Aerospace & Defense Technology - April 2021 - 22

RF & Microwave Technology

left block shows the Receiver-Exciter if
the system is a radar or a modem if it is a
communications system. This block generates the signals used for transmitting
and houses the receivers in receive mode.
The next block represents the beamforming network, which is responsible
for routing the transmitted and received
signals to the many T/R modules and radiators in the system. The beamforming
network has a small number of (or one)
input signals and many output signals.
The beamformer drives the next block,
which are the system's T/R modules.
These modules are responsible for controlling the amplitude and phase of the
transmitted and received signals to the
individual elements of the antenna.
Principle of Beamforming & Beam steering
1.Fixed antenna spacing d
2.Choose direction
3.Set phase shifts

Drilling down to the individual building blocks of the system, let's start with
the analog beamforming network (Figure 3). These are usually made of passive
structures like splitters and combiners.
The structures are configured as a distribution network by combining these
into the desired topology for the specific system. They are usually manufactured out of a multilayer PCB, where the
individual passive structures can be
printed and interconnected using stripline and micro-strip structures.
The beamforming networks need to
be tested for insertion loss and insertion
phase across their many paths. The performance requirements are usually
quite tight - typically, measurement
Beam steering (Phase Shift)
=0

10

Sidelobe Suppression
10

=90

Broadside
0

0

-10

-10

-20

-20

-30

-30

=90

Linear Taper

To far-field

-40

-40

-50

-50

0
Angle (degrees)

50

-50
-50

0
Angle (degrees)

Antennas
Phase Shifters

50

tolerances of 0.1 dB and a few degrees. It
becomes difficult to hold this uncertainty as the frequency increases and
becomes very difficult as the frequencies increase above 8 GHz. Multi-port
VNAs are the measurement tool of
choice to characterize these networks.
Figure 4 shows an example block diagram of a T/R module. The upper leg is
for transmitting while the lower leg is
used for receiving. There are input and
output switches to change from transmit or receive modes. The amplitude
weighting and phase shifting is done
using the variable gain amplifiers and
phase shifters in each leg. These are controlled digitally and can be varied over a
large value of states. There is also a PA
used for transmit and an LNA used for
receive. These components also need to
be characterized for noise figure, compression, intermodulation, and linearity.
In R&D, each T/R module design needs
to be tested and characterized over each
one of these states. For many designs,
each T/R module may also require testing
in production. Combining the large
number of T/R modules with many potential gain/phase states drives the need
for improving test throughput times.

Attenuators

Test Systems
Figure 1. Principles of phased array beamforming and beam steering.

T/R

Receiver
Exciter or
Waveform
Mod-Demod

T/R
Analog
Beamformers

100's to
1,000's of
Elements
per system

T/R

T/R

Figure 2. Generic phased array block diagram.

Figure 3. Analog beamforming networks (RF manifolds).

22

www.aerodefensetech.com

Cov

ToC

The comprehensive characterization
of T/R modules and active DUTs requires
test equipment that supports diverse test
scenarios. For example, test equipment
must be able to provide and handle both
very high and very low powers without
any modifications to the test setup or
perform intermodulation and group
delay measurements on converters with
an embedded local oscillator (LO).
The extension unit adds additional
signal conditioning to the network analyzer. This offers several economic and
technical benefits. If several network
analyzers are available to perform various tasks, not all analyzers need to be
equipped with all options. This means
that fewer options are needed for the
network analyzer itself, thus reducing
investment costs. The extension unit offers another advantage by providing additional protection for the network analyzer during measurements, as its
high-power front end may be used instead of the VNA ports.
Aerospace & Defense Technology, April 2021


http://www.aerodefensetech.com http://www.abpi.net/ntbpdfclicks/l.php?202104ADTNAV

Aerospace & Defense Technology - April 2021

Table of Contents for the Digital Edition of Aerospace & Defense Technology - April 2021

