JP2003198424A - Direct spread spectrum signal receiver and transmitter/ receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch the gain of an LNA for improving the dynamic range without interrupting the reception of a direct spread spectrum signal during switching. <P>SOLUTION: A DS signal received by an antenna 10' is fetched by a gain variable LNA 11, fetched via an attenuator/delayer 25 as well, converted to an intermediate frequency signal and processed by a Rake receiving part composed of despreaders 21a and 21b, spread code generators 22a and 22b and a Rake synthesizer 24. The gain of the LNA 11 is switched over a plurality of stages corresponding to a gain control signal from a signal level calculator 20 but the interruption of the received DS signal in the LNA 11 during gain switching is compensated by the DS signal received via the attenuator/delayer 25. Besides, in the signal level calculator 20, the threshold for gain switching of the LNA 11 when increasing a signal level is made different from the threshold when decreasing the signal level. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving device and a transmitting / receiving device, and more particularly to a receiving device and a transmitting / receiving device for a signal modulated using a direct sequence method.

[0002]

[Prior Art] IMT-2000 (International Mobile Teleco
In the next-generation mobile phone system called mmunications-2000), the direct sequence method (hereinafter D
W-CDMA (Wideband-Code D) using S technology
A method called ivision Multiple Access) was adopted as one of the communication methods. This DS system is suitable for mobile communication such as mobile phones because it has little interference with other communications and interference from other communications, is resistant to multipath fading, and has confidentiality.

FIG. 4 is a block diagram showing an example of a conventional transmission apparatus using the DS system, where 1 is a digital modulator,
2 is a spreader, 3 is a spread code generator, 4 is a D / A (digital / analog) converter, 5 is a mixer, 6 is a local oscillator,
7 is a BPF (band pass filter), 8 is a power amplifier,
Reference numeral 9 is a BPF, and 10 is a transmitting antenna.

In FIG. 1, an input digital information signal having a predetermined transmission rate (transmission rate) is supplied to a digital modulator 1 and digitally modulated. This digital modulation method includes FSK (Frequency Shift Keying) and PSK (Phase
Shift Keying) is used. The digital information signal thus digitally modulated (hereinafter referred to as a digital modulation signal) is supplied to the spread code generator 3 and the spreader 2 which constitutes a direct spread (DS) modulator, and is supplied from the spread code generator 3. The signal is mixed (multiplied or exclusive ORed) with the spread code of the pseudo-random data sequence to be spread, and the spectrum is spread to obtain a signal whose band is widened. Below, diffuser 2
Such mixing in step 1 is called DS modulation, and the signal obtained by such DS modulation is called DS signal.

The DS signal output from the spreader 2 is D /
After being converted into an analog DS signal by the A converter 4, it is supplied to the mixer 5 and mixed with the local oscillation signal from the local oscillator 6 to form a radio frequency transmission signal. This transmitted signal is
After the unnecessary band signal is removed by the BPF 7, the power is amplified by the power amplifier 8 and is transmitted via the BPF 9 to the transmitting antenna 1.
Sent from 0.

The spreading code generated by the spreading code generator 3 is faster than the transmission speed of the digital information signal, and by mixing this with the digital modulation signal, the spectrum of the digital modulation signal is spread. The resulting DS signal.

FIG. 5 is a block diagram showing an example of a conventional direct sequence receiver using the DS system. 10 'is a receiving antenna and 11 is a variable gain LNA (Low Noise Amplifie).
r: low noise amplifier), 12 is a BPF, 13 is a mixer, 1
4 is a local oscillator, 15 is a BPF, 16 is an amplifier, 17 is a mixer, 18 is a local oscillator, 19 is an A / D (analog / analog /
20 is a signal level calculator, 21 is a despreader, 22 is a spread code generator, and 23 is a digital demodulator.

In the figure, the transmission signal from the transmission device shown in FIG. 4 is received by the reception antenna 10 ', amplified by the variable gain LNA 11, and then supplied to the mixer 13 through the BPF 12, and then the local oscillator 14 outputs the local signal. It is mixed with the oscillation signal and converted into a first intermediate frequency signal. This intermediate frequency signal passes through the BPF 15, is amplified by the amplifier 16, and is then supplied to the mixer 17. In the mixer 17, the first intermediate frequency signal from the amplifier 16 is mixed with the local oscillation signal from the local oscillator 18 to obtain the second intermediate frequency signal. This second intermediate frequency signal is a DS signal, and this DS signal is supplied to the despreader 21 after being converted into a digital DS signal by the A / D converter 19. Here, the despreader 21 and the spreading code generator 22 form a spreading demodulator.

