This manufacturer has expanded its expertise in high-frequency switches and amplifiers into multifunction assemblies that meet demanding military requirements.
Maximizing engineering resources is of utmost importance to most military-electronics contractors, to the point where many of the largest suppliers have turned to traditional RF/microwave component houses in search of subassembly integration. One of the long-running RF/microwave component suppliers that has learned how to blend its component business with its expanding subsystem integration skills is Daico Industries (www.daico.com), which boasts a growing portfolio of multifunction assemblies to its credit.
Daico Industries, with a long history and solid reputation as a designer and manufacturer of RF/microwave switches, has combined that switch expertise with other design disciplines, including low-noise amplifiers (LNAs), power amplifiers (PAs), power combiners, and phase shifters, to assemble complex subassemblies for a wide variety of demanding military applications, including avionics, space, and shipboard systems. The assemblies range in complexity from two- or three-function "supercomponents" to advanced receiver/transmitter subassemblies with integral power supplies and digital interfaces.
For example, the model CDX0947 connectorized single-pole, single-throw (SPST) switch and amplifier blends some of the firm's traditional switch technology with growing skills in narrowband and broadband amplifier design. The component-sized unit packs a TTL driver, high-speed nonreflective SPST switch, and broadband amplifier into a housing measuring just 1.50 x 1.05 x 0.34 in. The multifunction component covers a frequency range of 20 to 2000 MHz with typical gain of 14 dB from 20 to 1000 MHz, 13 dB from 1000 to 1500 MHz, and 6 dB from 1500 to 2000 MHz. By including the switch, it features isolation of typically 80 dB to 1000 MHz, 57 dB from 1000 to 1500 MHz, and 42 dB from 1500 to 2000 MHz. The switching speed is typically 21 ns. The 50-ohm unit features typical through VSWR of 1.50:1 and terminated VSWR of 1.20:1 with typical current requirements of 200 mA at +15 VDC and 5 mA at -5.2 VDC. The unit is designed for operating temperatures from -55 to +85°C.
For a space application, the company developed the model CHD09122 output signal-distribution unit using diode switches and GaAs field-effect-transistor (FET) amplifiers to cover the 20- to-4000-MHz range. Designed as a thin, plug-in card assembly, the signal-distribution unit is radiation tolerant and hermetic to withstand the rigors of deep-space operation.
On a slighter higher level of integration, the firm's model DP0877 is a phaseshifter/ amplifier/switch assembly (see figure) that provides amplified output signals from 1300 to 1700 MHz with total phase-control range of 315 deg. Phase can be shifted under digital control with least-significant bit (LSB) of 45 deg., while the output signals can be blanked under the control of the switch with 300-ns typical switching speed. It features 18 dB gain with ±1 dB gain flatness, and a noise figure of typically 10 dB. The phase accuracy is ±5-deg.
The multifunction assembly integrates GaAs FET amplifiers, a monolithicmicrowave- integrated-circuit (MMIC) SPST blanking switch, passive power divider, three-section phase shifter, and TTL and ECL drivers. It is supplied in a multipin package measuring 2.57 x 1.99 x 0.23 in. The ECL control is used for the phase shifter while the TTL control is used for the blanking switch. The assembly is constructed with a molybdenum case for optimum heat transfer and offers +20 dBm output power at 1-dB compression. The amplitude balance between output ports is ±1 dB. The unit achieves 45-dB input-to-output isolation, with 20 dB isolation between output ports and is rated for operating temperatures from 0 to +71°C.
Of course, success in integration is usually based on solid design practices at the component level, and the company demonstrates this across a wide range of single-function components, including amplifiers, attenuators, detectors, and switches. The model CAMD9224 L-band high-power amplifier (HPA) is an example of a single-function component, with +62 dBm peak pulsed output power across the 1215-to-1400- MHz avionics band. It provides 12.5-dB typical gain across that range with typical amplitude flatness of ±0.6 dB and phase tracking of ±10 deg.
By leveraging the technology expertise in its individual components, Daico's engineers have developed higher-level integrated solutions for military applications including an APPL subassembly for airborne applications. Designed to boost exciter signals at input levels of +12 to +17 dBm in an avionics system, the subassembly must switch antenna connections between receiver and transmitter and also switch transmitter and receiver connections between one or more antennas. Designed for a housing measuring 9.260 x4.140 x1.70 in., the subassembly must also filter harmonics from transmitter signals, protect the transmitter from impedance mismatch damage, and protect the receiver from out-of-band interference signals. As a result, the highly integrated subassembly contains a number of different function blocks, including predriver, driver, and power amplifiers; a circulator to protect the power amplifier from antenna mismatches; an RF switch matrix which functions as an antenna interface; limiters to protect the receiver; low-noise amplifiers (LNAs) to improve receiver sensitivity; lowpass filters to suppress harmonic content; a high-performance power supply; and built-in-test (BIT), control, and monitoring circuitry.
Developed for use from 1350 to 1450 MHz, the subassembly is designed to operate with constant-envelope-modulation signals. The amplification, for example, must provide the fast rise/fall time needed to handle one symbol time (0.79 microseconds) without distortion.
In designing the integrated subassembly, which features upper and lower antenna ports for multiple-antenna connections, Daico's engineers were faced with a demanding set of requirements. For example, the VSWR at any RF interface could not exceed 1.30:1. In high-power mode, the output power from the lower antenna port into a 50- ohm load must be at least +51.2 dBm (132 W). In low-power mode, output power from the lower antenna port into a 50-ohm load must be at least +43.2 dBm (21.1 W) but not more than +46.3 dBm (42.2 W). The peak-to-peak gain flatness must be within 0.1 dB over any 1.7-MHz segment of the subassembly's instantaneous frequency range. The subassembly must provide at least 52 dB transmit- to-receive isolation, and must be unconditionally stable, with freedom of oscillation when presented with an infinite VSWR at any phase angle. It must also provide interference protection from Global Positioning System (GPS) signals in the neighboring bands of 1156 to 1196 MHz, 1208 to 1248 MHz, and 1555 to 1595 MHz requiring intelligent filtering capable of suppressing unwanted signals without adding undue weight and size to the subassembly.
In addition to meeting a host of military standard (MIL-STD) requirements for shock, vibration, and electromagnetic interference (EMI), the subassembly had target noise figure from any receiver input to any receiver output of 3.23 dB or less. The input third-order intercept point measured from each antenna port to each receiver port had to be at least +5 dBm while the output thirdorder intercept point measured at each receiver port had to be at least +16 dBm.
By specifying a small number of needed components, and relying on in-house engineering for the majority of the function blocks, the company succeeded in fitting the equivalent of about 25 separate components and function modules, such as the control and monitoring circuitry and a pulse-load power converter, into the required dimensions for the housing. In addition to its serial control interfaces, the unit features a diagnostic interface that helps in production and maintenance testing and troubleshooting.
Daico Industries, Inc.,
1070 E. 233rd St., Carson, CA 90745;
FAX: (310) 507-5701,