JP4245981B2 - Direct conversion receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-mode and multi-band direct conversion receiver used in a microwave radio communication system, and more particularly, to a plurality of systems having different signal bandwidths by using a fixed low-pass filter. It is related with the direct conversion receiver comprised so that it can respond to.
[0002]
[Prior art]
A conventional direct conversion receiver is composed of a direct conversion type broadband wireless device, a low noise amplifier for amplifying a received RF signal, a quadrature mixer including two unit mixers arranged in parallel, and two series variable bandwidths. Low-pass filter, IF signal variable gain amplifier and analog-digital converter, demodulator for demodulating each series of output signals, RF terminal for receiving RF signals, and LO terminal for controlling quadrature mixer And. (For example, refer nonpatent literature 1).
[0003]
In the direct conversion receiver described in Non-Patent Document 1, a reception method called a direct conversion method is such that the LO frequency applied from the LO terminal is brought close to the RF frequency of the received RF signal, and finally the same frequency is set. As a result, the frequency of the IF signal is set to zero and is directly converted to the baseband.
[0004]
In this way, if the frequency of the IF signal becomes zero, there is no image signal in principle, so it becomes easy to make a baseband filter IC in hardware, and the receiving unit can be made into one chip. The nature will also increase. Therefore, it can be said that the direct conversion method is the most suitable method for software defined radios in terms of wide bandwidth and versatility.
[0005]
In particular, in the multi-mode direct conversion method, as described above, the received wave is amplified by the low noise amplifier, and is frequency-converted into a baseband signal by the LO wave having a phase difference of 90 degrees in the quadrature mixer.
After that, in the low-pass filter with variable bandwidth, the passband is variable according to several modes, and only the necessary baseband is extracted, and the variable gain amplifier amplifies it to support a wide dynamic range. Is done. Furthermore, after that, it is converted into a digital signal by an analog-digital converter, and signal processing is performed by a demodulator.
[0006]
[Non-Patent Document 1]
"Basics and Applications of Software Defined Radio" (August 1, 2002, Cypec, Junmichi Araki: Planning and Supervision, pages 76-78)
[0007]
[Problems to be solved by the invention]
As described above, the conventional direct conversion receiver requires the use of a variable low-pass filter in the multi-mode and multi-band basebands, which complicates the entire device and limits the filter variable range. Therefore, there is a problem that an arbitrary communication method cannot be supported.
[0008]
The present invention has been made to solve the above-described problems. The variable baseband filter in the direct conversion receiver is composed of a band-fixed baseband filter, so that it can be flexibly applied to various types of communication systems. It is an object of the present invention to obtain a direct conversion receiver that can handle the above.
[0009]
[Means for Solving the Problems]
  The direct conversion receiver according to the present invention is a direct conversion receiver corresponding to a plurality of systems having different signal bandwidths, and includes two frequency converters arranged in parallel for the received RF signal from the RF terminal, and a plurality of systems. A spreading code generating circuit for generating a corresponding spreading code, a mixer for generating a local oscillation signal by mixing a local oscillation wave and a spreading code for each frequency converter, and a local oscillation signal for each frequency converter. 90-degree phase difference means for distributing with a phase difference of degrees, a low-pass filter and an analog-digital converter fixed to the band individually connected to the output terminal of each frequency converter, and an output signal of each frequency converter Variable gain amplifier for variably amplifying the signal and the signal through each low-pass filter and each analog-digital converter Comprising a despreading circuit for performing spreading processing, and a demodulator for demodulating an output signal of the despreading circuit,The multiple systems include mobile phones or wireless LANs with different frequency bands and different modulation schemes, where the frequency bands and modulation schemes are known, and the local oscillation signal has a frequency in a known frequency band,The spreading code is a code that can be spread over a wider band than the band of the received RF signal, and each frequency converterWith spreading codeLocal oscillation signalModulateThe received RF signal is converted to a baseband signal having a fixed bandwidth by frequency conversion.The low-pass filter removes unwanted waves from the baseband signal and extracts only the necessary baseband band. The variable gain amplifier supports the baseband band with a wide dynamic range.The baseband signal is converted, and the despreading circuit and the demodulating unit despread and demodulate the baseband signal.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
Hereinafter, the first embodiment of the present invention will be described in detail with reference to the drawings.
