JPH1117575A - Broad band radio frequency receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broad band radio frequency receiver with a small size and low power consumption by selecting a sampling speed of an A/D converter while keeping the broad band characteristic of the receiver without deteriorating the characteristic of a received signal. SOLUTION: Pluralities of intermediate band-pass filters 5a-5d of an integrated wide band filter IWF 5 filter an intermediate frequency signal at a different pass band and provide an output. A level detection section 6 detects each output level of the intermediate band pass filters 5a-5d and stores it and outputs the detected output level to a DSP 10. A changeover device 7 selects an output of the level detection section 6 under the control of the DSP 10 and an A/D converter 9 converts an analog signal outputted from the level detection section 6 into a digital signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadband radio frequency receiver used in a digital portable telephone or the like, and more particularly, to realize a channel separation and a modulation / demodulation process using a digital line such as a DSP by taking in a signal in a wide band. In such a case, the present invention relates to a small-sized and low-power-consumption wide-band radio frequency receiver capable of widening the band of the receiver without deteriorating the performance of the received signal.

[0002]

2. Description of the Related Art In recent years, the use of multimedia has been advanced in various fields, and there has been an increasing demand for high-speed, large-capacity transmission of mobile communication as an information terminal in the multimedia age. As a result, it is necessary for the wireless device to widen the band. In recent years, with the development of digital circuit technology, examples of realizing functions realized by analog circuits by digital circuits are increasing, and in the field of communication devices such as digital mobile phones, they are also called software radios. Techniques for realizing most of the wireless functions by software have been proposed. The feature of this technology is that all the signal processing functions, such as channel separation and modulation / demodulation that were conventionally performed in analog, are processed by software after A / D conversion, giving the radio equipment more flexibility. is there. For this reason, A / D converters, DSPs, and the like are required to have high frequency and wide band characteristics, and at the same time, it is necessary to widen the band of the radio section.

FIG. 4 is a diagram showing a conventional example of the configuration of a broadband radio frequency receiver. The broadband receiver shown in FIG.
In the digital mobile phone, an example is shown in which a part of the function of the wireless device is realized by a DSP. In FIG. 4, a broadband radio frequency receiver includes an antenna 1 for inputting a high frequency signal.
A high-frequency band-pass filter 2 for removing out-of-band unnecessary waves of a high-frequency signal; a high-frequency low-noise amplifier 3 for amplifying the high-frequency signal with low noise; and a fixed-frequency signal for frequency-converting the high-frequency signal in a wide band. , A mixer 4 that mixes the output of the high-frequency low-noise amplifier 3 with a fixed frequency signal and converts it to an intermediate frequency signal, and removes out-of-band unwanted waves of the frequency-converted intermediate frequency signal. An intermediate frequency bandpass filter 13, an intermediate frequency amplifier 8 with an AGC function for amplifying the intermediate frequency signal, an A / D converter 9 for converting an analog signal into a digital signal,
It comprises a DSP 10 that digitally performs signal processing functions such as channel separation and modulation / demodulation processing. The high-frequency band-pass filter 2, the high-frequency low-noise amplifier 3, the local oscillator 1
2, the mixer 4, the intermediate frequency band-pass filter 13, and the intermediate frequency amplifier 8 constitute a frequency conversion unit 14. The frequency conversion unit 14 is configured by an analog circuit and performs signal processing in an analog manner.

