#83: Basics of RF Mixers in Radio Receivers / Mixer Tutorial / Frequency Conversion
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange users link it when asking why a mixer's output contains many intermodulation and harmonic products beyond just the sum and difference frequencies.
Recommended by 1 people across 1 different months, 2019 to 2022.
What it is
A 16-minute tutorial by w2aew (Alan Wolke) on RF mixers used for frequency conversion in radio receivers. It shows input and output signals on an oscilloscope and the output spectrum, to illustrate the sum, difference and higher-order mixing products, and demonstrates IF filtering. It does not cover mixer design, mixer types, or how to choose one.
What people said
Recommends CEEA · 2022-02 · Electrical Engineering Stack Exchange · on “Downconversion Intermodulation Frequencies - Where do they come from?”
I recently came across this [this video] video which discusses the downconversion of a signal (referred to as IN) to an Intermediate Frequency (IF) using a Local Oscillator (LO). I'm assuming that all of these signals consist of a simple sinusoid with no other harmonics. I've been reading a textbook on how receivers in communications systems work and from the discussion in the book, I thought that multiplying the IN signal by the LO would result in two spikes in the frequency domain of the output signal (looking only at the positive half of the domain). One at \$f_{IN}+f_{LO}\$ and one at \$f_{IN}-f_{LO}\$ . However, in the video, he mentions that there are several "orders" of intermodulation pro
Cites Denis · 2019-10 · Electrical Engineering Stack Exchange · on “Can I input a square wave LO into a mixer?”
A typical RF mixer does not multiply the RF signal with the LO (local oscillator) signal. Instead, the signal polarity of the output depends on whether the LO is negative or positive: when the LO is positive the output signal is the same as the input signal (up to some gain) and when the LO is negative, the output is the same as the input but with an opposite sign. Now, effectively, this is the same as multiplying the input signal with the LO signal, but this is the case only when the LO is a square wave. This is why the LO in RF mixers is a square signal, because the mixer is designed to work with such a signal. The basic RF mixer consists of two swiches that pull the signal polarity one wa
Cites Denis · 2019-10 · Electrical Engineering Stack Exchange · on “Can I input a square wave LO into a mixer?”
Whether we filter the square wave or else, we still get all of these byproducts. [this video] Would there be anyone who could comment on this? Thanks.
Cites Denis · 2019-10 · Electrical Engineering Stack Exchange · on “Can I input a square wave LO into a mixer?”
Am I right to say that whether we filter the square wave or else, we still get all of these byproducts. According to W2AEW, [this video] even for a sine LO, products have lots of harmonics. Would there be anyone who could comment on this? Thanks.
Cites Majodi Ploegmakers · 2021-10 · Electrical Engineering Stack Exchange · on “Impedance transformer, how to measure”
I am preparing to do some RF mixer experiments with the SA612 Gilbert cell mixer. I started out with the impedance matching as I understand that the input and output need to be matched. From what I read, the impedance should match 1500 ohm single or 3000 ohm in a balanced configuration. So I need to match 50 to 3000 when using a balanced configuration. I decided to try winding a toroid. I used a T 80-2 (red, which should be good below 30MHz) with 23:3 turns: [LINK] But before I move on, I would like to measure it. I don't have any experience with this, so I would like to get a feeling if and how well it performs. But how? I have some basic equipment (scope, signal gen, nanoVNA, etc,) but I d
Cites Majodi Ploegmakers · 2021-10 · Electrical Engineering Stack Exchange · on “Impedance transformer, how to measure”
@glen_geek I was inspired by this [LINK] from w2aew. His toroids "look" the same, I mean, he didn't use enameled wire. So I thought I would come close to his results like this.