1 is a block diagram showing a direct conversion receiver according to Embodiment 1 of the present invention.
[0011]
In FIG. 1, the direct conversion receiver includes a low noise amplifier 1 that amplifies an RF signal received from an RF terminal 10, and a quadrature mixer 2 connected to the output terminal of the low noise amplifier 1.
The orthogonal mixer 2 includes two unit mixers (frequency converters) 3a and 3b arranged side by side so as to have a phase difference of 90 degrees, and a 90 degree phase difference distributor provided in association with one unit mixer 3b. 4 (90-degree phase difference means).
The 90-degree phase difference distributor 4 distributes the local oscillation signal from the mixer 22 to the unit mixers 3a and 3b with a phase difference of 90 degrees.
[0012]
The output terminal of the quadrature mixer 2 includes a low-pass filter (LPF) 20 with a fixed band, a variable gain amplifier (AGC) 5 that variably amplifies an input signal, and an analog-digital converter (A / D) 6. A series circuit is connected.
This series circuit has a two-system circuit configuration that is individually connected to each unit mixer 3a, 3b.
The output terminal of each series circuit is connected to the demodulator 8 via the despreading circuit 7. The despreading circuit 7 performs despreading processing on the input signal, and the demodulator 8 demodulates the output signal of the despreading circuit 7.
[0013]
  The spread code generation circuit 21 generates a spread code corresponding to a plurality of systems.
  The mixer 22 mixes the local oscillation wave (LO wave) from the LO terminal 11 and the spread code from the spread code generation circuit 21 to generate a local oscillation signal for each unit mixer 3a, 3b.
  Each unit mixer 3a, 3b in the quadrature mixer 2 converts the received RF signal into a frequency based on the local oscillation signal from the mixer 22, thereby converting the received RF signal into a baseband signal having a fixed bandwidth. ing.
  As is well known, the spread code is applied to spectrum spreading such as frequency hopping and direct spreading. For example, in direct spreading, a pseudo-random noise code (PN code) is used as a spreading code to widen the frequency and transmission is usually performed at a noise level or lower. On the receiving side, the same code is used to demodulate the original code. Retrieve the signal. Note that PN codes include Gold sequences and M sequences, and various methods are used according to various systems.
Therefore, since the spreading code corresponding to a plurality of systems is determined according to the application, it is necessary to generate a plurality of spreading codes.
[0014]
Next, the operation according to the first embodiment of the present invention shown in FIG. 1 will be described with reference to the explanatory diagram of FIG.
In FIG. 2, the horizontal axis represents the frequency of the received wave, the vertical axis represents the baseband signal power after frequency conversion, and the baseband signal of the received wave having band A is shown.
Here, a receiver that receives signals from a plurality of systems with different frequency bands and different modulation schemes, such as a mobile phone and a wireless LAN, from the RF terminal 10 and switches as necessary to demodulate the signals of the desired system will be described.
[0015]
In FIG. 1, first, a low noise amplifier 1 amplifies a received wave (received RF signal) of a first frequency band and a modulation method, and unit mixers 3a and 3b in the quadrature mixer 2 have a phase difference of 90 degrees. The frequency is converted to a baseband signal using LO waves.
At this time, the LO wave (local oscillation signal) input to the quadrature mixer 2 is generated by the mixer 22.
[0016]
That is, the mixer 22 mixes the LO wave having the same frequency as the received wave of the first desired system with the first spreading code generated by the spreading code generation circuit 21, and uses the spread wave as a local oscillation signal. Generate.
This local oscillation signal is used for frequency conversion in the quadrature mixer 2, whereby the output signal from the quadrature mixer 2 is a baseband having a certain band A (see FIG. 2) wider than the band of the received wave. Signal.
[0017]
Subsequently, the band-fixed low-pass filter 20 removes unnecessary waves from the baseband signal and extracts only the necessary baseband band. Further, the variable gain amplifier 5 has a baseband corresponding to a wide dynamic range. Convert to signal.
The analog-digital converter 6 converts the baseband signal that has passed through the low-pass filter 20 and the variable gain amplifier 5 into a digital signal, the despreading circuit 7 performs despreading, and the demodulator 8 The baseband signal is demodulated by a simple signal processing.