A spread code is also supplied from the spread code generator 22 to the despreader 21. This spreading code is the same as the spreading code used in the transmitter (FIG. 4). The despreader 21 performs autocorrelation between the supplied DS signal and the spread code, and mixes (multiplies or exclusive ORs) the DS signal and the spread code at the timing when the correlation between them is obtained. . As a result, the despreader 21 outputs the same FS as the output of the digital modulator 1 in the transmitter shown in FIG.
A digital modulation signal digitally modulated by K, PSK, or the like is obtained. The digital modulation signal is supplied to the digital demodulator 23 and demodulated to obtain the original digital information signal.

Further, D output from the A / D converter 19
The S signal is supplied to the signal level calculator 20, the level thereof is calculated, and the gain control signal is generated. The gain control signal controls the gain of the variable gain LNA 11.

By the way, a reception signal of a receiving device used for mobile communication or the like receives a direct wave directly from the transmitting device or a reflected wave or a diffracted wave (reflected and diffracted after being reflected and diffracted by a building or the like). Delayed wave) is the sum. This is called multipath fading. The digital information signal obtained by demodulating the received signal that has undergone multipath fading is different from the digital information signal used for transmission. That is, the received digital information signal has a higher signal error rate than the transmitted digital information signal.

FIG. 6 is a block diagram showing a main part (that is, a spread demodulator part) of a rake receiver for receiving a DS signal that has undergone such multipath fading.
1a and 21b are despreaders, 22a and 22b are spread code generators, and 24 is a Rake combiner.

The overall configuration of this Rake receiver is similar to that shown in FIG. 5, except that the despreader 21,
The part including the spread code generator 22 and the digital demodulator 23 has the configuration shown in FIG. The despreaders 21a and 21b and the spreading code generator 22a in FIG.
22b and the Rake combiner 24 constitute a spread demodulator. Further, the digital demodulator 23 in FIG. 6 corresponds to the digital demodulator 23 in FIG.

FIG. 7 is a schematic diagram showing the signals of the respective parts in FIG. 6 for ease of explanation, and the parts corresponding to those in FIG. 6 are designated by the same reference numerals.

Referring to FIG. 6, the A / D converter 19 shown in FIG.
Is supplied to the despreaders 21a and 21b. This supplied signal is transmitted through a plurality of paths including the direct DS signal (direct wave) from the transmitter as described above. However, the DS signals S ₁ and S ₂ that have passed through two paths will be described here. Of course, these DS signals S ₁ and S ₂ (see FIG.
(A) is a signal that passes through different paths of the same DS signal, and a time difference occurs depending on these paths.

The received DS signal (S ₁ + S ₂ ) (see FIG. 7)
(a)) is supplied to the despreaders 21a and 21b, and the spreading code generators 22a and 22b respectively use the same spreading code as the spreading code generated by the spreading code generator 3 of the transmitting apparatus shown in FIG. And the spread code generator 22a generates the despreader 2
1a, the spread code generator 22b supplies the spread code to the despreader 21b.

In the despreader 21a, the received DS signal (S ₁
+ S ₂ ) of the DS signal S ₁ and the spreading code from the spreading code generator 22a are subjected to autocorrelation, and the received DS signal (S ₁ + S ₂ ) and this spreading code are obtained at the timing when the correlation is obtained. By mixing (multiplication or exclusive OR), the digital modulated signal D ₁ of the received DS signal S ₁ before DS modulation is obtained (FIG. 7B). Similarly, the despreader 2
In 1b, the autocorrelation of the spreading code from DS signal S ₂ and the spreading code generator 22b of the received DS signal (S ₁ + S ₂₎ is taken, received by this correlation has been established timing DS signal (S ₁ + S ₂ ) and this spreading code are mixed (multiplied or exclusive ORed) to obtain the DS of the received DS signal S ₂ .
A digital modulation signal D ₂ before modulation is obtained (FIG. 7).
(B)). These digital modulation signals D ₁ and D ₂ are Rake.
It is supplied to the combiner 24, and the phase is adjusted and combined. R
The combined signal D output from the ake combiner 24 is supplied to the digital demodulator 23 and demodulated to obtain the original digital information signal.