Aerospace & Defense Technology - April 2021 - Intro
Aerospace & Defense Technology - April 2021 - Sponsor
Aerospace & Defense Technology - April 2021 - Cov1
Aerospace & Defense Technology - April 2021 - Cov2
Aerospace & Defense Technology - April 2021 - 1
Aerospace & Defense Technology - April 2021 - 2
Aerospace & Defense Technology - April 2021 - 3
Aerospace & Defense Technology - April 2021 - 4
Aerospace & Defense Technology - April 2021 - 5
Aerospace & Defense Technology - April 2021 - 6
Aerospace & Defense Technology - April 2021 - 7
Aerospace & Defense Technology - April 2021 - 8
Aerospace & Defense Technology - April 2021 - 9
Aerospace & Defense Technology - April 2021 - 10
Aerospace & Defense Technology - April 2021 - 11
Aerospace & Defense Technology - April 2021 - 12
Aerospace & Defense Technology - April 2021 - 13
Aerospace & Defense Technology - April 2021 - 14
Aerospace & Defense Technology - April 2021 - 15
Aerospace & Defense Technology - April 2021 - 16
Aerospace & Defense Technology - April 2021 - 17
Aerospace & Defense Technology - April 2021 - 18
Aerospace & Defense Technology - April 2021 - 19
Aerospace & Defense Technology - April 2021 - 20
Aerospace & Defense Technology - April 2021 - 21
Aerospace & Defense Technology - April 2021 - 22
Aerospace & Defense Technology - April 2021 - 23
Aerospace & Defense Technology - April 2021 - 24
Aerospace & Defense Technology - April 2021 - 25
Aerospace & Defense Technology - April 2021 - 26
Aerospace & Defense Technology - April 2021 - 27
Aerospace & Defense Technology - April 2021 - 28
Aerospace & Defense Technology - April 2021 - 29
Aerospace & Defense Technology - April 2021 - 30
Aerospace & Defense Technology - April 2021 - 31
Aerospace & Defense Technology - April 2021 - 32
Aerospace & Defense Technology - April 2021 - 33
Aerospace & Defense Technology - April 2021 - 34
Aerospace & Defense Technology - April 2021 - 35
Aerospace & Defense Technology - April 2021 - 36
Aerospace & Defense Technology - April 2021 - 37
Aerospace & Defense Technology - April 2021 - 38
Aerospace & Defense Technology - April 2021 - 39
Aerospace & Defense Technology - April 2021 - 40
Aerospace & Defense Technology - April 2021 - 41
Aerospace & Defense Technology - April 2021 - 42
Aerospace & Defense Technology - April 2021 - 43
Aerospace & Defense Technology - April 2021 - 44
Aerospace & Defense Technology - April 2021 - 45
Aerospace & Defense Technology - April 2021 - 46
Aerospace & Defense Technology - April 2021 - 47
Aerospace & Defense Technology - April 2021 - 48
Aerospace & Defense Technology - April 2021 - Cov3
Aerospace & Defense Technology - April 2021 - Cov4
https://www.nxtbook.com/smg/techbriefs/22ADT09
https://www.nxtbook.com/smg/techbriefs/22ADT08
https://www.nxtbook.com/smg/techbriefs/22ADT06
https://www.nxtbook.com/smg/techbriefs/22ADT05
https://www.nxtbook.com/smg/techbriefs/22ADT04
https://www.nxtbook.com/smg/techbriefs/22ADT02
https://www.nxtbook.com/smg/techbriefs/21ADT12
https://www.nxtbook.com/smg/techbriefs/21ADT10
https://www.nxtbook.com/smg/techbriefs/21ADT09
https://www.nxtbook.com/smg/techbriefs/21ADT08
https://www.nxtbook.com/smg/techbriefs/21ADT06
https://www.nxtbook.com/smg/techbriefs/21ADT05
https://www.nxtbook.com/smg/techbriefs/21ADT04
https://www.nxtbook.com/smg/techbriefs/21ADT02
https://www.nxtbookmedia.com