[0018]
Next, the case where the received wave of the second frequency band and modulation method is demodulated will be described.
At this time, the LO wave input to the orthogonal mixer 2 is generated by the mixer 22 in the same manner as described above, and the mixer 22 generates an LO wave having the same frequency as the received wave of the second desired system. The signal is mixed with the second spreading code generated by the circuit 21 and a spread wave is generated as a local oscillation signal. This local oscillation signal is used for frequency conversion in the quadrature mixer 2, and an output signal from the quadrature mixer 2 becomes a baseband signal having a band A wider than the band of the received wave.
[0019]
Hereinafter, similarly, when demodulating the received wave of the third to Nth frequency bands and modulation schemes, the frequency of the LO wave is mixed with the third to Nth spreading codes, and the frequency is used. By performing the conversion, a baseband signal having the same band A can be obtained.
In this way, in a receiver that receives a plurality of systems, the baseband low-pass filter 20 is not a variable-band filter but a fixed-band filter, so that signals having various frequency bands are always in the same band. It can be converted to a baseband signal with A.
[0020]
Embodiment 2. FIG.
In the first embodiment (see FIG. 1), a local oscillation signal is generated using one system of spread code generation circuit 21 and mixer 22. However, as shown in FIG. A plurality of local oscillation signals may be generated using a mixer. FIG. 3 is a block diagram showing a direct conversion receiver according to Embodiment 2 of the present invention. Components similar to those described above (see FIG. 1) are denoted by the same reference numerals as those described above, or after the reference numerals. A detailed description is omitted with “A”.
[0021]
In FIG. 3, two systems of local oscillation signals are input to the unit mixers 3a and 3b in the orthogonal mixer 2A. Here, in order to simplify the drawing, a case where the local oscillation signal is typically two lines is shown, but it goes without saying that the number of arbitrary lines can be set.
In this case, in order to generate two systems of local oscillation signals, LO terminals 11a and 11b that receive two systems of LO waves, spread code generation circuits 21a and 21b that generate two systems of spread codes, and a mixture of the two systems Devices 22a and 22b.
In addition, 90-degree phase difference distributors 4a and 4b are inserted between the mixers 22a and 22b and the unit mixer 3b, respectively.
[0022]
Each spreading code generation circuit 21a, 21b generates a plurality of spreading codes corresponding to a plurality of systems, and the mixers 22a, 22b individually mix a plurality of local oscillation waves and a plurality of spreading codes corresponding to the plurality of systems. To generate a plurality of local oscillation signals.
Each unit mixer 3a, 3b performs frequency conversion of a plurality of received RF signals corresponding to a plurality of systems based on a plurality of local oscillation signals, and outputs a baseband signal.
[0023]
Next, the operation of the second embodiment of the present invention shown in FIG. 3 will be described with reference to the explanatory diagram of FIG.
FIG. 4 shows a state in which a plurality of (first and second) received waves overlap in the same band, and power is superimposed as a baseband signal having the same band A.
In this case as well, a receiver that receives a plurality of signals of different frequency bands and different modulation schemes such as a mobile phone and a wireless LAN and demodulates each signal simultaneously will be described.
[0024]
First, as described above, the low noise amplifier 1 amplifies the received wave of the first frequency band and the modulation method, and the quadrature mixer 2A performs frequency conversion based on the LO wave having a 90-degree phase difference, and the base Outputs a band signal.
At this time, the first LO wave input to the orthogonal mixer 2A is input from the LO terminal 11a.
[0025]
That is, the mixer 22a mixes the first LO wave having the same frequency as the received wave of the first desired system with the first spreading code from the spreading code generation circuit 21a, and the spread wave is a local oscillation signal. Generate as This local oscillation signal is used for frequency conversion in the quadrature mixer 2A, and an output signal from the quadrature mixer 2A becomes a baseband signal having a band A (see FIG. 4) wider than the band of the received wave.
In the same manner as described above, unnecessary waves are removed by the low-pass filter 20, a wide dynamic range can be handled by the variable gain amplifier 5, converted to a digital signal by the analog-digital converter 6, and despread by the despreading circuit 7. Spreading is performed, and the demodulator 8 demodulates the signal.
