Monolithic Microwave Integrated Circuit

Monolithic microwave integrated circuit (MMIC) technology offers a reliable and cost-effective solution to meet the requirements of today’s advanced military and commercial RF systems. Its advantages include radiation hardness, high reliability, compact size and low weight.

MMIC power amplifiers are typically fabricated on GaAs substrates, but other III-V compound semiconductor materials like indium phosphide (InP) and silicon germanium (SiGe) have also been used.

Integrated Circuits

A monolithic microwave integrated circuit combines all the active and passive elements required for operation at a specific frequency on a single semiconductor chip. The combination reduces weight, volume, and power consumption compared to discrete components. It also enables a larger number of functions to be integrated into smaller packages. In addition, a monolithic IC is more reliable than a hybrid IC.

The design process for an IC is iterative and involves three phases: architectural, physical, and layout. In the architecture phase, the IC requirements are defined. This includes determining what functions the IC must perform and what performance targets are to be achieved. This information is used to select the best technology for implementing the IC.

During the physical design, the monolithic microwave integrated circuit actual shape of the circuit elements is determined. This is a complex task that requires sophisticated computer software to manage. It includes the use of a 3D computer-aided design tool, large signal modeling of InP heterojunction bipolar transistors (HBTs), and RF circuit simulation.

In the layout phase, the circuit elements are placed on the substrate. The final layout must account for the interaction between different components, which is influenced by their electrical properties and the mechanical properties of the substrate material. For example, the substrate must be able to withstand both concave and convex bending while maintaining a low DC resistance and good RF characteristics.

Discrete Components

Discrete components are single-element electronic devices that either regulate voltage and current flows or impact signals actively. They are classified as passive (primarily to regulate and do not achieve power gain) and active (switching devices).

Passive components include resistors, inductors, diodes and transmission lines. They are the building blocks of any electronic circuit, and their performance is dictated by their construction and materials.

In the case of a phase shifter, for example, one of the most common discrete components is the PIN diode. These are a class of semiconductor diodes that look like classic transistors, but differ by having layers of P and N semiconductors with a poorly doped intrinsic semiconductive region in between. This makes them able to process high-frequency signals.

Another common passive component is the microwave resonator, which is a cylinder-shaped element with a series of holes or slots that resonate at a specific frequency. This component is used to convert microwave signals to electric energy.

Discrete components are available in a range of casings, from classic TO92 to surface-mount SMD designs. They can also be found in metallized multilayer ceramic packages that minimize ring resonance from stray electromagnetic waves. This is especially important in monolithic microwave integrated circuit manufacturer systems that rely on the linear operation of power amplifiers, which require the highest power dissipation and therefore demand superior thermal management.

MMICs

MMICs incorporate all the elements of a microwave circuit on a single semiconductor substrate. This allows them to be fabricated more cheaply than hybrid or discrete components, while providing improved reliability and performance. MMICs can be used in a variety of applications including power amplifiers, wireless modules, and space avionics.

The design of MMICs begins with the development of an active and passive device model. This can be done using both CAD and FEA tools. The resulting model is used to simulate the operation of the MMIC, and to predict the performance of the device in its intended application.

Once the MMIC is designed, it is fabricated using foundry processes. A MMIC can have many different devices on a single die, and each device may be realized in different ways. This can affect the output power, gain, and other parameters of the device. For this reason, it is important to understand the process variations that occur during fabrication.

MMICs require suitable packaging to be integrated in their destination systems. The package should provide a mechanical shield to the device, allow for easy RF and DC access, and guarantee adequate thermal management. For commercial applications, plastic low-cost packages are common, while for high-performance applications such as military and spacecraft a custom ceramic package is often utilized.

Hybrid

A hybrid circuit incorporates individual semiconductor devices and passive components like resistors, diodes, inductors and transformers, resulting in a compact electronic device with lower cost. It is a popular choice for analog circuits, microwave power amplifiers and special circuits that require higher voltage and larger current.

The process of fabricating a thin-film hybrid IC involves the use of photolithography to construct a complex pattern on a ceramic substrate. The pattern consists of conductive and semiconductor film layers that are intricately combined to create electronic devices and interconnection lines. Once the entire circuit has been patterned, lead wires are meticulously attached to the device, and the hybrid IC is encapsulated in an outer casing.

Hybrid ICs offer the benefits of reduced weight and size, lower component count, high efficiency and improved reliability over their discrete counterparts. However, they do not perform as well at very high frequencies and may not be suitable for all applications.

Flexible hybrid electronics combine rigid and flexible substrates to create thin, lightweight modules with a wide range of processing and transmission capabilities. Using low dielectric-constant materials and very fine conductor lines, they minimize signal attenuation and increase speed, enabling advanced functions in a variety of new form factors.