Difference between revisions of "RF Attenuators"

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== Purchased Attenuators ==
 
== Purchased Attenuators ==
 +
 +
=== Programmable Attenuator ===
  
 
* [[PE4302 RF Attenuator|PE4302 RF Attenuator board in my enclosure design]]
 
* [[PE4302 RF Attenuator|PE4302 RF Attenuator board in my enclosure design]]
Line 5: Line 7:
 
[[file:PE4302_P1833-720px.jpg]]
 
[[file:PE4302_P1833-720px.jpg]]
  
−
== Homebrew RF Attenuators ==
+
=== Triple Attenuator ===
  
−
[[file:Atten_30dB_20dV_P1812-720px.jpg]]
+
* [[0/10/20/30 dB Attenuator]]
−
=== 30 dB Attenuator ===
 
  
−
* [http://leleivre.com/rf_pipad.html Pi Attenuator Calculator]
+
[[file:ATTEN4_CHINA_PCB.PNG]]
  
−
[[file:Atten30dB_P116-720px.jpg]]
+
== Homebrew RF Attenuators ==
  
−
[[file:30dB_Attenuator.PNG]]
+
[[file:Atten_30dB_20dV_P1812-720px.jpg]]
  
−
* Built
+
[[Homebrew RF Attenuators]]
−
** Standard 5% resistor values
 
−
** R1 = 820 in parallel with 22K = 790.6 ohms
 
−
** R2 = 2 paralleled 120 Ohm 1/4W resistors paralleled with 470 ohms = 53.2 ohms
 
−
** Flat from 0-30 MHz
 
−
** Measured attenuation is flat
 
−
*** -30.01dB at 1 MHz
 
−
*** -30.24dB at 30 MHz
 
−
** Input Impedance - 53.1 ohms, 21.3nF
 
−
** SWR 1.06
 
−
** 1/2W max (5VDC max, 0 ohm source)
 
  
−
* NanoVNA scan data
+
== Attenuator Design - Rev 2 ==
  
−
[[file:30dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
+
[[FILE:ATTEN1_P1896-720PX.jpg]]
  
−
[[file:30dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
+
* 6 dB resistor values in above
 +
* [https://oshpark.com OshPark] clear soldermask "After Dark"
 +
** $4.40 for 6 cards
 +
* Small/light enough to hang directly off fragile devices
 +
* SMA connectors
 +
** Male/female are good choices for direct connect to devices
 +
* Resistors
 +
** 1206
 +
*** 1/4W
 +
*** 1% values get good accuracy (approx. 2%) even though not exact to calculated values
 +
* Good bandwidth up well past RF
  
−
* LTSPICE Simulation
+
[[file:10dB_Attenuator.PNG]]
  