In this way, the Rake receiver demodulates not only direct waves but also signals (delayed waves) that have passed through paths where reflection and diffraction occur, and these are mixed and used.
It has the effect of reducing the signal error rate. In addition, in FIG.
Although the Rake receiver that processes only the signals that have passed through the two paths has been shown, by increasing the number of despreaders and spreading code generators used, it is possible to use a larger number of delayed waves and thereby to improve the signal error rate. Can be further reduced.

[0019]

A receiver having the configuration shown in FIGS. 5 and 6 has a tuner circuit for receiving a DS signal. In this tuner circuit, in order to widen the range of signal levels that can be received, the LNA provided there is made to have a variable gain, and the gain can be switched by a switch. Explaining, the variable gain LNA1 in the receiving system R
The circuit series from 1 to the mixer 17 forms a tuner circuit, the signal level calculator 20 calculates the level of the DS signal output from the A / D converter 19, and the gain control is performed according to the calculated level. A signal is generated and the gain of the variable gain LNA 11 is controlled by this gain control signal.

Here, the gain of the LNA cannot be continuously changed, and the LNA having a fixed gain is selected by the switch means. Therefore, the gain can be varied depending on the operation of the switch means. The steps can be switched discontinuously.

Therefore, when the gain of the variable gain LNA 11 is switched, the DS signal is momentarily cut off. Therefore, in the one having the configuration of the Rake receiver as shown in FIG. 6, there is a period in which neither a direct wave nor a delayed wave of the DS signal exists, and the despreaders 21a, 2a during that period are generated.
Malfunction occurs in 1b.

In a receiving apparatus that receives data by the time division multiplexing method, the gain of the variable LNA may be switched during a period in which desired data is not received. For example, in a mobile terminal such as a mobile phone. As described above, in the receiving device of the mobile terminal that continuously receives desired data without interruption, when the level of the received signal fluctuates due to the movement of the receiving device, the gain of the variable gain LNA is switched in response to this. It is necessary. However, if such a switching is performed, the gain variable L is inevitably received during the reception of the DS signal.
Since the gain of the NA is switched, the gain of the variable gain LNA cannot be switched without interruption of the received signal.

An object of the present invention is to solve the above problems and provide a direct spread signal receiving apparatus and a transmitting / receiving apparatus in which the interruption of the received signal does not occur even if the gain of the variable gain LNA is switched during reception. It is in.

[0024]

In order to achieve the above object, a direct spread signal receiving apparatus according to the present invention includes a variable gain low noise amplifier for amplifying a received radio frequency direct spread signal, and the low noise amplifier. Frequency conversion means for converting the radio frequency direct spread signal output from the radio frequency converter into an intermediate frequency direct spread signal, an analog / digital converter for converting the direct spread signal from the frequency conversion means into a digital signal, and the analog / digital converter A signal level calculator that calculates the signal level of the output signal of the digital converter and switches the gain of the low-noise amplifier according to the calculation result, and a digital direct spread signal output from the analog / digital converter as a digital modulation signal. Spreading demodulation means for demodulating, and a digital demodulator for demodulating the digital modulation signal demodulated by the spreading demodulation means into a digital information signal An attenuator / delayer for attenuating and delaying the radio frequency direct spread signal received via an antenna, and supplying the radio frequency direct spread signal output from the attenuator / delay device to the frequency conversion means. Is.

The frequency conversion means is supplied with the radio frequency direct spread signal output from the low noise amplifier and the radio frequency direct spread signal output from the attenuator / delayer, synthesizes them, and passes them with a small loss. A first band pass filter, a first mixer for converting a radio frequency direct spread signal output from the first band pass filter into a first intermediate frequency direct spread signal, and the first mixer A second band pass filter for passing the first intermediate frequency direct spread signal output from the second band pass filter with a small loss, and the second intermediate band direct spread signal output from the second band pass filter to the second band pass filter. And a second mixer for converting the intermediate frequency direct spread signal to a signal to be supplied to the analog / digital converter. Attenuating signals waveband, the second band-pass filter is to attenuate the signal in the frequency band other than the direct spread signal of the first intermediate frequency of the desired reception.

