Receiver

The receiver is the device that decodes the transmitted data from the received signal. The receiver, like the transmitter, requires an antenna to receive the signal from the air. Many receivers include additional filtering and tuning circuits to focus on the desired frequency more effectively or deliver the higher-quality audio output and filter out undesirable sounds.

Receivers are unquestionably crucial in every communication system. They are in charge of receiving incoming sent signals and recovering the information within them. Given the vast volume of data transmitted wirelessly today, it is essential to understand this topic thoroughly and understand the concept. 

Types of Receiver

Direct-Conversion Receiver

One sort of receiver architecture is the direct-conversion receiver, often known as a homodyne or zero-IF receiver. Direct-conversion receivers transform an RF signal to a 0-Hz signal in one step. They’re typically considered low-cost solutions because they only require a few components. Furthermore, they are well-suited to integrated-circuit (IC) designs.

A received RF input signal is often filtered and amplified by direct-conversion receivers. The signal is then combined with a local-oscillator (LO) signal of the same frequency as the RF input signal in a mixer. As a result, the input signal is converted to a 0-Hz signal, which appears at the mixer’s output. Demodulation can also happen at the time of frequency conversion. Although the total of the RF and LO signal frequencies shows at the mixer’s output, this product is removed by the mixer’s low-pass filtering. Of course, the demodulated baseband output is then processed.

Superheterodyne Receiver

A well-known receiver design that has been around for quite some time is the superheterodyne receiver. The lower-frequency intermediate-frequency (IF) signal is converted from a higher-frequency radio frequency (RF) signal. After the IF signal has been demodulated, the modulation data is handled.

Analysing the fundamental types of receivers can explain the entire process. A bandpass filter is used to filter a received signal initially. This filter, also known as a pre-select filter, rejects out-of-band signals. Following that, a low-noise amplifier (LNA) boosts the signal’s amplitude. Because the overall noise figure of a superheterodyne receiver is heavily dependent on the noise figure of the LNA, this LNA is a critical component. The LNA is followed by an image-reject filter, a bandpass filter. This filter’s goal is to eliminate the undesired picture frequency band.

Functions of Receiver

A receiving antenna provides the signal that goes into the receiver. Modulated RF carrier signals can characterise the received signals, usually quite faint. The actual data, audio, video or data, is carried via the modulation. To decode and analyse modulation information, a receiver must undertake a series of actions on a received signal.

Receivers must be able to work well even when there is noise and other interfering signals. As a result, selectivity and sensitivity are vital qualities to have. A receiver’s ability to identify and pick the desired signal in the presence of multiple undesired signals is referred to as selectivity. A good selectivity receiver will process desirable signals while rejecting unwanted spurious and interference signals.

Sensitivity refers to a receiver’s ability to process very faint input signals. It can be measured as the weakest signal level that a receiver can detect to achieve a specific criterion, such as a specified bit-error-rate (BER) or signal-to-noise-and-distortion (SINAD) ratio.

Each application has its unique set of requirements, necessitating the use of a variety of radio receivers. Some radio receivers are significantly more straightforward than others, while others offer better performance levels and are less space-constrained.

The advantages of Superheterodyne Receiver

High RF amplification – the Superheterodyne concept creates an intermediate frequency (i.e., 455 kHz) that is significantly lower than the radiofrequency. Because feedback through stray and interelectrode capacitance is decreased, RF amplification at low frequencies is more steady.

Improved selectivity — at immediate frequency, losses in tuned circuits are smaller. As a result, the tuned circuits’ quality factor Q rises. As a result, the amplifier circuits can operate with the highest level of selectivity.

Lower cost – with Superheterodyne, regardless of the radio wave used, a fixed intermediate frequency is obtained. This allows RF amplifiers to be used. As a result, the Superheterodyne receiver is less expensive than other radio receivers.

Conclusion

The term “receiver” refers to electronic equipment that receives radio waves and translates the data they carry into a form that can be used. The desired frequency waves are caught using an antenna. In the receiver, electronic filters isolate the intended signal from all other signals picked up by the antenna, an electronic amplifier boosts the signal’s power for further processing and demodulation retrieves the relevant data.

In comparison to modern radio receivers, early radio receivers had low performance. Very high-performance radios are already prevalent thanks to modern technology such as digital signal processing, high-performance transistors and other components.