Analog Baseband Filter with Source Follower for LO Leakage Control

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Solution Overview

Problem

Existing Radio Frequency Integrated Circuits (RFICs) face challenges in reducing current consumption and size while maintaining performance, especially in communication systems using 16QAM or 64QAM, due to issues like temperature-dependent resistor properties causing common mode voltage variations and Local Oscillator (LO) leakage.

Innovation Solution

Integration of a current-voltage conversion amplifier with a resistor array and a source follower circuit to adjust gain and compensate for temperature variations, reducing physical size and current consumption, and preventing LO leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If an integrated circuit of I-V converter and PGA is used, then current consumption and size are reduced, but temperature-dependent resistor properties cause common mode voltage variations and LO leakage

Engineering Contradiction:

Improvecircuit areaVSAvoidcommon mode voltage stability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

A source follower circuit is introduced as an intermediary between the PGA and the RF front-end. This source follower acts as a buffer that isolates the PGA's resistor array from the sensitive RF circuitry, preventing temperature-induced resistor variations from causing LO leakage while maintaining the integration benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The integrated circuit is segmented into distinct functional blocks: I-V converter, PGA with resistor array, and source follower circuit. This segmentation allows each component to be optimized independently - the resistor array for gain control and the source follower for temperature compensation - while remaining on a single chip.

Inventive Principle:

Principle #1Segmentation

2Use of energy by moving object

If an integrated circuit of I-V converter and PGA is used, then current consumption and size are reduced, but LO leakage occurs due to temperature changes

Engineering Contradiction:

Improvecurrent consumptionVSAvoidLO leakage

Core Design Contradiction:

Use of energy by moving objectVSObject-generated harmful factors

Solution Approach 1:

The source follower circuit serves as a protective intermediary that blocks the propagation of temperature-induced voltage variations from the PGA to the RF front-end, thereby preventing LO leakage without requiring additional power-consuming temperature compensation circuits.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The temperature-dependent properties of the resistors, which initially cause harm through LO leakage, are converted into a beneficial self-compensating mechanism. The source follower's inherent temperature characteristics counterbalance the resistor temperature effects, turning the harmful temperature dependence into a useful compensation mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Adaptability or versatility

If PGA uses active devices like OP-AMP, then gain and dynamic range are ensured, but current consumption increases and area expands

Engineering Contradiction:

Improvegain control rangeVSAvoidcircuit area

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The active OP-AMP-based PGA is replaced with a passive resistor array-based PGA. This substitution eliminates the need for large-area active devices while maintaining gain control functionality through resistive voltage division, significantly reducing the circuit area.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The gain control mechanism changes from active device parameter modulation (OP-AMP gain) to passive parameter selection (resistor ratio selection). By using a multi-stage resistor array with switches, the PGA achieves wide gain/dynamic range (−30 dB to 0 dB) through simple resistive division without requiring power-consuming active amplification stages.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively maintains a constant common mode voltage despite temperature changes, reducing current consumption and physical size, and preventing LO leakage, thereby enhancing the performance and efficiency of RFICs.

Implementation Method 1

a current-voltage conversion amplifier converting a current received at the analog baseband filter into a voltage and adjusting a gain of an output voltage of the current-voltage conversion amplifier using a plurality of resistors

Methodology Applied

Scientific EffectOhm's Law: Ohm's Law

Implementation Method 2

a source follower circuit compensating for temperature for the output voltage of the current-voltage conversion amplifier

Methodology Applied

Scientific EffectTemperature compensation:

Data Source

PatentUS9356563B2Analog baseband filter for radio transceiver

Publication Date: 2016.05.31 SAMSUNG ELECTRONICS CO LTD

AI summary

An analog baseband filter for a radio transceiver is provided. An analog baseband filter for a multi-mode multi-band radio transceiver includes a current-voltage conversion amplifier converting a current received at the analog baseband filter into a voltage and adjusting a gain of an output voltage of the current-voltage conversion amplifier using a plurality of resistors, and a source follower circuit compensating for temperature for the output voltage of the current-voltage conversion amplifier.