System Integration

X-Band Development Platform Block Diagram

This section covers how the three main boards of the X-Band platform work together to create a complete hybrid beamforming phased array system.

System Architecture Overview

The X-Band Development Platform implements a hybrid beamforming architecture that combines:

  • Analog beamforming via ADAR1000EVAL1Z (32 channels)

  • Digital beamforming via AD9081-FMCA-EBZ (4 digital channels)

  • Frequency conversion via ADXUD1AEBZ (X-Band ↔ C-Band)

  • FPGA processing via ZCU102 (control and algorithms)

Signal Flow Architecture

Receive Path

Antenna → ADAR1000 → XUD1A → AD9081 → ZCU102
(32ch)     (32→4)    (X→C)    (4)     (Processing)

  1. 32 Antenna Elements collect RF signals at X-Band frequencies

  2. ADAR1000 Analog Beamforming combines 8 interleaved channels into 4 subarrays

  3. XUD1A Down Conversion translates X-Band RF to C-Band IF

  4. AD9081 Digitization converts 4 analog IF to digital channels

  5. ZCU102 Processing performs digital beamforming and signal processing

Transmit Path

ZCU102      → AD9081 → XUD1A → ADAR1000 → Antenna
(Processing)   (4)     (C→X)    (4→32)     (32ch)

  1. ZCU102 Processing generates digital waveforms

  2. AD9081 DACs convert digital signals to 4 analog IF channels

  3. XUD1A Up Conversion translates C-Band IF to X-Band RF

  4. ADAR1000 Power Division distributes 4 channels to 32 antenna elements

  5. 32 Antenna Elements radiate coherent X-Band signals

Subarray Architecture

Four 8:1 Subarrays

The system is organized into four subarrays with interleaved element assignments. Each subarray contains:

  • 2x ADAR1000 ICs (8 channels total per subarray)

  • 1x Power Splitter/Combiner (ZX10-2-183-S+)

  • 1x XUD1A Channel for frequency conversion

  • 1x AD9081 ADC/DAC pair for digitization

Physical Layout (antenna-facing view — ADAR1000 ICs on reverse side)

Stingray Subarray Physical Layout

Signal Path per Subarray

Subarray

Antenna Elements

ADAR1000 Devices

XUD1A Path (PMOD pin)

AD9081 DAC / ADC

1

1, 2, 5, 6, 9, 10, 13, 14

DEV 1, 3

J1D — TXRX4 (pin 8)

DAC3 / ADC3

2

3, 4, 7, 8, 11, 12, 15, 16

DEV 2, 4

J1C — TXRX3 (pin 6)

DAC2 / ADC1

3

19, 20, 23, 24, 27, 28, 31, 32

DEV 6, 8

J1B — TXRX2 (pin 4)

DAC1 / ADC0

4

17, 18, 21, 22, 25, 26, 29, 30

DEV 5, 7

J1A — TXRX1 (pin 2)

DAC0 / ADC2

Note

The XUD1A TX/RX direction is set via the PMOD connector’s voltage channels: voltage1 → Subarray 4, voltage2 → Subarray 3, voltage3 → Subarray 2, voltage4 → Subarray 1. A value of 1 selects TX (up-conversion), 0 selects RX (down-conversion).

Hybrid Beamforming Benefits

This architecture provides:

  • Analog beamforming: Fast, low-power steering within each subarray

  • Digital beamforming: Flexible, adaptive processing between subarrays

  • Reduced digital complexity: Only 4 digital channels vs 32

  • Maintained flexibility: Full beam control through combined analog/digital processing

Frequency Plan

X-Band RF Operation

  • Target Frequency: 10 GHz (center of X-Band)

  • RF Range: 8-12 GHz (X-Band)

  • Element Spacing: 15mm (optimized for 10 GHz)

IF Processing

  • IF Frequency: C-Band — recommended 4.5 GHz – 4.8 GHz between XUD1A and AD9081

  • LO Options: External or ADF4371 internal PLL

  • Default LO: Configurable based on application

  • IF Bandwidth: Determined by AD9081 settings

Digital Processing

  • ADC Sampling: Up to 4 GSPS per channel

  • DAC Sampling: Up to 12 GSPS per channel

  • Digital Channels: 8 RX, 8 TX (from 4 RF channels)

  • NCO Flexibility: Channel and main NCOs for fine frequency control

Control Architecture

IIO Devices

All system components are controlled through IIO (Industrial I/O) devices:

Device

IIO Name

Function

ADAR1000 #1-8

adar1000_csb_x_x

Analog beamforming control

ADF4371

adf4371-0

LO generation (if used)

AD9081 RX

axi-ad9081-rx-hpc

Digital receive processing

AD9081 TX

axi-ad9081-tx-hpc

Digital transmit processing

XUD1A

xud_control

X-Band up/down converter control

TDD Core

axi-core-tdd

Time division duplexing

Interconnect Requirements

Digital Connections

  • AD9081 ↔ ZCU102: FMC HPC0 connection with riser

  • Interposer ↔ ZCU102: FMC HPC1 connection with cable extension

  • Stingray ↔ ZCU102: Dual PMOD connections with adapters

RF Connections

  • 8x SMA-SMPM cables: AD9081 ↔ XUD1A

  • 4x Power splitters: XUD1A → splits each channel to 2 input/outputs

  • 8x SMA-SMPM cables: Power splitters ↔ Stingray ADAR1000s

  • 32x SMPM bullets: Stingray ADTR1107s ↔ Antenna tiles

Optional Inline Filters (recommended for improved spectral purity)

Filter

Path

Qty

Mini-Circuits VLF-8400+

AD9081 ADC ↔ XUD1A (RX)

4

Mini-Circuits VLF-5500+

AD9081 DAC ↔ XUD1A (TX)

4

Power Distribution

  • ZCU102: 12V supply powers AD9081 via FMC

  • XUD1A: Dedicated 12V supply (~15W)

  • Stingray: Dedicated 12V supply (~30W)

Timing and Synchronization

Clock Distribution

  • Master Clock: 100 MHz reference (external or internal)

  • HMC7044: Clock distribution and jitter attenuation

  • AD9081: On-chip PLLs for ADC/DAC clocks

  • Phase Coherence: Maintained across all channels

TDD Coordination

  • TDD Engine: FPGA-based timing control

  • Global Sync: Coordinates all three boards

  • ADC/DAC Sync: Synchronized sampling and generation across all channels

Calibration Strategy

System-Level Calibration

  1. Individual Channel Cal: Per-ADAR1000 channel calibration

  2. Subarray Cal: Per-subarray amplitude/phase matching

  3. Digital Cal: AD9081 channel matching

  4. End-to-End Cal: Full system calibration via known signals

Calibration Tools

  • Built-in Detectors: ADAR1000 power detection

  • Digital Loopback: AD9081 internal test modes

  • External Signals: Controlled calibration sources

  • Over-the-Air: Pattern measurement and correction

Note

The hybrid architecture provides both the flexibility of digital beamforming and the efficiency of analog beamforming, making it ideal for radar, EW, and SATCOM applications requiring both performance and power efficiency.