"MIT博士PLL论文：频率合成器与锁相环设计"

需积分: 0 186 浏览量更新于2024-04-16 收藏 12.19MB PDF 举报

身份认证购VIP最低享 7 折!

领优惠券(最高得80元）

资源详情

资源推荐

16 LIST OF TABLES

18 CHAPTER 1. INTRODUCTION

1.1 Outline

This thesis is organized as follows:

• Motivation for constant envelope modulation

• Comparison of various constant envelope modulator architectures

• Key system performance requirements for GFSK/GMSK

• Overview of the calibration system

• Implementation Details

• Test Results

• Conclusions

1.2 Choice of Modulation Affects Battery Life

This section will discuss why constant envelope modulation types are attractive for wireless systems.

The type of modulation plays a large role in the efﬁciency of radio frequency (RF) power ampliﬁers.

The power added efﬁciency, η, is a key performance parameter of the power ampliﬁer. As given

by (1.1), η is deﬁned as the ratio of the added RF power to the signal to the power supplied by the

battery [3].

η =

RF ,out

− P

RF ,in

DC ,in

· 100% (1.1)

In many wireless communication devices, the power dissipated by the RF power ampliﬁer is

a sizeable percentage of the total battery power. When a modulated signal with signiﬁcant ampli-

tude variations such as quadrature phase shift keying (QPSK) or quadrature amplitude modulation

(QAM) is applied to an ampliﬁer which exhibits nonlinearities, two important signal degradations

occur. The nonlinear distortion causes distortion to the signal which causes degraded reception by

the intended receiver. The second effect is an increase in spurious transmit energy in adjacent chan-

nels. This effect is known as spectral regrowth and plays a prime roll in determining the required

ampliﬁer linearity. Linearity in power ampliﬁers has been studied extensively [4] and one of the

results is that power added effecienty is sacriﬁced to obtain higher linearity, see for example [5]

and [6]. If the amplitude variations in the modulated signal are reduced, then spectral regrowth is

reduced. This reduction in spectral regrowth may be traded for increased operating output power

and associated power added efﬁciency.

The desire for higher efﬁciency power ampliﬁers and corresponding increase in battery life

has led to the use of modulation types with reduced amplitude variations. Such modulation types

include

differential quadrature phase shift keying (

-DQPSK) used by the IS-54 United States

Digital Cellular (USDC) Standard [7], offset quadrature phase shift keying (OQPSK) used by the

IS-95 CDMA cellular phone system [7], Gaussian frequency shift keying (GFSK) used by the digital

european cordless telephone (DECT) standard [7], and Gaussian minimum shift keying (GMSK)

1.3. CLASSES OF MODULATION 19

used by the European Global System for Mobile Communications (GSM) system [7]. Of these

modulation types, GFSK and GMSK fall in the the continuous phase modulation (CPM) class of

constant envelope modulations [8]. It is this class of modulation that can be generated with the

modulated synthesizer.

1.3 Classes of Modulation

Before focusing on the particular modulation type of interest for this work, it is useful to examine

a few general classes of modulation. Modulation types can be generally classiﬁed as either linear

modulation or nonlinear modulation.

1.3.1 Linear Modulation

The class of modulation schemes known as pulse amplitude modulation (PAM) are called linear

modulation due to the linear relationship between the data symbols and the transmitted signal. When

analyzing narrowband signals that arise in communications systems, it is often times convenient to

represent the signal as in (1.2).

s(t) = <

(t)e

jω

(1.2)

The signal s

(t) is known as the complex envelope of the signal [9] and ω

is the center frequency

of the carrier. For PAM, the complex envelope is given by (1.3) [10].

(t) =

p(t − kT ) (1.3)

The sequence of (possibly complex) data symbols is given by a

and p(t) is the (possibly complex)

impulse response of a linear time-invariant pulse shaping ﬁlter. When the impulse response p(t) is

a smooth function, the envelope of the RF output signal, |s

(t)|, varies with time. Examples of

linear modulation are QPSK and QAM.

1.3.2 Constant Envelope Modulation

Phase and frequency modulation are both nonlinear modulation types because the output signal does

not depend on the modulating signal in a linear fashion. One advantage of this type of modulation

is that the envelope can be made inherently constant. The complex envelope for a constant envelope

signal is given by (1.4) [10].

