前馈技术在改善功率放大器线性中的应用

推导并分析了存在增益和相位跟踪等误差情况下,功率放大器前馈技术对三阶线性失真的改善情况,并从原理上论述了前馈技术的工作原理.前馈技术一般可将三阶互调降低10～30 dB,在新一代的抗干扰跳/扩频电台中有广泛应用.     

Practice makes perfect: Entrepreneurial-experience curves and venture performance

This study tackles the puzzle of why increasing entrepreneurial experience does not always lead to improved financial performance of new ventures. We propose an alternate framework demonstrating how experience translates into expertise by arguing that the positive experience–performance relationship only appears to expert entrepreneurs, while novice entrepreneurs may actually perform increasingly worse because of their inability to generalize their experiential knowledge accurately into new ventures. These negative performance implications can be alleviated if the level of contextual similarity between prior and current ventures is high. Using matched employee–employer data of an entire population of Swedish founder-managers between 1990 and 2007, we find a non-linear relationship between entrepreneurial experience and financial performance consistent with our framework. Moreover, the level of industry, geographic, and temporal similarities between prior and current ventures positively moderates this relationship. Our work provides both theoretical and practical implications for entrepreneurial experience—people can learn entrepreneurship and pursue it with greater success as long as they have multiple opportunities to gain experience, overcome barriers to learning, and build an entrepreneurial-experience curve.     

异质性、外资企业生产率与产业集聚

本文采用2000~2007年工业企业数据,系统考察了外资企业与我国地区产业集聚之间的互动促进关系,并从企业规模、控制权性质两个维度分析不同外资企业与产业集聚之间互动关系的路径差异。结果发现:外资企业与地区产业集聚之间的互动促进关系主要是外资企业与其前后关联行业集聚之间的互动促进,外资企业与同行业的集聚并未形成相互依赖、相互促进的关系;外商独资企业与其前后向关联行业的集聚均存在互动促进,且外商独资与其后向关联行业的集聚之间形成的互动促进是外资企业与我国产业集聚互动促进的主要路径;中外合资企业仅与其前向关联行业集聚之间形成稳定的互动促进关系。     

央行前瞻性指引与提升政策透明度

金融危机中,许多发达国家央行致力于提升政策透明度,在货币政策目标分析和政策对外沟通方面取得了进步。文章介绍了前瞻性指引的概念,分析了美国、日本、英国和欧洲央行实施新一轮前瞻性指引的内容及其引发的讨论,并简析了未来前瞻性指引的运用空间。     

Estimating Cointegrated Panels with Common Factors and the Forward Rate Unbiasedness Hypothesis

This article proposes a bias-adjusted estimator for use in cointegratedpanel regressions when the errors are cross-sectionally correlatedthrough an unknown common factor structure. The asymptotic distributionof the new estimator is derived and is examined in small samplesusing Monte Carlo simulations. For the estimation of the numberof factors, several information-based criteria are considered.The simulation results suggest that the new estimator performswell in comparison to existing ones. In our empirical application,we provide new evidence suggesting that the forward rate unbiasednesshypothesis cannot be rejected.     

Cointegration and causality among the onshore and offshore markets for China's currency

China has taken steps to develop offshore markets for renminbi trading and to liberalize exchange-rate determination in its onshore market. We examine the interaction between onshore and offshore markets with attention to how the interaction has been affected by widening of the onshore trading band first in April 2012 and further in March 2014. Ties between the onshore and offshore markets were closest before the first band widening and steadily loosened thereafter. We further study the cointegration and lead-lag effects between offshore and onshore spot and forward markets and show that there is a long-term equilibrium relationship between any pair of them. Our results suggest stronger causality running from the spot onshore rate to the spot offshore rate than vice versa. Between the spot and forward markets, there is evidence of bidirectional linear and nonlinear causality, which implies foreign impulses have had an influence on the domestic market.     

SERIES EXPANSION OF THE SABR JOINT DENSITY

Under the SABR stochastic volatility model, pricing and hedging contracts that are sensitive to forward smile risk (e.g., forward starting options, barrier options) require the joint transition density. In this paper, we address this problem by providing closed‐form representations, asymptotically, of the joint transition density. Specifically, we construct an expansion of the joint density through a hierarchy of parabolic equations after applying total volatility‐of‐volatility scaling and a near‐Gaussian coordinate transformation. We then establish an existence result to characterize the truncation error and provide explicit joint density formulas for the first three orders. Our approach inherits the same spirit of a small total volatility‐of‐volatility assumption as in the original SABR analysis. Our results for the joint transition density serve as a basis for managing forward smile risk. Through numerical experiments, we illustrate the accuracy of our expansion in terms of joint density, marginal density, probability mass, and implied volatilities for European call options.     

A framework to measure integrated risk

A framework underlying various models that measure the credit risk of a portfolio is extended in this paper to allow the integration of credit risk with a range of market risks using Monte Carlo simulation. A structural model is proposed that allows interest rates to be stochastic and provides closed-form expressions for the market value of a firm's equity and its probability of default. This model is embedded within the integrated framework and the general approach illustrated by measuring the risk of a foreign exchange forward when there is a significant probability of default by the counterparty. For this example moving from a market risk calculation to an integrated risk calculation reduces the expected future value of the instrument by an amount that could not be calculated using the common pre-settlement exposure technique for estimating the credit risk of a derivative.     

Term structure modelling of defaultable bonds

In this paper we present a model of the development of the term structure of defaultable interest rates that is based on a multiple-defaults model. Instead of modelling a cash payoff in default we assume that defaulted debt is restructured and continues to be traded.The term structure of defaultable bond prices is represented in terms of defaultable forward rates similar to the Heath-Jarrow-Morton (HJM) (Heath et al., 1992) approach, and conditions are given under which the dynamics of these rates are arbitrage-free. These conditions are a drift restriction that is closely related to the HJM drift restriction for risk-free bonds, and the restriction that the defaultable short rate must always be not below the risk-free short rate. In its most general version the model is set in a marked point process framework, to allow for jumps in the defaultable rates at times of default.Financial Assistance by Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 303, at the University of Bonn and the DAAD is gratefully acknowledged.I thank Pierre Mella-Barral, David Lando and David Webb for helpful conversations, and the participants of the FMG Conference on Defaultable Bonds (March 1997) in London and the QMF 97 conference in Cairns for helpful comments. All errors are of course my own.     

Cross‐sectional Restrictions on the Spot and Forward Term Structures of Interest Rates and Panel Unit Root Tests

In this paper we examine the stationarity of all the rates comprising the USD, GBP, DM and JPY spot and forward term structures. Instead of focussing on short maturity interest rates, as most other papers do, we perform a detailed analysis of the whole range of spot and forward interest rates of the 4 main currencies. We investigate the issue of stationarity within the framework of an equilibrium interest rate model such as Vasicek (1977), that defines the cross-sectional and time series properties that interest rates of various maturities must satisfy. We show that within a one-factor interest rate model, such as Vasicek, all interest rates are restricted to exhibit the same mean reverting behaviour. This restriction allows us to apply more powerful panel unit root tests. This methodology increases considerably the number of observations available and as a result the power of the unit root tests. The higher power of these tests allows us to demonstrate that there does exist mean reversion on the spot and forward US interest rates and the forward DM and GBP interest rates.