Direct Conversion Receivers

Direct Conversion Receivers – All You Need to Know

Radio receivers are super important parts of a functioning radio. A radio receiver is what uses the information from the antenna and demodulates the signal turning it into something we can listen to. There are many different types of radio receivers and different types of designs. 

A direct conversion receiver is a type of receiver that demodulates an incoming signal using an oscillator whose frequency is similar to the carrier frequency of the incoming signal. Direct conversion receivers are also known as homodyne receivers. 

Unlike the superheterodyne receiver, the modulated signal is converted to an audio signal all in one step. This makes the process a bit easier than the superheterodyne process which takes multiple steps to transform the radio signal. The IF frequency of a direct conversion receiver is zero. 

In both homodyne and superheterodyne receivers, the modulated RF signal comes through the antenna and is fed through an oscillator. In the homodyne receiver, the oscillator is producing a signal that is identical to the carrier signal. In the superheterodyne receiver, the oscillator is producing a signal that is slightly off of the carrier signal which creates an intermediate frequency. 

Advantages and Disadvantages

There are many advantages and disadvantages of direct conversion receivers. The biggest advantage is the lack of multiple conversion stages. This design converts the signal in one pass. Because of this, the design results in less circuitry and power consumption. 

The disadvantage is that sometimes signal leakage can occur. The circuit has a hard time rejecting hums because of the high audio frequency gain that is required to make the circuit work. 

History and Usage

The homodyne, or direct conversion receiver, was invented in 1932 by the British in efforts to create something that worked better than the superheterodyne receiver. 

Today direct conversion receivers are widely used in cell phones, tv’s, medical equipment and software defined radio systems. 

Conclusion

To conclude, radio receivers are an incredibly important part of radio design. The receiver is what takes the information from the antenna and turns it into something we can understand and listen to. 

There are many different kinds of designs for radio receivers but two of the most popular are superheterodyne and homodyne (otherwise known as direct conversion receivers). These two types of receivers work similarly but not exactly the same. 

A superheterodyne receiver converts the modulated signal to a base signal in two steps. The homodyne receiver does the same thing except it only takes one step to be completed. The homodyne receiver has its oscillator set to the same frequency as the carrier frequency which is how it produces a demodulated signal in one step. 

Even though the homodyne receiver uses less circuitry and requires less power, it is still not as popular with radio. The superheterodyne receiver is what is mostly found in radio but the homodyne receiver is a great alternative to check out. 

Check out these related links: 

https://www.cwtouchkeyer.com/amplifier-design/

https://www.cwtouchkeyer.com/oscillator-design/

https://www.cwtouchkeyer.com/ham-radio-modulation/

https://www.cwtouchkeyer.com/ham-radio-electricity-basics/

Sources:

Wikipedia

Wikipedia

YouTube

ARRL