There are four chapters in my dissertation. Chapter one gives a brief introduction of the three essays. Chapter two empirically analyzes the interaction among conventional monetary policy, foreign exchange intervention and the exchange rate in a unifying model for Japan. I have several findings. First, the results lend support to the leaning-against-the-wind hypothesis. Second, conventional monetary policy has as great influence on the exchange rate as foreign exchange intervention in Japan. Third, intervention in Japan is ineffective or may be counter-effective, so escaping liquidity trap by intervention alone may not be a feasible way. Chapter three empirically identifies the sources of exchange rate movements of Japan vis--vis the US, an...