(t) = e

jψ(t)

(1.4)

The phase function, ψ(t), is commonly generated by ﬁltering the data sequence, a

, with a linear

time-invariant ﬁlter with impulse response, p(t).

ψ(t) =

p(t − kT ) (1.5)

20 CHAPTER 1. INTRODUCTION

1.4 GFSK and GMSK

The class of modulations given by (1.4) and (1.5) include two popular and closely related modula-

tion types which are Gaussian frequency shift keying (GFSK) and Gaussian minimum shift keying

(GMSK) [11]. For GFSK and GMSK, the pulse shaping ﬁlter in (1.5) is given by (1.6),

GMSK

(t) = rect

(t) ∗ g(t) (1.6)

where rect

(t) is a rectangular pulse of duration T , and g(t) is a Gaussian pulse given by (1.7).

g(t) =

√

2πσ

−

(1.7)

The -3 dB bandwidth of the ﬁlter speciﬁed by (1.7) is

−3dB

log(2)

2πσ

(1.8)

and the noise bandwidth is

4σ

√

= f

−3dB

4 log(2)

≈ 1.065f

−3dB

. (1.9)

In addition to using the ﬁlter speciﬁed by (1.6), GMSK and GFSK use a frequency modulation

index of m = 0.5. The standard deﬁnition, see [12] for example, of modulation index for FSK type

modulations is given by (1.10).

∆

= f

dev,p−p

SYM

(1.10)

The symbol period, T

SYM

, is in seconds and the peak to peak frequency deviation, f

dev,p−p

, is in

Hz. Using the deﬁnition of modulation index, we can calculate the change in carrier phase during

one symbol time from (1.11).

∆

= a

2πf

dev,peak

SYM

= a

πm (1.11)

The data symbol, a

, is either 1 or -1. Using a modulation index of m = 0.5 causes the phase of

the RF carrier to either advance or decrease by

radians or 90 degrees relative to a carrier center

frequency phase reference during one symbol time depending on the value of the transmitted bit.

The difference between GMSK and GFSK is that GMSK requires a modulation index of precisely

0.5 while GFSK can work with different modulation indices. However, a nominal modulation index

of 0.5 is common for GFSK systems.

GMSK/GFSK is further classiﬁed by the product of the Gaussian ﬁlter -3 dB bandwidth, B,

and the symbol time, T . Values of BT ranging from 0.2 to 0.5 are common in practice. The

DECT standard employs GFSK with BT = 0.5 [13] and the GSM standard employs GMSK with

BT = 0.3 [7]. The parameter σ is related to the symbol rate and the parameter BT by

σ =

log(2)

2πf

SYM

. (1.12)

剩余178页未读，继续阅读

kk228

粉丝: 2
资源: 21

"MIT博士PLL论文：频率合成器与锁相环设计"

基于PLL信号发生器的设计资料.zip电子设计项目毕业设计及产品设计资料论文,源代码及PCB资料

关于PLL学习资料，大神写的，值得一看

MIT的博士毕业论文，关于PLL学习资料，大神写的，值得一看 频率合成器，锁相环、集成电路设计、环路分析、噪声分析

锁相环pll电路设计与应用 pdf csdn

锁相环pll电路设计与应用

小数 n 分频锁相环 (pll) 合成器

为什么PLL锁相环可以实现频率合成

DDS+PLL高性能频率合成器

锁相环[pll]电路设计与应用 pdf

硬件PLL锁相环时钟恢复电路

multisim锁相环pll

pll锁相环工作原理

pll锁相环ip核使用

pll 锁相环 仿真 c代码实现

pll锁相环工作原理csdn

pll原理讲义 一个典型的锁相环(pll)系统

pll软件锁相环代码

pll锁相环 csdn

三相并网逆变加pll锁相环simulink仿真

软件实现锁相环pll

最新资源

MIT的博士毕业论文，关于PLL学习资料，大神写的，值得一看频率合成器，锁相环、集成电路设计、环路分析、噪声分析

pll 锁相环仿真 c代码实现

pll原理讲义一个典型的锁相环(pll)系统