600S0R4AW250XT
American Technical Ceramics
The ATC 600S0R4AW250XT is a 0.4pF capacitor with ±0.05pF tolerance.
Application NoteAnalog
AN91: Low Cost Coupling Methods for RF Power Detectors Replace Directional Couplers
Application note detailing cost-effective capacitive coupling alternatives to directional couplers for RF power control in GSM, DCS, and PCS wireless applications.
Overview
This design document outlines low-cost coupling methods for RF power detectors and controllers, providing a discrete alternative to traditional directional couplers in wireless transmit channels. It introduces a capacitive coupling scheme using a 0.4pF capacitor and 50Ω resistor to interface with Linear Technology RF power controllers like the LTC4401-1 and LTC5505-2 power detector. Two methods are described: a basic capacitive tap and a method incorporating a shunt inductor to compensate for parasitic capacitance and improve sensitivity. The document includes performance comparisons against standard directional couplers, theory of operation, and layout considerations for GSM, DCS, and PCS band frequencies.
Use Cases
- Cellular telephone RF transmit power control
- Replacing directional couplers to reduce BOM cost and board area
- RF feedback network optimization for GSM/DCS/PCS bands
- Wireless transmitter power monitoring
Referenced Parts
06033C102KAT1A
AVX Corporation
1000pF 25V 10% X7R Capacitor
06035A101JAT1A
AVX Corporation
100pF 50V 5% NPO Capacitor
06035A150JAT1A
AVX Corporation
15pF 50V 5% NPO Capacitor
06035A330JAT1A
AVX Corporation
The 33pF capacitor is an AVX 06035A330JAT1A, comes in a 0603 package and has 5% tolerance.
06035A331JAT1A
AVX Corporation
330pF 50V 5% NPO Capacitor
0603YC104MAT1A
AVX Corporation
0.1μF 16V 20% X7R Capacitor
CR16-49R9FM
American Alumina Corp
The series resistor is 49.9Ω (AAC CR16-49R9FM) with 1% tolerance.
PF08123B
Hitachi
Each of these demo boards contains an LTC4401-1 power controller and a Hitachi PF08123B triple-band power amplifier.
LTC4401-1
Linear Technology
Each of these demo boards contains an LTC4401-1 power controller and a Hitachi PF08123B triple-band power amplifier.
LFDP21920MDP1A048
Murata Manufacturing
LFDP21920MDP1A048 Dual Wideband Diplexer SMT IC
LQP15MN4N7B00
Murata Manufacturing
The Murata film type inductor, LQP15MN4N7B00D, comes in a 0402 package and has ±1nH tolerance.
PF08107B
Hitachi
This method has been tested with the LTC4401-1 and the following Hitachi power amplifiers: PF08107B, PF08122B, PF08123B.
PF08122B
Hitachi
This method has been tested with the LTC4401-1 and the following Hitachi power amplifiers: PF08107B, PF08122B, PF08123B.
LTC5505-2
Linear Technology
Using a shunt inductor improves the sensitivity of the LTC5505-2 by a factor of 2dB to 4dB.
LDC21897M190-078
Murata Manufacturing
The directional coupler commonly used (Murata LDC21897M190-078) is unidirectional (forward) and dual band.
LFDP20N0020A
Murata Manufacturing
U3 LFDP20N0020A
LTC1757A
Linear Technology
This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403)
LTC1758
Linear Technology
This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403)
LTC1957
Linear Technology
This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403)
LTC4400
Linear Technology
This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403)
LTC4401
Linear Technology
This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403)
LTC4402
Linear Technology
This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403)
LTC4403
Linear Technology
This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403)
LDC21897M190-078
Murata
Murata LDC21897M190-078 directional coupler is housed
| 600S0R4AW250XT | American Technical Ceramics | The ATC 600S0R4AW250XT is a 0.4pF capacitor with ±0.05pF tolerance. |
| EMK212BJ105MG-T | Taiyo Yuden | 1μF 16V 20% X5R Capacitor |
| 06033C102KAT1A | AVX Corporation | 1000pF 25V 10% X7R Capacitor |
| 06035A101JAT1A | AVX Corporation | 100pF 50V 5% NPO Capacitor |
| 06035A150JAT1A | AVX Corporation | 15pF 50V 5% NPO Capacitor |
| 06035A330JAT1A | AVX Corporation | The 33pF capacitor is an AVX 06035A330JAT1A, comes in a 0603 package and has 5% tolerance. |
| 06035A331JAT1A | AVX Corporation | 330pF 50V 5% NPO Capacitor |
| 0603YC104MAT1A | AVX Corporation | 0.1μF 16V 20% X7R Capacitor |
| CR16-49R9FM | American Alumina Corp | The series resistor is 49.9Ω (AAC CR16-49R9FM) with 1% tolerance. |
| PF08123B | Hitachi | Each of these demo boards contains an LTC4401-1 power controller and a Hitachi PF08123B triple-band power amplifier. |
| LTC4401-1 | Linear Technology | Each of these demo boards contains an LTC4401-1 power controller and a Hitachi PF08123B triple-band power amplifier. |
| LFDP21920MDP1A048 | Murata Manufacturing | LFDP21920MDP1A048 Dual Wideband Diplexer SMT IC |
| LQP15MN4N7B00 | Murata Manufacturing | The Murata film type inductor, LQP15MN4N7B00D, comes in a 0402 package and has ±1nH tolerance. |
| PF08107B | Hitachi | This method has been tested with the LTC4401-1 and the following Hitachi power amplifiers: PF08107B, PF08122B, PF08123B. |
| PF08122B | Hitachi | This method has been tested with the LTC4401-1 and the following Hitachi power amplifiers: PF08107B, PF08122B, PF08123B. |
| LTC5505-2 | Linear Technology | Using a shunt inductor improves the sensitivity of the LTC5505-2 by a factor of 2dB to 4dB. |
| LDC21897M190-078 | Murata Manufacturing | The directional coupler commonly used (Murata LDC21897M190-078) is unidirectional (forward) and dual band. |
| LFDP20N0020A | Murata Manufacturing | U3 LFDP20N0020A |
| LTC1757A | Linear Technology | This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403) |
| LTC1758 | Linear Technology | This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403) |
| LTC1957 | Linear Technology | This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403) |
| LTC4400 | Linear Technology | This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403) |
| LTC4401 | Linear Technology | This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403) |
| LTC4402 | Linear Technology | This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403) |
| LTC4403 | Linear Technology | This scheme can be applied to all LTC power controllers (LTC1757A, LTC1758, LTC1957, LTC4400, LTC4401, LTC4402 and LTC4403) |
| LDC21897M190-078 | Murata | Murata LDC21897M190-078 directional coupler is housed |