Are HD antenna different from analog antenna?

Not really.

While some "HD" antennas are designed to minimize the effects of multipath reflections in large cities, there's no fundamental difference between an "HD antenna" and an "analog antenna". In a larger city where the TV transmitters are nearby and you have a good line-of-sight to them, you'll see no difference. The antenna is only used to pick up the air signal, which is on the same frequency band as old Analog TV. The only difference is the old-style analog NTSC (or PAL or SECAM) TV standard(s) used an analog carrier and the DTV ATSC standard uses a digital carrier.

The whole "HD" + "Analog" antenna thing is basically hype.