JP3850107B2 - Broadband radio frequency receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a broadband radio frequency receiver used in a digital cellular phone or the like, and more specifically, in a case where a signal is captured in a wide band and channel separation or modulation / demodulation processing is realized by a digital line such as a DSP. The present invention relates to a wide-band radio frequency receiver that is small in size and low in power consumption, with a wider band of the receiver without causing signal performance degradation.
[0002]
[Prior art]
In recent years, the development of multimedia has progressed in various fields, and the demand for high-speed and large-capacity transmission of mobile communication is increasing as an information terminal in the multimedia era. As a result, it is necessary to increase the bandwidth of the radio. In recent years, with the development of digital circuit technology, there are an increasing number of examples where functions realized by analog circuits are realized by digital circuits, and in the field of communication equipment such as digital mobile phones, they are also called software radios. Technologies that realize most of the wireless functions with software have been proposed. The feature of this technology is that the signal processing functions such as channel separation and modulation / demodulation, which have been conventionally performed in an analog manner, are all processed by software after A / D conversion. is there.
For this reason, A / D converters, DSPs, and the like are required to have high frequency and broadband characteristics, and at the same time, it is necessary to increase the bandwidth of the radio unit.
[0003]
FIG. 4 is a diagram illustrating a conventional example of the configuration of a wideband radio frequency receiver. The broadband receiver shown in FIG. 4 shows an example in which a part of the function of the wireless device is realized by a DSP in a digital cellular phone.
In FIG. 4, a broadband radio frequency receiver includes an antenna 1 for inputting a high frequency signal, a high frequency bandpass filter 2 for removing an out-of-band unnecessary wave of the high frequency signal, and a high frequency low noise for amplifying the high frequency signal with low noise. An amplifier 3, a local oscillator 12 for transmitting a fixed frequency signal for frequency conversion of the high frequency signal in a wide band, and a mixer 4 for mixing the output of the high frequency low noise amplifier 3 with the fixed frequency signal and converting it to an intermediate frequency signal An intermediate frequency band-pass filter 13 for removing unnecessary waves outside the band of the intermediate frequency signal after frequency conversion, an intermediate frequency amplifier 8 with an AGC function for amplifying the intermediate frequency signal, and converting an analog signal into a digital signal It comprises an A / D converter 9 and a DSP 10 that digitally performs signal processing functions such as channel separation and modulation / demodulation processing.
The high-frequency bandpass filter 2, the high-frequency low-noise amplifier 3, the local oscillator 12, the mixer 4, the intermediate frequency bandpass filter 13, and the intermediate frequency amplifier 8 constitute a frequency conversion unit 14, It consists of analog circuits and performs analog signal processing.
[0004]
Next, the operation of the broadband radio frequency receiver having the above configuration will be described.
FIG. 5 is a diagram modeling the spectrum of input / output signals in the wideband radio frequency receiver of FIG.
First, a high-frequency signal having a center frequency f _RF and a bandwidth Ws is input from the antenna 1, and unnecessary waves outside the required band (bandwidth W _RF ) are removed from the high-frequency signal by the high-frequency bandpass filter 2. . Here, in the high-frequency bandpass filter 2, a required dynamic range for satisfying the radio performance, for example, a bandwidth for obtaining 80 dB or more is set as W _RF .
A high-frequency signal (center frequency f _RF , bandwidth W _RF ) that has passed through the high-frequency bandpass filter 2 is amplified by a high-frequency low-frequency noise amplifier 3. Next, the output of the high-frequency low-noise amplifier 3 is mixed by the mixer 4 with a single-frequency fixed frequency signal transmitted from the local oscillator 12 and frequency-converted to output an intermediate frequency signal. Here, the center frequency of the center frequency signal of the intermediate frequency signal after frequency conversion is set to f _IF .
Next, the intermediate frequency band filter 13 removes unnecessary waves outside the desired band including the transmission frequency of the local transmitter 12. Here, in the intermediate frequency band-pass filter 13, the dynamic range required for satisfying the radio performance, for example, the bandwidth for obtaining 80 dB or more is set as W _IF , and the maximum frequency at this time is set as f _MAX .
