Butler matrix used for wireless test applications using microstrip technology |Ranatec

Butler Matrix

The RI 3101 Butler matrix is a beamforming network which typically is used to feed a phased array of antenna elements. It controls the directions of a beam, or beams, of a radio transmission. The beam direction is controlled by switching power to the desired beam port.

The RI 3101 Butler matrix is designed for wireless test applications using microstrip technology. The design and optimization was used based on computer simulations using ADS and HFSS. The hybrid couplers, cross-couplers, and the phase shifters are optimized one by one to get the best performances.

An important feature that makes RI 3101 Butler matrix attractive is the speed over mechanical scanning systems. In transmit mode it delivers the full power of the transmitter to the beam, and in receive mode it collects the signal from each of the beam directions with the full gain of the antenna array.

Since the Ranatec butler matrix 8×8 is both reciprocal and passive, it can be used for both transceiver and receive applications.

8 x 8 Butler Matrix, 8 GHz

Specification

Frequency range 2.4-8 GHz  
Return loss (50 Ohm reference) 13 dB typical VSWR = 1.6
Output phase deviation
from nominal
<±10° typical  
Output amplitude deviation
from nominal
<±3 dB Nominal is equal amplitude in the 8 output ports
Insertion loss <13 dB 9 dB of total 13 dB is splitting loss (1:8)
Isolation >13 dB Measured as isolation between input ports
Maximum power 5 W Total input power (average)
Number of input ports 8  
Number of output ports 8  
Connector type SMA-F  
Dimensions (WxLxT) 138x131x19 mm  
Mass 0.78 kg  

Mechanical Outline

Butler matrix used for wireless test applications using microstrip technology | Ranatec

Applications

MIMO testing for Bluetooth and Wi-Fi

The RI 3101 Butler Matrix supports multichannel MIMO testing for 8+8 antenna ports over a large frequency range – the conventional Bluetooth and Wi-Fi bands at 2.4 and 5 GHz are supported as well as an extension up to 8 GHz.

The RI 3101 Butler Matrix simulates real-world conditions, directing coverage over distances and across obstacles. This enables true testing of smartphones, sensors, routers and other access points. The RI 3101 Butler Matrix plays an important role in development of Wi-Fi 6 products.

Wi-Fi 6 is the most recent Wi-Fi network protocol and is a substantial upgrade over its predecessor. Wi-Fi 6 is faster due to technologies like traffic prioritization, beamforming and OFDMA. OFDMA (Orthogonal Frequency Division Multiple Access) works by subdividing channels into subcarriers and allowing for transmission to multiple endpoints (devices) at the same time. A Wi-Fi 6 router can send different signals in the same transmission window.

This results in a single transmission from the router being able to communicate with several devices, instead of each device having to wait for its turn as the router serves up the data across the network.

Beam switching and beam steering

The RI 3101 Butler matrix controls the direction of your antenna beam, using spatial filtering, creating directional signal transmission or reception. Beam switching (steering the beam) is achieved by altering the input power port, 1-8. Typically a switch matrix is applied in front of the Butler matrix to control the power input.

The Ranatec Butler matrix is designed for high precision applications, where high isolation and low out-of-phase is of importance.

The resulting antenna beam steering and butler matrix beamforming will consequently have high accuracy and suitable for the most demanding applications.

Ordering

RI 3101 Butler Matrix

FAQ

A Butler matrix is a beamforming network. It is typically used to feed a phased array of antenna elements and controls the direction of a beam, or beams, of a radio transmission.
Beamforming is a technique that focuses a wireless signal towards a specific receiving device, creating a more direct connection that is faster and more reliable than having a signal spread in all directions from a broadcast antenna.
A Tunable notch filter is used to remove a specific radio frequency, whereas the purpose of a Butler matrix is to control the direction of a beam, or beams, of radio transmissions.
“The Butler matrix is a type of beamforming network used to control the direction of a beam, or beams of a radio transmission. The characteristics of the Butler matrix include:

– X inputs and X outputs, where X is usually 4, 8 or 16
– The inputs are isolated from each other
– The phases of X outputs are linear with respect to their position so the beams are tilted off the main axis
– None of the inputs provides a broadside beam
– The phase increment between the outputs depends on which input is used”

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