JPH10190508A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To digitize a part of a radio reception function, to adapt a communication parameter to communication environment conditions and to mitigate the request frequency accuracy of an oscillator by providing a function for narrowing a frequency band to a channel band and the function for varying the band of the filter in a DSP part. SOLUTION: The DSP part 23 is programmed so as to perform channel selection and demodulation and is provided with the function of a multifrequency oscillator 33 for channel changeover for oscillation at a channel selection frequency, the function of a mixer 35 for synthesizing signals from an A/D converter 21 and channel selection frequency signals from the multifrequency oscillator 33, the function of a narrow-band band-pass filter 37 for narrowing the frequency band of the signals from the mixer 35 to the channel band and the function of a demodulator 39 for demodulating the signals from the band-pass filter 37. Then, since the narrow-band band-pass filter 37 is a programmable digital filter, the characteristics of the band-pass filter 37 are changed so as to enlarge the band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio receiver used for radio communication of a cellular phone or the like, and more particularly, to digitizing a part of a radio communication function and adapting communication parameters to communication environment conditions by software. The present invention relates to a receiver capable of relaxing required frequency accuracy of an oscillator.

[0002]

2. Description of the Related Art Generally, as a conventional receiver such as a personal digital cellular (PDC) type mobile phone,
A configuration as shown in FIG. 8 is known. As shown in FIG. 8, this conventional receiver adopts a so-called double superheterodyne system, and a receiving antenna 1
A first band-pass filter 3 connected to the receiving antenna 1, a channel switching multi-frequency oscillator (first local oscillator) 5, the first band-pass filter 3 and the channel switching multi-frequency A first mixer 7 connected to the oscillator 5 and a second mixer 7 connected to the first mixer 7
, A single-frequency oscillator (second local oscillator) 11, a second mixer 13 connected to the second band-pass filter 9 and the single-frequency oscillator 11, It has a third bandpass filter 15 connected to the mixer 13 and a demodulation circuit 17 connected to the third bandpass filter 15. The signal received by the antenna 1 is the first signal.
, A band signal corresponding to a service band including all channels provided by the system, and a frequency signal for channel selection from the multi-frequency oscillator 5 is transmitted to the first mixer 7. Synthesized by Next, the combined signal from the first mixer 7 is squeezed into a channel band by the second band-pass filter 9, and the second mixer 13 uses the single-frequency oscillator 11 Are synthesized. The synthesized signal from the second mixer 13 is again squeezed into the channel band by the third bandpass filter 15 and demodulated by the demodulation circuit 17.

[0003]

However, the frequency error of the multi-frequency oscillator 5 and the single-frequency oscillator 11 (発 振 器
Due to f), the center frequencies of the second and third bandpass filters 9 and 15 (narrow band filters) that determine the transmission characteristics are deviated from the center frequency of the received signal, and this leads to a deterioration in sensitivity. Was. For example, in a system in which the center frequency of a carrier is 818 MHz, the center frequency interval between adjacent channels is 25 KHz, and the service bandwidth including all channels is 4 MHz, the center frequency of the first band-pass filter 3 is 818 MHz, and the pass band is wide band. 4 MHz, the oscillation frequency of the multi-frequency oscillator 5 is 888 MHz, the oscillation frequency of the single-frequency oscillator 11 is 70.45 MHz, and the center frequencies of the second and third band-pass filters 9 and 15 are 70 MHz, respectively.
z, 450KHz, each with a narrow passband of 21K
Hz, sensitivity degradation (BER = 1) as shown in FIG.
Eb / NO degradation at 0 ^-2 ). Eb / N
O is the energy per bit to noise power density ratio. Here, in general, in mobile phones and the like, it is necessary to suppress the Eb / NO deterioration to about 0.5 dB due to the demand for the sensitivity. As is clear from FIG.
To suppress O degradation to 0.5 dB, Δf should be ± 3 kHz.
The frequency fluctuation range allowed for the dominant multi-frequency oscillator 5 is ± 3.4 pp
m is required to have an extremely high accuracy, and the cost for the oscillator is increased. The present invention has been made in view of the above circumstances, and has been made in view of the above circumstances. It is possible to digitize a part of a wireless reception function, adapt communication parameters to communication environment conditions by software, and reduce required frequency accuracy of an oscillator. The aim is to provide a possible receiver.

