CN103138713A - Reconfigurable complex filter and implementation method - Google Patents

Abstract

The invention discloses a reconfigurable complex filter and an implementation method and relates to the electronic technique. The method comprises setting center frequency and cut-off frequency in all operating modes of the filter to be equal proportional relation, so that the center frequency and the cut-off frequency can be changed simultaneously by changing capacitances of nodes of the filter, and the reconfigurable function is further achieved. According to the method, trans-conductance in all operation modes is maintained to be unchangeable, and parameters of the center frequency and the cut-off frequency of the filter can be adjusted simultaneously by only adjusting one parameter of the node capacitances; and compared with the prior art, the design of the reconfigurable complex filter is simplified.

Description

A kind of restructural complex filter and implementation method

Technical field

The present invention relates to electronic technology field, relate in particular to and a kind ofly change the centre frequency of filter and restructural complex filter and its implementation of cut-off frequency by control capacitance.

Background technology

Complex filter is due to its asymmetrical frequency characteristic, be widely used in wireless receiver to suppress image signal, its principle is to utilize the complex field computational methods, real filter is configured to a single sideband filter, be characterized in only having the logical selecting frequency characteristic of band in positive frequency or negative frequency, namely frequency characteristic is asymmetric.

Along with developing rapidly of radio communication, the kind of communication protocol also sharply increases, and increasing wireless communication protocol is used for for various communications applications.How on same terminal, integratedly can adapt to the telecommunication circuit that various protocols requires, and satisfy different communication requirements by convenient, flexible switching, become gradually study hotspot and the development trend of wireless communication field.Corresponding, the complex filter that is applied to wireless receiver is not that requirement can suppress image signal, and also requirement can be adjusted the frequency characteristic of filter in real time, to satisfy the requirement of different agreement.

The passive image-reject filter of traditional Order RC as shown in Figure 1, the centre frequency of filter This RC filter applies to realizes existing a plurality of difficult problems in integrated circuit.At first, R ₀, C ₀Require accurately to obtain accurate centre frequency, this is difficult to realize in integrated circuit; Secondly, can't change the size of resistance or the electric capacity of place in circuit, adjust the centre frequency of filter; In addition, the passive RC network loss is larger, the low-frequency noise poor performance.

Chinese patent literature 200720109276.9 discloses a kind of reconfigurable complex filter, and its schematic diagram as shown in Figure 2.It adjusts centre frequency and the cut-off frequency of filter by changing mutual conductance, realize but must be controlled by two groups of different control words, has increased the complexity of design.

Because the centre frequency of complex filter is non-vanishing, therefore adjust the frequency characteristic of complex filter, mean that its centre frequency and cut-off frequency must change simultaneously.The restructural of complex filter is realized at present, mainly comprise and change passive device and change two kinds of methods of active device, must realize by different control words but change in the time of centre frequency and cut-off frequency, greatly increase the design complexities of restructural complex filter.Therefore, prior art has yet to be improved and developed.

Summary of the invention

The object of the present invention is to provide a kind of restructural complex filter and its implementation, for the non-vanishing characteristics of complex filter centre frequency, provide a kind of implementation method that only can adjust simultaneously the restructural complex filter of centre frequency and cut-off frequency by one group of control word.

The present invention adopts following technical solution to achieve these goals:

A kind of restructural complex filter, it comprises the signal path of two-way quadrature, and is positioned at one group of outer mutual conductance gyrator of path, each signal path is comprised of trsanscondutor, node capacitor; The word size-controlled processed of node capacitor is controlled adjustable, with the different filter mode of operation of correspondence; Each trsanscondutor all remains unchanged under different mode of operations; Centre frequency under each mode of operation of filter becomes the equal proportion relation with cut-off frequency.

Described restructural complex filter, the signal path of its described two-way quadrature, setting parallel with one another between two signal paths, is connected through one group of mutual conductance gyrator.

Described restructural complex filter, its described each node capacitor comprises three capacitor C a, Cb, Cc and three switch S 0, S1, S2 that metal-oxide-semiconductor forms, and an electric capacity is connected with a switch, three electric capacity outer end contacts connect the node on signal path, three switch outer end contact ground connection; Switch S 0 grid connects high level and remains conducting, and switch S 1, S2 grid meet respectively control word A1, A2, and A1, A2 control the size of node capacitor by the open and close of control switch S1, S2.