The intermediate frequency signal having the center frequency f _IF and the bandwidth W _IF is amplified by the intermediate frequency amplifier 8 and then digitally converted by the A / D converter 9. At this time, if the sampling rate required for the A / D converter 9 is f _S , the sampling rate f _S needs to satisfy the following equation (1).
f _S > 2 × f _MAX −−− (1)
(Jeffery A. Wepman, "Analog-to-Digital Converters and Their Applicati-ons in Radio Receivers", IEEE Communication Megazine, Vol.33, No.5, pp39-45, May 1955)
Subsequently, the signal digitally converted by the A / D converter 9 is input to the DSP 10, and signal processing such as channel separation and modulation / demodulation processing is performed digitally.
[0005]
FIG. 6 is a diagram illustrating another example in which the spectrum of the input / output signal in the wideband radio frequency receiver of FIG. 4 is modeled.
As shown in FIG. 6, sampling may be performed in a frequency band that is relatively higher than the vicinity of the baseband. In this case, if the sampling rate required for the A / D converter 9 is f _S , the following equation (2) must be satisfied.
f _S > 2 × W _IF −−− (2)
(Jeffery A. Wepman, "Analog-to-Digital Converters and Their Applicati-ons in Radio Receivers", IEEE Communication Megazine, Vol.33, No.5, pp39-45, May 1955)
[0006]
[Problems to be solved by the invention]
However, in the prior art, in either case of the above formulas (1) and (2), in the configuration of the wideband radio frequency receiver, if it is actually intended to increase the bandwidth, the reason will be described in detail below. Since the requirements for the high-frequency characteristics and the broadband characteristics of various analog devices, the A / D converter 9 and the DSP 10 become very large, there is a problem that the circuit scale increases and the power consumption increases.
As shown in FIG. 5 above, in the broadband radio frequency receiver, since the high frequency signal is directly frequency-converted to the vicinity of the baseband, the negative aliasing signal enters the intermediate frequency band, which becomes noise and adversely affects the radio performance. And cause performance degradation. For this reason, the maximum frequency f _MAX needs to satisfy the condition of the following expression (3).
f _MAX > f _IF + W _IF / 2 --- (3)
From the above equations (1) and (3), the relationship between the sampling rate f _S of the A / D converter and the analog circuit is expressed by the following equation (4).
f _S > 2f _IF + W _IF −−− (4)
That is, as can be seen from the above equation (4), when trying to increase the bandwidth of the receiver, f _IF increases, so the sampling rate f _S of the A / D converter 9 must be increased. As a result, an expensive A / D converter is required and the cost of the apparatus is increased. Further, when the intermediate frequency I _IF is made closer to the baseband, it is difficult to realize an intermediate frequency bandpass filter, and even if it can be realized, insertion loss and shape increase in order to ensure wideband characteristics. Further, the out-of-band attenuation characteristic becomes slow, and the W _IF increases to secure the same dynamic range as described above, which increases the load on the A / D converter and is easily affected by out-of-band noise. .
For example, in the case of a surface acoustic wave filter known to have good attenuation characteristics, f _MAX is about 120 MHZ when the center frequency is 100 MHZ and the pass bandwidth WS is 20 MHZ. The sampler must sample at a sampling rate of 240 Msps (M Samples / sec) or higher.
The problem that the sampling rate of the A / D converter has to be increased is that even if the configuration of the wideband radio frequency receiver is configured by, for example, a double conversion method or the sampling method shown in FIG. 6 is used. This is a problem that occurs in the same way.
The present invention has been made in view of the above-mentioned problems, and by reducing the sampling rate of the A / D converter while maintaining the broadband characteristics of the receiver without degrading the characteristics of the received signal, An object is to provide a broadband radio frequency receiver with low power consumption.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a wideband radio frequency receiver according to claim 1 has a frequency converter that converts an input high frequency signal in a wideband to generate an intermediate frequency signal, and has different center frequencies. A filter unit that includes a plurality of bandpass filters that form a predetermined passband width in a state where the passbands overlap with each other, and that filters and outputs the intermediate frequency signal with the passband widths of the plurality of bandpass filters And detecting and storing each of the output levels of the plurality of bandpass filters, selecting the output of the level detector by controlling the DSP, and a level detector for outputting the detected output level to the DSP a switch for switching the a / D converter for converting the analog signals selected by the switch to a digital signal, channel separation and demodulation, etc. signals It said DSP for controlling the switching of physical and the switch, and configured to include a.