[0004]

To achieve the above object, the present invention provides a receiver used in wireless communication,
An RF unit for performing frequency conversion of a received signal received by the receiving antenna and removing unnecessary waves, an A / D converter for converting an analog frequency signal from the RF unit into a digital signal, A DSP unit comprising a programmable processor configured to receive a digital signal from A / D conversion means and to perform channel selection and demodulation operation on the digital signal by a software program, wherein the DSP unit has a frequency It is characterized by having a function of a narrow band-pass filter for narrowing a band to a channel band and a function of changing the band of the filter. Another feature of the present invention is that the DSP unit has a function of changing the band of the narrow band-pass filter so as to expand the band. Another feature of the present invention is that the above D
The SP section is programmed to perform channel selection and demodulation, and functions as a channel switching multi-frequency oscillator that oscillates at a channel frequency, and outputs a signal from the A / D converter and a channel selection frequency signal from the multi-frequency oscillator. By having a function of a mixer for combining, a function of a narrow band-pass filter for narrowing a frequency band of a signal from the mixer to a channel band, and a function of a demodulator for demodulating a signal from the band-pass filter. is there. Another feature of the invention is that
In a receiver used in wireless communication, an RF unit for performing frequency conversion of a received signal received by a receiving antenna and removing unnecessary waves, and for converting an analog frequency signal from the RF unit into a digital signal. A / D conversion means, and a DSP unit comprising a programmable processor configured to receive the digital signal from the A / D conversion means and perform channel selection and demodulation on the digital signal by a software program. Has,
The DSP unit has a function of three narrow bandpass filters having different center frequencies. Another feature of the present invention is that the DSP unit combines a function of a channel switching multi-frequency oscillator oscillating at a channel frequency, a signal from the A / D converter, and a channel selection frequency signal from the multi-frequency oscillator. A mixer function, three narrow bandpass filter functions having different center frequencies arranged in parallel to narrow the frequency band of the signal from the mixer to a channel band, and each signal from the narrowband bandpass filter. And a function of a select circuit for selecting an optimum demodulated signal from the three demodulators.

Another feature of the present invention is that the RF section is connected to the antenna by a first broadband bandpass filter, a single-frequency oscillator, the first broadband bandpass filter, and a single-frequency oscillator. And a second broadband bandpass filter connected to the mixer. Another feature of the present invention is an RF unit for performing frequency conversion of a received signal received by a receiving antenna and removing unnecessary waves, and an analog unit for converting an analog frequency signal from the RF unit into a digital signal. A / D
A receiver used in wireless communication, comprising: a conversion unit; and a digital processing unit configured to input a digital signal from the A / D conversion unit and perform channel selection and demodulation on the digital signal. That is, the digital processing section has a function of a plurality of channel switching transmitters, and has different channel selection frequencies. Another feature of the present invention is the function of a plurality of channel switching multi-frequency oscillators in which the digital processing unit oscillates at a channel selection frequency, the signal from the A / D converter and the channel selection frequency from the multi-frequency oscillator. A function of a mixer for synthesizing a signal, a function of a narrow bandpass filter for narrowing a frequency band of a signal from the mixer to a channel band, and a function of a demodulator for demodulating a signal from the bandpass filter, A function of a select circuit for selecting one of the multi-frequency oscillators so that the signal from the demodulator is optimized.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on illustrated embodiments. FIG. 1 is a configuration diagram showing an embodiment of a receiver according to the present invention. As shown in FIG. 1, this receiver includes a receiving antenna 1, an RF unit 19 connected to the receiving antenna 1, a wideband A / D converter 21 connected to the RF unit 19, Broadband A / D converter 2
DSP (Digital Signal Processor) unit 23 comprising a software programmable processor connected to 1
And The RF unit 19 is for performing frequency conversion and removing unnecessary waves, and includes a first broadband bandpass filter 25 connected to the antenna 1, a single frequency oscillator 27, and a first broadband band. Pass filter 2
5 and mixer 29 connected to single frequency oscillator 27
And a second broadband bandpass filter 31 connected to the mixer 29. The operation of the RF unit 19 is as follows. The signal received by the antenna 1 is narrowed down to a band corresponding to the entire channel by the first band-pass filter 25, and
7 are synthesized by the mixer 29, and the synthesized frequency signal is squeezed again by the second band-pass filter 31. And the second
The analog signal from the band pass filter 31 of A
The digital signal is converted by the / D converter 21.