Described restructural complex filter, the node capacitor of mode of operation 1 correspondence is Ca+Cb+Cc, and the node capacitor of mode of operation 2 correspondences is Ca+Cb, and the node capacitor of mode of operation 3 correspondences is Ca.

A kind of implementation method of restructural complex filter, it comprises the following steps:

Steps A, centre frequency and cut-off frequency under each mode of operation of filter are set, make centre frequency become the equal proportion relation with cut-off frequency;

In step B, maintenance filter, each trsanscondutor is constant;

Step C, control each node capacitor of filter with control word, make each node capacitor of filter adjustable;

Step D, selection control word are with the corresponding mode of operation of correspondence.

Described implementation method, its described step C changes node capacitor, changes when namely realizing filter center frequency and cut-off frequency.

A kind of restructural complex filter of the present invention and implementation method, utilize the equal proportion relation of centre frequency and cut-off frequency, can change simultaneously centre frequency and cut-off frequency by changing node capacitor, realize reconfigurable function, compared with prior art, the perfect function of restructural complex filter, and simplicity of design.

Description of drawings

Fig. 1 is the circuit theory diagrams of the traditional passive image-reject filter of Order RC;

Fig. 2 is the circuit theory diagrams of known reconfigurable complex filter;

Fig. 3 is a kind of restructural complex filter circuit theory diagrams of the present invention.

Embodiment

Below by embodiment, and by reference to the accompanying drawings, technical scheme of the present invention is elaborated.

Embodiment 1: a kind of restructural complex filter circuit theory diagrams of the present invention comprise the signal path of the quadrature that two route trsanscondutors, node capacitor form and are positioned at one group of outer mutual conductance gyrator of path as shown in Figure 3; The setting parallel with one another of the signal path of two-way quadrature between two signal paths, is connected through the mutual conductance gyrator; Each node capacitor in signal path, comprise three capacitor C a, Cb, Cc and three switch S 0, S1, S2 that metal-oxide-semiconductor forms, one electric capacity is connected with a switch, three electric capacity outer end contacts connect the node on signal path, three switch outer end contact ground connection, switch S 0 grid connects high level and remains conducting, and switch S 1, S2 grid meet respectively control word A1, A2, A1, A2 control the size of node capacitor by the open and close of control switch S1, S2, thus corresponding different mode of operations; Wherein, the node capacitor of mode of operation 1 correspondence is Ca+Cb+Cc, and the node capacitor of mode of operation 2 correspondences is Ca+Cb, and the node capacitor of mode of operation 3 correspondences is Ca; Each trsanscondutor all remains unchanged under different mode of operations; Centre frequency f under each mode of operation of filter _oi(i=1 ..., n) with cut-off frequency f _ci(i=1 ..., n) become the equal proportion relation, n=3 in the present embodiment, that is:

$\frac{f_{o1}}{{\mathrm{<figure-callout\; id="1"\; label="f\; c"\; filenames="HDA0000110891890000021.png"\; state="\{\{state\}\}">f</figure-callout>}}_c}=\frac{f_{o2}}{f_{c2}}=\frac{f_{o3}}{f_{c3}}---\left(1\right)$

In the present embodiment, filter is five rank complex filters.According to the relevant knowledge of filter, each node capacitor:

$C_i=\frac{{\mathrm{\&tau;}}_i\&CenterDot;G_m}{2\mathrm{\&pi;}{f}_c}$ (i＝1，…，5) (2)

The cross-couplings mutual conductance:

G _mi＝2πf _o·C _i (i＝1，…，5) (3)

In formula, τ _i(i=1 ..., 5) and constant for being determined by type and the exponent number of filter, G _mBe the mutual conductance on signal path, f _cBe cut-off frequency, f _oCentered by frequency.