[0004] Next, the operation of the wideband radio frequency receiver having the above configuration will be described. FIG. 5 is a diagram modeling a spectrum of an input / output signal 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 the high-frequency signal is filtered by a high-frequency band-pass filter 2 into a required band (bandwidth W
Unnecessary waves outside _RF ) are removed. Here, in the high-frequency band-pass filter 2, the dynamic range required to satisfy wireless performance is, for example, 80d.
Let W _RF be the bandwidth over which B or more is obtained. The high-frequency signal passed through the high-frequency band-pass filter 2 (center frequency f _RF ,
The bandwidth W _RF ) is amplified by the 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 the frequency conversion is set to f _IF . Next, the intermediate frequency band filter 13 causes the local oscillator 1
Unwanted waves outside the required band including the transmission frequency of No. 2 are removed. Here, in the intermediate frequency band-pass filter 13, a dynamic range required to satisfy wireless performance, for example, a bandwidth for obtaining 80 dB or more is W _IF , and a maximum frequency at this time is 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 is digitally converted by the A / D converter 9. At this time, assuming that the sampling speed required for the A / D converter 9 is f _S , the sampling speed f _S needs to satisfy the following expression (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 1
955) Subsequently, the signal digitally converted by the A / D converter 9 is input to the DSP 10, where signal processing such as channel separation and modulation / demodulation processing is performed digitally.

FIG. 6 is a diagram showing 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 relatively higher than near the baseband. In this case, assuming that the sampling speed 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 Converter
s and Their Applicati-ons in Radio Receivers ", IEEE
Communication Megazine, Vol.33, No.5, pp39-45, May 1
955)

[0006]

However, in the prior art, in any of the above formulas (1) and (2), the configuration of the wideband radio frequency receiver actually tries to widen the bandwidth. Then, since the requirements for the high-frequency characteristics and the wide-band characteristics of the various analog devices, the A / D converter 9, and the DSP 10 become very large for the reason described below, the circuit scale becomes large and the power consumption increases. was there. As shown in FIG. 5, in the wideband radio frequency receiver, a high-frequency signal is directly frequency-converted to near the baseband, so that a negative return signal enters the intermediate frequency band and becomes noise, adversely affecting radio performance. And degrades the performance. Therefore, 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 given by the following equation (4).
It looks like f _S > 2f _IF + W _IF --- (4) That is, as can be seen from the above equation (4), if an attempt is made to widen the band of the receiver, f _IF becomes large, so that A / D
The sampling rate f _S of the converter 9 must be high. As a result, an expensive A / D converter is required, and the cost of the device increases. Also, if the intermediate frequency _IIF is made closer to the baseband, it is difficult to realize an intermediate frequency bandpass filter, and even if it can be realized, the insertion loss and the shape will increase in order to secure wideband characteristics. Further, the out-of-band attenuation characteristic becomes slow, the W _IF increases to secure the same dynamic range as described above, the load on the A / D converter increases, and the out-of-band noise becomes more susceptible. . For example, in the case of a surface acoustic wave filter that is actually known to have good attenuation characteristics, when the center frequency is 100 MHZ and the pass bandwidth WS is 20 MHZ, f _MAX is about 120 MHZ, and the A / D conversion is performed. Must be sampled at a sampling rate of 240 Msps (MSamples / sec) or higher. The problem of having to increase the sampling rate of the A / D converter is that even if the configuration of the wideband radio frequency receiver is configured by, for example, a double conversion system or by using the sampling method shown in FIG. This is a problem that also occurs. The present invention has been made in view of the above problems, without deteriorating the characteristics of the received signal,
An object of the present invention is to provide a small-sized and low-power-consumption wideband radio frequency receiver by reducing the sampling rate of an A / D converter while maintaining the wideband characteristics of the receiver.

[0007]

According to a first aspect of the present invention, there is provided a wide-band radio frequency receiver for converting a frequency of an input high-frequency signal into a wide band to generate an intermediate frequency signal. And a filter unit having a plurality of filters each of which filters the intermediate frequency signal with a different pass band and outputs the same. The output level of each of the plurality of filters is detected and stored.
A level detector for outputting to an SP, a switch for selecting and switching the output of the level detector under the control of the DSP, and an A / D converter for converting an analog signal output from the level detector to a digital signal And a DSP for controlling signal processing such as channel separation and modulation / demodulation and switching of the switch. According to the broadband wireless receiver according to claim 1, the plurality of filters of the filter unit filter and output the intermediate frequency signal with different passbands, and the level detection unit detects the output levels of the plurality of filters. Each 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 is output from the level detector. Since it is configured to convert analog signals to digital signals, the output levels of multiple filters in the filter section are detected, the target communication band is detected, and the output from the level detection section is adjusted according to the system operation mode. To select and output. As a result, the sampling rate of the A / D converter can be reduced while maintaining the wideband characteristics of the receiver, so that a small-sized and low-power-consumption wideband wireless receiver can be provided.

