Antennas are bringing in more inputs, letting users pull in more information for navigation, GPS, phones, radio, and even television. There’s also a push to put smaller antennas further from noisy engine compartments, making it more challenging to transmit signals to the radio head unit.
Atmel Corp. has responded with a chip that gives designers more capability to put antennas in space-limited areas far from the radio. Its ATR4253 active antenna integrated circuit (IC) is designed for FM car antennas, car radios, and navigation applications. The chip, designed in Germany, also works with antennas used for Digital Media Broadcasting (DMB) in Korea, Digital Video Broadcasting-Terrestrial (DVB-T) in Europe and the U.S., and Integrated Services Digital Broadcasting-T (ISDB-T) in Japan.
Though antennas are often overlooked, their role is expanding as drivers demand more inputs. Antennas that must bring in more inputs are often smaller, fitting in shark-fin formats or in side mirrors. That is forcing engineers to move to a single chip instead of discrete components.
“Amplifiers have been made with discretes, which was okay with a big antennas,” said Carsten Friedrich, Atmel’s Manager of Car Radio ICs. “Now antennas are being placed in windows or even side mirrors, so you want smaller packages.”
The 3 x 3 mm (0.12 x 0.12 in) size of the ATR4253 is small enough to sit close to these remote antennas. This proximity lets it match the impedance of the cable and antenna and amplify the signal. The amplification capability makes the device useful as a pre-amplifier for car radios or navigation applications which require FM Radio Data System information.
The IC also addresses the growing focus on electromagnetic coupling, which is becoming more critical with the increasing use of high-speed electronics. EMC often forces designers to move antennas to the back of the vehicle.
“There’s more electromagnetic disturbance now, especially around the engine, so you want to put the antenna as far from engine as possible," said Friedrich. "But if you put it in the rear of the car, it’s a long way from the radio. That means more cable loss, so amplification is very important.”
The device also has some diagnostic features that can be particularly helpful for antennas placed in locations such as hatchback windows or on a trunk lid where the connectors can be disconnected. The chip can tell drivers and technicians that the pigtail connector is disconnected, eliminating or shortening a service call. Electrostatic discharge protection up to two kV also reduces the chance of damage.