IQ Mixer: Working, Features, and Top Manufacturers

IQ mixers are pivotal in modern RF and communication systems, enabling functions like phase modulation, demodulation and image rejection. This guide explains their working principles, highlights essential features, and lists leading manufacturers offering state-of-the-art IQ mixers for various applications. IQ mixer is usually made up of GaAs HBT shottky diode. It is widely used in point to point radios, satecom, sensors and test & measurement applications. It is used as image reject mixer, single sideband frequency converter, IQ demodulator, IQ modulator etc.

IQ mixer operation or working

An IQ mixer, or quadrature mixer, is a type of frequency mixer that processes signals into two separate components: in-phase (I) and quadrature-phase (Q). These components enable complex signal modulation and demodulation, such as amplitude modulation (AM), frequency modulation (FM), phase modulation (PM), and quadrature amplitude modulation (QAM). Here's how it works.

Basic Components of an IQ Mixer are as follows.
1. Local Oscillator (LO): Provides a reference signal split into two components that are 90° out of phase.
2. RF Input Signal: The signal to be mixed or processed.
3. I and Q Outputs: The result of mixing the RF input with the LO signal's in-phase and quadrature-phase components.
4. Mixing Diodes or Transistors: Perform the actual frequency conversion.

IQ mixer

Signal Splitting

The LO signal is divided into two paths:
• In-phase (I): Retains the original phase of the LO signal.
• Quadrature-phase (Q): The LO signal shifted by 90 degree.

Mixing Process

• The RF signal is mixed with the I and Q components of the LO signal in separate mixers.
• These mixers produce outputs at the sum and difference frequencies of the RF and LO signals.

Filtering and Isolation

Filters are applied to separate the desired output frequencies (e.g., sum or difference) from unwanted products. The I and Q components are then isolated as distinct baseband signals.

Combining or Processing I and Q Signals

• Demodulation: In receivers, the I and Q components are combined to reconstruct the original complex signal.
• Modulation: In transmitters, input I and Q signals are mixed with the LO to generate modulated RF signals.

Mathematical representation

Assume an RF input signal as SRF = A * cos (WRF *t + φ)
LO signal say : SLO = cos(WLO*t) and sin (WLO*t)
The mixer outputs two baseband components.
• In-Phase (I) = A*cos(φ)
• Quadrature-phase (Q) = A*sin(φ)
➨The combination of I and Q allows complete representation of the original RF signal's amplitude and phase.

IQ mixer Specifications

Following specifications need to be consider while purchasing the IQ mixer:
• Frequency of operation at RF, LO and IF1/IF2 ports
• Image rejection (in dB)
• LO to RF isolation
• LO to IF isolation
• RF to IF isolation
• Conversion gain
• IIP3(dBm)

IQ Mixer Manufacturers

Several manufacturers specialize in producing high quality IQ mixers for various RF needs. Here are some notable companies.

Manufacturer Location Speciality Key products/Features
Marki Microwave Morgan Hill, CA, USA High performance IQ mixers, both connectorized and bare die Covers wide frequency ranges; suitable for image rejection and single sideband modulation
Mini-Circuits Brooklyn, NY, USA Versatile IQ mixers for RF and microwave applications Models like SMIQ-653H-DG+; RF/LO frequencies up to 65 GHz
Pasternack Enterprises Irvine, CA, USA Reliable IQ mixers for various applications RF and LO frequency bands from 4 GHz to 38 GHz; focus on satellite communications and point to point systems
Qorvo Greensboro, NC, USA Broad range of RF products, including IQ mixers Offers standalone mixers and integrated solutions for up and down conversion
Analog Devices (ADI) Norwood, MA, USA High precision RF and microwave solutions Wideband IQ mixers with low noise and high linearity
Qualwave China Cost effective solutions for RF and microwave needs High isolation broadband IQ mixers designed for signal processing
Skyworks Solutions Irvine, CA, USA Integrated RF solutions, including IQ mixers High performance IQ mixers for communication systems
Hittite Microwave (ADI) Chelmsford, MA, USA Specialized in RF, microwave, and millimeter wave components Versatile IQ mixers with low conversion loss and high isolation

Applications of IQ Mixers

• Image Rejection: Removes image frequencies in receivers.
• Modulation and Demodulation: Used in QAM, QPSK, and other digital communication schemes.
• Frequency Conversion: Supports up conversion (transmitters) and down conversion (receivers).
• Phase Measurement: Enables accurate phase and amplitude measurements.

COnclusion

IQ mixers are indispensable for advanced communication systems, offering precision and versatility. With a clear understanding of their working and features, and knowledge of reliable manufacturers, you can select the best solutions to meet your RF design needs.

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