A "frequency sweep" is simply calculating the response of the antenna over a range of frequencies.  This would let you, for example, plot the input impedance as a function of frequency, or S11 as a function of frequency.  The broader label is "parameter sweep."  This may be the most powerful technique for designing devices and learning about them.  

Frequency sweep is nothing but range of  frequencies of your interest to observe your antenna characteristics in mentioned frequency sweep.

For driven solution type the frequency sweep is the range of frequencies for which solution is desired. For most antenna simulations the solution frequency is the operating frequency of antenna and for filter simulations it will be the center of the band pass frequency. You can find the published data (simulation parameters and frequency range) of different microwave devices over the internet . This will help you to understand how to choose solution frequency for your device.

Traditionally frequency sweep means to change the frequency in a predefined step between pre decided start and stop frequency band

In HFSS, the set sweep will calculate the characteristic of the parametewr with ref to frequency in a set band

To observe the reflection loss (S11) and to observe the gain of antenna in a given frequency range it is necessary to add frequency sweep. In frequency sweep you need to mention the start (say 5 GHz) and stop frequency (say 10 GHz) and also step frequency (say 0.1 GHz), hence you can observe your antenna S-parameter characteristics and also radiation performance mainly gain in that frequency range (5-10 GHz). 

 When you set a freq sweep in your simulation, in fact you choose frequencies for which the software calculates the intended parameters such as S parameters.

In frequency sweep you just set the range of frequency in which you want to calculate your antenna S-parameters and check the gain at your frequency of interest.

Frequency sweep means the range of your antenna parameter calculations, and you have to set your solution frequency slightly higher than your target frequency for microstrip patch antenna.

Thanks everybody the valuable answers.

freq sweep is used to compare the power of the signal received at each frequency from the frequency band and then choose the better one. 

Hi Mr. Chettri 

Like your application is GSM 900 so your center or solution frequency should be 900 MHz and according you can visualize the response offered by your antenna is particular frequency band which is referred to as freq sweep say 0-1.8 GHz.

Regards

Sameer

Hi Mr. Chettri,

The frequency sweep will allow you to check on the frequency band of operation of your antenna. It should be chosen according to your design frequency.

Regards

Kheireddine