−
[[file:LTSPice_30dB.PNG]]
+
=== Parts ===
  
−
=== 20 dB Attenuator ===
+
{| class="wikitable"
 +
! Mfr. #
 +
! Manufacturer
 +
! Customer #
 +
! Qty
 +
! R1/R2
 +
! Description
 +
|-
 +
| RK73H2BTTE17R8F
 +
| KOA Speer
 +
| ATTEN_03DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 1/4W 17.8 ohms 1%
 +
|-
 +
| RC1206FR-07294RL
 +
| YAGEO
 +
| ATTEN_03DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 294 ohms 1/4W 1206 1%
 +
|-
 +
| RK73H2BTTD37R4F
 +
| KOA Speer
 +
| ATTEN_06DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 1/4W 37.4 ohms 1%
 +
|-
 +
| CRCW1206150RFKEAC
 +
| Vishay
 +
| ATTEN_06DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 1/4Watt 150 ohms 1%
 +
|-
 +
| RC1206FR-0771R5L
 +
| YAGEO
 +
| ATTEN_10DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 71.5 ohms 1/4W 1206 1%
 +
|-
 +
| RC1206FR-0797R6L
 +
| YAGEO
 +
| ATTEN_10DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 97.6 ohms 1/4W 1206 1%
 +
|-
 +
| RK73H2BTTD1070F
 +
| KOA Speer
 +
| ATTEN_13DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 1/4W 107 ohms 1%
 +
|-
 +
| RC1206FR-0778R7L
 +
| YAGEO
 +
| ATTEN_13DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 78.7 ohms 1/4W 1206 1%
 +
|-
 +
| AC1206FR-07249RL
 +
| YAGEO
 +
| ATTEN_20DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 249 ohms 1/4W 1206 1%
 +
|-
 +
| RK73H2BTTDD61R9F
 +
| KOA Speer
 +
| ATTEN_20DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 61.9 ohms 1%
 +
|-
 +
| RK73H2BTTD7870F
 +
| KOA Speer
 +
| ATTEN_30DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 1/4W 787 ohms 1%
 +
|-
 +
| AC1206FR-0753R6L
 +
| YAGEO
 +
| ATTEN_30DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 53.6 ohms 1/4W 1206 1%
 +
|-
 +
| RC1206FR-072K49L
 +
| YAGEO
 +
| ATTEN_40DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 2.49k ohms 1/4W 1206 1%
 +
|-
 +
| RK73H2BTTD51R0F
 +
| KOA Speer
 +
| ATTEN_40DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 1/4W 51 ohms 1%
 +
|-
 +
| RK73H2BTTDD49R9F
 +
| KOA Speer
 +
| ATTEN_50_60DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 49.9 ohms 1%
 +
|-
 +
| RC1206FR-077K87L
 +
| YAGEO
 +
| ATTEN_50DB
 +
| 1
 +
| R1
 +
| Resistors - SMD 7.87k ohms 1/4W 1206 1%
 +
|-
 +
| RC1206FR-0726K1L
 +
| YAGEO
 +
| ATTEN_60DB
 +
| 2
 +
| R2
 +
| Resistors - SMD 26.1k ohms 1/4W 1206 1%
 +
|-
 +
|}
  
−
[[file:Atten_20dB_P115-720px.jpg]]
+
=== Measurements ===
  
−
[[file:20dB_Attenuator.PNG]]
+
* NanoVNA
 +
* S21 gain
 +
* 1-900 MHz scan
 +
* Calibrated with cable on thru
  
−
* Build
+
==== 6 dB Attenuator ====
−
** Standard 5% resistor values
 
−
** R1 = 2 of 510 in parallel also in parallel with 8.2K = 247.3 ohms
 
−
** R2 = 2 paralleled 150 Ohm 1/2W resistors paralleled with 330 ohms = 61.11 ohms
 
−
** Flat from 0-30 MHz
 
−
** Measured attenuation is flat
 
−
** Input Impedance - tbd ohms, tbd nF
 
−
** SWR tbd
 
−
** 1W max (8.6 V max, 0 ohm source)
 
  
−
[[file:20dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
+
* Flat from 1-600 MHz
−
 
+
* Higher attenuation past 600 MHz
−
[[file:20dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
+
* S21
−
 
 
−
* LTSPICE Simulation
 
−
 
 
−
[[file:LTSPice_20dB.PNG]]
 
−
 
 
−
=== 10 dB Attenuator ===
 
−
 
 
−
[[file:Atten_10dB_P115-720px.jpg]]
 
−
 
 
−
[[file:10dB_Attenuator.PNG]]
 
  
−
* Build
+
[[file:ATTEN1_NanoVNA_6dB_S21_1-900MHz.png]]
−
** Standard 5% resistor values
 
−
** R1 = 2 of 150 in parallel also in parallel with 1.5K = 71.43 ohms (0.3% error)
 
−
** R2 = 3 of 330 Ohm 1/4W parallel resistors paralleled with 810 ohms = 96.85 ohms (0.62% error)
 
−
** Flat from 0-30 MHz
 
−
** Measured attenuation is flat
 
−
** Input Impedance - tbd ohms, tbd nF
 
−
** SWR tbd
 
−
** 3/4W max (9.1 V max, 0 ohm source)
 
