JP4027565B2 - Digital receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital receiver, and more particularly to a digital receiver capable of extending the dynamic range of an A / D converter over a wide frequency band.
[0002]
[Prior art]
In recent years, with the development of digital circuit technology, there are an increasing number of examples in which functions realized by analog circuits are realized by digital circuits. When functions are realized with digital circuits, there are advantages that there is no variation in characteristics, there is no deterioration over time, and there is no need for adjustment. Furthermore, when programmable devices such as DSPs are used as digital circuits, the functions are described by software. Therefore, the merit that correction and change are easy is also obtained.
In the field of mobile communications such as digital cellular phones, the transition to digital circuits is progressing, and by realizing communication functions with software in DSPs, etc., there are receivers that can easily modify and change modulation / demodulation functions and filter functions. As an ultimate example, a software defined radio that realizes most of the communication functions with software has been proposed.
[0003]
FIG. 4 is a schematic configuration diagram showing an example of a conventional wideband digital receiver that performs modulation / demodulation by converting a received signal into a digital signal with a wideband.
The wideband digital receiver is a receiver that performs A / D conversion on the received wideband signal as it is in the RF band or IF band, and performs processing after channel separation by a digital circuit.
As shown in the figure, this receiver includes an antenna 100 that receives radio waves, an RF unit 1 that converts a received signal into a predetermined intermediate frequency signal, a bandpass filter (BPF) 2, an AGC (Automatic Gain Control). (Gain control) It comprises an amplifier 3, an A / D converter 4 and a digital signal processing unit 9.
[0004]
In the figure, the received signal received by the antenna 100 is converted into an intermediate frequency signal (IF signal) having a predetermined frequency in the RF unit 1 while being in a wide band, and is input to the band pass filter 2.
In the band pass filter 2, the IF reception signal is output to the AGC amplifier 3 after being subjected to necessary band restrictions. The necessary band mentioned here is a band that can be received by the wideband digital receiver, and is set to match the service band band of a system that is normally used. Here, the pass bandwidth of the bandpass filter 2 is Wb.
The AGC amplifier 3 amplifies and outputs the input IF signal to the A / D converter 4 at the next stage so as to be maximized within a range not exceeding the maximum input level of the A / D converter 4. . The IF signal amplified by the AGC amplifier 3 is converted into a digital signal in a wide band by the A / D converter 4 and output to the digital signal processing unit 9, and the digital signal processing unit 9 performs channel separation, demodulation, etc. Signal processing is performed to obtain a data output signal.
[0005]
[Problems to be solved by the invention]
However, in the conventional digital receiver, since the received signal of the frequency band Wb is converted into a digital signal by the A / D converter 4, a plurality of interference waves (other channels, noise, etc.) exist outside the desired channel. In this case, the A / D converter 4 may not have a dynamic range necessary for a desired channel.
That is, if the desired channel level is Vx and the m interference wave levels are Xi (i = 1 to m), the maximum level Vmax of the signal input to the A / D converter 5 is Vmax = Vx + ΣXi. The value of Vmax is amplified and input by the AGC amplifier so as to reach the maximum input level (hereinafter referred to as full scale range: FSR) of the A / D converter 4.
Accordingly, at this time, a dynamic range of a ratio of Vx / (Vx + ΣXi) is allocated to a desired channel signal. At this time, if there is an extremely high level of interference wave Xi with respect to the desired channel level Vx, the dynamic range allocated to Vx is greatly reduced.
This means that the wider the band, the greater the number of interference waves, and thus the higher the probability that the ratio of the dynamic range to the desired channel will be lower.
For this reason, the A / D converter of the wideband digital receiver as described above is required to have a wide dynamic range at a high speed, but there is a problem that it is extremely expensive and large at present.
The present invention has been made to solve the problems of the conventional wideband digital receiver as described above, and can ensure a wide dynamic range for a wideband received signal without degrading the performance. Accordingly, an object of the present invention is to provide a wideband digital receiver that is inexpensive and can use a small A / D converter.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the invention of claim 1, a bandpass filter for limiting a frequency band of a wideband received signal including a plurality of channels frequency-converted to an intermediate frequency by a high-frequency receiver, and the bandpass filter A digital receiver comprising an AGC amplifier that performs output level amplification, an A / D converter that converts the AGC amplifier output into a digital signal, and a digital signal processor that performs signal processing of the output of the A / D converter In
A level adjusting unit that obtains gain control information of the AGC amplifier and adjusts an output level from the A / D converting unit is connected to the A / D converting unit output,
The band-pass filter uses a center frequency of each frequency band allocated by dividing the reception frequency band by N (N is a natural number of 2 or more) as a center of the pass band, and a predetermined pass bandwidth above and below the center frequency. Comprising N bandpass filters having
The AGC amplifier is an amplifier that amplifies the outputs of the N band pass filters so as to match the maximum input level of the A / D converter connected to the AGC amplifier,
The output of the A / D conversion unit is adjusted to a predetermined level by the level adjustment unit connected at a subsequent stage, added by a post addition unit, and input to the digital signal processing unit .
