TX Mixer
TX Mixer Consider a typical TX with DAC (digital to analog converter), BBF (baseband filter and/or amplifier) and MIX (mixer) as shown in image below. Say DAC outputs a sinusoid signal. Let’s do some math to see what happens to the signal when it makes it to the TX output. $$ DAC,(t): Vcos(omega_{bb},t)$$ This signal […]
Semiconductor Yield Estimation
Semiconductor Yield Estimation Say you have an amplifier with Gain spec of x dB and you want to understand how many chips will pass this spec. What do you do? You measure all the parts you have, count the parts where gain fell below x dB and divide it to total number of parts, and […]
Single Tone Distortion
Distortion of a Single Tone in a non-linear System How does a single tone gets distorted in a non-linear system, what distortion products it generates and some insights into what goes in signal gain. Assume a non-linear system which can be modelled using a polynomial: $$V_o = a_o+a_1V_i+a_2V_i^2+a_3V_i^3+a_4V_i^4+a_5V_i^5$$ Let’s excite it with a single tone: […]
Counter Intermodulation Distortion aka 4FMODs
4FMODs and Counter IM3 New to transmitter design? Trying to understand what metrics are used by industry for transmitter design? You might have heard of primary 4FMOD (also called CIM3) and secondary 4FMOD (also called CIM5). Unlike traditional IM3 which is generated by intermodulation of two tones, CIM3 and CIM5 are primarily generated by distortion […]
Intermodulation of Two Tones
Intermodulation of Two Tones Admit it. You are lazy and don’t make notes. You do this math every time you need to remember what distortion products are generated by intermodulation of two tones and what is their relative level. No more. We are doing the math now, so you don’t have to. Intermodulation Math Assume […]
Transmitter Specs
Transmitter Specs Having little exposure to Industry, academic researchers wonder if they are designing the transmitter for the right metrics? Are transmitter specs all about output power and linearity? And besides what metrics are used by industry to characterize linearity? If you have such questions, you have landed at correct place. Take a look at […]