Therefore, for mode of operation 1, formula (2), (3) become respectively:

$C_{1i}=\frac{{\mathrm{\&tau;}}_i\&CenterDot;G_m}{{2\mathrm{\&pi;f}}_{c1}}$ (i＝1，…，5) (4)

G _m1i＝2πf _o1·C _1i (i＝1，…，5) (5)

In formula, C _1i(i=1 ..., 5) and be each node capacitor in pattern 1, f _c1Be the cut-off frequency in pattern 1, f _o1Be the centre frequency in pattern 1.

For mode of operation 2, formula (3) becomes:

$G_{m2i}=2\mathrm{\&pi;}{f}_{o2}\&CenterDot;C_{2i}=\frac{f_{o2}\&CenterDot;{\mathrm{\&tau;}}_i\&CenterDot;G_m}{f_{c2}}---\left(6\right)$

According to formula (1), formula (6) becomes:

$G_{m2i}=\frac{f_{o2}\&CenterDot;{\mathrm{\&tau;}}_i\&CenterDot;G_m}{f_{c2}}=\frac{f_{o1}\&CenterDot;{\mathrm{\&tau;}}_i\&CenterDot;G_{\mathrm{<figure-callout\; id="1"\; label="m\; f\; c"\; filenames="HDA0000110891890000021.png"\; state="\{\{state\}\}">m</figure-callout>}}}{f_c}=2\mathrm{\&pi;}{f}_{o1}\&CenterDot;C_{1i}=G_{m1i}---\left(7\right)$

Can find out, even change centre frequency and the cut-off frequency of filter by changing node capacitor, its mutual conductance still remains unchanged, and has therefore greatly simplified the design of restructural filter.

In the present embodiment, the centre frequency under three kinds of mode of operations is respectively f _o1, f _o2, f _o3(f _o1＜f _o2＜f _o3), the cut-off frequency under pattern 1 is f _o1, according to formula (1), the cut-off frequency under pattern 2,3 is respectively

According to formula (2), C _1i＞C _2i＞C _3i, (i=1 ..., 5), see form 1 for details.

Centre frequency and cut-off frequency under form 1 each mode of operation

The present invention can realize the centre frequency to filter, the control of cut-off frequency by one group of control word, realizes the restructural of complex filter, and simplicity of design, satisfies the demand for development of wireless lan communication lsi.

Claims (6)

1. a restructural complex filter, is characterized in that, comprises the signal path of two-way quadrature, and be positioned at one group of outer mutual conductance gyrator of path, and each signal path is comprised of trsanscondutor, node capacitor; The word size-controlled processed of node capacitor is controlled adjustable, with the different filter mode of operation of correspondence; Each trsanscondutor all remains unchanged under different mode of operations; Centre frequency under each mode of operation of filter becomes the equal proportion relation with cut-off frequency.

2. restructural complex filter according to claim 1, is characterized in that, the signal path of described two-way quadrature, and setting parallel with one another between two signal paths, is connected through one group of mutual conductance gyrator.

3. restructural complex filter according to claim 1, it is characterized in that, described each node capacitor, comprise three capacitor C a, Cb, Cc and three switch S 0, S1, S2 that metal-oxide-semiconductor forms, one electric capacity is connected with a switch, three electric capacity outer end contacts connect the node on signal path, three switch outer end contact ground connection; Switch S 0 grid connects high level and remains conducting, and switch S 1, S2 grid meet respectively control word A1, A2, and A1, A2 control the size of node capacitor by the open and close of control switch S1, S2.

4. restructural complex filter according to claim 3, is characterized in that, the node capacitor of mode of operation 1 correspondence is Ca+Cb+Cc, and the node capacitor of mode of operation 2 correspondences is Ca+Cb, and the node capacitor of mode of operation 3 correspondences is Ca.

5. the implementation method of a restructural complex filter, is characterized in that, comprises the following steps:

Steps A, centre frequency and cut-off frequency under each mode of operation of filter are set, make centre frequency become the equal proportion relation with cut-off frequency;

In step B, maintenance filter, each trsanscondutor is constant;

Step C, control each node capacitor of filter with control word, make each node capacitor of filter adjustable;

Step D, selection control word are with the corresponding mode of operation of correspondence.

6. implementation method according to claim 5, is characterized in that, described step C changes node capacitor, changes when namely realizing filter center frequency and cut-off frequency.

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