Next, the DSP unit 23, which is a main part of the present invention, is used.
Is composed of a software programmable processor that performs a control operation by a software program. In the first embodiment, the digital frequency signal from the A / D converter 21 is programmed to perform a function as shown in FIG. I have. That is, the DSP unit 23 is programmed to perform channel selection and demodulation. As shown equivalently in FIG. 2, the function of the channel switching multi-frequency oscillator 33 that oscillates at the channel selection frequency and the A / D The function of the mixer 35 for synthesizing the signal from the converter 21 and the channel selection frequency signal from the multi-frequency oscillator 33, and the function of the narrow band-pass filter 37 for narrowing the frequency band of the signal from the mixer 35 to the channel band. And a function of a demodulator 39 for demodulating the signal from the band-pass filter 37. Since the narrow band-pass filter 37 is a programmable digital filter as described above, the characteristic of the band-pass filter 37 is changed so that the band is expanded. This greatly reduces the dominant frequency accuracy requirement of the single frequency oscillator 27 of the RF unit 19 as compared with the conventional receiver (see FIG. 8).

That is, as a specific example, the center frequency of a carrier wave is 818 MHz, the center frequency interval between adjacent channels is 25 KHz, and the service bandwidth including all channels is 4 kHz.
MHz system, the first and second
4 MHz, the respective center frequencies of 818 MHz and 70 MHz, the oscillation frequency of the single-frequency oscillator 27 is 888 MHz, and the band of the narrow band-pass filter 37 of the DSP unit 23 is When the band of the narrow band-pass filter 37 is expanded by 10% (that is, 25 KHz + 2.5 KHz) in addition to the frequency of 25 KHz, the sensitivity degradation (Eb / B at BER = 10 ^-2 ) as shown by the solid line in FIG.
NO deterioration) and the allowable frequency error of the single frequency oscillator 27 at which Eb / NO becomes 0.5 dB or less is ± 4 kHz.
And the required frequency accuracy is 3.4 ppm from the conventional 3.4 ppm.
Relaxed to 5 ppm. The dotted line shown in FIG. 3 is the sensitivity degradation characteristic of the conventional example (see FIG. 8) for comparison.

Next, a second embodiment of the receiver according to the present invention will be described with reference to FIG. In the second embodiment, as shown in FIG. 4, a receiving antenna 1, an RF unit 19,
The configuration up to the A / D converter 21 is the same as that of the first embodiment described above, except for the function of the DSP unit 41 composed of a software programmable processor. That is,
As shown in FIG. 4, the DSP unit 41 functions as a channel switching multi-frequency oscillator 43 that oscillates at a channel frequency, a signal from the A / D converter 21 and a channel from the multi-frequency oscillator 43. A function of the mixer 45 for synthesizing the selected frequency signal, and three narrow band-pass filters 47 having different center frequencies and arranged in parallel to narrow the frequency band of the signal from the mixer 45 to the channel band.
a, 47b, 47c, three demodulators 49a, 49b, 49c for demodulating the signals from the narrow bandpass filters 47a, 47b, 47c, and three demodulators 49a, 49b, It is configured to have a function of a select circuit 51 for selecting an optimum demodulated signal from the demodulated signal from the demodulator 49c.

