Ohased Array For Small Craft Radar

As I understand it:

With no phase steering, the signals from all the dipoles would be superimposed on each other to get one main signal from a point perpendicular to the array. By timing the superposition so that the signals from one side (let's say the left side column) are matched with signals from the next column a tiny fraction of a second later, then a fraction of a second later for the 3rd column, etc. until the signals from all the columns have been superimposed, the arrays is phased-tuned to see signals coming from the left side.

Like wise for up-down steering; so depending on how you phase-combine each element you can effectively steer the angle over a range of angles up-down and left-right.

Not sure why the power is lower, other than the miniaturization process and improvement in signal/noise ratio.

Some of the earliest radars were phased-array, as seen by the four vertical dipole antennas. By staggering the signal, the effect is like the rotating field in a motor; it "sweeps" like a lighthouse beam.

Here is an excellent website on the subject; MUST SEE.

Radar Basics - Phased Array Antenna

Figure 2: Animation of the electronic beam-deflection

In the figure 1 (right), the signal is emitted by the lower radiating element with a phase shift of 10 degrees earlier than of the upper radiating element. Because of this the main direction of the emitted sum-signal is moved upwards.

(Note: Radiating elements have been used without reflector in the figure. Therefore the

Thanks Lyn, nice website. unfortunately it doesn't help explain the power aspect.

with the old system a 4kW radar; with a magnetron and a wave guide you had to have a 10 amp and some 15 amp main fuse. Today a 4kW radar spec a 33.5 W average power drain at 10.5 volts minimum. The inline fuse is 3A on the main power cable. Thes small craft radar are still X band and still have approximately the same pulse repetition rate and range so what has been changed to cut power? The old sets wer transistorized as well. Is a caznge in type of seminconductor really able to cut power consumption that much while retaining radiated power at the same level?

That's over my head, except to say that everything produced now uses less power to get more performance.

Components that used to require a minimum of 6-9v now operate at 3v, or less. Power devices have come a long way, too. But I'm not an electrical type.

I don't have a lot of experience with X-band stuff, but I know that semiconductor RF devices have been improving as time goes on. You mentioned "Magnetron" in your follow-up post. I know in the past, in order to get high-power X-band signals, a magnetron was one of the few ways you could get Kw of power. Now, there are semiconductor solutions that can achieve the same thing. Perhaps that's where the efficiency improvement lies, semiconductor sources vs Magnetron?

Tom D.

That could be part of the explanation. I am thinking the term phased array has been a misleading description. Unlike true phased arrays which are steerable like the system by Raytheorn on the Aegis cruisers the small boat radar has a bunch of dipoles etched on a circuit board. The board itself is mounted on a frame which is mechanically rotated. This is certainly a lower cost solution that the steerable phased array used for weather radar on aircraft.

I'm also guessing there may be a bit of calculation fudge involved. If each dipole emits so much by multiplying by the number of dipoles you can get a respectable number that looks good for marketing.

Trying to get any real information from the people manning a booth at a trade show is not likely to works because the actual designers are not the people hired to man the sales booth. If the product is provided by a third party sub contractor its impossible to find the real designer.

It may be that the new design has much better antenna gain and less losses in the system design, which provide better "effective radiated power", which is probably what they are quoting as output power. Just a thought.