[0007]
According to a second aspect of the present invention, in the receiver according to the first aspect , the pass band of the band-pass filter has a band that is wider above and below each of the frequency bands assigned by dividing the received frequency band into N parts. If there is a desired frequency band across the divided adjacent bands, one of the adjacent bands is selected in accordance with the amplification factor of the AGC amplifier.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on embodiments shown in the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a wideband digital receiver according to a reference example .
As shown in the figure, the receiver includes an antenna 100 that receives radio waves, an RF unit 1 that converts a received signal into a predetermined intermediate frequency signal, N band-pass filters (hereinafter referred to as BPF) 21, .. 2N, AGC amplifiers 31, 32,... 3N connected to the N BPFs 21 to 2N, an adder 6, an A / D converter 7, and a digital signal processing unit 9, respectively. Is done.
The N BPFs 21 to 2N are filters whose pass bands are the respective bands obtained by dividing the total reception bandwidth Wb into N, and the AGC amplifiers 31, 32,... 3N are the outputs of the BPFs 21 to 2N. Are amplified so that the maximum signal level of each becomes a predetermined level.
[0009]
In the figure, the received signal received by the antenna 100 is converted into an intermediate frequency signal (IF signal) having a predetermined frequency in the RF unit 1 while being in a wide band and is input to the BPFs 21, 22,.
In the BPF 21, 22,... 2N, the IF reception signals are output to the AGC amplifiers 31, 32,. As described above, the necessary band referred to here is set so as to match the band allocated with the respective bands obtained by dividing the total reception bandwidth Wb into N as pass bands.
The output of each BPF 21, 22,... 2N is a predetermined level, for example, a value of 1 / N of the FSR of the A / D converter 7, by the AGC amplifiers 31, 32,. It is amplified so that it becomes.
[0010]
The output signals of the AGC amplifiers 31, 32,... 3N are added by the adder 6 and restored to the original reception frequency band. The calculation accuracy at this time is sufficiently larger than the number of quantization bits of the A / D converter 7 so that the dynamic range of each signal can be maintained.
The signal added by the adder 6 is converted into a digital signal by an A / D converter 7 and subjected to signal processing such as channel separation and demodulation in a digital signal processing unit 9 to extract a receiver output signal.
As a result of the above operation, the signal level of the adder 6 output is suppressed from an extremely large level signal in the RF unit 1 output signal, and an extremely small level signal is amplified.
Therefore, the ratio Vx / (Vx + ΣXi) of the dynamic range with respect to the signal of the desired channel can relieve the influence of the interference wave having a large signal level and secure the necessary dynamic range.
[0011]
Figure 2 is a schematic configuration diagram showing an embodiment of implementation of the wideband digital receiver according to the first aspect of the present invention. As shown in the figure, the receiver includes an antenna 100 that receives radio waves, an RF unit 1 that converts a received signal into a predetermined intermediate frequency signal, N band-pass filters (hereinafter referred to as BPF) 21, 2N, AGC amplifiers 31, 32,... 3N connected to the BPFs 21 to 2N, respectively, and A / D converters 41, 42,... 4N connected to the AGC amplifiers 31 to 3N, respectively. The level adjustment circuits 51, 52,... 5N, the adder 8, and the gain control information of the AGC amplifiers 31, 32,. The second A / D converters 61, 62,... 6N output to 5N, the adder 8, and the digital signal processing unit 9 are configured.
The BPFs 21 to 2N are filters whose pass bands are the respective bands obtained by dividing the reception bandwidth Wb by N. Further, the AGC amplifiers 31, 32,... 3N amplify the maximum signal levels of the outputs of the BPFs 21 to 2N so as to become the FSR levels of the connected A / D converters 41, 42,. It is an amplifier.
The functional operation of the antenna 100, the RF unit 1, the BPF 21, 22,... 2N and the digital signal processing unit 9 is the same as that of the antenna 100, the RF unit 1, BPF 21, 22,. It is the same as the functional operation.