[0008] The broadband radio frequency receiver according to claim 2 is
2. The wideband radio frequency receiver according to claim 1, wherein each of the plurality of filters includes a SAW filter having a different resonance point, and can simultaneously handle multi-frequency signals. According to the wideband radio frequency receiver according to the second aspect, since the configuration uses a SAW filter as a filter, in addition to the effect of the first aspect, the intermediate frequency signal is filtered and output in different passbands. It is possible to configure the filter to be inexpensively. According to a third aspect of the present invention, there is provided a wideband radio frequency receiver according to the first or second aspect, wherein the frequency band for performing frequency analysis of a wideband signal is obtained.
An FFT processing unit having an FT function is provided inside or outside the DSP. According to the wideband radio frequency receiver according to claim 3, the DSP includes an FFT processing unit having an FFT function for performing frequency analysis of a wideband signal.
Since the configuration is provided inside or outside, it is possible to monitor the radio wave environment and the like in addition to the effects of the invention described in claim 1 or 2.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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 a 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 denoted by the same reference numerals. In FIG. 1, a wide-band radio frequency receiver includes an antenna 1 for inputting a high-frequency signal, a high-frequency bandpass filter 2 for removing out-of-band unnecessary waves of the high-frequency signal, and a high-frequency low-frequency amplifier for amplifying the high-frequency signal with low noise. Noise amplification unit 3
A local oscillator 12 for generating a fixed frequency signal for frequency-converting the high-frequency signal in a wide band, a mixer 4 for mixing the output of the high-frequency low-noise amplifier 3 with the fixed-frequency signal and converting the output to an intermediate-frequency signal, A plurality of intermediate frequency band-pass filters 5a to 5d are provided, and each intermediate frequency band-pass filter 5a to 5d removes an unnecessary out-of-band unnecessary wave of the intermediate frequency signal after frequency conversion.
lter) 5 and the output levels of the intermediate frequency band-pass filters 5a to 5d of the IWF 5 are stored.
Level detector 6 which outputs this output level with respect to 0
A switch 7 for switching the output of the level detector 6 in accordance with the control from the DSP 10, an intermediate frequency amplifier 8 with an AGC function for amplifying the intermediate frequency signal from the switch 7, and a digital signal for converting the amplified analog signal to a digital signal. A / D to convert to
A converter 9; a DSP 10 for digitally performing signal processing functions such as channel separation and modulation / demodulation processing;
An FFT processing unit 11 that performs FFT processing on the D-converted digital signal and outputs processed data to the DSP 10 to enable viewing of a wireless environment or the like is provided. As the intermediate frequency bandpass filters 5a to 5d, for example,
SAW filters each having a different resonance point can be used. FIG. 2 is a diagram illustrating frequency characteristics of the intermediate frequency bandpass filters 5a and 5b of the IWF 5. As shown in FIG. 2, each of the intermediate frequency band-pass filters 5a and 5b has a pass band width W2 and a center frequency f2 at a center frequency f1.
, The pass bandwidth W2, the center frequency f3, the pass bandwidth W3,
The intermediate frequency f4 has a frequency characteristic of a pass bandwidth W4.

