Whar make harmonic suppression in antenna

[bkd]

hi
i want to suppress down the second( or third or both) harmonic in antenna. So what parameter make the second harmonic and third harmonic disaapear in antenna. The S parameter is enough ? ( the S_para is near 0 dB at second and the third harmonic ??), or we must simulate in HFSS and measure the dBi in the second and third harmonic. If the dBi is smaller than the reference antenna( at the same frequency) , then the antenna consider harmonic suppression ???
Thank you for you time and your help

 

[boy]

I think only s-parameter is enough since it is a pararamter that demtermine how much power go to the antenna.

 

[flatulent]

The fool proof method is to have a low pass filter in the transmission line. This should be a LC type.

 

[vfone]

Roll-off the gain of the antenna at harmonic frequencies it will help to generate less harmonics into the space.
Also, poor S11 of the antenna at harmonic frequencies it will reflect back to the transmitter part of the harmonics.

 

[pfm_pfm]

void FFT256(float dataR[],float dataR1[],float dataI[])
{
int x0,x1,x2,x3,x4,x5,x6,x7,xx;
int L,j,k,b,p;
uint i;
float TR,TI,temp,c,s;
float TR1,TI1,temp1;
for(i=0;i<256;i++)
{
x0=x1=x2=x3=x4=x5=x6=x7=0;
x0=i&0x01; x1=(i/2)&0x01; x2=(i/4)&0x01; x3=(i/8)&0x01;x4=(i/16)&0x01; x5=(i/32)&0x01; x6=(i/64)&0x01;x7=(i/128)&0x01;
xx=x0*128+x1*64+x2*32+x3*16+x4*8+x5*4+x6*2+x7;
dataI[xx]=dataR;
dataI[xx+256]=dataR1;
}
for(i=0;i<256;i++)
{
dataR=dataI; dataI=0;
dataR1=dataI[i+256]; dataI[i+256]=0;
}
for(L=1;L<=8;L++)
{
b=1; i=L-1;
while(i>0)
{b=b*2; i--;}
for(j=0;j<=b-1;j++)
{
p=1; i=8-L;
while(i>0)
{p=p*2; i--;}
p=p*j;
for(k=j;k<256;k=k+2*b)
{
c=cos_tab[p];
s=sin_tab[p];

TR=dataR[k]; TI=dataI[k]; temp=dataR[k+b];
TR1=dataR1[k]; TI1=dataI[k+256]; temp1=dataR1[k+b];

dataR[k]=dataR[k]+(dataR[k+b])*c+(dataI[k+b])*s;
dataI[k]=dataI[k]-(dataR[k+b])*s+(dataI[k+b])*c;
dataR[k+b]=TR-(dataR[k+b])*c-(dataI[k+b])*s;
dataI[k+b]=TI+temp*s-(dataI[k+b])*c;

dataR1[k]=dataR1[k]+(dataR1[k+b])*c+(dataI[k+b+256])*s;
dataI[k+256]=dataI[k+256]-(dataR1[k+b])*s+(dataI[k+b+256])*c;
dataR1[k+b]=TR1-(dataR1[k+b])*c-(dataI[k+b+256])*s;
dataI[k+b+256]=TI1+temp1*s-(dataI[k+b+256])*c;
}
}
}
for(i=0;i<32;i++)
{
TR=dataR;TI=dataI;
dataR=sqrt(TR*TR+TI*TI);
dataR=(dataR)/128;
dataR[i+128]=atan2(TR,TI)*180/PI;

TR1=dataR1;TI1=dataI[i+256];
dataR1=sqrt(TR1*TR1+TI1*TI1);
dataR1=(dataR1)/128;
dataR1[i+128]=atan2(TR1,TI1)*180/PI;
}
dataR[0]=dataR[0]/2;
dataR1[0]=dataR1[0]/2;
}

 

[bkd]

Oh thank
But how to roll-off the gain of an antenna. it seems difficult to know how in control the gain.

 

[VSWR]

As the poster above says, the best way is to have low pass filter in the transmission line to safely control and estimate the harmonic content of your radiating signal through your antenna.

Optimizing your antenna for "harmonic suppression" is a strange, uncommon and undesired approach. An antenna "is-what-it-is" in terms of "harmonic suppression", after optimizing more important key parameters such as gain, radiation pattern, VSWR at operational frequency band, mechanical dimensions, topology, etc.

 

[bkd]

Hum. If you add the low pass filter, it makes bigger size .

 

[predistorter]

hi, i have ever come across the topic before. as far as i know, only evaluating the s11 is not enough. besiees, the input impedance of the antenna at harmonic frequencies has to be almost reactive.

 

[bkd]

Oh thank you. I have read a paper of Cryan about this topic,. In this paper the input resisatance of harmonic suppression must be almost zero, it means that the imput impedance is amost reactive.
Have you ever designed any harmonic antenna.
Can we discuss together about this one more.
Thank you very much for your time and your help

 

[predistorter]

yeah, certainly, in what sense? what's your design applications? is it for active antennas?

 

[bkd]

Yes. I design harmonmic supression antenna and doing active antenna oscillator . I must compare the power of second harmonic of original non harmonic antenna ocsillator and the harmonic supression antenna oscillator. The differency now is 10 dB ( not so much). But it seems very hard to compress more. Because i think the input resistance of harmonic suppresion antenna is still high ( measurement is 15 Ohm). Simulation is good but fabrication is not so good, I must make more adjusment to the harmonic antenna to get the S para and input resistance to zero .
Can you give me more advice about how to compress the second harmonic in oscillator. It seems interdependence of both antenna and circuit.

 

[predistorter]

it seems we two are doing the same design now. for the ideas of supressing the harmonic power for you active osicllator antenna you can search for the papers in ieee or wiley website. i am sure there are quite a few papers tackling this problem. what type of your antenna is it like? if it is a rectangular patch, you can use shorting pins to kill the second harmonic. regards

 

[bkd]

I do not doing in the rectagular patch . I doing in the slot antenna. The second harmonic power level seems unstable and sensitive. I am crazy with it. Can you give me the MSN or YH ID. My YH is nnanh_peace and my MSN is nnanh_peace@yahoo.com
We can discuss mote to get more experience.
Best regard

 

[bkd]

I am successful in designing harmonic suppression for some wide band slot antenna. But prof ask me to build the equivalent circuit for these. Oh my God. Does anyone have experience in building equivalent circuit with ADS.