JP2011066836A - Wireless receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless receiver in which a noise figure is improved. <P>SOLUTION: A wireless receiver comprises a plurality of amplifiers A1-A4, which are connected on multiple stages, each for amplifying a base band signal and a high-pass filter F2 is included in a feedback path of the first-stage amplifier A1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless reception device, and more particularly to an amplification technique in a wireless reception device such as a portable terminal.

  An example of a wireless reception device such as a portable terminal is disclosed in Patent Document 1. In FIG. 3, a signal received from the external antenna of the terminal device is differentially amplified by the low noise amplifier 301 and divided into two. After the DC component is cut (C cut) by the capacitor, the orthogonal mixer 302 performs down conversion from the RF signal to the baseband signal at once. At this time, a signal obtained by distributing the local oscillation (LO) signal from the local oscillator 304 into the in-phase component and the quadrature component by the divider 303 is mixed with the RF signal, so that each baseband is in quadrature with the in-phase (I) component. A signal of component (Q) is generated. From these baseband signals, the low-pass filter (LPF) 305 removes the signal power of interference waves such as adjacent channels, and extracts only the desired wave signal.

  The 3-wire serial digital data 312 is set and decoded by the PGA control circuit 311 to discretely switch the gain of the baseband amplifier 306 that amplifies the baseband signal. The DC offset canceller circuit 310 is a circuit that detects a DC component at the final stage of the baseband amplifier and cancels the DC offset by applying an analog negative feedback. The LPF 307 at the subsequent stage of the baseband amplifier 306 is a filter inserted so that the 50% roll-off characteristic downlink signal on the transmission side has a 100% roll-off characteristic as a total transfer function. After the S / N of the baseband signal is maximized by the LPF 307, the A / D converter 308 performs quantization and converts the analog signal into a digital signal.

  Here, the low-pass filter 305 is generally composed of an active filter. FIG. 4 is a diagram illustrating a configuration of an active filter disclosed in Non-Patent Document 1 and the like. In FIG. 4, the active filter is composed of a passive network NT1 and an amplifier A100 having an amplification degree K, and receives a V1 signal and outputs a V2 signal.

JP 2005-94178 A

Lawrence P. Huelsman, “Active and Passive Analog Filter Design”, McGraw-Hill College, 1993, P246

  The following analysis is given in the present invention.

In a conventional wireless receiver, a baseband signal is amplified by a multistage cascaded amplifier including a low pass filter (LPF) 305, a baseband amplifier 306, and an LPF 307. NFtotal, which is the NF (noise figure) of the entire receiving apparatus composed of such multistage cascaded amplifiers, is G1 for the amplification factor of the first stage and N1 for amplification factor of the first and second stages. Where G2 is NF, N2 is NF,... Gn is the amplification factor in the nth stage, and Nn is NF.
NFtotal = N1 + (N2-1) / G1 + (N3-1) / G1 · G2 +... + (Nn−1) / G1 · G2... Gn —— (Formula 1)

  According to Equation 1, the value of N1 in the first term has the greatest influence on NFtotal, and the smaller NFtotal is, the smaller NFtotal can be. Moreover, it is shown that the value after the second term can be decreased as the amplification factor G1 is increased from the second term.

  When the low-pass filter 305 is composed of an active filter as shown in FIG. 4, if the gain of the pass band is increased, the stability of the active filter itself deteriorates. For this reason, it is difficult to increase the gain of the passband corresponding to G1 in consideration of the stability. Further, since the thermal noise generated by the resistance element inserted in series in the passive network NT1 is amplified, the NF of the active filter is deteriorated. Therefore, the value of N1 shown in Equation 1 increases and G1 decreases, so that NFtotal becomes a large value.

  A radio reception apparatus according to an aspect of the present invention includes a plurality of amplifiers connected in multiple stages for amplifying a baseband signal, and includes a high-pass filter unit in a feedback path of the first-stage amplifier.

  According to the present invention, since the high-pass filter unit is included in the feedback path of the first-stage amplifier, the noise figure is improved.

