# how to design a 50 ohm feed line for a patch antenna

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#### neocw

##### Newbie level 4
50 ohm feed line

my patch antenna dimension is 37.74mm x 37.74mm, operating around 2.45GHz.
Substrate permittivity is 2.45, substrate height is 1.524mm, loss tangent is 0.0019, copper thickness is 0.035mm

Can anyone out there advice on the feed line dimension for above design? How should I go about designing it?

I intend to use a 50 ohm sma connector as source probe.

Thanks.

#### Element7k

50ohm patch antenna

Use calculator on:

Cheers,
Element7k

neocw said:
my fix antenna dimension is 37.74mm x 37.74mm, operating around 2.45GHz.
Substrate permittivity is 2.45, substrate height is 1.524mm, loss tangent is 0.0019, copper thickness is 0.035mm

Can anyone out there advice on the feed line dimension for above design? How should I go about designing it?

I intend to use a 50 ohm sma connector as source probe.

Thanks.

designing a 50 ohm antenna

Edge or coaxial feed?

#### neocw

##### Newbie level 4
feeder line calculation

Hi all,

the feeding method is edge fed.

#### neocw

##### Newbie level 4
designing a 50 ohm feedline

I tried the calculator, it only give the line width but not the length.

Element7k said:
Use calculator on:

Cheers,
Element7k

neocw said:
my fix antenna dimension is 37.74mm x 37.74mm, operating around 2.45GHz.
Substrate permittivity is 2.45, substrate height is 1.524mm, loss tangent is 0.0019, copper thickness is 0.035mm

Can anyone out there advice on the feed line dimension for above design? How should I go about designing it?

I intend to use a 50 ohm sma connector as source probe.

Thanks.

#### qiang

##### Member level 2
50 ohm feedline

it's sure that the 1/4 lamada transformer is needed to transform the input risistence to 50

#### peter-gr

##### Member level 1
patch antenna calculator for probe feed

Does the length of the feed line plays a specicific role?What is this role?I thought only the width plays role for input resistance of the feed line of a patcha antenna.

#### mr_ghz

##### Full Member level 5
patch antenna feeding calculator

You have to move the impedance of your (ptach)-antenna to 50 ohms. After this you can connect your 50 ohm line (specified by the width of your trace). The length doesn't play a role (only losses will increase).

But how can you move the impedance of your antenna? You can use a lambda/4 transformer, but it will be a very thin trace in your design. The better way is to move the feedpoint to the middle of the antenna. You can simulate it very easy with an EM simulator like ADS or Ensemble.

Bye

Amrutha M K

### Amrutha M K

Points: 2

#### cancel

##### Full Member level 5
50 ohm line calculator

try appcad from agilent .. it is free cad/calculator for lines etc.

Amrutha M K

### Amrutha M K

Points: 2

#### Element7k

patch antenna feedline calc

My apologies. I just read the title and assume that all you wanted was a 50ohm stripline. I didn't realised u wanted an edge fed p@tch.

My ghz is right, if you only have one section 1/4 transformer, it will be very thin. Your antenna's input impedance is about 400 ohms. If connected to the centre of the p@tch and a 1 section 1/4 transformer, I roughly calculated the width of the strip line as 0.26mm and L=22.52mm. After this strip, you can connect to the 4.4mm thick 50ohm stripline (Arbitrary length). You can try to used multiple impedance transformer (e.g. 50-75m 75-125,etc) to thicken the line. Otherwise, why not try an insert-feed?

Cheers,
Element7k

neocw said:
I tried the calculator, it only give the line width but not the length.

Amrutha M K

### Amrutha M K

Points: 2

#### nanjingchenbing

##### Newbie level 4
impedance calculator insert feed

my master graduation paper is to design a kind of multi-layer microstrip antenna . During the simulation I found that if the length of the feed line(whether microstrip or stripline) isn't long enough then the response of the system will include high-order modes.and these high-order modes will influse the result of S-parameter.

And I think the major advantage of the microstrip antenna is its minor size, so if you add a quarter wavelength impedance transformmer the advantage is discounted. why you not intend to design the input impedance of the antenna to match the port impedance?

If you design the uniform length of the feedline is long enouth then those high-order modes will can be neglected.

Just my suggestion.

V
Points: 2

#### goxy

##### Full Member level 4

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