Next, the operation of the broadband radio frequency receiver having the above configuration will be described. FIG. 3 is a diagram showing input / output signals in the case where a wideband signal is processed by the IWF 5 in a spectrum. First, a high-frequency signal having a center frequency f _RF and a bandwidth Ws is input from the antenna 1, and the high-frequency signal from the high-frequency signal is removed by a high-frequency band-pass filter 2 outside unnecessary bands (bandwidth W _RF ). . Here, in the high-frequency band-pass filter 2, a bandwidth that is a dynamic range required to satisfy wireless performance, and obtains, for example, 80 dB or more is defined as W _RF . The high-frequency signal (center frequency f _RF , bandwidth W
_RF ) is amplified by the high-frequency low-frequency noise amplifier 3 and then output from the local oscillator 12 that outputs a fixed frequency signal of a single frequency, and the mixer 4 keeps a wide band near the baseband or up to several tens of MHZ bands. Frequency conversion is performed. Here, the center frequency of the intermediate frequency signal after the frequency conversion is _defined as fIF.

Next, the frequency-converted signal is input to each of the intermediate frequency band-pass filters 5a to 5d of the IWF 5. Here, the bandwidth Ws of the high frequency signal and the pass bandwidths W1 to W1 of the intermediate frequency bandpass filters 5a to 5d are used.
W4 is given by the following equation (5). Ws = W1 + W2 + W3 + W4- (5) Then, the intermediate frequency signals are filtered by the intermediate frequency band-pass filters 5a to 5d to remove unnecessary waves outside the required band including the transmission frequency of the local oscillator 12, and each of the bandwidths W1 to W1. The band is divided into W4. Here, in each of the intermediate frequency band-pass filters 5a to 5d of the IWF 5, a bandwidth that is a dynamic range required to satisfy wireless performance, for example, 80 dB or more is defined as W _IF .

The level detector 6 measures the output level of each output of the IWF 5, and detects each of the intermediate frequency band-pass filters 5a to 5a.
The output level of 5d is stored and the measured output level is output to the DSP 10. The switch 7 is a DSP 10
, The output of the level detector 6 is switched and output to the intermediate frequency amplifier 8. The intermediate frequency signal selected by the switch 7 is amplified by an intermediate frequency amplifier, and is then digitally converted by an A / D converter 9. Here, the sampling speed 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 digitally performs signal processing such as channel separation and modulation processing. In addition, the DSP 10 controls the switch 7 so that the IWF
5 can be taken into the DSP 10. For example, the bandwidth Ws of the signal input to the IWF 5 is set to 20 MHZ, and the pass bandwidths W1 to W4 of the respective frequency bandpass filters are set to 5 MHZ, and a surface acoustic wave filter which is known to have actually good attenuation characteristics is considered. And W _IF is about 15 MHZ. As a result, noise and the like outside the passband can be sufficiently suppressed, and good reception performance can be ensured even during wideband reception. Further, since the pass band width of one intermediate frequency band pass filter is 5 MHZ, it is possible to transfer data at 5 to 6 Mbps. In this case, from the above equation (2), A / D
The converter 9 only needs a sampling rate of about 30 Msps. This results in a sampling rate that is about a quarter of the prior art. Furthermore, since signals can be easily captured in a wide band, it is possible to provide a function such as monitoring of the radio wave environment, such as the FFT 11, as described in the present embodiment. It is possible to do.

