to the drawings. FIG. 19 is a block diagram showing a configuration of a receiver having a multi-rate transmission function according to the fifth embodiment of the present invention. In FIG. 19, a receiver includes a first frequency converter 2 as frequency conversion means, a synthesizer 3,
Filter means 4 comprising two IF filters 40
, A second frequency converter 15, a second filter means 7 including a baseband filter 70, an A / D conversion means 8, an output terminal 9, and a system band switching signal to the baseband filter 70. And a system band switching signal generating means 10.

The characteristic configuration of the fifth embodiment is that the quadrature demodulation means 6 in the first embodiment is replaced by a second frequency converter 15 in the fifth embodiment. The operation of the fifth embodiment is also similar to that of the fourth embodiment. The difference is that in the fourth embodiment, when a signal having the widest bandwidth is received, the center frequency of the desired signal is set to 0 at the output stage of the quadrature demodulation means 63.
In contrast to the case where the local oscillation frequency is controlled so as to be in Hz, in the fifth embodiment, when a signal having the widest bandwidth is received, the lower limit frequency of the desired signal is set to the second frequency converter 15. In this case, the local oscillation frequency is controlled so as to be 0 Hz at the output stage. Generally, the receiver according to the first embodiment of the present invention is referred to as a direct conversion system, whereas the receiver according to the fifth embodiment is referred to as a low IF system.

When receiving the signal with the widest bandwidth,
Frequency conversion is performed so that the lower limit frequency becomes 0 Hz, and the baseband signal is received by demodulation. If the band is narrower than that, the frequency conversion is performed using a local oscillation frequency that is converted to the lower limit frequency 0 Hz of the widest bandwidth channel including the desired band, and the baseband filter Unnecessary signal components are cut off and demodulated by setting the characteristic to a band-pass characteristic that allows only a desired signal to pass.

Next, the operation of the receiver according to the fifth embodiment at the time of receiving a plurality of rates when the same system as that of the fourth embodiment is assumed as the system of the fifth embodiment will be described. I do.

First, when a signal having a center frequency of 1980 MHz is received during transmission of the maximum bandwidth of 20 MHz (the lower limit frequency of the signal is 1970 MHz and the upper limit frequency is 1990 MHz), (1) characteristics of the baseband filter 7 Is a low-pass filter having a cutoff frequency of 20 MHz. (2) The oscillation frequency of the synthesizer 3 is set to 1970 MHz, which is the lower limit frequency of the input signal, and IF
, Ie, 1770 MHz. (In the fourth embodiment, the local oscillation frequency is determined so that the center frequency of the desired signal is 200 MHz. However, in the present embodiment, the lower limit frequency of the desired signal,
That is, in this case, 1970 MHz is IF 200M
The local oscillation frequency is determined to be Hz. 2) By operating as described above, a signal having a center frequency of 1980 MHz and a bandwidth of 20 MHz is received. The frequency characteristic of the baseband filter 7 at this time is as shown in FIG.

Next, the case where the transmission bandwidth is 10 MHz will be described. For example, if the carrier frequency is 1985 MHz
Is received, the local oscillation signal output from the synthesizer 3 has a frequency of 1770 MHz in the same manner as described above. In this case, the local oscillation frequency is 17
70 MHz, so the carrier frequency of the desired signal is 215 MH
z, the output of the second frequency converter 15 is not a baseband signal, but has a center frequency of 15M.
A signal having a bandwidth of 10 MHz at Hz is similar to the second specific example of the first embodiment. At this time, the baseband filter 7 has a center frequency of 15 MHz and a bandwidth of 10 MHz.
Is set by the system band switching signal generating means 10 so as to make the band pass filter. FIG. 20B shows the frequency characteristics of the baseband filter 7 at this time. By operating in this manner, a signal having a center frequency of 1985 MHz and a bandwidth of 10 MHz can be received without changing the characteristics of the IF filter 4 and without changing the oscillation frequency of the synthesizer 3.