The digital direct spread signal output from the analog / digital converter is processed by the frequency converting means by combining a plurality of radio frequency direct spread signals received by the antenna via different paths. The spreading demodulation means is provided for each N (where N is an integer of 2 or more) despreader to which the digital direct spread signal output from the analog / digital converter is supplied, and for each despreader. The
Rake combining for generating a spreading code used in a transmitting device that has transmitted a direct spread signal of a radio frequency and supplying N spreading code generators to be supplied to the corresponding despreader and outputs of the N despreaders. The N despreaders spread and demodulate the digital direct spread signals through different paths.

Further, the signal level calculator described above is a threshold value for switching the gain of the low noise amplifier from one gain to the other gain when the signal level of the output signal of the analog / digital converter increases. And a threshold value that determines the level at which the gain of the low noise amplifier is returned from the other gain to the one gain when the signal level of the output signal of the analog / digital converter decreases.

In order to achieve the above object, a direct spread signal transmitting / receiving apparatus according to the present invention uses the above direct spread signal receiving apparatus as a receiving system and uses a common antenna for the receiving system and the transmitting system. Has a spreader and a spread code generator that supplies a spread code to the spreader.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a direct spread signal receiving apparatus according to the present invention. 10 'is a receiving antenna, 11 is a variable gain LNA, 12 is a BPF,
13 is a mixer, 14 is a local oscillator, 15 is a BPF, 16
Is an amplifier, 17 is a mixer, 18 is a local oscillator, 19 is A
/ D converter, 20 is a signal level calculator, 21a, 21b
Is a despreader, 22a and 22b are spread code generators, 23 is a digital demodulator, 24 is a Rake combiner, and 25 is an attenuation / attenuator.
This is a delay device, and parts corresponding to those in FIGS. 5 and 6 are designated by the same reference numerals.

This embodiment constitutes a Rake receiver with an LNA gain switching function. Further, for convenience of explanation, this embodiment is assumed to receive the transmission signal from the transmission device shown in FIG.

In the figure, a radio frequency transmission signal from the transmission device is received by a reception antenna 10 '. This received signal is supplied to the variable gain LNA 11 and the attenuator / delayer 25. The variable gain LNA 11 has an effect of amplifying the received signal and reducing noise added to the received signal in the receiving device. This is referred to as reducing the noise figure of the receiving device, and in a receiving device that receives a low-level signal, the first stage is generally composed of an LNA as in this embodiment.

The variable gain LNA 11 is constructed so that the gain can be switched in a plurality of steps. As described with reference to FIG. 5, the level of this received signal is calculated by the signal level calculator 20, and the gain corresponding to the calculation result is obtained. A control signal is generated,
This gain control signal switches the gain of the variable gain LNA 11.

On the other hand, the attenuator / delay device 25 is used for the antenna 1
The received signal from 0'is attenuated, delayed, and output. The attenuator / delayer 25 is composed of a passive element in order to prevent power consumption.

The output signal of the variable gain LNA 11 and the output signal of the attenuator / delay device 25 are supplied to the BPF 12. The BPF 12 passes these received signals with a small loss and attenuates a signal in an image frequency band described later to a desired level.

The output signal RF of the BPF 12 is supplied to the mixer 13, mixed with the local oscillation signal LO ₁ from the local oscillator 14, and frequency-converted into the _first intermediate frequency signal IF ₁ .

Now, assuming that the frequency of the output signal RF of the BPF 12 is f _RF and the frequency of the local oscillation signal LO ₁ is f _LO1 ,
The frequency f _IF1 of the first intermediate frequency signal IF ₁ is f _IF1 = f _LO1 −f _RF (1) (provided that f _LO1 > f _RF ).

By the way, a receiving device of a mobile terminal such as a mobile phone receives a radio frequency signal other than a radio frequency signal of a desired frequency f _RF (hereinafter referred to as a reception desired signal). A signal of a frequency (f _LO1 + (f _LO1 −f _RF ) = 2f _LO1 −f _RF ), which is symmetrical with respect to the desired reception frequency f _RF with respect to the frequency f _IF1 of the local oscillation signal LO ₁ , is received. An image frequency band signal with respect to a radio frequency signal) is also received from the receiving antenna 10 '. When a signal in such an image frequency band is supplied to the mixer 13 and converted into an intermediate frequency signal by the local oscillation signal LO ₁ , the frequency f _IM1 of this intermediate frequency signal is f _IM1 = (2f _LO1 −f _RF ) −f _LO1 = f _LO1 −f _RF , which is equal to the frequency f _IF1 of the first intermediate frequency signal IF ₁ of the reception desired signal shown in the above equation (1).