As described above, in the present embodiment, a plurality of intermediate bandpass filters 5a to 5a of the IWF 5 are provided.
5d filters the intermediate frequency signals with different passbands and outputs the same, and the level detector 6 detects and stores the output levels of the intermediate bandpass filters 5a to 5d, respectively, and outputs the detected output levels. Output to the DSP 10, the switch 7 selects and switches the output of the level detector 6 under the control of the DSP 10, and the A / D converter 9 converts the analog signal output from the level detector 6 into a digital signal. Therefore, the level detector 6 detects the output levels of the filters of the intermediate bandpass filters 5a to 5d to detect a target communication band, and the switch 7 outputs the output from the level detector 6. Can be selected according to the operation mode of the system and output to the A / D converter 9. as a result,
Since the sampling rate of the A / D converter can be reduced while maintaining the wideband characteristics of the receiver, it is possible to provide a small-sized and low-power-consumption broadband wireless receiver. In addition, compared to the conventional method, it is possible to easily increase the bandwidth of the receiver, and also to significantly reduce the loss to digital devices such as A / D converters and DSPs without causing performance degradation. A broadband radio frequency receiver can be configured. In the present embodiment, D
Separate FFT processing unit 11 to reduce load on SP10
However, the function can be provided by the DSP 10. Further, in the present embodiment, an example is shown in which the intermediate frequency bandpass filter of the IWF 5 is configured by a SAW filter, but the present invention is not limited to this, and another filter may be used. Also, an example has been shown in which the IWF 5 divides the signal into four bands, but the number of divisions is not limited to this.

[0014]

According to the broadband radio receiver according to the first aspect, the plurality of filters of the filter section filter and output the intermediate frequency signal with different passbands, and the level detection section outputs the plurality of intermediate frequency signals. Each of the output levels 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 converts an analog signal output from the level detector into a digital signal. By detecting the level of the output of the filter, the target communication band can be detected, and the output from the level detector can be selected and output according to the operation mode of the system. As a result, the sampling rate of the A / D converter can be reduced while maintaining the wideband characteristics of the receiver, so that a small-sized and low-power-consumption wideband wireless receiver can be provided. According to the wideband radio frequency receiver according to the second aspect, since the configuration uses a SAW filter as a filter, in addition to the effect of the first aspect, the intermediate frequency signal is filtered and output in different passbands. It is possible to configure the filter to be inexpensively. According to the wideband radio frequency receiver according to the third aspect, an FFT processing unit having an FFT function for performing frequency analysis of a wideband signal is provided inside or outside the DSP. Or, in addition to the effects of the invention described in 2, the monitoring of the radio wave environment and the like can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a broadband radio frequency receiver according to the present invention.

FIG. 2 is a view showing frequency characteristics of each intermediate frequency band-pass filter of the IWF of FIG. 1;

FIG. 3 is a diagram illustrating input / output signals in the case of processing a wideband signal with the IWF of FIG. 1 in a spectrum.

FIG. 4 is a diagram showing a configuration of a conventional broadband radio frequency receiver.

FIG. 5 is a diagram showing a first example of modeling the spectrum of an input / output signal in the wideband radio frequency receiver of FIG. 4;

FIG. 6 is a diagram showing a second example in which the spectrum of the input / output signal in the wideband radio frequency receiver in FIG. 4 is modeled.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 antenna 2 high-frequency band-pass filter 3 high-frequency low-noise amplifier 4 mixer 5 IWF 5 a to 5 b local oscillator 6 level detector 7 switch 8 intermediate frequency amplifier 9 A / D converter 10 DSP 11 FFT processing unit

Claims (3)

[Claims] 1. A frequency conversion unit for converting an input high-frequency signal into a wide band to generate an intermediate frequency signal, and a plurality of filters for filtering and outputting the intermediate frequency signal with different pass bands. A filter unit, a level detection unit that detects and stores the output levels of the plurality of filters, and outputs the detected output levels to a DSP, and selects an output of the level detection unit under the control of the DSP. A switching unit for switching, an A / D converter for converting an analog signal output from the level detection unit to a digital signal, and the DSP for controlling signal processing such as channel separation and modulation / demodulation and switching of the switching unit. A broadband radio frequency receiver comprising: 2. The apparatus according to claim 1, wherein the plurality of filters are SAW filters each having a different resonance point, and are capable of simultaneously handling multi-frequency signals.
A broadband radio frequency receiver as described. 3. An F for performing frequency analysis of a wideband signal.
3. The wideband radio frequency receiver according to claim 1, wherein an FFT processing unit having an FT function is provided inside or outside the DSP.