Interface Guide: STM-Rb Series Rubidium Clocks

Overview

The BRIDZA STM-Rb series represents a comprehensive lineup of high-performance rubidium frequency standards, including the ultra-high performance STM-Rb-H, standard STM-Rb-N, vibration-resistant STM-Rb-Z, ultra-thin STM-Rb-S, and miniature STM-Rb-M models. These instruments deliver exceptional frequency stability and phase noise performance essential for precision timing applications in telecommunications, navigation, metrology, and defense systems.

Supported Models

Connector Locations

 ┌─────────────────────────────────────────────────────────────┐
 │ FRONT PANEL │
 │ │
 │ [SMA] 10MHz OUT [SMA] 1PPS OUT [SMA] 1PPS IN │
 │ │
 │ ┌──────┐ ┌──────┐ ┌──────┐ ┌──────┐ ┌──────┐ │
 │ │ PWR │ │ LOCK │ │ ALM │ │ COM │ │ GND │ │
 │ │ LED │ │ LED │ │ LED │ │ LED │ │ LED │ │
 │ └──────┘ └──────┘ └──────┘ └──────┘ └──────┘ │
 │ │
 │ DC IN: +12V/+24V COM: RS232/RS485 (DB9) │
 │ │
 └─────────────────────────────────────────────────────────────┘

Interface Definitions

1. 10MHz Reference Output

Pin Assignment (SMA Connector):

 ┌─────────┐
 │ ○ │ Center pin: Signal
 │ │ Outer shell: Ground
 └─────────┘

2. 1PPS Pulse Output

Timing Diagram:

 High
 │ ┌─────────┐
 │ │ 5ms │
 │ │ │
 └────────┘ └────
 Low ↑
 Rising edge aligned to UTC second

3. External 1PPS Input (N/Z/S Series)

4. Serial Monitor Interface

DB9 Pin Assignment (RS232):

5. SCPI Command Set

Common Commands:

*IDN? ; Read instrument identification
*rst ; Reset to factory defaults
*cls ; Clear status registers
:syst:err? ; Query system errors
:freq? ; Query output frequency
:power? ; Query output power level
:power  ; Set output power (dBm)
:outp:stat <0|1> ; Enable/disable output
:outp:stat? ; Query output status
:sens:temp? ; Query internal temperature
:sens:volt? ; Query supply voltage
:cal:date? ; Query last calibration date

1PPS Commands:

:puls:fwid? ; Query pulse width
:puls:fwid  ; Set pulse width (ms)
:puls:pol? ; Query polarity
:puls:pol  ; Set negative/positive polarity

Disciplining Commands:

:sync:mode  ; Set sync mode (INT/EXT/GNSS)
:sync:stat? ; Query synchronization status
:sync:off? ; Query offset from reference
:sync:pha? ; Query 1PPS phase error

Power Supply

DC Input Connector

Pin Assignment (Terminal Block):

 ┌─────────────────────┐
 │ + - ⏚ │
 │ │ │ │ │
 │ 12V GND Chassis │
 └─────────────────────┘

Power Specifications by Model

Mechanical Dimensions

STM-Rb-H (Desktop/Rack Mount)

 232mm
 ┌────────────────────────────────┐
 │ │ 162mm
 │ ┌──────────────────────┐ │
 │ │ │ │
 │ │ STM-Rb-H │ │
 │ │ RUBIDIUM CLOCK │ │
 │ │ │ │
 │ └──────────────────────┘ │
 │ │
 └────────────────────────────────┘
 └── 160mm ──┘
 
 Mounting Holes: 4× M3 threads, 8mm deep

STM-Rb-N (Compact Module)

 127mm
 ┌────────────────────────────┐
 │ ┌──────────────────┐ │ 92.5mm
 │ │ │ │
 │ │ STM-Rb-N │ │
 │ │ 10MHz 1PPS │ │
 │ │ │ │
 │ └──────────────────┘ │
 │ └──39.6mm──┘ │
 └────────────────────────────┘

Typical Connection Diagram

 ┌──────────────────────────────────────────────────────────────┐
 │ SYSTEM CONNECTION │
 │ │
 │ GNSS Antenna │
 │ │ │
 │ ▼ │
 │ ┌─────────┐ 10MHz ┌─────────────┐ │
 │ │ GNSS │──────────────│ │ │
 │ │ DO │ │ STM-Rb-N │──────┬──────┐ │
 │ │ │─────1PPS─────│ │ │ │ │
 │ └─────────┘ │ │ 10MHz 1PPS │
 │ │ │ OUT OUT │
 │ └─────────────┘ │ │ │
 │ ▼ ▼ │
 │ ┌─────────┐ ┌───────┐ │
 │ │ Freq. │ │ Data │ │
 │ │ Counter │ │Acquis.│ │
 │ └─────────┘ └───────┘ │
 │ │
 │ PC/Server │
 │ │ │
 │ ▼ │
 │ ┌─────────────────────────────────────────────┐ │
 │ │ RS232/RS485 COM Port │ USB Adapter │ │
 │ └─────────────────────────────────────────────┘ │
 │ │
 └───────────────────────────────────────────────────────────────┘

PCB Layout Guidelines

RF Signal Routing

• 50Ω Transmission Lines: Use controlled impedance traces (Microstrip Line)
• Trace Width: 2.8mm for FR4, 3.2mm for Rogers materials (50Ω)
• Ground Plane: Solid ground plane beneath RF traces
• Via Stitching: Ground vias every λ/10 (20mm @ 10MHz)
• Connector Placement: Place SMA connectors at PCB edge

Power Distribution

• Decoupling: 100nF + 10μF caps near each IC
• Star Ground: Single point ground for analog circuits
• Trace Width: 2mm minimum for 1A current paths

EMC Considerations

• Shielding: Full metal enclosure for H/N series
• Filter: Input power filtered with EMI suppressors
• Isolation: Optical isolation for serial communication

Configuration Examples

Serial Port Setup (Python)

import serial

# Open serial connection
ser = serial.Serial(
 port='/dev/ttyUSB0',
 baudrate=9600,
 bytesize=serial.EIGHTBITS,
 parity=serial.PARITY_NONE,
 stopbits=serial.STOPBITS_ONE,
 timeout=1
)

# Read identification
ser.write(b'*IDN?\n')
response = ser.readline().decode().strip()
print(f"Instrument: {response}")

# Query frequency
ser.write(b':FREQ?\n')
freq = ser.readline().decode().strip()
print(f"Frequency: {freq} Hz")

# Enable output
ser.write(b':OUTP:STAT 1\n')

# Close connection
ser.close()

SCPI Command Sequence

; Initialize rubidium clock
*RST ; Reset to defaults
*CLS ; Clear status

; Configure for GNSS disciplining
:SYNC:MODE EXT ; Enable external 1PPS input
:FREQ 10000000 ; Set 10MHz output

; Enable outputs
:OUTP:STAT 1 ; Enable RF output
:PULS:STAT 1 ; Enable 1PPS output

; Query status
:SYNC:STAT? ; Should return "LOCKED"
:TEMP? ; Internal temperature

Troubleshooting

Download Resources

• STM-Rb-N Datasheet
• STM-Rb-H Datasheet
• STM-Rb-Z Datasheet
• STM-Rb-S Datasheet
• STM-Rb-M Datasheet
• 3D Models (STEP)

Document Version: 1.0

Last Updated: 2026-05-24

BRIDZA Technologies