Next, a case where the transmission bandwidth is 5 MHz will be described. For example, if the frequency of the carrier is 1987.
When the signal of z is received, the local oscillation frequency of the synthesizer is set to 1770 MHz as described above. In this case, since the local oscillation frequency is 1770 MHz, the carrier frequency of the desired signal is frequency-converted to 217.5 MHz. Therefore, the output of the second frequency converter 15 is not a baseband signal, but the center frequency is 17.5 MHz and the bandwidth is Is a signal of 5 MHz, similar to the second specific example of the first embodiment. At this time, the baseband filter 7 has the center frequency 1
The 7.5 MHz bandwidth is set by the system band switching signal generating means 10 so as to be a band pass filter having a 5 MHz bandwidth. FIG. 20C shows the frequency characteristics of the baseband filter 7 at this time. By operating in this manner, a signal having a center frequency of 1987.5 MHz and a bandwidth of 5 MHz can be received without changing the characteristics of the IF filter 4 and without changing the oscillation frequency of the synthesizer 3.

As described above, when a signal having the widest bandwidth is received, frequency conversion is performed so that the lower limit frequency is 0 Hz, and the baseband signal is received by demodulation. If the band is narrower than that, the frequency conversion is performed using a local oscillation frequency such that the lower limit frequency of the channel having the widest bandwidth including the desired band is converted to 0 Hz, and the baseband filter is used. Unnecessary signal components are cut off and demodulated by setting the characteristic to a band-pass characteristic that allows only a desired signal to pass.

By operating as described above, a signal of a plurality of bandwidths can be configured in a receiver so that the oscillation frequency of the synthesizer can be reduced without increasing the number of IF filters. .

In each of the above embodiments, the characteristics of the IF filter 40 and the baseband filter 70 show a configuration in which a margin is not taken into consideration for the system bandwidth. In an actual design, the bandwidth of the filter is often slightly wider than the bandwidth of the desired signal. However, even in such a case, by using the configuration method of the present invention, the number of IF filters can be reduced and the effect of using a synthesizer having high phase noise characteristics is the same.

[0065]

As described above in detail, according to the receiver having the multi-rate transmission function according to the present invention, in particular, the intermediate frequency filter constituting the first filter means is provided with one intermediate frequency filter.
In addition, a simple and simple configuration can be achieved, and the manufacturing cost can be reduced by integrating the circuit configuration of the first filter means into an integrated circuit.

Also, since the interval between the oscillation frequencies of the synthesizer can be widened, not only the number of intermediate frequency filters can be reduced, but also the high phase noise characteristic can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiver having a multi-rate transmission function according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing characteristics of first filter means of the receiver having the multi-rate transmission function according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing frequency characteristics of a high-frequency signal and a local oscillation signal of the receiver according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an output of a frequency converter when receiving a signal having a bandwidth of 20 MHz according to the second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an output of a quadrature demodulator 3 when receiving a signal having a bandwidth of 20 MHz in the second embodiment.

FIG. 6 is an explanatory diagram showing an output of a baseband filter 4 when receiving a signal having a bandwidth of 20 MHz in the second embodiment.

FIG. 7 shows different center frequencies 20 in the second embodiment.
FIG. 3 is an explanatory diagram showing an output of a frequency converter when a signal having a bandwidth of MHz is received.

FIG. 8 shows 20 different center frequencies in the second embodiment.
FIG. 4 is an explanatory diagram showing an output of a quadrature demodulation unit when a signal having a bandwidth of MHz is received.

FIG. 9 is a diagram showing another example of the second embodiment in which the center frequencies are different.
FIG. 4 is an explanatory diagram showing an output of a second filter unit when a signal having a bandwidth of MHz is received.

FIG. 10 is an explanatory diagram showing an output of a frequency converter when receiving a signal having a bandwidth of 10 MHz in the second embodiment.

FIG. 11 is an explanatory diagram showing an output of a quadrature demodulator when receiving a signal having a bandwidth of 10 MHz in the second embodiment.

FIG. 12 is an explanatory diagram illustrating an output of a second filter unit when receiving a signal having a bandwidth of 10 MHz in the second embodiment.

FIG. 13 is an explanatory diagram showing an output of a frequency conversion unit when a signal having a bandwidth of 10 MHz is received when the oscillation frequency of the synthesizer is changed in the second embodiment.

FIG. 14 is an explanatory diagram showing an output of a frequency conversion unit when receiving a signal having a bandwidth of 5 MHz in the second embodiment.

FIG. 15 is a block diagram showing a configuration of a receiver having a multi-rate transmission function according to a third embodiment of the present invention.

FIG. 16 is an explanatory diagram showing an output of a second filter unit of the receiver according to the third embodiment.

FIG. 17 is a block diagram showing a configuration of a baseband filter constituting second filter means of a receiver having a multi-rate transmission function according to a fourth embodiment of the present invention.