Although f _LO1 > f _RF is set here,
It may be f _LO1 <f _RF , and the same applies in that case.

In this way, when the desired signal to be received and the signal in the image frequency band thereof are received and supplied to the mixer 13, they are converted into an intermediate frequency signal of the same frequency and mixed with each other, thereby deteriorating the received signal. It will be. BPF1
2 attenuates the signal in the image frequency band before mixing with the desired signal to be received to a desired level, and
Signals in frequency bands other than the desired reception signal are also attenuated to a desired level.

The first intermediate frequency signal IF ₁ output from the mixer 13 passes through the next BPF 15, is amplified by the amplifier 16, and is then supplied to the mixer 17 to be output from the local oscillator 18 by the local oscillation signal LO. _It is mixed with ₂ and frequency converted into a _second intermediate frequency signal IF ₂ .

Here, the frequency f _IF1 of the first intermediate frequency signal IF ₁ of the reception desired signal supplied to the mixer 17 is represented by the above equation (1). If the frequency of the local oscillation signal LO ₂ output from the local oscillation 18 is f _LO2 ,
The frequency f _IF2 of the _second intermediate frequency signal IF ₂ obtained from the mixer 17 is f _IF2 = f _LO2 −f _IF1 (2) (where f _LO2 > f _IF1 ). Further, regarding the frequency f _LO2 of the local oscillation signal LO ₂ , the frequency f _IM2 of the signal in the image frequency band of the _first intermediate frequency signal IF ₁ is f _IM2 = f _LO2 + (f _LO2 −f _IF1 ) = 2f _LO2 − f _IF1 . The signal in the image frequency band is also used by the mixer 17
When fed at the same time, the local oscillation signal LO _2, the frequency f _IM2 is an intermediate frequency signal _{f IM2 = (2f LO2 -f IF1} ) -f LO2 = f LO2 -f IF1, the frequency f _IM2 is The second intermediate frequency signal IF ₂ of the desired reception signal represented by the above equation (2)
Is equal to the frequency of.

As described above, even when the first intermediate frequency signal IF ₁ of the desired reception signal is converted into the second intermediate frequency signal by the mixer 17, the signal in the image frequency band is also supplied to the mixer 17. As a result, these are converted into an intermediate frequency signal of the same frequency and mixed with each other, which deteriorates the received signal. The BPF 15 allows the first intermediate frequency signal IF ₁ of the desired reception signal to pass therethrough with a small loss, and the second intermediate frequency signal I 1 of the desired reception signal as described above.
A signal in the image frequency band of the _first intermediate frequency signal IF ₁ before being mixed with F ₂ is attenuated to a desired level, and
Similar to the BPF 12, signals in frequency bands other than the desired reception signal are also attenuated to a desired level.

Although f _LO2 > f _IF1 is set here,
It may be f _LO2 <f _IF1 , and the same applies in that case.

The second intermediate frequency signal IF ₂ output from the mixer 17 is a DS signal, which is converted into a digital signal by the A / D converter 19 and supplied to the despreaders 21a and 21b. As described in 7, the despreader 21
In (a), the same spreading code as that of the spreading code generator 3 (FIG. 4) in the transmission device output from the spreading code generator 22a is correlated and mixed (multiplication or exclusive OR), and despreading is performed. In the device 21b, the same spreading code as that of the spreading code generator 3 (FIG. 4) in the transmission device, which is output from the spreading code generator 22b, is correlated and mixed (multiplied or exclusive OR) to obtain FSK, respectively. It becomes a digitally modulated signal that is digitally modulated such as PSK.

The output signal of the despreader 21a is, for example, a direct wave digital modulation signal, and the output signal of the despreader 21b is, for example, a delayed wave digital modulation signal that has passed through a path involving reflection and diffraction. And the Rake combiner 24 combines the phases and gives a predetermined weighting to combine them. The output signal of the Rake combiner 24 is demodulated by the digital demodulator 23 into the original digital information signal.