The realization of the three band-pass filters 47a, 47b, 47c with the center frequencies shifted by a program requires the frequency accuracy requirement of the single-frequency oscillator 27 of the RF unit 19, which becomes dominant, to the conventional receiver ( (See Fig. 8)
It will be greatly eased compared to. That is, as a specific example, in a system where the center frequency of a carrier is 818 MHz, the center frequency interval between adjacent channels is 25 KHz, and the service bandwidth including all channels is 4 MHz, the first and second broadband bandpass filters 2 are used.
The respective bands of 5 and 31 are 4 MHz, the respective center frequencies are 818 MHz and 70 MHz, the oscillation frequency of the single frequency oscillator 27 is 888 MHz,
Bandpass filters 47a, 47 of the DSP unit 41
When the band of b and 47c is set to 21 KHz and the center frequency of the band-pass filters 47a and 47c is shifted by ± 6 KHz with respect to the center frequency of the band-pass filter 47b, the sensitivity degradation (BER = 10) shown by the solid line in FIG. ^-2 Eb / NO degradation), and Eb / NO is 0.5d
B, the permissible frequency error of the single-frequency oscillator 27 becomes ± 9 KHz, and the required frequency accuracy is 3.4 p.
pm to 10.1 ppm. Where 1
A frequency accuracy of about 0 ppm can be obtained with a crystal oscillator that has been subjected to simple temperature compensation, so that a local oscillator that is simpler and less costly than in the past can be used.

Next, a modification of the second embodiment will be described with reference to FIG. As shown in FIG. 6, in this modified example, the configuration of the DSP unit in the second embodiment is different, and the DSP unit 52 of this modified example includes three multi-frequency oscillators 53a, 53b, The function of 53c and three mixers 55a, 55b, 5c for synthesizing the frequency signal from the multi-frequency oscillators 53a, 53b, 53c in parallel with the digital signal from the A / D converter 21
5c and three narrow band-pass filters 57a, 57b, 57 for inputting the combined signals from the mixers 55a, 55b, 55c in parallel to narrow down the frequency band.
c and the three narrow bandpass filters 57
a, 57b, and 57c, the functions of three demodulators 59a, 59b, and 59c for demodulating the frequency signals in parallel.
It has a function of a select circuit 61 for selecting an optimal demodulated signal from the demodulators 59a, 59b, 59c. According to this modification, the same effect as in the second embodiment can be obtained.

Next, another modification of the second embodiment will be described with reference to FIG. As shown in FIG.
This modified example also differs in the configuration of the DSP unit in the second embodiment. The DSP unit 62 of this modified example includes three multi-frequency oscillators 63a, 63b, and 63 with shifted oscillation frequencies.
3c and the three multi-frequency oscillators 63a, 63
switch 6 for sequentially selecting one of the outputs of b and 63c
4, a function of a mixer 65 for synthesizing the oscillation frequency sequentially selected by the switch 64 with the digital signal from the A / D converter 21, and a function for narrowing down the frequency band of the synthesized signal from the mixer 65. The function of the narrow band pass filter 67 and the function of the narrow band pass filter 6
7 and a function of the demodulator 69 for demodulating the frequency signal from
It has a function of a select circuit 71 for selecting the most suitable demodulated signal from the sequentially transmitted demodulated signals. According to this modification, the same effect as in the second embodiment can be obtained. In the above embodiment, a DSP using a software programmable processor has been described as an example. However, the present invention is not limited to this, and a DSP using a so-called CPU or a combination of logic circuits is used. It goes without saying that a circuit capable of digital signal processing realized by the above may be applied.

[0013]

According to the present invention, as described above, the DSP unit is constituted by a software programmable processor or the like programmed to perform channel selection and demodulation.
Since the DSP unit has a function of expanding a band of a narrow band-pass filter for narrowing a frequency band to a channel band or a function of three narrow band-pass filters having different center frequencies, the DSP unit becomes dominant. The requirement for the frequency accuracy of the single frequency oscillator can be relaxed. In addition, since the required frequency accuracy of the single-frequency oscillator can be relaxed, a frequency oscillator of about 10 ppm can be obtained with a crystal oscillator that has been subjected to simple temperature compensation. Available.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an embodiment of a receiver according to the present invention.

FIG. 2 is an equivalent functional block diagram of a first embodiment of the DSP unit shown in FIG. 1;

FIG. 3 is a characteristic diagram of sensitivity degradation in the receiver having the DSP unit of the first embodiment shown in FIG. 2;

FIG. 4 is a configuration diagram showing a second embodiment of the receiver according to the present invention.

5 is a characteristic diagram of sensitivity degradation in the receiver having the DSP unit of the second embodiment shown in FIG.

FIG. 6 is a configuration diagram of a modification of the second embodiment shown in FIG.

FIG. 7 is a configuration diagram of a modified example of the second embodiment shown in FIG.