FIG. 18 is an explanatory diagram showing a frequency arrangement of the receiver according to the fourth embodiment.

FIG. 19 is a block diagram showing a configuration of a receiver having a multi-rate transmission function according to a fifth embodiment of the present invention.

FIG. 20 is an explanatory diagram showing an output of a baseband filter of the receiver according to the fifth embodiment.

FIG. 21 is a block diagram showing a configuration of a conventional receiver having a multi-rate transmission function.

FIG. 22 is an explanatory diagram showing an example of frequency allocation in a conventional receiver.

FIG. 23 is an explanatory diagram showing respective frequency characteristics of (a) a first IF filter, (b) a second IF filter, and (c) a third IF filter in the first filter means of the conventional receiver. .

FIG. 24 is an explanatory diagram showing the characteristics of the second filter means when the conventional receiver receives (a) a signal having a bandwidth of 20 MHz and (b) a signal having a bandwidth of 5 MHz.

[Explanation of symbols]

 Reference Signs List 2 frequency converter 3 synthesizer 4 first filter 40 intermediate frequency (IF) filter 6 quadrature demodulator 7 second filter 7a first baseband filter 7b second baseband filter 70 baseband filter 8A / D conversion means 10 System band switching signal generation means 11 Synthesizer 12 90-degree phase shifter 13 Loopback removal filter 14 Switched capacitor filter (SCF)

Claims (7)

[Claims] 1. A frequency conversion means for converting a received high-frequency signal into an intermediate frequency, a first filter means connected to an output terminal of the frequency conversion means, and a first filter means connected to an output terminal of the first filter means. A quadrature demodulator, a second filter connected to the output of the quadrature demodulator, and an A / D converter connected to the output of the second filter. In a receiver having a multi-rate transmission function used in a wireless communication system that performs communication using a signal of a bandwidth, the first filter means includes a plurality of bandwidths supplied through the frequency conversion means. One band pass filter capable of passing a bandwidth corresponding to at least the sum of the respective bandwidths of the widest bandwidth signal and the narrowest bandwidth signal is provided. And a receiver having a multi-rate transmission function. 2. The communication apparatus according to claim 1, wherein when performing communication using the signal having the widest bandwidth, the frequency conversion means is wider than the bandwidth passed by the first filter means and has a higher bandwidth than the first filter means. Function as a low-pass filter having a cut-off frequency including the frequency of the signal, and when performing communication using the narrowest bandwidth signal, function as a band-pass filter having a bandwidth including the communication bandwidth. The receiver having a multi-rate transmission function according to claim 1. 3. A synthesizer for generating a local signal having a predetermined frequency and supplying the local signal to the frequency conversion means,
2. The receiver having a multi-rate transmission function according to claim 1, wherein an interval between the frequencies of the local signal generated by the synthesizer is at least twice the bandwidth of the narrowest bandwidth signal. . 4. A frequency conversion means for converting a received high-frequency signal to an intermediate frequency, a first filter means connected to an output terminal of the frequency conversion means, and a first filter means connected to an output terminal of the first filter means. A quadrature demodulator, a second filter connected to the output of the quadrature demodulator, and an A / D converter connected to the output of the second filter. In a receiver having a multi-rate transmission function used in a wireless communication system that performs communication using a signal of a bandwidth, the first filter means includes a plurality of bandwidths supplied through the frequency conversion means. The signal having the widest bandwidth among the signals has at least the passband thereof, and the carrier frequency of the widest bandwidth signal is the passband of the first filter means. A receiver having a multi-rate transmission function, comprising one band-pass filter controlled to have a center frequency of a width. 5. When performing communication using the signal having the widest bandwidth, the second filter means has a cut-off frequency set so as to include a half band of the bandwidth. When communication is performed using a signal having a bandwidth narrower than the signal having the widest bandwidth, the second filter means is configured by a band-pass filter that passes a bandwidth including the bandwidth. The receiver having a multi-rate transmission function according to claim 4, wherein the receiver is configured. 6. The apparatus according to claim 1, wherein said second filter means comprises a low-pass filter whose cut-off frequency is selected according to a bandwidth used in communication. Receiver having a multi-rate transmission function. 7. The apparatus according to claim 6, wherein said second filter means includes a switched capacitor filter, and a cutoff frequency of said low pass filter is determined by a cutoff frequency of said switched capacitor filter. Receiver having a multi-rate transmission function.