According to wideband radio receiver according to claim 1, a plurality of band-pass filter of the filter unit, and outputs the filtered passband width, each of the intermediate frequency signals are different, the level detecting unit, the plurality of bandpass Each output level of the filter is detected and stored, and the detected output level is output to the DSP. The switch selects and switches the output of the level detector under the control of the DSP, and the A / D converter switches the switch. Since the analog signal selected by the method is converted into a digital signal, the output level of the plurality of bandpass filters of the filter unit is detected, the target communication band is detected, and the output from the level detection unit is output. You can select and output according to the system operation mode. As a result, the sampling rate of the A / D converter can be made lower than before while maintaining the broadband characteristics of the receiver, so that it is possible to provide a small-sized and low power consumption broadband wireless receiver.
[0008]
A wideband radio frequency receiver according to a second aspect of the present invention is the wideband radio frequency receiver according to the first aspect, wherein the plurality of bandpass filters are SAW filters each having a different resonance point, and simultaneously transmit a multifrequency signal. It was possible to handle.
According to the wideband radio frequency receiver of the second aspect, since the SAW filter is used as the bandpass filter, in addition to the effect of the first aspect, the intermediate frequency signal is filtered with a different passband width . Thus, the output filter can be configured at low cost.
The wideband radio frequency receiver according to claim 3 is the wideband radio frequency receiver according to claim 1 or 2, wherein an FFT processing unit having an FFT function for performing frequency analysis of a wideband signal is provided in the DSP, or A configuration provided outside.
According to the wideband radio frequency receiver of the third aspect, the FFT processing unit having the FFT function for performing frequency analysis of the wideband signal is provided inside or outside the DSP. Alternatively, in addition to the effects of the invention described in 2, it is possible to monitor the radio wave environment.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a broadband radio frequency receiver according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a broadband radio frequency receiver according to the present invention. In FIG. 1, parts having the same functions as those of the broadband radio frequency receiver shown in FIG. 4 are given the same reference numerals. In FIG. 1, a broadband radio frequency receiver includes an antenna 1 for inputting a high-frequency signal, a high-frequency bandpass filter 2 for removing unnecessary waves outside the band of the high-frequency signal, and a high-frequency low-frequency amplifier that amplifies the high-frequency signal with low noise. The noise amplifier 3, the local transmitter 12 for generating a fixed frequency signal for frequency conversion of the high frequency signal in a wide band, and the output of the high frequency low noise amplifier 3 are mixed with the fixed frequency signal and converted to an intermediate frequency signal. An IWF (Integrated Wideband Filter) 5 that includes a mixer 4 and a plurality of intermediate frequency bandpass filters 5a to 5d, and removes unnecessary out-of-band waves of the intermediate frequency signal after frequency conversion by each of the intermediate frequency bandpass filters 5a to 5d. , The output level of each of the intermediate frequency band pass filters 5a to 5d of the IWF 5 is stored, and the output level is output to the DSP 10. A level detector 6; a switch 7 for switching the output of the level detector 6 in accordance with control from the DSP 10; an intermediate frequency amplifier 8 with an AGC function for amplifying the intermediate frequency signal from the switch 7; A / D converter 9 for converting a signal into a digital signal, DSP 10 for digitally performing signal processing functions such as channel separation and modulation / demodulation processing, and the digital signal after A / D conversion are processed by FFT processing It is configured by an FFT processing unit 11 or the like that outputs data to the DSP 10 and enables a circular view of a wireless environment or the like. As the intermediate frequency bandpass filters 5a to 5d, for example, SAW filters having different resonance points can be used. FIG. 2 is a diagram showing the frequency characteristics of the intermediate frequency bandpass filters 5a to 5b of the IWF 5. Each intermediate-frequency band-pass filter 5a~5b, as shown in FIG. 2, the passband width W 1 at a center frequency f1, a center frequency f2 in the pass band width W2, the center frequency f3 in the pass band width W3, passes at the center frequency f4 Each has frequency characteristics of the bandwidth W4.
