Browse Prior Art Database

Load Insensitive Wide Dynamic Range RF Power Detector

IP.com Disclosure Number: IPCOM000174162D
Publication Date: 2008-Aug-29
Document File: 2 page(s) / 38K

Publishing Venue

The IP.com Prior Art Database

Abstract

This paper describes a RF power detector circuit that has a wide dynamic range and is load insensitive. In this circuit, the output DC voltage changes monotonically with the RF power level. This circuit can be used in many applications, particularly used together with a RF power amplifier.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 54% of the total text.

Page 1 of 2

Load Insensitive Wide Dynamic Range RF Power Detector

Wei Yi Thor, Avago Technologies (Malaysia) Sdn Bhd, Penang, Malaysia

Abstract

This paper describes a RF power detector circuit that has a wide dynamic range and is load insensitive. In this circuit, the output DC voltage changes monotonically with the RF power level. This circuit can be used in many applications, particularly used together with a RF power amplifier.

Introduction

In many applications today, particularly in applications requiring a power amplifier, a form of indicator is required to track the power at the output of the power amplifier. Often, this indicator comes in the form of a DC voltage that is either proportional to or is a function of the output power.

Background

Fig. 1: Diode Rectifier

Detector Circuit

Vin

C2

X

D

3

D1

Vd

R1

d

R2

Vo

C

1

D

2

ut

C3

Vin Vo

   Fig. 3: RF Power Detector Circuit (Detector A)

Fig. 3 shows the first of the circuits presented in this paper. This circuit combines the circuit in [1] and Fig. 2. The advantage of this circuit is that the output voltage can be up to twice the value the input voltage (voltage doubler), and is able to work with a wide dynamic range of the input power.

D2 adds a DC voltage to turn-on D1 and D3. R2 provides a DC path to ground. R1 acts as a current limiter, and together with C1, acts as a low pass filter.

RFin

ut

C

1

D

2

C2

Vdd

R4

X

Vin Vo

D1

C2

D3

ut

D1

R3

C3

Vdd

R1

Q1

Vout

R2

D2

C1

Fig. 2: Voltage Doubler

Fig. 1 and 2 shows a basic form of voltage detector circuits. In both circuits, the output voltage, Vo, is a function of the input voltage, Vin. The benefit of the circuit in Figure 2 is that Vo is double the value of the amplitude of Vin. However, the major disadvantage of both circuits is that a turn-on voltage (typically around
0.3-1.0V) is required to turn on the diodes, and hence these circuits does not work where Vin values are very small i.e. low RF power levels.

D4

D5

Fig. 4: Improved RF Power Detector Circuit (Detector B)

Fig. 4 s...