Compare the pros and cons of the following three planar transmission lines,i.e.microstrip, stripline,and CPW.
Advantages of cpw
• With regards to routine solitude, you can get excellent solitude using CPW, because there are always RF reasons between records. Many illustrations of high-isolation RF changes have used based CPW to get 60 dB solitude or more.
• The benefits of having a dense substrate is noticed when you fabricate CPW MMICs. The price of rear handling (thinning, via imprinted, rear plating) is removed. Many organizations that are currently creating GaN gadgets are utilizing CPW so they can focus on system technological innovation and not have to determine how to imprinted vias in rubber carbide or pearl. With GaN technological innovation, wafer pieces are on the transaction of 12 mils dense, so for X-band gadgets, the dimension the processor is well printed to 10 or 15 mil alumina.
• For GaAs MMICs, wafer pieces begin out at 25 mils. If a CPW processor is installed face-up, a serious dimension discontinuity can outcome. The way to get around this issue is to use flip-chip technological innovation, which is the benefits or a drawback based on who you discuss to!
• The floor inductance for shunt components is quite low for CPW, in comparison to microstrip programs. This is because the RF floor is "right there", and you don't have to routine via gap to get connected to it (vias add inductance).
• As described preciously, if you want to create lightweight tour using filter transmitting collections, you must business off RF reduction. CPW tour can be lossier than similar microstrip tour, if you need a lightweight structure.
• In conditions of routine dimension, CPW is at a drawback in comparison to a stripline of microstrip routine, because it's efficient dielectric continuous is reduced (half of the areas are in air).
• Ground ties are always required to tie the two reasons together in CPW, or strange factors can occur. These are especially essential around any discontinuity, such as a tee 4 way stop.
• Unintended unwarranted transmitting ways can also occur. In a parallel-plate method, the substrate functions like a dielectric-filled waveguide, and EM power develops along random routes. Don't get us incorrect, if you know how to prevent this mistake, CPW performs great.
Advantages of Striplines
• Stripline is a TEM (transverse electromagnetic) transmitting range press, like talk. The stuffing aspect for talk is oneness, and "Keff" is similar to ER. This implies that it is non-dispersive. Whatever tour you can create on microstrip (which is quasi-TEM), you can create better using stripline, unless you run into manufacturing or dimension restrictions. Stripline filtration and couplers always provide better data transfer usage than their alternatives in microstrip, and the roll-off of stripline BPFs can be quite symmetrical (unlike microstrip). Stripline has no reduced cutoff regularity (like waveguide does).
• But is stripline really non-dispersive at all frequencies? Study about the low regularity distribution of TEM press, something to think about when you are developing between 10 MHz and 1 GHz.
• Another benefits of stripline is that amazing solitude between nearby records can be carried out (as compared to microstrip). The best solitude outcomes when a picket-fence of vias encompasses each transmitting range, spread at less than 1/4 wave length. Stripline can be used to path RF alerts across each other quite quickly when balanced out stripline is used.
• Disadvantages of stripline are two: first, it is much more complicated (and more expensive) to create than microstrip, some old people would even say it's a missing art. Lumped-element and effective elements either have to be hidden between the groundplanes (generally a challenging proposition), or changes to microstrip must be applied as required to get the elements onto the top of the panel.
• The second drawback of stripline is that because of the second groundplane, the remove sizes are much smaller for a given impedance (such as 50 ohms) and panel width than for microstrip. A typical respond to issues with microstrip tour is to make an effort to turn them to stripline. You will end up with a panel width that is four periods that of your microstrip panel to get comparative transmitting range reduction. That indicates you'll need 40 mils dense stripline to substitute ten mil dense microstrip. This is one of the factors that softboard producers provide so many thicknesses.
Advantages and disadvantages of microstrip.
Advantages:
• Cheap to fabricate.
• Easy to manufacture.
• Microstrip patch antennas are efficient radiators.
• It has a support for both linear and circular polarization.
• Easy in integration with microwave integration circuits.
Disadvantages:
• Low impedance bandwidth.
• Low gain.
• Extra radiation occurs from its feeds and junctions.
• Excitation of surface waves.
• Size of micro strip antenna comes in both advantages and disadvantages but there are some applications where the size of microstrip antenna is too large to be used.
Q2). Considerthe two-port Sparameter network shown below:
Derive [S]of the resistive network at 60GHz.
The abbreviation S has been derived from the word scattering.
For high frequencies, it is convenient to describe a given network in terms of waves rather than voltages or currents. This permits an easier definition of reference planes.
For practical reasons, the description in terms of in- and outgoing waves has been introduced.Now, a 4-pole network becomes a 2-port and a 2n-pole becomes an n-port. In the case of an odd pole number (e.g. 3-pole), a common reference point may be chosen, attributing one pole equally to two ports. Then a 3-pole is converted into a (3+1) pole corresponding to a 2-port.As a general conversion rule for an odd pole number one more pole is added.
Let us start by considering a simple 2-port network consisting of a single impedance Z connected in series (Fig. 1). The generator and load impedances are ZG and ZL, respectively. If Z = 0 and ZL = ZG (for real ZG) we have a matched load, i.e. maximum available power goes intothe load and U1 = U2 = U0/2.
Please note that all the voltages and currents are peak values. The lines connecting the different elements are supposed to have zero electrical length. Connections with a finite electrical length are drawn as double lines or as heavy lines. Now we need to relate U0, U1 and U2 with a and b.
The S-matrix is only defined if all ports are matched (=terminated with the necessary load)
This is important for measurements and simulation!The matching load does not have to be equal for all ports! (not necessarily always 50 Ohm)
Example: Transformer with N1:N2=1:2
The impedance scales with the square of this ratioif there is a 50 Ohm impedance on one side, the other side has either an impedance of 12.5 Ohm (down transformer) or 200
The entries in the S-Matrix can have a different format such as length and phase, real and imaginary part etc. More information will be given in the lecture on Measurements
2) Consider the wireless receiver front-end shown below:
a) Please devise a single-stub matching network to achieve maximum power transfer using open shunt stub (please show your schematic and leave all units in terms of wavelength). Use ZY-Chart only!
b) What is the type of component associated with the open shunt stub based on your matching network?
c) What is the value of the component that you identified in (b) at 5 GHz (assume stripline implementation with ?r = 4)?