[0026]
Further, when demodulating the received wave of the second frequency band and modulation method, the second LO wave having the same frequency as the received wave of the second desired system is input from the LO terminal 11b, and in the mixer 22b, The signal is mixed and spread with the second spread code from the spread code generation circuit 21b, and input to the orthogonal mixer 2A as the second local oscillation signal.
Thus, the baseband signal frequency-converted by the orthogonal mixer 2A becomes a baseband signal having the band A.
[0027]
Hereinafter, similarly, when demodulating the received waves of the third to Nth frequency bands and modulation schemes, the waves that are spread by mixing the third to Nth LO waves with the third to Nth spreading codes are also used. By performing frequency conversion using, a baseband signal having the same band A can be generated.
In this manner, in a receiver that receives a plurality of systems, the baseband low-pass filter 20 is configured by a fixed-band filter so that signals having various frequency bands are always converted to baseband signals having the same band A. Can be converted.
Further, with the circuit configuration of FIG. 3, a plurality of signals can be simultaneously received and demodulated.
[0028]
Embodiment 3 FIG.
Although not particularly mentioned in the second embodiment (see FIG. 3), a plurality of (N) codes orthogonal to each other are generated as a plurality of spreading codes generated from each spreading code generation circuit. Also good.
For example, when the circuit configuration described above (see FIG. 3) is used, there is a possibility that interference occurs between the respective spread codes from the plurality of spread code generation circuits 21a and 21b. In order to avoid such interference between codes, it is desirable to generate codes orthogonal to each other from the respective spread code generation circuits 21a and 21b. Thereby, interference between codes can be suppressed.
[0029]
Embodiment 4 FIG.
In the first embodiment (see FIG. 1), the variable gain amplifier 5 is inserted between the low-pass filter 20 and the analog-digital converter 6. However, as shown in FIG. 5, the mixer 22 and the quadrature mixer are used. 2 (each unit mixer 3a, 3b) may be inserted a variable gain amplifier 23.
[0030]
FIG. 5 is a block diagram showing a direct conversion receiver according to Embodiment 4 of the present invention. Components similar to those described above (see FIG. 1) are denoted by the same reference numerals as those described above, or after the reference numerals. Detailed description is omitted with “B”.
In FIG. 5, a variable gain amplifier 23 is inserted between the mixer 22 and the quadrature mixer 2.
The variable gain amplifier 23 variably sets the power of the local oscillation signal in accordance with a plurality of systems under the control of the demodulator 8B.
[0031]
Next, the operation according to the fourth embodiment of the present invention shown in FIG. 5 will be described.
In this case as well, a receiver that receives a plurality of signals of different frequency bands and different modulation schemes such as a cellular phone and a wireless LAN, and switches them as necessary to demodulate those signals will be described.
First, the received wave of the first frequency band and the modulation method is amplified by the low noise amplifier 1, and the orthogonal mixer 2 performs frequency conversion to a baseband signal with an LO wave having a 90-degree phase difference.
[0032]
At this time, the first LO wave having the same frequency as the received wave of the first desired system is input from the LO terminal 11 and mixed with the first spreading code generated by the spreading code generation circuit 21 in the mixer 22. Then, the variable gain amplifier 23 generates a spread wave amplified by a desired gain as a local oscillation signal. This local oscillation signal is used for frequency conversion in the quadrature mixer 2, and an output signal from the quadrature mixer 2 becomes a baseband signal having a band A wider than the band of the received wave.
[0033]
In addition, since the power conversion gain when the received wave is frequency-converted to the baseband signal needs to be determined according to the LO wave power input to the mixer 2, the variable gain amplifier 23 has a desired conversion gain. The corresponding LO power is input to the orthogonal mixer 2.
Thus, by setting the LO power with the variable gain amplifier 23, it is possible to cope with a desired dynamic range.
[0034]
As described above, the frequency-converted baseband signal has a band A (see FIG. 2) wider than the band of the received wave.
Thereafter, unnecessary waves are removed through the band-fixed low-pass filter 20 and only the necessary baseband band is extracted, converted into a digital signal by the analog-digital converter 6, and despreaded by the despreading circuit 7. The demodulator 8 demodulates the signal.
Similarly, when demodulating the received wave of the Nth frequency band and modulation scheme, the variable gain amplifier 23 is set so that the LO power corresponding to the Nth received wave is obtained.
