CDMA2000 1X接收端滤波器的设计

天山苍雪

CDMA2000 滤波器有三部分：

1.发送端基带滤波器

文献4 对基带滤波器的要求及系数：（p450）

该滤波器系数已知，为h_k。

2.发送端均衡滤波器

求解he（先用的已知的y）

根据文献2：

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% 此处用的四倍，由频域转到Z域代码：

w0=2*pi*3.15*100000;

[b, a] = bilinear([-1,1.36*w0,-w0*w0],[-1,-1.36*w0,-w0*w0],1.2288*4*10e5);

[he,n]=impz(b,a);

生成的he为36阶。

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3.接收端补偿滤波器

文献1给出了接收端滤波器的设计方法，介绍了求补偿滤波器hc的方法。三个滤波器卷积之后应满足：

hk*he*hc=RC filter

先求前两个卷积：y=hk*he。文献1介绍了方法。此处先用已知的y。

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http://www.edaboard.com/thread127909.html

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h_k=[ -0.0253

   -0.0342

   -0.0358

   -0.0167

    0.0216

    0.0649

    0.0910

    0.0819

    0.0371

   -0.0220

   -0.0607

   -0.0512

    0.0079

    0.0844

    0.1269

    0.0945

   -0.0128

   -0.1435

   -0.2118

   -0.1405

    0.0946

    0.4414

    0.7859

    1.0000

    1.0000

    0.7859

    0.4414

    0.0946

   -0.1405

   -0.2118

   -0.1435

   -0.0128

    0.0945

    0.1269

    0.0844

    0.0079

   -0.0512

   -0.0607

   -0.0220

    0.0371

    0.0819

    0.0910

    0.0649

    0.0216

   -0.0167

   -0.0358

   -0.0342

   -0.0253];

%%%%%%%%%%%%%%%%

w0=2*pi*3.15*100000;

[b, a] = bilinear([-1,1.36*w0,-w0*w0],[-1,-1.36*w0,-w0*w0],1.2288*4*10e5);

[he,n]=impz(b,a);

Hk=fft(h_k,128);

He=fft(he,128);

Y1=Hk.*He;

y1=ifft(Y1,128);

y=y1(1:70);

%%%%%%% RC

z=rcosine(1,4,'normal',0,14);

%%%%%%% Kaiser window using matlab built-in function kaiser()

N=113; beta = 6.65;

w = kaiser(N, beta);

w = w';

% Apply Kaiser window w to RC filter z

zw = z.*w; zw=zw.';

Hz=fft(zw,128);

Hy=fft(y,128);

H=Hz./Hy;

hc=ifft(H,128);

%%%%%%%%%%%%%验证

% a=conv(y,hc);

% b=1;

% figure(2)

% plot(a);hold on;

% plot(b:4:length(a),a(b:4:end),'+r');

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文献4对性能要求（p116）:

验证过程：(时域/用fvtool(a)看幅度，相位，群延时)

三个滤波器卷积之后验证是否满足奈奎斯特定理。

RC = hk*he*hc = y*hc

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

% a=conv(y,hc);

% b=1;

% figure(2)

% plot(a);hold on;

% plot(b:4:length(a),a(b:4:end),'+r');

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

用fvtool(a)看幅度，相位，群延时。

参考文献：

1.《Complementary Filter Design for Testing of IS-95 Code   Division Multiple Access Wireless Communication Systems》

2.《Receiver Architectures for CDMA2000 1 xEV-DV Mobile  Terminals including Phase Compensated  Filtering》

3.《Recommended Minimum Performance Standards for cdma2000 Spread Spectrum Base Stations》

4.《Physical Layer Standard for cdma2000 Spread Spectrum Systems》