[0010]
Next, the operation of the broadband radio frequency receiver having the above configuration will be described.
FIG. 3 is a spectrum diagram showing input / output signals when a wideband signal is processed by the IWF 5.
First, a high frequency signal having a center frequency f _RF and a bandwidth Ws is input from the antenna 1, and unnecessary waves outside the required band (bandwidth W _RF ) are removed from the high frequency signal by the high frequency band pass filter 2. . Here, in the high-frequency bandpass filter 2, a required dynamic range for satisfying the radio performance, for example, a bandwidth for obtaining 80 dB or more is set as W _RF .
The high-frequency signal (center frequency f _RF , bandwidth W _RF ) that has passed through the high-frequency bandpass filter 2 is amplified by the high-frequency low-frequency noise amplifier 3 and then a local oscillator 12 that outputs a single frequency fixed frequency signal. The signal is converted to the vicinity of the base band or to several tens of MHZ band by the signal from the mixer and the mixer 4 while maintaining a wide band. Here, the center frequency of the intermediate frequency signal after frequency conversion is set to f _IF .
[0011]
Next, the frequency-converted signal is input to the intermediate frequency bandpass filters 5a to 5d of the IWF 5, respectively.
Here, the bandwidth Ws of the high-frequency signal and the pass bandwidths W1 to W4 of the intermediate frequency bandpass filters 5a to 5d are expressed by the following equation (5).
Ws = W1 + W2 + W3 + W4 --- (5)
Then, the intermediate frequency signal is divided into bandwidths W1 to W4 by removing unnecessary waves outside the required band including the transmission frequency of the local transmitter 12 by the intermediate frequency bandpass filters 5a to 5d.
Here, in each of the intermediate frequency band-pass filters 5a to 5d of the IWF 5, a dynamic range required for satisfying the radio performance, for example, a bandwidth for obtaining 80 dB or more is set as W _IF .
[0012]
The level detector 6 measures the output level of each output of the IWF 5 and stores the output level of each of the intermediate frequency bandpass filters 5a to 5d, and outputs the measured output level to the DSP 10. The switch 7 switches the output of the level detector 6 and outputs it to the intermediate frequency amplifier 8 under the control of the DSP 10. The intermediate frequency signal selected by the switch 7 is amplified by an intermediate frequency amplifier and then digitally converted by an A / D converter 9.
Here, the sampling rate required for the A / D converter 9 requires the condition of the above equation (2).
The digitally converted signal is input to the DSP 10, and signal processing such as channel separation and modulation processing is performed digitally. Further, the DSP 10 can take in all the intermediate frequency signals output from the IWF 5 to the DSP 10 by controlling the switch 7.
For example, the bandwidth Ws of a signal input to the IWF 5 is 20 MHZ, the pass bandwidths W1 to W4 of each frequency band pass filter are 5 MHZ, respectively, and a surface acoustic wave filter known to have actually good attenuation characteristics is considered. W _IF is about 15 MHZ.
As a result, noise outside the passband can be sufficiently suppressed, and good reception performance can be ensured even during wideband reception. Moreover, since the pass band width of one intermediate frequency band pass filter is 5 MHz, transfer of 5 to 6 Mbps is possible. In this case, from the above equation (2), the A / D converter 9 needs a sampling rate of about 30 Msps. This is about a quarter of the sampling rate of the prior art.
Furthermore, since it is easy to capture signals in a wide band, a new system can be operated, such as the ability to have a radio wave environment, such as FFT 11, as shown in this embodiment. Can be done.
[0013]
As described above, in the present embodiment, the plurality of intermediate bandpass filters 5a to 5d of the IWF 5 filter and output intermediate frequency signals in different pass bands, and the level detection unit 6 Each of the output levels of the bandpass filters 5a to 5d is detected and stored, and the detected output level is output to the DSP 10, and the switch 7 selects and switches the output of the level detector 6 under the control of the DSP 10. Since the / D converter 9 is configured to convert the analog signal output from the level detection unit 6 into a digital signal, the level detection unit 6 detects the output level of each of the intermediate bandpass filters 5a to 5d. Then, the target communication band is detected, and the switching unit 7 selects the output from the level detection unit 6 according to the system operation mode and outputs it to the A / D converter 9. It can be. As a result, the sampling rate of the A / D converter can be made lower than before while maintaining the broadband characteristics of the receiver, so that it is possible to provide a small-sized and low power consumption broadband wireless receiver.