  
−
[[file:10dB_Attenuator_NanoVNA_Setup_Curve_900MHz.PNG]]
+
* S11 from 1-900 MHz
  
−
[[file:10dB_Attenuator_NanoVNA_Data_900MHz.PNG]]
+
[[file:ATTEN1_NanoVNA_6dB_S11_1-900MHz.png]]
  
−
* LTSPICE Simulation
+
==== 40 dB Attenuator ====
  
−
[[file:LTSPice_10dB.PNG]]
+
* Flat from 1-600 MHz
 +
* Higher attenuation past 600 MHz
 +
* -39.9 dB at 14 MHz
 +
* S21
  
−
=== Attenuator Construction ===
+
[[file:ATTEN1_NanoVNA_40dB.png]]
  
−
* Single side copper clad PCB
+
* Flat from 1-30 MHz
−
** Approx 2"x1"
+
* S21
−
* Clean with steel wool
 
−
* Solder SMA connectors
 
−
** Use large alligator clips to hold while soldering
 
−
** Solder on sides only
 
  
−
[[file:Atten_01_SMAs_720px.jpg]]
+
[[file:ATTEN1_NanoVNA_40dB_1-30MHz.png]]
  
−
* Cut "T" Shaped pads
+
* s11
−
** I used nibbler
+
* 1-900 MHz
−
* Center fits between connector ground pins
 
−
* Glue down pads with Superglue
 
  
−
[[file:Atten_02_Pads_720px.jpg]]
+
[[file:ATTEN1_NanoVNA_40dB_S11_1-100MHz.png]]
  
−
* Solder center pin with big solder blob
+
* VSWR
−
** A bit too high for direct contact
+
* 1-900 MHz
−
* Verify raised pad does not short to ground
 
  
−
[[file:Atten_03_Solder CenterPads_720px.jpg]]
+
[[file:ATTEN1_NanoVNA_40dB_VSWR_1-100MHz.png]]
  
−
* Solder side resistor(s)
+
=== DC Block ===
−
* Leave room for center resistor(s)
 
  
−
[[file:Atten_04_Solder Side_Resistors_720px.jpg]]
+
* Use same PCB
 +
** Install 0.1uF cap between the two SMAs
 +
** Leave off resistors to ground
 +
* Sweep 50 KHz to 900 MHz
 +
* S21 of -0.8 dB at 50 KHz
 +
* S21 of 0.44 dB at 900 MHz
  
−
* Measure side resistors from pad to ground
+
[[FILE:ATTEN1_NanoVNA_DC-BLOCK_S21_50KHz-900MHz.png]]
−
* Should match value
 
−
* Solder center resistor(s)
 
  
−
[[file:Atten_05_Solder Center_Resistors_720px.jpg]]
+
* Sweep 50 KHz to 900 MHz
 +
*S11
  
−
* Verify no shorts between centers and ground
+
[[FILE:ATTEN1_NanoVNA_DC-BLOCK_S11_50KHz-900MHz.png]]
  
 
== Attenuator Charts ==
 
== Attenuator Charts ==

Latest revision as of 12:08, 25 November 2021

Purchased Attenuators

Programmable Attenuator

PE4302 P1833-720px.jpg

Triple Attenuator

ATTEN4 CHINA PCB.PNG

Homebrew RF Attenuators

Atten 30dB 20dV P1812-720px.jpg

Homebrew RF Attenuators

Attenuator Design - Rev 2

ATTEN1 P1896-720PX.jpg

  • 6 dB resistor values in above
  • OshPark clear soldermask "After Dark"
    • $4.40 for 6 cards
  • Small/light enough to hang directly off fragile devices
  • SMA connectors
    • Male/female are good choices for direct connect to devices
  • Resistors
    • 1206
      • 1/4W
      • 1% values get good accuracy (approx. 2%) even though not exact to calculated values
  • Good bandwidth up well past RF

