Is Time-Modulated Reflector Array with feed a challenge?

First of All, TMRA WITH FEED is really challenge. 

1. Which feed should be use?

  In the conventional TMRA with plane wave. The source is a plane wave which is considered as radiation from infinite far-field. The electromagnetic waves arrive at the elements at the same time. Hence, a exact identical theory from Time Modulated Array can be applied to TMRA. Hence, to make things easier, it is best to use a feeding source similar to plane wave. 

Furthermore, the back radiation of the source should be very small.

  1) dipole

        dipole is easy to make and simulate. The numerical theory is considerably easy. However, the radiation pattern is omni-directional at the H-plane (normally horizontal cut). That means the back radiation or the radiation towards the bore-sight is high (we expect only scattering from TMRA elements at bore sight). NOT GOOD CHOICE

  2) Patch antenna

       Patch antenna is seldom known in the use of reflector antenna. Performance is not tested. However, according to my experience of patch antenna. The antenna gain is small. The profile of the antenna is big. Back radiation is small. 

  3) Horn antenna

       Horn antenna is widely used to feed reflector arrays. The beam-width is fixable. The gain is flexible. Gain can be up to 20 dB. Low back radiation, 

2. How many elements should use?

  The number of elements is one of the parameter could be used in time-modulation theory. I would say the number of elements has the same functionality in conventional phased array. 

FOR a linear array, I would think one row of element is not enough. The scattering energy is comparably small thus the power from the feeding source domains. Hence, it is good to increasing the rows of element. 

A 2D array is good, elements are serial connected in column.   

3. How to deal with coupling?

Theoretical analysis do not consider coupling at all. Simulation in CST do. Couplings can be divided into

1) between ON element and OFF element

2) between ON element and ON element

3) between elements and feeding antenna 

4. Which is the best way to estimate the phase shifts of signals arrive at the elements?

original phase start at the antenna+phase shifts due to propagation.

Fig. 1 Illustration of a TMRA with feed: feed is placed at distance of d at the bore-sight of  TMRA; Ri is a relative path between the feed to the i-th element.

Fig 2. CST model of the feed (blue box: constructed in another file and imported as a field source) and the linear TMRA (8 element dipoles tested in previous research) 

Fig. 3 The feed: a X-band Horn designed use Antenna Magus (high gain and wide beam-width)

Solo walk at Derwent dams Peak District

On a nice sunny Sunday, I went to Derwent dams for a 3 hours walk. The view is picturistic. Woods, water, breeze, sunshine and lovely people make the Sunday the day. 

a view of Howden Dam (Upper Derwent) 

 The leaves are going red soon

 Light and shadow (a drive way in the woods)

It says 'take time to look, to sit, to stare, allow these hills to ease your cares' on a bench. 

Lockerbrook is a field of woods with amazing view of whole reservoir

Enjoy!