There has been always a concern for every scaled CMOS generation, whether such low-cost,low-area RF CMOS devices can satisfy the RF requirements for the high performance RF applications. This report introduces the design, simulation and imple-mentation of test set in the integrated approach for network analyzer which can be used at frequencies which require large bandwidth.The testset of a network analyzer separates the incident, reflected and transmitted waves for an arbitrary device under test (DUT), to calculate the S-parameters of the DUT. The idea behind this is to design test set which will be compact with low cost, low area and which can be used for broad bandwidth. The initial points on the development of the circuit were dependent on the phenomenon that it will work at high frequency up to 10GHz. While designing the circuit one important thing has to be considered is, only CMOS technology used to design the test set since it consumes less power, high packing density, operation at high switching frequencies, high operational speed. In the design, 180 nm CMOS technology has been used for the simula-tion to avoid short channel e?ects. The setup consists mainly of a phase divider, voltage reference circuit, impedance matching network and combiner circuit. It is expected that test set will be able to separate the incident and reflected signals upto frequency atleast 10GHz.
Network analysis is one of the most important and powerful measurement techniques in the discipline of microwave engineering. It facilitates the analysis of various network types such as active circuitry, passive components, or sensors. Network analyz-ers are typically utilized for the measurement of S-parameters, which correlate incident, reflected, and transmitted wave portions in both magnitude and phase.
A network analyzer is an instrument that measures the network parameters of electrical networks. Network analyzers commonly measure s–parameters because reflection and transmission of electrical networks are easy to measure at high frequencies, but there are other network parameter sets such as y-parameters, z-parameters, and h-parameters. Network analyzers are often used to characterize two-port networks such as amplifiers and filters, but they can be used on networks with an arbitrary number of ports.Figure 1 shows the block diagram of network analyzer.
Figure 1: Block Diagram of a Network Analyzer1
The test set takes the signal generator output and passes it to the device under test, and it pass the signal to be measured to the receivers.It often splits a reference port for the incident wave. In a SNA, the reference channel may go to a diode detector (receiver) whose output is sent to the signal generator’s automatic level control. The result is better control of the signal generator’s output and better measurement accuracy. In a VNA, the reference channel goes to the receivers; it is needed to serve as a phase reference.The testset of a network analyzer functions to isolate the incident and reflected waves from the DUT connected to the analyzer.
Directional coupler is four port network that is designed to divide and distribute power
2. They couple a defined amount of the electromagnetic power in a transmission line to
a port enabling the signal to be used in another circuit. Directional couplers are most frequently constructed from two coupled transmission lines set close enough together such that energy passing through one is coupled to the other. This technique is favoured at the microwave frequencies where transmission line designs are commonly used to imple-ment many circuit elements. Directional couplers have many applications. These include providing a signal sample for measurement or monitoring, feedback, combining feeds to and from antennas, antenna beam forming, providing taps for cable distributed systems such as cable TV, and separating transmitted and received signals on telephone lines.The directional coupler in a network analyzer has to provide a path for the reference RF signal from the source to the load (DUT), and then provide another path for the signal reflected from the load to the reflected power detector.
Figure 2: Directional Coupler
Directional couplers are categorized as passive reciprocal networks. A directional cou-pler is used for isolating, eliminating or combining signals in microwave signal routing and radio frequency. The ports in the directional coupler are: Coupled , Input, Transmitted, Isolated. A special design is put into use by which the input power is split between the coupled and output ports in a specific ratio known as the coupling ratio. Depending on the application for which it is used, the key specifications of the directional coupler varies. The parameters/specifications which are mostly varied are the coupling factor, transmis-sion loss, low variation of the coupling attenuation, high directivity and input power. The features which are desired for e?cient coupler are high directivity, good impedance and wide operational bandwidth. But the performance of a directional coupler is computed using the directivity factor. There are di?erent types of directional couplers like single, dual directional, coaxial, waveguide and even combination types.
Moore’s law is the observation that the number of transistors in a dense integrated
circuit doubles about every 18 months. Alternatively size of transistor will decrease by p
factor of 2: