JP2000165278A - Broadband receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a broadband receiver with a small size and low power consumption regardless of a simple configuration by relaxing requirements of configuration circuits different from a conventional broadband receiver that has required an A/D converter with an excellent high frequency characteristic because of a requirement of a very fast sampling speed resulting in requiring a high cost, a large size and much power consumption for a portable telephone set. SOLUTION: A pattern memory section 9 controls a local oscillator 5 so as to oscillate local frequency that each intermediate frequency signal is coincident with center frequency of an IF filer 6. The each intermediate frequency signal is obtained by dividing a received signal into a plurality of bands each having a prescribed width band and mixing with each center frequency of each band. The obtained intermediate frequency signal is A/D-converted, a DSP 8 applies FFT processing to the result so as to monitor a radio wave environment and a frequency including a desired channel is selected from the result. Then the pattern memory section 9 controls the local oscillator 5 so as to oscillate a frequency at which only the selected frequency band can be received and receives.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver such as a digital portable telephone, and more particularly to a small-sized and low-power-consumption broadband receiver having a simple structure.

[0002]

2. Description of the Related Art In recent years, multimedia has been promoted in various fields, and there is an increasing demand for high-speed, large-capacity transmission of mobile communication as an information terminal in the multimedia age. Correspondingly, the need for wireless devices to increase the bandwidth has increased. In recent years, with the development of digital circuit technology, more and more functions that have been realized by analog circuits have been realized by digital circuits. In the field of communication devices such as digital mobile phones, software-defined radios (Joe Mitola , "The Software Radio Architectur
e ", IEEE Communication Magazine, Vol. 33, No. 5, pp26-3
8, May 1995), a technology for realizing most of the wireless functions by software has been proposed. The feature of this technology is that after converting a received analog signal to a digital signal, the signal processing functions such as channel separation and modulation / demodulation that were performed analogously by hardware are processed by software, so that the frequency band and modulation method are The function of the wireless device can be flexibly changed according to the situation.

FIG. 4 shows a digital portable telephone or the like.
A part of the function of the wireless device is changed to DSP (Digital Signal Process).
FIG. 7 is a schematic configuration diagram illustrating an example of a conventional wideband receiver realized in or). In the figure, the broadband receiver includes an antenna 61 and an RF for removing unnecessary out-of-band waves of a high-frequency signal.
A band-pass filter 62, an RF amplifier 63 for amplifying the high-frequency signal with low noise, a mixer 64 for converting the high-frequency signal into an intermediate frequency signal while keeping a wide band, a local oscillator 65 for outputting a fixed oscillation frequency, IF band-pass filter 66 for removing out-of-band unnecessary waves of a signal, and A / D converter 6 for converting an analog signal to a digital signal
7, a DSP 68 that digitally performs signal processing functions such as channel separation and modulation / demodulation processing, and a control unit 69 that performs signal processing of demodulated voice or data and controls the operation of the entire receiver.

[0004] The receiving operation of the above receiver is as follows.
The RF bandpass filter 62 removes unnecessary waves outside the band from the high-frequency reception signal of the center frequency fRF received by the antenna 61 of the receiver. Here, when the allocated frequency band is Ws, an RF band-pass filter having a center frequency fRF and a bandwidth WRF to obtain a dynamic range (for example, 80 dB) required to satisfy reception performance such as adjacent channel interference characteristics. Assume that 62 is needed. The output of the RF band-pass filter 62 is amplified by the RF amplifier 63, and then mixed with a local signal from the local oscillator 65 that outputs a fixed oscillation frequency in the mixer 64. Is frequency-converted.

[0005] The intermediate frequency signal output from the mixer 64 has a center frequency fIF and a bandwidth WI for obtaining a dynamic range (80 dB) required to satisfy the reception performance.
Unnecessary waves other than the required band are removed by the IF bandpass filter 66 of F. The output of the IF bandpass filter 66 is converted into a digital signal by the A / D converter 67. The intermediate frequency signal converted into a digital signal is digitally subjected to signal processing such as channel separation and demodulation processing in the DSP 68, and is output from the control unit 69 as voice or data.