[0012]
In the figure, the received signal received by the antenna 100 is converted into an IF signal, divided into N, and input to the AGC amplifiers 31, 32,... 3N, as in the case of the receiver of FIG. In each AGC amplifier 31 to 3N, each signal is amplified to the FSR level of the A / D converters 41, 42,... 4N connected to the AGC amplifiers 31, 32,. / D converters 41, 42,...
The signals converted into digital signals by the A / D converters 41, 42,... 4N are adjusted to signal levels, which will be described later, by level adjusting circuits 51, 52,. In the adder 8, the input signals are added and restored to a signal in the same frequency band as the received signal. The digital wideband received signal added by the adder 8 is input to the digital signal processing unit 9 for signal processing.
[0013]
The input signals of the A / D converters 41, 42,... 4N are amplified at different rates by the AGC amplifiers 31, 32,. In the level adjustment circuits 51, 52,... 5N, for example, the AGC amplifiers 31, 32,. , 62,... 6N to obtain the respective gain control information, and the level is adjusted.
The addition processing in the adder 8 is processed with sufficiently high calculation accuracy compared to the number of quantization bits of the A / D converters 41, 42,... 4N so that the dynamic range of each input signal can be maintained. The
With the above operation, the output signal of the adder 8 becomes a wideband digital signal having a wide dynamic range, and a dynamic range necessary for the signal processing of the digital signal processing unit 9 can be secured.
[0014]
In the receiver of FIG. 2, when the reception frequency band Wb is divided into N, a desired frequency band (for example, reception channel) may be divided by any of the BPFs 21 to 2N. In this case, distortion due to the addition of the outputs of the BPFs 21 to 2N that do not have an ideal band limiting characteristic occurs in a signal in a desired frequency band at the output of the adder 8.
FIG. 3 is a schematic configuration diagram showing an embodiment of a wideband digital receiver corresponding to the above problem. As shown in the figure, this receiver includes an antenna 100 that receives radio waves, an RF unit 1 that converts a received signal into a predetermined intermediate frequency signal, N bandpass filters (hereinafter referred to as BPF) 71, 72N, AGC amplifiers 31, 32,... 3N connected to the BPFs 71 to 7N, A / D converters 41, 42,... 4N, and level adjustment circuits 51, 52,. 5N and second A / D converters 61, 62 for A / D converting the gain control information of the AGC amplifiers 31, 32,... 3N and outputting them to the level adjustment circuits 51, 52,. ..Digital composed of 6N, adder 8, signal processing unit 91 that monitors the entire reception band of the output of adder 8 and second signal processing unit 92 that performs signal processing such as channel separation and demodulation Signal processor 90 and selector 10 In constructed.
Each of the BPFs 71 to 7N is a filter having a pass band equal to or greater than each band allocated by dividing the reception bandwidth Wb into N parts. Further, the AGC amplifiers 31, 32,... 3N amplify so that the maximum signal level of the output of the BPFs 71 to 7N becomes the level of the FSR of the connected A / D converters 41, 42,. Amplifier.
Further, the functional operation of the antenna 100, the RF unit 1, the AGC amplifiers 31 to 3N, the A / D converters 41 to 4N, the level adjustment circuits 51 to 5N, the second A / D converters 61 to 6N, and the adder 8 are described. Is the same as the functional operation of each part of the same reference numeral in FIG.
[0015]
In the figure, the received signal received by the antenna 100 is converted into an IF signal by the RF unit 1 and input to the BPFs 71, 72,. The BPFs 71, 72,... 7N are filters each having a center frequency of a band obtained by dividing the reception bandwidth Wb by N and having a passband wider than (Wb / 2N) above and below the center frequency. is there. The reception signals divided into N by the BPF 71, 72,... 7N are band-limited and input to the AGC amplifiers 31, 32,.
In the AGC amplifiers 31, 32,... 3N, the respective signals are amplified so as to be at the FSR level of the A / D converters 41, 42,. Is done. After being converted into digital signals by the A / D converters 41, 42,... 4N, they are output to the level adjustment circuits 51, 52,.
In the level adjustment circuits 51, 52,... 5N, each AGC amplifier 31 sent from the AGC amplifiers 31, 32,... 3N via the second A / D converters 61, 62,. ˜3N gain control information is obtained, and the level adjustment circuits 51 to 5N are added by the adder 8 so that the levels between the bands are equalized, for example, the levels are adjusted to return to the respective BPF 71 to 7N output levels. The At the same time, the gain control information from the second A / D converters 61, 62,.
