12 Dec Starting to build a Radio Receiver
The objective of this article is to explain the DRM Receiver Technology beyond the basic blocks articulated in the October Newsletter. The first section in the signal chain was the RF block. In the last few decades it has become obvious that the RF generators are not the only transmitters functioning at the radio broadcasting sites. Instead every single item of electronics equipment can become potential RF generators, some intentionally like mobile phones, Bluetooth devices, Wi-Fi equipment, etc. The high RF density today also manifests itself as RF noise and is highest in lower frequencies; it decays exponentially with increase in frequency. It is for this reason the traditional AM radios don’t sound as good as they used to even though the receiver sensitivities and technology have improved significantly. Thus shielding the susceptible parts and the filtering of noise is essential for the optimum functioning of these radios.
Channel and source coding, which form part of the DRM transmission and reception, make the product error resilient and also offer a significant amount of error correction. Newer and upcoming source decoders in the DRM Technology enhance this functionality further. Since these encoders and decoders have been researched and ported on to processors by chip vendors, this does not remain a hurdle anymore. The decoded audio data is sent to amplifier and speakers’ block. The quality of audio is important and should not be compromised. But it is common knowledge that this may also increase the cost of the materials required for the product. So there has to be a judicious selection of components and appropriate trade off.
RF front-end devices which down convert the signal of interest to digitized IF or low-IF signal are also easily available. Manufacturers of these ICs also provide a reference designs that has been well researched and designed for best noise immunity and least susceptibility. Thus eliminating the risk of doing multiple iterations on the PCB designs and removing one more hurdle.
The last element in the block is the man machine interface, which is very specific and custom built for the manufacturer so as to bring in the product differentiation. There are independent design houses to do this modification also.
Bottom line, all required material is available like a pre-cooked meal and aesthetically appealing plastic encasement needs to be created by the manufacturer and the reference PCBs that are already available may be redesigned or re-CAD and the product can be manufactured very quickly and easily.
Thus crossing the bridge or getting over the technology barrier does not have the uncertainties of success anymore and can easily be accomplished by the radio receiver manufacturer.
TVB Subrahmanyam of Analog Devices