History of Microwave Circuits (I)

1 Introduction

In the 1960s, especially in the 1970s, due to the rapid development of microwave semiconductor circuits, microwaves played an increasingly important role in the field of radio technology. At present, it has been widely used in microwave relay communication, satellite communication, radar, guidance, electronic measuring instruments and electronic equipment of various aircraft. Therefore, theoretical and engineering personnel engaged in radio and electronic technology are in scientific research and production practice. A large number of microwave electronic circuits will be contacted and used.

2 microwave circuit generation

"Microwave circuits" have long been synonymous with "waveguide circuits". As early as the early 1930s, it was recognized that waveguides are a useful transmission structure for microwave frequencies. Of course, these should be mentioned. The work of Southworth et al. at Bell Labs. Researchers have long discovered that a properly modified small section of the waveguide can be used as a radiator or an electrical antigen. Southworth talked about resonant cavities and horn antennas in an early paper. In the development of modern waveguide circuits, the microwave power was efficiently transmitted from the microwave source to the waveguide transmission line from the beginning, and can be effectively recovered at the receiving end, which puts forward the corresponding original transmitter and receiver. High requirements. Therefore, it has led to the emergence of components such as traveling wave detectors, wavelength meters, and terminal loads. However, the level of microwave technology used in the year was very backward. At that time, microwave experiments were often carried out using optical test benches. The International Radio Engineering (IRE) Journal published a review of the history of microwave technology development in its 50th Anniversary Collection. The article, there are several photos of the equipment used in the year.

The development and application of microwave technology constitute the basis of microwave circuits. From the originally discovered principle of multiple reflections of discontinuities and the corresponding cavity resonance principle, to the use of these principles to match the microwave power source to the waveguide, and then to match the waveguide to the receiver (such as a crystal detector), And using these devices, a signal of a certain frequency is passed through the circuit.

One of the basic features of microwave circuits is the ability to adjust or tune their characteristics through the screws, diaphragms (and thus the size of the compression) inside the waveguide. At first, this was only a trial and error method, and later developed into the so-called "waveguide engineering." It is also one of the most common methods of microwave engineering for a long time.

3 Status of microwave circuits

Microwave circuits began in the stereoscopic microwave circuit used in the 1940s, which consisted of a waveguide transmission line, a waveguide element, a resonant cavity, and a microwave tube. In the 1960s, a new generation of microwave integrated circuits, which were known for their semiconductor devices, thin film deposition technology, and lithography, emerged. Due to its small size, light weight and easy to use, it is fully utilized in weapons, aerospace and satellite.

During the Second World War, two basic transmissions, the waveguide and the TEM mode coaxial line, were often used in microwave circuits. The waveguide is characterized by high power and low loss. The latter feature leads to the appearance of a high Q resonator. The same axis has inherent broadband characteristics due to the absence of dispersion effects. In addition, the concept of impedance can be easily explained in the coaxial line, which simplifies the design process of the component. These two transmission structures have evolved into important microwave circuit components, and the two can be used together to achieve unexpected effects.

In 1951, Barrett and Barnes proposed a structure in which a stripline transmission structure was used in a microwave circuit in the same manner as used today, consisting of two thin strip-shaped conductors sandwiched between metal sheets on the outside. Its plan view is shown in Figure 3-1. In the early ribbon process, a squeegee and glue were used to cut and bond the ribbon conductor to the dielectric plate. With the advent of copper-clad laminates, stripline development has become a sophisticated process with pre-calculated performance. The most important feature of the stripline transmission structure is that its characteristic impedance is controlled by the width of the center strip conductor. The two-position nature of the stripline circuit structure allows it to interconnect many components without damaging the shield of the outer conductor, which also provides great flexibility in the input and output locations. Since the two strip conductors are in close proximity, there is inherent coupling characteristics, so the strip line is very convenient to use in parallel line couplers.

Since 1974, Plessey Corporation of the United States has used GaAs FETs as active devices and GaAs semi-insulating substrates as carriers to develop the world's first MMIC amplifiers in military applications (including smart weapons, radar, communications, and electronic warfare, etc.). Under the impetus, the development of MMIC is very rapid. It is the advent of GaAs technology and the characteristics of GaAs materials that have contributed to the transition from microwave integrated circuits to monolithic microwave integrated circuits (MMICs). Compared with the second-generation microwave hybrid circuit HMIC, the MMIC has received much attention because of its smaller size, longer life, higher reliability, lower noise, lower power consumption, and higher operating limit frequency.

The emergence of monolithic microwave integrated circuits has made possible the realization of various microwave circuits. As a result, various MMIC devices have reached unprecedented levels, such as MMIC amplifiers, low noise amplifiers (LNAs), mixers, upconverters, voltage controlled oscillators (VCOs), filters, etc. up to the MMIC front end and the entire transceiver system. . Monolithic microwave integrated circuits have broad application prospects in solid-state phased array radar, electronic countermeasure equipment, tactical missiles, television satellite receiving, microwave communications and ultra-high-speed computers, and large-capacity information processing.

With the further improvement of MMIC technology and the advancement of multi-layer integrated circuit technology, three-dimensional multilayer microwave structures using almost all passive devices and chip interconnection networks in multilayer substrates have received more and more attention. Moreover, the MCM (Multi-Chip Module) technology built on a multilayer interconnect substrate will make the size of the microwave millimeter wave system smaller.