As described above, since the Rake receiver is configured, both the direct wave and the delayed wave can be demodulated and used, which has the effect of reducing the signal error rate. In this embodiment, the Rake receiver that processes only two waves, the direct wave and the delayed wave, is used. However, by using more sets of the despreader and the spread code generator,
It is possible to cope with a larger number of delayed waves and further reduce the signal error rate.

D output from the A / D converter 19
The signal level of the S signal is also supplied to the calculator 20, the signal level of the DS signal is calculated, and a gain control signal corresponding to the calculation result is generated. The gain control signal switches the gain of the variable gain LNA 11, and the received signal becomes a desired constant level signal.

Specifically, when the input signal level of the A / D converter 19 is low, the gain of the variable gain LNA 11 is set to the first gain which is the maximum gain to reduce the noise figure,
When the input signal level of the A / D converter 19 increases from this small level to reach a certain threshold A, the gain variable LNA1
The unity gain is switched from the first gain to a smaller second gain. When the input signal level of the A / D converter 19 decreases from the level equal to or higher than the threshold value A (at this time, the gain of the variable gain LNA 11 is the second gain),
Even if this level reaches the threshold value A, the gain of the variable gain LNA 11 does not switch, and the threshold value B (A
> B), the gain of the variable gain LNA 11 is switched from the second gain to the maximum gain, which is the first gain, and the noise figure is lowered.

As a result, the circuit block on the output side of the variable gain LNA 11 is prevented from being supplied with an excessive level of signal, so that the dynamic range of the receiver is improved. When the threshold for switching the gain of the variable gain LNA 11 is switched from the first gain to the second gain,
On the contrary, by setting different values when switching from the second gain to the first gain, even if the input signal level of the A / D converter 19 varies near the threshold value, the gain variable LNA
It is possible to prevent the phenomenon that 11 is frequently switched accordingly.

Here, the gain set in the variable gain LNA 11 is defined as two gains of the first gain and the second gain, but it is also possible to switch three or more gains to be used, It goes without saying that there is a threshold value as described above for each switching.

At the instant when the gain of the variable gain LNA 11 is switched, the DS signal is interrupted by the variable gain LNA 11. In the conventional Rake receiver, neither the instantaneous direct wave nor the delayed wave is input, but in this embodiment, the variable gain L
The DS signal instantaneously cut off at NA11 is input through the attenuator / delayer 25. Despreaders 21a and 21b on the output side of the A / D converter 19 and spread code generators 22a and 2a
2b, in the Rake receiving block including the Rake combiner 24, the DS signal continues to be captured by the attenuator / delayer 25 even if the DS signal is instantaneously interrupted by the variable gain LNA 11, and the error rate is reduced. Prevent.

This will be described with reference to FIG.
(C) shows the operation when the gain of the variable gain LNA 11 is not switched, and S ₁ and S ₂ respectively show the direct wave and the delayed wave that have passed through the variable gain LNA 11, and S ₁ ′,
S ₂ 'denotes a direct wave and a delayed wave that have passed through the attenuator / delay device 25, respectively. In this case, the direct wave S ₁ and the delayed wave S ₂ (FIG. 2A) that have passed through the variable gain LNA 11 are attenuator / delayer 2
The direct wave S ₁ ′ and the delayed wave S ₂ ′ (FIG. 2 (b)) that have passed through 5 are combined by the BPF 12 and these combined signals (FIG.
(C)) is sequentially processed from the mixer 13, and R shown in FIG.
In the case of the ake reception block, the DS signal of the direct wave S ₁ is the despreader 21 a, and the DS signal of the direct wave S ₁ ′ is the despreader 2
1b will be processed respectively.

When the gain is switched by the variable gain LNA 11, the instant direct wave S ₁ and the delayed wave S ₂ are cut off, and the attenuator / delayer is used as shown in FIG. 2C. The direct wave S ₁ ′ and the delayed wave S ₂ ′ that have passed through 25 are mixer 1
It is processed from 3. In this case, 'the DS signal despreader 21a of a delay wave S _2' direct wave S ₁ so that the DS signal are respectively processed by the despreader 21b.

The gain attenuation of the attenuator / delayer 25 is
When the input signal level of the A / D converter 19 is the above threshold value B, the signal-to-noise ratio of the received signal passing through the attenuator / delay device 25 is set to a level that satisfies a desired error rate.