[0035]
In this way, by inserting the variable gain amplifier 23 between the mixer 22 and the quadrature mixer 2 and configuring the baseband low-pass filter 20 with a fixed-band filter, a plurality of systems can be obtained as described above. Can always generate a baseband signal of the same band A and convert it to a signal having the same level of power. Further, the variable gain amplifier 5 (see FIG. 1) can be eliminated in each baseband circuit.
[0036]
Embodiment 5 FIG.
In the second embodiment (see FIG. 3), the variable gain amplifier 5 is inserted between the low-pass filter 20 and the analog-digital converter 6, but as shown in FIG. 6, the mixers 22a and 22b Variable gain amplifiers 23a and 23b may be inserted between the quadrature mixer 2A (unit mixers 3a and 3b), respectively.
FIG. 6 is a block diagram showing a direct conversion receiver according to Embodiment 5 of the present invention. Components similar to those described above (see FIG. 2) are denoted by the same reference numerals as those described above, or after the reference numerals. A detailed description is omitted with “C”.
[0037]
In FIG. 6, variable gain amplifiers 23a and 23b are inserted between the mixers 22a and 22b and the quadrature mixer 2A (unit mixers 3a and 3b), respectively. The variable gain amplifiers 23a and 23b are configured to variably set the power of the local oscillation signal according to a plurality of systems under the control of the demodulator 8C.
The description of the operation according to the fifth embodiment of the present invention shown in FIG.
By using the variable gain amplifiers 23a and 23b similar to the variable gain amplifier 23 described above (see FIG. 5) side by side as many as the required number of LO waves, the present invention can be applied to a case where a plurality of signals are received simultaneously. The same effects as those of the fourth embodiment can be obtained.
[0038]
  In addition,In the first to fifth embodiments, the 90-degree phase difference distributor 4 (4a, 4b) is provided in the orthogonal mixer 2 (2A) as the 90-degree phase difference means. However, as shown in FIG. A 90-degree phase shifter 24 may be inserted on the output side of the circuit 21 (21a, 21b).
  FIG. 7 shows the present invention.Reference example 1 related toFIG. 6 is a block diagram showing a direct conversion receiver according to the above, and the same components as those described above (see FIG. 5) are denoted by the same reference numerals as those described above, or by adding “D” after the reference numerals. Omitted.
  Here, a case where the 90-degree phase shifter 24 is applied to the circuit configuration of the above-described fourth embodiment (see FIG. 5) will be typically described.
[0039]
In FIG. 7, the mixers 22c and 22d connected to the LO terminal 11 are configured by parallel circuits that generate individual local oscillation signals for the unit mixers 3a and 3b in the orthogonal mixer 2D.
A spread code 90-degree phase shifter 24 (90-degree phase difference means) is inserted between the spread code generation circuit 21D and one mixer 22d, and the other mixer 22c has a spread code generation. The output terminal of the circuit 21D is directly connected.
[0040]
Variable gain amplifiers 23c and 23d are inserted between the mixers 22c and 22d and the respective unit mixers 3a and 3b, and the variable gain amplifiers 23c and 23d are controlled by the demodulator 8D.
Each mixer 22c, 22d generates a local oscillation signal by mixing a local oscillation wave from the LO terminal 11 and a spread code having a phase difference of 90 degrees with each other, and passes through each variable gain amplifier 23c, 23d. Are input to the unit mixers 3a and 3b.
[0041]
  Next, as described above, the case of receiving a signal such as a mobile phone or a wireless LAN is shown in FIG.Reference example 1The operation of will be described.
  In this case, by using the 90-degree phase shifter 24 instead of the 90-degree phase difference distributor 4 described above, the mixers 22c and 22d have two parallel codes and a spread code having a phase difference of 90 degrees. The LO wave of the same phase is mixed and generated as a local oscillation signal (LO) for each unit mixer 3a, 3b in the quadrature mixer 2.
[0042]
Thereby, there can exist an effect similar to the case of the above-mentioned Embodiments 1-5.
In general, it is known that it is difficult to realize the 90-degree phase difference distributor 4 that can handle a wide band signal in the LO frequency or RF frequency band. However, by using the circuit configuration of FIG. A broadband orthogonal mixer 2D can be realized.