10dB Attenuator.PNG

Parts

Mfr. # Manufacturer Customer # Qty R1/R2 Description
RK73H2BTTE17R8F KOA Speer ATTEN_03DB 1 R1 Resistors - SMD 1/4W 17.8 ohms 1%
RC1206FR-07294RL YAGEO ATTEN_03DB 2 R2 Resistors - SMD 294 ohms 1/4W 1206 1%
RK73H2BTTD37R4F KOA Speer ATTEN_06DB 1 R1 Resistors - SMD 1/4W 37.4 ohms 1%
CRCW1206150RFKEAC Vishay ATTEN_06DB 2 R2 Resistors - SMD 1/4Watt 150 ohms 1%
RC1206FR-0771R5L YAGEO ATTEN_10DB 1 R1 Resistors - SMD 71.5 ohms 1/4W 1206 1%
RC1206FR-0797R6L YAGEO ATTEN_10DB 2 R2 Resistors - SMD 97.6 ohms 1/4W 1206 1%
RK73H2BTTD1070F KOA Speer ATTEN_13DB 1 R1 Resistors - SMD 1/4W 107 ohms 1%
RC1206FR-0778R7L YAGEO ATTEN_13DB 2 R2 Resistors - SMD 78.7 ohms 1/4W 1206 1%
AC1206FR-07249RL YAGEO ATTEN_20DB 1 R1 Resistors - SMD 249 ohms 1/4W 1206 1%
RK73H2BTTDD61R9F KOA Speer ATTEN_20DB 2 R2 Resistors - SMD 61.9 ohms 1%
RK73H2BTTD7870F KOA Speer ATTEN_30DB 1 R1 Resistors - SMD 1/4W 787 ohms 1%
AC1206FR-0753R6L YAGEO ATTEN_30DB 2 R2 Resistors - SMD 53.6 ohms 1/4W 1206 1%
RC1206FR-072K49L YAGEO ATTEN_40DB 1 R1 Resistors - SMD 2.49k ohms 1/4W 1206 1%
RK73H2BTTD51R0F KOA Speer ATTEN_40DB 2 R2 Resistors - SMD 1/4W 51 ohms 1%
RK73H2BTTDD49R9F KOA Speer ATTEN_50_60DB 2 R2 Resistors - SMD 49.9 ohms 1%
RC1206FR-077K87L YAGEO ATTEN_50DB 1 R1 Resistors - SMD 7.87k ohms 1/4W 1206 1%
RC1206FR-0726K1L YAGEO ATTEN_60DB 2 R2 Resistors - SMD 26.1k ohms 1/4W 1206 1%

Measurements

  • NanoVNA
  • S21 gain
  • 1-900 MHz scan
  • Calibrated with cable on thru

6 dB Attenuator

  • Flat from 1-600 MHz
  • Higher attenuation past 600 MHz
  • S21

ATTEN1 NanoVNA 6dB S21 1-900MHz.png

  • S11 from 1-900 MHz

ATTEN1 NanoVNA 6dB S11 1-900MHz.png

40 dB Attenuator

  • Flat from 1-600 MHz
  • Higher attenuation past 600 MHz
  • -39.9 dB at 14 MHz
  • S21

ATTEN1 NanoVNA 40dB.png

  • Flat from 1-30 MHz
  • S21

ATTEN1 NanoVNA 40dB 1-30MHz.png

  • s11
  • 1-900 MHz

ATTEN1 NanoVNA 40dB S11 1-100MHz.png

  • VSWR
  • 1-900 MHz

ATTEN1 NanoVNA 40dB VSWR 1-100MHz.png

DC Block

  • Use same PCB
    • Install 0.1uF cap between the two SMAs
    • Leave off resistors to ground
  • Sweep 50 KHz to 900 MHz
  • S21 of -0.8 dB at 50 KHz
  • S21 of 0.44 dB at 900 MHz

ATTEN1 NanoVNA DC-BLOCK S21 50KHz-900MHz.png

  • Sweep 50 KHz to 900 MHz
  • S11

ATTEN1 NanoVNA DC-BLOCK S11 50KHz-900MHz.png

Attenuator Charts

DBm vs milliVolt milliWatts.PNG

DBm vs Volta Watts.PNG

DBm vs Volt Watts.PNG

References

  • Heavily inspired by Alan (W2AEW) video

W2AEW Attns-01.PNG

W2AEW Attns-02.PNG

W2AEW Attns-03.PNG

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