FIG. 3 is a block diagram showing a specific example of a mobile terminal such as a mobile phone using the above embodiment.
10 "is a transmitting / receiving antenna, 26 is a BPF, 27 is a duplexer, 28 is a digital signal processing circuit, 29 is a D / A converter, 30 is a speaker, 31 is a microphone, and 32 is A.
A / D converter, 33 is a keyboard, and 34 is a display, and parts corresponding to those in FIGS. 4 and 1 are denoted by the same reference numerals.

In this specific example, the transmitting system T uses the configuration of the transmitting operation shown in FIG. 4, the receiving system R uses the embodiment shown in FIG. 1, and an antenna is provided with a duplexer 27 for both transmission and reception. Is.

First, the transmission system T will be described.

In FIG. 3, during a call, the audio signal output from the microphone 31 is converted into a digital information signal by the A / D converter 32, and the digital signal processing circuit 28 is used.
Is processed in. The digital information signal associated with the operation is also supplied from the keyboard 33 to the digital signal processing circuit 28.

These digital information signals processed by the digital signal processing circuit 28 are modulated by the digital modulator 1 into a digital modulated signal as described with reference to FIG. 4, and this digital modulated signal is processed by the spreader 2. Becomes a DS signal. The DS signal becomes an analog signal in the D / A converter 4, the unnecessary band component is removed by the BPF 26, and then supplied to the mixer 5, mixed with the local oscillation signal from the local oscillator 6 and transmitted at a predetermined radio frequency. Become a signal. After the unnecessary band component is removed by the BPF 7, this transmission signal is power-amplified by the power amplifier 8 and further supplied to the BPF 9. The BPF 9 prevents the transmission wave from leaking into the reception frequency band in the duplexer 27 and removes noise such as unnecessary spurious. The transmission signal output from the BPF 9 is transmitted from the transmitting / receiving antenna 10 ″ via the duplexer 27.

Next, the receiving system R will be described.

The radio frequency signal received by the transmitting / receiving antenna 10 "is amplified by the variable gain LNA 11 (see FIG. 2).
(a)), and is attenuated / delayed by the attenuator / delayer 25 (see FIG. 2).
(b)), respectively supplied to the BPF 12 and synthesized. The combined signal processed by the BPF 12 as described above is supplied to the mixer 13, mixed with the local oscillation signal from the local oscillator 14, and converted into a first intermediate frequency signal. This first
The intermediate frequency signal of 1 is subjected to the above processing by the BPF 15, amplified by the amplifier 16, and supplied to the mixer 17.

In the mixer 17, the first intermediate frequency signal from the amplifier 16 and the local oscillation signal from the local oscillator 18 are mixed, and an analog D signal as a second intermediate frequency signal is mixed.
An S signal is obtained. This DS signal is supplied to the A / D converter 19
Is converted into a digital DS signal by. This DS signal is
As described with reference to FIGS. 6 and 7 and FIG. 1, the despreader 21
a, 21b and the Rake combiner 24 process the digital modulated signal, and the digital demodulator 23 demodulates the original digital information signal.

If this digital information signal is a voice information signal, it is processed by the digital signal processing circuit 28, and then converted into an analog voice signal by the D / A converter 29 and supplied to the speaker 30 for voice. In the case of the image information or character information signal other than the signal, it is processed by the digital signal processing circuit 28 and then supplied to the display 34 or the like.

In this specific example as well, the variable gain LNA is used.
At the time of switching the gain of 11, the interruption of the reception of the direct wave or the delayed wave at this time is satisfied by the signal from the attenuator / delay device 25. Further, the threshold value A in the signal level calculator 20,
The same applies to B as in the embodiment shown in FIG.

[0065]

As described above, according to the present invention,
The DS signal can be continuously captured even at the moment of switching the gain of the LNA, the gain of the LNA can be switched without lowering the error rate of the received signal, and the dynamic range can be improved.

Further, even if the signal level continues to fluctuate in the vicinity of the LNA gain switching threshold, the LNA gain switching does not repeat and the gain is set stably, so that the signal level does not fluctuate. can do.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a direct spread signal receiving apparatus according to the present invention.

FIG. 2 is a diagram showing an operation of the embodiment shown in FIG.

