Test & Measurement

Application Card | 01.00

Multichannel coherent signal generation

Your task

Testing multi-antenna systems such as phased array or

beamforming antennas requires a test system capable of

providing multiple signals with constant phase relation-

ships between them. The coherent test signals must have

a specific or definable phase difference (delta phase) and

definable amplitude. Some of the challenges for such a

test system include compactness, phase control capabil-

ity and simplicity in handling. In particular, phase stability

between the channels is of importance. Many applications

in the A & D direction finding and mobile communications

beamforming sectors demand that the phase relationships

between channels be constant over time with minimal de-

viations, for example as little as < 1° phase drift. Such high

phase stability can only be achieved when using a com-

mon synthesizer signal (local oscillator, LO) for all signal

generators in a test system.

T & M solution

Rohde & Schwarz signal generators present a compact

easy-to-use solution for generating phase-coherent sig-

nals. The generators R&S®Sxx-B90 phase coherence op-

tion enables LO coupling of multiple instruments by dis-

tributing the synthesizer signal of one instrument to the

others. Different generator models can be coupled to op-

timally fit user requirements in terms of number of phase-

coherent channels and RF frequency range.

For example, generating four phase-coherent RF signals

up to 20GHz requires one R&S®SMW200A two-channel

vector signal generator and two sets of R&S®SGS100A

RF source and R&S®SGU100A upconverter. The whole

setup acts as one unit, conveniently controlled via the

intuitive R&S®SMW200A touchscreen. The vector signal

generator generates two 20GHz phase-coherent chan-

nels and also provides the I/Q baseband signals and the

LO signal for the two external RF outputs (R&S®SGS100A/

R&S®SGU100A combinations). The relative phases be-

tween all four RF channels are set digitally in the baseband

on the R&S®SMW200A. The four-channel system is there-

fore easy in handling and capable of controlling the phase

relationships in a straightforward way.

A perfectly matched set of Rohde & Schwarz signal

generators generates multiple phase coherent

signals up to 40GHz.

Multichannel

coherent signal

generation

Compact, scalable test solution with phase-coherent RF outputs.

Excellent phase stability between channel 1 and channels 2/3/4

respectively at 20GHz and constant instrument temperature (top trace).

SMW200A_multichannel_coherent_ac_en_3607-1194-92.indd 1 23.02.2015 20:50:25

Test setup to generate four phase-coherent channels at 20GHz with phase control capability and excellent

phase stability

¸SGU-Z4

connection kit

RF signal 1

RF signal 2

RF signal 3

Device

under test

¸SGU-Z4

connection kit

¸SMW200A vector signal generator

I/Q data USB/LAN control

¸SGS100A SGMA RF source with

¸SGU100A SGMA upconverter

I/Q

data

USB/LAN

control

RF signal 4

Rohde & Schwarz GmbH & Co. KG

Europe, Africa, Middle East | +49 89 4129 12345

North America | 1 888 TEST RSA (1 888 837 87 72)

Latin America | +1 410 910 79 88

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www.rohde-schwarz.com

customersupport@rohde-schwarz.com

R&S® is a registered trademark of Rohde & Schwarz GmbH & Co. KG

Trade names are trademarks of the owners

PD 3607.1194.92 | Version 01.00 | February 2015 (as)

R&S®SMW200A; Multichannel coherent signal generation

Data without tolerance limits is not binding | Subject to change

3607.1194.92 01.00 PDP 1 en

360711

9492

High phase stability among all RF signals requires a shared

LO signal. The easiest way to distribute the LO signal is by

daisy-chaining. Each cascaded instrument amplifies the

LO signal to maintain a proper LO signal level. To be less

prone to temperature effects, the LO signal frequency is a

factor of four lower than the wanted RF frequency, contrib-

uting to a better phase stability. The LO frequency is multi-

plied automatically by the external RF outputs.

Due to the shared LO signal, the phase stability is

excellent. For example, at constant ambient temperature

the measured phase drift between the channels is < 1°

over a minimum of 90 min. at 20GHz RF frequency(see

diagram).

The Rohde & Schwarz test solution is scalable to optimally

meet customer needs. The number and type of generators

needed depends on the required number of channels and

RF frequency.

Examples of different setups

Number of

channels

Frequency

(max.)

Signal generators

R&S®

Total HU

8 6GHz 1 × SMW, 6 × SGT 7

4 12.5GHz 1 × SMW, 2 × SGS 5

4 20GHz 1 × SMW, 2 × SGS, 2 × SGU 6

8 20GHz 2 × SMW, 4 × SGS, 4 × SGU 12

3 40GHz 1 × SMW, 2 × SGS, 2 × SGU 6

The small form factor and easy handling of this test solu-

tion are unique on the market. The generators are conve-

niently controlled via one user interface that also allows

adjustment of the RF signal characteristics, including

phase relationships. Its compact size and excellent phase

stability make this multichannel solution ideal for generat-

ing phase-coherent signals.