[0043]
  Reference example 1 aboveIn FIG. 7 (see FIG. 7), the 90-degree phase shifter 24 is applied to the circuit configuration of the above-described fourth embodiment (see FIG. 5). However, as shown in FIG. The 90-degree phase shifters 24a and 24b may be applied to the circuit configuration of 6).
  Figure 8Reference example 2FIG. 6 is a block diagram showing the direct conversion receiver according to FIG. 6. The same components as those described above (see FIG. 6) are denoted by the same reference numerals as those described above, or by adding “E” after the reference numerals. Omitted.
[0044]
In FIG. 8, a plurality (two) of LO terminals 11c and 11d are provided, and a plurality of (two each) mixers 22c1, 22c2, 22d1, and 22d2 are provided to the LO terminals 11c and 11d, respectively. It is connected.
Mixers 22c1 and 22d1 are connected to the LO terminal 11c, and mixers 22c2 and 22d2 are connected to the LO terminal 11d.
Further, variable gain amplifiers 23c1 and 23c2 are inserted between the mixers 22c1 and 22c2 and the unit mixer 3a, and variable gain amplifiers 23d1 and 23d2 are inserted between the mixers 22d1 and 22d2 and the unit mixer 3b. Has been inserted.
[0045]
The mixers 22c1 and 22c2 generate local oscillation signals for the unit mixer 3a, and the mixers 22d1 and 22d2 generate local oscillation signals for the unit mixer 3b.
The variable gain amplifiers 23c1, 23c2, 23d1, and 23d2 are controlled by the demodulator 8E.
[0046]
  A 90 degree phase shifter 24c is inserted between the spread code generating circuit 21c and the mixer 22d1, and a 90 degree phase shifter 24d is inserted between the spread code generating circuit 21d and the mixer 22d2. Yes.
  The output terminals of the respective spread code generation circuits 21c and 21d are directly connected to the mixers 22c1 and 22c2.
  The operation in this case is described above.Reference example 1Since it is the same as that, description is abbreviate | omitted.
[0047]
  The spread code generation circuits 21c and 21d and the 90-degree phase shifters 24c and 24d shown in FIG. 8 can be applied to simultaneous reception of a plurality of signals by using the necessary number of LO waves, respectively. ofReference example 1The same operational effects can be achieved.
[0048]
【The invention's effect】
  As described above, according to the present invention, two frequency converters arranged in parallel with respect to the received RF signal from the RF terminal, a spread code generation circuit that generates a spread code corresponding to a plurality of systems, and each frequency A mixer that generates a local oscillation signal by mixing a local oscillation wave and a spread code for the converter, and a 90-degree phase difference means for distributing the local oscillation signal to each frequency converter with a phase difference of 90 degrees from each other; Band-fixed low-pass filter and analog-digital converter individually connected to the output terminal of each frequency converter, variable gain amplifier for variably amplifying the output signal of each frequency converter, and each low-pass A despreading circuit that performs a despreading process on the signal via the filter and each analog-digital converter, and a demodulation unit that demodulates the output signal of the despreading circuitThe spreading code is a code that can be spread over a wider band than the band of the received RF signal,Each frequency converter frequency-converts the received RF signal based on the local oscillation signal, thereby converting the received RF signal into a baseband signal having a fixed bandwidth. The despreading circuit and the demodulation unit despread the baseband signal. Therefore, the variable baseband filter in the direct conversion receiver is configured with a fixed band baseband filter, so that a direct conversion receiver that can flexibly cope with various types of communication systems can be obtained. effective.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram showing a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing a baseband signal obtained according to Embodiment 1 of the present invention.
FIG. 3 is a block configuration diagram showing a second embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a baseband signal obtained according to Embodiment 2 of the present invention.
FIG. 5 is a block diagram showing a fourth embodiment of the present invention.
FIG. 6 is a block configuration diagram showing Embodiment 5 of the present invention.
FIG. 7Reference example 1 related toIt is a block block diagram which shows.
FIG. 8Reference example 2 related toIt is a block block diagram which shows.