After the level is adjusted as described above, the outputs of the level adjustment circuits 51, 52,..., 5N are added by the adder 8 and output to the signal processing unit 91 of the digital signal processing unit 90. At the same time, the outputs of the level adjustment circuits 51, 52,... 5N are sent to the second signal processing unit 92 of the digital signal processing unit 90, respectively.
[0016]
The signal processing unit 91 monitors the radio wave environment of the entire reception band, searches for the target channel, and the like. For example, where when analyzing signals considering channel signal of the band, estimation of the center frequency by the signal processing unit 9 1, estimates of the modulation scheme, performs such estimation of the modulation parameters, the results second To the signal processing unit 92. The second signal processing unit 92 performs signal processing such as channel separation and demodulation based on information obtained as a result of analysis by the signal processing unit 91.
As a result of monitoring the reception band by the signal processing unit 91, when it is found that the desired channel or band is divided by the reception band, for example, by the BPF 71 and the BPF 72, the second signal processing unit 92 Based on the gain control information of the AGC amplifiers 31 and 32 transmitted to the selector 10 via the second A / D converters 61 and 62, the APF is included in the band of the BPF output with the higher amplification factor of the AGC amplifier. Select the desired channel.
With the above operation, it is possible to select a channel having a digital signal with a wider dynamic range while avoiding distortion due to the addition processing even in the vicinity of the boundary of the divided bands.
In the above example, the selection criterion for selecting a channel included in the output band of the adjacent BPF may be the noise floor level of the BPF output (the average level of noise in the band). In this case, the noise floor By selecting a desired channel included in the band of the higher-level BPF output, a channel having a digital signal with a wider dynamic range can be selected.
[0017]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a digital reception signal having an even wider dynamic range over a wider frequency band than a conventional receiver using a conventional A / D converter. Become.
This greatly contributes to the provision of a low-priced, small-sized digital wireless device that is effective when, for example, a channel with the best radio wave propagation status is selected from all service bands and communication is desired using the channel communication method. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an embodiment of a digital receiver according to a reference example .
[2] configuration schematic diagram showing the one embodiment of the implementation of the digital receiver according to the invention of claim 1, wherein.
FIG. 3 is a schematic configuration diagram showing another modified embodiment of the digital receiver according to the first aspect of the present invention;
FIG. 4 is a schematic configuration diagram showing an embodiment of a conventional digital receiver.
[Explanation of symbols]
1 ·· RF part 2 ·· Band pass filter (BPF)
3 .... AGC amplifier, 4 .... A / D converter, 6 .... adder,
7. A / D converter, 8. Adder,
9. Digital signal processing unit, 10. Selector,
21, 22,... 2N, Bandpass filter (BPF),
31, 32, 3N, AGC amplifier,
41, 42,... 4N, A / D converter,
51, 52,... 5N, Level adjustment circuit,
61, 62,... 6N, a second A / D converter,
71, 72,... 7N, Bandpass filter (BPF),
90 .. Digital signal processing unit 91.. Signal processing unit
92 .. Second signal processing unit, 100 .. Antenna

Claims (2)

A band-pass filter that limits a frequency band of a wide-band received signal including a plurality of channels that are frequency-converted to an intermediate frequency by a high-frequency receiver, an AGC amplifier that performs level amplification of the band-pass filter output, and an AGC amplifier output In a digital receiver comprising an A / D converter for converting into a digital signal and a digital signal processor for performing signal processing of the output of the A / D converter,
A level adjusting unit that obtains gain control information of the AGC amplifier and adjusts an output level from the A / D converting unit is connected to the A / D converting unit output,
The band-pass filter uses a center frequency of each frequency band allocated by dividing the reception frequency band by N (N is a natural number of 2 or more) as a center of the pass band, and a predetermined pass bandwidth above and below the center frequency. Comprising N bandpass filters having
The AGC amplifier is an amplifier that amplifies the outputs of the N band pass filters so as to match the maximum input level of the A / D converter connected to the AGC amplifier,
The digital receiver is characterized in that the output of the A / D conversion unit is adjusted to a predetermined level by the level adjustment unit connected at a subsequent stage, added by a post addition unit, and input to the digital signal processing unit . The passband of the bandpass filter has a band that is wider above and below each frequency band assigned by dividing the received frequency band into N parts,
If the desired frequency band across divided adjacent bands is present, digital claim 1, wherein the selecting one of the band that the adjacent corresponding to the amplification factor of the AGC amplifier Receiving machine.

Images