- Buyers Guide
Military Microwaves Supplement
Published March 9, 2006
I am trying to design a microstrip or CPW coupler from 2 to 18 GHz. I was thinking of either a multisection branch line coupler or a multisection coupled line coupler, but I would like to know your opinion. Which is the best solution for such a wideband coupler?
From: Mahesh Patel
I am starting to manufacture a coaxial cable assembly. What assembly precautions should I take for assembly up to 26.5 GHz flexible and semi-rigid type cables? I want to make test assemblies with good VSWR and insertion loss.
From: Samuder Gupta, Solid State Physics Lab
I have designed an oscillator for L-band using GaAs MESFET with the o/p taken from its source and then fed to an MPA to increase the o/p power. The o/p power is maximum when the S22 of the amplifier MESFET is off matched with a 50 ohm load. I am having difficulty understanding this. Please advise.
From: Ahmed Elzayat, ETS
I am designing a miniaturized halfwave length coupled filter with Tx zeros at finite frequencies. I am using ADS momentum as a simulation tool. The filter has a central frequency of 5.225 GHz and a fractional bandwidth of about 3 percent. I am having trouble with the losses (my current loss is around 4 dB in the middle of the band). I tried to use a perfect conductor, but still have about 1.6 dB of loss in the middle of the band. What are the loss mechanisms in these types of designs and what are the design tradeoffs?
I would like to share my understanding on Mr. Tapas' question regarding insertion loss and return loss of a filter. In terms of S-parameters, return loss is generally known as S11, which is defined in dB, while insertion loss is generally known as S21 (in dB). Since a filter is a passive circuit, insertion loss is commonly known as circuit loss or attenuation from input to output.
From: Oscar Zalamia, RF Engineering and Electromagnetics
What happens to external noise (atmospheric, gallactic and man-made) when it goes through a low noise amplifier (LNA)? Can a LNA reduce the external noise level through filtering, amplification or impedance matching? I was led to believe that a LNA can only affect internal (static and thermal) noise but not external noise; that is, the external noise floor cannot be reduced. I appreciate your insight into this subject.
What is your definition of the difference between a diplexer and duplexer? A simple question, but searching the Internet on the subject has made my brain hurt. Vendor sites, dictionary sites, wireless sites, amateur radio sites and microwave sites all seem to have a different take. Some say gas discharge tubes, switches and circulators are duplexers while others distinguish between "di" and "du" apparently only on whether they are combining or dividing multiple signals.
From: Justin Schaub, Lockheed Martin - MS2, Eagan MN (Tactical Systems)
One of the biggest obstacles I have run into several times in creating a link budget between radio systems, antenna to antenna in various situations:
Is there one recommended source to learn a correct and accepted way to create link budgets?
From: Mrs. Mahadev, SAHA
How can I design a linear phase shifter of 360 degrees using a varactor diode and circulator at 360 MHz?
Dear Mrs. Mahadev,
From: Paul Grayson, American Industrial Magic LLC
I have been promoting the DARPA Grand Challenge race and working on three vehicles for about four years now. Do you have any suggestions about how I might find people with a background like yourself who would be interested in helping me develop the sensors that my all-volunteer project needs? Or perhaps sponsors that would allow me to hire the people my team needs? My contact information is as follows: Paul Grayson, Chief Engineer, American Industrial Magic LLC, Farm Vehicle Automation and Racing, 390 4 Mile Road, S. Traverse City, MI 49686-8411 (231) 946-0187, e-mail: email@example.com or visit http://www.aimagic.org.
I am studying the wide angle impedance matching and scan blindness in microstrip antennas for electronic scanning using IE3D software. I would like to use a waveguide simulator for this purpose. Though waveguide simulators are well established for open ended waveguides and other similar structures, I am at large in using the same as far as the microstrip antenna. This is due to the presence of a dielectric substrate. Does the size of a waveguide (simulator) also depend on the dielectric constant? Are there any articles discussing the use of waveguide simulators for infinite array studies on microstrip antennas?
From: Prasanna, Thagaraja College of Engineering and Technology
I am a novice trying to explore the elliptic filter design in microwave filters, but could not find any appropriate material on the Internet or in books. Could you please help me to understand this topic and also guide me to where can I find reading material relevant to this topic?
I am searching for an equation to calculate the cascade compression point (P1dB) of a cascade system with amplifiers, filters, attenuators, etc. I would prefer to utilize it in a homemade spreadsheet. Could you provide any direction?
Harlan Howe, Jr. received his BS degree in optics from the University of Rochester in 1957. He has been actively engaged in the microwave industry for 48 years, first as a design engineer and then as an engineering manager. In 1990 he became the publisher/editor of Microwave Journal. He retired as publisher in 2001, but remains the editor. He is a Life Fellow of IEEE, past president of MTT-S and the recipient of an IEEE Third Millennium Medal in 2000 and the MTT-S Distinguished Service Award in 2005.
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