FIG. 8 is a configuration diagram of a conventional receiver.

9 is a characteristic diagram of sensitivity degradation of the conventional receiver shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Receiving antenna, 3 ... 1st band pass filter, 5 ... Multi-frequency oscillator for channel switching, 7 ... 1st mixer, 9 ... 2nd band pass filter, 11 ... Single frequency oscillator, 13 ... 2 mixers, 15 ... third bandpass filter, 17 ... demodulation circuit,
19: RF unit, 21: Broadband A / D converter,
23 DSP part, 25 first band-pass filter, 27 single-frequency oscillator, 29 mixer, 31 second band-pass filter, 33 multi-frequency oscillator for channel switching, 35 mixer, 37
... bandpass filter, 39 ... demodulator,
41: DSP unit, 43: Multi-frequency oscillator for channel switching,
45 ... mixer, 47 ... bandpass filter,
49: demodulator, 51: select circuit,
53: Multi-frequency oscillator 55: Mixer, 57: Band pass filter,
59: demodulator, 61: select circuit,
63: Multi-frequency oscillator, 64: Switch,
65: mixer, 67: band-pass filter, 69: demodulator, 71: select circuit,

Claims (6)

[Claims] 1. An RF unit for performing frequency conversion of a received signal received by a receiving antenna and removing unnecessary waves, and an A / D for converting an analog frequency signal from the RF unit into a digital signal. A receiver for use in wireless communication, comprising: a conversion unit; and a digital processing unit that receives a digital signal from the A / D conversion unit and performs channel selection and demodulation on the digital signal. A receiver, wherein the processing unit has a function of a band-pass filter for narrowing a frequency band of a selected channel to a channel band, and the band of the filter is variable. 2. A digital processor comprising a programmable processor, comprising: a function of a channel switching multi-frequency oscillator oscillating at a channel selection frequency; a signal from the A / D converter and a channel selection frequency from a multi-frequency oscillator; A mixer function for synthesizing the signal, a band-pass filter function for narrowing the frequency band of the signal from the mixer to a channel band, and a demodulator function for demodulating the signal from the band-pass filter. The receiver of claim 1, wherein the receiver is programmed. 3. An RF unit for performing frequency conversion of a received signal received by a receiving antenna and removing unnecessary waves, and an A / D for converting an analog frequency signal from the RF unit into a digital signal. A receiver used in wireless communication, comprising: a conversion unit; and a digital processing unit configured to input a digital signal from the A / D conversion unit and perform channel selection and demodulation on the digital signal. A receiver characterized in that the digital processing section has a function of a plurality of bandpass filters having different center frequencies. 4. The mixer according to claim 1, wherein said digital processing unit functions as a channel switching multi-frequency oscillator oscillating at a channel selection frequency and a signal from the A / D converter and a channel selection frequency signal from the multi-frequency oscillator. Features and
The functions of three narrow bandpass filters having different center frequencies arranged in parallel to narrow the frequency band of the signal from the mixer to the channel band, and three functions for demodulating each signal from each of the narrowband bandpass filters. 4. The receiver according to claim 3, wherein the receiver has a function of a demodulator and a function of a select circuit for selecting an optimum demodulated signal from the three demodulators. 5. An RF unit for performing frequency conversion of a received signal received by a receiving antenna and removing unnecessary waves, and an A / D for converting an analog frequency signal from the RF unit into a digital signal. A receiver used in wireless communication, comprising: a conversion unit; and a digital processing unit configured to input a digital signal from the A / D conversion unit and perform channel selection and demodulation on the digital signal. A receiver characterized in that the digital processing section has a function of a plurality of channel switching transmitters and has different channel selection frequencies. 6. A function of a plurality of channel switching multi-frequency oscillators oscillated at a channel selection frequency by the digital processing unit, and a signal from the A / D converter and a channel selection frequency signal from the multi-frequency oscillator are combined. The function of a mixer to perform, the function of a narrow band-pass filter for narrowing the frequency band of the signal from the mixer to the channel band,
The apparatus according to claim 1, further comprising a demodulator function for demodulating the signal from the band-pass filter and a select circuit function for selecting one of the multi-frequency oscillators so that the signal from the demodulator is optimized. Item 6. The receiver according to Item 5.