We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Is a Frequency Mixer?

By Geisha A. Legazpi
Updated Feb 21, 2024
Our promise to you
WiseGeek is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At WiseGeek, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A frequency mixer is a nonlinear or multiplier electrical circuit that is able to produce continuous sum and difference frequencies of two or more input signals. The device is widely used in telecommunications transmitters and receivers. The mathematical products of sinusoidal signals have additive and subtractive effects on the resulting frequencies. In the common superheterodyne receiver, for instance, the frequency mixer inputs are the radio frequency (RF) signal that is incoming and the local oscillator (LO) signal and the resulting sum or difference of the two inputs is the intermediate frequency (IF). Besides the sum and difference frequencies, there are other outputs in smaller amplitudes including higher-frequency or higher-order harmonics.

Using the IF amplifier stages simplifies the first RF amplifier stages of the receiver. Usually, only one front-end stage needs to be tunable across the receiver band. The rest of the RF amplifiers after the frequency mixer are tuned only to the IF. A special mixer called a subharmonic mixer may input an LO frequency that is half the required frequency, pass through a nonlinear device, and effectively generate an LO at twice the original frequency.

When vacuum tubes or triodes were used, a grid between the cathode and the anode was able to control the flow of electrons. By proper design, the triode was able to amplify RF signals and to oscillate given the right passive-tuned tank circuits as frequency reference. The triode was developed to have more than one control grid. In early 1900s, the pentagrid converter was used as a frequency mixer where a triode with four additional grids performed the amplifier, oscillator, and mixer functions, resulting in single-vacuum front-end for receivers.

Ring modulation allows the use of transformers and a bridge diode configuration to produce the desired multiplication of the message and the carrier frequency. The result is a frequency spectrum with the message shifted higher in frequency by an amount equal to the carrier frequency. On the receiver side, the product detector may be used to input the modulated carrier and the carrier reference frequency to recover the original message.

A Gilbert cell is a bipolar transistor circuit that makes use of the current gain of direct-coupled bipolar transistor stages to generate the required analog multiplication to produce frequency mixer outputs. The first input signal is fed to the base terminals of two transistors working as a differential pair, while the second input is fed to the base terminals of two differential pairs of transistors with emitters that provide the collector currents for the differential pair for the first input signal. The resulting output is available at the collectors of the differential pairs for the second input signal.

The frequency mixer may also work as a frequency multiplier. If the same signal is fed to the input of a frequency mixer, the output frequencies include integer multiples of the input frequency. The second and third harmonics will be available at the output with the second harmonic having a higher level than the third harmonic.

WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.