T/R MODULES
designs built to your specifications
A Transmit-Receive (T/R) module forms the basis of a time-duplexed RF front end, sitting immediately behind the antenna array elements. They are found in beamforming arrays used for radar and communication (e.g. 5G, satellite) systems, often where active beam (or null) steering is desired. At a minimum, these modules consist of a low noise amplifier, a power amplifier and a transmit-receive switch. On top of this, we can build in various levels of "intelligence" that permit the TR module to take over some of the beam steering tasks, such as automated scanning and beam switching. Digital control & telemetry interfaces and power control systems are often incorporated.
T/R modules are often tightly integrated with specialized antenna elements. Depending on the application, these antenna elements can be planar (patch, Vivaldi, etc.) or non planar (helix, etc.). Multiple polarization capability is sometimes incorporated in an antenna array. OMP can develop custom antennas and T/R modules up to X/Ku band using commercially available components to suit your application.
The Transmit-Receive (T/R) module is an essential subsystem of a time duplexed RF front-end. RF systems ranging from 5G communications to large phased array radar systems will use T/R modules to control transmit and receive antenna functions. In their most basic form, T/R modules consist of an antenna switch, a transmit power amplifier (PA) and a receive low noise amplifier (LNA, See Illustration 1). This is the type of T/R module you may find incorporated in a simple time duplexed radio. A phased array radar system may incorporate phase shifting and amplitude control as well, for the purpose of steering the beam and shaping the antenna pattern (Illustration 2). In the case of antenna arrays, T/R modules are tightly integrated with the elements of the antenna array.
Having the T/R module physically close to the radiating elements permits maximum transmitting efficiency because transmission losses between the final PA and the antenna are minimized. Furthermore, the receiver sensitivity is enhanced by minimizing noise produced by transmission losses in the antenna feed network.
Stacking T/R modules together with their associated antenna elements permits the construction of adaptive electronically steerable arrays. A one-dimensional (linear) array takes the form of a “plank”, which, when stacked together with other planks, forms a two-dimensional array (Illustration 4).
Each T/R module has its own phase and amplitude weighting that can be updated in real time to permit beam scanning and target tracking functionality. Both single beam and monopulse operation is readily implementable using such modules.
Adaptive electronically scanned arrays (AESA)
When we stack together many of these T/R modules with their antenna elements, as seen in Figure 4, the phase and amplitude control allowed by each T/R module permits fully active beamforming. Terrestrial communication systems (e.g. 5G) and satellite systems use this capability to track user terminals and reduce interference by steering nulls in the direction of jammers/interferers. Radar systems use AESA functionality for beam scanning (reducing or eliminating the need for mechanical antenna scanning) as well as target tracking in civilian and military applications.
Key design aspects of AESAs are the antenna element spacing, RF signal distribution, thermal management and data interface. The element spacing must be carefully selected to prevent the production of unwanted grating lobes in the antenna pattern. The spacing determines the dimensions of the T/R module enclosure. For X band and above, it is very important that the T/R system components be very compact, such that they can physically fit in the space defined by the antenna spacing.
The RF signal distribution system must exhibit as little loss as possible, especially between the T/R module and antenna.
Thermal management becomes an issue when transmitter power exceeds a watt or two. Some form of cooling (air, fluid) may be needed under many circumstances, particularly if high duty-cycle, extended operation in hot environments is expected. A high-speed data interface is critical when real-time updates of T/R module phase/amplitude data are needed for scanning and tracking operations.
To Summarize:
-
T/R modules perform fundamental time-domain duplexing function for many communications and radar applications.
-
When phase and amplitude functionality is included, the possibility of electronic beam (and null) steering becomes possible.
-
Electronic beam steering reduces or eliminates the need for mechanical antenna scanning.
-
Placing T/R modules close to radiating elements enhances antenna system efficiency in both transmit and receive modes.
-
Active arrays are easily scalable, permitting the use of large antenna apertures without the bulk and mass that a large reflector antenna would entail.
-
In many cases, antenna array elements are realizable using low-cost printed circuit board manufacturing techniques.