by Leo G. Maloratsky, Aerospace Electronics Co., Indialantic FL
In building a strategy for effective integrated-circuit design, it is important to understand the characteristics of different RF and microwave planar dividers/combiners. Optimization of the design process for dividers and combiners can reduce unnecessary costs and design iterations, thus allowing designers time to improve the quality of the product. The design process includes various stages from analysis of requirements to final design documentation, balancing and trading-off factors such as electrical performance, size, cost, etc.
Definitions of Dividers/Combiners
Dividers and combiners are used frequently in RF and microwave integrated circuits as separate components or as parts of devices such as attenuators, phase shifters, mixers, amplifiers, modulators, high power transmitters and beam forming networks for antenna arrays.1 A reciprocal divider can provide an equal or unequal power split between two or more channels. Because of their reciprocity, these circuits may also be employed to combine a number of oscillators or amplifiers to a single port. However, the combining mode has some particularities. To get lossless combining, input signals should be coherent and of equal amplitudes.
The major parameters that define planar RF and microwave dividers/combiners are bandwidth (BW), power division (m), relative output phases (Δφ), phase imbalance, amplitude imbalance, insertion loss (IL), matching (VSWR) or return loss (RL), isolation (ISO), power handling capacity, total number of inputs/outputs, integration level and cost. Insertion loss is the ratio (in decibels) of input power to output power with reflectionless terminations connected to the ports of the divider/combiner. The insertion loss of a printed divider/combiner is a combination of conductor loss, dielectric loss, isolation loss and mismatching loss. The relative phase difference can be quadrature (Δφ = 90°) or in-phase/out-of-phase (Δφ = 0° or 180°). The divider/combiner bandwidth is the range of frequencies for which a parameter falls within a specified limit with respect to certain characteristics.
Dividers/combiners can be classified according to the following performance characteristics:
Interested in reading the complete article?
A complete view is available to registered MWJournal.com members.
Registration is FREE! Click here to register.
Already registered? Login >>
Already a member, but don't remember your username and/or password? Click here.
If you are a Microwave Journal monthly subscriber and would like to enable FREE Website access, please click here.