It is a block diagram which shows the structure of the radio | wireless receiver which concerns on 1st Example of this invention. It is a circuit diagram of the principal part of the radio | wireless receiver which concerns on 1st Example of this invention. It is a block diagram which shows the structure of the conventional radio | wireless receiving apparatus. It is a figure which shows the structure of the conventional active filter.

  The wireless receiver according to the embodiment of the present invention includes a plurality of amplifiers (A1 to A4 in FIG. 1) connected in multiple stages for amplifying a baseband signal, and is in the feedback path of the first-stage amplifier (A1 in FIG. 1). A high-pass filter unit (F2 in FIG. 1) is included.

  In the wireless reception device, the high-pass filter unit may include a high-pass filter (HP1 in FIG. 2) and a buffer circuit (Buf1 in FIG. 2) that buffers the output of the high-pass filter.

  In the wireless reception device, the high-pass filter may be composed of passive elements.

  In the wireless receiver, at least a part of the plurality of amplifiers is a variable gain differential amplifier including a pair of MOS transistors and a current supply circuit commonly connected to the sources of the MOS transistors. The gain may be controlled by changing the current. The current supply circuit may be a variable current source (I1 in FIG. 2).

  According to the radio receiving apparatus as described above, the gain can be easily increased by the amplifier at the first stage, so that G1 expressed by Equation 1 can be increased. Further, since the thermal noise generated by the resistance element inserted in series in the passive network, such as the active filter which is the first stage configuration of the prior art, is not amplified, the formula 1 is more than the prior art. N1 shown can be reduced. Therefore, the NFtotal represented by Equation 1 can be made smaller in the present invention.

  Hereinafter, it will be described in detail with reference to the drawings in accordance with embodiments.

  FIG. 1 is a block diagram showing a configuration of a radio receiving apparatus according to the first embodiment of the present invention. In FIG. 1, the radio reception apparatus includes an antenna ANT, a low noise amplifier L1, a local oscillator VCO, a mixer M1, variable gain amplifiers A1 to A4, a low-pass filter F1, an amplifier B1, and a high-pass filter F2.

  An antenna ANT for signal reception is connected to the mixer M1 via the low noise amplifier L1. The mixer M1 is connected to the low noise amplifier L1 and the local oscillator VCO as inputs and output to the variable gain amplifier A1. A high-pass filter F2 is connected to the output of the variable gain amplifier A1. The output of the high pass filter F2 is connected to the input of the variable gain amplifier A1. Further, the output of the variable gain amplifier A1 is amplified via the cascaded variable gain amplifiers A2, A3, and A4, and is output to the low-pass filter F1 that performs band selection. The output of the low-pass filter F1 is connected to the amplifier B1. The output of the amplifier B1 is connected to an AD converter not shown.

  Next, the operation of the wireless reception device will be described. In FIG. 1, an RF band received signal input from an antenna ANT for signal reception is amplified by a low noise amplifier L1. The amplified received signal is input to the mixer M1, and is subjected to frequency conversion (down-conversion) by a local oscillation signal (LO signal) generated by the local oscillator VCO.

  With the configuration in which the high-pass filter F2 is arranged as a feedback unit in the variable gain amplifier A1, only the interference wave and unnecessary spurious are extracted from the frequency-converted signal by the high-pass filter F2, and are added to the input of the variable gain amplifier A1 in reverse phase. With such a configuration, interference waves and unnecessary spurious at the output of the variable gain amplifier A1 are reduced.

  The signal output from the variable gain amplifier A1 is adjusted to the input level required by the AD converter including the gains of the variable gain amplifiers A2, A3, A4, the low-pass filter F1, and the amplifier B1, and is sent to an AD converter (not shown). A signal is sent. The gains of the variable gain amplifiers A1 to A4 can be changed by a control signal (not shown).

  Next, specific configuration examples of the variable gain amplifiers A1 to A4 and the high-pass filter F2 that are main parts of the wireless reception device will be described. FIG. 2 is a circuit diagram of the main part of the radio receiving apparatus according to the first embodiment of the present invention. In FIG. 2, the variable gain amplifier A1 includes NMOS transistors MN1 and MN2, resistance elements R1 and R2, and a variable current source I1 that form a differential pair. The NMOS transistor MN1 has a drain connected to the power supply VDD via the resistor element R1 and one output terminal, a source connected to the other end of the variable current source I1 whose one end is grounded, and a gate connected to one input. Connect to the end. The NMOS transistor MN2 has a drain connected to the power supply VDD via the resistor element R2 and is connected to the other output terminal, a source connected to the other end of the variable current source I1, and a gate connected to the other input terminal. The variable current source I1 has a current value that can be changed by the control signal Vct, and can adjust the gain in the variable gain amplifier A1. Note that a variable resistor may be used instead of the variable current source I1, which is a current supply circuit. In this case, the resistance element may be switched by the switch element so that the gain in the variable gain amplifier A1 can be adjusted.

  The variable gain amplifiers A1 to A4 are usually all configured the same. However, the variable gain amplifier A1 includes a feedback path, and includes a high-pass filter HP1, a buffer Buf1, and capacitive elements C1 and C2 in the feedback path. The high pass filter HP1 may be configured by a passive element such as an LCR. If there is no problem such as impedance mismatch even if the output of the high pass filter HP1 is directly connected to the input of the variable gain amplifier A1, the buffer Buf1 may be omitted. Furthermore, the high pass filter HP1 is not limited to a passive filter, and may be an active filter.

  One and the other input ends of the variable gain amplifier A1 receive differential signals In1 and In2 output from the mixer M1, and are connected to one ends of the capacitive elements C1 and C2, respectively. One and the other output terminals of the variable gain amplifier A1 are connected to one and the other input terminals of the variable gain amplifier A2, respectively, and are connected to a pair of input terminals of the high-pass filter HP1. A pair of output ends of the high-pass filter HP1 are connected to the other ends of the capacitive elements C1 and C2, respectively, via the buffer Buf1.

  Variable gain amplifiers A1 to A4 are cascaded in multiple stages, and output differential signals Out1 and Out2 from one and the other output terminals of variable gain amplifier A4 to low-pass filter F1.

  As described above, by including the high-pass filter F2 in the feedback path of the variable gain amplifier A1, the gain can be easily increased by the variable amplifier A1, so that G1 in Expression 1 can be increased. In addition, since the thermal noise generated by the resistance element inserted in series in the passive network such as the active filter which is the first stage configuration of the prior art is not amplified, the first stage NF is higher than the prior art. Can be reduced.

  Therefore, the value of N1 in the first stage is smaller in the present invention than in the conventional technique, and the value of G1 in the first stage is larger in the present invention than in the conventional technique. That is, if applied to Equation 1, NFtotal can be made smaller in the present invention than in the prior art.

  It should be noted that the disclosures of the aforementioned patent documents and the like are incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiments and examples can be changed and adjusted based on the basic technical concept. Various combinations and selections of various disclosed elements are possible within the scope of the claims of the present invention. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea.

ANT antenna L1 low noise amplifier VCO local oscillator M1 mixer A1, A2, A3, A4 variable gain amplifier F1 low pass filter F2 high pass filter B1 amplifier MN1, MN2 NMOS transistor R1, R2 resistance element I1 variable current source HP1 high pass filter Buf1 buffer C1, C2 capacitive element

Claims (5)

A plurality of amplifiers connected in multiple stages for amplifying a baseband signal are provided.
A radio receiving apparatus comprising a high-pass filter section in a feedback path of the amplifier at the first stage.   The radio reception apparatus according to claim 1, wherein the high-pass filter unit includes a high-pass filter and a buffer circuit that buffers an output of the high-pass filter.   The radio reception apparatus according to claim 2, wherein the high-pass filter includes a passive element. At least some of the plurality of amplifiers are
A pair of MOS transistors;
A current supply circuit commonly connected to the sources of the MOS transistors;
A variable gain differential amplifier comprising:
The radio receiving apparatus according to claim 1, wherein the gain is controlled by changing a current of the current supply circuit.   The radio reception apparatus according to claim 4, wherein the current supply circuit is a variable current source.

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