FIG. 3 is a block diagram showing a specific example of a mobile terminal using the present invention.

FIG. 4 is a block diagram showing a conventional example of a transmission device using the DS system technology.

FIG. 5 is a block diagram showing a conventional example of a receiver using the DS system technology.

FIG. 6 is a block diagram showing another conventional example of a receiver using the DS system technology.

FIG. 7 is a diagram schematically showing signals of respective parts in FIG.

[Explanation of symbols]

1 Digital modulator 2 diffuser 3 Spread code generator 4 D / A converter 10,10 ', 10 "antenna 11 Variable gain LNA 12 BPF 13 mixer 14 Local oscillator 15 BPF 17 mixer 18 Local oscillator 19 A / D converter 20 Signal level calculator 21a, 21b despreader 22a, 22b Spread code generator 23 Digital demodulator 24 Rake combiner 25 Attenuator and delay device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Isao Ikuta             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Development Book             Department (72) Inventor Akio Yamamoto             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Development Book             Department (72) Inventor Yukiya Ueki             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Development Book             Department (72) Inventor Masaki Noda             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Hitachi Digital Media Development Book             Department F term (reference) 5K022 EE02 EE31

Claims (5)

[Claims] 1. A variable gain low noise amplifier for amplifying a received radio frequency direct spread signal, and a frequency for converting the radio frequency direct spread signal output from the low noise amplifier into an intermediate frequency direct spread signal. Converting means, an analog / digital converter for converting the intermediate frequency direct spread signal from the frequency converting means into a digital signal, and a signal level of an output signal of the analog / digital converter, A signal level calculator that switches the gain of the low noise amplifier according to the digital signal, a spread demodulation unit that demodulates the digital direct spread signal output from the analog / digital converter into a digital modulation signal, and a digital demodulated by the spread demodulation unit. A digital demodulator that demodulates the modulated signal into a digital information signal, and attenuates or delays the direct spread signal of the radio frequency received via the antenna. And a damping-delay device, a direct spread signal receiving apparatus of the direct spread signal of the radio frequency output from the attenuation-delay device and supplying to said frequency converter. 2. The frequency conversion means according to claim 1, wherein the radio frequency direct spread signal output from the low noise amplifier and the radio frequency direct spread signal output from the attenuator / delayer are used. A first band-pass filter that is supplied, synthesized, and passes with a small loss, and converts the radio-frequency direct-spread signal output from the first band-pass filter into a first intermediate-frequency direct-spread signal. A first mixer, a second band pass filter for passing the first intermediate frequency direct spread signal output from the first mixer with a small loss, and an output from the second band pass filter A second intermediate frequency direct spread signal is converted into a second intermediate frequency direct spread signal and is supplied to the analog / digital converter.
The first band pass filter attenuates signals in a frequency band other than the direct spread signal of the radio frequency desired to be received, and the second band pass filter is the second band pass filter to be received. 1. A direct spread signal receiving apparatus which attenuates signals in frequency bands other than the intermediate spread direct spread signal of 1. 3. The digital direct spread signal output from the analog / digital converter according to claim 1, wherein a plurality of the radio frequency direct spread signals received by the antenna through different paths are combined. And is processed by the frequency conversion means, wherein the spread demodulation means supplies N digital direct spread signals output from the analog / digital converter (where N is an integer of 2 or more). ) Despreaders, and N spreading codes that are provided for each despreader and that generate spreading codes used by the transmission device that has transmitted the radio frequency direct spread signal and that are supplied to the corresponding despreaders. A code generator and a Rake combiner for combining the outputs of the N despreaders, and the N despreaders spread demodulate the digital direct spread signals through different paths. Direct spread signal receiving apparatus characterized by. 4. The signal level calculator according to claim 1, wherein when the signal level of the output signal of the analog / digital converter increases, the gain of the low noise amplifier is increased by one of the gains. From the other gain to the other gain and a level for returning the gain of the low noise amplifier from the other gain to the one gain when the signal level of the output signal of the analog / digital converter decreases. A direct spread signal receiving apparatus characterized in that a threshold to be determined is different. 5. The direct spread signal receiving apparatus according to claim 1 is used as a receiving system, a common antenna is used for the receiving system and the transmitting system, and the transmitting system is a spreader. And a spread code generator that supplies a spread code to the spreader.