The advantages of a TAM that uses the L- through Ka-Band operational MiXiP SiP core is that the system is no longer hardware constrained. With the DAC, ADCs and FPGA MiXiP SiP’s ability to operate up to Ka-Band and with the system contained within a single SiP package, developers need only select from a vast array of auxiliary components to meet system performance requirements.
Once the auxiliary components are selected, the TAM becomes completely software-defined (dynamically software reconfigurable) with simultaneous sampling, handovers and seamless connectivity. Once the TAM hardware implementation is set, the only design variable in the system (besides software reconfigurations) is the sample clock frequency. The simultaneous sampling multi-band and multi-service operational capabilities of the TAM provide users with greater system-level resilience, independence of local/terrestrial/space EM infrastructures and automatic switching, which also enables other functions such as system monitoring, encryption operations and antenna blockage avoidance.3
Transmitter DAC
The EV12DD700 is a Ka-Band capable, radiation-tolerant, dual current-steering, 12-bit DAC with conversion rates up to 12 GSps. It can synthesize signals at frequencies over 21 GHz without up-conversion (see Figure 7). It embeds digital features like interpolation, digital up-conversion, direct digital synthesis, chirp, beamforming, beam hopping and ultra-fast frequency hopping.1,2,8
Figure 7 EV12DD700 (a) and amplitude versus output frequency (b).
The sinc(x) = sin(x)/x DAC output response can be compensated through the anti-sinc feature (A-SINC). In addition to the classical non-return-to-zero output mode (NRZ), the DAC cores have an embedded RF mode and a 2RF mode requiring a clock at twice the speed of other modes. These output modes enable the DAC to directly synthetize frequencies up to 21+ GHz without an external up-converter for operation up to and including Ka-Band.
Figure 8 shows the spectral output of the device when simultaneously transmitting L- and C-Bands (DAC Channel A (NRZ mode)) and X- and Ku-Bands (DAC Channel B (RF mode)) output signals.
Figure 8 EV12DD700 simultaneous output: L- and C-Bands (a), X- and Ku-Bands (b).
Figure 9 EV10AS940 performance and features.
Receiver ADC
The EV10AS940 is a 10-bit Ka-Band capable single channel ADC enabling sample rates up to 12.8 GSps. It also features digital down-conversion (DDC) and frequency hopping (FH) capabilities with multiple digital channels by integration of multiple numerically controlled oscillators. Other extensive digital features are included as well (see Figure 9).
Its high analog input bandwidth (35 GHz) makes it the best choice for direct RF Ka-Band architectures, eliminating any requirements to integrate dedicated mixers. Power consumption is as low as 2.5 W. It also features 11 ESIstream serial links that operate synchronously with the sampling clock to achieve deterministic data transfer.
DDC functionality has multiple options for decimation rates with up to four independent NCOs to support FH in multi-band operation. Coherent FH is possible due to multiple phase accumulators on each NCO and deterministic dedicated hopping trigger I/Os. Digital integer and fractional delays enable beamforming for use in phased array applications.
Other features include background and temperature calibration, temperature monitoring, DDC with decimation ratios from 2 to 1024, 4 DDC channels, dedicated FH I/Os, deterministic FH with return to zero, continuous and coherent modes, ESIstream 62/64b, high speed serial link (HSSL) reach selection and HSSL impedance control (2 × 50 Ω ± 20 percent).
Table 1 shows spurious free dynamic range (SFDR) and Table 2 shows noise power ratio (NPR), which are helpful in assessing the ADC’s multi-band/multi-tone performance capabilities.
Figure 10 Tx/Rx MiXiP SiP core for a TAM design.
Figure 10 shows the Tx/Rx MiXiP SiP core of the TAM which houses the EV12DD700, 2 EV10AS940s and the XQRVC1902. The complete MiXiP SiP transceiver has a compact form factor outline of 63 × 50 mm with a SiP ball matrix of 52 × 47 mm. The SiP (substrate patent pending) is pre-built using rad-tolerant DAC and ADCs with known reliability.
The ADCs also have single-ended inputs which are extremely helpful when selecting LNA drivers and eliminating the need for any transformer/balun requirements. Of course, the MiXiP positions the XQRVC1902 are next to the DAC and ADCs, thereby minimizing digital routing and reducing interference.
The AMD Xilinx VC1902 (7 nm) is a Versal-based AI core and adapt compute acceleration platform (ACAP) AI inference engine. Versal AI cores offer breakthrough AI inference that deliver over 100x greater performance than server-class CPUs.
The Versal ACAP is a comprehensive SoC that combines CPUs, DSPs, I/O and RAM control along with programmable hardware logic. The XQRVC1902 enables the Tx/Rx MiXiP SiP to have dynamic frequency planning and to be software controllable, flexible, multi-band, multi-service and able to crossband (receive multiple bands while simultaneously transmitting other bands).
TAM Auxiliary Components
To fully implement a software-defined direct RF simultaneous sampling multi-band/service transceiver operating from L- through Ka-Band, each system component is a key enabler. Besides using the Ka-Band capable Tx/Rx MiXiP, every other system component must be evaluated and understood from a simultaneous sampling multi-band performance perspective as well.6,7
For example, six simultaneous Tx/Rx RF bands/tones will be processed by the antennas, HPAs, LNAs, filters and circulators. Traditionally, these components are evaluated by varying single tones and/or two-tone tests. What is required now, however, is a multi-band performance evaluation mindset for each component.
This is where NPR testing might prove useful. NPR testing is typically thought of in terms of the “quietness” of a specific band within a multi-band system. Noise and intermodulation distortion products of other bands will fall into a specific band. Therefore, NPR testing may prove helpful in assessing auxiliary components’ multi-band/multi-tone performance capabilities. Some considerations for selecting TAM auxiliary components are:
Antennas and Operating Frequencies/Polarizations
If all Tx and Rx signals are in same plane, use linear polarized antennas; if not, use circular polarization. Wideband (circular polarized) antennas are generally provided by defense/satcom suppliers and a few commercial suppliers.
Wideband antenna design requires tradeoffs between antenna gain, antenna size, multi-beam capability, beamforming/shaping and steerability. Note that Ka-Band bandwidths are 4× larger than lower bands and therefore use multiple focused spot beams for frequency reuse operations that allow for Tx/Rx of different signals simultaneously at the same frequency.4
