This paper introduces a review of the design and analysis of different 
designs for tunable/nonreciprocal and compact-size microwave 
couplers. The presented couplers are designed based on composite right/
left-handed (CRLH) transmission lines and in the planar structures 
made of ferrite substrates. The CRLH transmission lines have many 
attractive features of nonlinearity operation with the frequency that 
can help the designers to present a compact and different frequency 
functionality of the presented devices. Moreover, the ferrite substrates 
are anisotropic media that help the designer to introduce nonreciprocal 
devices. Mixing the design aspects from CRLH transmission lines and 
the ferrite substrates can lead to novel properties. According to this 
approach, we present a collecting review for many microwave couplers 
with small size/ different frequency functionalities and different tunable/
non-reciprocity properties. The reviewed designs are implemented in 
coplanar waveguides hosting planar structures that help for reducing the 
needed DC magnetic bias for the ferrite substrates for its operation. All 
the reviewed couplers are presented in a detailed explanation of theory 
parts and complete circuit model and electromagnetic simulations and 
finally experimental measurements.