The intermediate frequency signal and A /
The relationship between the sampling rates of the D converter will be described in detail.
FIG. 5 is a diagram modeling a frequency spectrum of a high-frequency input signal of the receiver and an intermediate frequency signal after frequency conversion.
(A) shows the case where the frequency has been converted to the vicinity of the baseband, and (b) shows the case where the frequency has been converted to a relatively higher frequency than the baseband. As shown in FIG.
The high-frequency signal from the F band-pass filter 62 is frequency-converted by the mixer 64 to an intermediate frequency near the baseband, and furthermore, the IF band-pass filter 66 removes unnecessary waves from the center frequency fIF and the intermediate band of the bandwidth WIF. The frequency signal is sampled in the A / D converter 67 by the Nyquist sampling method, and is converted into a digital signal. At this time, the sampling speed fS required of the A / D converter 67 is determined by setting the maximum frequency of the intermediate frequency signal to f.
It is known that a condition of fS> 2 × fMAX (1) is required when MAX is set (Jeffery A.
Wepman: "Analog-to-Digital Converters and Their Ap
replications in Radio Receivers ", IEEE Communication
Magazine, Vol. 33, No. 5, pp 39-45, May 1995). Also, the following equation is obtained from FIG. fMAX = fIF + WIF / 2 (2) From equations (1) and (2), fS> 2 × fIF + WIF (3)

As shown in FIG. 5B, a high-frequency signal from an RF band-pass filter 62 having a center frequency fRF and a bandwidth WRF is frequency-converted by a mixer 64 to an intermediate frequency relatively higher than a baseband. , An IF band-pass filter 66, a center frequency fIF from which unnecessary waves have been removed, and a broadband intermediate frequency signal having a bandwidth WIF are converted to an A / D converter 67.
Is sampled by a band-pass sampling method and converted into a digital signal. At this time, A
It is known that the sampling rate fS required of the / D converter 67 needs to satisfy the following condition: fS> 2 × WIF (4) (Jeffery A.
Wepman: "Analog-to-Digital Converters and Their Ap
replications in Radio Receivers ", IEEE Communication
Magazine, Vol. 33, No. 5, pp 39-45, May 1995). Equation (4)
As can be seen from this, the sampling rate in this case depends mainly on the bandwidth of the signal input to the A / D converter,
It is hardly affected by the maximum frequency of the input signal.
Therefore, according to the bandpass sampling method, the sampling speed in the A / D converter can be reduced as compared with the Nyquist method.

The signal digitized by the A / D converter 67 is channel-separated by the DSP 68. DSP6
8 monitors a communication environment for each channel based on the signal separated in the standby state, selects a channel having an excellent communication environment at the start of communication, demodulates a signal of the channel, and controls the control unit. Output to 69. The control unit 69
The signal input from the DSP 68 is output as a voice or a data string. Further, the control unit 69 controls the local oscillator 65 such that a predetermined intermediate frequency signal is obtained from the mixer 64 when the reception frequency band is changed due to the change of the service to be used.

[0009]

However, as shown in equations (3) and (4), the A / D converter 6
The sampling speed fS of 7 is determined by the characteristic values fIF and WIF of the signal passing through the IF bandpass filter 66. In the configuration of FIG. 4, for example, the bandwidth Ws = 20 MHz
In the case of configuring a wideband receiver, a surface acoustic wave (SAW) which can obtain an excellent attenuation characteristic by using an IF bandpass filter is used.
ic Wave) filter, WIF = 60 MHz, fIF = 3
The filter has a characteristic value of about 40 MHz. At this time, the sampling speed by the Nyquist sampling method is fS = 740 Msps (M sample per s
econd) Also, in the band-pass sampling method that can reduce the sampling speed, fS
= 120 Msps, and in any case, to construct an A / D converter having a dynamic range of 80 dB and a large sampling speed, it is very expensive, large and consumes a large amount of current at present. For this reason, there is a problem that it is difficult to configure a wideband receiver for mobile communication, especially for a small mobile phone. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a small-sized, low-power-consumption broadband receiver with a simple configuration by reducing the required performance of constituent circuits. Aim.

[0010]

In order to solve the above-mentioned problems, the present invention provides a wideband receiver which implements a part of radio functions such as channel separation and modulation / demodulation by digital signal processing means. It is divided into a plurality of bands having a predetermined bandwidth, each band is sequentially frequency-converted so as to have the same intermediate frequency, and the obtained intermediate frequency signal is digitally converted and subjected to FFT processing by the digital signal processing means In particular, the radio wave environment is monitored, and a band including a desired channel is selected and received from the divided bands based on the monitoring result.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a broadband receiver according to the present invention. As shown in FIG. 1, the receiver includes an antenna 1 for receiving a high-frequency signal, an RF bandpass filter 2 for removing an out-of-band unnecessary wave of the high-frequency reception signal, and an RF amplifier for amplifying the high-frequency input signal with low noise. 3, a mixer 4 for converting a high-frequency signal into an intermediate-frequency signal, a local oscillator 5 for outputting a frequency-variable local signal to the mixer 4,
An IF band-pass filter 6 for removing unnecessary waves outside the band of the intermediate frequency signal, an A / D converter 7 for converting an analog signal into a digital signal, and signal processing functions such as channel separation, modulation / demodulation processing, and FFT of an input signal. A digital DSP 8; a frequency pattern memory 9 for outputting a control signal for switching the oscillation frequency of the local oscillator 5 in a certain pattern; and processing of demodulated voice or data and control of the operation of the entire receiver. And a control unit 10 for performing the control.

The operation of the broadband receiver having the above-described configuration will be described with reference to the schematic diagram of FIG.
The description will be made as a wideband receiver capable of receiving the frequency band of the wireless system of the band 1.9 GHz. The antenna 1, the RF bandpass filter 2, and the RF amplifier 3 of the receiver receive and amplify all the 400 MHz, 800 MHz, and 1.9 GHz bands. The received signal amplified by the RF amplifier 3 is frequency-converted in the mixer 4 by mixing with the local signal from the local oscillator 5, and is output to, for example, an IF bandpass filter 6 having a center frequency of 70 MHz and a pass bandwidth of 5 MHz. .

In this receiver, the entire frequency band of each of the 400 MHz band, 800 MHz band, and 1.9 GHz band received by the antenna 1 is continuously divided into small bands of 5 MHz width, and the 400 MHz frequency band is divided. The center frequencies of the respective small bands are denoted by f401, f402,.
f40n, the center frequencies of the respective small bands in the 800 MHz frequency band are f801, f802,.
The center frequency of each small band of the 5 GHz frequency band is f
151, f152,... F15n. In the local oscillator 5, an intermediate frequency obtained by mixing each of the center frequencies with the oscillation frequency of the local oscillator 5 is a center frequency of the IF bandpass filter 6.
An oscillation frequency that matches the MHz is output based on the control of the frequency pattern memory unit 9.

Next, the function of the frequency pattern memory section 9 will be described based on the example of the reception frequency pattern shown in FIG.
FIG. 3A shows that the receiver is 1.9 band from the 400 MHz band.
All frequency bands of GHz band are 400 MHz at time interval Tp.
It is a pattern example for sequentially scanning and receiving from the lowest frequency band of the band to the highest frequency band of the 1.9 GHz band. In order to receive signals in this pattern, the frequency pattern memory unit 9 sends a signal to the local oscillator 5 at every time interval Tp.
The frequencies f401,... F40n, f801,.
The control signal is output so as to output a local oscillation signal from which an intermediate frequency signal of 70 MHz is obtained by mixing with 80n, f151,... F15n. Upon receiving this control signal, the oscillator 5 outputs a predetermined oscillation frequency at each time interval Tp. As a result of the above operation, the entire frequency band can be received from the lowest frequency band to the highest frequency band with a bandwidth of 5 MHz for each time interval Tp. It becomes possible to monitor.

Further, by changing a control signal output from the frequency pattern memory unit 9 to the local oscillator 5 as a control signal, for example, only a specific radio system band or each radio system is alternately received. Any reception pattern can be configured, such as sequentially receiving small bands in the wireless system. FIG. 2B is a diagram showing an example of a pattern in which a 5 MHz small band of the 800 MHz frequency band is received in an arbitrary order. Here, it goes without saying that the control interval to the local oscillator 5 should be appropriately set in accordance with the time division timing predetermined in the wireless system.

The intermediate frequency signal from the mixer 4 is filtered by an IF band-pass filter 6 to remove unnecessary out-of-band signals, and is input to an A / D converter 7 where it is converted into a digital signal. As described above, the intermediate frequency signal input to the IF bandpass filter 6 has a center frequency of 70 MHz and a pass bandwidth of 5 MHz.
Is constant. A filter having a characteristic that the center frequency fIF is 70 MHz and the required pass bandwidth Ws is 5 MHz,
For example, if the filter is constituted by a surface acoustic wave filter, the bandwidth WIF in which a dynamic range of 80 dB or more can be obtained is 15 MHz.
With this filter, out-of-band noise and the like can be sufficiently suppressed, and good reception performance can be ensured even during wideband reception. As a result, the sampling speed in the A / D converter is required to be about 30 Msps. This sampling rate can be sufficiently handled by an existing inexpensive A / D converter.

The input signal digitally converted by the A / D converter 7 is input to a DSP 8, where the input signal is subjected to FFT processing and level detection or the like is performed to determine what signal in what frequency band. You can check if is entered. The confirmation information is sent to the control unit 10,
The control unit 10 selects a channel desired to be received based on the information from the DSP 8, stops the frequency pattern control of the local oscillator 5 by the frequency pattern memory unit 9, and receives only the band in which the desired channel exists. The frequency of the local oscillator 5 is controlled as much as possible. By controlling the oscillation frequency of the local oscillator 5 described above, reception in a desired reception frequency band becomes possible.
The received signal from which unnecessary out-of-band waves have been removed is digitally converted by the A / D converter 7 and then input to the DSP 8, where signal processing such as channel separation and demodulation is performed, enabling voice communication and data communication. Becomes