[Explanation of symbols]
  2, 2A, 2D, 2E Quadrature mixer, 3a, 3b Unit mixer (frequency converter), 4, 4a, 4b 90 degree phase difference distributor, 5, 23, 23a-23d Variable gain amplifier, 6 Analog to digital converter, 7 Despreading circuit, 8, 8B-8E Demodulator, 10 RF terminal, 11, 11a-11d LO terminal, 20 Low-pass filter, 21, 21a-21d, 21D Spreading code generation circuit, 22, 22a-22d, 22c1, 22c2, 22d1, 22d2 mixer, 24 90 degree phase shifter.

Claims (4)

In direct conversion receivers that support multiple systems with different signal bandwidths,
Two frequency converters arranged in parallel for the received RF signal from the RF terminal;
A spreading code generating circuit for generating a spreading code corresponding to the plurality of systems;
A mixer that generates a local oscillation signal by mixing the local oscillation wave and the spread code for each frequency converter;
90 degree phase difference means for distributing the local oscillation signal to each frequency converter with a 90 degree phase difference from each other;
A band-fixed low-pass filter and an analog-digital converter individually connected to the output terminal of each frequency converter;
A variable gain amplifier for variably amplifying the output signal of each frequency converter;
A despreading circuit that performs a despreading process on the signal via each low-pass filter and each analog-digital converter;
A demodulator that demodulates the output signal of the despreading circuit,
The multiple systems include mobile phones or wireless LANs having different frequency bands and different modulation schemes, where the frequency bands and modulation schemes are known;
The local oscillation signal has a frequency in the known frequency band,
The spreading code is a code that can be spread over a wider band than the band of the received RF signal,
Each frequency converter modulates the local oscillation signal using the spreading code and converts the frequency of the received RF signal, thereby converting the received RF signal into a baseband signal having a fixed bandwidth,
The low-pass filter removes unnecessary waves from the baseband signal and extracts only a necessary baseband band,
The variable gain amplifier converts the baseband band into a baseband signal corresponding to a wide dynamic range ,
The direct conversion receiver, wherein the despreading circuit and the demodulation unit despread and demodulate the baseband signal. In direct conversion receivers that support multiple systems with different signal bandwidths,
Two frequency converters arranged in parallel for the received RF signal from the RF terminal;
A spreading code generating circuit for generating a spreading code corresponding to the plurality of systems;
A mixer that generates a local oscillation signal by mixing the local oscillation wave and the spread code for each frequency converter;
A variable gain amplifier for variably amplifying the output signal of the mixer;
90 degree phase difference means for distributing the local oscillation signal to each frequency converter with a 90 degree phase difference from each other;
A band-fixed low-pass filter and an analog-digital converter individually connected to the output terminal of each frequency converter;
A despreading circuit that performs a despreading process on the signal via each low-pass filter and each analog-digital converter;
A demodulator that demodulates the output signal of the despreading circuit,
The multiple systems include mobile phones or wireless LANs having different frequency bands and different modulation schemes, where the frequency bands and modulation schemes are known;
The local oscillation signal has a frequency in the known frequency band,
The variable gain amplifier is inserted between the mixer and each frequency converter, and under the control of the demodulator, variably sets the power of the local oscillation signal according to the plurality of systems,
The spreading code is a code that can be spread over a wider band than the band of the received RF signal,
Each frequency converter modulates the local oscillation signal using the spreading code and converts the frequency of the received RF signal, thereby converting the received RF signal into a baseband signal having a fixed bandwidth,
The low-pass filter removes unnecessary waves from the baseband signal and extracts only a necessary baseband band,
The variable gain amplifier converts the baseband band into a baseband signal corresponding to a wide dynamic range ,
The direct conversion receiver, wherein the despreading circuit and the demodulation unit despread and demodulate the baseband signal. The spreading code generating circuit generates a plurality of spreading codes corresponding to the plurality of systems;
The mixer generates a plurality of local oscillation signals by individually mixing a plurality of local oscillation waves corresponding to the plurality of systems and the plurality of spreading codes,
3. The direct conversion reception according to claim 1, wherein each of the frequency converters performs frequency conversion of a plurality of reception RF signals corresponding to the plurality of systems based on the plurality of local oscillation signals. Machine. The direct conversion receiver according to claim 3 , wherein the spreading code generation circuit generates a plurality of codes that are orthogonal to each other as the plurality of spreading codes.

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