The design of a horn like this begins with a specification. Usually the following parameters are given:

Gain (in dBi)

a (inches or cm) (usually the horn is fed from a waveguide)

b (inches or cm) (usually the horn is fed from a waveguide)

frequency (Hz)

The problem is to find A and B, and other dimensions shown below. Once we have these dimensions, we can find other parameters of the antenna.

The usual procedure is to solve an equation to get a *key parameter*
using the given specifications. This methodology will be outlined in this post
and access to the equation solver will be provided. Subsequent posts will add
more detail so that an engineer will be able to get a first cut design of the
horn and fabricate it.

After the required key value is obtained through solving the equation the following steps are used to find the Horn parameters.

Use

λ is the wavelength of the signal in cm. l_{e} is found from the
solution of the equation.

Calculate B from this equation.

From B, λ, l_{e} and G calculate A. The
equation to be used is:

G = (½)(4π/λ^{2})(AB)

Now we have A and B.

l_{h} is found from the following equation:

A = sqrt(3λl_{h})

Calculate R_{H} and R_{E }from the following equation:

R_{E }= (B -b)(sqrt[(l_{e}/B)^{2 }– ¼)])

Since we are dealing with a pyramidal horn R_{E }=R_{H}

Use the following equation for R1:

l_{h}^{2 }= R1^{2 }+ (A/2)^{2}

Use the following equation to calculate R2:

l_{e}^{2 }=
R2^{2 }+ (B/2)^{2}

The equation to be solved is: |

The quantity σ has to be solved for. σ =le/λ . This equation is best solved numerically with a starting value of σ = G/2π√6. The Python program that was written to do this is available on request at spg@signalpro.biz or spg327@gmail.com Ref: This blog is partially based on “Antenna Theory and Design, by Warren L. Stutzman and Gary A. Thiele. The book was published by John Wiley and Sons, 1981. Ref: The Python program was written by Anuj Tripathi, University of Arizona, Tucson, Arizona. |

A reverse calculator is provided now by SPG that calculates the number of turns needed to generate a given value of an inductor wound on a toroid. Please visit the SPG website and check under the “complementary” menu.

]]>The resistance of a resistive layer on an ASIC/IC is usually given (for hand calculations ) by taking the ratio of the length of the layer and its width and multiplying by its sheet resistance, (L/W)RS. Where L is the length, W is the width and RS is the sheet resistance. (Not every resistor can be calculated this way. Odd shapes are not amenable to this formula.) A simple javascript was generated at SPG that can be modified as needed to do this. Please visit the Signal Processing Group website to download the calculator free of cost. The calculator may be found under the “calculators” menu item.

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