In addition, it is possible to easily increase the bandwidth of the receiver as compared with the conventional method, and it is possible to significantly reduce the negative effect on digital devices such as A / D converters and DSPs without causing performance degradation. A broadband radio frequency receiver can be constructed.
In the present embodiment, the FFT processing unit 11 is separately provided to reduce the load on the DSP 10, but the DSP 10 can also have the function.
In the present embodiment, the intermediate frequency bandpass filter of the IWF 5 is configured with a SAW filter. However, the present invention is not limited to this, and other filters may be used. Moreover, although the example divided | segmented into four bands by IWF5 was shown, the division | segmentation number is not limited to this.
[0014]
【The invention's effect】
According to wideband radio receiver according to claim 1, a plurality of band-pass filter of the filter unit, and outputs the filtered passband width, each of the intermediate frequency signals are different, the level detecting unit, the plurality of bandpass Each output level of the filter is detected and stored, and the detected output level is output to the DSP. The switch selects and switches the output of the level detector under the control of the DSP, and the A / D converter switches the switch. Since the analog signal selected by the method is converted into a digital signal, the output level of the plurality of bandpass filters of the filter unit is detected, the target communication band is detected, and the output from the level detection unit is output. You can select and output according to the system operation mode. As a result, the sampling rate of the A / D converter can be made lower than before while maintaining the broadband characteristics of the receiver, so that it is possible to provide a small-sized and low power consumption broadband wireless receiver.
According to the wideband radio frequency receiver of the second aspect, since the SAW filter is used as the bandpass filter, in addition to the effect of the first aspect, the intermediate frequency signal is filtered with a different passband width . Thus, the output filter can be configured at low cost.
According to the wideband radio frequency receiver of the third aspect, the FFT processing unit having the FFT function for performing frequency analysis of the wideband signal is provided inside or outside the DSP. Alternatively, in addition to the effects of the invention described in 2, it is possible to monitor the radio wave environment.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a wideband radio frequency receiver according to the present invention.
FIG. 2 is a diagram illustrating frequency characteristics of each intermediate frequency bandpass filter of the IWF in FIG. 1;
3 is a diagram showing spectrums of input / output signals when a wideband signal is processed by the IWF of FIG. 1. FIG. 4 is a diagram showing a configuration of a conventional broadband radio frequency receiver.
5 is a diagram showing a first example in which a spectrum of an input / output signal in the broadband radio frequency receiver of FIG. 4 is modeled.
6 is a diagram showing a second example in which the spectrum of an input / output signal in the wideband radio frequency receiver of FIG. 4 is modeled.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Antenna 2 High frequency band pass filter 3 High frequency low noise amplification part 4 Mixer 5 IWF
5a to 5b Local transmitter 6 Level detector 7 Switch 8 Intermediate frequency amplifier 9 A / D converter 10 DSP
11 FFT processor

Claims (3)

A frequency converter that generates an intermediate frequency signal by converting the frequency of the input high frequency signal in a wide band;
A plurality of band-pass filters each having a different center frequency and forming a predetermined pass-band width in a state in which the respective pass-bands overlap each other, and the intermediate frequency signal is represented by the pass-band width of each of the plurality of band-pass filters. A filter unit for filtering and outputting;
A level detection unit that detects and stores the output levels of the plurality of bandpass filters, and outputs the detected output level to the DSP;
A switch for selecting and switching the output of the level detection unit under the control of the DSP;
An A / D converter that converts an analog signal selected by the switch into a digital signal;
A broadband radio frequency receiver comprising signal processing such as channel separation and modulation / demodulation and the DSP for controlling switching of the switch. 2. The broadband radio frequency receiver according to claim 1, wherein each of the plurality of band-pass filters includes SAW filters having different resonance points, and can handle a multi-frequency signal simultaneously.   3. The broadband radio frequency receiver according to claim 1, wherein an FFT processing unit having an FFT function for performing frequency analysis of a broadband signal is provided inside or outside the DSP.

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