In the above-described embodiment, the FFT function is implemented to perform the frequency analysis of the wideband signal inside the DSP 8, but the outline of the configuration of another embodiment of the wideband receiver according to the present invention shown in FIG. As shown, the FFT processing unit can be provided outside the DSP. The broadband receiver shown in the figure includes an antenna 1, an RF bandpass filter 2,
It comprises an F-amplifier 3, a monitoring unit 40, a receiving unit 50, and a control unit 10. The monitoring unit 40 includes a mixer 41, a local oscillator 42, an IF bandpass filter 43, and an A / D converter 4.
4. It comprises a DSP 45 for performing frequency analysis on a wideband input signal by FFT processing, and a frequency pattern memory unit 46. The receiving unit 50 includes a mixer 51 and a control unit 10.
Local oscillator 52 that oscillates a local signal based on the control signal, IF band-pass filter 53, A / D converter 5
4 and a DSP 55 for performing channel separation, voice or data signal processing.

In FIG. 3, the received wideband signal is R
The signal is amplified by the F amplifier 3 and input to the monitoring unit 40. In the monitoring unit 40, in the same manner as the operation of the receiver in FIG.
Frequency pattern memory section 4 based on control of control section 10
The intermediate frequency signal received and frequency-converted according to the reception pattern from No. 6 is subjected to FFT processing by the DSP 45, analyzes the use condition of the received radio wave in the wideband frequency band, and outputs the analysis result to the control unit 10. The control unit 10 selects a desired frequency band based on the analysis result, and outputs a local signal capable of converting a signal of the desired frequency band to an intermediate frequency to the mixer 51 to the local oscillator 52 of the receiving unit 50. Send a control signal. The received signal of the desired band is converted into an intermediate frequency signal of a predetermined frequency in mixer 51 and input to IF bandpass filter 53. The intermediate frequency signal is subjected to an IF band-pass filter 53 to remove unnecessary waves outside the band, further converted to a digital signal by an A / D converter 54, subjected to signal processing such as channel separation / demodulation processing by a DSP 55, and input to the control unit 10. The data is output from the control unit 10 as a voice or data signal. IF in this case
Bandpass filter 53, A / D converter 54, DSP5
5 can be dealt with by parts of normal performance. By the above operation, the receiver can perform communication by selecting a channel having a good communication environment from the wide band frequency band while constantly monitoring the wide band radio wave environment.

[0020]

As described above, the wideband receiver according to the present invention divides a received high-frequency wideband signal into fixed bandwidths, and converts each band into the same intermediate frequency signal for reception. With such a configuration, the required performance of digital circuit components such as an IF filter, an A / D converter, and a DSP can be significantly reduced, and therefore, a very wide band reception that cannot be handled by a conventional IF filter or A / D converter. There is a remarkable effect that a small and low power consumption receiver can be configured with a simple circuit. Further, the receiver having the above-described configuration can monitor a radio wave environment that changes every moment over a wide range, and can select and change a communication line based on the monitoring result. In this way, the function of the receiver can be given flexibility, which can greatly contribute to the effective use of radio waves.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a wideband receiver according to the present invention.

FIGS. 2A and 2B are diagrams showing examples of reception frequency patterns according to the present invention.

FIG. 3 is a schematic configuration diagram showing another embodiment of the wideband receiver according to the present invention.

FIG. 4 is a schematic configuration diagram showing an example of a conventional receiver in which a part of a wireless function is realized by a DSP.

5 (a) and 5 (b) are diagrams modeling a spectrum of a received input signal and an intermediate frequency signal in the receiver of FIG. 4;

[Explanation of symbols]

1. Antenna, 2. RF bandpass filter,
3, RF amplifier, 4, 41, 51, mixer,
5, 42, 52 ... local oscillator, 6, 43, 53 ... I
F band pass filter, 7, 44, 54 A / D converter, 8, 45, 55 DSP, 9, 46 frequency pattern memory section, 10 control section, 40 monitoring section, 50 .. A receiving section (according to the present invention) 61. an antenna, 62 .. an RF bandpass filter,
63 RF amplifier, 64 mixer 65 local oscillator 66 IF bandpass filter 67 A
/ D converter, 68 · · DSP, 69 · · · control section

Claims (1)

[Claims] 1. A broadband receiver which realizes a part of a radio function such as channel separation and modulation / demodulation by digital signal processing means, divides a wideband received signal into a plurality of bands having a predetermined bandwidth, and Are sequentially converted to have the same intermediate frequency, and the obtained intermediate frequency signal is digitally converted.
A wideband receiver which monitors a radio wave environment by performing FT processing, and selects and receives a band including a desired channel from the divided bands based on the result.